Main characteristics of cellular communication of the CDMA standard. Description of the CDMA standard

S. Orlov

CDMA Technology - Features and Benefits

In the choice of cellular telephony technology at the turn of the third millennium, certainty seems to have appeared. By the end of 1999, according to CDG (CDMA development group), CDMA (Code Division Multiple Access) technology was chosen by 50 million subscribers in the world (Fig. 1). Including 28 million in Asia, 16.5 million in North America and 5 million in Latin America. There are half a million subscribers in Europe, the Middle East and Africa.

Rice. 1. Growth in the number of CDMA subscribers in the world

Such a rapid development of code division access technology is explained by the expected increase in subscriber density, resistance to interference, a high degree of protection of transmitted data from unauthorized access, and better energy and economic indicators. Simplified modeling shows that the capacity of base stations with CDMA technology is several times larger compared to existing cellular telephony standards that use frequency division channels (NMT, AMPS, TACS). Reality is, of course, much more complex than idealized models.

Briefly, the advantages of CDMA over other systems are as follows:

• the capacity of base stations increases 8-10 times compared to AMPS and 4-5 times - compared to GSM;
• improved sound quality compared to AMPS;
• lack of frequency planning due to the use of the same frequencies in the adjacent sectors of each cell;
• improved security of transmitted data;
• improved coverage characteristics, allowing the use of fewer cells;
• longer battery life before discharging;
• the possibility of allocating the required frequency band - as needed.

Technical features of CDMA technology

To compare the capabilities of CDMA technology, it is necessary to provide a description of existing standards.

Advanced Mobile Phone Service (AMPS). This standard provides for frequency division of subscriber access to the base station (FDMA - frequency division multiple access). Each channel is allocated a narrow bandwidth (30 kHz) and this channel is assigned to one subscriber. There is also narrowband AMPS (NAMPS), in this standard only 10 kHz is allocated per channel. In the TACS (Total Access Communications System) system, the bandwidth allocated for one channel is 25 kHz.

In North America, one operator owns an average of 416 AMPS channels and occupies the 30 kHz × 416 » 12.5 MHz band. Obviously, the same frequencies cannot be used in adjacent cells, so the seven cells that make up the daisy use the same frequency plan. Thus, for AMPS, the number of subscribers per cell is approximately 416/7 = 59. In fig. 2, the reuse of the same frequencies is shown in the same shades.

Rice. 2. "Chamomile" frequency plan AMPS

It should be noted that the frequency reuse factor K = 7 was chosen rather from practical field measurements than from the law of attenuation of radio waves in vacuum on the free surface, and takes into account the real environment: houses, relief, etc. On the free surface, this coefficient would be somewhat larger.

In Europe, technologies with time division of channels are widely used. GSM (IS-54) uses 10 frequency channels and 8 time slots occupying a 200 kHz wide frequency trunk. Thus, in the GSM system in the same frequency band of 12.5 MHz, 12.5 / 0.2 = 62 trunks of 200 kHz each can be placed. Considering that each frequency channel is divided into 8 time slots, the cell capacity is 80 subscribers, against 59 in AMPS.

Code division technology offers further ways to increase the capacity of base stations. The key point is the use of noise-like signals. Instead of splitting the spectrum or time slots, each user is assigned a fragment of a noise-like carrier. Since its fragments are quasi-orthogonal, it becomes possible to allocate the entire width of the dedicated channel for each user. By solving the near-far zone problem and dynamic power control, the frequency distribution is as shown in Fig. 3, that is, the entire 1.25 MHz frequency band is used by each user and is reused in the adjacent cell. The capacity per cell is determined by the balance between the required signal-to-noise ratio for each user and the compression factor of the code sequence.

Rice. 3. CDMA frequency plan

A quantitative indicator of the quality of a digital receiver is a dimensionless signal-to-noise ratio (SNR - Signal Noise Ratio)

The noise power spectral density in the expression means the latter for thermal noise, and interference is the mutual influence from other subscribers. The value of the signal-to-noise ratio determines the ratio of the number of erroneously transmitted bits to their total number. This ratio also depends on other additional factors such as channel coding and error correction, multipath and fading. For receivers typically used in commercial CDMA, the signal-to-noise ratio should be between 3 and 9 dB. The energy per bit and the data rate are related as follows:

where P s is the signal power.

Noise plus interference is the power spectral density. If the signal spectrum has a uniform distribution with bandwidth W, then the noise plus the interference component of the power spectral density is:

where the first term is the thermal noise level of the receiver (FN = receiver noise factor). Rewriting the expression for the signal-to-noise ratio in terms of data rate and occupied spectrum width, we obtain a formula that relates the ratio of energy per bit to the noise power with the power per user, as well as the data rate, the total power to other users, and the width of the occupied spectrum:

This formula explains that code division systems provide the greatest advantage in networks with high subscriber density and high traffic.

The problem of the near-far zone

CDMA technology (and other spread spectrum systems) has been neglected in mobile wireless communication systems for many years due to the so-called near-far problem. Since the result of the receiver's operation in such systems is the convolution of the received and reference signals, there was an ambiguity in the identification of the convolution signal. So, for example, the side lobes of the convolution signal from a nearby mobile terminal may be comparable in amplitude to the main response of the convolution signal from the most distant terminal. Therefore, the other most important point in CDMA technology is that all mobile terminals must create approximately the same field strength near the base station antenna.

Power management

The key point of commercial CDMA is extremely simple: if you use power management so that the received power from all remote sites is equivalent, then all the benefits of spreading the spectrum become realizable. Assuming that power is controlled, noise and interference can be expressed as:

N 0 + I 0 \u003d N 0 + (N - 1) P,
N 0 = F N k B T O , (5)

where N is the total number of users. The signal-to-noise ratio takes the form:

The maximum number of subscribers per base is reached if the power is added just enough to provide the required signal-to-noise ratio, in exact accordance with the accepted value of the error probability. If we set the value of the left side of the expression (6) equal to the given signal-to-noise ratio and solve this expression with respect to N, then we get the ratio for determining the capacity of the base station for CDMA:

Given that the data rate in CDMA is 9.6 kbaud, we get:

Or, given that 15.1 dB is 5.688, and squaring, the number of users per base station at a signal-to-noise ratio = 6 dB is 32. When power control is included in the system, the system designer or the operator has the ability to choose a compromise between signal-to-noise ratio and the maximum number of simultaneous calls. We note again that the signal-to-noise ratio and the number of subscribers are interrelated: if the signal-to-noise ratio is increased by 3 dB, then the allowable number of subscribers will be halved, that is, to 16. In expression (8), we neglected the difference between N and N–1 . There are some other factors that we have not taken into account.

Cell capacity

The discussion around expression (8) assumed only one cell, not taking into account interference with neighboring ones. One might ask, what are we gaining? The capacity of an isolated AMPS cell is even greater. In fact, nothing prevents the use of all frequency trunks (1.25 MHz each) within one cell (compare Fig. 2 and Fig. 3). Thus, if we make an approximate comparison, then for AMPS the capacity of a “daisy” of seven cells is equal to the product of the number of subscribers per cell (59) by 7, that is, 413. The similar capacity for CDMA is equal to the product of the number of subscribers per cell (32) to the number frequency trunks (10) and the number of cells (7), i.e. 2240. The CDMA to AMPS capacity ratio is 5.4. However, if interference with neighboring cells is taken into account in expression (3), then this ratio will decrease to 4.4. In addition to the possibility of using all ten frequency trunks simultaneously, CDMA uses cell sectorization. This improvement increases the relative capacity ratio of CDMA and AMPS by up to 13 times.

Speech encoding

An important point for reducing the mutual interference of channels from different subscribers is speech coding. Coding can significantly reduce the average transmitter power.

It is known that human speech is an intermittent signal source. According to Bell Laboratories measurements, speech activity accounts for 35–40% of the total time resource. If you use this factor, then you can increase the capacity of the network by a factor of two or more. In practice, this activity factor is 50% due to the fact that mobiles and base stations must maintain a physical link during the silent period and the power cannot be reduced to zero. Thus, the advantage of CDMA over AMPS can be up to 26 times.

Features of building a CDMA network

One of the founders of CDMA technology is the American company QUALCOMM. In the US, the CDMA digital cellular system has been standardized by the TIA (Telecom-munication Industry Association) and described in the IS-95 standard. Like IS-54, IS-95 provides for compatibility with existing AMPS cellular telephony systems. IS-95 systems are allocated the same bandwidth as AMPS. In other words, CDMA works "on top" of the existing AMPS.

The CDMA system allows each user within a cell to use the same radio channel and the entire allocated frequency band. A user in an adjacent cell is using the same frequency band. The system absolutely does not need frequency planning. To reduce costs for mobile operators and facilitate the transition from AMPS to CDMA, the CDMA system provides a channel width of 1.25 MHz, the same as that of AMPS. Unlike other cellular systems, single channel traffic is not constant and depends on voice activity and network requirements.

IS-95 uses different types of modulation for the forward and reverse channels. In the forward link, the base station transmits data simultaneously for all users in the cell, using a different spreading code for each user to separate the channels. The pilot code is also transmitted and has a higher power level, allowing users to synchronize frequencies. In the reverse direction, the mobile handsets respond asynchronously, with the same power level coming to the base station from each mobile. This mode is possible due to power control and power control of moving tubes via the service channel. IS-95 uses Excited Linear Predictive (QCELP) speech coding. It is encoded and compressed, and the data rate per channel is 9.6 kbaud. The speech codec detects voice activity and in pauses (during silence) reduces the channel speed to 1200 baud. Intermediate values ​​2400, 4800 are also possible.

Specification of frequencies and channels

For the return link, IS-95 defines a frequency band from 824 to 849 MHz. For the direct channel - 869-894 MHz. The forward and reverse channels are separated by an interval of 45 MHz. User data is packed in a channel with a bandwidth of 1.2288 Mbps. The channel load capacity is 128 telephone connections with a traffic rate of 9.6 kbaud. The spectrum spreading algorithm for the forward and reverse channels is different. In the forward channel, the user data stream is encoded and compressed by a factor of 2. Next, the bit permutation algorithm is used (in the domestic literature there is a term - interleaving). After that, the data is convolved with one of the 64-bit pseudo-random sequences of PRS (Walsh functions). Each mobile subscriber is assigned a PSP fragment, with the help of which his data will be separated from the data of other subscribers. The orthogonality of the PRP fragments is ensured by synchronous coding of all channels in the cell simultaneously (and the fragments themselves are orthogonal). A pilot signal (code) is provided in the system so that the mobile terminal can control the channel characteristics and perform synchronous detection. For global synchronization of the CDMA network, the system also uses radio tags from GPS satellites. In the reverse channel, a different spectrum shaping algorithm is used, since the signals from remote terminals reach the base station along different paths. After precoding and 1/3 compression and bit swapping, blocks of 6 encoded symbols are packed into one of 64 orthogonal Walsh functions. Thus, a 64-digit signal is formed. Quadruple spread spectrum at the output creates a stream of 1.2288 Mbps. The 307.2 kbps source sequence is generated according to codes defined for user 242 and base station 215. 1/3 compression and Walsh packing results in exceptional interference immunity. Improved error robustness is essential for the reverse link as it uses non-coherent detection and has interference with other mobile terminals within the cell. Another important element of the reverse channel is mobile terminal power control. The system provides slow (static) power control and fast. Quick control commands are sent at 800 baud and are embedded in conversational frames. Without fast power control, the fading associated with the propagation of radio waves in structures with reflective objects (walls of houses, metal structures, and so on) would lead to a significant degradation in system performance. Slow power control provides equivalent equalization of distances from mobile terminals to the base station. To combat multipath, both the mobile terminal and the base station use a RAKE receiver using correlation signal reception. Several correlators are used at the receiver input, which fold the input sequence. In this case, the reference signal is applied to different correlators with a slight time shift comparable to the time difference when radio waves travel along different trajectories. The output signals of the correlators are summed. Thus, if the level of the convolution signal from one of the multipath signals at the current moment of time turns out to be equal to zero (as a result of the interference pattern of the field distribution), then the convolution from the delayed signal will be different from zero. The IS-95 standard provides for three correlators at the receiver input. The CDMA architecture provides for a soft handover. Communication during the transition of the mobile terminal from one cell to another is not destroyed and is not interrupted. The mobile terminal combines two signals from two base stations in the same way as it combines two signals from the same base station coming from different paths.

Direct CDMA channel

The forward CDMA channel consists of a pilot, a sync channel, up to seven paging channels, and up to 63 traffic channels. The pilot signal enables the mobile terminal to receive timestamps, providing phase lock for coherent detection. Based on the pilot signal, mobile terminals are able to determine the relative signal strengths from each base station and decide when and to which base station to locate. The synchronization channel transmits clock signals to mobile terminals at 1200 baud. Paging channels are used to transmit control information and other messages and operate at 9600, 4800, 2400 baud. The forward traffic channel transmits any user data at 9600, 4800, 2400, 1200 baud.

The data on the forward traffic channel is grouped into a 20 ms frame. User data after precoding and formatting is interleaved to adjust the current data rate, which may vary. Then the spectrum of the signal is expanded by convolution with the Walsh function and a pseudo-random sequence to a value of 1.2288 Mbps.

Power control subchannel

To minimize errors, IS-95 provides for control of the power output of each tube. The base station on the reverse channel receives and evaluates the field strength from each handset and informs the mobile terminal about the need to reduce / increase the power.

Since the power received by the base station is determined by both the distance to the mobile and the interference in the communication channel (and zeros and antinodes are located at a close distance in the interference pattern), the base station sends power control signals every 1.25 ms. The power control signal is sent to the mobile terminal on the forward control subchannel. This signal is instructed to increase or decrease the power by 1 dB. If the signal level is low, then “0” is transmitted in the direct control subchannel, thereby instructing to increase the power, and vice versa. Power control bits are inserted after the scrambled data.

There are 24 data symbols transmitted in a 1.25 ms interval, and IS-95 allows 16 possible positions for transmitting a power control bit. These positions are at the beginning and any of the first 16 bits can be a power control bit. The 24 bits for the long code decimator are used to scramble the data in a 1.25 ms interval. And the last 4 bits out of 24 determine the position of the power control bit.

Reverse CDMA channel

User data in the reverse channel is grouped into frames with a duration of 20 ms. All data in the reverse channel is encoded with a convolutional codec, interleaved and encoded with a 64-character orthogonal sequence. Spectrum spreading occurs before transmission. The procedures for interleaving, orthogonal modulation, spreading the spectrum are similar to those for the direct channel, so their description is omitted.

Conclusion

Direct spread spectrum systems, or they say, noise-like signals, were not invented today or even yesterday. Such communication systems have long been used in military and special equipment. And the fact that today this technique is gradually moving into the category of public production is largely due to the huge successes in microelectronics: digital and analog, passive information processing devices. A number of important and useful developments were made by Russian scientists: the Voronezh Research Institute of Radio Communications, the Moscow Research Institute of Radio Communications, NPO Almaz, and others. To decorate the material, it is worth citing the results of developments that have commercial application in CDMA.

On fig. Figure 4 shows the frequency response of an IS-95 surface-acoustic wave filter designed for a mobile terminal, and fig. 5 - frequency response of the filter for Wideband CDMA - a communication technology that allows you to transmit, including a moving image.

Literature

1. Vijay K. Gard. IS-95 CDMA and cdma2000: Cellular/PCS systems implementation. 446 p.
2. Kyung Il Kim. Handbook of CDMA system design, engineering and optimization. 274p.
3. Joseph C. Liberti, Jr., Theodore S. Rappaport. Smart Antennas for wireless communication IS-95 and third generation CDMA application.
4. Poor/Wornel. Wireless Communication: Signal Processing perspectives. 432 p.
5. Theodore S. Rappaport. Wireless Communication: Principles and Practices. 656p.
6. Gard/Smolik/Wilkes. Application of CDMA in Wireless/Personal Communication. 416 p.
7. Man Young Rhee. CDMA Cellular Mobile Communication and Network security. 544 p.

It cannot be said that the comparison of GSM and CDMA networks is relevant for Russia today: the GSM standard has conquered the market long and firmly, and is not going to be crowded yet. However, a number of advantages of CDMA, which is no longer new, but developing, makes one think about the choice in a number of cases: for example, when a high data transfer rate or voice quality is fundamentally important. An ordinary consumer is faced with a dilemma when he accidentally notices the tariff scale of a few CDMA operators or reads in the characteristics of a phone he likes that the latter supports this particular communication standard. What will we get by changing the usual GSM-smartphone to CDMA? Let's evaluate the advantages and disadvantages of both networks from the point of view of the payer to the operator's cash desk.

Definition

Cellular standard CDMA uses a single wide code division bandwidth. In general, the scheme of operation can be represented as follows: several subscribers transmit a data packet simultaneously at the same frequency, the data packet from each is encoded in a unique way.

GSM cellular standard uses the principle of frequency-time division of the channel. General view of the operation scheme: each subscriber uses his (to which he connected) time slot and a narrow frequency band to transmit a data packet.

Comparison

What is the difference between GSM and CDMA, if the definitions give out practically a set of words? Narrow bands, wide bands, frequencies… And in what form to the end user? First of all, the differences for us, calling and accessing the Internet, are in the quality of communication. Just a wide band provides data transmission with virtually no quality loss. If you used a wired landline telephone, you will immediately feel the difference between GSM and CDMA: the latter gives approximately the same sound without interference and interruptions.

The data transfer rate in CDMA networks is quite high, up to 2 Mbps. However, many will be surprised to learn that they are well acquainted with CDMA. The well-known 3G technology, or UMTS, is just one of the varieties of CDMA. We use it to transfer data through our regular smartphones, tablets and other devices. However, voice calls and sending SMS messages (as well as other operator services) are in the GSM network.

There are few CDMA operators in Russia, their coverage area includes few territories, so it is premature to talk about the transition to this communication standard. However, where, for example, Skylink works, the clients of this operator note the reliability of the connection in the first place. An undoubted advantage can be considered the increased security of data transmission due to complex signal encryption systems. The main thing is that it is much more difficult to intercept information in CDMA networks than in the usual GSM.

The GSM network is widespread in Russia almost everywhere and leaves almost no “white spots”. Smartphones and phones designed to work on CDMA networks make up a negligible number of them, so choosing the right model for yourself is not easy. In CDMA devices, an R-UIM card is installed, which allows you to change the operator and number.

The difference between GSM and CDMA can be significant for those who care about health. Experts believe that the negative impact on the human body of radiation from CDMA modules is several times lower than from GSM modules. This is due to the low power of the emitter: 0.2 W versus 2 W, respectively.

Findings site

1. CDMA mobile networks provide higher voice quality and secure connections.
2. CDMA networks provide high data rates.
3. The coverage of GSM networks in Russia is wider today.
4. The choice of devices operating in GSM networks is ten times more than CDMA devices.
5. When connected to a CDMA device, a short (direct) number is assigned.

CDMA - Code Division Multiple Access - code division multiple access system.

CDMA or cdmaOne is an all-digital standard using the 824-849 MHz frequency range for receive and 874-899 MHz for transmission.

CDMA is called a wideband system and the signals are transmitted over the air noise-like. Broadband - because it occupies a wide frequency band. Noise-like signals - because when several subscribers work on the air at the same frequency, at the same time, the signals overlap.

CDMA technology has been known for a long time. After World War II, CDMA technology was used for a long time in military communication systems, both in the USSR and in the USA.

1935 - in the USSR, the first work devoted to this topic was published by Doctor of Technical Sciences, Professor, Honored Worker of Science and Technology of the RSFSD.V. Ageev.

In the 50s, it was used by the American military communications system, which was used to organize the exchange of voice messages between military aircraft and ground services, as well as to determine the distance to the aircraft.

In 1983, Motorola's first portable cell phone was released. Weight 1.15 kg, Cost 4 thousand dollars.

In November 1989 in San Diego, the capabilities of a digital cellular communication system based on code division of channels were demonstrated for the first time by the American company "Qualcomm"

In 1995, the launch of the first CDMA (is-95) cellular network in Hong Kong, the network is built on Motorola equipment.

Historically, the CDMA standard is most common in North and South America, Southeast Asia:

The evolution of cellular communication systems using CDMA technology.

Table of development of CDMA2000 technology

multisession network games, etc.

Comparison of CDMA and TDMA (GSM) technologies. TDMA- Time Division Multiple Access -

multiple access system with

channel time division.

Access to the base station of several subscribers on the same frequency with time division.

This technology is based on the GSM standard,

From the figure, we see that several subscribers communicate with the "base" on the same frequency channel, but in turn, at equal, very, very short, intervals of time, i.e.

several subscribers can talk on the same frequency, but at different times. At any given time, only one conversation, or rather a small part of it, is transmitted on the carrier. In the next time slice, the system will transmit part of another conversation, and so on. On the receiving side, the conversations are again assembled from parts into a single whole. The described parts of the conversation are so small that for end users, breaking the conversation into such parts is almost imperceptible.

CDMA - Code Division Multiple Access

With code division of channels.

Access to the base station of several subscribers on the same frequency

With code division

When using CDMA technology, all conversations are transmitted on a carrier at the same time. To understand the organization of the CDMA signal on the air, consider an example invented by marketers from Motorola.

It is necessary to imagine the "carrier" in the form of a room, with two opposite walls of which there are pairs of people (one person from a pair at each wall), speaking only their native language, and each pair speaks a language different from the languages ​​of the other pairs. At the same time, all couples speak at the same time and with the same volume, but they do not interfere with each other at all, because for one couple the sounds uttered by the neighboring couple are nothing more than meaningless noise. However, everything that is pronounced by one of the members of the couple is completely understandable against the general background for the second member of the couple, due to the use of a common language understandable to both. Returning to real concepts, it should be noted that the room

- this is the carrier, pairs of people near the walls - this, respectively, is the terminal and part of the base station serving this terminal, and the unique language is the code that encodes this talk.

What does it affect

First of all, on the health of someone who talks a lot on the phone

On how fast the network works, the speed of transmitting / receiving data

Differences between CDMA and other digital technologies

High communication quality Eco-friendliness - safety for human health High data transfer rate Confidentiality Noise immunity Cost-effectiveness

Higher quality of communication.

In CDMA technology, it is possible to provide high quality speech while reducing the radiated power and noise level. The result is consistently high voice and data quality with minimal average output power.

Environmental friendliness - safety for human health.

A distinctive quality of CDMA technology is the lower power consumption of the terminals - several times lower output power, which reduces the impact of electromagnetic radiation on the human body by 1.5 - 2 times.

CDMA mobile terminals can maintain a quality connection with Base Stations at minimum power. In the worst case, this power reaches 0.2 watts (this is the peak value of some older phones with an unstable connection), usually in the milliwatts, while in other standards it ranges from 0.6 to 2 watts.

In addition, the closer the terminal is to the Base Station, the lower the level of electromagnetic radiation it has.

Due to the low intensity signal, the total electromagnetic emission level is much lower than in other standards.

Phones operate using a power-at-noise signal. This ensures high environmental friendliness and safety for the user.

Oddly enough, this consumer quality is a consequence of the military application of the standard. Following military logic, if it is impossible to find out from the negotiations the final goal of the pilot of the aircraft, there is nothing left but to destroy this aircraft. That's it for the difficulty of detecting an aircraft as a signal source, the radiated power of the terminal is significantly reduced.

Higher data transfer rate

CDMA technology implements original, more optimal algorithms for using the channel resource, which provides more opportunities for using CDMA terminals in terms of data transmission.

Provides less delay in the transmission of a voice message than other mobile communication systems.

When using CDMA, you do not have to use sophisticated means to suppress the echo signal. A perfect method of error correction allows you to effectively deal with multipath signal propagation.

This property provides additional benefits of CDMA in high-rise urban environments.

Confidentiality.

The built-in coding algorithm and distribution of information over a wide range provides protection against unauthorized access and listening.

CDMA is the most secure standard available on the cellular market.

Initially, the standard was developed and implemented to connect pilots with ground services. It was important to "hide" the signal among the noise in order to make it difficult for the enemy to detect such a signal. Even if it was possible to isolate significant signals from the noise, the next problem appeared - decoding conversations. Conversations are encrypted using unique codes that require exceptional computing power to decipher.

CDMA is based on a modulation method using a noise-like and wideband signal (sometimes they say “blurred” or “stretched” spectrum). Useful information is, as it were, “smeared” over a frequency range that is much wider than with traditional methods of signal modulation (such a signal is often called narrowband). The result is a signal that occupies a larger

frequency range and has a much lower intensity than with narrowband modulation. It is clear that in this case it is possible to receive information only by knowing the sequence by which the useful signal was multiplied during transmission - otherwise it will look like noise (hence the name). Therefore, in military applications, this method was used primarily for protection against interference (broadband signal is very resistant to narrowband interference) and listening.

Noise immunity.

Noise-immune - because if a signal-interference occurs in a wide frequency band (1.23 MHz), a narrow range (200 kHz), the signal will be received almost undistorted. Due to error-correcting coding, the system will restore the lost data.

Interference of industrial origin, such as cars, is not terrible, since their spectrum is much narrower and unable to block the CDMA signal.

The "code" used in CDMA serves not only to identify the conversation, but is also a kind of filter that eliminates distortion and background noise.

In terms of voice quality characteristics (naturalness and intelligibility), CDMA parameters are comparable to the quality of wired channels.

Noise immunity is valuable, since not only voice, but also any other information is transmitted through CDMA channels.

If the average user, by and large, is indifferent to whether his voice sounds in a telephone conversation with impeccable clarity or with little interference, then errors made during file transfers can violate the integrity of, for example, a corporate database.

Large network capacity.

More complete use of the frequency resource - the capacity of CDMA is 10 to 20 times higher than that of analog systems (FDMA), and 3 to 6 times the capacity of other digital systems (TDMA).

CDMA networks use the radio frequency resource efficiently due to the ability to reuse the same frequencies in the network.

In systems with frequency division channels (both FDMA and TDMA) there is a problem of the so-called "reuse" (reuse) frequency channels.

In order not to interfere with each other, neighboring base stations (BS) must use different channels. Thus, if a BS has 6 neighbors (the most frequently considered case, while the area of ​​\u200b\u200beach BS can be represented as a hexagon, and everything together looks like a honeycomb), then the number of channels that this BS can use is seven times less than the total number of channels in the range allocated for the network. This leads to a decrease in network capacity and the need to increase the density of BS installation in densely populated areas.

For CDMA, there is no such problem at all. All BSs operate on the same channel. Thus, the frequency resource is used more fully.

One subscriber is "leaded" by several base stations.

One of the features of CDMA networks is the possibility of "soft" transition from one base station to another (soft handoff). At the same time, a situation is possible when several BSs "lead" one subscriber at once. The subscriber simply will not notice that he was "transferred" to another BS. Thus, communication interruptions during movement are excluded. In addition, while maintaining communication with several base stations (up to 4x) at the same time, the best signal is selected. Moreover, if no channel provides the proper quality, then the signal is built from "bad" components, which in total gives a good result. If a subscriber, guided by three base stations, enters the coverage area of ​​the 4th base station, it acts as interference. The network optimization department is called upon to monitor the absence of such overlays. A typical example of this advantage in action: in an underpass where GSM phones can lose connection, a CDMA phone, catching multiple echoes coming from different directions, can confidently keep in touch.

economy

The number of base stations required to form high-quality coverage is much lower than that of other standards, which in turn affects the capital and operating costs of operators. And the level of costs invariably determines the level of tariffs that an operator can afford in a particular struggle in the communications market.

CHAPTER 3. STRUCTURE OF INTERTELECOM LLC COMPANY

CEO heads Intertelecom LLC and carries out general management of its activities in accordance with the provisions of the charter of Intertelecom LLC.

Reporting directly to the CEO are:

- ;

- Deputy General Director for Construction;

- Head of the technical operation department;

- Head of Network Planning and Development Department;

- Head of Information Technology Department;

- Technical directors of regional branches.

Directly subordinate to the First Deputy General Director are:

- Chief Accountant;

- Head of the Department of Economics and Finance;

- Head of Marketing and Sales Department;

- Head of Customer Service Department;

- Head of Human Resources Department;

- Head of the General Department (Chief of the Office);

- Director of security;

- Head of the legal department;

- Head of the motor transport department;

- Head of Procurement Department;

- Head of the economic department.

The First Deputy General Director coordinates the administrative and economic activities of the Deputy General Director for Economics and Finance, the Department of Technical Operation, regional offices, the Department of Planning and Network Development.

Head of Marketing and Sales Department directly subordinate to the chief managers of the regions.

Head of Customer Service Department manages the work of customer service centers of regional branches and the information support center.

Head of technical operation department supervises the directors of the technical directorate of the region.

AGREED

First Deputy General Director

Shulga L.V.

Deputy General Director for Construction

Labor protection department

Network Planning and Development Department

NOTATION

Subordination

Coordination

STRUCTURE OF THE MARKETING AND SALES DEPARTMENT

The main tasks of the department:

∙ Formation, development and control of the functioning of the dealer network:

∙ Development of sales promotion activities through the dealer direction at the national and regional level;

∙ Monitoring compliance by dealers with the terms of the Dealer Agreement, procedures for connecting subscribers;

∙ Conducting settlements with dealers.

∙ Negotiating and concluding agreements to expand the network of replenishment points

∙ Interaction with partners in the implementation of account replenishment funds on the transfer of goods and mutual settlements, as well as controversial issues on payments not accepted from subscribers.

LOGISTICS DEPARTMENT

The main tasks of the department:

∙ Planning sales of commercial equipment.

∙ Inventory management.

∙ Assigning tasks to sales staff.

∙ Sales quality control.

∙ Evaluation of the results of the work of experts in the sale of subscriber equipment.

∙ Work coordination

Department for research of subscriber equipment

∙ Studying and predicting the performance of new equipment

∙ Issuance of a technical opinion on subscriber equipment

∙ Writing software that optimizes the work of service centers

∙ Troubleshooting and recommendations for their elimination

Department for the organization of payments and electronic means of payment

∙ interaction with partners providing the opportunity to replenish the account of the company's subscribers. banking and non-banking institutions dealers and distributors selling recharge scratch cards, electronic vouchers.

∙ organization of legal, financial and technical interaction with companies,

providing in any possible way replenishment of the account by Intertelecom subscribers

STRUCTURE OF THE DEPARTMENT OF SUBSCRIBER SERVICE

EXPERT AND CALCULATION DEPARTMENT

The main tasks of the department

∙ timely provision of financial and economic

reporting service on connections made for all regional offices for the previous month, reports on equipment sold for all regional offices for the previous month.

SUBSCRIBER DEPARTMENT

The main tasks of the department

∙ control over the timeliness of connections and installation of terminals for privileged categories of citizens

∙ timely submission of documentation to the district

Department of labor and social protection of the population for monthly compensation of the subscription fee of the privileged category of citizens.

∙ monthly, on time, sending legal

persons tax invoices, detailed printouts for the past period

∙ sending invoices for advance payment, letters of termination of contracts

∙ handling complaints (other than complaints about coverage)

∙ approval and accounting of refund applications

∙ work with changes to the standard contract for budgetary organizations

Department of QUALITY CONTROL OF SERVICE

The main tasks of the department

analysis of the Mystery Shopper internal and external audits knowledge snapshots

monitoring compliance with standards for the appearance of premises and displaying goods monitoring compliance with service standards analysis of profitability of the CSO

HEAD OF DEPARTMENT OF SUBSCRIBER SERVICE

SERVICE DEPARTMENT

The main tasks of the department

∙ Control over the number of repairs performed, funds received and used spare parts in all service centers.

∙ Ensuring the smooth operation of regional service centers, organizing the timely delivery of spare parts to regional offices.

∙ Ensuring fast and high-quality service of terminals coming from regional service centers.

∙ Monitoring the implementation of the procedure for the repair of equipment.

OFFICE EQUIPMENT SERVICE DEPARTMENT

The main tasks of the department

∙ Hardware maintenance and ensuring uninterrupted

work of computer equipment and printing and duplicating equipment owned by Intertelecom LLC.

∙ Controlling the execution of users

rules for the operation of computer and printing equipment;

∙ Control of the issuance, movement and write-off of computer

and printing and duplicating equipment within the company, as well as the purchase of equipment, consumables, spare parts

and accessories.

RENT DEPARTMENT

The main tasks of the department

selection of commercial premises, signing of contracts control of payments for rent and utilities monitoring of rental prices, work with landlords

Customer Service Centers

(CALL CENTER)

∙ information support group: operators technical consultation group: engineers group online consultants

∙ corporate client group

∙ telemarketing group

∙ online consultants

The main tasks of the department

∙ consulting, information gathering, recording

appeals of real and potential subscribers of the company, including corporate ones.

∙ informing subscribers about changes in tariffs, conditions, services, etc.

∙ technical consulting for subscribers on setting up equipment (direction of engineers).

∙ customer satisfaction survey

maintenance and services provided by the Company

∙ responses to emails from subscribers on the official website of the Company

∙ work with registers of debtors

∙ selling services over the phone

DEPARTMENT OF ECONOMIC SECURITY AND COUNTERACTION OF VIOLATIONS IN THE NETWORK

The main tasks of the department

∙ detection and prevention of types of fraud aimed at unauthorized actions and unauthorized use of the company's resources and services, as a result of which the LLC

INTERTELECOM bears the loss of income.

∙ Development of algorithms to detect illiquid connections and abuses in the process of servicing subscribers. Monitoring compliance with the order of connections for compliance with approved orders and procedures of the company.

∙ Testing of tariff plans, services, special terms of service, order

connections for compliance with approved orders. twenty

DEPARTMENT OF INFORMATION TECHNOLOGIES

HEAD OF IT DEPARTMENT

Tasks of the Department of Information Technologies:

∙ Collection of primary information for further calculations and analysis.

∙ Automated information processing and computational work to generate all kinds of reports at the request of related departments.

∙ Solving engineering, economic and other problems of production and research character.

∙ Providing related departments with the results of calculations.

∙ Studying the information services market for the development of the department and the information structure of the enterprise as a whole.

DEPARTMENT OF ANALYSIS AND INFORMATION PROCESSING

Main goals:

development and support of software for related departments.

PROGRAMMING DEPARTMENT

Main goals:

construction and maintenance of the computer network of Intertelecom LLC, communication with branches, operability of the computer park and office equipment, development and support

WEB-applications and LLC website

Intertelecom.

Service centers Subscriber service centers of the company of subscribers of the Intertelecom company Intertelecom

COA is open in all COA is open in all

regions of Ukraine, regions of Ukraine,

where there is coverage and where there is coverage and

services are provided services are provided

Serve:

Serve:

Individuals - individuals

Legal entities - legal entities

dealer network dealer network

Dealers are our business Dealers are our business

partners.

partners. Dealer network

The dealer network is represented in each

represented in every region of Ukraine

region of Ukraine

Serve:

Serve:

Corporate clients Corporate clients (SPD and legal entities) (SPD and legal entities)

PROCEDURE FOR CONNECTING INDIVIDUALS AND LEGAL ENTITIES TO SALES AND CUSTOMER SERVICE CENTERS

CONNECTING INDIVIDUALS

To acquaint the Client with the tariffs and rules for the provision of communication services

DOCUMENTS REQUIRED FOR CONNECTING INDIVIDUALS

∙ international passport

conclusion of a subscription agreement

∙ a copy of a valid passport of a citizen of Ukraine of one of his parents, in which the Subscriber is entered in the passport

like his child.

If there is no record of children in the parent's passport, the Subscriber shall submit a copy of his birth certificate.

16 years old, but under 18 years old, who are or were married

Citizens who change their surname due to marriage

(the passport is marked “change within the specified time”)

∙ valid citizen's passport

Parental permission is not required.

∙ Original marriage certificate

∙ Marriage certificate

∙ details of the passport to be exchanged

Emphasize on:

Passport: expiration date must be later than the current one.

Compliance of the photo in the passport with the appearance of the bearer.

If in doubt, the Operator must offer to present another document (driver's license, passport for traveling abroad, military ID, etc.);

The presence of an imprint of the seal of the Ministry of Internal Affairs on the photograph in the passport; Compliance with the Subscriber's age passport;

Availability of required additional photographs (at 25 and 45 years old)

The subscription agreement for this passport can be concluded before the date indicated in accordance with the mark in the passport.

In this case, in the billing it is necessary to enter the data of the passport, which must be exchanged, and the surname - a new one.

Required photocopies

Subscriber's passport (pages with entries) where the name, patronymic, surname, series and number of the passport are indicated,

by whom and when it was issued, photograph (at 25 and 45), signature, registration

passport of one of the Subscriber's parents birth certificate (if the child is not included in the parent's passport)

Subscriber's passport (pages with entries) where the name, patronymic, surname, series and number of the passport are indicated, by whom and when it was issued, signature, registration

Subscriber's passport (pages with entries) where the name, patronymic, surname, series and number of the passport are indicated, by whom and when it was issued, photograph (at 25 and 45 years old), signature, registration

passport to be exchanged Marriage certificate (as confirmation of the new name is provided)

Foreign citizens

Stateless persons

Persons concluding the Subscription Agreement on behalf of the Subscriber

∙ passport of a citizen of a foreign state

marked:

about valid registration on the territory of Ukraine in the bodies of the Ministry of Internal Affairs of Ukraine, entry visa (currently valid)

or a border crossing mark for citizens of countries from whose territory visa-free entry is allowed)

∙ immigration card, which includes:

personal data, host address and visa validity period.

∙ original document replacing the passport

(refugee certificate; refugee travel document to travel abroad

∙ service cards of employees of representative offices

foreign business entities registered in Ukraine

∙ any other document allowing identification

owner (photo, surname, name, etc.) with an entry visa or a mark on crossing the border

∙ original power of attorney (notarized or

other form permitted by the current legislation of Ukraine)

∙ the original of your passport and a copy of the principal's passport

Signing copies of documents

Connection is allowed upon presentation of both an internal passport of a foreign state and a foreign passport, with the exception of cases of promotional connection.

A multiple-entry visa (or a visa valid for at least six months at the current

point in time) or the presence of a mark of registration in the bodies of the Ministry of Internal Affairs of Ukraine.

The immigration card must contain: personal data, as well as the address of the receiving party (i.e. the address of the place that is the purpose of the visit or the place of temporary residence of a foreign

Connection is allowed except in cases of promotional connection.

The absence of a valid registration in a valid passport of a citizen of Ukraine is not a basis for refusing to conclude a Subscription Agreement.

Passport, Visas or Crossing Marks

borders (for citizens of countries from whose territory visa-free entry is allowed).

Document replacing a passport

In the absence of registration, the last address of registration indicated in the passport is fixed as the address of the Subscriber's place of residence.

In the absence of such, the subscriber writes the Application with his own hand: “Addresses of the place of residence: (indicates the full address)”.

Passport of an authorized person Power of Attorney

The subscriber puts the current date and signature on each page with copies of the documents specified in the table "Required documents for connecting individuals"

(if the signature is different, write: “I, full name without abbreviations, I confirm the changes under the signature”, put the current date and again my signature (current).

Forbidden:

Use of ready-made certified copies of documents provided by the Subscriber!

Connect the Subscriber if the data of his passport matches the data of the billing system, which reflect:

 the fact of connecting this subscriber on the terms of the promotion with the signing of an additional agreement and the presence of debt on this connection

 the subscriber's statement about the loss or theft of the terminal, registered in a special ("black") list. Reporting a lost or stolen terminal

is registered in a special (“black”) list only upon personal application of the terminal owner to the CPOA upon presentation of a passport. (Do not connect to this particular terminal, which is in the "black" list)

SALES CENTERS ALSO CONNECT LEGAL ENTITIES

3. Bank certificate on opening an account (Date of issue no more than 30 days). register. This document is valid for one month. This document is provided in

Connecting a subscriber in the "Clients" program:

1. Connect the Subscriber in the "Clients" program with the obligatory filling in of all fields.

∙ Additional Agreement(s)(if provided by the terms of connection).

The Additional Agreement is drawn up and signed for each telephone number, if these telephone numbers are on different personal accounts

∙ Acceptance certificate (for connection amount)

∙ Invoice for the issuance of equipment and warranty card(if equipment is purchased)

Of what consists of connection payment and what remains about the subscriber:

The package of documents to be submitted Xia in the archive of the company:

Invoice for the release of terminals (accounting)

see also

"Instructions for using the "Clients" application as part of ACP Billing_IT 2.0.5 Version 2.0 (07.07.2009)"

Information for the new Intertelecom Subscriber!

Congratulations, you have become a subscriber of Intertelecom LLC! You are the owner of a direct city telephone number.

In addition to the direct landline number, you will receive a gift mobile number with the code 094. The last three digits of the 094 number coincide with the last three digits of the landline number.

When calling to city operators, your direct city number will be determined. When calling to mobile operators, the mobile number 094 will be determined. Your friends can choose which number is more profitable for them to call from their operator.

You have the opportunity to earn money by receiving incoming calls to number 094. You can use communication services throughout Ukraine, where there is company coverage,

without additional terminal settings.

When moving from one region to another, the rate of outgoing calls remains the same, as if you were in your city. Incoming calls are also free.

For the operation of your number, a prerequisite is the timely payment of the subscription fee, depending on the tariff plan you have chosen. The subscription fee for using the direct city number is charged on the 1st day of each month. AT

If the funds on the account are not enough to pay the subscription fee, a few days before the start of the new month, the autoinformer will remind you of this. If the subscription fee is not paid, outgoing and incoming calls will be blocked after 6-10 days.

To include the number in the work, you need to replenish the account in a way convenient for you

month, during the validity of the supplementary agreement.

When you pay the monthly fee, you are credited with package minutes that can be used for local landline numbers. The paid subscription fee and the balance of prepaid minutes do not roll over to the next month. The balance of funds on the subscriber's account, in excess of the subscription fee, is transferred from month to month.

Calls in the national network of Intertelecom LLC between subscribers served on regional and district numbering are free of charge.

Calls within the region, within Ukraine, to the networks of mobile operators and international calls are paid separately - in excess of the monthly fee, depending on the tariff plan you have chosen.

To make outgoing calls in any direction, the balance of money on your account must be more than 00.00 UAH.

There is no connection fee.

Calls are billed per second, starting from the first second of the call.

By connecting under certain conditions, you always have the opportunity to order additional services: caller ID, call forwarding, conference calls, call waiting, voice mail, fax and Internet, Mobile Hit, Free Internet, Unlimited access, 3G Access 500.

If necessary, you can use such services as: change of tariff plan, temporary termination of the contract (in the absence of a valid additional agreement), change of owner, change of number, blocking for loss, change of equipment.

For individuals, there is an additional opportunity: use the self-service system (ACCA) on the company's website https://assa.intertelecom.ua.

You can always get any information you are interested in:

∙ in the company information center by typing*750 from your number or

∙ number 0-800-50-50-75 / 094 50 50 750 (if you are calling from another operator's number);

∙ *800 - for corporate subscribers

∙ on the official website of the company www.intertelecom.ua

∙ at Intertelecom Sales and Customer Service Centers in your city.

∙ By contacting the Online consultant from the main page of the Intertelecom website.

30. Is it possible to use one phone number on several terminals at the same time?

31. Is it possible to use your services using a GSM phone?

There is no such possibility

No, because the GSM and CDMA standards are based on different technological principles. But there are two-standard telephones in customer service centers.

Additional services

Automatic Caller Identifier (CLI) Call Waiting Conference

Call forwarding Complex package of additional services "Complete"

Short Message Service (SMS) Who called service

Service “On call again” SIP-number

SIP multichannel International roaming in Pridnestrovie International roaming "Around the world"

100 minutes to mobile networks All the world with Intertelecom - Russia INTERNET access

Providing permanent monthly

Rek Lamny

Administrative Services

(paid as a one-time payment upon the order at the TsOA)

Temporary termination of the contract. Extension of suspension.

Restoration of the contract (from suspension).

Owner change. Number change.

Change of equipment (changing the subscription form)

Blocking on loss Change of tariff plan Number deactivation

One-time printout of Internet traffic One-time printout of calls Reactivation

Standby mode Optional number

Inclusion of the number in the call center of JSC "Ukrtelecom"

Billing services

(paid upon consumption)

Outgoing calls Internet traffic Sending SMS Sending/receiving a fax

Confidential Call Content Services Audiotex

My messages (Mail.Ru, My World, Mail.Ru Agent, Gmail,

One and the same service can be both administrative, and additional and billing, For example: administrative service - upon connection, the Fax transmission service is ordered (activation 5 UAH) additional service - paid every month (10 UAH)

billing service - payment for incoming / outgoing connections 0, 20 UAH.

Description of services

Additional services

(paid every month along with the subscription fee)

Automatic Number Identifier (CAN)

The service will allow you to determine the number of the calling subscriber and display on the terminal display:

- telephone number of the subscriber who called you;

- the name of the caller from your phone's address book (depending on the terminal model).

It is also possible to view on the display of the device (depending on its model) one or another

the number of phone numbers of recent incoming or missed calls.

How to order the service "AON".

How is the AON service charged?

service paid)

Attention! The service works only if your device supports the automatic number identification function.

Call Waiting

The Call Waiting service allows you to answer an incoming call while the subscriber is already talking on the phone.

During the call, you will hear a short beep, which means that your number received another call. At the same time, the subscriber who dialed your number will hear the usual long beeps with a sharp break in a different tone at the end of the beep and the message “Check out the subscriber, please, please.” Thanks to these beeps and a message, you can determine that the person who is being called on the phone is busy on the first line.

You can answer an incoming call without interrupting the current call by pressing the CALL button. Press CALL to switch between conversations.

If you wish to ignore the incoming call, do nothing.

How to order the "Call Waiting" service.

You can order this service at ACCA, at the CIP, having passed identification, from dealers or at the nearest customer service center by filling out an application form.

This service is included in the work automatically, after its order and payment.

How to manage the Call Waiting service.

The ordered “Call Waiting” service can be managed on the terminal in the following way: activation – dial *43 and press CALL

deactivation - dial #43 and press CALL.

How is the Call Waiting service charged?

Monthly subscription fee:

In most tariff plans it is provided free of charge, (there are tariff plans in which the cost

service paid)

Call forwarding

This service will allow you not to miss an important call when you are outside the coverage area of ​​LLC

“Intertelecom” when you cannot answer a call or your terminal is disconnected.

A call that arrives at your terminal can be forwarded as to a device of any telephone network, including an international number. The set call forwarding will not prevent you from making outgoing calls from your device.

There are the following types of redirects:

- unconditional (for all incoming calls)

- by subscriber's non-response

- according to occupancy

- by non-response and employment at the same time

How to order the "Call Forwarding" service.

You can order this service at ACCA, at the CIP, having passed identification, from dealers or at the nearest customer service center by filling out an application form.

This service is included in the work automatically, after its order and payment.

How to manage the "Call Forwarding" service.

Enabling forwarding on the terminal is possible as follows:

How is the call forwarding service charged?

Monthly subscription fee:

In most tariff plans it is provided free of charge, (there are tariff plans in which the cost of the service is paid)

One-time fee for each minute of forwarded call 0.20 UAH. + cost of a call to a direction (depends on the tariff plan).

Conference call

The service allows you to organize a conversation simultaneously with two subscribers.

How to order the conference call service.

You can order this service at ACCA, at the CIP, having passed identification, from dealers or at the nearest customer service center by filling out an application form.

This service is included in the work automatically, after its order and payment.

How to use the "Conference call" service.

To create a conference call on the terminal, you must:

1. Establish a connection (incoming or outgoing) with one subscriber

2. Dial the number of another subscriber and press the CALL button

3. After establishing a connection with the second subscriber, press the CALL button again.

How is the conference call service charged?

Monthly subscription fee:

A one-time fee for each use of the service is calculated as if you made both calls separately - a fee is charged for each of your outgoing calls, depending on its duration and direction.

Complex package of additional services "Complete"

The comprehensive package includes:

Caller ID, Call waiting, Conference calling, Forwarding.

How to order and activate the "Complete" service.

You can order this service at ACCA, at the CIP, having passed identification, from dealers or at the nearest customer service center by filling out an application form.

Each of the services included in the package is included in the work automatically, after ordering and paying for the service

How to use and manage the "Complete" service.

Each service included in the package is activated and managed individually, depending on which of the 4 services you want to use. The principle of activation and operation of services from the package is indicated

How is the “Complete” service charged?

Monthly subscription fee:

In most tariff plans it is provided free of charge, (there are tariff plans in which the cost of the service is paid)

Short Message Service (SMS).

Sending SMS.

An Intertelecom subscriber can send SMS messages (provided that the telephone set supports this function) both within the network and outside it, to subscribers of other operators. Sending SMS-messages outside the network "Intertelecom" is carried out with the participation of a third-party company "Center for Global Messages Ukraine" (CGSU). List of operators available for SMS exchange

Order the "sending SMS" service

You can order this service at ACCA, at the CIP, having passed identification, from dealers or at the nearest customer service center by filling out an application form.

This service is included in the work automatically, after its order and payment.

How to use the "sending SMS" service.

To send messages within the network, the recipient number must be specified in long-distance format, both for direct capacity and for mobile:

0+area code+ subscriber number (for example: 0481234567) 094+ subscriber number (for example: 0941234567)

To send a message outside the "Intertelecom" network through the CGSU, the recipient's number must be specified in the following format (for national operators):

0+operator code+subscriber number (for example 0501234567)

To send a message outside the "Intertelecom" network through the CGSU, the recipient's number must be specified in the following format (for foreign operators):

00 + country code + operator code + subscriber number (for example: 0079152222222 - to send a message to

MTS Russia).

How is the SMS service charged?

Tariffication is different, depending on the tariff plan on which the subscriber is served.

Attention! When sending an SMS outside the Intertelecom network, the message delivery report means that the message was successfully delivered to the CGSU server, but not to the recipient's terminal. Tariffication of SMS sending occurs in case of successful delivery to the server of the Central State Statistics Service.

SMS reception

An Intertelecom subscriber can receive SMS messages:

- from the Company's website www.intertelecom.ua

- from the terminal of the Intertelecom network

- from national and foreign operators connected to the Central State Statistics Service (only to mobile number 094, when sent to a direct city number, the message will not be delivered)

How to order the "SMS reception" service

The service is available to all subscribers of the Company, there is no need to order it

How is the SMS service charged?

The service of receiving SMS is free of charge in all tariff plans.

Usually, users do not think about the difference in communication standards when choosing a mobile operator. Nevertheless, there are differences between them and CDMA successfully coexists with the dominant GSM in the Ukrainian market. In this material, we will try to figure out what the difference is, what benefits GSM can give to the user, and which CDMA.

Since its inception, mobile communication has gone through several rounds of evolution. The first communication standards related to the 1G generation were wireless analogues of conventional telephone communication. They had many disadvantages: high transmitter power, which could adversely affect health, low capacity of base stations, poor noise immunity. Omitting the intermediate stages of their development, they were quickly replaced by second-generation 2G networks.

The first digital standard was GSM, which provided the best noise immunity, protection against interception and voice quality through the use of a voice codec. Developed by the European Telecommunications Standards Institute (ETSI), it began to be implemented in 1991, gradually becoming the most common. Already in 1993, Qualcomm developed an alternative IS-95 standard (cdmaOne) based on CDMA technology, which began to be implemented in 1995.

What are the main differences?

The key difference between these standards is the way of working with the frequency resource.

GSM uses channel separation based on time and frequency. A small frequency band is allocated for each subscriber, on which the phone communicates with the base station. In this case, the “sessions” of data exchange are fixed in time. With a certain simplification, let's say that the signal is interrupted, but due to the high frequency of data transfer, the subscriber does not notice this. In real life, interruptions are noticeable only by the characteristic squeaking sound of the speakers when there is a phone nearby that calls or receives a message.

In turn, CDMA uses code division of signals. Each subscriber connected to the base station uses the entire available frequency resource, common to all subscribers, and the base station communicates with everyone at the same time. The signal from a particular user is selected using code modulation - each subscriber has a specific "code", which allows you to select it from the general radio air.

Different schemes are easier to describe with one simple example. Imagine that there are several people in a room, divided into pairs. The first part communicates in the same language, they speak in turn, for example, for 20 seconds - this is a description of GSM. The second part speaks simultaneously, but in different languages ​​- this is CDMA. In both cases, people communicate normally, but continuous conversation is obviously more comfortable, especially since the neighbors simply do not understand what they are talking about nearby.

What are the benefits?

The difference in operating principles, a wider frequency band allocated to a CDMA subscriber, result in certain advantages of CDMA over GSM. For the subscriber, they are:

• better voice quality – large bandwidth is resistant to interference
• security - from the side, the intercepted CDMA signal looks like noise, it is difficult to distinguish an individual subscriber from it
• lower power consumption of the communication device - the signal power in the CDMA network is less compared to GSM and depends linearly on the distance to the base station. This also affects security, as a signal of lower power is harder to fix.

For operators, the benefits of CDMA lie in the greater capacity of base stations, their range, easier network setup, congestion tolerance and the ability to adapt to specific tasks. CDMA operators can cover more area with less equipment that is easier to configure.

A natural question arises - if CDMA is so much better, why is GSM the most common standard? The reasons are pretty simple. At the time of creation, CDMA GSM already existed, there was a choice of ready-made solutions for both operator equipment and consumer equipment. A more advanced CDMA required more computing power, the creation of new solutions for a less common technology, and, for example, conventional phones cost more than their GSM counterparts and were not compatible with them.

In addition, there was a user-friendliness issue. In the GSM network, the subscriber identifier is a SIM card, it stores the information necessary for the operator. A user who wants to change an old mobile phone to a new one simply rearranged the SIM card. To work in CDMA networks, the necessary data was recorded (flashed) into the phone itself; in principle, it did not have a slot for a SIM card. Therefore, changing a mobile phone entailed the need to visit the operator's salon, and the existing phone could not be used in other countries, for example, in roaming. SIM analogue for CDMA appeared in 2002 and was called R-UIM. Phones operating in both CDMA and GSM began to appear, the problem of a limited choice of devices was gradually resolved. American operators played their role in this, which became the locomotive for the development of the standard. In the Ukrainian CDMA market, operators occupy a noticeably smaller share, the choice of compatible smartphones or phones is less, but some of the equipment is imported by operators, and users, if they wish, can buy a suitable smartphone on international platforms.

If we take into account the pros and cons, it turns out that the technologies look comparable from a consumer point of view, the final choice comes down only to the coverage of the operator.

Evolution

The conclusions voiced are applicable primarily from the point of view of ordinary telephone communication, but conversations have long become just one of the services of operators against the background of Internet access.

Initially, the GSM standard provided the highest possible data transfer rate of up to 9.6 kbps. GPRS and EDGE technologies, which belong to the 2G generation, made it possible to accelerate to a theoretical 474 kbps. In the third generation of UMTS GSM networks, WCDMA technology is used for data transmission, which is a derivative of CDMA, it uses a similar code division of channels. Further development of technologies and the introduction of HSPA + and DC-HSDPA (for example, Kyivstar and Life) provide a theoretical data exchange rate of 42.2 Mbps (Kyivstar, combining two "carriers") or even 63.3 Mbps ("Life", three "carriers").

The original CDMA had a greater margin of safety and provided data transfer rates up to 153 kbps. The subsequent phases of the development of the standard are already classified as 3G networks, EV-DO technology is used for data transmission. Depending on the implemented generation of the standard (Rev.), the maximum data transfer rate in such a network varies from 2.4/0.153 Mbps (Rev. 0, upload/download) to 73.5/27 Mbps (Rev. B) . Naturally, the figures given for each standard are theoretical, it is impossible to achieve such speeds for all connected subscribers and the real access speed turns out to be several times lower. Plus, it all depends on the implemented technologies. For example, Intertelecom in large cities operates on the Rev. B and provides speeds up to 14.7 Mbps.

Thus, in theory, further development of 3G networks and an increase in data transfer rates are possible, but from a practical point of view, the solution looks doubtful. The available speeds cover the needs of users well (if you don’t come up with crazy scenarios with the distribution of torrents in 24/7 mode), and the technologies pull backwards compatibility with 2G networks and support for old phones.

Ministry of Education of the Russian Federation

VORONEZH STATE TECHNICAL

UNIVERSITY

abstract

on the subject of digital devices on the topic:

Cellular CDMA standard.

Problems of implementation and operation

in Russia.

Completed:

Student of the SSK group - 972

Litvinov A.

Supervisor:

Shifrin V.M.

Voronezh

Plan:

1 CDMA as a tool for solving economic problems;

2 Code division digital cellular mobile radio systems:

2.1. principles of code division of channels;

2.2. cellular mobile radio system with code division of channels of the IS-95 standard;

2.3. security aspects in the IS-95 standard;

2.4. mobile station of IS-95 standard;

2.5. base station of IS-95 standard;

2.6. the use of CDMA in wireless communication systems such as WILL;

3. Mobility in CDMA systems.

4. Problems of CDMA functioning in Russia.

5. Conclusion.

CDMA as a tool for solving economic problems

There are three tasks for regional operators leading to economic success:

1. development of the telephone network.

2. Reconstruction and renewal of the existing network, improvement of communication quality.

3. Expansion of types and number of services.

The development of the telephone network, in turn, is based on three main requirements of a solvent consumer:

The speed of the application;

Installing the phone in any geographic location;

Speed ​​of connection and high quality of conversation;

Place system CDMA in the development of telecommunications in the region.

From the first days of operation, modern communication technologies make it possible to avoid unproductive labor at all stages, from design to construction and operation. Ease of design and installation of the CDMA system was evaluated.

This system immediately became popular. Behind it, a stable demand was entrenched, which is characteristic, however, for all radio systems that create the possibility of immediate installation of a telephone in those areas where wired networks have not reached for years. These are one-story arrays of cities, suburban summer cottages, suburban farms.

Customer feedback has confirmed the benefits of CDMA. The system is characterized by the best voice quality and connection reliability. A significant role is played by the quality assurance of security against unauthorized access. Reasonable tariff policy and communication quality, convenient local numbering create the necessary popularity for the system.

The need to change technologies.

Modern equipment does not leave us a chance to build and operate networks according to the old rules. If we change the coordinate station to a digital one, we are forced to carry out a certain reconstruction of the subscriber network, to change almost the entire network of subscriber lines. There is no return to multi-kilometer pole lines, bare communication cables with low insulation. At the same time, we will not be able to build lines for four or five subscribers of a farm or settlement with an armored cable buried at least a meter deep into the ground to protect against gusts for economic reasons. Modern radiotelephone systems are one of the most acceptable, in our opinion, methods of providing telephones to areas with a low population density.

Coordinate and decade-step stations make up 80% of the switching equipment in the region. Cable economy and overhead communication lines are older than switching systems. The task that all operators are forced to solve is the problems of the village. A full-fledged reconstruction and renewal of rural telephone communications can become a reality only when the population's solvency is restored, but a solution needs to be prepared today. One should not disregard the option of a certain development of the economy, when the depreciation of rural networks will put before the operator the task of their forced reconstruction.

Reconstruction of rural telephone communication and CDMA .

One of the main tasks that CDMA can solve is the replacement of worn-out rural stations and subscriber lines. The system allows serving subscribers within a radius of 30 kilometers or more. With the help of CDMA, it is possible to release and transfer exchanges that are still able to work from areas where base stations are installed, although such solutions can only be temporary and forced.

It is advisable to use the recently certified remote concentrators of the QCT - 8000 series, which allow you to install telephones in individual buildings and compact villages. In the apartments of users, a standard wired telephone set is installed, which is 5-6 times cheaper than radio telephones.

In addition to the tasks of development and reconstruction, it was very important to solve the problem of providing modern additional services, including for the most distant rural settlements. These are data transmission and facsimile services, Internet services. Tests of the latest modification of Qualcomm's QCT-1000 device showed that data transfer is feasible at a high level, which significantly expands the circle of consumers.

Currently, various research organizations are paying considerable attention to the development of mobile radio systems for cellular and microcellular structures of a new generation with code division channels (CDMA). One such development is the CJDIT project funded under the RACE program by the European Community. Until recently, the implementation of the CDMA system has been hampered by the lack of a number of technical solutions, including the problems of implementing subscriber stations with acceptable consumer qualities.

One of the first cellular mobile radio communication systems with code division of channels was developed by Qualcomm (USA), the principles of its construction are the basis of the US CDMA standard IS-95.

Assessment of the state and development trends of cellular communication systems with code division of channels is of interest to operators and future subscribers of these networks.

Code division principles

On September 28, 1995, Hutchison Telephone (Hong Kong) launched the world's first digital Code Division Multiplexing System (CDMA) into commercial operation. The network is built on Motorola equipment: SC9600 base stations and an EMX2500 switching station

The principles of code division of communication channels (CDMA - Code Division Multiple Access) have been studied in detail and considered in many works. They are based on the use of wideband signals (WBS), the bandwidth of which is much higher than the bandwidth required for conventional messaging, such as in narrowband frequency division multiplexing (FDMA) systems. The main characteristic of NLS is the signal base, defined as the product of its spectrum width F and its duration T:

In digital communication systems that transmit information in the form of binary symbols, the NPS duration T and the message rate C are related by the relation T = 1/C. Therefore, the signal base B = F/C characterizes the expansion of the NPS spectrum relative to the message spectrum. The expansion of the frequency spectrum of transmitted digital messages can be carried out by two methods or a combination of them:

1. direct expansion of the frequency spectrum;

2. carrier frequency hopping;

Existing and developing cellular communication systems mainly use NLS, the formation of which is carried out according to the direct spectrum spreading method (DS-CDMA-Direct Sequence-CDMA).

The creation of cellular mobile radio communication systems with code division of subscribers was constrained by the lack of technical and technological capabilities for the implementation of small-sized, low-power and multifunctional devices for "compressing" the NPS. At present, these problems have been successfully solved by the American firms Qualcomm, InterDigital, Motorola. Based on proposals from Qualcomm, the US adopted the IS-95 standard for a cellular mobile radio system with code division.

Cellular mobile radio system with coded

channel separation standard IS-95.

Cellular system of mobile radio communication with code extension of channels (CDMA) was first developed by Qualcomm (USA). The main goal of the development was to increase the capacity of the cellular communication system in comparison with the analog one by at least an order of magnitude and, accordingly, increase the efficiency of using the allocated frequency spectrum.

Technical requirements for the CDMA system are formed in a number of standards.

Qualcomm's CDMA system is designed to operate in the 800 MHz frequency band.

Security or privacy is a feature of CDMA technology, so in many cases, cellular network operators will not need special message encryption equipment.

The Qualcomm CDMA system is based on the Direct Spread Spectrum method based on the use of 64 types of sequences formed according to the Walsh function law. For the transmission of voice messages, a speech converting device with the CELP algorithm with a conversion rate of 8000 bps (9600 bps in the channel) was selected. Operating modes at speeds of 4800, 2400 and 1200 bps are possible.

The handshake protocols in CDMA, as well as in the AMPS and N-AMPS standards, are based on the use of logical channels.

In CDMA, channels for transmission from a base station are called forward (Forward), for reception by a base station - reverse (Reverse). The channel structure in CDMA in the IS-95 standard is shown in the figure:

Direct Reverse

Forward Channel Reverse Channel

Pilot channel Access channel

Pilot Channel Access Channel

Call channel

Direct traffic channel

Forward Traffic Channel

The structure of communication channels in the CDMA standard IS-95

Direct channels in CDMA:

· leading channel - used by the mobile station for initial synchronization with the network and control over the signals of the base station in time, purity and phase;

· synchronization channel - provides identification of the base station, the level of radiation of the pilot signal, as well as the phase of the pseudo-random sequence of the base station. After the specified synchronization steps are completed, the connection establishment processes begin;

call channel - used to call a mobile station. After receiving the call signal, the mobile station transmits an acknowledgment signal to the base station, after which information about the connection establishment and assignment of the communication channel is transmitted to the mobile station via the call channel. The paging channel starts working after the mobile station has received all system information (carrier frequency, clock frequency, signal delay over the synchronization channel);

· direct access channel - designed to transmit voice messages and data, as well as control information from the base station to the mobile.

Return channels in CDMA:

· access channel - provides communication of the mobile station to the base station when the mobile station is not using the traffic channel. The access channel is used to establish calls and respond to messages sent over the call channel, commands, and network registration requests. Access channels are combined (combined) with call channels;

· reverse traffic channel - provides transmission of voice messages and control information from the mobile station to the base station.

The following figure will show the procedure for establishing a normal connection (incoming call to a mobile station).

mobile station Base station

Accepts Search message Transmits Search message or

channel Separated paging message (MIN) of the call

· Transmits Reply to search message Accepts Reply to search message

(MIN,ESN) channel Tuned to assigned

access information channel using a common

long code.

Starts transmitting insignificant data over

direct traffic channel

Accepts Appointment message Transmits

channel channel (ESN, CDMA channel, channel code)

Tuned to assigned call channel

communications using a common long code.

Receives N consecutive frames from

base station

Starts transmitting the channel preamble Receives the channel preamble from

connection to the reverse traffic channel. mobile station

Accepts confirmation command Transmits confirmation command

base station direct channel base station

Starts dropping received traffic packets

with service requests and send

data over the reverse traffic channel.

Accepts Ready signal s Transmits Ready signal with

information message. direct channel information message

traffic (ringing signal, CNI - caller number)

Gives a ringing signal to the mobile reverse channel

radiotelephone. traffic

Displays CNI information on the scoreboard

mobile radiotelephone.

(Subscriber answers the call)

Removes the ringing tone

mobile radiotelephone.

· Transmits connection command Accepts connection command

begins to transmit information channels of the reverse

traffic confirmation packets

service.

Receives confirmation Sends confirmation

channel direct

(conversation of subscribers) (conversation of subscribers)

Normal connection establishment procedure (case of incoming call at the mobile station). The call to the subscriber unit may include a phase when a specific desired option (option) of the service is set.

The figure shows the procedure for passing a normal call (outgoing call from a mobile station)

Mobile station Base station

· Detects a call being sent Receives initial message

mobile station user. Channel Set to the assigned traffic channel,

· Transmits initial message access using a common long code in reverse

(ESN, MIN, dialed digits) traffic start.

Starts transmitting idle traffic channel data on the forward link.

Accepts Appointment message Transmits Channel Assignment Message

channel. Call channel (ESN, CDMA channel, code channel).

· Tuned to the traffic channel, Authenticates the MIN and ESN of the mobile station.

using a common long code. Receives the traffic channel preamble from

· Receives N consecutive valid mobile stations.

real frames from the base station.

Starts transmitting the channel preamble

Accepts confirmation command Transmits The command to confirm the basic

base station. direct channel stations.

· Start transmitting traffic packets to traffic

Service Option 1 and from Service Option 1.

Accepts Continuation of the initial

· Transmits Continuation of the initial return channel messages.

messages. traffic

· Accept confirmation. Sends an acknowledgment.

direct channel

Possible procedure (optional)

Accepts Jump request command Direct Channel Transmits command Request to switch to

to a private long code. traffic private long code

Sends an acknowledgment along with Receives a message Command received about

message Command received about return channel

switch to private long code traffic

Starts to send and receive information Starts to send and receive information

information using a private long code using a private long code.

Possible procedure (optional)

Accepts Ready signal together Transmits Ready signal together

with information message direct channel with information message(signal

ringback traffic)

· Sends an acknowledgment. Accept confirmation

return channel

Gives a signal to control the sending of traffic

calls over the speech path.

(the called party answers the call)

Possible procedure (optional)

Accepts Ready signal together Transmits Ready signal together

with information message. direct channel with information message.(silence)

Sends confirmation Receives confirmation

· Disables ringback tone Reverse channel

in the traffic path. traffic

(conversation of subscribers) (conversation of subscribers)

In the IS-95 standard, the power level of the signal emitted by the mobile station is controlled in a dynamic range of 84 dB in 1 dB steps. This makes it possible for the base station to receive signals from mobile stations at substantially the same power level regardless of the distance to the base station. The closer the power level of signals from mobile stations at the input of the base station to the minimum corresponding to the required communication quality, the lower the level of mutual interference in the system and, consequently, the higher its capacity.

The high power level control requirement of the mobile station can be attributed to a disadvantage of the Qualcomm system. The second disadvantage of Qualcomm CDMA is the need to use cells of the same size throughout the network, otherwise there is mutual interference from the signals of mobile stations that are in neighboring cells of different sizes.

The CDMA standard provides greater network capacity than traditional analog cellular networks. Capacity increase can be achieved in two ways:

1) increase in the number of channels per MHz of the allocated frequency band;

2) an increase in the reuse of communication channels in a given territory.

A factor contributing to the reduction of mutual interference in the CDMA system and, consequently, to an increase in its capacity, is the use, similar to GSM, of a discontinuous speech transmission system.

On the interval of the communication session, the active part of the conversation is about 35%, 65% falls on listening to messages from the opposite side and pauses. The emission of a signal by the mobile station only during intervals of voice activity leads to an additional reduction in system interference and an overall increase in the capacity of the CDMA system.

The following table will list the main characteristics of CDMA and their brief description, which determines the advantages and prospects of cellular communication systems with code division.

Characteristics and their description

High throughput.

Field tests conducted under various conditions have confirmed that under high load, the throughput of CDMA systems is on average 15 times higher than the throughput of analog systems. Finally, by using existing vocoders that operate at half the bit rate, throughput is increased by a further 1.7 times. Additional sectorization (above 3) also increases throughput.

High quality connection.

A variable bit rate vocoder provides speech-to-digital conversion and high-quality speech reproduction. Background signals are muffled even under heavy load. The soft handover method (switching the subscriber from one radio channel to another) used in CDMA systems provides almost transparent transfer of calls between cells. This reliable transmission method virtually eliminates call drops and reduces the load on switching equipment.

Possibility of further evolution of the system.

The existing system provides for search services and digital data transmission. The existing control structure provides facsimile protocols. Higher transmission rates may also be envisaged. Portable subscriber stations based only on the CDMA method and compatible with cellular systems and PBXs may meet future requirements.

Possibility of introducing new functions.

If desired, you can access a wireless PBX, home cordless phone, public cordless digital telephones, personal network, and cellular networks from the same machine, if desired. Interfaces with PBX, ISDN network and public switched telephone network are provided. Digital control signals provide a range of data services that can be added as the operator introduces new services. The variable rate vocoder and the data capability provided allow the introduction of different levels of service. The signal level and delay measurements provided in the system make it possible to determine the position of the mobile station.

Communication privacy.

The digital form of signals, transmission in a wide frequency band, protection of information for each addressee - all this provides a much higher secrecy of communication than in other systems.

Ease of transition (and compatibility with analog systems)

CDMA allows you to almost triple the existing bandwidth in analog networks and provides a higher quality of service. Throughput and radio coverage allow the introduction of CDMA with a much smaller number of cells than existing networks. Antenna coverage and sectorization are cell independent and not as tightly coupled as in a narrowband system. Subsequent expansion can be incremental and can be local (to quickly provide radio coverage in one place) or global.

Price and availability of equipment

Existing CDMA system cost estimates for network and subscriber equipment show that the cost of this system is equivalent to existing analog systems. Higher bandwidth allows communication with significantly fewer cells than analog and TDMA systems, reducing capital and operating costs. Proven custom integrated circuit technology has reduced complex CDMA circuit technology to very simple solutions.

The IS-95 standard provides a high degree of security for transmitted messages and subscriber data.

Communication security is also ensured by the use of authentication and message encryption procedures.

Encryption of messages transmitted over a communication channel (TSN) is also carried out using the procedures of the IS-54B standard.

IS-95 also uses a "frequent communication" mode, provided by a secret mask in the form of a long code.

Mobile station standard IS-95

Qualcomm and Motorola have developed dual-mode CDMA mobile stations that communicate with existing analog frequency modulated networks (AMPS and N-AMPS). This circumstance provides significant advantages to CDMA subscribers, as it allows you to use your radiotelephone where existing analog cellular networks provide radio coverage.

The main difference between CDMA subscriber stations and existing analogue standards stations is the addition of digital signal processing functions to CDMA mobile stations.

base station standard IS-95

CDMA communication systems use omnidirectional or sector cells (typically 120 degrees)

The following figure will show a block diagram of a base station (BTS) for a omnidirectional antenna cell with digital equipment that includes channel units.

Amplifier

Transceiver

GPS receiver

Cell controller

Block diagram of a CDMA base station

Each channel block can be configured as a traffic channel or as a service channel. A GPS (Global Positioning System) receiver is used to synchronize the network.

The transceiver compartment converts the intermediate frequency signals generated in the digital block compartment into a radio frequency signal at a carrier frequency and provides inverse conversion of the received signal to an intermediate frequency. In the transmit direction, the signal passes from the transceiver through a power amplifier and filter to the transmitting antenna. In the reverse direction, the receive path begins with receiving antennas, a filter, and a low noise figure amplifier. Then, in the transceiver, the signal is converted to an intermediate frequency and enters the digital equipment compartment. It should be noted that the transmitting and receiving paths are connected directly to their antennas.

The operation modes of digital equipment and the transceiver are controlled by the cell controller (CC)

The use of CDMA in wireless communication systems such as WILL

In recent years, considerable attention has been paid to the development and implementation of wireless radio communication systems (WILL) to serve fixed subscribers in rural and hard-to-reach areas. In this area, the developments of Motorola, Alcatel, Siemens, etc. are known. Under certain conditions related to the number of subscribers served and their remoteness from the public telephone networks (PSTN), the laying of cable communication lines becomes economically inefficient compared to the introduction of radio channels to connect fixed subscribers to the PSTN. Typically, the use of WILL is considered appropriate for servicing subscribers remote from the PSTN at distances from several kilometers to several tens of kilometers.

As noted earlier, CDMA systems have a number of advantages over existing cellular networks and allow increasing network capacity. However, the advantages of CDMA are provided by the complication of the functioning of the network and user equipment, which become invisible when using advanced methods of digital signal processing, high-speed computing tools and modern microelectronic technologies.

In the version of the wireless communication network for fixed subscribers, continuous control of the power level adjustment of the subscriber stations is not required, the radiation level can be fixed once when the subscriber station is installed. To reduce system interference, directional antennas are used for subscriber stations (in the direction of the base station). All this makes it possible to provide an even greater capacity of the WILL CDMA network compared to the mobile cellular network.

Overall, CDMA technology, when used on the WILL network, delivers an 18- to 20-fold increase in capacity, according to Motorola's estimates, compared to the analog AMPS network.

Fixed placement of subscriber stations, the use of directional antennas in the direction from the subscriber station to the base station allows you to implement a 60-degree cell, that is, to ensure the simultaneous operation of 180 active subscribers. With a load from one subscriber to 0.025 Erlang, the number of subscribers served by one 60-degree cell will be about 7000. These results confirm the high efficiency of using CDMA to build wireless communication systems with a fixed subscriber.

Mobility in CDMA systems.

CDMA system operators and those simply interested in the introduction of this technology in Russia are aware of the decision of the board of the State Communications Committee on the recognition "it is expedient to create in Russia on the basis of the IS-95 standard in the 800 MHz band only wireless access networks to local telephone networks." Thus, the "link to the countryside" of the most advanced mobile communication standard has been finally approved.

Consider the current situation from the point of view of a law-abiding CDMA network operator, for which we first define two important concepts.

What is mobility? In full - this is the service of a subscriber with a portable telephone with the possibility of roaming - national or international. Mobility is characterized by high traffic charges and its low intensity, no external directional antennas are used, and the working area is probabilistic in nature. The normative document will be the "Rules for the provision of mobile services" that are currently being developed.

"Stationarity" - a fixed installation of a radiotelephone with dimensions very close to a conventional telephone set, or a subscriber radio module with a standard telephone interface. High traffic intensity per subscriber and low cost are required. Very often external antennas and 100-th radio access to the telephone network are needed. The conditions for the provision of radio access services are governed by the "Rules for the provision of telephone services".

At the same time, radio access provides relative mobility - the ability to work in various places of the radio coverage area and even in a moving car.

So, let's consider some problems that arise during the operation of stationary radiotelephones. On sale are fixed telephones from Qualcomm, Samsung and LG. The telephone set includes a battery power supply, which provides 8 hours of talk time in case of contact with the mains. This source allows you to operate the phone autonomously. Many subscribers understood the possibilities of CDMA phones and began to use them as mobile phones, transporting them in a car. Of course, such use is prohibited by our rules for providing communication services via the CDMA system, and this is noted in the contract with the subscriber, but how to identify the violator, how to prove the fact of violation and what to do next?

First of all, it was necessary to solve the technical problem of detecting the mobility of phones. An analysis of the billing records of the Qualcomm controller revealed two existing parameters - the number of sectors in which the conversation began and ended, and the value of the distance to the phone in this conversation. Knowledge of the working sector turned out to be ineffective, since with a sector width of 120 0 and a system range of 20 ... 25 km, the sector area is 400 km 2, and when a telephone is installed at the border of two sectors, the working sector can change several times during one conversation (hand-off).

The most informative is the distance to the phone. A large number of billing records for obviously fixed and mobile phones were analyzed. Based on the results of the analysis, it turned out that the distribution function of the range for calls to landline phones is close to normal and its value is 3σ ‹ 200 conventional billing record units. The range distribution function for mobile phones can be arbitrary, with maxima at ranges corresponding to the most frequent stops.

Empirically, the stationarity criterion was established: 3σ ‹ 300 arb. units.

At present, we have developed a program that automatically processes monthly billing records and prints out telephone numbers with a range spread of more than 300 units.

This processing of the first 400 CDMA subscribers revealed 20% of mobile and multi-site phones. Letters were sent to these subscribers with a proposal to stop using CDMA phones in violation of the Rules of Use and the provisions of the Agreement. Almost everyone using the phone at multiple locations has registered their second/third location. Some "mobile workers" have stopped carrying phones in the car, while work continues with the rest.

Along the way, several interesting facts emerged:

For some subscribers, the range distribution function showed the phone to work at two points. It turned out that the phone was operated only at one point, but it works on the built-in antenna and for some external reason switches to another base station, the quality of work is satisfactory. The installation of external antennas "tied" the phone to the selected base stations and improved the quality of communication to excellent;

Several subscribers constantly complained about poor call quality; it turned out that they use the phone in a mobile version. warning letters were sent to them. The complaints have stopped!

So what can be done to end the mobile use of fixed phones? Technical and administrative measures were considered.

technical measures. Linking the phone to the working sector is the most effective technical solution, although it is not 100% effective. Unfortunately, this is not possible with a Qualcomm controller. Probably, such a task was not originally set. In addition, if a sector fails, all its subscribers will be lost, although in today's situation many of them remain operational, as they switch to reflected signals from other sectors.

The use of concentrators. This will completely solve the problem of mobility, but there are several deterrent reasons:

There are still no certified CDMA hubs. The Qualcomm QCT-8000 hub has only recently passed certification testing;

The concentrator is most applicable to newly built facilities, when it is planned in advance in the project of a large residential building, office or industrial building. In the existing infrastructure of a city or village, the use of a concentrator does not solve the problem of the "last mile", reducing it only to the level of the last hundreds of meters;

Wealthy buyers, as a rule, are big individualists and perfectly understand all the advantages of a personal radiotelephone. It is impossible to drive them into a radiotelephone "communal apartment".

Sale of phones without battery power supply.

In many situations, this is unacceptable, since communication is especially needed during a power outage. And there will always be craftsmen who will connect the phone to the car network.

administrative measures.

Such measures can be:

Warning about violation of the Rules and provisions of the Agreement and a proposal to issue a second / third working point;

Disabling a malicious "mobile phone" for a systematic violation of the Terms and Conditions of the Agreement, but in this case real income is lost and a difficult legal situation may arise;

Assignment of a "mobile" tariff, i.e. actual recognition of mobility and deviation from the decisions of the State Committee for Communications.

Conclusion:

Today, we do not have a reliable technical means to prohibit the mobile use of fixed telephones. You can only identify them and warn subscribers about a possible disconnection. However, disconnection not only creates a difficult legal situation, but also leads to the loss of part of the income, which is unacceptable in today's situation, when there is a struggle to attract and retain each subscriber. This uncertain situation with fixed mobile operation can continue for quite a long time, at least as long as there is a margin of capacity.

What's next? Only one thing can be said with certainty - the number of subscribers using a fixed telephone in a mobile version, in the back seat of a car, is steadily increasing. We learn this by analyzing new reports from the mobility program every month. In addition, subscribers have already stopped hiding and directly ask: "Can I ride with him?" "No," we say, and they, nodding their heads in understanding, leave!

There are two ways out of this situation: 1. Categorically ban mobile use and require operators to disconnect all mobile subscribers and thereby "throw out the baby with the water", because. practically close the CDMA standard in Russia. 2. Allow the mobility of CDMA subscribers, legalizing the introduction of "mobile" traffic and introducing competition into a civilized course.

The sale of portable phones with a reasonable price of mobile traffic, subject to limited mobility within one controller, can attract additional subscribers and significantly increase the income of CDMA operators, among which more than 30% are representatives of telecommunications.

Problems.

The problems that should be paid attention to are well known to the absolute majority of operators, however, we are looking for ways to solve these problems alone and often find not the best and cheapest ones. These problems do not allow the operator to fully use CDMA to solve technological and economic problems. Such tasks can only be solved collectively, while all participants must be aware that not only can and should they benefit from the association, but they will also have to sacrifice part of their interests.

Works on registration of documents in state organizations.

Works on design, installation and commissioning of radiotelephone systems have shown that design work in the state bodies of the Russian Federation takes 5-6 times more time than delivery, installation and commissioning taken together.

frequency resource.

Today, this problem is especially urgent, and not only because the Russian frequency distribution is very different from world principles. Today CDMA operates in the 800 MHz spectrum, occupying the 1.23 MHz frequency band. Science says that the change of generations of equipment and the transition to broadband and high-speed technologies of the 3rd generation will require expanding the spectrum by 10-15 times. The operator should already know today what time frame he needs to do, what he needs to do so that his business is not intercepted by others.

GPS - a necessary tool for the functioning of the system.

Adjustment, synchronization and maintenance of the CDMA network in an optimal state is carried out according to the standard scheme using satellite systems such as GPS. The whole world uses only these systems. However, operators learn about the difficulties of using them in Russia after the fact, when the equipment has already been purchased. When moving to the 3rd generation, new problems are added, when the place in space, the speed and direction of movement of the terminal will be fixed up to a meter. Science, an association, a holding must anticipate such phenomena, suggest to the operator what he should work on legally and economically. The State Committee for Telecommunications should form a legal framework in advance.

State and problems.

The solution of a number of problems is impossible without the participation of the State Committee for Telecommunications and other state bodies. It is necessary to solve a number of direct prohibitions and problems that cause economic damage to operators and the state, and prevent the consumer from using all the possibilities of CDMA systems.

Allowing at least limited mobility and intra-region inter-controller communication with two or more controllers will greatly increase the attractiveness of the system.

Coordination of the transition to 3rd generation systems, when operators operating in the GSM, AMPS and CDMA standards will be forced to unite on a single technological platform, should be carried out under the auspices of the State Committee for Telecommunications.

These are the problems that we face at the current stage of the implementation of this technology.

List of used literature:

1 Avdeeva L.V. The introduction of radiotelephone systems in Russia

CDMA communications: history and problems // Mobile systems.

Special issue according to the CDMA standard. - M., 1998. - 30-34s.

2 Wireless subscriber line access. Volume 1. Handbook of mobile terrestrial communications. - M., 1997. - p.346.

3 Varakin L.E. Theory of signal systems. - M., 1978. - p.304.

4 Varakin L.E. Communication systems with noise-like signals. - M., 1985. - p.384

6 Gromakov Yu.A. Digital cellular mobile radio communication systems with code division of channels. - M., 1996. - 49s.

7 Dixon R.K. broadband systems. - M., 1979. - p.304

8 Pyshkin I.M., Dezhurny I.I. Mobile radio communication systems. - M., 1986. - p.328.

9 Tuzov G.I. Statistical theory of reception of complex signals. - M., 1987. - p.400

10 Tuzov G.I., Sivov V.A. Noise immunity of radio systems with complex signals. - M., 1985. - p.265.