JPH11331936A - Communication system for mobile object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economize power consumption by reproducing signals at a high transmission rate with fidelity when a communication environment is adverse and enabling the sufficient maintenance of sound quality even at a low transmission rate when the communication environment is satisfactory on the other hand. SOLUTION: At a base station 10, communication environment information such as traffic increase or mobile station position is collected. Based on this information, the base station 10 determines a communication mode. A mobile station 20 selects the transmission rate of the determined communication mode and performs transmission at that transmission rate. This transmission rate is dynamically switched and optimized corresponding to a change in the communication environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system which is widely used by mobile phones and the like.

[0002]

2. Description of the Related Art In a general communication system, an appropriate transmission rate is set according to the amount of information to be transmitted within a unit time. For example, in mobile communication mainly using voice, ADP
A scheme such as CM or sub-band ADPCM is adopted, but in the former scheme, a transmission rate of 32 kbps is set, and in the latter scheme, a transmission rate of 64 kbps is set.

[0003]

However, the above-mentioned prior art has the following problems to be solved.
For example, in order to improve sound quality in mobile communication mainly using voice, it is preferable to use a method in which the transmission rate is large and the number of bits of data to be transmitted per unit time is large. on the other hand,
A mobile station is usually driven by a charged battery. Therefore, in order to make the continuous usable time as long as possible, a method in which the transmission power is small is preferable. In this case, the lower the transmission rate, the more the transmission power for transmitting the same information can be saved.

In order to multiplex signals and increase the number of channels, the smaller the transmission rate of each mobile station is, the more multiplexing of communications becomes possible. Therefore, there is a demand for a system that allows many subscribers to communicate by performing communication at a transmission rate as low as possible without impairing the necessary sound quality and information amount regardless of the propagation state.

[0005]

The present invention employs the following structure to solve the above problems. <Configuration 1> A communication environment information collection unit that collects communication environment information for a mobile station that performs mobile communication, and a communication mode determination unit that determines a communication mode suitable for the communication environment based on the collected communication environment information. Selecting one of the communication modes from two or more communication modes prepared in advance,
A mobile communication system comprising: a transmission unit that executes communication by a mobile station.

<Configuration 2> When a mobile station communicates with another station through a base station, the base station includes a communication environment information collection unit for collecting communication environment information, and a communication environment information collection unit for collecting the communication environment information. A communication mode determining unit that determines a communication mode suitable for the communication environment; and a mode selection information transmitting unit that generates mode selection information for communication mode selection and transmits the generated mode selection information to the mobile station. The station selects one of two or more communication modes operating at different transmission rates prepared in advance at a predetermined timing, and selects one of the communication modes to perform communication by the mobile station. A mobile communication system, comprising: a transmitting unit that executes the mobile communication system.

<Structure 3> In the system described in Structure 1 or 2, the timing at which the transmission unit selects a new operation mode according to the mode selection information is determined for each transmission frame.
A mobile communication system for each transmission burst and / or for each call.

<Configuration 4> A mobile communication system according to configuration 1 or 2, wherein the mode selection information is included in header information of a transmission frame.

<Structure 5> A mobile communication system according to structure 1 or 2, wherein the mode selection information is included in prefix information or ending information of a transmission burst.

<Configuration 6> A mobile communication system according to configuration 1 or 2, wherein the mode selection information is included in control information transmitted and received during call setup.

<Structure 7> A mobile communication system according to structure 1 or 2, wherein the mode selection information is inputted by a control switch of the mobile station.

<Configuration 8> A mobile communication system according to configuration 2, wherein the environment information collection unit of the base station collects environment information from the mobile station.

<Configuration 9> In the system described in Configuration 2, the mode selection information transmitting section of the base station transmits the mode selection information to the mobile station based on the environment information of the moving mobile station based on the destination information. A mobile communication system, characterized by transmitting:

<Structure 10> In the system described in Structure 2, the mode selection information transmitting unit of the base station transmits the specified specific information even when a plurality of mobile stations are performing communication in the same environment. A mobile communication system for transmitting mode selection information only to a mobile station.

<Configuration 11> A mobile station performing mobile communication includes:
A communication environment information collection unit that collects communication environment information, a speech coding system determination unit that determines a speech coding system suitable for the communication environment based on the collected communication environment information, and a determined speech coding system. To generate a coding scheme selection information for performing a predetermined coding at a predetermined timing from two or more kinds of coding schemes operating at different transmission rates prepared in advance. A mobile communication system comprising: a transmission unit that selects a system and executes communication by the mobile station.

<Configuration 12> When the mobile station communicates with another station through the base station, the base station includes a communication environment information collection unit that collects communication environment information, and a communication environment information collection unit that collects the communication environment information. A voice coding scheme determining unit that determines a voice coding scheme suitable for the communication environment, and generates coding scheme selection information for selecting the determined voice coding scheme, and transmits the generated coding scheme selection information to the mobile station. An encoding method selection information transmitting unit is provided, and the mobile station has, at a predetermined timing set in advance, from two or more types of voice encoding methods operating at different transmission rates prepared in advance,
A mobile communication system, comprising: a transmission unit that selects a corresponding voice coding method and executes communication by a mobile station.

<Structure 13> In the system according to structure 11 or 12, the timing at which the transmitting unit selects a new speech coding method according to the coding method selection information is determined for each transmission frame, each transmission burst, and / or A mobile communication system for each call.

<Structure 14> A mobile communication system according to structure 11 or 12, wherein the coding scheme selection information is included in header information of a transmission frame.

<Configuration 15> A mobile communication system according to configuration 11 or 12, wherein the coding scheme selection information is included in the prefix information or the ending information of the transmission burst.

<Structure 16> A mobile communication system according to structure 11 or 12, wherein the coding method selection information is included in control information transmitted and received during call setup.

<Structure 17> A mobile communication system according to structure 11 or 12, wherein the coding system selection information is inputted by a control switch of the mobile station.

<Structure 18> A mobile communication system according to Structure 12, wherein the environment information collection unit of the base station collects environment information from the mobile station.

<Configuration 19> In the system according to Configuration 12, the coding scheme selection information transmitting unit of the base station transmits a code to the mobile station based on environment information of the moving mobile station based on the destination environment information. A mobile communication system for transmitting encryption scheme selection information.

<Structure 20> In the system described in Structure 12, the coding scheme selection information transmitting section of the base station is configured to transmit the coding scheme selection information in advance even when a plurality of mobile stations are performing communication in the same environment. A mobile communication system for transmitting coding scheme selection information only to a specific mobile station.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below using specific examples. <First Embodiment> FIG. 1 is a block diagram showing a mobile communication system according to a first embodiment. In the figure, the base station 10
Controls wireless connection between the mobile station 20 and a communication line (not shown) when many mobile stations 20 communicate with another mobile station (not shown) or a fixed station. In a general mobile phone system, a number of base stations are provided, and each base station communicates with a mobile station that moves within a predetermined area.

Further, when performing wireless communication, various noises are mixed in when a signal propagates in the air. In order to remove such noise and faithfully reproduce the original signal, various types of error correction information are included in the transmission signal. If the transmission rate is high, more error correction information can be included in the transmission signal. Therefore, even when the communication environment is relatively poor, a high-quality call can be made.

Here, it is assumed that the amount of information such as error correction information is reduced and transmission is performed at a low transmission rate in order to save transmission power. In this case, when the communication environment is relatively good, information with few errors reaches the receiving side, so that a substantially high-quality signal can be reproduced. However, when the communication environment is poor, an error exceeding the error correction capability occurs, and it may be impossible to perform a good signal reproduction on the receiving side.

Therefore, in the present invention, information on the communication environment is collected, and the transmission rate is dynamically switched according to the communication environment. For this purpose, the base station 10 includes a communication environment information collection unit 1, a communication mode determination unit 2, a mode selection information transmission unit 3, and the like. With such a configuration, various types of communication environment information 4 are collected.

On the other hand, the mobile station 20 includes, for example, a microphone 21, an A / D converter 22, a voice coding unit 23, a blocking unit 24, a convolution coding unit 25, an interleave processing unit 26, It comprises a header adding unit 27, a spreading unit 28, a power control unit 29 and the like. These block configurations are the same as those provided in a conventional mobile phone.

That is, the voice of the speaker is input from the microphone 21 and converted into a digital signal by the A / D converter 22. The audio encoding unit 23 converts the audio signal into a predetermined code, and the blocking unit 24 is a unit that blocks the audio signal for each transmission block. Also, the convolutional encoder 2
Reference numeral 5 denotes a unit for performing processing for adding error correction information to each of the divided audio signals, and an interleave processing unit 26 rearranges data to be transmitted.

The header adding section 27 adds predetermined header information to each frame of data to be transmitted.
Reference numeral 8 denotes a portion for performing a predetermined spreading process when the code spreading method is adopted. The power control unit 29 is a unit that receives the output of the spreading unit 28 and transmits the signal in the air with a predetermined power.

Here, a transmission rate instructing section 30 is provided so that the mobile station 20 can switch the transmission rate based on the mode selection information notified from the base station 10. Note that the block diagram in FIG. 1 is configured such that the mobile station 20 appropriately selects a communication mode based on mode selection information notified from the base station 10. However, the mobile station 20 may voluntarily collect the communication environment information 4 and switch the communication mode. For this purpose, for example, as shown in a dashed block in this figure, a communication environment information collection unit 31 and a communication mode determination unit 32
Should be provided.

FIG. 2 is a diagram illustrating the types of transmission rates. For example, as described above, the conventional ADPCM system has 32 bits, and the sub-band ADPCM system has 64 bits.
A transmission rate of bps is set. However, in practice, as shown in FIG. 2, in the ADPCM system, 16, 24, 32, and 40 kbps, the subband AD
In PCM, it is possible to set and control the transmission rate of 48, 56, 64 kpbs. In the present invention,
These transmission rates are dynamically selected according to the communication environment.

FIG. 3 shows an example of timing for mode selection. The switching of the transmission rate as described above is executed, for example, at the timing shown in FIG. (A) shows an operation mode selected for each frame. The transmission signal is divided into frames each having a predetermined length. If an operation mode according to the communication environment is selected for each frame, the communication quality, transmission power, and the like can be optimized.

In this example, the operation mode is dynamically switched to the operation mode M3 for the frame F1, the operation mode M7 for the frame F2, and the operation mode M2 for the frame F3.

FIG. 3B shows an example in which the operation mode is switched for each burst. A burst is a talk spurt from the beginning to the end. That is, a period from when a sound is emitted to when the sound stops sounding is called a burst, and switching control is facilitated by switching the operation mode for each burst. In addition, when the sound quality changes due to the switching, there is an effect that it is difficult to notice the change. A burst is composed of a plurality of frames.

(C) shows an example in which the operation mode is switched for each call. When a call is set and communication is started, the operation mode determined at the beginning is selected, and communication in the operation mode is performed. In this case, a certain mode is maintained until the call is disconnected. The method shown in (c) has the longest control interval.

Hereinafter, the operation of the system shown in FIG. 1 will be specifically described. First, the contents of the communication environment information shown in FIG. 1 will be described. FIG. 4 is an explanatory diagram of communication environment information collected by the base station. The communication environment information collected by the communication environment information collection unit 1 of the base station 10 shown in FIG. 1 has the contents shown in FIG. First, the base station controls the communication of all mobile stations within the area managed by the base station, so that it can detect wireless traffic.

Here, for example, the number of simultaneous users, the call loss rate,
Acquire information such as connection waiting time, BER, SIR, and the like. The more concurrent users, the more traffic. In such a case, the traffic is alleviated as the communication rate of each station is lower. Therefore, the communication mode is determined so that each mobile station takes the lowest possible communication rate.

Further, the position of the mobile station is detected to detect wireless traffic for each position. For example, the base station may divide an area managed by the base station into a plurality of sections, detect wireless traffic for each section, and move to a section having a large wireless traffic while the mobile station is moving from one position to another. If found, a decision is made to select a communication mode in a direction to lower the transmission rate.

Further, a report is received from the mobile station. The mobile station transmits various information to the base station during communication. Here, information such as the reception level of the mobile station, its level fluctuation, the signal error rate, the frequency characteristics of the transmission path, and the Doppler frequency generated when the mobile station is moving at high speed is reported from the mobile station to the base station. . The transmission rate is determined based on this information. For example, when the error rate is high, the transmission rate is increased to improve the communication quality and to maintain it. In the opposite case, the transmission rate is reduced so that communication can be performed with low power consumption as long as communication quality can be maintained.

The communication environment information collecting section 1 shown in FIG. 1 collects the above information, and the communication mode determining section 2 determines the communication mode based on the above judgment. The determination of the communication mode mainly consists in selecting a transmission rate. The selection range and selectable types of the transmission rate may be arbitrarily determined by the system. The output of the communication mode determination unit 2 is sent to the mode selection information transmission unit 3 and the mode selection information is transmitted to the mobile station 20.

In the mobile station 20, the transmission rate instructing unit 30 accepts the mode selection information, and outputs the speech encoding unit 23, the blocking unit 24, the convolutional encoding unit 25, the interleave processing unit 26, the header adding unit 27, and the spreading unit. 28, etc., to change the transmission rate. Thereby, the base station 10
Is selected, and transmission is performed at that transmission rate. As described above, the mobile station 20 itself can collect communication environment information and determine a communication mode.

FIG. 5 is an explanatory diagram of communication environment information collected by the mobile station. For example, the location where the mobile station is used has a significant effect on the communication environment. When the mobile station is used in a suburb, when it is used indoors, when it is used in a vehicle, etc., the usage environment is different. The mobile station is provided with a predetermined switch function so that the switch can be switched for each such use environment. When the user of the mobile station switches the switch, communication environment information can be taken into the mobile station.

Further, as another use environment, the reception level and its fluctuation, the error rate, the frequency characteristic of the transmission path, the Doppler frequency, and the like are measured in the same manner as reported to the base station described with reference to FIG. The communication mode is determined based on the result. Further, the use state can be taken as one of the communication environments. For example, if there is no sound for a certain time during a call,
The transmission rate can be made sufficiently low. Further, when the user requests a certain sound quality or more, control is required to forcibly increase the transmission rate.

FIG. 6 is a diagram for explaining a method of transmitting mode selection information from the base station to the mobile station. As described above, the base station 10 shown in FIG. 1 appropriately transmits the mode selection information to the mobile station 20 that makes a call in the area managed by itself. In this case, for example, when the wireless traffic suddenly increases, the mode selection information can be sent to all the mobile stations so as to lower the transmission rate. This can be realized by using a conventional control information broadcasting function.

On the other hand, mode selection information can be sent only to a specific mobile station. In the example shown in FIG. 6, for example, when the mobile stations 20-2 and 20-3 have been talking for a long time, the mobile stations 20-2 and 20-3 notify the mode selection information to reduce the transmission rate to these stations. Thereby, other mobile stations can be preferentially treated. In addition, for example, when a different charge is set or a different contract is made for each mobile station, the transmission rate is reduced earlier when communication traffic increases for a mobile station with a lower charge. To transmit the mode selection information.

In this way, the base station can notify any specific mobile station or all mobile stations of the mode selection information. For example, if it is assumed that if the transmission rate is reduced by about half of the number of mobile stations under management, the adverse effect due to the increase in communication traffic can be suppressed, it is assumed that about half of all the mobile stations are randomly selected. , And the mode selection information can be notified.

FIG. 7 is a diagram for explaining an example of the mode selection operation. When the mode selection information as described above is accepted by the transmission rate instruction unit 30 shown in FIG.
The operation mode is selected as shown in FIG. For example, in FIG. 7A, the mode selection information is included in the header information 41 located at the head of the frame. According to this mode selection information, the operation mode is set to, for example, M3 during the transmission of the frame.

When control is performed in burst units,
The mode selection information is included in the initial information 42A or the final information 42B. Referring to the prefix information, the burst following the prefix information 42A is selected in the corresponding operation mode M1. If the ending information 42B includes mode selection information, the operation mode of the next burst is set to, for example, M4 as shown in FIG. (C) of the figure shows the operation mode selection operation for each call, and the call setting control command 4
3 includes mode selection information. When the call setting is completed, a call is started in the corresponding operation mode M5.

(D) shows a case where the operation mode is switched from M2 to M5 by the activation switch 44 of the mobile station. This operation is usually performed before starting a call, or when moving from outdoors to indoors with a mobile station.

FIG. 8 is a diagram for explaining specific signal contents when the mode is changed. This figure specifically shows how to change the signal content when the operation mode is changed, for example, when the transmission rate is switched from a high state to a low state. For example, in the case where a stereo signal is being transmitted, if mode selection information for halving the transmission rate is accepted, switching is performed so that only one channel of the stereo signal is communicated. As a result, communication can be continued while maintaining the signal quality itself. Also, 8kb
The signal of the ps code is changed to 4 kbps.

Further, for example, when the communication environment is extremely good,
A part or all of the error correction signal is omitted. This enables communication without substantially lowering the signal quality. As a result, a sufficiently practical call can be made even when the transmission rate is lowered.

The above-described collection of communication environment information, determination of the communication mode, transmission of mode selection information, and transmission rate instruction based on the mode selection information are executed by a computer program that controls the base station and the mobile station. You. Therefore, the present invention can be implemented by incorporating a memory storing a control program into a corresponding portion of a base station or a mobile station, or by installing a program in a program memory from the outside. Also,
The transmission rate switching as described above may be performed separately for the uplink signal and the downlink signal, or may be controlled by exchanging information so that the uplink and the downlink have the same transmission rate.

<Effect of Specific Example 1> In the mobile communication system described above, the base station or the mobile station collects communication environment information and determines a communication mode according to the information. When the communication mode is determined, communication at the corresponding high transmission rate or low transmission rate is performed. Thereby, when there are many signal errors, communication is performed at a high transmission rate, and communication quality is maintained. On the other hand, when the communication environment is very good and error occurrence is small or traffic increases, the transmission rate is low. A communication mode is selected to suppress transmission power and enable multiplex communication.

<Specific Example 2> In the specific example 1, the transmission rate was dynamically switched according to the communication environment. In this specific example 2, the encoding system is dynamically switched instead of the transmission rate. FIG. 9 shows a block diagram of a mobile communication system according to the second embodiment. In the base station 40 shown in this figure, a communication environment information collecting unit 1 and a speech coding method determining unit 5
5 and an encoding method selection information transmitting unit 56 are provided. Compared to the example of FIG. 1, the communication mode determination unit 2 of FIG.
Is replaced by a speech coding scheme determining unit 55, and the mode selection information transmitting unit 3 of FIG.
Has been replaced by

Further, the mobile station 50 includes
1, a microphone 21, an A / D converter 22, a switching unit 52, a voice coding unit 23A, a voice coding unit 23B, a blocking unit 24, a convolution coding unit 25, and an interleave processing unit 2.
6, header adding unit 27, spreading unit 28, and power control unit 2
9 is provided.

As compared with the mobile station 20 shown in FIG. 1 of the first embodiment, the part of the transmission rate instructing unit 30 in FIG. 1 becomes a coding method instructing unit 51, and the voice encoding unit 23 in FIG. Speech encoder 2 adopting different encoding schemes
3A and a speech encoding unit 23B. A switching unit 52 is provided to transfer the output of the A / D converter 22 to one of the audio encoding unit 23A and the audio encoding unit 23B. The outputs of the audio encoding unit 23A and the audio encoding unit 23B are both output to the blocking unit 24. The configuration of other parts is exactly the same as that of the first embodiment.

Here, parts different from the system of the first embodiment will be sequentially described with reference to FIG. The base station 40 collects the communication environment information by the communication environment information collection unit 1, and determines an appropriate speech coding method according to the contents. The audio coding method determining unit 55 makes this method determination. The coding method selection information transmitting unit 56 transmits information for selecting the determined coding method to the mobile station 50. The encoding method instruction unit 51 receives this information and controls the switching unit 52.

The switching unit 52 includes, for example, the audio encoding unit 23A
Is selected, the output of the A / D converter 22 is output to the audio encoding unit 23A. The subsequent operation is exactly the same as the mobile station 20 of the first embodiment. In this way, when the communication environment is poor, an encoding method with a lower signal error rate is selected.

The coding system selection information transmitting section 5 of the base station 40
6 receives information indicating that another encoding method is to be selected, the encoding method instructing unit 51 controls the switching unit 52, and then controls the A / D converter 22 to the audio encoding unit 23B. Send output. The mobile station 50 may independently prepare the communication environment information collection unit 31 and the voice coding method determination unit 57, and control the selection of the coding method. Other operations are exactly the same as those in the first embodiment.

<Effect of Specific Example 2> As described above, by dynamically switching the encoding method according to the communication environment, high-quality multiplex communication with few signal errors can be performed as in the specific example 1. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a mobile communication system according to a specific example 1.

FIG. 2 is a diagram illustrating types of transmission rates.

FIG. 3 is an explanatory diagram of a timing example of mode selection.

FIG. 4 is an explanatory diagram of communication environment information collected by a base station.

FIG. 5 is an explanatory diagram of communication environment information collected by a mobile station.

FIG. 6 is an explanatory diagram of a method of transmitting mode selection information from a base station to a mobile station.

FIG. 7 is an explanatory diagram of an example of a mode selection operation.

FIG. 8 is an explanatory diagram of specific signal contents when a mode is changed.

FIG. 9 is a block diagram of a mobile communication system according to a specific example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Communication environment information collection part 2 Communication mode determination part 3 Mode selection information transmission part 4 Communication environment information 10 Base station 20 Mobile station 30 Transmission rate instruction part 31 Communication environment information collection part 32 Communication mode determination part

Claims (20)

[Claims] 1. A communication environment information collecting unit for collecting communication environment information for a mobile station performing mobile communication, and a communication mode determining unit for determining a communication mode suitable for the communication environment based on the collected communication environment information. A mobile communication system comprising: a transmission unit that selects one of two or more communication modes prepared in advance and executes communication by the mobile station. 2. When a mobile station communicates with another station through a base station, the base station includes: a communication environment information collection unit that collects communication environment information; A communication mode determining unit that determines a communication mode suitable for the communication environment; and a mode selection information transmitting unit that generates mode selection information for selecting a communication mode and transmits the mode selection information to the mobile station. Is prepared at a predetermined timing set in advance,
A mobile communication system comprising: a transmission unit that selects a communication mode from among two or more communication modes operating at different transmission rates and executes communication by a mobile station. 3. The system according to claim 1, wherein the transmission unit selects a new operation mode according to the mode selection information for each transmission frame, each transmission burst, and / or each call. A mobile communication system characterized by the above-mentioned. 4. The mobile communication system according to claim 1, wherein the mode selection information is included in header information of a transmission frame. 5. The mobile communication system according to claim 1, wherein the mode selection information is included in prefix information or ending information of a transmission burst. 6. The mobile communication system according to claim 1, wherein the mode selection information is included in control information transmitted and received during call setup. 7. The mobile communication system according to claim 1, wherein the mode selection information is input by a control switch of the mobile station. 8. The mobile communication system according to claim 2, wherein the environment information collection unit of the base station collects environment information from the mobile station. 9. The system according to claim 2, wherein the mode selection information transmission unit of the base station transmits the mode selection information to the moving mobile station based on the environment information of the moving destination of the mobile station. A mobile communication system for transmitting. 10. The system according to claim 2, wherein the mode selection information transmitting unit of the base station is configured to transmit a specific mobile station specified in advance even when a plurality of mobile stations are performing communication in the same environment. A mobile communication system for transmitting mode selection information only to a station. 11. A mobile station for performing mobile communication, a communication environment information collection unit for collecting communication environment information, and a speech code for determining a speech coding method suitable for the communication environment based on the collected communication environment information. And a coding scheme determining unit for generating coding scheme selection information for selecting the determined speech coding scheme, and operating at different preset transmission rates at a predetermined timing set in advance. A mobile communication system comprising: a transmission unit that selects a corresponding voice coding method from among the above voice coding methods and executes communication by the mobile station. 12. When a mobile station communicates with another station through a base station, the base station includes: a communication environment information collection unit that collects communication environment information; A speech coding scheme determining unit that determines a speech coding scheme suitable for the communication environment; and coding scheme for generating coding scheme selection information for selecting the determined speech coding scheme and transmitting the information to the mobile station. A method selection information transmission unit, wherein the mobile station has a predetermined timing set in advance,
Mobile communication characterized by comprising a transmission unit for selecting a corresponding voice coding system from among two or more voice coding systems operating at different transmission rates and executing communication by a mobile station. system. 13. The system according to claim 11, wherein the transmission unit selects a new speech coding scheme according to the coding scheme selection information, for each transmission frame, each transmission burst, and / or a call. A mobile communication system, characterized in that: 14. The mobile communication system according to claim 11, wherein the coding method selection information is included in header information of a transmission frame. 15. The mobile communication system according to claim 11, wherein the coding scheme selection information is included in prefix information or ending information of a transmission burst. 16. The mobile communication system according to claim 11, wherein the coding scheme selection information is included in control information transmitted and received during call setup. 17. The mobile communication system according to claim 11, wherein the coding scheme selection information is input by a control switch of a mobile station. 18. The mobile communication system according to claim 12, wherein the environment information collection unit of the base station collects environment information from the mobile station. 19. The system according to claim 12, wherein the coding scheme selection information transmitting unit of the base station performs coding on the moving mobile station based on environment information of a moving destination of the mobile station. A mobile communication system for transmitting method selection information. 20. The system according to claim 12, wherein the coding scheme selection information transmitting unit of the base station is configured to perform the identification specified in advance even when a plurality of mobile stations are performing communication in the same environment. A mobile communication system characterized by transmitting coding scheme selection information only to the mobile station.