Cellular radio system and its base station equipment

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a cellular wireless system such as an automobile / mobile phone system, and particularly relates to a system that employs, for example, Code division multiple access (CDMA) as an access method between a base station and a mobile station device.

【0002】

[Conventional technology]

In recent years, as one of the wireless communication methods applied to mobile communication systems, a spread spectrum communication method that is resistant to interference and interference has attracted attention. In a wireless communication system using the spectrum diffusion communication method, for example, in a device on the transmitting side, digitized voice data or image data is modulated by a digital modulation method such as PSK or FSK modulation method, and then this modulation is performed. The transmitted data is converted into a wideband baseband signal using a diffusion code such as a pseudo random noise code (PN code), and then converted into a radio frequency signal for transmission. On the other hand, in the receiving device, the received radio frequency signal is despread using the same spreading code used in the transmitting device, and then a digital demodulation method such as PSK or FSK demodulation method is used. It is configured to perform digital demodulation and reproduce the received data.

【0003】

The CDMA system is an application of such a spread spectrum communication system, and the channel separation between each communication is ensured by assigning different diffusion codes to the wireless communication between each mobile station and the base station. It is a thing.

【0004】

FIG. 11 is a schematic configuration diagram showing an example of a CDMA cellular radio system. In the figure, a plurality of base stations BS1 to BSn are distributed and arranged in the service area, and these base stations BS1 to BSn are connected to the control station CS via the wired lines L1 to Ln, respectively, and the control stations are connected to the control station CS. It is further connected to the wired communication network NW from CS. Further, the base stations BS1 to BSn each form radio zones Z1 to Zn called cells, and mobile stations MS1 to MSm each form a radio path with the base station of the cell in which the own station exists by the above CDMA method. Be connected.

【0005】

By the way, in this type of system, when mobile stations MS1 to MSm move between cells while communicating, so-called handoff is performed in which the base station to which the wireless path is connected is switched. There are two types of handoffs: soft handoffs and hard handoffs.

【0006】

First, soft handoff is a method peculiar to CDMA cellular radio systems. That is, when performing a handoff, the mobile station simultaneously forms a wireless path between its own station and the base station from which the handoff is performed, and between the own station and the base station to which the handoff is performed, and via these wireless paths. Path diversity synthesis is performed based on the received signals. After that, among the paths for which path diversity synthesis is being performed, the connection destination base station is switched by cutting the path in which the received electric field strength of the pilot channel becomes smaller than the threshold value for a certain period of time or more. In this way, soft handoff has the advantage that one of the two paths is always connected to the base station at the time of handoff and the path is not disconnected, so smooth switching can be performed without causing a momentary interruption of voice. There is.

【0007】

However, in order to perform soft handoff, it is a condition that the handoff source base station and the handoff destination base station use the same radio frequency. Therefore, for example, as shown in FIG. 11, in a system in which different radio frequencies f1, f2, and f3 are assigned to a plurality of base station groups BSa, BSb, and BSc, the mobile station MSi is transmitted from the cell of the base station group BSa. Soft handoff cannot be performed when moving to a cell of another base station group BSb or BSc.

【0008】

On the other hand, the hard handoff is mainly performed when the frequencies used by the handoff source base station and the handoff destination base station are different as described above. That is, when it becomes necessary to change the radio frequency used by the mobile station during handoff, the base station sends a message instructing the mobile station to perform handoff. Upon receiving this message, the mobile station suspends transmission / reception, forms a newly assigned radio path from the base station with the base station, and resumes transmission / reception using the path after the formation of this radio path. .. That is, at the time of hard handoff, it is necessary to temporarily disconnect the radio path in order to switch the radio frequency and re-form the radio path with the new radio frequency.

【0009】

However, in order to form a radio path between the mobile station and the base station, the mobile station first captures the pilot channel transmitted by the base station and establishes PN code synchronization. Then, after the establishment of this PN code synchronization, the base station transmits synchronization information and control information to the mobile station through the sink channel and the paging channel, whereas the mobile station transmits a message to the base station through the access channel. By exchanging and receiving the above signals, a vacant downlink traffic channel is assigned from the base station to the mobile station, and when the mobile station can receive a good signal continuously for a plurality of frames by this downlink traffic channel, the base station and the mobile station thereafter. It will be in a communication state with.

【0010】

For this reason, it takes a relatively long time to re-form the wireless path at the time of handoff, and as a result, the call voice is interrupted or noise is generated in the process of handoff, which causes deterioration of call quality. In addition, problems such as interruption of the call due to the failure of the handoff may occur.

【0011】

[Problems to be Solved by the Invention]

As described above, in the conventional system, there is no choice but to rely on hard handoff, which causes interruption of call voice and noise in the process of handoff, which causes deterioration of call quality, and call due to failure of handoff. Problems such as interruptions may occur.

【0012】

The present invention has been made by paying attention to the above circumstances, and an object of the present invention is to enable inter-cell handoff by soft handoff, thereby improving communication quality by preventing communication interruption or the like. In addition, it prevents traffic from concentrating on a specific radio frequency, so that when the above soft handoff is attempted, the problem that the soft handoff cannot be performed due to insufficient free traffic channels does not occur. The purpose of the present invention is to provide a cellular radio system and its base station apparatus capable of increasing the completion rate of soft handoff.

【0013】

[Means for solving problems]

In order to achieve the above object, the cellular radio system of the present invention relates to a mobile station in which each of a plurality of base stations has at least one common radio frequency and communicates with the base station by the first radio path. When it becomes necessary to perform a handoff, the handoff source base station sends a handoff request including information indicating the radio frequency of the first radio path to the handoff destination base station. Then, in the handoff destination base station, the second radio path using the same radio frequency as the radio frequency of the first radio path notified together with the handoff request from the handoff source base station is set as the mobile station to be handed off. Form between. In the mobile station to be handed off, the reception quality of both radio paths is monitored while communicating using the first radio path and the second radio path at the same time, and one of these radio paths is used. When the reception quality drops below a predetermined quality, the wireless path is disconnected.

【0014】

Further, the base station device of the present invention has the same radio frequency as the radio frequency commonly possessed by all the base station devices in the system, and handoff is performed for the mobile station connected via the first radio path. When it becomes necessary to send a handoff request including information notifying the radio frequency of the first radio path to the base station to be handed off, and a handoff request is sent from the base station of the handoff source. , A second radio path using the same radio frequency as the radio frequency of the first radio path notified together with this handoff request is formed between the mobile station to be handoff.

【0015】

As a result, according to the cellular radio system of the present invention and its base station apparatus, all base stations in the system have a common radio frequency, so that no matter which cell the mobile station moves to, the destination It is possible to form a second radio path having the same radio frequency as the first radio path before movement by using the common radio frequency with the base station. That is, it is possible to perform a soft handoff. Therefore, the call voice is not interrupted or noise is not generated in the handoff process, which makes it possible to maintain high call quality.

【0016】

Further, the cellular radio system and the base station apparatus of the present invention monitor the traffic of each of the plurality of base stations for each of the plurality of radio frequencies possessed, and compare the detection result of the traffic with the threshold value. If there is a radio frequency whose traffic exceeds the threshold, the radio path of the mobile station communicating using that radio frequency is changed to the radio path of another radio frequency whose traffic does not exceed the threshold. I am trying to perform a hard handoff to switch.

【0017】

Therefore, according to the present invention, when a large number of communications are concentrated on a specific radio frequency, some of these communications are automatically handed off to other radio frequencies with low traffic. Therefore, it is possible to average the traffic of each radio frequency and secure an empty traffic channel, which makes it possible to execute the soft handoff associated with the cell-to-cell movement described above with a high probability. ..

【0018】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic configuration diagram showing an embodiment of a cellular wireless system according to the present invention. In the figure, the same functional parts as those in FIG. 11 are designated by the same reference numerals.

【0019】

In the cellular radio system of this embodiment, a plurality of radio frequencies (carriers) f1 to fk common to all base stations BS1 to BSn in the system are assigned. Each of these carriers f1 to fk is a downlink carrier fb1 to fbk used to transmit a signal from the base station to the mobile station, and an uplink carrier fm1 to fmk used to transmit a signal from the mobile station to the base station. Consists of a pair with.

【0020】

Each base station BS1 to BSn transmits a pilot channel, a sink channel, a paging channel, and a downlink traffic channel in each of the downlink carriers fb1 to fbk, respectively. On the other hand, the mobile station MS transmits an access channel and an uplink traffic channel in each of the uplink carriers fm1 to fmk, respectively.

【0021】

FIG. 3 is a circuit block diagram showing the configuration of the mobile station MS. In the figure, the speaker's transmitted voice signal output from the microphone of the microphone / speaker 10 is converted into a digital signal by the DA / AD converter 11 and then converted by the vocoder (voice encoder / decoder) 12. It is encoded and input to the microprocessor 13. In the microprocessor 13, a control signal or the like is added to the transmitted voice signal as needed, and transmission data is created by this.

【0022】

This transmission data is encoded by the convolutional encoder 15 after the error detection code and the error correction code are added by the data generation circuit 14, and further processed for interleaving by the interleaving circuit 16. Then, in the spread spectrum device 17, the spread spectrum is modulated by the PN code. This spread spectrum transmitted signal is converted into an analog signal by the DA converter 19 after the unnecessary frequency components are removed by the digital filter 18, and then converted into a predetermined carrier frequency by the analog front end 20. At the same time, after the power is amplified to a predetermined transmission power, the signal is transmitted from the antenna 21 to a base station (not shown).

【0023】

On the other hand, the radio frequency signal received by the antenna 21 is low-noise amplified by the analog front end 20, frequency-converted to the baseband frequency, and further converted into a digital signal by the AD converter 22 at a predetermined sampling cycle. After that, it is input to the signal search circuit 23, the automatic gain control (AGC) circuit 24, and the three finger circuits 25, 26, 27, respectively.

【0024】

Of these, the signal search circuit 23 performs a PN search on the pilot signal broadcast from the base station on the pilot channel, and includes an initial capture unit, a clock tracking unit, and a data demodulation unit. The power control data obtained by this PN search operation is taken into the microprocessor 13.

【0025】

The finger circuits 25, 26, and 27 each include an initial capture unit, a clock tracking unit, and a data demodulation unit, as in the signal search circuit 23, respectively, and depending on the PN synchronization information captured by the signal search circuit 23, Spread spectrum and demodulate the transmission data transmitted from the base station. The reason why the three finger circuits are provided is to receive the multipath reception signal at a high SN ratio by using the time diversity effect and to perform the soft handoff described in detail later.

【0026】

The symbols demodulated by the finger circuits 25, 26, and 27 are input to the symbol synthesizer 28 together with the synchronization information, and are synthesized with each other. Then, the synthesized demodulation symbol is input to the deinterleaved circuit 29 together with the timing information, deinterleaved here, and then input to the Viterbi decoder 30 where the Viterbi decoding is performed. Further, the received data that has been viterbi-decoded is input to the microprocessor 13 after being subjected to error-correcting-decoding processing by the error-correcting circuit 31, and the audio data and the control data are separated by the microprocessor 13. Of these, the voice data is voice-decoded by the vocoder 12, converted into an analog signal by the DA / AD converter 11, and then supplied to the speaker 10 for loudspeaker output from the speaker 10.

【0027】

The keypad / display 32 inputs dial data, control data, and the like and displays various information related to the usage state of the mobile station, and its operation is controlled by the microprocessor 13.

【0028】

Next, the handoff operation of the system configured as described above will be described. Here, a case where the mobile station MSj moves from cell Z1 to cell Z2 will be described as an example.

【0029】

First, the operation when the power is turned on in the mobile station MSj will be described. FIG. 4 is a flowchart showing the operation procedure. When the power is turned on, the mobile station first performs the power sense of each downlink carrier fb1 to fbk arriving from the base station in step 4a, and from the result of the power sense, the downlink carrier with the minimum received power level and this downlink in step 4b. Select an upstream carrier that is paired with the carrier. Now, for example, as a result of the power sense of the downlink carrier, it is assumed that the reception power level of the downlink carrier fbi is the minimum as shown in FIG. Then, in this case, the downlink carrier fbi and the uplink carrier fmi paired with the downlink carrier fbi are selected as carriers to be used. Here, the reason for selecting the carrier with the minimum received power level is that in the CDMA system, the power of the received signal other than that addressed to the own station affects it as noise, so if the carrier with the minimum received power is selected, interference will occur. This is because the probability of being able to communicate without it is the highest.

【0030】

Then, when the carrier to be used is selected, the mobile station MSj subsequently captures the pilot channel of the downlink carrier fbi in step 4c. This pilot channel capture operation is performed in the signal search circuit 23. When the acquisition of the pilot channel is completed, the base station BS1 transmits a message signal to the mobile station MSj using the sync channel, paging channel and downlink traffic channel of the downlink carrier fbi, while the mobile station MSj steps. In 4, the message signal is transmitted using the access channel and the uplink traffic channel of the uplink carrier fmi, whereby the first radio path is formed between the base station BS1 and the mobile station MSj. After that, the mobile station MSj can communicate with the base station BS1 via the first radio path described above.

【0031】

During this communication, the mobile station MSj measures the multipath pilot channel intensity arriving from the surrounding base stations in the downlink carrier fbi. Then, the one with the highest reception power level is selected from the observed pilot channels, and another fin receives the selected pilot channel by a circuit to perform diffusion code synchronization. Then, when the diffusion code synchronization is established, the signals received by the two finger circuits thereafter are combined by the symbol synthesizer 28 to reproduce the received signal. That is, the reception operation is performed by path diversity synthesis.

【0032】

Next, the soft handoff operation associated with the inter-cell movement of the mobile station MSj during the above communication will be described. 6 and 7 are flowcharts showing control procedures and control contents of mobile station MSj and base stations BS1 and BS2 for explaining their operation, respectively.

【0033】

It is assumed that the mobile station MSj moves from the position in cell Z1 shown in a to the boundary position of cells Z1 and Z2 shown in b as shown in FIG. 2, for example, during the wireless communication. Then, in the mobile station MSj, the reception level of the pilot channel arriving from the base station BS2 becomes high. The mobile station MSj detects the received power level of the pilot channel in step 6a during wireless communication and compares the detected value with a plurality of threshold values preset in step 6b. Then, each time the reception power level of the pilot channel exceeds these threshold values, the spread code phase and the reception power level of the pilot channel are reported to the base station BS1 in communication in step 6c.

【0034】

During wireless communication, base station BS1 monitors the arrival of reception level report messages from mobile stations and the arrival of soft handoff requests from other base stations in steps 7a and 7b, respectively. Then, when a reception level report message arrives from the mobile station MSj in this state, it is determined in step 7c whether or not a soft handoff is necessary from the reported reception level. When it is determined that a soft handoff is necessary, the base station BS2 to be the handoff destination is determined in step 7d, and the soft handoff request is transferred to this base station BS2 via the control station CS. Information representing the carrier in use is inserted in this handoff request.

【0035】

When the above handoff request arrives, the base station BS2 shifts from step 7c to step 7e, where the reception level of the uplink traffic channel from the mobile station MSj is measured. As a result of this measurement, if it is determined that a handoff is necessary, the mobile station MSj is instructed to perform a soft handoff in step 7f. Then, in step 7g, an operation for forming a second radio path with the same carrier fi as the first radio path being formed with the mobile station MSj and the handoff source base station BS1 is executed. ..

【0036】

On the other hand, upon receiving the above soft handoff instruction, the mobile station MSj shifts from step 6d to step 6e, where an operation for forming a second radio path by the carrier fi is performed. Then, when a second radio path is formed between the base station BS2 and the mobile station MSj at the handoff destination, the mobile station MSj uses the uplink traffic channel to the base stations BS1 and BS2 in step 6f. Report the completion of the formation of the second radio path. The base stations BS1 and BS2 receive and confirm the wireless path formation completion notification from the mobile station MSj in step 7h.

【0037】

Thus, in the mobile station MSj thereafter, the path diversity is based on the simultaneous use of the first radio path formed between the base station BS1 and the second radio path newly formed between the base station BS2. The reception operation is performed.

【0038】

During reception by the above path diversity, the mobile station MSj monitors the reception power level of the pilot channels of the first radio path and the second radio path in step 6g, respectively. In this state, it is assumed that the mobile station MSj further moves from the position near the cell boundary shown in (b) of FIG. 2 to the position in cell Z2 shown in (c). Then, the reception power level of the pilot channel of the first radio path is continuously lowered for a certain period of time from the preset threshold value. Therefore, the mobile station MSj reports to that effect to the base stations BS1 and BS2 in step 6h.

【0039】

Upon receiving this report, the base stations BS1 and BS2 move from step 7i to step 7j, and instruct the mobile station MSj to disconnect the first radio path on the side where the reception level of the pilot channel has decreased. To the mobile station MSj. Upon receiving this disconnection instruction, the mobile station MSj executes a process for disconnecting the designated first radio path in step 6j. Then, when the disconnection is completed, the fact is reported to the base station BS2. At this time, the base station BS1 also executes a process for disconnecting the first radio path to and from the mobile station MSj in step 7k. Thus, a soft handoff is performed when the mobile station MSj moves from cell Z1 of base station BS1 to cell Z2 of base station BS2.

【0040】

Next, the hard handoff operation to be performed when the traffic of a specific carrier increases will be described. 8 and 9 are flowcharts showing control procedures and control contents of base stations and mobile stations for explaining their operations, respectively.

【0041】

Each base station BS1 to BSn monitors the number of traffic channels used for each downlink carrier in step 8a during its operation, that is, the traffic of each downlink carrier. Then, when a carrier whose number of traffic channels used exceeds a preset threshold value is found, a hard handoff is instructed to the mobile station communicating using this carrier. The threshold value for monitoring traffic is set to a value about 20 to 30% lower than the limit value of the traffic channel with a margin.

【0042】

Now, in the base station BS1, for example, as shown in FIG. 10, it is assumed that the number of traffic channels used by the downlink carrier fb3 exceeds the threshold value. Then, the base station BS1 shifts from step 8b to step 8c, where any mobile station among the plurality of mobile stations communicating using the downlink carrier fb3 is hardened via the downlink traffic channel. Send handoff instructions. At this time, the carrier information of the handoff destination is also notified together with the instruction of the hard handoff.

【0043】

On the other hand, the mobile station monitors the arrival of a hard handoff instruction from the base station in step 9a during communication, and if a hard handoff instruction arrives from the base station BS1 in this state, the process proceeds to step 9b. Then, the pilot channel of the designated carrier is acquired according to the carrier information of the handoff destination notified from the base station BS1. Then, when the acquisition of the pilot channel is completed, the access channel is used in step 9c to transmit a traffic channel allocation request to the base station BS1.

【0044】

When a channel allocation request arrives from the mobile station, the base station BS1 moves from step 8d to step 8e, selects a free traffic channel here, and uses the allocation information of this free traffic channel as a paging channel in step 8f. And sends it to the mobile station that requested the channel allocation.

【0045】

When this channel allocation information is received, the mobile station transmits a preamble signal using the upstream traffic channel of the carrier specified in step 9e. In step 8g, the base station BS1 receives the preamble signal of the upstream traffic channel arriving from the mobile station and performs the capture operation of the traffic channel. The capture report message is sent, and then communication with the mobile station is continued using the traffic channel of the newly assigned carrier. On the other hand, when the mobile station receives the capture report message in step 9f, it continues communication using the traffic channel of the newly assigned carrier.

【0046】

Thus, a hard handoff to other carriers is made when the number of traffic channels used by a particular carrier increases above the threshold. The number of mobile stations that perform hard handoff is determined according to the number of traffic channels used by the carrier.

【0047】

As described above, in this embodiment, all the base stations BS1 to BSn in the system have a common carrier, and the mobile station communicating using the first wireless path moves to the cell. In this case, the soft handoff request is transferred from the handoff source base station to the handoff destination base station, and the handoff destination base station is connected to the handoff target mobile station in accordance with this request. Form a second radio path using the same carrier as. Then, after that, the mobile station monitors the reception power level of the first and second radio paths while performing the reception operation by the path diversity, and when the reception level of one path drops below the threshold value, this is performed. I try to disconnect the wireless path.

【0048】

Therefore, according to this embodiment, when the mobile station moves to any cell in the system, it is possible to perform a soft handoff using the same carrier, which causes a momentary interruption of voice or switching noise. It is possible to always perform a smooth handoff without causing problems such as occurrence.

【0049】

Further, in this embodiment, the number of used traffic channels for each carrier is monitored in each base station BS1 to BSn, and when a carrier whose number of used traffic channels exceeds the threshold value appears, this carrier is used. Then, some mobile stations out of a plurality of mobile stations in communication perform a hard handoff to switch the wireless path in use to a wireless path using another carrier.

【0050】

Therefore, it is possible to prevent the concentration of traffic on a specific carrier and average the traffic between carriers, which makes it possible to perform a soft handoff due to lack of free traffic channels. It is possible to prevent problems such as the inability to perform handoffs, which can increase the completion rate of soft handoffs.

【0051】

In addition, there is a concern that the communication quality will deteriorate due to the momentary interruption of the call voice and the generation of noise by performing the hard handoff, but this hard handoff is different from the handoff that accompanies the movement between cells, and the SN of the received signal in the cell. It is performed under a high ratio condition, and the diffusion sequence offset used by the carrier before the handoff and the carrier after the handoff is the same, and the diffusion code synchronization can be relatively easily taken. Therefore, the probability of failure of the hard handoff is low, and the time required for a series of operations is extremely short, so that the deterioration of communication quality is extremely small.

【0052】

The present invention is not limited to the above-described embodiment, and the gist of the present invention is described with respect to the soft handoff control procedure and control content, and the hard handoff control procedure and control content for traffic averaging. It can be modified in various ways within a range that does not deviate.

【0053】

[Effect of the invention]

As described in detail above, in the cellular wireless communication system of the present invention and its base station apparatus, at least one common radio frequency is possessed by each of a plurality of base stations, and when a call related to a mobile station occurs, the present invention is concerned. A first radio path is formed between the mobile station and the base station of the cell in which the mobile station resides using the common radio frequency described above. Then, when it becomes necessary to perform a handoff for a mobile station communicating via this first wireless path, the radio frequency of the first wireless path is transmitted from the base station of the handoff source to the base station of the handoff destination. A second radio path using the same radio frequency as the radio frequency of the first radio path notified by the handoff source base station together with the handoff request is transmitted at the handoff destination base station by transmitting the handoff request including the information to be represented. Is formed with the mobile station to be handed off. In this state, the mobile station to be handed off monitors the reception quality of both radio paths while communicating using the first radio path and the second radio path at the same time, and one of these radio paths. The wireless path is disconnected when the reception quality of the path drops below a predetermined quality. Further, each of the plurality of base stations monitors its traffic for each of the plurality of radio frequencies possessed. Then, the traffic detected by this monitoring is compared with the threshold value, and if there is a first radio frequency in which the traffic exceeds the threshold value, the movement during communication using the first radio frequency is used. Perform a hard handoff to switch the station's radio path to a second radio frequency path where traffic does not exceed the above threshold and the spread code sequence offset is the same as the first radio frequency. ing.

【0054】

Therefore, according to the present invention, cell-to-cell handoff can be performed by soft handoff, whereby communication quality can be improved without interruption of communication, and traffic to a specific radio frequency can be achieved. It is possible to prevent the concentration of the above and prevent the problem that the soft handoff cannot be performed due to insufficient free traffic channel when trying to perform the above soft handoff. It is possible to provide a cellular radio system and its base station apparatus which have made it possible to increase the completion rate of the above.

[Simple explanation of drawings]

[Figure 1]

The schematic block diagram which shows one Embodiment of the CDMA cellular radio system which concerns on this invention.

[Figure 2]

FIG. 5 is an enlarged view showing a part of the system shown in FIG. 1 for explaining the operation of one embodiment of the present invention.

[Fig. 3]

A circuit block diagram showing a mobile station configuration in the system shown in FIGS. 1 and 2.

[Fig. 4]

The flowchart which shows the operation procedure at the time of power-on of the mobile station shown in FIG.

[Fig. 5]

The figure which shows an example of the perspective result of each downlink carrier.

[Fig. 6]

A flowchart showing a control procedure of a mobile station related to a soft handoff and the control content thereof.

[Fig. 7]

A flowchart showing a control procedure of a base station related to a soft handoff and the control contents thereof.

[Fig. 8]

A flowchart showing a base station control procedure and its control contents related to a hard handoff.

[Fig. 9]

A flowchart showing a control procedure and control contents of a mobile station related to a hard handoff.

[Fig. 10]

The figure which shows an example of the monitoring result of the number of traffic channels used for each carrier.

[Fig. 11]

The schematic which shows an example of the structure of the conventional CDMA cellular radio system.

[Explanation of symbols]

BS1 ~ BSn ... Base station Z1 ~ Zn ... cell CS ... control station NW ... Wired communication network MS1 ~ MSm ... Mobile station 10 ... Microphone / Speaker 11 ... DA / AD converter 12 ... Vocoder (voice coder / decoder) 13 ... microprocessor 14 ... Data generation circuit 15 ... Convolutional encoder 16 ... interleaved circuit 17 ... Spread spectrum 18 ... Digital filter 19 ... DA converter 20 ... analog front end 21 ... Antenna 22 ... AD converter 23 ... Signal search circuit 24 ... Automatic Gain Control (AGC) Circuit 25,26,27 ... Finger circuit 28 ... Symbol synthesizer 29 ... Deinterleaved circuit 30 ... Viterbi Decoder 31 ... Error correction circuit 32 ... Keypad / Display