JP2670757B2 - Channel allocation method for mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention searches a free channel by measuring the interference wave power of a plurality of channels by a base station, allocates the searched free channel, and performs communication between the base station and the mobile station. The present invention relates to a channel allocation method in a cellular mobile communication system.

[0002]

2. Description of the Related Art Conventionally, a cellular mobile communication system has a plurality of base stations arranged in a service area, and each mobile station receives a channel assignment from the nearest base station and communicates with the base station. In such a system, a range in which mobile stations connected to respective base stations are present is called a "cell". Although the number of channels is limited, it is configured so that a plurality of cells can be assigned the same channel at the same time and used to communicate with a large number of mobile stations.

Channel allocation methods in such a system include a "fixed channel allocation method" and a "dynamic channel allocation method". The fixed channel allocation method is a method in which a channel to be used in each cell is fixedly determined in advance so that interference does not occur between cells, and only that channel is allocated to each mobile station. On the other hand, in the dynamic channel allocation method, the base station measures the interference wave power of the channels allocated to the entire system, and the value satisfies a predetermined condition such as being less than a certain "threshold value". This is a method of selecting and allocating channels. According to this method, if the surrounding traffic is small, it is possible to allocate a large number of channels to a cell in which the traffic is concentrated, so that there is an advantage that the channel utilization efficiency is improved. On the other hand, there is a drawback that interference may occur between cells.

As one of the methods for improving the drawbacks of such a dynamic channel allocation method, "Chennel Segrega"
tion, a Distributed Adaptive Channel Allocation Sc
hemefor Mobile Communication Systems "(IEICE Trans
Actions, Vol. E-74, No. 6, June 1991) are known. In this method, each base station learns a channel in which interference is unlikely to occur from the past channel usage state and preferentially allocates the channel, thereby lowering the probability of occurrence of interference (hereinafter, “learning type”). Channel assignment method ").

In the above learning type channel assignment method, as a method of learning a channel in which interference is unlikely to occur, the interference wave power of each channel is measured periodically, and when the measured value is less than a certain threshold value. A method of increasing the priority of the channel and decreasing the priority of the channel when the measured value of the interference wave power is equal to or higher than a certain threshold value is often used. When such priority learning is performed, the interference wave power measuring device is required to measure the interference wave power of many channels.

Further, in general, in the dynamic channel allocation method, when a channel allocation request is generated, the time required for channel allocation is shortened. Therefore, the interference wave power of each channel is irrespective of whether the channel allocation request is generated or not. It is common practice to repeat the above measurement and search for an unused channel that is not used in the surrounding cells in advance. For this reason, the above-mentioned interference wave power measuring device is required.

[0007]

However, in the above-mentioned conventional "dynamic channel assignment method", as described above, the interference wave power measuring device is generally used for learning the priority and searching for an empty channel. , In a system with a large number of channels, the cycle of searching for free channels becomes long. Therefore, even if a free channel is found at the time of searching, it is already used in surrounding cells at the time of channel allocation, and there is an increase in cases where the required quality cannot be obtained even if a free channel searched beforehand is allocated. , There was a problem. The present invention has been made in order to solve the above-described problem, and does not increase the number of interference wave power measurement devices, has a short cycle of vacant channel search, and performs good quality communication with allocated channels. It is an object of the present invention to provide a channel allocation method for a mobile communication system capable of performing the above.

[0008]

In order to solve the above problems, a mobile communication system according to a first invention of the present invention comprises a plurality of cells, base stations installed in each of the cells, A plurality of mobile stations and a plurality of channels are provided, the base station communicates with the mobile station using the channel, and each of the base stations assigns a priority value to each of the channels. If the measured value is less than the first threshold value, the priority value is increased and the measured value is the first threshold value. When the value is equal to or more than the value, channel priority learning is performed to reduce the value of the priority, the interference wave powers of all the channels are periodically measured, and the channel whose measured value is less than the second threshold value is selected. Free channel search to record as free channel Performing a channel allocation request, wherein, when there is a request for channel allocation, a channel allocation method for a mobile communication system which selects and allocates, in order from the channels having higher priority, the channels having higher priorities, The power measurement is performed in order from the channel with the highest priority, and when the number of empty channels reaches a predetermined value, the empty channel search is repeated from the channel with the highest priority again. A mobile communication system according to a second aspect of the present invention includes a plurality of cells, a base station installed in each of the cells, a plurality of mobile stations, and a plurality of channels, The base station communicates with the mobile station using the channel, each base station sets a priority value for each of the channels, and periodically measures the interference wave power of all channels. If the measured value is less than the third threshold value, the priority value is increased, and if the measured value is greater than or equal to the third threshold value, the priority value is decreased. Priority learning is performed, the interference wave powers of all channels are periodically measured, and a channel allocation request is performed by performing a free channel search in which a channel whose measured value is less than the fourth threshold value is recorded as a free channel. If any, Channel allocation method for a mobile communication system, which selects and allocates in order from the channel having the highest priority among the channels having the highest priority, wherein the interference wave power measurement in the empty channel search is performed from the channel having the highest priority of the channel. When the number of empty channels reaches a predetermined value, the empty channel search is repeated from the channel with a higher priority again, and in the empty channel search, the interference wave power is measured for all the channels. The measured interference wave power value is recorded, and in the channel priority learning, the recorded interference wave power measurement value is used for the channel in which the interference wave power measurement value recorded in the empty channel search exists. Performing the priority learning using
The channel priority learning is performed by newly performing the interference wave power measurement for the channel for which the interference wave power measurement value recorded in the empty channel search does not exist.

[0009]

According to the channel allocation method of the mobile communication system according to the first aspect of the present invention having the above-mentioned configuration, the interference wave power in the empty channel search is measured in order from the channel having the highest priority. When the number of empty channels reaches the predetermined value, the empty channel search is repeated again from the channel having the highest priority. Further, according to the channel allocation method of the mobile communication system according to the second aspect of the present invention having the above configuration, the interference wave power measurement in the empty channel search is performed in order from the channel having the highest priority. , When the number of empty channels reaches a predetermined value, the empty channel search is repeated again from the channel with the highest priority, and in the empty channel search, the measurement is performed on all the channels for which the interference wave power is measured. The measured value of the interference wave power is recorded, and in the channel priority learning, the recorded interference wave power measurement value is used for the channel in which the interference wave power measurement value recorded in the empty channel search exists. The priority learning is performed and there is an interference wave power measurement value recorded in the empty channel search. The channel priority learning is performed by performing a new interference wave power measurement for have channels.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a mobile communication system that employs the channel allocation method according to the first embodiment of the present invention. As shown in the figure, the mobile communication system includes a plurality of cells 4
01, 402, 403, 404 and each of these cells 40
Base stations 411, 412, 41 installed in 1 to 404
3, 414 and a plurality of mobile stations 421, 422, 423.
424 and a plurality of channels CH1, CH2, ..., CHn
It is provided with. In this communication system, a large number of base stations are also arranged in the vicinity to provide services over a wide range, and a large number of mobile stations other than the above exist in each of the cells 401 to 404.

Each of the base stations 411 to 414 described above learns channel priorities, searches for vacant channels, and allocates channels. The free channel search is repeated in advance even if a communication request (channel allocation request) has not occurred. In the empty channel search, the interference wave power of each channel is measured, and the channel whose measured value is less than a certain threshold value T2 is recorded as an empty channel. At this time, the measurement value of the interference wave power of the idle channel is also recorded.

The learning of the channel priority is also repeated in advance regardless of whether or not a communication request is generated. In learning the priority of a channel, a priority value is set for each channel, the interference wave power of each channel is measured, and the measured value is less than another threshold T1 different from the above T2. At times, the priority value of the channel is increased, and when the measured interference wave power measurement value is equal to or higher than the threshold value T1, the priority value of the channel is decreased.

Channel allocation is performed when a mobile station communication request occurs. When a communication request occurs, the recorded empty channels are selected in descending order of priority, and the ratio between the power value of the signal from the mobile station of the communication partner and the interference wave power value of the selected channel is a predetermined threshold. The first channel having a value of T'or more is assigned to the mobile station for communication. Where the threshold T1 is the first threshold and
The threshold value T2 corresponds to the second threshold value.

FIG. 3 is a flow chart for explaining the channel priority learning operation in the first embodiment.
The base station determines a priority value for each of the channels. For example, a random value is set as the initial value. In learning the channel priority, as shown in FIG. 3, first, the priority order i is set to 1 (step 20
1), then the channel P with the i-th highest priority value
(I) is selected (step 202). Next, the interference wave power U (i) of the selected channel P (i) is measured (step 203), and the interference wave power measurement value U (i) is compared with a predetermined threshold value T1 (step 204). . As a result, if the interference wave power measurement value U (i) is less than the predetermined threshold value T1, the priority value is increased (step 20).
5), the interference wave power measurement value U (i) is a predetermined threshold value T1
In the above case, the priority value is increased (step 20).
6). Then, i is compared with the total number of channels Nchmax (step 207). As a result, i becomes Nchma
If it is less than x, 1 is added to i (step 208), the process returns to step 202 and the procedure after step 202 is repeated. In step 207, i is Nchmax.
If they are equal to each other, the priority values are arranged in descending order, the number of the channel having the i-th highest priority value is set to P (i) (step 209), and the process returns to step 201 and step 2
Steps 01 and after are repeated.

FIG. 2 is a flow chart for explaining the operation of empty channel search in the first embodiment. In learning the priority of empty channels, as shown in FIG. 2, the number Nv of empty channels is first set to 0 (step 10
1), the priority order i is set to 1 (step 102).
Next, the channel P (i) having the i-th highest priority value is selected (step 103). Next, the selected channel P
The interference wave power U (i) of (i) is measured (step 10
4) Compare the interference wave power measurement value U (i) with a predetermined threshold value T2 (step 105). As a result, when the interference wave power measurement value U (i) is less than the predetermined threshold value T2, the channel P (i) is recorded as a free channel (step 106), and 1 is added to the free channel number Nv (step 106). The process proceeds to step 108) and step 109. In step 105, the interference wave power measurement value U
If (i) is greater than or equal to the threshold T2, channel P (i)
Is recorded as an in-use channel (step 107), and the process proceeds to step 109.

Next, i is compared with the total number of channels Nchmax (step 109), and if i is equal to Nchmax, the process returns to step 101 and the procedure from step 101 is repeated. In step 109, i is N
If it is not equal to chmax, the process proceeds to the next step 110. In step 110, the number of free channels Nv and the predetermined value N
If v is compared with vmax and Nv is less than Nvmax, 1 is added to i (step 111), the process returns to step 103, and the procedure from step 103 is repeated. Step 110 above
If Nv is equal to Nvmax at
Is added (step 112), the channel P (i) is recorded as an in-use channel (step 113), and the process proceeds to step 114. Next, in step 114,
i is compared with Nchmax, and the procedure after step 112 is repeated while i is less than Nchmax, and the procedure after step 101 is repeated when i becomes equal to Nchmax.

As described above, in the channel allocating method of the first embodiment, the channels having higher priority are selected in order and the interference wave power value is measured to search for an empty channel. When Nvmax is reached, the search for an empty channel is repeated from the channel with the highest priority again.

When the channel allocation method of the first embodiment is used, for example, a channel with a high priority value (a channel with a high priority) in the base station 411 is first selected when it is an empty channel. Since the frequency of use is high, the interference wave power is often high in the surrounding base stations 412 and 413, and the priority value becomes small. Therefore, the high-priority channels are the base stations 412,
Since the frequency of use by the base station 413 is low, the base station 411 is likely to have an empty channel.

In the channel allocation method of the first embodiment, the channels are selected in order from the channel having the highest priority to search for an empty channel. Fewer channels to measure wave power. Therefore, according to this method, the time interval for searching for an empty channel is shortened, and the channel recorded as an empty channel is less likely to be in use by surrounding base stations at the time of channel assignment, Good communication quality can be obtained.

Next, a channel allocation method according to the second embodiment of the present invention will be described with reference to FIG. The channel allocation method of the second embodiment also has a system configuration as shown in FIG. 1, like the method of the first embodiment. FIG. 4 is a flow chart for explaining the operations of empty channel search and channel priority learning in the channel allocation method of the second embodiment. On the figure, step 301
˜316 is a part for performing a free channel search, and steps 317 to 327 are a part for performing channel priority learning.

As a free channel search procedure, first,
The number of free channels Nv is set to 0 (step 301), and the priority order i is set to 1 (step 302). Next, the channel P (i) having the i-th highest priority value is selected (step 303). Next, the interference wave power U (i) of the selected channel P (i) is measured (step 304) and the measured value U (i) is recorded (step 305).
Next, the interference wave power measurement value U (i) is compared with a predetermined threshold value T4 (step 306). As a result, when the interference wave power measurement value U (i) is less than the predetermined threshold value T4, the channel P (i) is recorded as a free channel (step 307), and 1 is added to the free channel number Nv ( The process proceeds to step 309) and step 310. In step 306, the interference wave power measurement value U
If (i) is greater than or equal to the threshold T4, channel P (i)
Is recorded as an in-use channel (step 308) and the process proceeds to step 310.

Next, i is compared with the total number of channels Nchmax (step 310), and i is the total number of channels Nchmax.
If it is equal to max, the process jumps to step 313 to set the measured channel number M to i. In step 310 above,
If i is less than Nchmax, the process proceeds to the next step 311. In step 311, the number of free channels Nv and the predetermined value N
When v is compared with vmax, and Nv is less than Nvmax, 1 is added to i (step 312), the process returns to step 303, and the procedure after step 303 is repeated. Step 311 above
When Nv reaches Nvmax in step 31, step 31
Move to 3. After execution of step 313, 1 is added to i (step 314), channel P (i) is recorded as a busy channel (step 315), and step 316
Move to Next, in step 316, i and N
Compare with chmax, and if i is less than Nchmax, step 3
The procedure from 14 onward is repeated, and when i becomes equal to Nchmax, the procedure goes to the channel priority learning procedure described below.

In the channel priority learning of the second embodiment, the priority order i is first set to 1 (step 31
7), then the channel P with the i-th highest priority value
(I) is selected (step 318). Next, i is compared with the number of measured channels M (step 319). As a result, if i is equal to or less than M, the interference wave power measurement value U (i) recorded in step 305 is set to the interference wave power value U.
If i is larger than M, the interference wave power value of the channel is newly measured there, and the measured value U (i) is taken as the interference wave power value U (step 32).
1) and the process moves to the next step 322. And then,
In step 322, the interference wave power value U determined as described above is compared with a predetermined threshold value T3. As a result, if U is less than T3, the priority value of the channel P (i) is increased (step 323), and if U is T3 or more, the priority value of the channel P (i) is decreased. (Step 324). Next, i and the total number of channels N
Compare chmax. As a result, if i is less than Nchmax, 1 is added to i (step 326), and step 318
Returning to step 318, the procedure after step 318 is repeated. If i is equal to Nchmax in step 325, the priority values are arranged in descending order, and the channel number having the i-th highest priority value is set to P (i) (step 3
27), the process returns to step 301, and the procedure after step 301 is repeated.

As described above, in the channel allocation method of the second embodiment, the interference wave power in the empty channel search is measured in order from the channel with the highest priority, and the number Nv of the empty channels becomes the predetermined value Nvmax. When it reaches, the empty channel search is repeated again from the channel with the highest priority. Then, in the idle channel search, the measured values of the interference power measured for all the channels for which the interference power was measured are recorded, and in the channel priority learning, the interference power measured in the empty channel search is recorded. For existing channels, priority learning is performed using the recorded interference wave power measurement values, and for channels for which there is no recorded interference wave power measurement value in the empty channel search, new interference wave power measurements are performed Perform priority learning.

According to the channel assignment method of the second embodiment, since the channel priority learning is performed using the interference wave power value measured in the empty channel search, the channel for which the interference wave power value was measured in the empty channel search is determined. Can omit the measurement of the interference wave power value in the channel priority. In this manner, the time for measuring the interference wave power for learning the channel priority can be shortened, so that the time interval for searching for an empty channel is shortened, and the channel recorded as an empty channel becomes nearby when the channel is allocated. It is unlikely that the base station is in use by the base station and the communication with good communication quality can be performed. In the second embodiment described above, the threshold value T3 corresponds to the third threshold value.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

For example, in the second embodiment, the priority learning is performed once every time the empty channel search is performed, but the priority learning may be performed a smaller number of times than the empty channel search. The priority learning may be performed once every time a free channel search is performed two or more times.

[0028]

As described above, according to the channel allocation method for the mobile communication system according to the first aspect of the present invention, the channels having the highest priority are selected in order to search for an empty channel. For this reason, the number of channels for measuring the interference wave power is small in order to search for a certain number of empty channels. Therefore, according to this method, the time interval for searching for an empty channel is shortened, and the channel recorded as an empty channel is less likely to be in use by surrounding base stations at the time of channel assignment, Good communication quality can be obtained. Further, according to the channel allocation method of the mobile communication system according to the second aspect of the present invention, since the channel priority learning is performed using the interference wave power value measured in the empty channel search, the interference wave power in the empty channel search is used. For the channel whose value is measured, the measurement of the interference wave power value in the channel priority can be omitted. In this manner, the time for measuring the interference wave power for learning the channel priority can be shortened, so that the time interval for searching for an empty channel is shortened, and the channel recorded as an empty channel becomes nearby when the channel is allocated. It is unlikely that the base station is in use by the base station and the communication with good communication quality can be performed.

[Brief description of the drawings]

FIG. 1 is a conceptual block diagram showing an overall configuration of a mobile communication system adopting a channel allocation method according to a first embodiment of the present invention.

[Fig. 2] Fig. 2 is a flow chart diagram explaining an operation of searching for a free channel in the mobile communication system shown in Fig. 1.

[Fig. 3] Fig. 3 is a flowchart diagram explaining an operation of channel priority learning in the mobile communication system shown in Fig. 1.

[Fig. 4] Fig. 4 is a flowchart diagram explaining operations of empty channel search and channel priority learning in the mobile communication system adopting the channel allocation method according to the second embodiment of the present invention.

[Explanation of symbols]

 101-327 Procedure 401-404 Cell 411-414 Base station 421-424 Mobile station CH1-CHn channel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-33033 (JP, A) JP-A-6-197079 (JP, A) JP-A-6-90205 (JP, A)

Claims (2)

(57) [Claims] 1. A plurality of cells, a base station installed in each of the cells, a plurality of mobile stations, and a plurality of channels, wherein the base station communicates with the mobile stations using the channels. Each of the base stations sets a priority value for each of the channels, periodically measures the interference wave power of all the channels, and the measured value is less than the first threshold value. In the case of, the priority value is increased, and when the measured value is equal to or more than the first threshold value, the priority value is decreased. An interference channel power is measured, a free channel search is performed in which a channel whose measured value is less than the second threshold value is recorded as an empty channel, and when there is a channel allocation request, among the empty channels, High priority A method for allocating a channel in a mobile communication system, which is sequentially selected and assigned from a channel, wherein the measurement of the interference wave power in the search for the vacant channel is performed in order from a channel having a higher priority of the channel, and the number of vacant channels is a predetermined value. Channel allocation method for a mobile communication system, wherein the empty channel search is repeated from a channel having a higher priority. 2. A plurality of cells, a base station installed in each of the cells, a plurality of mobile stations, and a plurality of channels, wherein the base station communicates with the mobile stations using the channels. Each of the base stations sets a priority value for each of the channels, periodically measures the interference wave power of all the channels, and the measured value is less than a third threshold value. In the case of, the priority value is increased, and when the measured value is equal to or more than the third threshold value, the priority value is decreased. The interference wave power is measured, a free channel search is performed in which a channel whose measured value is less than the fourth threshold value is recorded as a free channel, and when there is a channel allocation request, among the free channels, The high priority A channel allocation method of a mobile communication system, which is sequentially selected from the channels and allocated, wherein interference wave power measurement in the empty channel search is performed in order from the channel with the highest priority, and the number of empty channels is a predetermined value. When it reaches, the empty channel search is repeated again from the channel with the highest priority, and the measured values of the interference wave power are recorded for all the channels in which the interference wave power is measured in the empty channel search. However, in the channel priority learning, the priority learning is performed by using the recorded interference wave power measurement value for the channel in which the interference wave power measurement value recorded in the empty channel search exists, For channels for which there are no interfering power measurements recorded in the channel search Channel allocation method for a mobile communication system and performing the channel priority learning performed new interference wave power measurement.