JPH11262044A - Base station of multi-carrier tdma mobile communication system and method for assigning communication channel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly cope with a channel assigning request from a mobile terminal and also to reduce call lossed by securing beforehand a candidate channel to be assigned to the mobile terminal and the candidate channel adapting to a condition requested by means of the mobile terminal in management tables. SOLUTION: CPUs 511 of the respective base stations check the dead state of a communication channel and respectively register the candidate channel for a single channel to be assigned to a single channel type mobile terminal and the plural groups of candidate channels to be assigned to a multi-channel type mobile terminal in first and second management tables of RAM 512. At this time, the multi-channel communication candidate channel is selected before the single channel communication channel, the channel for satisfying three- channel array condition requested by the multi-channels is secured, and the channel satisfying a communication quality condition is selected from the management table at the channel assigning of request from the mobile terminal. In this way, a prescribed channel assigning time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station which communicates with a plurality of mobile terminals via a radio communication channel, and more particularly, to a plurality of carrier frequencies and a carrier rear frequency in a time division manner. The present invention relates to a multi-carrier TDMA radio base station for establishing a plurality of wireless communication channels by selectively combining a plurality of formed time slots and a communication channel assignment method.

[0002]

2. Description of the Related Art Some digital cordless telephone systems employ a multicarrier TDMA as a wireless channel access system. Multi-carrier TD
In MA, each base station has a plurality (M) of TDMAs.
By using a plurality of (N) carrier frequencies in which time slots are formed, a total of N × M channels can be formed. As shown in RCR STD-28 (RCR: Radio System Development Center), each mobile terminal in a digital cordless telephone system starts communication or when a mobile terminal moves from one cell area to another cell area. At the time of the handover that occurs, a communication channel (information channel) is allocated from the base station via the control channel, and thereafter, communication is performed using the allocated communication channel. Each base station in the multi-carrier TDMA telephone system receives a plurality of (N ×
A channel satisfying a predetermined communication quality, for example, a channel having a CIR (carrier-to-interference power ratio) exceeding a predetermined threshold is selected from the channels of M), and the selected channel is assigned to the mobile terminal.

[0003] As a method of selecting a channel, for example, a combination of a carrier frequency and a time slot position for specifying a start channel of a quality check is randomly selected, and a combination of a carrier frequency and a time slot number is sequentially shifted. First Available (FA: Fie) that measures the communication quality of a channel and assigns the first found channel that satisfies the predetermined quality to the mobile terminal.
and a worst-case CIR method that measures the quality of all N × M channels and allocates the lowest quality channel among the found channels that satisfy the predetermined quality to the mobile terminal. The worst CIR method has an advantage that the frequency use efficiency can be improved, but has a problem that it takes time for channel assignment.

In order to improve the problem of the worst CIR method,
For example, in JP-A-6-209283, one of a plurality of time slots is randomly selected, the time slot is fixed to the selected time slot, and N is specified by changing only the carrier frequency. A channel allocation method has been proposed in which communication quality is measured for a number of channels, and a carrier with the lowest quality is selected from among carriers that satisfy the predetermined quality found and allocated to a mobile terminal. The above improved worst CIR
According to the method, when a carrier satisfying a predetermined communication quality is not found in the initially selected time slot, the position of the time slot is changed, and a channel to be allocated to a terminal is selected by the FA method. Multi-carrier D described above
In the TMA wireless communication system, a high-speed data communication service that requires assignment of a plurality of communication channels to one mobile terminal is being studied. In this case, for example, a “channel having the same carrier and a different time slot” or a “channel having a different carrier frequency, There are restrictions such as "channels with discontinuous slots."

[0005]

However, in the conventional channel allocation method of randomly allocating one communication channel in response to a request from a mobile terminal, in a channel arrangement represented by a combination of a carrier frequency and a time slot, Unused channels are left in an irregular arrangement, so when a mobile terminal requests simultaneous allocation of multiple channels, the base station has no remaining channels that satisfy the allocation conditions desired by the mobile terminal, and There is a high possibility of a call loss due to the inability to do so. Further, in the related art, since a channel selection operation is started after a channel allocation request is received, it takes a long time to allocate a channel to a plurality of channel allocation requests accompanied with the above-described special constraints. There's a problem.

An object of the present invention is to provide a communication channel allocating method and a base station which can quickly respond to a request for allocating a plurality of channels from a mobile terminal. Another object of the present invention is to provide a communication channel allocating method and a base station that can reduce the occurrence of call loss in response to a request for allocating a plurality of channels from a mobile terminal.

[0007]

In order to achieve the above object, a base station for a multi-carrier DTMA radio communication system according to the present invention comprises a plurality of communication channels specified by a carrier frequency and a time slot number. Reference is made to the management table memory in which at least one set of candidate channels for the selected multi-channel communication is registered, and the management table memory when receiving a channel allocation request from a multi-channel mobile terminal using a plurality of channels. A channel assignment device for assigning a communication channel to the mobile terminal. More specifically, the set of candidate channels for multi-channel communication registered in the management table memory is:
For example, the channel assignment device includes a plurality of candidate channels satisfying a predetermined relative relationship in a channel arrangement determined by a carrier frequency and a time slot number, and the channel assignment device includes a plurality of candidate channels included in the candidate channel set.
A channel suitable for the mobile terminal is selected.

Another feature of the present invention is that the channel allocating device has means for jointly measuring the communication quality of the candidate channel selected with reference to the management table memory with the mobile terminal, When there is no candidate channel satisfying the predetermined communication quality to be allocated to the mobile terminal in the table memory, from among other communication channels not registered in the management table memory, the predetermined communication quality to be allocated to the mobile terminal is satisfied. Another object is to include means for searching for an empty channel.

In a preferred embodiment of the invention, the base station comprises:
A first management table for registering at least one candidate channel for single-channel communication selected from a plurality of communication channels each specified by a carrier frequency and a time slot number; A second management table for registering at least one set of candidate channels for the selected multi-channel communication, wherein when a channel assignment request is received from a mobile terminal, the first, second, or third channel is selected according to the type of the mobile terminal. The communication channel to the mobile terminal is allocated by selectively referring to one of the two management tables.

If the mobile terminal that has issued the channel assignment request is of the single-channel communication type, the first management table
In the case of the multi-channel type, the second management table is referred to. The contents of the first and second management tables are updated when the mobile terminal starts or ends communication, when the channel is switched, or periodically. The process of updating the second table for multi-channel communication has priority over the first table for single-channel communication, and the multi-carrier TDM
A plurality of sets of free channels selected by a predetermined selection procedure from the plurality of channels formed by A are registered. Whether a channel is idle or not can be determined by the level of the received radio wave of each channel. According to one embodiment of the present invention,
By communicating with at least one mobile terminal, the candidate channel determined to be an empty channel at the level of the received radio wave is checked whether it is a valid candidate channel.

[0011] When the multi-channel mobile terminal to which the first channel for multi-channel communication is allocated starts the calling procedure without requesting the second channel, the second
The second channel left in the management table is wasted.
In this case, in one embodiment of the present invention, the base station intentionally lowers the transmission power of the first channel to cause the mobile terminal to issue a channel switching request, and responds to the channel switching request. The communication channel is assigned with reference to the first management table. The first channel is released by the channel switching, and is registered again as a candidate channel for multi-channel communication in the second management table in the next management table update process.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a digital cordless telephone system which is an example of a mobile radio communication system to which the present invention is applied. In FIG. 1, 101 to 103 are mobile terminals (MS), 104 to 105 are base stations (BS), 1
Reference numeral 06 denotes an exchange connected to the base station, and 107 denotes another communication network connected to the exchange 106. Base station 10
4 to 105 form communication areas determined by the respective transmission radio field intensities. Each of the mobile terminals 101 to 103 located in these communication areas is connected to the exchange 106 via a base station in the communication area. Communicates with another mobile terminal or a terminal device connected to another communication network 107.

FIG. 2 shows the configuration of the base stations 104 to 105. In the figure, 501 is an antenna, 502 is a radio unit for transmitting and receiving radio waves via the antenna, 503 is a plurality of demodulation circuits connected to the radio unit 502 for demodulating received signals of different carrier frequencies, 504 Are a plurality of demodulation circuits connected to the radio section 502 for modulating transmission signals of different carrier frequencies, respectively.
Reference numeral 5 denotes a channel codec connected to the demodulation circuit 502 and the modulation circuit 503, and reference numeral 506 denotes encoding of voice communication data connected between the channel codec 505 and a wired network (digital network: ISDN) interface 507. Transcodec 508 for decoding / decoding
A data demultiplexing unit connected between the channel codec 505 and the wired network interface 507 for speed conversion of data for data communication. The data demultiplexing unit 508 is a mobile communication device that uses a plurality of communication channels simultaneously. In data communication with a terminal, a process of multiplexing / demultiplexing data to the plurality of channels is also performed. The base station
The exchange 106 via the wired network interface 507
Is connected to

Reference numeral 509 denotes a quality measuring unit for measuring communication quality; 510, a memory for storing various programs;
Reference numeral 11 denotes a processor constituting a main part of the channel allocation device of the present invention, and 512 denotes a memory for storing various table data described later. The processor 51
1 is coupled to other elements of the base station via an internal bus,
By executing the program stored in the memory 510,
The operation of the base station and the channel assignment according to the present invention described later are realized.

FIG. 3 shows a relationship between a carrier frequency and a time slot in multicarrier TDMA. In multi-carrier TDMA, a plurality of carrier frequencies f0,
A frame including a plurality of time slots is transmitted at each carrier frequency using f1 to fn. Transmission from the mobile terminal to the base station is performed in time slots TS1 to TS4 defined as the uplink channel 200, and transmission from the base station to the mobile terminal is performed in time slots TS1 to TS4 defined as the downlink channel 201. Of the plurality of carrier frequencies, f0 is used for control information, and f1 to fn are used for communication of user information. As shown by hatching, the communication channels are allocated to the respective mobile terminals because time slots having the same positional relationship are allocated to the uplink channel 200 and the downlink channel 201, and therefore, the embodiments of the present invention will be described below. Is performed focusing on the uplink channel 200.

FIG. 4 shows an arrangement of communication channels when the number of time slots per frame is 4 and the number of carrier frequencies is n. In this example, a total of 4n communication channels are formed, and each communication channel has a carrier frequency f
Is n and the time slot number is s (= 1 to 4), a channel number represented by n + (s-1) is given. In the following description, channel number n + (s-1)
, Each communication channel is represented by CH (f, s).

In the present invention, each base station checks the availability of a communication channel prior to a channel assignment request from the mobile terminal, and checks whether the mobile terminal uses one communication channel per direction (hereinafter referred to as a single channel type). Mobile terminal)
And a plurality of sets of candidate channels for multi-channel communication to be assigned to a mobile terminal using a plurality of communication channels per direction (hereinafter referred to as a multi-channel mobile terminal). These are registered in the first and second management tables, respectively.

In this case, by selecting a candidate channel for multi-channel communication prior to a candidate channel for single-channel communication, a candidate channel satisfying the channel arrangement condition required by the multi-channel terminal can be secured. Further, when a mobile terminal actually requests a channel allocation, by selecting a channel satisfying the communication quality condition from among the candidate channels registered in the management table, the time required for channel allocation can be reduced.

FIG. 5 shows an example of a single channel management table 300 for registering candidate channels for single channel communication. The single channel management table 300 stores one candidate channel for each of the time slots TS1 to TS4. When a base station receives a channel assignment request from a single channel mobile terminal, the base station registers the candidate channels registered in the table 300. A channel to be allocated to the mobile terminal is searched from the channels. Here, one candidate channel is registered for each time slot, but a plurality of candidate channels may be registered for each time slot. FIG.
Shows an example of a multi-channel management table 400 for registering candidate channels for multi-channel communication.
Here, a two-channel mobile terminal is assumed as a multi-channel mobile terminal. Multi-channel management table 40
0 stores a plurality of sets of candidate channels 400-1 to 400-3 having group numbers g1 to g3. In the example shown here, each set includes a candidate channel CH1 to be assigned as a first channel to a two-channel mobile terminal,
Candidate channels CH2, C to be assigned as channels
H3 and CH4. When the base station receives the first channel allocation request from the two-channel mobile terminal, the base station refers to the management table 400 and allocates any one of the channel groups, for example, the first candidate channel CH1 registered in g1. When a request for allocating a second channel is received from the same mobile terminal, a candidate channel suitable for the communication function of the mobile terminal is selected from the second candidate channels CH2 to CH4 registered in the channel group g1. .

The candidate channel CH2 is a channel formed by another empty time slot in a frame transmitted at the same carrier frequency as the first candidate channel CH1, and the candidate channel CH3 has no restriction on the carrier frequency. The first candidate channel CH1 is a channel formed by empty time slots having a temporally discontinuous positional relationship with the first candidate channel CH1, and the candidate channel CH4 is an arbitrary carrier frequency having no channel arrangement restriction with respect to the first candidate channel CH1. /
This is a channel formed by empty time slots of time slots. Here, as an example, the management table 40
Although only three sets of candidate channels (g1 to g3) are registered in 0, more sets of candidate channels can be registered in actual applications.

The contents of the management tables 300 and 400 are obtained by causing the processor 511 to execute the management table update program described in FIGS. 7 and 8 periodically or at the end of the process of allocating channels to one mobile terminal. Be updated. The update program for the management table may be executed even when the already allocated communication channel is released due to termination of communication by one mobile terminal, switching of channels, handover, or the like.

FIG. 7 is a flowchart showing a processing procedure of an update program of the single channel management table 300. In order to sequentially find candidate channels in each of the time slots TS1 to TS4 of the single channel management table 300, first, a value of a parameter s indicating a time slot number is set to an initial value 0 (step 701), and a value of the parameter s is set. Is incremented (step 702). The value of the incremented parameter s is determined (step 703), and when the value of the parameter s exceeds the upper limit value 4, the program ends.

If the value of the parameter s is equal to or less than the upper limit value 4, the carrier frequency f serving as a starting point for searching for a candidate channel is determined.
Is randomly selected (step 705), and it is determined whether or not the channel CH (f, s) to be checked is already registered in the multi-channel management table 400 as a candidate channel for multi-channel communication (step 70).
5). If the target channel CH (f, s) has not been registered as a candidate channel, it is determined whether or not the target channel is an empty channel having a predetermined communication quality (step 706). To determine the state of the target channel, the received signal by the demodulation circuit 503 corresponding to the carrier frequency f is taken into the quality measuring section 509, and when the received radio wave level including the interfering wave is equal to or lower than the predetermined level, the communication quality is provided. It may be determined that the channel is empty.

If the target channel CH (f, s) is a free channel having a predetermined communication quality, the identifier (or channel number) of the target channel is stored in the management table 30.
It is registered as a candidate channel for the 0th s-th time slot (step 707), and the process returns to step 702. If the target channel CH (f, s) is not an empty channel having a predetermined communication quality, or if the target channel CH (f, s) has already been registered as a candidate channel for multi-channel communication, the channel for all carrier frequencies in the s-th time slot It is determined whether the status check has been completed (step 70).
8) If the determination result is YES, it is determined that there is no applicable candidate channel in the s-th time slot, and the process returns to step 702. If the determination result is NO, the carrier frequency f is changed to the next frequency. (Step 70
9), and return to the determination step 705. Step 709
The switching of the carrier frequency f is started from the starting point carrier frequency fi which is randomly selected for each time slot and proceeds in the fn direction in FIG.
It is performed cyclically so as to return to 1 and proceed in the direction of the starting point carrier fi.

In the above embodiment, candidate channels are sequentially selected for all time slots. For example, in response to a channel assignment request from a mobile terminal, the base station sets the j-th time slot. When a registered candidate channel is allocated, a new candidate channel is searched for only in the j-th time slot,
A range of a time slot for searching for a candidate channel may be specified.

Further, in the above embodiment, in each time slot, an FA (Fiest available) in which the first found free channel satisfying a predetermined quality is set as a candidate channel.
Although the method is adopted, in each time slot, the communication quality may be measured for all available channels, and the channel with the worst communication quality among the available channels satisfying the predetermined quality may be registered as a candidate channel. .

In the above embodiment, the candidate channel selected by the FA method is dispersed in the channel arrangement by randomly selecting the starting carrier frequency for each time slot. The relationship between the carrier frequency of the selected candidate channel and the carrier frequency of the candidate channel already registered in another time slot is determined, and if the carrier frequency is biased, another channel is searched for. The arrangement bias may be reduced.

FIG. 8 shows a multi-channel management table 40.
The outline of the processing procedure of the update program 0 is shown below. This program is executed prior to the update program of the single channel management table shown in FIG. In this embodiment, first, initial values are set for a parameter g indicating a group number, a parameter f indicating a carrier frequency, and a parameter s indicating a time slot number (step 80).
1) Increment the group number (step 80)
After 2), it is determined whether the group number has exceeded a predetermined upper limit (step 803). If the group number exceeds the upper limit, the program is terminated. Otherwise, the candidate channel C to be the first channel CH1 is set.
A search routine for H (f, s) is executed (step 81).
0). If no candidate channel is found (step 804), this program ends.

When a candidate channel is found in the search routine 810, the found candidate channel CH (f,
After registering s) as the first channel CH1 of the g-th group,
Retrieval routine 8 for second channel CH2, CH3, CH4
20, 830 and 840 are sequentially executed, and step 802 is executed.
Return to As a result, the search for the candidate channel is repeated for the next set, and the program ends when the check is completed for all the channels.

FIG. 9 shows the details of the search routine 810 for the candidate channel CH (f, s). First, the value of the parameter f indicating the carrier frequency is incremented (step 811), and it is determined whether or not the upper limit value n has been exceeded (step 812). When the parameter f is equal to or less than the upper limit value n,
The candidate channel CH (f, s) is stored in the current management table 40.
In the updating process of 0, it is determined whether or not the channel is already registered as one of the candidate channels of another group (step 81).
4) If registered, return to step 811. If the channel CH (f, s) is not registered in the management table 400, the received radio wave of this channel is measured, and the channel CH (f, s) has a predetermined communication quality as in step 706 of FIG. It is determined whether or not the channel is a free channel provided (step 815).

If the channel CH (f, s) is a free channel having a predetermined communication quality, it is selected as a candidate channel (step 816), and the status code indicating the search result is changed to a status indicating the presence of the candidate channel. Then, if this channel CH (f, s) is not an empty channel having a predetermined communication quality, the process returns to the first step 811 to switch the carrier frequency.
Repeat the same check for the next channel.

If the value of the parameter s indicating the carrier frequency exceeds the upper limit n in step 812, the time slot number s is incremented and the parameter f of the carrier frequency is reset to the initial value (step 817).
If the updated time slot number s does not exceed the upper limit (4 in this example) (step 818), step 814 is executed. If the time slot number s exceeds the upper limit, the status check has been completed for all the channels. Therefore, the status code indicating the search result is changed to a status indicating no candidate channel (channel check completed). (Step 819), this routine ends. In the determination step 804 in FIG. 8, the presence or absence of a candidate channel is determined based on the status code.

FIG. 10 shows the details of the search routine 820 for the second channel CH2. The second channel CH2 is the first channel
The selection condition is that the channel CH1 and the carrier frequency are the same and only the time slot number is different. Since the time slot number of the first channel CH1 searched in the routine 810 is indicated by the value of the parameter s,
After setting the value of the parameter s to another parameter t, the value of the parameter t is incremented (step 821). It is determined whether or not the value of the parameter t has exceeded the upper limit value of the time slot number (step 822), and if not, the state of the channel CH (f, t) is checked (step 823). Channel CH (f,
If it is determined that t) is an empty channel having a predetermined communication quality, the channel CH (f, t) is changed to the second group of the g-th group
Register as channel CH2 and end this routine. If the channel CH (f, t) is not a free channel having a predetermined communication quality, step 821 is executed.
And the same check is repeated for the channel of the next time slot.

If the value of the parameter t exceeds the upper limit of the time slot number in step 822, that is, if the check has been completed for all time slots, the process returns to step 810 in FIG. Channel CH
Redo from the search of 1. In this case, since the value of the group number g is unchanged as before, the management table 40
At 0, the already registered g-th group first channel CH1 is rewritten with the newly searched channel number. In order to avoid re-searching for the second channel CH2 excessively, as shown in steps 825 and 826,
The number of returns to step 810 (the number of search repetitions) is counted, and if the number of times exceeds a predetermined threshold, it is determined that there is no second channel CH2 in the g group, and the next routine 830 is performed. You may make it go to.

FIG. 11 shows details of the search routine 830 for the second channel CH3. The second channel CH3 is the first channel
The selection condition is that the time slot is discontinuous with the time slot of the channel. First, the value of the current time slot number s is set to another parameter j (step 831a), and the value of the parameter j is incremented (step 832). Parameter j is the first channel C
The H1 time slot indicates a time slot having a discontinuous positional relationship. If the value of j exceeds 4,
It is determined that the check has been completed in all the time slots, and the process returns to step 810 in FIG. If the value of the parameter j is 4 or less, the carrier frequency F is selected at random, and the channel CH is selected in the same manner as in step 706 of FIG.
The state of (F, j) is checked (step 834).
If the channel CH (F, j) is a free channel that satisfies the predetermined communication quality, it is registered as the g-th group of the second channel CH3, and this routine ends.

If the channel CH (F, j) is not a free channel that satisfies the predetermined communication quality, it is determined whether or not the channel check has been completed for all carrier frequencies (step 836). If yes,
It returns to step 831b. If the decision result in the step 837 is NO, the carrier frequency is switched to the next frequency (step 837), and in a step 834, the state of the next channel is checked. When the check is completed in all the time slots, the number of times of return to step 810 (the number of repetitions of the search) is counted as shown in steps 838 and 839, and when the number of times exceeds a predetermined threshold value. May determine that there is no second channel CH3 in the g group, and may proceed to the next routine 840.

FIG. 12 shows the details of the search routine 840 for the second channel CH4. The second channel CH4 is an arbitrary channel having no restriction on carrier frequency and time slot. Therefore, the search routine 81 shown in FIG.
0, the g-th set of first channels CH
A vacant channel having a predetermined communication quality is searched from the next channel after the first channel. The execution result of the search routine 810 is determined (step 842), and the candidate channel CH (f, s) is determined.
Is found, this is set to the second channel CH of the g-th set.
Register as 4. If the candidate channel CH (f, s) is not found, it is determined that there is no second channel CH4 (step 844), and the routine 84 is performed with CH4 unregistered.
Exit 0.

When each base station receives a channel allocation request control message from the mobile terminal via the control channel, the base station determines whether the requesting mobile terminal is a single-channel type terminal based on the control information included in the control message. It is determined whether or not the terminal is a multi-channel type terminal. For a single-channel type mobile terminal, refer to the single-channel management table 300. For a multi-channel type mobile terminal, refer to the multi-channel management table 400. Is performed.

FIG. 13 shows a processing procedure of a channel assignment program for a single-channel mobile terminal. First, the value of the parameter s indicating the time slot number is set to the initial value 1 (step 901), and the communication quality of the candidate channel registered in the s-th slot of the management table 300 is measured (step 902). The communication quality in this case is determined by requesting the mobile terminal to transmit a dummy signal to the candidate channel via the control channel, and changing the reception state of the signal on the candidate channel to CIR (carrier to interference power ratio), It is measured by a known method such as CNR (carrier to noise power ratio) and BER (bit error rate).

If the candidate channel satisfies a predetermined communication quality, the candidate channel is deleted from the single channel table 300 (step 911), and processing for assigning the candidate channel to the mobile terminal is executed (step 911). After step 912), this program ends. If the candidate channel does not satisfy the predetermined communication quality, the value of the slot number s is updated (step 904),
It is determined whether candidate channels have been selected in all time slots (step 905). If the determination result is NO, the process returns to the communication quality measurement step 902. If the determination result is YES, one new candidate channel is randomly selected from all the channels shown in FIG. 4 (step 906), and the new candidate channel is subjected to the same method as in steps 902 to 903. Then, the communication quality is determined (step 907).

If the new candidate channel satisfies the predetermined communication quality, the process proceeds to step 911; otherwise, the next channel is designated as a new candidate channel in the order of channels (step 908), and the communication quality of step 907 is determined. Repeat the judgment. However, the candidate channels registered in the management table 300, for which the communication quality has already been checked, and the candidate channels for multi-channel communication registered in the management table 400 are excluded from the check targets in step 907. If it is determined that the communication quality has been checked for all the channels (step 909), the channel allocation effort to the mobile terminal is abandoned and the mobile terminal is treated as a call loss.

In the above embodiment, the initial value of the time slot number s is set to 1 and the communication quality of the registered candidate channels of TS1 to TS4 is checked on the management table 300 in the order of the time slot number. For example, the initial value of the time slot number s may be set at random, and the channel assignment may occur in an irregular time slot order. Further, the time slot number serving as a starting point may be changed each time a channel allocation request is generated so that candidate channels remain at discontinuous time slot positions in the management table 300 after channel allocation.

FIG. 14 shows a processing procedure of a channel assignment program for a multi-channel mobile terminal. First, the value of the parameter g indicating the group number in the multi-channel management table 400 is set to the initial value 0 (step 1).
001) Next, the value of the parameter g is incremented (step 1002). The value of the parameter g after the increase is compared with the upper limit (3 in this example) (step 100).
3) If the value does not exceed the upper limit, the above management table 4
The communication quality of the first channel CH1 of the g-th group of 00 is checked in the same manner as in steps 902 to 903 of FIG. 14 (step 1004). If the communication quality does not satisfy the predetermined condition, the process returns to step 1002 and the same operation is repeated for the next group number. If the communication quality of the first channel CH1 of the g-th group satisfies the predetermined condition, the channel CH1 is deleted (invalidated) from the management table 400 and then assigned to the mobile terminal (steps 1005 to 1006). .

If it is determined in step 1003 that the group number g
Exceeds the upper limit, it means that all of the first candidate channels CH1 registered in the management table 400 are not suitable for the mobile terminal currently targeted for channel allocation, and the process proceeds to step 1020. The first channel CH1 to be allocated to the mobile terminal is selected from all the channels shown in FIG. That is, step 1
After randomly selecting a candidate channel in 020, it is determined whether or not the candidate channel satisfies a predetermined communication quality (step 1021). If the predetermined communication quality is satisfied, the process proceeds to step 1006, and the candidate channel is allocated to the mobile terminal. If the communication quality of the candidate channel does not satisfy the predetermined condition, the next candidate channel is selected in order of channel number (step 1022).
Returning to step 1021, the communication quality check is repeated. If the check is completed for all the channels without finding any candidate channel that satisfies the predetermined communication quality, it is treated as a call loss (steps 1023 to 102).
4) End this program.

After allocating the first channel CH1 to the mobile terminal in step 1006, it is determined whether or not there is a second channel allocation request from the mobile terminal (step 1007).
If there is no request for the second channel, the program ends. When a request for the second channel is issued from the mobile terminal, the second channel CHi (CH1, CH2 or CH
Check whether 3) has been registered (step 100)
8). If the matching second channel CHi has been registered, the communication quality of this channel CHi is checked (step 1009). If the predetermined communication quality is satisfied, the channel CHi is deleted from the management table 400 (invalid). After that, it is allocated to the mobile terminal (steps 1010 to 1011), and this program is terminated.

When the second channel CHi conforming to the above request is not registered in the g-th group of the management table 400, or
If the second channel CHi that satisfies the above request does not satisfy the predetermined communication quality, the process proceeds to step 1030, and the same method as the routine 820, 830 or 840 described above is used to select from the channels shown in FIG. Select another second channel CHi that meets the above requirements. If no other second channel CHi that meets the request is found, the process proceeds to step 1024, and the channel request is treated as a call loss. If another second channel CHi that meets the request is found, the communication quality is checked (step 1).
032) If the predetermined communication quality is satisfied, the process proceeds to step 1011 to allocate the second channel CHi to the mobile terminal. If the second channel CHi does not satisfy the predetermined communication quality, the process returns to step 1030 to search for another channel CHi.

According to the above embodiment, a plurality of sets of candidate channels satisfying various constraints are registered in the multi-channel management table 400 in advance for channels for multi-channel communication with specific constraints between channels. This allows the base station that has received the channel assignment request from the mobile terminal to complete the channel assignment promptly with reference to the management table 400. Also, several sets of candidate channels for multi-channel communication with constraints are selected in advance, prior to channel selection for single-channel communication, and these are set in the multi-channel management table 400.
, The occurrence of call loss in multi-channel communication can be reduced.

Hereinafter, some modifications of the present invention will be described. The first modification is characterized in that when a multi-channel mobile terminal starts communication on a single channel, the assigned channel is switched to a communication channel registered in the single-channel management table during communication. The first terminal registered in the multi-channel management table 400 in the mobile terminal
When the base station 104 receives a call setup request after allocating the channel CH1 and before receiving a request for allocating the second channel CHi from the mobile terminal, the base station 104 establishes a connection between the mobile terminal and the destination device via the exchange 106. Establish communication connection between In this case, the communication channel CH1 assigned to the mobile terminal satisfies a special condition for multi-channel communication and is wasteful for single-channel communication. Therefore, the base station intentionally lowers the level of the transmission radio wave transmitted to the mobile terminal on the communication channel CH1 in order to release the communication channel CH1 to the mobile terminal. Since the communication quality of the communication channel CH1 is deteriorated due to the decrease in the transmission radio wave, the mobile terminal that has detected the deterioration requests the base station to change the channel.

In response to the channel change request, the base station executes the single channel communication channel assignment program shown in FIG.
A channel that replaces the communication channel CH1 is selected from the channel candidates registered in. Since the released communication channel CH1 can be returned to the management table multi-channel 400 again in the next multi-channel management table communication process, it is effective for a channel allocation request from a new multi-channel mobile terminal. Available.

The above-described channel switching due to a conscious decrease in transmission radio waves can be applied to a single-channel mobile terminal. That is, when a channel to be assigned is not found in response to a channel assignment request from a single-channel mobile terminal, the channel assignment program shown in FIG. If the multi-channel allocation program of FIG. 14 is executed instead of the step 910, the communication channel CH1 selected from the candidate channels registered in the multi-channel management table 400 is allocated to the single-channel mobile terminal. Can be. In this case, the second channel CH4 may be assigned instead of the communication channel CH1 required for multi-channel communication.

The first channel CH for single channel communication
1 is temporarily applied, and when the communication of another mobile terminal is completed, or when a channel for single-channel communication becomes free due to handover or the like, the communication quality of the communication channel CH1 is forcibly degraded. For example, the multi-channel management table 400 can be restored in the same procedure as described above. As described above, by temporarily lending the candidate channels registered for multi-channel communication, it is possible to avoid occurrence of a call loss of the single-channel mobile terminal.

FIG. 15 shows a second modification of the present invention.
1 of a program flowchart executed by a base station for the purpose of suppressing a multi-channel allocation request from a mobile terminal
Here is an example. It is determined whether or not a valid candidate channel CH1 remains in the multi-channel management table 400 (step 1101). If there is a valid candidate channel CH1, a first broadcast frame having contents permitting a multi-channel allocation request is determined. Is generated (step 1103); otherwise, a second broadcast frame is generated which allows only a single channel allocation request (step 110).
2), these broadcast frames are transmitted periodically (step 1104). The first and second broadcast frames are transmitted via a broadcast channel (a type of control channel) used by the base station to broadcast a channel configuration, a base station identifier, and the like to a mobile terminal located in its own cell. , Sent periodically.

The switching from the first broadcast frame to the second broadcast frame is performed in the multi-channel management table 4.
This may be performed before the remaining number of candidate channels CH1 of 00 becomes zero. For example, when the remaining number of candidate channels CH1 for multi-channel communication becomes one, switching from the first broadcast frame to the second broadcast frame is performed,
When two or more sets of candidate channels are registered in the management table 400 as a result of the release of the allocated channel due to the end of communication or handover, the second broadcast frame is switched to the first broadcast frame, and a multi-channel allocation request is issued. May be canceled. As described above, by broadcasting the status of the vacant channel in the base station to each mobile terminal, the issuance of a channel assignment request from the mobile terminal is suppressed, so that the occurrence of a call loss due to the shortage of the vacant channel can be prevented. This can prevent unnecessary channel allocation processing in the base station.

FIG. 16 shows a third modification of the present invention.
7 shows a flowchart of a determination routine for further selecting candidate channels to be registered in the management tables 300 and 400. In the management table update program described in FIG. 7 and FIGS. 8 to 12, when the received radio wave level of the check target channel is equal to or lower than a predetermined level, it is determined that the channel is an empty channel having predetermined communication quality, It is registered as a candidate channel in the management table 300 or 400. The determination routine of FIG. 16 is for checking the influence on each of the candidate channels selected according to the received radio wave level on other communication channels currently in use, and determining that the candidate channel is invalid if the degree of influence is large. For example, in the update program of the single channel management table shown in FIG.
If the candidate routine is determined to be invalid by the determination routine, a next candidate channel selection step is performed. Note that the above determination routine is
Similarly, in the multi-channel management table update program, step 805 in FIG. 8 and step 8 in FIG.
16, step 824 in FIG. 10, step 83 in FIG.
5, incorporated immediately before step 843 in FIG.

In FIG. 16, first, it is determined whether there is a mobile terminal communicating with the base station (step 1201). If there is no mobile terminal communicating with the base station, it is determined that the candidate channel is valid (step 1202). This routine ends. If there is a communicating mobile terminal, transmission of a dummy signal is started on the candidate channel (step 12).
03), select the first mobile terminal from among the communicating mobile terminals. Next, it is determined whether the check has been completed for all the mobile terminals in communication (step 120).
5) If the check is complete, proceed to step 1202; otherwise, request the selected mobile terminal to report the received signal level on the currently used channel via the control channel ( Step 12
06). The received signal level reported from the mobile terminal is compared with a threshold (step 1207). If the received signal level exceeds a predetermined level, the next mobile terminal is selected (step 1202).
9) Return to step 1205. If step 120
In step 7, if the received signal level is lower than the predetermined level, it is determined that the use of the candidate channel adversely affects communication on another channel, and the candidate channel is invalidated (step 1208).

According to the above embodiment, since a channel having a great effect on communication on another channel can be excluded from candidate channels, communication quality in a communication channel already allocated can be guaranteed, and channel switching due to a decrease in communication quality. And interruption of communication can be avoided. In order to determine the degree of influence on other channels, each mobile terminal to which the channel is assigned is made to report the received signal level in the communication channel, and based on this received level, each mobile terminal used in step 1207 is used. A threshold may be generated for each.
Further, the degree of influence on other channels may be determined based on other communication quality information other than the above-described reception level.

The validity of the candidate channel may be determined by using another mobile terminal that is not currently communicating. For example, the base station transmits a dummy signal to a candidate channel, and requests a mobile terminal that is presently not communicating in the wireless cell of the own station to measure the communication quality of the candidate channel via the control channel. . The mobile terminal that has received the measurement request transmits the dummy signal received from the candidate channel with a CI
Measure communication quality by R, CNR or BER, etc.
The measurement result is reported to the base station via the control channel. The base station can determine the validity of the candidate channel based on the measurement result received from the control channel. Conversely, the base station requests a mobile terminal that is not currently communicating to transmit a dummy signal to the candidate channel via the control channel, and the base station side performs CIR, CNR, or BE transmission.
The communication quality may be measured by R or the like, and the validity of the candidate channel may be determined.

The base station may request a plurality of mobile terminals to measure the communication quality of the same candidate channel. That is, the dummy signal transmitted to one candidate channel is measured by a plurality of mobile terminals, and the base station collects communication quality measurement results from the plurality of mobile terminals, and determines the worst communication quality among the candidate The validity of the candidate channel is determined by regarding the communication quality of the channel.

[0059]

As is apparent from the above description, according to the present invention, by allocating communication channel candidates to be assigned to a multi-channel type mobile terminal in a management table in advance, the channel allocation from the mobile terminal can be performed. Be able to respond quickly to requests. In addition, by securing in advance the candidate channel suitable for the channel conditions required by the multi-channel mobile terminal in the management table, it is possible to reduce the occurrence of a call loss due to a shortage of channels. In the embodiment, the first and second communication channels are allocated to the multi-channel mobile terminal. However, the present invention can be applied to a case where three or more communication channels are allocated to one mobile terminal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital cordless telephone system to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a base station.

FIG. 3 is a diagram for explaining a relationship between a carrier frequency and a time slot in multicarrier TDMA.

FIG. 4 is a diagram showing an example of a channel arrangement in multicarrier TDMA.

FIG. 5 is a diagram showing a single channel management table for registering candidate channels for single channel communication.

FIG. 6 is a diagram showing a multi-channel management table for registering candidate channels for multi-channel communication.

FIG. 7 is a flowchart illustrating a processing procedure of an update program of a single channel management table.

FIG. 8 is a flowchart showing a processing procedure of an update program of a multi-channel management table.

FIG. 9 is a flowchart showing details of a candidate channel CH (f, s) search routine 810 in FIG. 8;

FIG. 10 is a flowchart showing details of a candidate channel CH2 search routine 820 in FIG. 8;

FIG. 11 is a flowchart showing details of a search routine 830 for a candidate channel CH3 in FIG. 8;

FIG. 12 is a flowchart showing details of a candidate channel CH4 search routine 840 in FIG. 8;

FIG. 13 is a flowchart showing a processing procedure of a single channel communication channel assignment program.

FIG. 14 is a flowchart showing a processing procedure of a multi-channel communication channel assignment program.

FIG. 15 is a program flowchart showing an example of a process of transmitting base station information.

FIG. 16 is a program flowchart showing another embodiment for selecting a candidate channel.

[Explanation of symbols]

101: mobile terminal 104: base station 106: exchange
107 Other communication network 21-0 Control channel 20-1 to 20-n Communication channel 300 Single channel management table 400 Multichannel management table 501 Base station antenna 502 Radio section 503
Demodulation unit 504 Modulation unit 505 Channel codec 506 Transcodec 507 Wired network interface 508 Data demultiplexing unit 509 Channel quality measurement unit 510 ROM 511 Processor 512 RAM

Claims (10)

[Claims] A base station for a multi-carrier DTMA radio communication system using a plurality of carrier frequencies each having a plurality of time-division multiplexed time slots, each of which is specified by a carrier frequency and a time slot number. A management table memory in which at least one set of candidate channels for multi-channel communication selected from among the communication channels is registered, and when a channel allocation request is received from a multi-channel mobile terminal using a plurality of channels, A base station comprising: a channel assignment device that assigns a communication channel to the mobile terminal by referring to a table memory. 2. A set of candidate channels for multi-channel communication registered in the management table memory includes a first candidate channel and a predetermined channel in a channel arrangement determined by a carrier frequency and a time slot number. A plurality of second candidate channels satisfying a relative relationship, wherein the channel assignment device selects a plurality of channels having a relative relationship suitable for the mobile terminal from among a plurality of candidate channels included in the set of candidate channels. The base station according to claim 1, further comprising: a base station. 3. The communication device according to claim 2, wherein the channel allocation device is configured to select, from among the other communication channels not registered in the management table memory, when there is no candidate channel satisfying a predetermined communication quality to be allocated to the mobile terminal in the management table memory. 3. The base station according to claim 2, further comprising means for searching for a channel satisfying a predetermined communication quality to be assigned to the mobile terminal. 4. A base station for a multi-carrier DTMA radio communication system using a plurality of carrier frequencies each having a plurality of time-division multiplexed time slots, each of which is specified by a carrier frequency and a time slot number. A first management table in which at least one candidate channel for single-channel communication selected from among the communication channels is registered; and at least one set of multi-channel communication for multi-channel communication selected from among the plurality of communication channels. When a channel assignment request is received from a mobile terminal, a second management table in which candidate channels are registered, and one of the first and second management tables is selectively referred to according to the type of the mobile terminal. And a channel assignment device for assigning a communication channel to the mobile terminal. Chikyoku. 5. A set of candidate channels for multi-channel communication registered in the second management table, wherein the first candidate channel and the first candidate channel in a channel arrangement determined by a carrier frequency and a time slot number are different from each other by a predetermined number. And a plurality of second candidate channels satisfying the following relationship. When the channel assignment device receives a channel assignment request from a multi-channel mobile terminal using a plurality of channels, the channel assignment device is registered in the second management table. The method according to claim 4, further comprising means for selecting a plurality of channels having a relative relationship suitable for the multi-channel mobile terminal from among a plurality of candidate channels included in the set of candidate channels. base station. 6. The channel allocation device according to claim 1, wherein:
The method according to claim 4 or 5, further comprising means for jointly measuring the communication quality of the candidate channel selected from the second management table memory with the mobile terminal that has issued the channel assignment request. base station. 7. The first or second management table memory when there is no candidate channel in the first or second management table memory that satisfies a predetermined communication quality to be allocated to the mobile terminal. 7. A method for searching for a channel satisfying a predetermined communication quality to be assigned to the mobile terminal from other communication channels not registered in the mobile terminal. Base station as described. 8. A method for selectively using at least one of a plurality of carrier frequencies and at least one of a plurality of time slots time-division multiplexed to said carrier frequency between a base station and a mobile terminal. At least one set of candidates for multi-channel communication selected from a plurality of communication channels each specified by a carrier frequency and a time slot number. Registering a channel in a management table memory; and selecting a communication channel to be allocated to the mobile terminal by referring to the management table memory when receiving a channel allocation request from a multi-channel mobile terminal using a plurality of channels. And a communication channel comprising: Ri applied method. 9. In the registration step, a first candidate channel and a first candidate channel in a channel arrangement determined by a carrier frequency and a time slot number are set as the candidate channel set.
A plurality of second candidate channels satisfying a predetermined relative relationship with the candidate channel are selected, and in the assigning step, among the plurality of candidate channels included in the set of candidate channels, a relative relationship suitable for the mobile terminal is set. The method according to claim 8, wherein a plurality of channels are selected. 10. A method for selectively using at least one of a plurality of carrier frequencies and at least one of a plurality of time slots time-division multiplexed to said carrier frequency between a base station and a mobile terminal. Communication channel allocation method in a multi-carrier DTMA wireless communication system, wherein at least one candidate channel for single channel communication selected from a plurality of communication channels each specified by a carrier frequency and a time slot number. Registering in a first management table; registering at least one set of candidate channels for multi-channel communication selected from the plurality of communication channels in a second management table; When a request is received, the first, One of the second management table by referring selectively, the communication channel allocation method, which comprises the steps of allocating a communication channel to the mobile terminal.