JPH06209283A - Radio channel asigning system - Google Patents

Abstract

PURPOSE:To improve the frequency utilization efficiency and to shorten time to be required for the retrieval of a free channel by retrieving all the channels of the slot on a time base and asigning the carrier of the lowest quality satisfying quality to a call. CONSTITUTION:In the dynamic channel (DCA) of a TDMA radio communication, 8 plural carrier frequencies f1 to f8 perform a communication via the radio channel of the multicarrier TDMA of 3 plural time base slots T1 to T3. Arbitrary slots T1 to T3 are selected, all the corresponded channels f1 to f8 are retrieved and the carrier of the lowest quality of the carriers f1 to f8 satisfying quality is assigned to a call. At the time, when the carriers f1 to f8 satisfying quality do not exist, other slots are retrieved. By this slot unit processing, the frequency untilization efficiency can be improved because time to be required for the retrieval of a free channel is shortened as compared with the case where all the channels are processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for searching an allocated channel in dynamic channel allocation (DCA) for allocating a free channel that can be used from all wireless channels in TDMA wireless communication according to the occurrence of a call. It is a thing.

[0002]

2. Description of the Related Art Desired wave-to-interference wave power ratio (CIR) and desired wave-to-noise power ratio (C
NR), bit error rate (BER), etc., but in the following description, the case of using CIR as quality will be described. The concept is the same when the quality is defined by other than CIR.

As a conventional technique, the first available (FA) method in which the channels are sequentially searched and the one that satisfies the required CIR is assigned first, and the CIR is the most available among those that search all the channels and satisfy the required CIR. There are two methods: a method of assigning a low (bad) one (called a worst CIR method).

Each of the above methods in the case of multicarrier TDMA will be described below. In the description, the number of slots is 3, the number of carriers is 8 (the number of wireless channels is 2
4) and the required CIR is 20 dB.

FIG. 1 is a diagram for explaining dynamic channel allocation. 1a to 1c are base stations and 2a to 1c.
2c represents a wireless zone, 3a to 3e represent terminals,
(A) is dynamic channel allocation (DCA: Dy
1 shows a configuration of a mobile communication system that assigns a wireless channel by using the "Namic Channel Assignment". Each of the base stations 1a to 1c selects a CI from among the channels (24 channels: 3 slots × 8 carriers (FIG. 1B)) used in the system, depending on the occurrence of a call.
A radio channel having an R value of 20 dB or more is selected and assigned. For the sake of explanation, the wireless channels are numbered as shown in FIG. If there is no wireless channel having a CIR value of 20 dB or more, the call is lost.

Now, assume that a call originates from the terminal 3e in the radio zone 2a of the base station 1a, and the CIR value of each radio channel at that time is as shown in FIG.
In FIG. 3, it is assumed that the wireless channel number 5 is assigned for communication with the terminal 3a (this is indicated by displaying 3a at the position corresponding to the channel number 5 in FIGS. 3 and 5 to 10). ).

In the base station 1a, the radio channel 5 (slot 1, carrier 5) is used for communication with the terminal 1a. Although a wireless channel cannot be assigned to the terminal 3e, when having a plurality of wireless transmission / reception devices (corresponding to the number of carriers), it is not necessary to be aware of whether the slot is being used by the base station.

In the following description, it is assumed that there are a plurality of radio transmitter / receivers (corresponding to the number of carriers). When only one wireless transmitter / receiver is provided, the same operation is performed if each method is applied to a slot other than the slot used by the base station. (1) When the first available (FA) method is applied In the FA method, the search order is set in a certain direction as shown in FIG. 4, but in order to avoid bias in the wireless channel to be used, the wireless channel (slot (And carrier) is generally selected at random. The case where the search start channel is the radio channel number 1 and the radio channel number 18 in FIG. 2 will be described.

Since the required CIR is 20 dB, 20 dB when the search start channel is the radio channel number 1.
The wireless channel 7 (CIR value 40 dB), which is the first channel described above, is assigned to the terminal 3e (FIG. 5). The search start channel is the wireless channel number 18
In this case, the radio channel 20 (CIR value 25 dB) is assigned to the terminal 3e (FIG. 6). In these figures, the shaded sections indicate the assigned channels. This also applies to FIG.

As described above, in the FA method, the radio channel to be randomly assigned is selected from the radio channels satisfying the required CIR. On the other hand, the required CIR as much as possible
Assigning a wireless channel closer to the above (of the wireless channels that satisfy the required CIR) improves the frequency utilization efficiency because the same channel is repeatedly used at a short distance when viewed from the entire system. Desirable because

Therefore, the FA method has an unfavorable problem that the frequency utilization efficiency is lowered. (2) When the worst CIR method is applied The worst CIR method searches all radio channels
This is a method of assigning a wireless channel having the worst CIR value among the wireless channels satisfying the IR. Radio channel C
If the IR value is as shown in FIG. 3, the wireless channel number 11
(CIR value 21 dB) is assigned to the terminal 3e (FIG. 7).

According to the worst CIR method, the same channel can be repeatedly used at a short distance.
The frequency utilization efficiency can be improved as compared with the method.
However, since it is necessary to search all channels, the processing time for determining the assigned channel becomes a problem,
There is an unfavorable problem that the connection delay time from the generation of a call to the assignment of a wireless channel becomes long.

It is an object of the present invention to provide a radio channel allocation method capable of improving frequency utilization efficiency and shortening the time required to search for a vacant channel.

[0014]

According to the present invention, the above objects are achieved by the means described in the claims.

That is, the invention of claim 1 comprises a plurality of base stations, a terminal, and a radio zone formed around the base station. The base station and the terminal use a plurality of carrier frequencies. Communication is performed via a multi-carrier TDMA radio channel used by dividing into time slots,
Regarding allocation of radio channels used for communication between a base station and a terminal, in a communication system in which a base station or a terminal selects a channel that satisfies a desired quality from all the radio channels according to the occurrence of a call. For the search of the radio channel to be allocated, the slot position on the time axis to be searched first is randomly selected, the channel quality is measured for the carriers on all the frequency axes of the slot position, and one is selected for the slot. When the above carriers satisfy the predetermined quality, a radio channel is assigned to the call that has generated the carrier with the lowest quality level among the carriers satisfying the predetermined quality, and all the carriers in the slot have the predetermined quality. If it does not meet the criteria, the carrier is searched for in other slot positions and the specified quality is set first. It is a radio channel allocation method for allocating radio channels for a call which generated the carrier satisfying.

The invention of claim 2 is composed of a plurality of base stations, terminals, and a radio zone formed around the base stations. The base station and the terminals use a plurality of carrier frequencies in a plurality of time slots. Multi-carrier T used by dividing
Regarding the allocation of the wireless channel used for communication between the base station and the terminal by performing communication through the DMA wireless channel, the base station or the terminal satisfies the desired quality from all the wireless channels according to the occurrence of a call. In a communication system performed by selecting a channel to be allocated, a wireless channel to be allocated is searched first by randomly selecting a carrier on the frequency axis to be searched, and channel qualities at slot positions on all time axes on the carrier are selected. When one or more slots satisfy the predetermined quality in the carrier, the radio channel is assigned to the call of the slot having the lowest quality level among the slots satisfying the predetermined quality, and all of the carriers are allocated. If one of the slots does not meet the specified quality, search for another slot in another carrier and It is a radio channel allocation method for allocating radio channels for a call slots satisfies a predetermined quality.

[0017]

The present invention measures the qualities of all carriers (CIR values in the description of the prior art) in the slot where the search is started, and satisfies the predetermined quality when there is a channel that satisfies the predetermined quality. Of the channels, the channel with the lowest quality level is assigned. On the other hand, when there is no channel that satisfies the predetermined quality in the slot where the search is started, the FA is searched from the next slot to obtain the predetermined quality first. The main feature is to allocate the channels to be filled, and the conventional technique is different from the conventional technique in that when searching for a slot other than the slot where the search is started, F is used.
The difference is that the channel is searched by the A method.

[0018]

EXAMPLES Examples of the present invention will be described with reference to the following three examples. In this section, the communication quality is defined by CIR.
It is assumed that each base station has a plurality of (the number of carriers) wireless transmission / reception devices. When each base station has only one wireless transmitting / receiving device, the procedure described below can be applied by excluding the slot in use in the base station from the search target.

In the following description, first, a case will be described in which there is at least one radio channel satisfying the required CIR in each slot. Next, a case where there is no radio channel that satisfies the required CIR in a certain slot will be described. Finally, all radio channels require CIR
The case where the above is not satisfied will be described. (1) When there is at least one radio channel satisfying the required CIR in each slot In the system shown in FIG. 1 (a), when a call occurs at the terminal 3e, the radio channel to be assigned is selected at the base station 1a. To do.

A case will be described in which the CIR value of each radio channel at the time when a call occurs at the terminal 3e is as shown in FIG. First, a slot for starting the search is randomly selected, and a wireless channel satisfying the required CIR is searched for for all the carriers in the slot. The required CIR is now set to 20 dB.

Radio channels satisfying the required CIR are shown by hatching in FIG. Regarding the method of selecting the first slot, a typical method is to generate a random number in the base station so that the probabilities that each slot is selected are equal. Required C in search start slot
When there is a radio channel that satisfies the IR, the radio channel with the worst CIR value among the radio channels that satisfy the required CIR is assigned.

When the CIR value of each radio channel is as shown in FIG. 3, if the search start slot is the first slot, then the radio channel having the poor CIR value among the radio channels 7 and 8 satisfying the required CIR. 8 are assigned. Similarly, when the search start slot is the second slot, the wireless channel 11 is assigned, and when the search start slot is the third slot, the wireless channel 22 is assigned.

According to the worst CIR method, all radio channels are searched and the radio channel 11 (CIR value 21 dB) is assigned. However, the required CIR is also satisfied by searching all carrier frequencies for only one slot in this way. It is possible to select a wireless channel having a bad CIR value from the wireless channels. That is, the repetition distance of the same radio channel can be shortened, and the frequency utilization efficiency can be improved. Also, the time required for the wireless channel search can be reduced to 1/3 as compared with the worst CIR method. (2) When there is no radio channel that satisfies the required CIR in a certain slot A case will be described in which the CIR value of each radio channel at the time when a call is generated at the terminal 3e is the one shown in FIG. In FIG. 9, the wireless channels that satisfy the required CIR are shown by hatching.

When the search start slots are the second slot and the third slot, the required CIR is set for each slot.
Since there is a channel that satisfies the above condition, the assigned channel can be selected only by searching each slot. When the search is started from the second slot, the wireless channel 11 (CIR value 21 dB) is used. When the search is started from the third slot, the wireless channel 19 (CIR value 25 d) is used.
B) are assigned respectively.

When the search start slot is the first slot, there is no radio channel satisfying the required CIR even if all the carriers in the first slot are searched, so that the assigned radio channel cannot be selected. In this case, the process moves to the search for the next slot (second slot), but in the slots other than the search start slot, all carriers are not searched and the FA method is searched. Therefore, in the case of FIG. 9, the wireless channel 11 (CIR value 21 dB) that satisfies the required CIR is first selected on the second slot.

Since the search start slot is randomly determined, it can be considered that the number of radio channels in use is averaged among the slots. Therefore, when there is no assignable channel (radio channel that satisfies the required CIR) in the search start slot, it is considered that the number of assignable channels is small in other slots. Therefore, even if the FA method is used to search for slots other than the search start slot, if there is a wireless channel that satisfies the required CIR, the same effect as the worst CIR method (the same wireless channel is repeatedly used at a sufficiently short distance) is used. It is possible to improve the frequency utilization efficiency).

In addition, FA other than the search start slot
By performing the search by the method, the search processing time, that is, the connection delay time can be shortened as compared with the worst CIR method in which the measurement of all wireless channels is always performed. (3) When all wireless channels do not satisfy the required CIR A case will be described in which the CIR value of each wireless channel at the time when a call is generated at the terminal 3e is as shown in FIG.

In this case, since there is no radio channel satisfying the predetermined CIR, the search start slot and other 2
For all slots, all carriers are searched and it is determined that there is no assignable channel. Therefore, no radio channel is assigned to the call made at the terminal 3e, resulting in a call loss.

In the FA method, when a call is lost, all wireless channels are searched, so that the present invention does not increase the processing time. In the above description, a method of allocating a vacant channel by deciding a time slot after deciding a time slot has been described. However, the frequency is first set as in the invention of claim 2 of the "claims" of this specification. However, the same effect can be obtained even when the configuration for searching the time slot next is adopted.

[0030]

As described above, according to the present invention, there is an advantage that a high frequency utilization efficiency can be realized with a short radio channel search time.

FIG. 11 shows the result of computer simulation of comparison between the conventional method and the present invention. In the simulation, it is assumed that a wireless channel having three slots and 28 carriers (the number of channels is 84) is used in an area composed of regular hexagonal zones as shown in FIG. 12, and the relationship between the call volume and the call loss rate per zone and the channel allocation. The number of search channels required for FA method, worst CI
The R method and the present invention were determined (the shaded area in FIG. 12 represents the data acquisition cell). Call loss rate is 3%
And the relationship between the number of search channels and the traffic volume in the case of 10%,
11 (a) and 11 (b), respectively. In either case, according to the present invention, it is understood that high frequency utilization efficiency almost equal to that of the worst CIR method can be realized with about 40% of search channels (search time) of the worst CIR method.

[Brief description of drawings]

FIG. 1 is a diagram illustrating dynamic channel allocation.

FIG. 2 is a diagram showing the numbers of wireless channels.

FIG. 3 is a diagram showing a CIR value of each wireless channel.

FIG. 4 is a diagram showing a wireless channel search order in the conventional FA method.

FIG. 5 is a diagram showing a case where a search start channel is channel number 1 in the conventional FA method.

FIG. 6 is a diagram showing a case where a search start channel is a channel number 18 in the conventional FA method.

FIG. 7 is a diagram showing allocation channels in a conventional half-tone dot mesh CIR method.

FIG. 8 is a diagram illustrating a case where there is a wireless channel that satisfies a required CIR.

FIG. 9 is a diagram illustrating a case where there is no wireless channel that satisfies a required CIR in a certain slot.

FIG. 10 is a diagram illustrating a case where all wireless channels do not satisfy the required CIR.

FIG. 11 is a diagram illustrating an effect of the present invention.

FIG. 12 is a diagram illustrating a computer simulation model for confirming the effects of the present invention.

[Explanation of symbols]

 1a to 1c base stations 2a to 2c wireless zones 3a to 3d terminals

Claims (2)

[Claims] 1. A plurality of base stations, a terminal, and a radio zone formed around the base station. The base station and the terminal divide a plurality of carrier frequencies into a plurality of time slots for use. The radio channel used for communication between the base station and the terminal is used to perform communication via the radio channel of the multi-carrier TDMA, and the desired quality is selected from all the radio channels in the base station or the terminal according to the occurrence of a call. In a communication system in which a channel that satisfies the above condition is selected, a radio channel to be allocated is searched first by randomly selecting a slot position on the time axis to be searched, and by selecting a carrier on all frequency axes of the slot position. The channel quality is measured and if one or more carriers in the slot meet the required quality, then the carrier that meets the required quality is A) Allocating a radio channel to the call that generated the carrier with the lowest quality level, and if all the carriers in the slot do not meet the required quality, perform a carrier search in another slot position and first A wireless channel allocation method characterized by allocating a wireless channel to a call that has generated a carrier that satisfies the required quality. 2. A base station, a terminal, and a radio zone formed around the base station, the base station and the terminal dividing a plurality of carrier frequencies into a plurality of time slots for use. Regarding the allocation of the radio channel used for communication between the base station and the terminal, which communicates via the multi-carrier TDMA radio channel, the base station or the terminal selects the desired quality from all the radio channels according to the occurrence of a call. In a communication system in which a channel that satisfies the above condition is selected, a radio channel to be allocated is searched first by randomly selecting a carrier on the frequency axis to be searched, and channels at slot positions on all time axes on the carrier are searched. The quality is measured, and if one or more slots in the carrier satisfy the specified quality, the slot that satisfies the required quality. If the wireless channel is assigned to the call of the slot with the lowest quality level among all, and if all the slots of the carrier do not satisfy the required quality, the slot is searched for on another carrier and the required quality is determined first. Radio channel allocation method characterized by allocating radio channels for calls in filled slots