JPH0865731A - Mobile object communication system - Google Patents

Abstract

PURPOSE: To provide a mobile object communication system capable of sufficiently corresponding to speech communication or data communication of >32kbps by enabling plural carrier frequencies to use and performing communication fitted in the optimum transmission rate capacity of the system. CONSTITUTION: Request transmission rate requested by a link channel establishment request message from a mobile station 101 is compared with the maximum transmission rate between a base station 100 and the mobile station 101 by a comparison means 104, and when the former is larger than the latter, a control part 103 judges whether or not the request transmission rate is the multiple of the maximum transmission rate, and sets the number of carrier frequencies corresponding to a judged result.

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 using the TDMA-TDD system.

[0002]

2. Description of the Related Art In recent years, regarding a mobile communication system using the TDMA-TDD system, "Radio System Development Center (RCR)" proposes a "second generation cordless telephone system standard proposal" (hereinafter, RCR STD-28). Standardization work is underway.

The RCR STD-28 defines a radio section interface between a mobile station and a base station of a mobile communication system as a defining point, and defines the following items as service attributes, and is used via a communication channel. It is assumed that 32 kbps voice communication is used as the transmission service.

Information transfer capability → Voice transfer mode → Circuit switching Information transfer rate → 32 kbps Communication form → Point / Point Further, the communication protocol is divided into a call connection phase and a communication phase, and the call connection phase is further linked in a wireless section. The link channel establishing phase for establishing a wireless link and the service channel establishing phase for setting a wireless link for a telephone service such as voice transmission and a non-telephone service such as ISDN. The link channel establishment phase relevant to the present invention will be described below.

In the link channel establishment phase, there is a function of using the control channel to select the link channel having the quality and capacity required for call connection and the protocol type, and the following channel setting message is defined.

(1) Link channel establishment request message (2) Link channel assignment message (3) Link channel assignment refusal message (4) Link channel establishment re-request message FIG. 5 shows a link channel assignment sequence.

In the figure, when a link channel establishment request message is transmitted from the mobile station on the control channel (T
1) In the base station, the service providing conditions such as the transmission rate are judged, and if the service can be provided, the link channel assignment message is transmitted to the mobile station (T2). At this time, the synthesizer is switched to change the carrier frequency to prepare for signal transmission to the designated communication physical slot. Upon receiving the link channel assignment message, the mobile station similarly prepares for signal transmission, then transmits a synchronization burst signal (T3), and synchronizes the communication physical slot (T4).

The link channel establishment request message requests the base station for the transmission rate of the link channel required for communication by the mobile station and the protocol type used for call connection. The format of the link channel establishment request message is shown in FIG. And FIG. 7 shows the information elements included in the link channel establishment request message.

The LCH type in the figure specifies the transmission rate and is 32 kbit / s as a standard. In voice circuit switching, voice is 32k by ADPCM encoding system.
Although the standard is specified because it is compressed to bps, 16 kbps and 8 kbps that are reserved are specified when using a voice encoding method with a high compression rate.

The link channel assignment message indicates the result of link channel assignment to the mobile station after the base station receives the link channel establishment request message. The reference station confirms that the transmission rate indicated by the link channel establishment request message and the protocol can be provided, and specifies the transmission rate, carrier number, absolute slot number, and relative slot number that can be provided in the link channel assignment message, Notify the mobile station.

FIG. 8 shows the format of the link channel assignment message, and FIG. 9 shows the information elements included in the link channel assignment message.

The carrier number in the figure specifies the carrier frequency of the carrier wave used between the base station and the mobile station. The absolute slot number indicates which of the four slots of TDMA was used to transmit the link channel assignment message. The relative slot number is used to specify a physical slot for communication that is actually reserved for a call such as voice and data. Further, the designation of the communication physical slot is determined by the relative slot number with the slot that is 2.5 ms after the slot (notified by the absolute slot number) in which the link channel allocation message is transmitted as the first slot.

A method of using the relative slot number is shown in FIG.

In the figure, (A) shows the transmission position of the link channel assignment message, and (B) shows one TDMA physical slot. The RCR STD-28 uses the 1.9 GHz band and is a 4-channel multiplexed multi-carrier TDMA-T.
Since DD is defined as a communication method, one frequency is divided into eight slots per 5 ms, and four slots (mobile station → base station) and four slots (base station → mobile station) are alternately allocated. There is.

FIG. 10 shows the position of the link allocation message when the absolute slot number of the link channel allocation message is designated by the first slot,
Uplink relative slot numbers are assigned as shown in (C), and downlink relative slot numbers are assigned as shown in (D).

Further, the relationship between the transmission rate and the physical slot position when the relative slot number is 1 is shown in (1) to (3) of FIG. (1) has a transmission rate of 32 bits kbps
At this time, the physical slot is repeated in the uplink and downlink in a 5 ms period. (2) is when the transmission rate is 16 kbps, and the physical slot is repeated every 10 ms in the uplink and downlink. (3) is when the transmission speed is 8 kbps,
The physical slot is repeated at a cycle of 20 ms each for uplink and downlink.

FIG. 11 shows a case where the relative slot number is designated as 2.

As shown in the figure, LCH type = 32 kb
ps and relative slot number = 2nd slot,
A second slot (number 2) is assigned based on the number 1 slot in (C) and (D). After that, uplink and downlink will appear alternately every 4 slots,
(E) is the physical slot of the received signal of the mobile station, (F) is the physical slot of the transmitted signal, and (F) is the physical slot of the transmitted signal.

Also in the RCR STD-28,
The maximum transmission capacity is 32 kbit / s,
The transmission method for transmission rates exceeding 32 kbit / s is not specified. Therefore, for example, a communication method using a plurality of time slots or a communication method using a plurality of carrier frequencies has not been established in the mobile communication system.

[0020]

However, in the above-mentioned conventional example, it is assumed that voice is used for the information transfer capability and voice communication is used for the information transfer rate of 32 kbps as the service attribute of the wireless section interface. There is a drawback that it cannot be used for voice communication or data communication.

That is, at present, the mainstream of the backbone communication network for digital data communication is the ISDN (Integrated Services Digi).
talNetwork: integrated service digital network), and its communication speed is guaranteed to be at least 64 kbps. In the conventional wireless section interface, IS
32k even when performing digital data communication with the DN network
There is a problem that only the information transfer rate of bps can be obtained and the information transfer rate of 64 kbps of the ISDN network cannot be fully utilized.

In view of the above-mentioned conventional problems, the present invention enables the use of a plurality of carrier frequencies and performs communication in accordance with the optimum transmission rate capacity of the system.
It is an object of the present invention to provide a mobile communication system capable of sufficiently coping with voice communication or data communication of kbps or higher.

[0023]

To achieve the above object, a first invention is a mobile communication system for communicating between a base station and a mobile station by a TDMA-TDD system by a carrier having a predetermined carrier frequency. , The base station compares the requested transmission rate requested by the mobile station with the maximum transmission rate between the base station and the mobile station, and sets 1 according to the comparison result.
The comparison means is provided for setting one or a plurality of different carrier frequencies.

In a second aspect based on the first aspect, the comparison means compares the request transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate. Transmission speed comparison means,
When the required transmission rate is higher than the maximum transmission rate, the first determination means determines whether the required transmission rate is a multiple of the maximum transmission rate and the determination result of the first determination means. And a first carrier number setting means for setting the number of carrier frequencies.

In a third aspect based on the first aspect, the comparing means compares the required transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate. Transmission speed comparison means,
When the required transmission rate is higher than the maximum transmission rate, second determining means for determining whether or not all carrier frequencies are vacant, and that all carrier frequencies are vacant by the second determining means When it is determined, a second carrier number setting means for setting the number of carrier frequencies to a predetermined number is provided.

In a fourth invention based on the first invention, the carrier frequency is divided into a plurality of groups, and the comparison means is the requested transmission rate requested by the link channel establishment request message from the mobile station. And a third transmission rate comparison means for comparing the maximum transmission rate with
When the requested transmission rate is higher than the maximum transmission rate, a third determination unit that determines whether or not a carrier frequency is empty in a predetermined group, and a carrier in the predetermined group by the third determination unit A third carrier number setting means for setting the number of carrier frequencies to a predetermined number when it is determined that there is an empty frequency,
For each of the groups, the third determination means and the third
The carrier number setting means is executed.

In a fifth aspect based on the fourth aspect, each group of the carrier frequencies is fixedly assigned to the mobile station.

[0028]

According to the first aspect of the present invention, the comparison means of the base station compares the requested transmission rate required by the mobile station with the maximum transmission rate between the base station and the mobile station, One or a plurality of different carrier frequencies are set according to the comparison result. As a result, a plurality of carrier frequencies are used in mobile communication, an appropriate carrier frequency is selected, and the reference station is able to communicate with the mobile station even when the request exceeds the maximum transmission rate of one slot. It becomes possible to indicate the speed. Moreover, since a plurality of different carrier frequencies are used, it is not necessary to consider interference between slots.

According to the second invention, the first transmission rate comparing means of the comparing means compares the required transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate, The determining means determines whether or not the required transmission rate is a multiple of the maximum transmission rate when the required transmission rate is higher than the maximum transmission rate. Further, the first carrier number setting means sets the number of carrier frequencies according to the judgment result of the first judging means. As a result, the number of carrier frequencies can be accurately calculated even when a plurality of carrier frequencies are required.

According to the third invention, the second transmission rate comparing means of the comparing means compares the required transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate, and makes the request. When the transmission rate is higher than the maximum transmission rate, the second determination means determines whether or not all carrier frequencies are available. Further, when it is determined that all carrier frequencies are vacant, the second carrier number setting means sets the number of carrier frequencies to a predetermined number. As a result, even when a plurality of carrier frequencies are required, the number of carrier frequencies can be set more easily than in the second aspect.

According to the fourth invention, the third transmission rate comparing means of the comparing means compares the required transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate, and requests transmission. When the speed is higher than the maximum transmission speed, the third judging means judges whether or not there is an empty carrier frequency in the predetermined group. Further, when it is determined that there is an empty carrier frequency in the predetermined group, the third carrier number setting means sets the number of carrier frequencies to a predetermined number. Then, the third determination means and the third carrier number setting means are executed for each group of carrier frequencies divided into a plurality of groups. As a result, the probability of selecting the carrier frequency is higher than in the third aspect, and the number of times the carrier frequency is searched is reduced.

According to the fifth invention, since each group of carrier frequencies in the fourth invention is fixedly allocated to the mobile stations, the mobile stations can be assigned the same frequency at the same time. Disappear.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a mobile communication system according to the present invention.

In the figure, 100a and 100b are base stations of the mobile communication system, both of which are connected to the exchange 102. 101a and 101b represent mobile stations, and the base station 100
(General term for base stations 100a and 100b) and TDMA-TD
It communicates with the D type digital wireless interface. The exchange 102 may be a private network exchange or a public network exchange. Generally, the difference between the private network and the public network is the carrier frequency used by the control signal, the originating identification code, the configuration of the destination identification code, etc., but these are all obstacles to the implementation of the present invention. I won't.

The base station 100 has a control section 103, a comparison means 104, a radio communication section 105, and a frequency synthesizer section 106. The control unit 103 includes a CPU, a ROM that stores programs, a memory RAM, and the like, and controls the entire base station 100. However, in FIG. ,
And the relationship with the frequency synthesizer unit 106 only.

The comparison means 104 of the base station 100 compares the transmission rates according to the instruction from the control section 103. The comparison means 104 is programmed and stored in the ROM in the control unit 103, and is used for the mobile station 101 (mobile station 101).
a, 101b generically) transmits a link channel establishment request message, is received by the base station 100, and is passed from the wireless communication unit 105 to the control unit 103.
03 is called to analyze the transmission rate required by the mobile station 101 according to the content of the message.

Radio communication section 105 (radio communication section 105a,
The generic term 105b) includes a bandpass filter, a high frequency amplifier, an intermediate frequency amplifier, a modulator / demodulator, and the like. The wireless communication unit 105 includes a base station 100 and a mobile station 1.
There may be a plurality of wireless interfaces depending on the communication capacity of the wireless interface with 01. For example, R as in the conventional example
In CR STD-28, communication capacity using one carrier frequency is up to 32 kbps, so ISDN
Two sets of wireless communication units 105 are required to perform communication at 64 kbps, which is the basic interface of the network.

The frequency synthesizer unit 106 (generic term for the frequency synthesizer units 106a and 106b) gives a carrier frequency to the radio communication unit 105. Similarly to the wireless communication unit 105, there may be a plurality of frequency synthesizer units 106 depending on the communication capacity, and there is a one-to-one correspondence with the wireless communication unit 105.

In the link channel establishment phase shown in the conventional example, the mobile station 101a designates the requested transmission capacity as the LCH type of the link channel establishment request message and transmits it to the base station 100a. With the LCH type of the conventional example, only a maximum transmission rate of 32 kbps can be specified, but the type parameter can be expanded to specify up to 64 kbps.

The mobile station 101 puts a link channel establishment request message designated as 64 kbps on the control carrier frequency and transmits it to the base station 100a. The base station 100a that has received the link channel establishment request message
A link channel establishment request message is sent to the control unit 103. The control unit 103 extracts the LCH type of the link channel establishment request message and calls the comparison unit 104 to compare the transmission rates.

FIG. 2 is a flow chart showing the processing of the comparing means 104 of the base station 100. Note that this processing procedure is programmed and stored in the ROM in the control unit 103.

The comparison means 104, which has received the link channel establishment request message from the control unit 103 (step S2)
00), the LCH type is extracted, and the transmission rate (requested transmission rate) instructed by the mobile station 101a is checked (step S201). The instructed transmission rate is compared with the maximum transmission rate (step S202). The maximum transmission rate referred to here is the maximum transmission rate when one communication physical slot is used at one carrier frequency between the base station 100 and the mobile station 101. For example, the conventional STD-
In 28, since one communication physical slot has a communication speed capacity of 32 kbps at one carrier frequency,
The maximum transmission rate is 32 kbps.

As a result of comparison in step S202, if the transmission rate ≦ maximum transmission rate, the base station 100 and the mobile station 101 can communicate with each other even if only one carrier frequency is used, so the number of carrier numbers is set to one. (Step S204). If the transmission rate> the maximum transmission rate, multiple carrier frequencies are required according to the transmission rate.
It is checked whether the transmission rate is a multiple of the maximum transmission rate (step S203).

If it is a multiple, the number of carrier numbers is set to the number of quotients obtained by dividing the transmission rate by the maximum transmission rate (step S).
205). If it is not a multiple, the number of carrier numbers is set to the number obtained by adding 1 to the quotient obtained by dividing the transmission rate by the maximum transmission rate (step S206).

The transmission rate designated as described above is 64k.
When the bps and the maximum transmission rate are 32 kbps, the number of carrier numbers used for communication is two.

After that, the number of carrier numbers determined in each process is sent to the control unit 103 as a parameter of the carrier frequency switching request (step S207).

Upon receiving the carrier frequency switching request, the control unit 103 selects a vacant carrier frequency based on the parameter of the number of carrier numbers. A control command is sent to the frequency synthesizer unit 106 to switch the wireless communication unit 105 to the selected carrier frequency.

The carrier frequency is set to 2 such as 64 kbps.
Frequency synthesizers 106a, 1
A control command is sent to two of 06b. The frequency synthesizer units 106a and 106b correspond to the corresponding wireless communication unit 1.
A frequency switching instruction is given to 05a and 105b.

After the carrier frequency is determined, the control unit 103 transmits a link channel allocation message in which a carrier number corresponding to the switched carrier frequency is set to the mobile station 101a through the wireless communication unit 105, and the mobile station 101a and Synchronize.

In this way, the base station 100 becomes the mobile station 1
01, a plurality of wireless links are established to enable communication at a designated transmission rate.

FIG. 3 is a flowchart of the comparing means 104 of the base station 100 showing the second embodiment of the mobile communication system according to the present invention.

The transmission rate designated by the link channel establishment request message from the mobile station 101a is compared with the comparison means 104.
Parsed by At this time, in the first embodiment, the instructed transmission rate and the maximum transmission rate are compared and it is further determined whether or not the transmission rate is a multiple of the maximum transmission rate. You have to do the division,
Calculation may take time. Therefore, in this embodiment, a simple processing procedure is shown.

The instructed transmission rate is compared with the maximum transmission rate by the comparison means 104 (step S30).
0). The maximum transmission rate described here is the maximum transmission rate when one communication physical slot is used in one carrier frequency between the base station 100 and the mobile station 101. For example, in the conventional STD-28, one communication physical slot has 32 kb at one carrier frequency.
Since there is a communication speed capacity of ps, 32 kbps is the maximum transmission speed. The maximum transmission rate is selected from the LCH types shown in the information element in the link channel establishment request message of FIG.

As a result of comparison, if the transmission rate ≦ maximum transmission rate, the communication between the base station 100 and the mobile station 101 is possible even with one communication physical slot, as in the first embodiment. Number of carrier numbers for switching request is 1
The number is set individually (step S302).

If the transmission rate> the maximum transmission rate, a plurality of carrier frequencies are required according to the transmission rate, but if another mobile station 101 is not in communication and is not using the carrier frequency at all, It is possible to perform communication by occupying all carrier frequencies.

Therefore, a vacancy in the carrier frequency is searched (step S301), and if there is a vacancy, the number of carrier numbers is set to the number of carrier numbers at the maximum transmission speed (step S303). Then, the determined number of carrier numbers is sent to the control unit 103 as a parameter of the carrier frequency switching request (step S305). If it is not available, an error is notified to the control unit 103 and the process is terminated (step S3).
04).

FIG. 4 is a flowchart of the comparing means 104 of the base station 100 showing the third embodiment of the mobile communication system according to the present invention.

In the second embodiment described above, it is checked whether the carrier frequencies are all empty (step S301).
The carrier number defined in CR STD-28 is shown in FIG.
As shown in, there are 50 from 1 to 50. Mobile station 1
It takes time to search for 50 carrier frequencies each time a link channel establishment request message arrives from 01, and one base station 100 uses most carrier frequencies at a time with a plurality of mobile stations 101. Probability is low and you don't have to search all. Therefore, in this embodiment, the carrier frequency is divided into several groups and a search is performed for each group.

At this time, the grouping is performed, for example, by the mobile station 1.
There is a method in which the maximum value of the transmission rate required by 01 is used as a reference. The mobile station 101 has an ISDN transmission rate of 64 kb
If ps is requested as the maximum transmission rate, the group is 3
By bundling two 2 kbps, 32 groups can be divided by 64 kbps. Therefore, in this embodiment, the number of searches is half that in the second embodiment.

In FIG. 4, first, the comparison means 104 analyzes the transmission rate instructed by the link channel establishment request message from the mobile station 101a. The instructed transmission rate is compared with the maximum transmission rate by the comparison means 104 (step S400). The maximum transmission rate described here is the maximum transmission rate when one communication physical slot is used at one carrier frequency between the base station 100 and the mobile station 101. For example, the conventional STD
With -28, since one communication physical slot has a communication speed capacity of 32 kbps at one carrier frequency, the maximum transmission speed is 32 kbps. Usually, the maximum transmission rate is selected from the LCH types shown in the information element in the link channel establishment request message of FIG.

As a result of the comparison in step S400, if the transmission rate ≦ the maximum transmission rate, the base station 100 and the mobile station 10
Since the communication of No. 1 is possible with one communication physical slot as in the first embodiment, the number of carrier numbers in the carrier frequency switching request is set to one (step S40).
3). If the transmission rate> the maximum transmission rate, a plurality of carrier frequencies are required according to the transmission rate, and therefore the allocation block number is extracted. The allocation block number extracted at this time may be extracted in a so-called cyclic hunt format, in which the previously used one is stored and the next one is automatically selected, or it is fixedly allocated to the mobile station 101. The number may be extracted (step S401).

Therefore, a vacancy of the carrier frequency in the extracted block number is searched (step S402), and if there is a vacancy, the number of carrier numbers is set to a predetermined number of carrier numbers and the block number is used as a parameter (step S402). S404). The set carrier number and block number are sent to the control unit 103 as parameters of the carrier frequency switching request (step S407). If it is not empty, it is determined whether or not all blocks have been searched, and if not, the next block number is extracted (step S405).

When all blocks have been searched, the control unit 1
03 is notified of an error and the process is terminated (step S40).
6).

[0065]

As described above, according to the first aspect of the invention, the base station compares the requested transmission rate required by the mobile station with the maximum transmission rate between the base station and the mobile station. Since the reference station is provided with the comparing means for setting one or a plurality of different carrier frequencies according to the comparison result, the reference station can perform transmission capable of communicating with the mobile station even when the request exceeds the maximum transmission rate of one slot. It becomes possible to indicate the speed. Therefore,
The mobile station can perform communication adapted to the optimum transmission rate capacity of the mobile communication system, and can sufficiently deal with voice communication or data communication of 32 kbps or higher.

Further, since a plurality of different carrier frequencies are used, as compared with the case where one carrier frequency is used and a plurality of communication physical slots are used to secure a communication speed capacity of 32 kbps or more, It is not necessary to consider interference, and there is an effect that the degree of error correction can be reduced.

According to a second invention, in the above-mentioned first invention, the comparing means compares the requested transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate. First transmission rate comparing means, first determining means for determining whether or not the required transmission rate is a multiple of the maximum transmission rate when the required transmission rate is higher than the maximum transmission rate, and the first transmission rate comparing means For setting the number of carrier frequencies according to the determination result of the determination means
Since the above-mentioned carrier number setting means is provided, it is possible to accurately calculate the number of carrier frequencies even when a plurality of carrier frequencies are required.

According to a third invention, in the above-mentioned first invention, the comparing means compares the requested transmission rate requested by the link channel establishment request message from the mobile station with the maximum transmission rate. A second transmission rate comparing means, a second determining means for determining whether or not all carrier frequencies are available when the required transmission rate is higher than the maximum transmission rate, and the second determining means. When it is determined that all the carrier frequencies are vacant, a second carrier number setting means for setting the number of the carrier frequencies to a predetermined number is provided. However, the number of carrier frequencies can be easily set, and there is an effect that interference from other mobile stations is not received.

In a fourth invention based on the above-mentioned first invention, the carrier frequency is divided into a plurality of groups, and the comparison means is the requested transmission rate requested by the link channel establishment request message from the mobile station. And a third transmission rate comparison means for comparing the maximum transmission rate with
When the requested transmission rate is higher than the maximum transmission rate, a third determination unit that determines whether or not a carrier frequency is empty in a predetermined group, and a carrier in the predetermined group by the third determination unit A third carrier number setting means for setting the number of carrier frequencies to a predetermined number when it is determined that there is an empty frequency,
For each of the groups, the third determination means and the third
Since the carrier number setting means is executed, the probability of selecting the carrier frequency is increased and the number of times the carrier frequency is searched is reduced, so that the processing load is reduced.

According to the fifth invention, in the above-mentioned fourth invention, since each group of the carrier frequencies is fixedly assigned to the mobile station, the probability that the mobile stations simultaneously designate the same frequency. Is eliminated, and the probability of selecting the carrier frequency is increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a mobile communication system according to the present invention.

FIG. 2 is a flowchart showing a process of a comparison unit in the first embodiment.

FIG. 3 is a flowchart of comparison means showing a second embodiment of the mobile communication system according to the present invention.

FIG. 4 is a flowchart of comparison means showing a third embodiment of the mobile communication system according to the present invention.

FIG. 5 is a link channel allocation sequence diagram.

FIG. 6 is a format diagram of a link channel establishment request message.

FIG. 7 is a diagram showing information elements included in a link channel establishment request message.

FIG. 8 is a format diagram of a link channel assignment message.

FIG. 9 is a diagram showing information elements included in a link channel assignment message.

FIG. 10 is a diagram showing a method of using relative slot numbers.

FIG. 11 is a diagram showing a case where a relative slot number is designated to 2;

[Explanation of symbols]

 100a, 100b Base station 102 Exchanger 101a, 101b Mobile station 103 Control unit 104 Comparing means 105 Wireless communication unit 106 Frequency synthesizer unit

Claims (5)

[Claims] 1. A carrier having a predetermined carrier frequency,
In a mobile communication system for communicating between a base station and a mobile station by a TDMA-TDD system, the base station has a requested transmission rate requested by the mobile station and a maximum transmission rate between the base station and the mobile station. And a comparing means for setting one or a plurality of different carrier frequencies according to the comparison result. 2. The first comparing means for comparing the requested transmission rate requested by a link channel establishment request message from the mobile station with the maximum transmission rate, and the requested transmission rate. Is greater than the maximum transmission rate, a first determination unit that determines whether the requested transmission rate is a multiple of the maximum transmission rate, and the carrier frequency of the carrier frequency is determined according to the determination result of the first determination unit. The mobile communication system according to claim 1, further comprising first carrier number setting means for setting the number. 3. The second comparing means for comparing the required transmitting speed requested by a link channel establishment request message from the mobile station with the maximum transmitting speed, and the required transmitting speed. Is greater than the maximum transmission rate, second determining means for determining whether or not all carrier frequencies are vacant, and when it is determined by the second determining means that all carrier frequencies are vacant 2. The mobile communication system according to claim 1, further comprising second carrier number setting means for setting the number of the carrier frequencies to a predetermined number. 4. The carrier frequency is divided into a plurality of groups, and the comparing means compares the requested transmission rate requested by a link channel establishment request message from the mobile station with the maximum transmission rate. Transmission rate comparison means of No. 3, third determination means for determining whether or not there is an empty carrier frequency in a predetermined group when the required transmission rate is higher than the maximum transmission rate, and the third determination means And a third carrier number setting means for setting the number of carrier frequencies to a predetermined number when it is determined that there is an empty carrier frequency in the predetermined group by the third group. 3 determination means and the third
2. The mobile communication system according to claim 1, wherein said carrier number setting means is executed. 5. The mobile communication system according to claim 4, wherein each group of the carrier frequencies is fixedly allocated to the mobile station.