JP2003111132A - Autonomous distributed control channel allocation method and autonomous distributed control channel allocation device in hierarchical cell mobile communication system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the frequency use efficiency of the entire system when combining a hierarchical cell configuration and a segregated channel allocation scheme. FIG. 1 shows a flow of a channel assignment process in a system in which a segregation channel assignment is applied to base stations of both layers in a hierarchical cell configuration. In the present invention, a channel (priority channel for each layer) assigned preferentially for each layer is designated. Then, after the priority update process (S5, S7) after the channel availability / busy detection (S4),
Further, additional priority update processing (S10, S11) is performed, and while maintaining the priority relationship within the priority channel for each layer,
By providing a priority difference between the priority channel of the layer to which the own station belongs and the priority channel of the layer to which the own station does not belong, the separation of the channels assigned to each layer is promoted, and the channel segregation within the layer is also secured. Thus, the frequency use efficiency of the entire system is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autonomous distributed control channel allocation method and channel allocation apparatus in each hierarchical base station in a cellular mobile communication system having a hierarchical cell structure.

[0002]

2. Description of the Related Art A mobile communication system accommodates a large number of mobile stations moving in a wide area, and therefore a cellular system covering a service area by a plurality of cells (radio zones) formed by a plurality of base stations. Is generally used. FIG. 5 is a diagram illustrating a general cellular mobile communication system in which a service area for communicating with a mobile station is formed by a plurality of wireless zones formed by a plurality of base stations. In this figure,
Each mobile station is wirelessly connected 6 to the nearest base station 4, and each base station 4 is connected to the switching center 2 by the terrestrial cable system 3 and further connected to the other network 1. Here, when the mobile station 5 makes a call and requests a wireless connection to the base station 4, the base station 4 searches for and allocates an empty channel which is not currently used and which satisfies a predetermined condition, from its own channel.

By the way, in order to accommodate a larger number of mobile stations in a limited frequency band, it is general to use a so-called "small cell" technique for narrowing the cell size in such a cellular system. Target. If the cell size is reduced by reducing the transmission power of the mobile station and base station,
Interference when using the same channel in the area is reduced, the same channel can be reused more frequently at shorter distance intervals, and the number of mobile stations accommodated per frequency band can be increased. However, on the other hand, there is a problem that the control amount load of the base station is increased, such as handover control for switching the wireless channel to the corresponding cell as the mobile station moves.

Therefore, for example, a mobile station having a slow moving speed such as a pedestrian is selectively accommodated in a small cell, and a mobile station moving at high speed such as an automobile is selectively accommodated in a large cell, and the frequency and space between the cells are selectively accommodated. Hierarchical cells sharing each other are under consideration. FIG. 6 shows a two-layer cell structure of a large cell layer and a small cell layer, in which a mobile station having a slow moving speed is selectively accommodated in a small cell, and a mobile station moving at high speed is selectively accommodated in a large cell. FIG. 6 is a diagram showing an example of a hierarchical cell configuration in which frequencies and spaces are shared between cells (in this case, a two-layer cell configuration of a large cell layer and a small cell layer). In this figure, the mobile station knows its own moving speed by a speed detecting device or the like, and at the time of making a call, it selects a base station of a layer for which channel allocation is requested based on its own moving speed information and makes a call. Base stations in both layers share the same frequency band channel, and according to the layer selection and channel allocation request from the mobile station, the base station in the layer is a channel that is not currently used from its own channel Search and allocate free channels that meet the conditions. As a channel allocation method, there is a dynamic channel allocation method by autonomous distributed control. In this method, each base station independently searches for free channels and allocates channels from common channel resources in the system, so the base station control load is light, and new base stations can be added without major changes to existing base station systems. There is an advantage.

Channel Segregatio
The n) method is an adaptive method using autonomous distributed control that automatically avoids interference while learning cell allocation and uses different channels for each base station without measuring and investigating the received power distribution at the base station in advance. Channel allocation method (Reference: Y.Furuya, Y.Akaiwa "Channel Segregation, a Dist
ributed Adaptive Channel Allocation Scheme for Mob
ile Communication Systems "1991/6 IEICE Trans. Vo
l.E74, No.6). In this channel segregation method, a carrier sense function is introduced in each base station so that the channel used can be determined by the autonomous distributed control method. Each base station learns the cell arrangement and the interference map between the base stations based on the statistical data of the carrier sense results. Each base station gives a high priority to a specific channel according to the learning result, and tries to use them with high probability. As a result of the learning, the base stations within the distance of mutual interference use different channels. The detailed algorithm will be described with reference to the flowchart in FIG. 7. (1) A priority function P (i) is defined for each channel #i. The channel priority is determined by the value of the priority function P (i). That is, the channel with the highest priority function P (i) has the highest priority. (2) When the base station issues a call connection request, the base station rearranges the channels it holds in order of priority P (i) (S1), and then searches for an empty channel in this order. (3) If the first highest priority channel (not the last channel) is unused (S3 is yes), this is designated as the observation channel. (4) The base station carrier senses the channel.
In other words, the desired wave received power from the terminal that requested connection,
The received power of the interference wave on the observation channel is measured, and CIR (Ca
rrier to Interference Ratio: Ratio of desired wave to co-channel interference wave) is calculated and compared with a predetermined threshold Th. CI
If R is less than the predetermined threshold Th, then the channel is considered busy. Otherwise, it is considered empty. (5) If it is detected that the channel is empty (S4 returns yes
s), the base station increases the priority function of its channel (S
5) Then, communication is started on that channel (S6). (6) If the channel is detected as busy (S4 is n
o), the base station decrements the priority function of that busy channel (S7) and performs another free channel search for the next highest priority channel (S8). Then, the base station repeats the processing from step (3). (7) If all channels are detected as busy,
The call becomes a call loss (channel cannot be assigned and communication cannot be performed) (S9).

According to the above-mentioned algorithm, once the channel #i is successfully allocated in the base station a, the priority of the channel #i in the base station a increases. In this way, the priority of channel #i becomes high, so that the base station a uses channel #i. The surrounding base stations recognize that channel #i is likely to be busy, and
Decrease the priority function of i. Thus, channel #i
Is "acquired" by base station a.

The iterative calculation method of the priority function P (i) executed in steps S5 and S7 is as follows. (1) For each channel #i, the base station stores a set of information P (i) and N (i). Where P (i) is the priority function,
N (i) is the number of times of access (observation designation) to channel #i,
Show. (2) If channel #i is detected as being empty and allocation is successful,
P (i) and N (i) are updated as follows. P (i) == [P (i) N (i) +1] / [N (i) +1] N (i) == N (i) +1 where == is the value on the right side of the left side Indicates to replace. (3) If channel #i is not successfully allocated, P (i) and N (i)
Is updated as follows. P (i) == [P (i) N (i)] / [N (i) +1] N (i) == N (i) +1

FIG. 8 is a diagram showing how effective channel utilization progresses with time as a result of learning. here,
It is assumed that four cell base stations (A # 1, A # 2, A # 3, A # 4) share six channels. It can be seen from FIG. 8 that each base station uses different channels as time passes (t1 → t2 → t3). At time t1, the frequency of use of channels 2, 1, 1 and 2 is high in the order of cell numbers, and channel segregation has not occurred. This gradually segregates channels as time passes t2 and t3 (3 in the order of cell numbers).
2, 1, 3 channels). That is, the base station
A # 1 captures the third channel, base station A # 2 captures the second channel, base station A # 3 captures the first channel, and base station A # 4 captures the third channel. Since both base stations A # 1 and A # 4 are separated from each other and have no interference, the same channel (third channel) is captured. In this way, frequency reuse that automatically avoids interference occurs between base stations.

[0009]

In order to improve the frequency utilization efficiency of a mobile communication system in which different call types coexist, a system combining the above hierarchical cell configuration and segregation channel allocation method is required. However, the method of simply combining the above-described conventional hierarchical cell configuration and the segregation channel allocation method has the following problems. That is, since cells of a certain layer and cells of another layer (generally different in size) are overlapped in the same area, mutual interference conditions when the same channel is used in cells of both layers are:
The size and positional relationship between the cells of both layers, the positional relationship between the terminal and the base station, and the like change variously, and become very complicated.

In the conventional non-hierarchical (single-layer) cell structure, the CI
Each base station equivalently learns the cell arrangement and the interference map between the base stations based on the statistical value of the R (Carrier to Interference Ratio) determination, and the base stations in the mutual interference relationship As a result of learning, different channels are used, but in the simple combination method of the hierarchical cell method and the channel segregation method, due to the complexity of this interference relationship, base stations between layers and within layers can automatically interfere with each other. The mechanism of channel segregation that avoids the problem and uses a specific channel becomes difficult to work.

Therefore, the segregation channel allocation method is not applied to both layers, but one layer is fixed channel allocation (the channel to be used is determined in advance for each base station).
As a method, it has been proposed to apply the segregation channel allocation method only to the other layer (Furukawa, Akaiwa, "Macro / micro cell coexisting cellular system applying channel segregation method", IEICE Tech. Report RCS93-81 ). However, the fixed channel allocation method has low frequency utilization efficiency, and even if the channel allocation method is applied to only one layer, the merit of making the entire system into hierarchical cells is halved.

As described above, in the conventional simple combination method of the hierarchical cell configuration and the segregation channel allocation method, the channel segregation mechanism between layers and within layers becomes difficult to work, and the frequency utilization efficiency of the entire system is improved. There is a problem of reducing it.

Therefore, an object of the present invention is to solve the above problems and to improve the frequency utilization efficiency of the entire system, and an autonomous distributed control channel allocation method and autonomous distributed control in a hierarchical cell mobile communication system. It is to provide a control channel allocation device.

[0014]

In order to achieve the above object, the method of allocating an autonomous distributed control channel in a hierarchical cell mobile communication system according to the present invention is a hierarchy in which cells of different natures are arranged in the same service area. A channel allocation method in a mobile communication system having a cell configuration, in which base stations of both layers perform channel allocation by a channel segregation method, which is a channel that is preferentially allocated for each layer (hereinafter, "priority channel for each layer"). ) Is specified, each base station provides a difference in priority value between priority channels for each layer while maintaining the priority relationship in each priority channel for each layer, and based on the priority of each channel. Channel allocation is performed.

Further, in order to provide a difference in the priority value between the priority channels for each layer while maintaining the priority relationship within the priority channel for each layer, each base station gives priority to each channel by the channel segregation method. Regarding the degree, the layer to which the own station belongs is the high-priority layer, and the layer to which the own station does not belong is the low-priority layer.
/ (Maximum priority of priority channel of low priority layer) (γ is a real number less than 1), (priority channel of priority channel of low priority layer (new)) = α x (of priority channel of low priority layer) Each priority
(Old)), each priority of the priority channel of the low priority layer is further updated.

Alternatively, each base station prioritizes each channel according to the channel segregation method in order to provide a difference in priority value between the priority channels for each layer while maintaining the priority relationship in the priority channel for each layer. Regarding the degree, β = (minimum priority of priority channel of high priority layer), with the layer to which the own station belongs as the high priority layer and the layer to which the own station does not belong as the low priority layer
− (Maximum priority of priority channel of low priority layer)
When <0, (priority channel of low priority layer (new)) = (priority channel of low priority layer (old))
+ Β-γ (γ is a real number less than 1), and in the case of β ≧ 0,
(Each priority of the priority channel of the low priority layer (new)) = (Each priority of the priority channel of the low priority layer (old))-γ is used to further update each priority of the priority channel of the low priority layer. Is.

Further, the autonomous distributed control channel allocation device in the hierarchical cell mobile communication system of the present invention has a hierarchical cell structure in which cells having different properties are superposed in the same service area, and the base stations of both layers are channels. A channel assignment device in a mobile communication system that assigns channels by a segregation method, and a priority channel designation unit for each layer that designates a channel to be assigned with priority for each layer (hereinafter, referred to as "priority channel for each layer"). And an inter-tier priority difference setting unit for providing a difference in priority value between the priority channels for each layer while maintaining the priority relationship in each priority channel for each layer.

Further, the inter-layer priority difference setting unit sets α = γ × (the priority channel of the high-priority layer as a high-priority layer to which the local station belongs and a low-priority layer to which the local station does not belong. (Minimum priority) / (Maximum priority of priority channel of low priority layer) (γ: Real number less than 1), (Priority of each channel of low priority layer (new)) = α x (Low priority layer) According to the respective priorities (old) of the priority channels of (1), the processing of further updating the respective priorities of the priority channels of the low priority layer is executed.

Further, the inter-layer priority difference setting unit sets β = (minimum priority of priority channel of high priority layer as a high priority layer to a layer to which the local station belongs and a low priority layer to a layer to which the local station does not belong. Degree)-(maximum priority of the priority channel of the low priority layer), and if β <0, (each priority of the priority channel of the low priority layer (new)) = (of the priority channel of the low priority layer) Each priority (old) + β-γ (γ is a real number less than 1), β ≧ 0
In the case of, each priority of the priority channel of the low priority hierarchy is
(New)) = (Priority of each priority channel in the lower priority layer (Old))-
According to γ, the processing of further updating each priority of the priority channel of the low priority layer is executed.

According to the present invention as described above, the prioritized updating of priority for each channel, that is, when the observed channel is detected to be empty, the priority function of the channel is increased, and when it is detected to be busy, the busy function is increased. -In addition to the process of decreasing the priority function of the channel, the process of designating the channel to be preferentially assigned for each layer and the difference in the priority value between layers while maintaining the priority relationship of the priority channel for each layer. Update is provided. Due to this difference in priority value between layers, a specific priority channel for each layer is assigned to a specific layer, and separation of channels assigned to each layer is promoted. Further, by maintaining the priority relationship of the priority channels for each layer, the conventional channel segregation in the layer is secured, and frequency reuse for automatically avoiding interference between base stations occurs. In this way, an improvement in frequency utilization efficiency of the entire hierarchical cell system is achieved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a flowchart of a segregation method channel allocation process executed in a base station that implements an autonomous distributed control channel allocation method in a hierarchical cell mobile communication system of the present invention.
Comparing FIG. 1 with the conventional non-hierarchical (one-layer) cell configuration segregation method channel allocation processing flow of FIG.
In the case of the present invention, the same additional priority update is performed after each of the priority function update (up) process (S5) when a free channel is detected and the priority function update (down) process when busy is detected (S7). The difference is that processing (steps S10 and S11) is added. Since the other steps are the same as those in the flow of FIG. 7, the description thereof will be omitted.

The additional priority update processing in steps S10 and S11 will be described below. FIG. 2 is a chart showing an example of additional priority update processing contents in all base stations belonging to a specific hierarchy A. Here, the hierarchical cell system is composed of two layers, layer A and layer B, and the number of system channels is 6 channels # 1 to # 6. Further, in the present invention, a channel to be preferentially assigned for each layer (referred to as “priority channel for each layer”) is defined. Here, channels # 1 to # 3 for layer A and channels for layer B are assigned. It is assumed that # 4 to # 6 are specified. Similar to the conventional channel segregation method for non-hierarchical (single-layer) cell configuration, the priority function P (i) value updated in step S5 or S7 after detection of a free / busy channel is P (1) = 0.4, P (2) = 0.5, P (3) = 0, respectively.
9, P (4) = 0.6, P (5) = 0.2, P (6) = 0.3.

Here, in the base station belonging to this layer A,
In the additional priority update processing of step S10 or S11, the following processing is performed. First, minPa (i) = min [P
(1), P (2), P (3)], the minimum priority in the priority channel for layer A is obtained. Also, maxPb (i) = max [P (4), P (5),
P (6)] determines the maximum priority in the priority channel for layer B. Let γ = 0.9 be any real number γ less than 1. Next, α = γ × (minimum priority of high priority hierarchy) / (maximum priority of low priority hierarchy) = γ × (minimum priority of hierarchy A) / (maximum priority of hierarchy B) = 0.9 × 0.4 Calculate /0.6 = 0.6. In this description, since the base station for layer A is the additional update process, (minimum priority of high priority layer) is (minimum priority of layer A priority channel) and (maximum priority of low priority layer). ) Corresponds to (maximum priority in the priority channel for layer B).

Then, only for each priority of the low priority hierarchy B, additional priority is updated by (each priority of the low priority hierarchy (new)) = α × (each priority of the low priority hierarchy (old)) . That is, Puα (1) = P (1) = 0.4 (invariant) Puα (2) = P (2) = 0.5 (invariant) Puα (3) = P (3) = 0.9 (invariant) Puα (4) = α × P (4) = 0.6 × 0.6 = 0.36 Puα (5) = α × P (5) = 0.6 × 0.2 = 0.12 Puα (6) = α × P (6) = 0.6 × 0.3 = 0.18 and added these The new priority is updated. In the next channel allocation process in the base station of the layer A, the owned channels are rearranged in the order of the additionally updated priority function Puα (i) value, and the empty channel search is performed in that order.

In this way, the channels to be preferentially assigned to the layer A are designated as # 1 to # 3, and the Pu α (1 to 3) are assigned to the channel # 4 to be preferentially assigned to another layer (layer B).
It is always larger than Puα (4 ~ 6) of ~ # 6. That is, there can be a difference in priority value between layers. Moreover, each Pu α
(4), Puα (5), Puα (6) and each P (4), P (5), P (6) are maintained in the priority relationship (size relationship), and the priority update processing of this priority is maintained. Before and after, the magnitude relation of the priorities in the priority channels for each layer is maintained. Due to the difference in priority value between layers, a specific priority channel for each layer is assigned to a specific layer, and separation of channels assigned to each layer is promoted. In addition, by maintaining the priority relationship within the priority channel for each layer, the conventional channel segregation within the layer is secured, and frequency reuse that automatically avoids interference between base stations occurs.

Here, the real number γ (0 <γ <1) is a parameter that gives a ratio of the minimum priority of the high-priority hierarchy and the maximum priority of the low-priority hierarchy after the update of the additional priority, that is, the priority between the hierarchies. It is a parameter that determines the degree of difference in degree, and the smaller γ has the function of accelerating the separation of channels assigned to each layer. Also, since γ is multiplied by each priority of the low priority hierarchy, it also affects the priority difference in the low priority hierarchy,
The smaller γ is, the smaller the priority difference becomes, and it takes time to converge the channel segregation in the low-priority hierarchy. This arbitrary real number parameter γ can be controlled so that it becomes the optimal separation time for each hierarchy and convergence time for resident separation in each hierarchy depending on the call load situation of the actual hierarchical cell system.

Channels # 1 to # 3 for layer A and channels # 4 to # 6 for layer B are designated as channels to be preferentially assigned for each layer. If the volume increases, the channel assigned to it is # 1
~ Not limited to # 3. The priority channel for layer A is a channel that is assigned preferentially to layer A, and if more calls are already made while using channels # 1 to # 3, the priority is next set to Pu α (4 to 6). High channel #
4, # 6, # 5 are designated as observation channels and empty search is performed. Further, the above is the additional priority updating process in all the base stations belonging to the layer A, but the opposite additional priority updating process is performed in all the base stations belonging to the layer B. That is,
In this case, (Minimum priority of high priority layer) is (Minimum priority of layer B priority channel), (Maximum priority of low priority layer) is (Maximum priority of layer A priority channel) , M
inPb (i): Tier B minimum priority and maxPa (i): Tier A maximum priority, α = γ × minPb (i) / maxPa (i) is obtained, and Puα (1 to 3) = α × P (1 to 3), Pu α (4 to 6) = P (4 to
6) Immutable additional priority update processing.

FIG. 3 is a principal block diagram showing an example of the configuration of a hierarchical cell mobile communication system base station apparatus including the autonomous distributed control channel allocation apparatus of the present invention that implements the above-described autonomous distributed control channel allocation method. . In this figure, 1
Reference numeral 1 is an antenna, and 12 is a transceiver having a receiver 13, a transmitter 14, and a channel setting unit 15. Reference numeral 16 denotes an autonomous distributed control channel allocation device of the present invention, which is a CIR determination unit 1
8, a channel priority order rearrangement unit 19, a free channel search unit 17 including a channel unused determination unit 20,
A table unit 21, a conventional channel segregation priority updating unit 22, and an additional priority updating unit 23 of the present invention including a hierarchical channel specifying unit 24 and an inter-tier priority difference setting unit 25 are included. There is. The channel table section 2
1 is used (or unused) for each channel
Is a table for storing a set of information indicating the information, the priority information of the channel, and the number of times of access (observation designation) to the channel.

When there is a call connection request in the base station configured as described above, the channel table section 21 is referred to, the channels are sorted in the priority order by the channel priority order sorting section 19, and the channels are sorted in the priority order. Unused determination unit 2
It is determined whether or not the channel is unused by 0, and the observation channel is designated to the channel setting unit 15 of the transceiver 12. The channel setting unit 15 controls the frequency synthesizer or the like of the receiver 13 to take out the reception signal of the observation designated channel. The received signal is carrier sensed by the CIR determining unit 18, and the prioritization of the channel is raised / lowered by the conventional segregation method priority updating unit 22 by the vacancy / busy determination. This priority (old) is further updated by the additional priority updating unit 23 of the present invention, and new priority information is stored in the channel table unit 21. The layer-by-layer priority channel designating unit 24 designates a channel to be preferentially allocated for each layer, and the inter-layer priority difference setting unit 25 maintains the priority relationship of the layer-by-layer priority channel while maintaining a difference in priority value between layers. To provide. The usage information in the channel table section 21 is the CIR determination section 18
And the access count information is updated by the observation designation signal from the channel unused determination section 20.

In the above-described embodiment, in order to provide a difference in priority value between layers, the ratio of the minimum priority of channels belonging to the high priority layer to the maximum priority of channels belonging to the low priority layer is 1 Using the value α multiplied by a coefficient less than
Although the priorities of the channels belonging to the low priority layer are additionally updated, other methods can be used. Hereinafter, another embodiment of the additional priority update processing will be described. Note that, also here, the chart of FIG. 2 is referred to. In this method, the minimum priority mi
The process is performed in the same manner as in the above case until the derivation of nPa (i) and the maximum priority maxPb (i) of the low priority layer. Then, β = (minimum priority of high priority hierarchy) − (maximum priority of low priority hierarchy) = (minimum priority of hierarchy A) − (maximum priority of hierarchy B) = 0.4−0.6 = −0.2 , Β <0 only for each priority of the low priority hierarchy B
In the case of, each priority of the low priority hierarchy (new) = (each priority of the low priority hierarchy
(Old)) + Adds priority update to β-γ. Here, γ is an arbitrary real number less than 1. That is, Puβ (1) = P (1) = 0.4 (invariant) Puβ (2) = P (2) = 0.5 (invariant) Puβ (3) = P (3) = 0.9 (invariant) Puβ (4) = P (4) -0.2-0.9 = 0.6-1.1 = -0.5 Puβ (5) = P (5) -0.2-0.9 = 0.2-1.1 = -0.9 Puβ (6) = P (6) -0.2-0.9 = 0.3- 1.1 = -0.8, and these are new priorities that have been added and updated. Further, when β ≧ 0, (each priority of the low priority layer (new)) = (each priority of the low priority layer)
(Old) -Additional priority update process is set to -γ. That is, the additional priority update is performed such that Puβ (4) = P (4) −0.9 Puβ (5) = P (5) −0.9 Puβ (6) = P (6) −0.9. In the next channel allocation processing, empty channels are searched in the order of the additionally updated priority function Puβ (i) value.

As described above, Puβ (1 to 3) of channels # 1 to # 3 preferentially assigned to the layer A are Puβ of channels # 4 to # 6 preferentially assigned to another layer (tier B).
It is always larger than (4 ~ 6). That is, there can be a difference in priority value between layers. Moreover, each Puβ (4), Puβ (5),
The priority relationship (size relationship) between Puβ (6) and each P (4), P (5), P (6) is maintained. Therefore, as in the previous case,
Due to the difference in priority value between layers, a specific channel for each specific layer is assigned to a specific layer,
Separation of channels assigned by hierarchy is facilitated.
In addition, by maintaining the priority relationship within the priority channel for each layer, the conventional channel segregation within the layer is secured, and frequency reuse that automatically avoids interference between base stations occurs. Here, the real number γ (0 <γ <1) determines the difference between the minimum priority of the high-priority tier and the maximum priority of the low-priority tier after the additional priority is updated, that is, the degree of the difference in priority between tiers. It is a parameter, and has a function of accelerating the separation of channels assigned by hierarchy as γ increases. This arbitrary real number parameter γ can be controlled so that the optimum separation time for each layer is obtained according to the call load situation of the actual hierarchical cell system. The reverse addition priority update process is performed for all base stations belonging to the layer B, as in the case described above.

As described above, according to the present invention, the additional update priority Puα (i) (or Puβ (i)) of a channel that is preferentially assigned to a specific layer is preferentially assigned to another layer. The priority of the channel to be allocated is always higher than Puα (i) (or Puβ (i)), and there is a difference in the priority value between layers. Moreover, the priority relationship (size relationship) of each priority Puα (i) (or Puβ (i)) of the priority channel for each layer
Is maintained. Due to the difference in priority value between layers, a specific priority channel for each layer is assigned to a specific layer, so that the same channel assignment does not conflict in both layers, and the channels assigned by layer are separated. Is promoted. In addition, by maintaining the priority relationship of priority channels for each layer, the conventional channel segregation in which a specific channel is assigned to a specific base station in the layer is secured, and interference between base stations is automatically prevented. The avoidance of frequency reuse occurs. Further, since the channel search is performed in the order of the additional update priority regardless of the priority channel for each layer, the empty channel is always searched for the entire number of system channels in any layer. Therefore, even if there is a fluctuation in call volume between tiers, the number of channels according to the intra-tier call volume is allocated from all system channels in each tier without being limited to the number of priority channels for each tier. Can follow.

FIG. 4 is a diagram showing the time transition of the channel allocation frequency of each layer in the hierarchical cell / segregation system channel allocation of the present invention. Here, the hierarchical cell system is composed of two layers of A layer and B layer, the number of system channels is 6 channels # 1 to # 6, and channels # 1 to # 3 and B for A layer are given as priority channels for each layer. It is assumed that channels # 4 to # 6 are specified for the hierarchy. At time t1, each channel of # 2, # 1, # 1, and # 2 in the order of cell numbers in the A layer, and in the B layer
The allocation frequency of each channel # 3, # 4, # 6, # 3 is high. The high allocation frequency channels of the A layer are # 1 and # 2, and the A layer priority channel # 1
Corresponding to ~ # 3, the high allocation frequency channel of B layer is
Channels other than B-layer priority channels # 4 to # 6 in # 3, # 4, and # 6
# 3 is also assigned, and the priority channel assignment frequency for each layer has not yet been separated between layers. The high allocation frequency channels for each cell in the B layer are segregated at # 3, # 4, # 6, # 3, but the high allocation frequency channels for each cell in the A layer are # 2, # 1, The same channel # 1 is allocated in # 1 and # 2 and adjacent cells, and the channels in the hierarchy are not sufficiently segregated. Due to the additional priority update of the present invention, the priority channel frequency for each layer is gradually separated as time elapses t2 and t3 (channels # 1 to # 3 in the A layer, channels # 4 to # in the B layer). 6) and channel segregation within the layer (channels # 3, # 2, # 1, # 3 in the A layer in order of cell numbers, channels in the B layer)
# 4, # 5, # 6, # 4) will occur. Therefore, the adverse effect of the complicated interference relationship between the two layers in the method of simply combining the allocation method by the hierarchical cell and the channel segregation, that is,
To improve the problem that the channel segregation mechanism that automatically avoids interference between layers and base stations in the layer and uses a specific channel becomes difficult to work, and reduces the frequency utilization efficiency of the entire system. You can

By applying the present invention to another dynamic channel allocation method by autonomous distributed control based on the same principle as the channel segregation method, the application of the present invention promotes the separation of channels allocated to each hierarchy in a hierarchical cell. At the same time, it is possible to improve the frequency utilization efficiency of the entire system by ensuring channel reuse within the hierarchy.

[0035]

As described above, according to the autonomous distributed control channel allocating method and allocating apparatus of the present invention, it is possible to configure a hierarchical cell in which the channel segregation method is applied to base stations of both layers.
In the system, separation of channels assigned to each layer is promoted, and channel segregation in each layer is also secured. Therefore, frequency utilization efficiency of the entire system can be improved. As a result, in a hierarchical cell system that accommodates different call types such as low-speed mobile stations and high-speed mobile stations, the channel segregation method is applied to both layers, improving the frequency utilization efficiency of the entire system, It becomes possible to accommodate many users.

[Brief description of drawings]

FIG. 1 is an example flowchart of a segregation method channel allocation process for a hierarchical cell mobile communication system embodying the present invention.

FIG. 2 is a diagram showing the contents of an additional priority update process in all base stations belonging to a specific layer A implementing the present invention.

FIG. 3 is a configuration example of a hierarchical cell mobile communication system base station apparatus including an autonomous distributed control channel allocation apparatus according to the present invention.

FIG. 4 is a diagram showing a time transition of each channel allocation frequency of each layer in hierarchical cell / segregation method channel allocation in which the present invention is implemented.

FIG. 5 is a diagram illustrating a general cellular mobile communication system in which a service area for communicating with a mobile station is formed by a plurality of radio zones formed by a plurality of base stations.

FIG. 6 shows a hierarchical cell configuration in which a mobile station having a slow moving speed is selectively accommodated in a small cell and a mobile station moving at a high speed is selectively accommodated in a large cell, and frequency and space are shared between the respective cells. It is a figure which shows an example.

FIG. 7 is a flowchart showing a channel allocation processing procedure of a conventional channel segregation method in which a priority function of the channel is increased / decreased by a channel empty / busy detection by CIR determination and a free channel search is performed in order of the priority. Is.

FIG. 8 is a diagram showing a time transition of each channel allocation frequency in the conventional segregation method channel allocation applied to a non-hierarchical (one-layer) cell configuration.

[Explanation of symbols]

11 antenna 12 transceiver 13 receiver 14 transmitter 15 channel setting section 16 Autonomous distributed control channel allocation device 17 Free channel search section 18 CIR judgment section 19 Channel priority sorting section 20-channel unused judgment section 21 channel table section 22 Conventional channel segregation method priority update unit 23 Additional Priority Update Unit of the Present Invention 24 priority channel designation section for each layer 25 Priority difference setting unit between layers

Claims (6)

[Claims] 1. A channel allocation method in a mobile communication system, which has a hierarchical cell structure in which cells of different natures are arranged in an overlapping manner in the same service area, and base stations of both layers perform channel allocation by a channel segregation method. Channel that is preferentially assigned to each layer (hereinafter,
It is called "prior channel for each layer". ), Each base station maintains a priority relationship in the priority channel for each layer while providing a difference in priority value between priority channels for each layer, and allocates channels based on the priority of each channel. An autonomous distributed control channel allocation method in a hierarchical cell mobile communication system. 2. The base stations prioritize each channel according to a channel segregation method in order to provide a difference in priority value between the priority channels for each layer while maintaining the priority relationship within the priority channel for each layer. Regarding the degree, the layer to which the own station belongs is the high-priority layer, and the layer to which the own station does not belong is the low-priority layer.
(Maximum priority of priority channel of low priority layer) (γ is a real number less than 1), (Priority of each priority channel of low priority layer (new)) = α × (each priority channel of low priority layer) 2. The autonomous distributed control channel allocation method in a hierarchical cell mobile communication system according to claim 1, wherein each priority of the priority channels of the low priority hierarchy is further updated by the priority (old). 3. Each base station prioritizes each channel according to a channel segregation method in order to provide a difference in priority value between priority channels for each layer while maintaining the priority relationship in each priority channel for each layer. Regarding the degree of priority, the hierarchy to which the own station belongs is the high priority hierarchy, and the hierarchy to which the own station does not belong is the low priority hierarchy. Degree), and in the case of β <0, (each priority of priority channel of low priority layer (new)) = (each priority of priority channel of low priority layer)
(Old) + β-γ (γ is a real number less than 1), and in the case of β ≧ 0, (each priority of low priority layer priority channel (new)) = (each priority of low priority layer priority channel) Every time
2. The autonomous distributed control channel allocation method in a hierarchical cell mobile communication system according to claim 1, wherein each priority of the priority channels of the low priority layer is further updated by (old) -γ. 4. A channel allocation device in a mobile communication system, which has a hierarchical cell structure in which cells having different properties are overlapped and arranged in the same service area, and base stations of both layers perform channel allocation by a channel segregation method. While maintaining the priority relationship within the layer-specific priority channel and a layer-specific priority channel designating section for designating a channel to be preferentially allocated for each layer (hereinafter, referred to as “layer-specific priority channel”),
An autonomous distributed control channel allocation device in a hierarchical cell mobile communication system, comprising: an inter-tier priority difference setting unit that sets a difference in priority value between priority channels for each hierarchy. 5. The inter-layer priority difference setting unit sets α = γ × (minimum priority channel of the high priority layer as a high priority layer for a layer to which the local station belongs and a low priority layer for a layer to which the local station does not belong. priority)/
(Maximum priority of priority channel of low priority layer) (γ: real number less than 1), (Priority of each priority channel of low priority layer (new)) = α × (each priority channel of low priority layer) 5. Autonomous distributed control in a hierarchical cell mobile communication system according to claim 4, wherein processing for further updating each priority of the priority channel of the low priority hierarchy is executed according to the priority (old). Channel allocation device. 6. The inter-layer priority difference setting unit sets β = (minimum priority of priority channel of high-priority layer as a high-priority layer to which its own station belongs and a low-priority layer to which its own station does not belong. )-(Maximum priority of priority channel of low priority layer), and if β <0, (each priority of priority channel of low priority layer (new)) = (each priority channel of low priority layer) priority
(Old) + β-γ (γ is a real number less than 1), and in the case of β ≧ 0, (each priority of low priority layer priority channel (new)) = (each priority of low priority layer priority channel) Every time
(Old))-γ is used to execute a process of further updating each priority of the priority channels of the low priority layer.
An autonomous distributed control channel allocation device in the hierarchical cell mobile communication system described.