JPH07222232A - Radio channel assigning method - Google Patents

Abstract

PURPOSE:To prevent a call loss rate or the generation rate of interference jamming from being degraded even when a radio wave propagating device is fluctuated based on the installation of a new base station in an autonomous distributed assigning system. CONSTITUTION:A non-used channel with highest priority P is selected out of non-used channels (S3), it is investigated whether the selected channel can be used or not (whether an interference wave is small or not) (S4), when it can be used, processing to assign Plambda+1 (0< #1<1) to that channel as new priority P (Sb) is executed (S7) but when the selected channel can not be used, the Plambda-1 is defined as new priority P (S4) and the channel in the next higher priority is selected (S10).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless channel allocation method in a mobile communication system, in which wireless channels used by each wireless base station for communication with mobile stations are allocated in a distributed manner.

[0002]

2. Description of the Related Art In mobile communication systems such as mobile phones and car phones, which are now widespread, the radius of a wireless zone serviced by one wireless base station is about several kilometers, and many wireless base stations are within the service area. Cellular systems are well known that provide services by being deployed in the.
Generally, in such a system, the same radio channel is used by different radio base stations geographically distant for the purpose of effectively utilizing a limited radio channel.
So-called radio channels are repeatedly used geographically. When repeatedly using the radio channel geographically, interference from the same radio channel or F
In a DMA (Frequency Division Multiple Access) system, the interference and the like from adjacent channels in an interleaved system in which the power of sidebands of radio channels is allowed to overlap to form radio channels are spatially controlled so as not to exceed the allowable value. It is necessary to repeatedly use the same wireless channel in wireless base stations that are sufficiently far apart.

As a method of repeatedly using a radio channel satisfying such conditions, the radio wave propagation situation in the service area is predicted in advance by actual measurement or theoretical calculation, and the radio channel is fixedly arranged in each radio base station. There is a fixed channel allocation method and a dynamic channel allocation method in which wireless channels that are not fixedly arranged and that can be used by the entire system can be used by any wireless base station. Further, the dynamic channel allocation method includes a centralized control type dynamic channel allocation method in which a control station that controls allocation of wireless channels is installed over a plurality of wireless base stations, and such a wireless base station does not require such a control station. There is an autonomous distributed dynamic channel allocation system that allocates wireless channels in an autonomous distributed manner.

In the fixed channel allocation method, the radio channels available in the radio base station are fixedly determined so that the power ratio of the desired wave and the interference wave is equal to or higher than a certain threshold value. Although the probability of occurrence is low, if all wireless channels allocated to the own base station are being used within the own base station, it is possible for the own base station to use the wireless channels assigned to adjacent base stations and Even if there is a transmitter / receiver that is not in use in the own base station, the wireless channel cannot be allocated in response to a new wireless channel allocation request, and the design is to determine the fixed allocation of wireless channels. It has the drawback of requiring a huge amount of work. Further, there is a drawback that the adaptability to system expansion is low, because a redesign is required even when equipment is added.

On the other hand, in the dynamic channel allocation method, it is possible to allocate radio channels to the traffic fluctuations, spatial deviations, etc., with some flexibility, but in order to minimize the probability of call loss or interference. In general, enormous information and complicated control are required, and in the centralized control type dynamic channel allocation method, signal traffic between each radio base station and the control station increases,
In addition, in the autonomous distributed dynamic channel allocation method,
There is a drawback that the processing up to channel allocation is large and the connection delay is large, and it is very important to realize a wireless channel allocation method with a small control load.

As a wireless channel allocation method for realizing autonomous distributed dynamic channel allocation by a relatively simple control method, the allocation priority of each wireless channel is calculated from the history of availability of past allocation, and the allocation priority is high. Whether or not the wireless channel can be assigned is determined in order from the wireless channel. If it is determined that the wireless channel can be assigned, the wireless channel is assigned. Otherwise, the wireless channel with the next highest priority of assignment is moved to determine whether the wireless channel can be assigned. A radio channel allocation method has been proposed (Japanese Patent Application Nos. 61-244137 and 62-62).
-91033).

[0007]

However, in the conventional method of determining the allocation priority of each wireless channel in the autonomous distributed dynamic channel allocation system, the past allocation availability judgment results are all weighted with the same weight and very Since a lot of past assignment availability judgment results are used, there is a problem that it takes a huge amount of time to follow changes in the radio wave propagation state and traffic distribution after the system reaches a steady state. Such changes in the radio wave propagation state and traffic distribution are caused by the construction of new buildings around the radio base station, the construction of the radio base station, the start / stop of the operation of the portable radio base station, etc. The autonomous distributed dynamic channel allocation method using usage history has a drawback in that it cannot follow changes in the radio wave propagation state and traffic distribution, and the call loss rate, the probability of interference, and the connection delay increase.

The present invention is intended to solve these problems and must be taken into consideration in the actual system operation. A new building around the wireless base station, a new wireless base station, or a portable wireless base station is provided. Suitable for system extensibility, without compromising connection quality such as call loss ratio, probability of interference, connection delay, etc. even if changes in radio wave propagation status and traffic distribution etc. occur due to start / stop of station operation etc. An object of the present invention is to provide a wireless channel allocation method with excellent performance.

[0009]

According to the present invention, for each wireless channel, a weighting that changes according to the number of times going back to the past from the current allocation availability judgment is attached to the past allocation availability judgment result of the wireless channel. , The assignment priority of the wireless channel is determined, and it is determined whether or not the wireless channel with the highest assignment priority can be used.

The changing weights are selected to be large for the new allocation availability determination result and small for the old allocation availability determination result. Since the weight of the old assignment availability determination result is smaller, one of the two values having different polarities determined in advance is set as A according to the assignment availability determination result, and P × λ + A (P is the assignment priority of the wireless channel until then). , Λ is a positive weight constant less than 1) and is set as a new allocation priority of the wireless channel.

Further, when a wireless channel is switched due to interference during communication, the allocation priority is updated with respect to the wireless channel before the switching, assuming that the determination result of the availability determination result has occurred. In that case, the calculation of P × λ + A is performed using a value whose absolute value is smaller than the value of A that is used for the non-allocation of the allocation availability determination result when the new wireless channel is allocated.

[0012]

FIG. 1 shows an example of the configuration of a wireless system to which the present invention is applied. A plurality of radio base stations 11 _{1 to} 11 _N serve mobile stations 12 within the entire service area. M wireless channels can be used as the entire mobile communication system, and the wireless base stations 11 _{1 to} 11 _N are transmitters / receivers K ₁ to K capable of transmitting / receiving any one of the M wireless channels. _{It has N} pieces. Each mobile station 12 is equipped with a transceiver capable of transmitting and receiving on any of the M radio channels.

Further, each of the radio base stations 11 _{1 to} 11 _N has a memory for managing the allocation priority of each radio channel, and is 0 or more and less than 1 which is predetermined by the system operator for weight determination. The constant λ of is stored in memory. FIG. 2 functionally shows a part of the equipment in the radio base station 11 _i , which is related to radio channel allocation. The K _i transceivers 13 _{1 to} 13 _Ki are connected to the transceiver control device 14, and the transceiver control device 14 is connected to the wireless channel control device 15. The radio channel controller 15 is connected to the call processing controller 16 and the memory 17. Memory 17
Includes a flag indicating whether each wireless channel Ch _{1 to} Ch _M is in use or unused, and an allocation priority P.
_{1 to} P _M are stored, and a constant λ for determining the weight is also stored.

The radio channel controller 15 reads, updates, and writes the allocation priority of the radio channel in the memory 21 in response to a request from the call processing controller 16, and the radio currently used by the radio base station. Manage channels. The transceiver control device 14 manages the transceivers 13 _{1 to} 13 _Ki and determines whether or not the wireless channel designated by the wireless channel control device 15 can be assigned.

Next, referring to FIG. 3, a wireless channel according to the present invention will be described.
An example of the channel allocation method will be described. (1) New call or wireless from the call processing controller 16
When there is a wireless channel allocation request for channel switching,
The radio channel controller 15 is a radio channel that is not currently in use.
Check whether or not the channel exists in the memory 17
Read the lag and do it. All wireless channels Ch₁~
Ch_MIf the call is being used by the call processing controller 16,
Notify and end the process (S₁). (2) If there are available wireless channels, the wireless channel
The channel control device 15 is different from the transceiver control device 14 in that
Ask if there is a transceiver not currently in use.
Make a meeting. If no transceiver is available
In this case, the transceiver controller 14 is the radio channel controller 1
5, the call processing control device 16 is notified to that effect, and
Ends the process (S₂). (3) If there is a transceiver that can be used, the wireless channel
The controller 15 refers to the allocation priority in the memory 17.
Allocation priority among wireless channels not currently in use
Select a radio channel number with a high
Notify 14 (S ₃), The transceiver control device 14
Whether or not to use the wireless channel is determined as described below, and
The result is returned to the radio channel controller 15 (S_Four). (4) The wireless channel control device 15 determines whether or not it can be used.
If the result is usable, it is decided in advance with respect to the result of the assignment availability judgment.
One of the two values with different polarities, in this example +1
Substitute for A in the assignment priority calculation formula (S_Five), The wireless
Channel allocation priority P_jThe following formula is calculated from_j× λ + A (1) The calculated result is a new allocation priority P_jToshi (S₆), So
Of P_jTo the relevant location on the memory 17
The channel number is notified to the call processing control device 16, and the radio
Channel used / unused flag is being used, that is, "1"
Set as (S₇). (5) Step S_FourUnusable as a result of availability judgment in
If it is
Of the two values with different polarities, in this example, the -1 assigned
Substituting it into A in the previous arithmetic expression (S₈) Of the wireless channel
Allocation priority P_jThe following formula is calculated from_j× λ + A (2) The calculation result is assigned a new allocation priority P_jAs memory 17
Write in the relevant area above (S₉), Then the highest allocation priority
Select the wireless channel that you want to use and select (3), (4), (5)
Repeat the process (S_Ten ). (6) For all wireless channels not currently in use
If the judgment result of availability is not usable, wireless
The channel controller 15 informs the call processing controller 16 to that effect.
Then, the process ends (S₁₁).

[0016] By executing the above processing, the allocation priority P _j of the j-th radio channel Ch _j is the assignment executability judgment for past L times of the radio channel results A _1,
From A ₂ , ..., A _L (A _i (i = 1, 2, ..., L) is +1 or −1 from the above), P _j = A ₁ + λA ₂ + λ ² A ₃ + ... + λ ^{(L- 1) It} is calculated as _AL (3). Since λ is a constant greater than or equal to 0 and less than 1, as a result, the wireless channel allocation priority is most greatly contributed by the previous determination result of whether or not allocation is possible, and thereafter, the contribution to the allocation priority increases as the determination result becomes older. Becomes smaller, and the weighting of the variable allocation determination result becomes smaller as the allocation determination result becomes older, which is realized by an extremely simple operation. At this time, the memory 17 required is sufficient to store the allocation priority, the radio channel usage status, and the constant λ, and the storage capacity is small and high-speed processing is possible.

Various methods are conceivable as the method of determining whether or not the wireless channel can be allocated (step S ₄ ) in the process (3) in the wireless channel allocation method. One of the wireless channels is set and received, and if the reception level, that is, the interference wave level is less than or equal to a predetermined threshold value, it is determined that allocation is possible, A notification for provisional setting is sent and transmitted on that wireless channel, and this is received by the wireless base station.The power ratio between the desired wave and the interference wave on that wireless channel is measured, and if this is above a certain threshold, allocation is possible. There are ways.

Let us consider the convergence of the value of the allocation priority P _j in the case where the availability determination for the j-th radio channel is continuously enabled or disabled. If it can be assigned,
When the assignability determination result A is ρ, and when the assignment is not assignable, the assignability determination result A is set to −ρ, and equations (1) and (2) are calculated to update the assignment priority (however, , Ρ is a positive constant). When only Y is continued L times, P _j is P _j = ρΣ _n-1 ^L λ ^n-1 (4) Σ is from n = 1 to L. When x is -1 <x <1, Σx ⁿ ≈x / (1-x) Σ is from n = 1 to ∞, and the limit of equation (4) is taken as ρΣλ ^n-1 ≈ρ {λ / (1-λ) +1} = ρ / (1-λ) (5) Σ is from n = 1 to ∞. Similarly, even when only the impossibility continues, −ρΣλ ⁿ⁻¹ ≈−ρ {λ / (1-λ) +1} = −ρ / (1-λ) (6), and the value of the allocation priority is It converges to a finite value. That is, even if the allocation priority of the wireless channel in the example is always the highest, the allocation priority does not become infinitely large and becomes larger than the finite value ρ / (1-λ) as described above. Therefore, the value of the allocation priority in the memory 17 does not become so large that it cannot be stored, that is, as the memory 17, the allocation priority ρ /
A storage capacity that can store up to (1-λ) may be prepared.

As described above, according to the present invention, since the weighting of the old assignment availability determination result is reduced, a new building around the wireless base station, a new wireless base station, an operation start / stop of the portable wireless base station are started. Even if the status of the interference wave changes due to changes in the radio wave propagation state due to changes, the construction of a large office building, or changes in the traffic distribution due to dismantling, etc., the allocation priority of each wireless channel can be tracked according to the changes. It changes so as to take a preferable value suitable for the environment, and does not cause deterioration of connection quality.

Further, by selecting the value of the constant λ, it is possible to freely adjust the flexibility of following changes in the radio wave propagation state, traffic distribution and the like. That is, by setting λ to a small value, the influence of the old assignment availability judgment result on the assignment priority is eliminated quickly, and the assignment priority of each wireless channel quickly adapts to changes in the radio wave propagation state and traffic distribution. Grows larger. On the other hand, if λ is set to a large value, the past allocation availability judgment result will affect the allocation priority forever, and the flexibility will be small. Therefore, when the change in the radio wave propagation state or the traffic distribution is relatively small, λ may be relatively large.

In the above description, the allocation priority is calculated based on the result of the allocation availability judgment when a new wireless channel is allocated. However, when interference is caused during communication and the communication is switched to another wireless channel, The fact that there was interference switching is also considered in determining the allocation priority for the radio channel before switching. In other words, the allocation determination result is processed as allocation not possible and the allocation priority is updated. For example, assuming that the allocation availability determination result A is −0.5, P _j × λ + A (7) is calculated from the allocation priorities P _j of the relevant wireless channels until then, and the calculation result is calculated as a new allocation priority P _j. And

It was carried out to confirm the effect of the present invention.
A computer simulation model is shown in FIG. In this simulation, the wireless zones 21 _{1 to} 21 ₅ are hexagonal omnicells, and the wireless zones 21 _{1 to} 21 ₅ are one-dimensionally arranged. The call generation follows the Poisson distribution and occurs spatially uniformly within the wireless zone. The holding time is assumed to follow an exponential distribution with an average of 120 seconds. Also, it is assumed that the habits of calls within each wireless zone are the same. It is assumed that the mobile station which is going to make or receive a call selects the wireless zone in advance by measuring the received power of the perch channel (control channel) transmitted from the wireless base station at a constant transmission power. . In addition, the number of radio channels that can be used in the entire system is set to 20, and only co-channel interference is considered as interference.

In an actual mobile communication system, there is a situation in which a new wireless base station is installed in the area and a service is started due to an increase in requests for calling and receiving calls in an area where the wireless base station does not exist. It happens frequently. In this computer simulation, such a situation was modeled as follows. As shown in FIG. 4A, the wireless base station 11 ₃ does not exist for 5 days after the start of the simulation, and no call is generated in the wireless zone 21 ₃ . As shown in FIG. 4 (b), the wireless base station 11 ₃ is not provided from the 6th day to the 10th day, but a call similar to the other wireless zones occurs in the wireless zone 21 ₃ . Suppose there is. As shown in FIG. 4C, on the 11th day, the wireless base station 1
1 ₃ is newly established and service is started.

5 and 6 show the results of the computer simulation. FIG. 5 shows the call loss rate at the wireless base station 11 ₃ for one day on the 11th day when the wireless base station 11 ₃ was newly established.
FIG. 5 (a) shows the probability of occurrence of uplink and downlink interference, and FIG. 5 (b) and FIG. 6 (a) show the number of times of determination whether or not allocation is necessary for allocating one call. (B)
, And the applied call volume per wireless zone is on the horizontal axis.

From the result of this computer simulation,
According to the wireless channel allocation method of the present invention, compared with the conventional wireless channel allocation method using the wireless channel usage history, the applied call volume per wireless zone is 7 [Erl / Ce].
11], the blocking rate is from 3.13% to 2.02%
, The uplink interference occurrence probability is 2.11% to 1.05%, and the downlink interference occurrence probability is 1.6.
From 0.5% to 0.54%, it was confirmed that the number of times of determination whether or not the allocation required for allocating a wireless channel to one call was significantly improved from 1.93 times to 1.56 times, respectively. The wireless channel allocation method of the present invention can be applied to a change in radio wave propagation state and traffic distribution due to new construction of a wireless base station, a new wireless base station, start / stop of operation of a portable wireless base station, etc. However, it was confirmed that the method is a wireless channel allocation method that suppresses an increase in the call loss rate, the probability of occurrence of interference, and the number of times of judgment of availability for wireless channel allocation, does not deteriorate connection quality, and has a small control load.

In the above-described embodiment, the result of the assignment availability judgment is A = 1 when the assignment is possible, A = −1 when the assignment is not possible, and A = −0.5 when the channel switching is started due to the interference. , A can be set to a positive value when the allocation is possible, and a negative value can be set when the channel is switched due to the non-allocation and interference. In the above-described embodiment, the weight is sequentially decreased with respect to the current allocation availability determination result as the allocation availability determination result becomes older. However, it is not necessary to reduce the weight every time, for example, every two or three times. May be reduced. In order to reduce the weight every two times, the calculation of P _i × λ + A and the calculation of P _i + A may be alternately performed. Further, the weight is not limited to be reduced every fixed number of times, and the number of times of the same weight may be increased as the weight gets older. Further, for example, the weights for the assignment availability determination results from the latest to a predetermined number of times, for example, up to three times may be set to constant values, and the weights assigned to the assignment availability determination results older than that may be set to constant values smaller than the fixed value. In other words, the weight may be reduced at least once as the result of the assignment availability determination becomes older. In addition, depending on the case, the weight with respect to the assignment availability determination result three times before may be set to the maximum with respect to the current one.

Furthermore, in the above description, two numerical values having polarities different from each other, which are selected in accordance with the result of the assignment availability determination, are A = ρ when assignment is possible and A = −ρ when assignment is not possible, that is, absolute values are equal. However, the absolute values may be different from each other. For example, when allocation is possible, A = 1.0, and when allocation is not possible, A = −1.2. When a new wireless base station is provided in the periphery, allocation of wireless channels that have been used with high allocation priority until now. It is possible to lower the priority and make it easier for the new wireless base station to select a wireless channel. Alternatively, if multiple wireless base stations are provided in a wide service area and operations are started simultaneously from a state where the allocation priority of each wireless channel is zero, A = 1.2 when allocation is possible and allocation is not possible. In this case, A = −1.0 is set so that the allocation priority becomes high quickly.

Further, in the above description, when the channel is switched due to the interference interference and the processing is performed assuming that the allocation failure of the allocation availability determination result has occurred, A = -0.5, that is, the allocation becomes unusable in another allocation. In consideration of the fact that the allocation priority was high last time as a value with an absolute value smaller than A = -1.0 when the allocation was made, the numerical value used when allocation is not possible at the time of new allocation without such a case. For example, the same value as A = −1 may be used as A.

As the radio channel, it is considered that the radio frequency is used in the FDMA system, the time slot is used in the TDMA (time division multiple access) system, and the spread code or the frequency hopping pattern is repeatedly used in the CDMA (code division multiple access) system. This invention can be used for radio frequency, time slot, spreading code
Even when the radio channel is configured by either method, the method of the present invention can be applied by determining the radio channel allocation availability by measuring the interference wave level or the power ratio of the desired wave to the interference wave. , The same effect can be obtained.

[0030]

As described above in detail, according to the present invention, the past allocation availability judgment result of the wireless channel is weighted by the number of times going back from the present allocation availability judgment to the past. , The allocation priority is determined, based on the allocation priority, it is determined whether or not the wireless channels with the highest allocation priority can be used in order, and by allocating the wireless channels, the new construction of the building around the wireless base station, the wireless It adapts to changes in radio wave propagation conditions and traffic distribution caused by new base station installations, start / stop of portable radio base stations, etc., and the allocation priority of each radio channel becomes favorable, resulting in call loss rates and interference interference. Occurrence probability,
It is possible to suppress an increase in the number of times of determination of availability required for radio channel allocation, and the connection quality does not deteriorate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a mobile communication system to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration example of equipment within a radio base station applied to the present invention.

FIG. 3 is a flowchart showing a processing procedure in the embodiment of the present invention.

FIG. 4 is a diagram illustrating a simulation model of a computer simulation performed to confirm the effects of the present invention.

FIG. 5 is a graph showing the result of a computer simulation carried out to confirm the effect of the present invention.

FIG. 6 is a graph showing a continuation of the result of the computer simulation.

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[Procedure amendment]

[Submission date] May 13, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

As a wireless channel allocation method for realizing autonomous distributed dynamic channel allocation by a relatively simple control method, the allocation priority of each wireless channel is calculated from the history of availability of past allocation, and the allocation priority is high. Whether or not the wireless channel can be assigned is determined in order from the wireless channel. If it is determined that the wireless channel can be assigned, the wireless channel is assigned. Otherwise, the wireless channel having the next highest priority of assignment is moved to determine whether the wireless channel can be assigned. radio channel assignment techniques have been proposed (JP 61-244137, and JP 62
-91033).

Claims (5)

[Claims] 1. A wireless base station refers to allocation priorities managed on the basis of past usage history for each wireless channel, and determines whether or not the wireless channels can be used in order from the wireless channel with the highest allocation priority. In the method of allocating wireless channels according to the above method, for each wireless channel, a weight that changes according to the number of times past the current allocation availability judgment is applied to the past allocation availability judgment result of that wireless channel is assigned to that wireless channel. A method of allocating a wireless channel, characterized in that the above-mentioned allocation priority is determined. 2. The wireless channel allocation method according to claim 1, wherein the changing weight is selected to be large for a new allocation availability determination result and small for an old allocation availability determination result. 3. P × λ +, where A is set to one of two values having different polarities determined in advance in accordance with the result of the assignment availability determination.
A (P is the prioritized allocation priority of the wireless channel, λ
Is calculated as a new assignment priority of the wireless channel by calculating a positive weight constant less than 1. 4. When a wireless channel is switched due to interference during communication, the allocation priority is updated with respect to the wireless channel before the switching, assuming that the determination result of the above-mentioned assignment availability determination has occurred. The wireless channel allocation method according to any one of claims 1 to 3, characterized in that: 5. It is assumed that when a wireless channel is switched due to interference during communication, a determination is made as to the assignment availability determination result for the wireless channel before the switching, but when a new wireless channel is assigned. 4. The radio channel allocation according to claim 3, wherein the allocation priority is updated by calculating P × λ + A using a value whose absolute value is smaller than the value of A used when allocation of the allocation availability determination result is not possible. Method.