JP4464845B2 - Allocation channel selection method and base station - Google Patents

Description

  The present invention relates to an allocation channel selection method and a base station, and more particularly to an allocation channel selection method and a base station in a wireless communication system using time division multiple access and frequency multiple access.

  As a wireless communication system that transmits and receives information by time-division multiplexing a plurality of channels in a predetermined slot using time division multiple access technology, for example, “Second Generation Cordless Telephone System RCR STD-28” of the Japan Radio Industry Association (Personal handyphone system: hereinafter referred to as PHS) (for example, see Non-Patent Document 1).

  A wireless communication system is a system in which a terminal moves and is used, and the state of a radio wave propagation path between the terminal and a base station changes from moment to moment depending on surrounding radio wave usage conditions. Therefore, the base station needs to select a channel to be allocated when the terminal performs communication. In the PHS, the above-mentioned standard states that “a communication carrier performs carrier sense within 2 seconds prior to transmission, and can be used over 4 frames or more in which the reception slot section (referred to as a 1-slot length section) is continuous ( It is specified that the peer slot is transmitted and used only after it is confirmed that it is free (see, for example, Section 3.2.15 (2) of Non-Patent Document 1).

  In the above standard, conditions for channels that can be used as communication carriers (carriers) (referred to as slots in the carriers) are determined, and which channels are used among the communication carriers that can be used. The determination of whether to do so is left to the specifications of each carrier and the device function of the device manufacturer, and various allocation channel selection methods have been proposed.

In the conventional technology, carrier sense of a call channel is always performed and a candidate to be assigned is selected so that a channel with less interference can be selected in a short time. When assigning, the carrier having the least interference among the candidate carriers is sensed for four frames, and it is determined whether or not the carrier is available.
"2nd generation cordless telephone system RCR STD-28", published by The Radio Industry Association, May 2004

  However, in the conventional method, it can be confirmed that the selected carrier is free for four consecutive frames in which carrier sense is performed, but it is not known whether the selected carrier is free in other time zones. For this reason, when a reflecting object such as a mobile station or an automobile moves, the level of the interference wave may change greatly and the call quality may deteriorate.

  In view of the above, it is an object of the present invention to provide an allocated channel selection method and a base station that allocate a carrier that is unlikely to receive interference. It is another object of the present invention to assign a carrier that is unlikely to receive interference by adding or updating software without changing the hardware of an existing system as much as possible.

  It is another object of the present invention to assign a channel that is at least two carriers away from the channel in use. The present invention assigns a channel that is at least two carriers away from the channel in use by determining whether or not each channel is in use based on the reception levels including the carriers before and after the channel to be assigned. Objective. Furthermore, an object of the present invention is to set priority and finely control carriers to be allocated based on reception levels including upper and lower carriers of channels that are candidates for allocation.

In order to solve the above problem, for example,
A radio channel control method for assigning a channel used for radio communication between a radio terminal and a radio base station,
An antenna for transmitting and receiving information wirelessly with a wireless terminal;
A reception level measurement unit for measuring a reception level via the antenna;
In a base station having a memory that stores the reception level, and a control device that controls allocation of channels used for wireless communication with a wireless terminal,
The control device of the base station measures the reception level of the radio signal received by the receiving radio device prior to assigning the call channel to the radio terminal, and stores it in the memory;
The control device arranges the reception levels stored in the memory in order of frequency for each time slot;
A step of determining a priority order for allocating channels using reception levels of five carriers including two carriers above and below candidate carriers as a determination material;
The control device includes a step of setting so as to allocate the carrier having the higher priority.

Some features of the present invention are exemplified below.
(1) In a radio communication base station that uses a time division multiple access scheme, an allocation candidate channel is determined when determining the allocation candidate channel for performing communication by confirming the presence or absence of interference (hereinafter referred to as carrier sense) before starting communication. Channels are determined based on reception level information for a maximum of 5 channels of channel allocation candidate channel number ± 1 channel (hereinafter referred to as adjacent channel) and channel allocation candidate channel number ± 2 channel (hereinafter referred to as next adjacent channel). .
(2) The next adjacent channel of the in-use channel whose interference wave reception level hardly changes on the time axis is selected.
(3) An allocation priority is assigned to the search channel to be allocated, and an allocation channel with a high priority is determined.
(4) When the same priority is present in a plurality of channels, an assigned channel having the lowest reception level is determined from the channels having the same priority.
(5) The lowest priority of the allocation priority is excluded from the determination of the adjacent channel and the next adjacent channel with respect to the search channel to be allocated, that is, only the level search of the search channel to be allocated is performed.

According to the first solution of the present invention,
In a wireless communication system that uses a carrier of a plurality of frequencies, time-division multiplexes each channel in a plurality of slots of each carrier, and transmits and receives information between a wireless terminal and a base station.
Measuring the reception level of the channel defined by the carrier and slot received from the terminal by the base station for each carrier and slot, and storing the measured reception level in a table corresponding to the identifier of the carrier and slot;
Sequentially setting search channels by selecting carrier and slot identifiers;
5 channels including a set search channel, two adjacent channels whose slots are the same as that of the search channel, and whose carriers are adjacent to each other above and below the carrier of the search channel, and two next adjacent channels that are adjacent above and below Reading a reception level corresponding to the carrier and slot identifier of each channel from the table;
The reception level of the read search channel and the reception levels of the two adjacent channels are equal to or lower than a predetermined threshold, and the read search channel, the two adjacent channels, and the two next adjacent channels An allocation channel selection method including: a step of selecting, as an allocation candidate channel, a search channel whose reception level is minimum in the search channel when the reception levels are arranged in carrier order, and allocating any of the allocation candidate channels to a radio terminal Is provided.

According to the second solution of the present invention,
A base station in a wireless communication system that uses carriers of a plurality of frequencies, time-division-multiplexes each channel in a plurality of slots of each carrier, and transmits and receives information between the wireless terminal and the base station,
An antenna for wirelessly communicating with the wireless terminal;
A reception level measuring unit that measures a reception level of a channel defined by the carrier and slot received from the terminal via the antenna for each carrier and slot;
A table storing reception levels measured by the reception level measurement unit corresponding to carrier and slot identifiers, and comprising a control device for allocating channels to radio terminals,
The controller is
Set the search channel sequentially by selecting the carrier and slot identifier,
5 channels including a set search channel, two adjacent channels whose slots are the same as that of the search channel, and whose carriers are adjacent to each other above and below the carrier of the search channel, and two next adjacent channels that are adjacent above and below For each channel, the reception level corresponding to the carrier and slot identifier of each channel is read from the table,
The reception level of the read search channel and the reception levels of the two adjacent channels are equal to or lower than a predetermined threshold, and the read search channel, the two adjacent channels, and the two next adjacent channels When the reception levels are arranged in the order of carriers, the base station is provided that selects the search channel whose reception level is minimum in the search channel as an allocation candidate channel and allocates one of the allocation candidate channels to the radio terminal.

  According to the present invention, it is possible to assign a carrier that is unlikely to receive interference in a short time. According to the present invention, it is possible to allocate a carrier with a low possibility of receiving interference only by adding or updating software without changing hardware of an existing system as much as possible.

  Further, according to the present invention, a channel separated by at least two carriers from the channel in use can be allocated. According to the present invention, a channel that is at least two carriers away from a channel in use is allocated by determining whether each channel is in use based on each reception level including carriers before and after the channel that is an allocation candidate. Can do. Furthermore, according to the present invention, it is possible to set priority and finely control the carriers to be allocated based on the reception levels including the carriers before and after the channel that is the allocation candidate.

  In the base station, as an optimum method for selecting an available channel, the reception level (or interference wave level) of a channel that can be used is measured, and not only the applicable carrier but also, for example, two carriers before and after that are judged and assigned. Finely control the carrier. Hereinafter, embodiments of radio channel selection according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system configuration diagram illustrating a configuration of a wireless communication system.
The wireless communication system 1 includes a plurality of terminals (PS: Personal Station) 30, a plurality of base stations (CS: Cell Station) 20 each having a zone 10 that is a radio wave arrival area to the terminal 30, and a plurality of base stations. 20 and a communication network 40 connected to the network 20. The wireless communication system 1 performs information transmission / reception between terminals 30 or between other terminals (not shown) connected to the terminal 30 and the communication network 40.

  In the figure, the zone 10-1 of the base station 20-1 overlaps with the zone 10-2 of another base station 20-2, and shows that the channel used by one interferes with the other. When the base station 20 assigns a channel to the terminal 30, the base station 20 measures the reception level of available radio resources, and determines a channel with low interference (a channel with a low measured interference wave level) between the base station 20 and the terminal 30. Select as the call channel used for communication.

FIG. 2 is a block diagram illustrating a configuration of the base station 20 provided in the wireless communication system.
The base station 20 includes an antenna 200 that transmits / receives information to / from the terminal 30 wirelessly, a combiner 210 that combines and / or separates information to be transmitted and / or received, a wireless signal converted into an electrical signal, etc. A transmission wireless device 220 and a reception wireless device 230 that process signals transmitted and received, a signal control device 240 that performs processing (for example, modulation and demodulation) of signals transmitted and received between the public network 40 and the terminal 30, and a public A wired line control device 250 that is an interface for communicating with the network 40 and a control device 260 that controls the entire base station 20 are included. These are connected by a control line 270, respectively.

  The signal control device 240 includes a reception level measurement unit 241 that measures the reception level of a frame (radio signal) received from the terminal 30. The reception level measurement unit 241 may be configured to be included in the reception wireless device 230. The reception level measurement unit 241 sequentially searches each slot and each carrier to measure the reception level, and stores the measured reception level in, for example, the memory 262 or the memory 262 in the own device.

  The control device 260 includes a control microcomputer (processor) 261, a memory 262 for storing data of the base station 20, and a program 263 for performing radio channel control such as channel allocation according to the present embodiment described in detail below. With. The program 263 controls the channels allocated to the terminals 30 based on the reception level data of a plurality of carriers measured by the reception level measurement unit 241. Specifically, control is performed such that a change in the reception level on the time axis is small and a carrier that is two or more carriers away from a carrier that is being used by another base station 20 is allocated, so that more stable call quality can be maintained. Details of channel assignment will be described later.

  Here, before explaining the details of the radio channel selection method of the present invention, the state change of the interference wave generated in the radio communication system 1 will be explained. 3, 9, and 10 are explanatory diagrams (1) to (3) for explaining state changes due to time transition of interference waves in the wireless communication system 1.

The diagram shown in FIG. 3 is an explanatory diagram for explaining the positional relationship between the base station 20 and the terminal 30. Here, an example in the following case will be described.
The terminal 30-1 is located far from the base station 20-1, and the terminal 30-3 is located close to the base station 20-1. The terminal 30-2 is between the terminal 30-1 and the terminal 30-3. Further, the terminal 30-1 is communicating with a base station 20-2 different from the base station 20-1 using the carrier f (FIG. 3: 150-1). Terminal 30-2 is communicating with base station 20-2 using carrier f + 1 (FIG. 3: 150-2) which is a carrier adjacent to carrier f. Furthermore, the terminal 30-3 is communicating with the base station 20-2 using f + 2 (FIG. 3: 150-3) which is a carrier away from the carrier f by two carriers. The base station 20-1 measures the interference wave (reception level) on all the permitted carriers including the carrier f (FIG. 3: 150-4), and selects an unused channel. Implement career sense.

  FIG. 9 is an explanatory diagram (2) illustrating a change in state of an interference wave due to time transition in the wireless communication system. At a certain time t0 (380), the base station 20-1 is communicating with the terminal 30-1 communicating with the carrier f (150-1) and the terminal communicating with the carrier f + 1 (150-2) as shown in FIG. The reception level of the carrier f (150-4) received from the three terminals 30 between the terminal 30-3 and the terminal 30-3 communicating with the carrier f + 2 (150-3) is X (dBμV) (FIG. 9: 310) is assumed to be the same.

  FIG. 9A shows the reception level with respect to the frequency when the base station 20-1 receives a radio wave emitted from the terminal 30-1 communicating with the base station 20-2 with the carrier f (150-1). It is a figure. Here, it is assumed that the reception level of the carrier f (150-4) having the same frequency as the carrier used by the base station 20-1 is X (dBμV).

  FIG.9 (b) shows the receiving level with respect to a frequency when the base station 20-1 receives the electromagnetic wave emitted from the terminal 30-2 communicating with the base station 20-2 by the carrier f + 1 (150-2). It is a figure. Here, it is assumed that the reception level of the carrier f (150-4) is X (dBμV).

  FIG.9 (c) shows the receiving level with respect to a frequency when the base station 20-1 receives the electromagnetic wave emitted from the terminal 30-3 communicating with the base station 20-2 by the carrier f + 2 (150-3). It is a figure. Here, it is assumed that the reception level of the carrier f (150-4) is X (dBμV).

  FIG. 10 is an explanatory diagram (3) illustrating a change in state of an interference wave due to time transition in the wireless communication system. An example of a change in reception level received by the base station 20-1 from each terminal 30 when the three terminals 30 each move one route 320 shown in FIG. FIG. 10 shows the time change of the reception level of the carrier f (150-4). The time when the reception level of the carrier f (150-4) received from each terminal 30 by the base station 20-1 is X (dBμV) (310) is t0 (330). This t0 corresponds to the time t0 in FIG.

  FIG. 10A shows that the base station 20-1 receives when the terminal 30-1 communicating with the base station 20-2 on the carrier f (150-1) moves along the route 320-1 shown in FIG. The change 340-1 in the reception level of the carrier f (150-4) is shown. 10B, the base station 20-1 when the terminal 30-2 communicating with the base station 20-2 on the carrier f + 1 (150-2) moves along the route 320-2 shown in FIG. Shows a change 340-2 in the reception level of the received carrier f (150-4). In FIG. 10C, the base station 20-1 receives when the terminal 30-3 communicating with the base station 20-2 on the carrier f + 2 (150-3) moves along the route 320-3 shown in FIG. The change 340-3 in the reception level of the carrier f (150-4) is shown.

  As shown in FIG. 10C, there is almost no change in the reception level of the carrier f (150-4) received from the terminal 30-3 communicating with the carrier f + 2 (150-3). On the other hand, as shown in FIGS. 10A and 10B, the interference waves (reception levels) from the terminal 30-1 communicating with the carrier f and the terminal 30-2 communicating with the carrier f + 1 are time-lapse. Depending on the situation, the level may increase, and the call quality is likely to be adversely affected.

  This means that a carrier that is two or more carriers away from the carrier in use can maintain stable call quality because the level of the interference wave hardly changes even if the terminal 30 in use moves. The allocation channel selection method according to the present embodiment is provided with a function of controlling the base station 20 so that a carrier that is two or more carriers away from the carrier in use can be selected.

  FIG. 4 is an explanatory diagram of processing of data read from the reception level measurement unit 241 by the program 263 provided in the base station 20. The program 263 provided in the base station 20 inputs reception level information of radio resources that are always unused from the reception level measurement unit 241 and stores them in the memory 262. The program 263 can be read and executed by the control microcomputer (processor) 261, for example. The program 263 provided in the base station 20 performs allocation channel selection processing based on the reception level stored in the memory 262 when receiving a request for connecting a call channel from the terminal 30. As described above, the allocation channel selection method of the present embodiment performs detailed control based on a plurality of reception level information in order to select a channel that is two or more carriers away from the channel in use.

  FIG. 4A is a configuration diagram of the first table stored in the memory 262. The first table 410 stores reception levels corresponding to carrier and slot identifiers. The first table 410 shown in FIG. 4A shows that the program 263 of the base station 20 stores the data input from the reception level measurement unit 241 in the memory 262 by arranging the data for each physical slot and in order of frequency. Yes. Whether or not the slot is being used by another base station 20 cannot be determined by just looking at one channel as described above with reference to FIG. Therefore, the program 263 tabulates the reception levels of 5 carriers including 2 carriers before and after each carrier of each physical slot and stores them in the second table 420 of the memory 262.

  4B and 4C are configuration diagrams of the second table 420. FIG. For example, reception levels L (N−2) to L (N + 2) of five carriers including two carriers before and after the center of one channel are stored in one entry. The second table 420 stores the priority. These reception levels and priorities can be stored for each carrier and slot identifier.

  For example, the carriers surrounded by the broken lines in FIGS. 4A and 4B will be described. Each reception level of the carriers 61 to 65 centering on the carrier 63 of SLOT1 is stored in one entry of the second table 420. Remembered. In this example, L (N) indicates the reception level 423 of the search channel, L (N−1) and L (N + 1) are the reception levels 422 and 424 of adjacent channels, L (N−2) and L (N + 2). Indicates reception levels 421 and 425 of the next adjacent channel. Similarly, reception levels of 5 carriers centering on each carrier are stored for each slot.

  Based on the five carrier data, the program 263 ranks the priorities to be assigned, for example, from 1 to 8, and stores the priority rank information in the second table 420 described above. An example of the second table 420 in which the priorities are stored is shown in FIG.

  FIG. 5 is a table showing conditions for determining the priority order. This table shows an example of conditions for the program 263 provided in the base station 20 to determine priorities to be assigned to all available radio resources based on a plurality of reception level information stored in the memory 262. In the drawings and in the following description, L (N): channel reception level (dBμV) to be determined, L (N−1): channel reception level (dBμV) obtained by subtracting the channel carrier to be determined by −1. ), L (N−2): channel reception level (dBμV) obtained by decrementing the carrier of the channel to be judged, L (N + 1): channel reception level (dBμV) obtained by adding +1 the carrier of the channel to be judged, L ( N + 2): channel reception level (dBμV) obtained by adding +2 to the carrier of the channel to be judged, L: reception level threshold value (dBμV) that is recognized as an empty channel, for example, 8 dBμV. The threshold value can be set in advance. Also, an appropriate value other than 8 dBμV may be used. The program 263 searches the second table 420 shown in FIG. 4 stored in the memory 262 for the presence / absence of channels matching the conditions in descending order of priority (P1 in the figure).

Each priority will be described with reference to FIG. In addition, the priority may set a more detailed priority besides the example shown below, and may set a simplified priority. Furthermore, the conditions may be changed as appropriate.
The channel with the highest priority is a channel in which neither the carrier to be judged nor the adjacent carrier is unused. The threshold value that is determined to be unused is a carrier within a value obtained by adding 6 dBμV to the reception level of the carrier of L and L or less. From these, it is determined that the terminal 30 being used does not exist in the range affected by interference, and only floor noise exists.

The priority 1, the priority 2, and the priority 3 are on condition that L (N) is equal to or less than a predetermined threshold L (first threshold) and the adjacent channel is not used. Specifically, it is as follows.
(1) The priority 1 is set so that the reception level L (N ± 1) of the adjacent channel is L or less.
L (N) ≦ L and L (N ± 1) ≦ L
(2) One of L (N ± 1) is L or less, and the other is L + 6 (second threshold) or less as priority 2.
L (N) ≦ L, L (N + 1) ≦ L, and L (N−1) ≦ L + 6, or
L (N) ≦ L, L (N−1) ≦ L, and L (N + 1) ≦ L + 6
(3) L (N ± 1) is L + 6 or less as priority 3.
L (N) ≦ L and L (N ± 1) ≦ L + 6
In FIG. 5, d. c. Represents don't care and indicates that the channel is not considered. In addition to the L + 6, the second threshold may be an appropriate value larger than the first threshold.

  The channel with the next highest priority is a channel in which the channel to be judged is unused (L (N) is L or less) and the adjacent carrier is not used by another terminal 30. That is, a channel that is at least two carriers away from the channel in use. The method for determining whether another terminal 30 is not using the adjacent carrier is based on the adjacent channel (for example, L (N-1)) of the channel being used (for example, L (N-2)) and the next adjacent channel. There is a level difference of about 6 dBμV or more between channels (for example, L (N)). The level L (N) of the channel to be judged is L or less, and one or both of the levels L (N ± 1) of the adjacent channels are more than L (N) +6 (third threshold), and the reception level of the channel to be judged When the reception levels of L (N) and front and rear two carriers are made into a bar graph, it is a condition that the channel to be judged is a valley on the bar graph. A valley on the bar graph can be determined, for example, by whether the reception level values are arranged in the order of carriers and are minimum or minimum in the channel to be determined. The third threshold value may be an appropriate value larger than L (N) other than L (N) +6.

Depending on the level of the adjacent channel level L (N ± 1) and the level L (N ± 2) of the next adjacent channel, the priority level is divided into priority level 4, priority level 5 and priority level 6. Specifically, it is as follows.
(4) Another terminal 30 is using a channel separated by two carriers in one direction on the frequency axis and the other direction is unused, and one of the levels L (N + 1) or L (N-1) of the adjacent channel is Priority 4 is set below the threshold L.
L (N) ≦ L, L (N + 1) ≦ L, and L (N) + 6 ≦ L (N−1) <L (N−2), or
L (N) ≦ L, L (N−1) ≦ L, and L (N) + 6 ≦ L (N + 1) <L (N + 2)
(5) Another terminal 30 is using a channel separated by two carriers in one direction on the frequency axis and the other direction is not used, and the level L (N + 1) or L (N-1) of the adjacent channel The priority is 5 when one is equal to or less than the threshold value L (N) +6.
L (N) ≦ L and L (N + 1) ≦ L (N) +6 and L (N) + 6 ≦ L (N−1) <L (N−2), or
L (N) ≦ L and L (N−1) ≦ L (N) +6 and L (N) + 6 ≦ L (N + 1) <L (N + 2)
(6) The priority is set to 6 when another terminal 30 is using a channel that is two carriers away in both directions on the frequency.
L (N) ≦ L and L (N) + 6 ≦ L (N−1) <L (N−2) <50 and L (N) + 6 ≦ L (N + 1) <L (N + 2) <50

The above-mentioned priority 6 is a condition in which at least the interference is not received in the channel to be judged. For example, when there are many terminals 30 in a narrow range and the traffic is high, it corresponds to the priority 6 There may be no channel to perform. For this case, priority 7 and priority 8 are defined as in the following example.
(7) The carrier to be judged is somewhat interfered, but the terminal 30 or the base station 20 that emits a radio wave that causes greater interference is a channel separated by two or more carriers, and the interference level of the channel separated by two carriers is , A channel that is 50 dBμV (fourth threshold) or less is assigned a priority of 7. Note that an appropriate value other than 50 dBμV can be used as the fourth threshold value.
L (N) + 6 ≦ L (N−1) <L (N−2) ≦ 50 and L (N) + 6 ≦ L (N + 1) <L (N + 2) ≦ 50
(8) The carrier to be judged has received some interference, but the terminal 30 or the base station 20 that emits a radio wave that causes greater interference is a channel separated by two or more carriers, and one of the channels separated by two carriers A channel whose level exceeds 50 dBμV is set as a priority level 8.
L (N) + 6 ≦ L (N−1) <L (N−2), L (N) + 6 ≦ L (N + 1) <L (N + 2), and 50 <L (N−2) or 50 <(N + 2)

  The program 263 searches from the higher priority, and if a matching channel is found, the program 263 is determined as an allocation candidate channel without performing a search after that priority (to the lower priority). Further, the priority is stored in the second table 420 corresponding to the determined allocation candidate channel.

  6 and 7 are flowcharts (1) and (2) in which the program 263 selects an allocation channel. With reference to FIG. 6 and FIG. 7, the flow of a process in which the program 263 of the base station 20 selects an allocation channel will be described.

  When the base station 20 receives a request for connecting a call channel (or assigning a channel) from the terminal 30, the program 263 activates an assigned channel selection process (S501). First, the program 263 periodically reads the reception level for each carrier and slot from the reception level measurement unit 241 and stores it in the first table 410 of the memory 262 corresponding to the carrier and slot identifier. The carrier and slot identifiers may use characters, symbols, etc. in addition to numbers. In addition to the carrier and slot identifiers, the reception level may be stored corresponding to identification information for identifying a channel.

The program 263 sorts reception level information of available radio resource channels in order of frequency for each physical slot as shown in FIG. 4A, for example (S502). Note that if the data has already been sorted and stored, the process of step S502 may be omitted. Next, the program 263 initializes the search channel (S503). For example, the program 263 sets the search channel as a preset carrier and slot channel. The program 263 initializes each slot and channel priority / highest priority information / highest priority number information (hereinafter referred to as the highest priority number) and stores it in the memory 262 (S504). For example, the priority of each slot and channel is stored in the second table 420 of the memory 262 corresponding to the slot and channel. If there is an unsearched channel, the program 263 proceeds to step S506, and if there is no unsearched channel, the program 263 proceeds to step S601 in FIG. 7 (S505).
For example, as described with reference to FIGS. 4 and 5 above, the program 263 determines the priority of the channel from the channel to be judged (search channel) and the reception level information of the five carriers before and after the carrier, Store (S506).

FIG. 8 is a detailed flowchart of step S506.
First, the program 263 sets the reception levels corresponding to the carrier and slot identifiers of each channel from the first table 410 for the five channels of the set search channel, two adjacent channels, and two next adjacent channels. Read (S701). Here, the adjacent channel refers to a channel whose slot is the same as that of the search channel and whose carriers are adjacent to each other above and below the carrier of the search channel. The next adjacent channel is a channel whose slot is the same as that of the search channel and the adjacent channel, and whose carrier is further adjacent to the adjacent channel in the vertical direction.

  Next, the program 263 sets a priority based on each read reception level (S703). For example, the program 263 sets priorities according to the conditions shown in FIG. The program 263 stores the set priority in the second table 420 corresponding to the carrier and slot (S705), and proceeds to step S507. In addition to the carrier and the slot, the priority may be set corresponding to an identifier for identifying the search channel.

  Returning to FIG. 6, the program 263 compares the determined priority of the carrier (search channel) with the highest priority in the channel searched so far (S507). The highest priority can be read from the memory 262. If the priority of the channel is higher than the highest priority, the highest priority is set to the priority of the channel and stored in the memory 262 (S508), and updated to a new priority. For example, the priority number is initialized to 1 and set in the memory 262 (S509).

  On the other hand, if the priority of the channel is the same as the highest priority in the channel searched so far in the comparison in step S507 (S507), 1 is added to the highest priority number and set in the memory 262 (S510). ). When the priority of the channel is lower than the highest priority in the comparison in step S507 (S507), the channel is not used and the information on the highest priority is assumed to be unchanged, and the process proceeds to step S511. The program 263 updates the search channel regardless of the comparison result in step S507 (S511). For example, the carrier of the search channel is set to the next carrier. The program 263 repeats the processing from step S506 to S511 until the search for all channels is completed (S505).

  When the search of all channels is completed (S505: No), the program 263 reads the information of the highest priority set in the memory 262, and the channels (assignment candidate channels) within the priority 8 that are effective priorities are read. The presence or absence is determined (S601). For example, if the read highest priority is 8 or less, the program 263 can determine that there is a channel with a priority of 8 or less. If there is no channel within the priority level 8 (S601), the program 263 transmits a message rejecting the allocation of the call channel to the terminal 30 (S602), and ends the process (S603). On the other hand, if it is determined in step S601 that there is a channel within the priority level 8 (S601), the program 263 reads the highest priority number set in the memory 262, and whether there are a plurality of highest priority channels. Is determined (S604).

When there is only one channel (when the highest priority number = 1), the program 263 refers to the second table 420 of the memory 262 and determines the channel having the same priority as the highest priority as an allocation candidate channel. Then, the process proceeds to step S606. On the other hand, when there are a plurality of channels (when the highest priority number is not 1), the program 263 receives from the entries having the same priority as the highest priority based on the information in the second table 420 of the memory 262. The channel with the lowest level L (N) value is selected (S605). When the value of L (N) is also the same (or when the difference is equal to or less than a predetermined value), the channel with the lowest value of L (N-1) + L (N + 1) is selected from among them. (S605). The base station 20 performs the selected channel assignment process on the terminal 30 (S606), and ends the process (S607).
Through the above-described allocation channel selection processing, the base station 20 can allocate a channel to the terminal 30 that can prevent a reception level from increasing during a call and can ensure stable call quality.

  In the above description, the reception levels of the five channels of the search channel and the upper and lower channels are read and the priority is determined based on each reception level. In some cases, the adjacent carrier and / or the next adjacent carrier is only in one direction. In this case, it is not necessary to read the reception levels of the five channels. For example, the reception levels of the number of channels that can be read may be read and the determination may be made based on those reception levels.

  For example, it can be used in industries related to wireless communication. In particular, it can be used in industries related to wireless communication systems using time division multiple access and frequency multiple access.

1 is a system configuration diagram showing a configuration of a wireless communication system. It is a block diagram which shows the structure of the base station with which a radio | wireless communications system is equipped. It is explanatory drawing (1) explaining the state change by the transition of the time of the interference wave in a radio | wireless communications system. It is explanatory drawing of the process of the data which the program with which the base station was provided input from the reception level measurement part. It is the table | surface which showed the conditions which determine the priority at the time of selecting an allocation channel. It is an operation | movement flowchart (the 1) which shows operation | movement of an allocation channel selection control program. It is an operation | movement flowchart (the 2) which shows operation | movement of an allocation channel selection control program. The detailed flowchart of step S506. It is explanatory drawing (2) explaining the state change by the transition of the time of the interference wave in a radio | wireless communications system. It is explanatory drawing (3) explaining the state change by the transition of the time of the interference wave in a radio | wireless communications system.

Explanation of symbols

1 wireless communication system 10 zone 20 base station (CS)
30 terminals (PS)
40 public network 150 wireless signal 200 antenna 210 coupler 220 transmission wireless device 230 reception wireless device 240 signal control device 241 reception level measurement unit 250 wired line control device 260 control device 261 control microcomputer (processor)
262 Memory 263 Program 270 Control line 320 Terminal movement path 410 First table 420 Second table 421, 425 Next adjacent channel 422, 424 Adjacent channel 423 Search channel

Claims (8)

In a wireless communication system that uses a carrier of a plurality of frequencies, time-division multiplexes each channel in a plurality of slots of each carrier, and transmits and receives information between a wireless terminal and a base station.
Measuring the reception level of the channel defined by the carrier and slot received from the terminal by the base station for each carrier and slot, and storing the measured reception level in a table corresponding to the identifier of the carrier and slot;
Sequentially setting search channels by selecting carrier and slot identifiers;
5 channels including a set search channel, two adjacent channels whose slots are the same as that of the search channel, and whose carriers are adjacent to each other above and below the carrier of the search channel, and two next adjacent channels that are adjacent above and below Reading a reception level corresponding to the carrier and slot identifier of each channel from the table;
The reception level of the read search channel and the reception levels of the two adjacent channels are equal to or lower than a predetermined threshold, and the read search channel, the two adjacent channels, and the two next adjacent channels An allocation channel selection method including: a step of selecting, as an allocation candidate channel, a search channel whose reception level is minimum in the search channel when the reception levels are arranged in carrier order, and allocating any of the allocation candidate channels to a radio terminal . Based on the read reception levels, the search channel reception level and the reception levels of the two adjacent channels are set to have a high priority for the search channel that is equal to or lower than a predetermined threshold, and the search channel and the two adjacent channels are adjacent. When the reception levels of the channel and the two next adjacent channels are arranged in the order of carrier, the search channel in which the reception level is minimum in the search channel is set as a low priority, and search channels other than these are set as lower priority, Setting the priority,
Storing the set priority in a second table corresponding to the carrier and slot identifier of the search channel;
The step of sequentially setting, the step of reading, the step of setting the priority, and the step of storing in the second table are executed for all or a predetermined number of carriers and slots. And further comprising steps
The assigning step comprises:
The allocation channel selection method according to claim 1, wherein a search channel with the highest priority is allocated to a wireless terminal with reference to the second table. The assigning step comprises:
The allocated channel selection method according to claim 2, further comprising: allocating a channel having the lowest reception level among the corresponding search channels to a wireless terminal when there are a plurality of search channels having the highest priority. The assigning step comprises:
When there are a plurality of search channels with the highest priority and the reception levels of the search channels are equal or nearly equal, the search channel with the lowest sum of reception levels of two adjacent channels is selected from the corresponding search channels. The allocation channel selection method according to claim 2, including allocation to a radio terminal. In the step of setting the priority,
The high priority is
The search channel reception level of the search channel is equal to or lower than the first threshold value, and the reception channels of the adjacent channels are equal to or lower than the first threshold value as the first priority,
It does not correspond to the first priority, the reception level of the search channel is less than or equal to the first threshold, one reception level of the adjacent channel is less than or equal to the first threshold, and the other reception level of the adjacent channel is The search channel that is less than or equal to the second threshold and greater than the first threshold is set as the second priority,
The search channels that do not correspond to the first and second priorities, the search channel reception level is equal to or lower than the first threshold, and the reception levels of both adjacent channels are equal to or lower than the second threshold are set to the third search channel. Priority is set as the priority of
The allocation channel selection method according to claim 2, wherein the priority is higher in the order of the first priority, the second priority, and the third priority. In the step of setting the priority,
The low priority is
The reception level of the search channel is less than or equal to the first threshold, and one reception level of the adjacent channel is less than or equal to the first threshold, and the other reception level of the adjacent channel is greater than the reception level of the search channel The search channel that is equal to or higher than the third threshold and is lower than the reception level of the next adjacent channel further adjacent to the adjacent channel is set as the fourth priority,
It does not correspond to the fourth priority, the reception level of the search channel is less than or equal to the first threshold, and one reception level of the adjacent channel is less than or equal to the third threshold, and the other reception of the adjacent channel The search channel whose level is equal to or higher than the third threshold and is lower than the reception level of the next adjacent channel further adjacent to the adjacent channel is set as the fifth priority,
It does not fall under the fourth and fifth priorities, the reception level of the search channel is less than or equal to the first threshold, and each of the reception levels of both adjacent channels is greater than or equal to the third threshold, The search channel that is lower than the reception level of the next adjacent channel that is further adjacent to each of the adjacent channels, and that the reception level of the next adjacent channel is less than a predetermined fourth threshold is set as the sixth priority. The priority is set,
The allocation channel selection method according to claim 2, wherein the priority is higher in the order of the fourth priority, the fifth priority, and the sixth priority. In the step of setting the priority,
The low priority is
The reception level of the search channel is less than or equal to the first threshold, and one reception level of the adjacent channel is less than or equal to the first threshold, and the other reception level of the adjacent channel is greater than the reception level of the search channel The search channel that is equal to or higher than the third threshold and is lower than the reception level of the next adjacent channel further adjacent to the adjacent channel is set as the fourth priority,
It does not correspond to the fourth priority, the reception level of the search channel is less than or equal to the first threshold, and one reception level of the adjacent channel is less than or equal to the third threshold, and the other reception of the adjacent channel The search channel whose level is equal to or higher than the third threshold and is lower than the reception level of the next adjacent channel further adjacent to the adjacent channel is set as the fifth priority,
It does not correspond to the fourth and fifth priorities, the reception level of the search channel is equal to or lower than the first threshold, and each of the reception levels of the adjacent channels is equal to or higher than the third threshold, The search channel that is lower than the reception level of the next adjacent channel that is further adjacent to each of the adjacent channels and that the reception level of the next adjacent channel is less than a predetermined fourth threshold is set as the sixth priority. ,
It does not fall under the fourth to sixth priorities, and both of the adjacent channels are each equal to or higher than the third threshold value and lower than the reception level of the next adjacent channel further adjacent to each of the adjacent channels, and The search channel whose reception level of the next adjacent channel is equal to or lower than the fourth threshold is set as the seventh priority,
It does not fall under the fourth to seventh priorities, and both of the adjacent channels are each equal to or higher than the third threshold value and lower than the reception level of the next adjacent channel further adjacent to each of the adjacent channels, and The priority is set with the search channel having the reception level of the next adjacent channel larger than the fourth threshold as the eighth priority,
The allocation channel selection method according to claim 2, wherein the priority is higher in the order of the fourth priority to the eighth priority. A base station in a wireless communication system that uses carriers of a plurality of frequencies, time-division-multiplexes each channel in a plurality of slots of each carrier, and transmits and receives information between the wireless terminal and the base station,
An antenna for wirelessly communicating with the wireless terminal;
A reception level measuring unit that measures a reception level of a channel defined by the carrier and slot received from the terminal via the antenna for each carrier and slot;
A table storing reception levels measured by the reception level measurement unit corresponding to carrier and slot identifiers, and comprising a control device for allocating channels to radio terminals,
The controller is
Set the search channel sequentially by selecting the carrier and slot identifier,
5 channels including a set search channel, two adjacent channels whose slots are the same as that of the search channel, and whose carriers are adjacent to each other above and below the carrier of the search channel, and two next adjacent channels that are adjacent above and below For each channel, the reception level corresponding to the carrier and slot identifier of each channel is read from the table,
The reception level of the read search channel and the reception levels of the two adjacent channels are equal to or lower than a predetermined threshold, and the read search channel, the two adjacent channels, and the two next adjacent channels The base station that selects a search channel whose reception level is minimum in the search channel when the reception levels are arranged in carrier order as an allocation candidate channel, and allocates one of the allocation candidate channels to a radio terminal.

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