JP2679413B2 - Channel allocation method for mobile communication system - Google Patents

Abstract

PURPOSE:To allocate a dynamic channel with less occurrence of interference in the mobile communication system of cellular system. CONSTITUTION:The mobile communication system consists of an exchange station 200, a base station 201, and a mobile station 202, the mobile station 202 during talking measures periodically a reception level of a connected base station and a peripheral base station and reports the level to the exchange station 200 via the connecting base station. A reception level ratio between the connecting base station and each peripheral base station is collected from the result of the reception level measurement and whether or not each peripheral base station generates the same channel interference or adjacent channel interference to the connection base station based on the distribution of the reception level ratio is decided and the operating channel of each base station 201 is decided based on the result of decision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a channel assignment system for a cellular mobile communication system.

[0002]

2. Description of the Related Art In a large-capacity mobile communication system such as a car telephone system, a service area is covered by a plurality of base stations, and channels having the same frequency (hereinafter referred to as "same channel") are used between base stations without interference. The frequency is effectively used by repeatedly using.
Such a system is called a cellular system.

There are roughly two types of methods for allocating channels used by each base station. One method is a method of predicting radio wave propagation characteristics in advance so as not to cause interference and allocating a fixed channel to each base station. This is called fixed channel assignment and is a common method in current car telephone systems. The other method is a method called dynamic channel allocation in which a channel that does not cause interference is selected for each communication and used. Although the dynamic channel allocation method has the drawback that the control method and device configuration are complicated, as long as there is no interference, any channel can be used freely, so the number of subscribers that can be accommodated is greater than that of fixed channel allocation. It has the advantage of increasing the number, and its adoption is also being considered for car telephone systems (Reference 1: R. Beck and
H. Panzer, "Strategies for"
Handover and Dynamic Chan
nelAllocation in Micro-ce
ill Mobile MobileRadio Syatem
s ", Conference Record of 39t
h IEEE Veh. Tech. Conf. Pp.
178-185, 1989. ).

In addition to channel allocation, in a mobile communication system of a cellular system, control called handoff (switching channels during communication) for switching a communication channel from a connected base station to an adjacent base station near a cell boundary is essential. . TDMA scheduled to be introduced in the near future
In a (time-division multiplexing) type digital mobile telephone system, a mobile station measures the reception level with respect to neighboring base stations by utilizing the idle time between transmission and reception time slots, and the result is measured together with the reception level of the connected base station. It has been decided to adopt a method (called Mobile Assisted Hand-off) of reporting to the base station being connected and activating the handoff based on this result. This reception level is measured by the BCCH (Broadcast) that is constantly transmitted by the base station.
Cast Control Channel (broadcast control channel). Also,
In order to suppress the measurement error due to the influence of fading, a plurality of measurement values obtained within a fixed time are averaged, and the average value is used as the SACCH (Slow Associated Content).
roll CHChannel: Report to the base station connected via a low speed associated control channel (Reference 2: David)
J. Targetett, "Handover-Enhan
ced capabilities of the GS
M system ”, Proceedings of
Digital Cellular Radio Co
nference, Hagen, FRG, October
r, 1988. ).

[0005]

In the dynamic channel allocation method, it is necessary to control the selection of a channel that is not affected by interference for each call.

[0006] Whether or not interference will occur for a combination of base stations over the entire service area will be thoroughly investigated in advance, and if the combination with the channel usage state of each base station is taken into consideration, the occurrence of interference will occur. You can select the channels that you do not want. However, this method requires a great deal of labor to grasp the interference state, and is impossible in reality.
Even if the interference status could be grasped, it would be necessary to review every time a new base station is installed or a new building is built around the base station. A method of measuring the reception level at both stations and selecting a channel free from interference is also conceivable. However, in this method, since the reception level cannot be measured for a sufficiently long time, a measurement error occurs and there is a risk of allocating a channel in which interference occurs. Moreover, the propagation state may change due to the movement of the mobile station, which may cause interference.

As described above, in the conventional dynamic channel allocation system, it is difficult to select a channel that is not affected by interference for each call.

It is an object of the present invention to provide a dynamic channel allocation system with less occurrence of interference in a cellular mobile communication system.

[0009]

A channel allocation system according to a first invention of the present application is a channel allocation system for a cellular mobile communication system in which a mobile station in a call measures the reception levels of a connected base station and peripheral base stations. In the mobile station, the reception level ratio between the connecting base station and each peripheral base station is totaled from the reception level measurement results, and the peripheral base stations are connected to the connecting base station from the distribution of the reception level ratio. Determines whether to cause co-channel interference or adjacent channel interference, and determines the channel used by each base station based on the result of the determination.

The channel allocation system of the second invention of the present application is the same as the channel allocation system of the first invention of the present application,
Prioritize the channels used by each base station, use from the channel with the highest priority, and if a certain channel can be used without interference, co-channel interference to the base station that used the channel. The priority of the channel in the base station determined to give is lowered, and if a certain channel cannot be used due to interference, the base station determined to give co-channel interference to the base station using the channel In the above, the priority of the channel is increased.

The channel allocation system of the third invention of the present application is the same as the channel allocation system of the first invention of the present application,
Prioritize the channels used by each base station, use the channels with the highest priority, and if a certain channel can be used without interference, do not give co-channel interference to the base station that used the channel. When the priority of the channel in one or more base stations selected in descending order of the base station that used the channel from among the base stations determined to be increased, and a certain channel cannot be used due to interference, , The priority of the channel in one or more base stations selected in order of proximity to the base station using the channel from among the base stations determined not to cause co-channel interference to the base station using the channel It is characterized by lowering.

A channel allocation system according to a fourth invention of the present application is the channel allocation system according to the first invention of the present application,
Prioritize adjacent channels to the adjacent channels of the base station that used the channel, if the channel used by each base station is given priority, and the channel with the highest priority is used, and if a certain channel can be used without interference. Decrease the priority of the adjacent channel of the channel in the base station determined to give the adjacent channel interference to the base station using the channel, if a certain channel could not be used due to interference, Increasing the priority of the adjacent channel of the channel in the base station using the channel, and increasing the priority of the adjacent channel of the channel in the base station determined to cause adjacent channel interference to the base station using the channel It is characterized by

The channel allocation system of the fifth invention of the present application is the same as the channel allocation system of the first invention of the present application,
Prioritize the channels used by each base station, use the channels with higher priority, and if a certain channel can be used without interference, do not give adjacent channel interference to the base station that used the channel. Among the base stations determined to be the above, the priority of the adjacent channel of the channel is increased in one or more base stations selected in the order close to the base station using the channel, and a certain channel cannot be used due to interference. In this case, the channel in one or more base stations selected in order of proximity to the base station using the channel from among the base stations determined not to cause adjacent channel interference to the base station using the channel It is characterized by lowering the priority of the adjacent channel of.

The channel allocation system of the sixth invention of the present application is the same as the channel allocation system of the first invention of the present application,
According to the reception level of the connecting base station in the mobile station, the reception level ratio between the connecting base station and each peripheral base station is divided into two or more and aggregated, and the connection is being made from the distribution of the reception level ratios. It is characterized in that whether or not each peripheral base station causes co-channel interference or adjacent channel interference with respect to the base station is determined for each peripheral base station, and a channel to be used is determined based on the result of the determination. And

In the digital car telephone system of the TDMA system as described above, if the measurement results of the reception levels of the connected base stations and the peripheral base stations in the mobile stations distributed over the entire cell are summed up, it is possible to calculate between the base stations. It is possible to easily monitor the interference state. Then, by determining the used channel based on this interference state and the channel use state of each base station, it is possible to suppress the occurrence of interference.

The first invention of the present application is that a desired wave-to-interference wave reception level ratio (hereinafter referred to as CIR) is calculated from the reception level of the connected base station and the reception level of a certain neighboring base station in the reception level report from each mobile station. Is calculated, and the probability density distribution is obtained for a certain number of CIR values. Then, from this probability density distribution, the probability that the CIR is equal to or greater than the minimum communicable CIR value is obtained. If this probability is smaller than the required location rate (for example, 90%), it is determined that interference will occur between the connected base station and its neighboring base stations, and simultaneous use of the same channel is prohibited. On the contrary, if the probability that the CIR is equal to or higher than the minimum communicable CIR value is higher than the required location ratio (90%), it is determined that no interference occurs between the connected base station and its neighboring base stations, and the same. Allow simultaneous use of channels. By making such a determination for each base station, the interference state between base stations, that is, the interference matrix is obtained, and if channel allocation is performed based on this interference matrix and the usage state of the channel in each base station, the interference It is possible to suppress the occurrence of interference.

Also in the dynamic channel allocation method, rather than randomly selecting a channel to be used, the same channel such as fixed channel allocation is used so that the same channel is used at the smallest reuse interval as much as possible. The frequency utilization probability is improved when the channel is selected so that the channel is used with the smallest reuse interval as much as possible. A channel segregation method has been proposed as a method for automatically allocating channels such that the same channel is frequently used at the minimum reuse interval (Reference 3: Yukitsuna Furuya e).
t. al. , "Channel Segregatio
n, A Distributed Adaptive
Channel Allocation Scheme
forMobile Communication
Systems ”, Proceedings of S
second Nrdic Seminar on Di
digital Land Mobile Radio C
communication, Stockholm Sw
eden, October 1986. ). The segregation method assigns priority to channels at each base station, assigns channels in order from the highest priority, raises the priority of the channel if it is available for each call, and prioritizes the channel if it is unavailable. Is a method for automatically forming a repetitive pattern such that the number of times that the same channel is used at the minimum reuse interval is increased by decreasing. The segregation method of Reference 3 is a method in which each base station assigns a priority to each other independently, but a method of simultaneously updating the priorities of a plurality of base stations based on the interference state between the base stations is also conceivable. For example, when raising the priority of channel n in a certain base station, the priority of channel n in the base station which causes co-channel interference to this base station is lowered. Also, the priority of the channel n in the base station that does not cause co-channel interference to this base station is increased. By doing so, it is possible to quickly and surely form a repeating pattern having a high frequency utilization probability as compared with the conventional segregation method. In the second invention of the present application, when the priority of the channel n in a certain base station in the segregation method is raised, a base station which gives co-channel interference to the base station is obtained by the method of the first invention of the present application, and , The priority of channel n in the base station is decreased. Further, when lowering the priority of channel n in a certain base station, a base station that causes co-channel interference to that base station is obtained by the method of the first invention of the present application, and the priority of channel n in these base stations is raised. . In the third invention of the present application, when the priority of the channel n in a base station in the segregation system is raised,
A base station that does not give co-channel interference to the base station is obtained by the method of the first invention of the present application, and one or more base stations are selected from these base stations in the order of proximity to the base station in question. Increase the priority of channel n in the base station. When lowering the priority of channel n in a certain base station, a base station that does not cause co-channel interference to the base station is obtained by the method of the first invention of the present application, and the base station in question is selected from these base stations. One or more base stations are selected in the order close to, and the priority of channel n in those base stations is lowered. By doing so, the possibility that the channel n is used at the minimum reuse interval increases, and thus the frequency utilization rate improves.

In the interleaved channel arrangement in which the number of channels is doubled by using the same number of channels in which the frequency is shifted by 1/2 of the channel interval in addition to the normal channel arrangement, the same channel is used. In addition, the adjacent channel cannot be used in the same base station or the adjacent base station (Reference 4: VH Mac Donald,
"Advanced Mobile Phone Se
rvice: TheCellular Concep
t "The Bell System Techni
cal Journal, Vol. 58, No. 1, J
annuary1979. ). If the priorities of adjacent channels in a plurality of base stations are updated at the same time by utilizing the interference state between the base stations, iterative patterns that satisfy the constraint condition of the interleaved channel arrangement can be formed. In the fourth invention of the present application, when the priority of the channel n in a certain base station in the segregation method is raised, a base station which causes adjacent channel interference to the base station is obtained by the method of the first invention of the present application, and Channel n at each base station
N-1 and n, which are adjacent channels of
Decrease the priority of +1. Further, when lowering the priority of channel n in a certain base station, a base station that causes adjacent channel interference to that base station is obtained by the method of the first invention of the present application, and is the adjacent channel of channel n in these base stations. Increase the priority of channel n-1 and channel n + 1. In the fifth invention of the present application, when the priority of the channel n in a certain base station in the segregation method is raised, a base station that does not cause adjacent channel interference to the base station is obtained by the method of the first invention of the present application, One or more base stations are selected from these base stations in the order of proximity to the base station in question, and the priority of the adjacent channels n-1 and n + 1 of the channel n in those base stations is raised. When lowering the priority of channel n in a certain base station, a base station which does not cause adjacent channel interference to the base station is obtained by the method of the first invention of the present application, and the base station in question is selected from these base stations. One or more base stations are selected in the order of close to, and channel n−1 and channel n +, which are adjacent channels to channel n in those base stations.
Lower the priority of 1. In the case of interleaved channel arrangement, by doing so, a repetitive pattern that also satisfies the constraint on adjacent channels is automatically formed.

The Leus partitioning is a technique in which a cell is divided into donuts according to the distance from the base station and different channels are assigned to the respective divided cells. In this way, it is possible to shorten the repetition distance of the same channel by utilizing the loose interference condition between the inner cells,
Overall frequency utilization efficiency is improved (Reference 5: SWH
alpern, “Reuse partitionin”
g in cellular systems ”, Co
nference Record of 33rd I
EEE Veh. Tech. Conf. Pp. 322
-327, 1983. ).

The channel allocation suitable for this Leus partitioning can also be carried out by utilizing the interference state between the base stations based on the reception level measurement result at the mobile station. In the sixth invention of the present application, when the probability density distribution of the desired to interfering wave reception level ratio CIR is obtained from the reception level of the connected base station and the reception level of a certain neighboring base station as in the first invention of the present application, , A plurality of probability density distributions are obtained according to the value of the reception level of the connected base station. For example, when performing the Leuse partitioning by dividing the cell into inner and outer parts, if the reception level of the connected base station is higher than a certain level, it is determined that the mobile station is in the inner cell, and the mobile station The probability density distribution of CIR in the cell is updated, and the interference matrix for the inner cell is obtained. If the reception level of the connecting base station is lower than a certain level, it is determined that the mobile station is in the outer cell, and the probability density distribution of CIR when the mobile station is in the outer cell is updated,
Find the interference matrix for the inner cells. If the received level of the connected base station is lower than a certain level, it is determined that the mobile station is in the outer cell, the probability density distribution of the CIR when the mobile station is in the outer cell is updated, and the outer cell is updated. For the interference matrix for. If two types of interference matrices are used according to the position of the mobile station and channel allocation is performed, it is possible to suppress the occurrence of interference even when the Leus partitioning is performed.

By the above-described methods, it is possible to provide a dynamic channel allocation method in a mobile communication system of a cellular system with less interference and high frequency utilization efficiency.

[0022]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an example of the configuration of a mobile communication system in which the channel allocation system of the present invention is used. This mobile communication system is composed of a switching station 200, a base station 201, and a mobile station 202. A mobile station in a call periodically measures the reception levels of a base station being connected and peripheral base stations, and is being connected. Report to the exchange through the base station. The switching center activates a handoff to another base station based on this reception level. The method of measuring the reception level and reporting the result is described in detail in Document 2 above.

FIG. 3 shows the format of the reception level report. LEV DL (300) is the reception level of the connected base station in the mobile station, ID _(n) (301 to 306) is the identifier of the peripheral base station, and LEV _(n) (307 to 312) is the peripheral base station of the mobile station. It is the reception level. In this embodiment, among the neighboring base stations, the reception levels of 6 base stations are reported in descending order of reception level. The number of peripheral base stations to be measured can be selected as an arbitrary value, but a larger number can create a more detailed interference matrix. Each reception level is displayed in decibels.

FIG. 1 is a flow chart for explaining a method for the switching station to update the interference matrix indicating the interference state between the base stations from the reception level report of each mobile station in the channel allocation system of the first invention. is there. When the exchange receives the reception level report in the format of FIG. 3 via the connected base station (referred to as BS _i ) (100), the variable n is set to 1 (101) and the connected base station BS _{i is set.} Reception level L
The difference between the reception level LEV _(n) of the peripheral base station (denoted by BS _{j )} indicated by EV DL and ID _(n) , that is, the desired wave-to-interference wave power ratio CIR is assigned to the variable CIR NEW (10
2). The exchange stores a fixed number of CIR values for each combination of base stations, discards the oldest CIR value each time a new CIR NIW is obtained, and replaces it with the CIR NIW value (103). Next, the probability density distribution of the set of CIR values of the base station BS _{i for} the base station BS _j is obtained (104). Further, the probability P ₁ that the CIR is equal to or greater than the threshold value 1 is obtained from this probability density distribution (105). Threshold 1
Is selected as the minimum value of CIR with which communication is possible, the probability P
₁ indicates the percentage of places where calls can be made within the cell. Then, the probability P ₁ is compared with the location rate required by the quality regulation (106). In this embodiment, the required location rate is 90%.
As shown in FIG. 4A, when the probability P ₁ that the CIR is 1 or more is 90% or more, the connected base station BS _i and the peripheral base station BS _j use the same channel or the adjacent channel. Also determines that no interference occurs, and writes a symbol (○) indicating that the same and adjacent channels can be used in the columns of the desired station BS _i and the interference station BS _j of the interference matrix shown in FIG. 5 ( 107). Further, as shown in FIG. 4B, if the probability P ₁ that the CIR is greater than or equal to the threshold value 1 is less than 90%, interference will occur if the connected base station BS _i and the peripheral base station BS _j use the same channel. Determined to occur. Even a base station that gives co-channel interference may be able to use the adjacent channel, so the probability P ₂ that the CIR becomes equal to or greater than the threshold value 2 is calculated (108). Threshold 2
Is smaller than the threshold value 1 by the margin due to the frequency difference. Then, this probability P ₂ is compared with the location rate 90% required by the quality regulation (109). If the probability P ₂ is 90% or more, it is determined that no interference occurs even if the connecting base station BS _i and the peripheral base station BS _j use adjacent channels, and the desired station BS _i and the interference in the interference matrix are determined. In the station BS _j column, write a symbol (Δ) indicating that the same channel cannot be used and the adjacent channel can be used (1
10). If the probability P _{2 is} also less than 90%, it is determined that interference will occur even if the connecting base station BS _i and the neighboring base station BS _j use adjacent channels, and the desired station BS _i and the interfering station in the interference matrix are determined. A symbol (x) indicating that the same channel and the adjacent channel cannot be used is written in the column of BS _j (111). Connected base station BS _i and peripheral base station B
When the update of the interference matrix for S _j is completed, 1 is added to the variable n (113), and if the variable n is 6 or less,
The control from 102 to 112 is repeated. When the variable n exceeds 6, the process ends and the next reception level report is prepared (113). By doing so, the interference matrix showing the interference state between the mobile stations can be automatically created from the reception level report of the mobile stations.

When a channel is newly allocated by calling, terminating a call, handoff or the like of the mobile station, a channel that does not cause interference is surely selected based on this interference matrix and the usage state of the channel in each base station. You can For example, when a new channel is assigned to the base station BS _i , the base stations marked with x in the interference matrix shown in FIG. 5, that is, BS _h , BS _i , B
Select the same channels and adjacent channels not used in S _j , BS _k and BS _l , and select the base stations marked with Δ, that is, the channels that adjacent channels are not used in BS _g , BS _m and BS _n . To do so. In addition to dynamically allocating channels as in the present embodiment, channel allocation based on the interference matrix is set to 1
It may be fixed in units such as days or weeks.

FIG. 6 is a flow chart for explaining the channel allocation system of the second invention. In this channel allocation method, a so-called segregation method is employed in which each base station assigns a priority to each channel, and when a request is made, a channel having a higher priority is used. The segregation method is described in detail in Reference 3. Also, all prioritization shall be carried out collectively by the exchange. Further, the switching center manages an interference matrix showing an interference state between the base stations by the method of the first invention.

When there is a channel allocation request to the base station BS _i , the exchange selects the channel n having the highest priority in the base station BS _i (600), and selects the interference matrix and the channel n in the neighboring base stations. It is determined whether or not the channel n can be used based on the usage state (601).
If it is available, the priority P _(n) of the channel n in the base station BS _i is increased (602), and the base station which causes the co-channel interference to the base station BS _i is obtained from the interference matrix. Decrease priority P _(n) (6
03), the call is started (604). If it cannot be used, the priority P _(n) of the channel n in the base station BS _i is reduced (605), and the base stations that give the co-channel interference to the base station BS _i are obtained from the interference matrix. The priority P _{(n) in} is increased (606) and it is checked whether channel n is the last channel available in the base station BS _i (607). If the channel n is the last channel, the call is lost (608). If it is not the last channel, the channel with the next highest priority is selected, this is set as channel n (609), and the process returns to the control for checking availability again (601). In the present embodiment, both the priority increase (606) and the priority decrease (603) in the base station that gives the co-channel interference are performed, but only one of them may be performed.

FIG. 7 is a flow chart for explaining the channel allocation system of the third invention. Similar to the second invention,
The exchange centrally manages the channel priority and interference matrix in each base station.

When there is a channel allocation request to the base station BS _i , the switching center selects the channel n having the highest priority in the base station BS _i (700), and the interference matrix and the usage state of the channel n in the neighboring base stations are selected. It is determined whether the channel n is available based on (701). If it can be used, the priority P _(n) of the channel n in the base station BS _i is increased (702), and the base station that does not cause the co-channel interference to the base station BS _i is obtained from the interference matrix. Only N base stations close to the station BS _i are obtained, and the priority P _(n) in these base stations is increased (7
03), the call is started (704). Base stations close to the base station BS _i can be inferred from the CIR distribution.
That is, the smaller the probability P ₁ that the threshold value is 1 or more, the base station BS
_It can be determined that it is close to _i . The value of N is arbitrary, but is preferably a value such that the selected base station has a circular shape surrounding the base station BS _i . If it cannot be used, the priority P _(n) of the channel n in the base station BS _i is decreased (705),
Determined base station BS _i base station which does not give the same channel interference from interference matrix, the base station near the base station BS _i look only N stations, reduces the priority P _(n) in these base stations from among the (706), channel n is the base station BS
Check if it is the last channel available in _i (707). If channel n is the last channel, the call is lost (708). If it is not the last channel, the channel with the next highest priority is selected, this is set as channel n (709), and the process returns to the control for checking availability again (70).
1). In this embodiment, both the priority increase (703) and the priority decrease (706) in the base station that does not give the co-channel interference are performed, but only one of them may be performed.

FIG. 8 is a flow chart for explaining the channel allocation system of the fourth invention. Similar to the second invention,
The exchange centrally manages the channel priority and interference matrix in each base station. It also uses an interleaved channel arrangement.

When there is a channel allocation request to the base station BS _i , the switching center selects the channel n having the highest priority in the base station BS _i (800), and the interference matrix and the usage state of the channel n in the neighboring base stations are selected. It is determined whether the channel n is available based on (801). If it is available, the priority P _(n) of the channel n in the base station BS _i is increased (802), and the priority P of the channel n−1 and the channel n + 1 which are the adjacent channels of the channel n in the base station BS _i are increased. _(n-1) , P _{(n + 1)} are decreased (803), the base stations that give adjacent channel interference to the base station BS _i are obtained from the interference matrix, and the priority P _(n-1) in these base stations is obtained. , P _{(n + 1)} is reduced (804),
A call is started (805). If it cannot be used, the priority P _(n) of the channel n in the base station BS _i is decreased (806), and the priorities of the channel n−1 and the channel n + 1 which are the adjacent channels of the channel n in the base station BS _i are decreased. P _(n-1) and P _{(n + 1)} are increased (807), and the base station B
A base station which gives adjacent channel interference to S _i is obtained from the interference matrix, the priorities P _(n-1) and P _{(n + 1)} in these base stations are increased (808), and channel n is changed to base station BS _i. Check if it is the last channel available in (809). If channel n is the last channel, the call is lost (810). If it is not the last channel, the channel with the next highest priority is selected, this is set as channel n (811), and the process returns to the control for checking the availability again (801). In this embodiment, the priority is increased in the base station which gives the adjacent channel interference (808). Decrease (8
Although both 04) are performed, only one of them may be performed.

FIG. 9 is a flow chart for explaining the channel allocation system of the fifth invention. Similar to the second invention,
The exchange centrally manages the channel priority and interference matrix in each base station. It also uses an interleaved channel arrangement.

When the base station BS _i has a channel allocation request, the switching center selects the channel n having the highest priority in the base station BS _i (900), and determines the interference matrix and the use state of the channel n in the neighboring base stations. Based on this, it is determined whether channel n is available (901). If available, the priority P _(n) of the channel n in the base station BS _i is increased (902), and the priority P of the adjacent channels n-1 and n + 1 of the channel n in the base station BS _i is increased. _(n-1) and P _{(n + 1)} are decreased (9
03), a base station that does not cause adjacent channel interference to the base station BS _i is obtained from the interference matrix, and the base station B
Only N base stations close to S _i are obtained, the priorities P _(n-1) and P _{(n + 1)} in these base stations are increased (904), and a call is started (905). Base stations close to the base station BS _i can be inferred from the CIR distribution. That is, the smaller the probability P ₁ that the threshold value is 1 or more, the closer to the base station BS _i it can be determined. The value of N is arbitrary, but is preferably a value such that the selected base station has a circular shape surrounding the base station BS _i . If it cannot be used, the priority P _(n) of the channel n in the base station BS _i is reduced (906), and the base station B
Priority P _(n-1) , P of channel n-1 and channel n + 1 which are adjacent channels of channel n in S _{i
(n + 1)} is increased (907), a base station that does not cause adjacent channel interference to the base station BS _i is obtained from the interference matrix,
Of these, only N stations are searched for base stations close to the base station BS _i ,
The priorities P _(n-1) and P _{(n + 1)} at these base stations are decreased (908) and it is checked whether channel n is the last channel available at base station BS _i (909).
If channel n is the last channel, the call is lost (9
10). If it is not the last channel, the channel with the next highest priority is selected, and this is set as channel n (911),
The process returns to the control for checking the availability again (901). In the present embodiment, both the priority increase (904) and the priority decrease (908) are performed in the base station that does not give adjacent channel interference, but only one of them may be performed.

FIG. 10 is a flow chart for explaining a method for the switching station to update the interference matrix indicating the interference state between the base stations from the reception level report of each mobile station in the channel allocation method of the sixth invention. is there. Each cell is divided into two in a donut shape, and the inner cell and the outer cell perform channel assignment independently of each other.

When the exchange receives the reception level report in the format of FIG. 3 via the connected base station BS _i (1
000), the variable n is set to 1 (1001), and the reception level LEV DL of the connected base station BS _i is compared with the threshold 3 (1002). The threshold value 3 is selected to be the average reception level at the boundary between the inner cell and the outer cell. Therefore, if the reception level LEW DL is larger than the threshold value 3, it can be determined that the mobile station is located in the inner cell.
On the contrary, if the reception level LEV DL is smaller than the threshold value 3, it can be determined that the mobile station is located in the outer cell. When it is determined that the mobile station is located in the inner cell, 1 in FIG.
The interference matrix corresponding to the inner cell is updated by the same procedure as 02-111 (1003). When the update of the interference matrix for the connected base station BS _i and the first neighboring base station BS _j is completed, 1 is added to the variable n (1004), and if the variable n is 6 or less, the procedures of 1003 and 1004 are repeated, When n exceeds 6, the process ends and the next reception level report is prepared (1005). When it is determined that the mobile station is located in the outer cell, 102 in FIG.
The interference matrix corresponding to the outer cell is updated by the same procedure as described in (-111) (1006). When the update of the interference matrix for the connected base station BS _i and the first neighboring base station BS _j is completed, 1 is added to the variable n (1007), and if the variable n is 6 or less, the steps 1006 and 1007 are repeated to When n exceeds 6, the process ends and the next reception level report is prepared (1008). By doing so, even when the cell is divided into the inner side and the outer side, the interference matrix corresponding to each cell can be automatically created.

When a channel is newly allocated by calling, receiving a call, handoff, or the like of the mobile station, whether the mobile station is located in the inner cell or the outer cell based on the reception level of the base station to which the mobile station desires to connect. Select whether to sphere,
A channel in which no interference occurs is assigned based on the interference matrix corresponding to the selected cell and the usage state of the channel at each base station.

[0038]

As described above in detail, according to the present invention, it is possible to provide a dynamic channel allocation system in which the occurrence of interference is small in a cellular mobile communication system.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a method of updating an interference matrix in the channel allocation system of the first invention.

FIG. 2 is a diagram showing a configuration example of a mobile communication system.

FIG. 3 is a diagram showing a format example of a reception level report.

FIG. 4 is a diagram showing an example of a CIR probability density distribution.

FIG. 5 is a diagram showing an example of an interference matrix.

FIG. 6 is a flowchart for explaining a channel allocation system of the second invention.

FIG. 7 is a flowchart for explaining a channel allocation system of the third invention.

FIG. 8 is a flowchart for explaining a channel allocation system of the fourth invention.

FIG. 9 is a flowchart for explaining a channel allocation system of the fifth invention.

FIG. 10 is a flowchart for explaining an interference matrix updating method in the channel allocation system of the sixth invention.

[Explanation of symbols]

102-104 Aggregation of reception level ratio between connected base station and each neighboring base station 105-111 Determination of same or adjacent channel interference 200 Switching station 201 Base station 202 Mobile station 300 Reception level of connected base station 301-306 Peripheral base station identifiers 307 to 312 Peripheral base station reception levels 603, 606 Priority update in base stations that give co-channel interference 703, 706 Priority update in base stations that do not give co-channel interference 803, 807 Update of priority in used base station 804, 808 Update of priority in base station that gives adjacent channel interference 904, 908 Update priority in base station that does not give adjacent channel interference 1002 Depending on reception level of connected base station Of the reception level ratio between the connected base station and each neighboring base station Determination of the split aggregate 1003,1006 same or adjacent channel interference

Claims (6)

(57) [Claims] 1. A channel allocation method for a cellular mobile communication system, wherein a mobile station in a call measures the reception levels of a connected base station and a neighboring base station, the base station being connected from a reception level measurement result of the mobile station. And a reception level ratio between each of the peripheral base stations, and whether the peripheral base stations cause co-channel interference or adjacent channel interference to the connected base station from the distribution of the reception level ratio And a channel allocation method for determining a channel to be used by each base station based on the result of the determination. 2. A priority is given to a channel used by each base station, and a channel having a higher priority is used, and when a certain channel can be used without interference and interference, the base station using the channel is used. When the priority of the channel in the base station determined to give the co-channel interference is lowered, and when a certain channel cannot be used due to the interference, the co-channel interference is given to the base station using the channel. The channel allocation method according to claim 1, wherein the priority of the channel in the determined base station is increased. 3. A channel used by each base station is given a priority, and a channel having a higher priority is used, and when a certain channel can be used without interference, the same channel is used for the base station using the channel. Among the base stations determined not to give interference, the priority of the channel is increased in one or more base stations selected in the order of proximity to the base station using the channel, and a certain channel can be used due to interference. If not, in one or more base stations selected in the order of proximity to the base station using the channel from among the base stations determined not to give co-channel interference to the base station using the channel The channel allocation method according to claim 1, wherein priority of the channel is lowered. 4. A channel to be used by each base station is given priority, and a channel having a higher priority is used. When a certain channel can be used without interference, the channel in the base station using the channel is used. Lowering the priority of the adjacent channel, lowering the priority of the adjacent channel of the channel in the base station determined to give the adjacent channel interference to the base station using the channel, and a certain channel cannot be used due to the interference. In the case of, the channel adjacent to the channel in the base station using the channel is raised in priority, and the adjacent channel of the channel in the base station determined to cause adjacent channel interference to the base station using the channel 2. The channel allocation method according to claim 1, wherein the priority of is increased. 5. A channel to be used by each base station is given a priority, and a channel having a higher priority is used, and when a certain channel can be used without interference, an adjacent channel to the base station using the channel is used. Among the base stations determined not to give interference, the priority of the adjacent channel of the channel is increased in one or more base stations selected in ascending order of the base station using the channel, and a certain channel interferes with the interference. If it cannot be used due to, the one or more selected from the base station using the channel in the order close to the base station using the channel from among the base stations determined not to give adjacent channel interference to the base station using the channel. The channel allocation method according to claim 1, wherein the priority of the adjacent channel of the channel in the base station is lowered. 6. A reception level ratio between a connected base station and each peripheral base station is divided into two or more in accordance with a reception level of a connected base station in a mobile station, and the total is calculated. Determine from the distribution whether or not each peripheral base station gives co-channel interference or adjacent channel interference to the connecting base station for each peripheral base station, and determines the channel to be used based on the result of the determination. The channel allocation method according to claim 1, wherein the channel allocation method is determined.