JP3057189B2 - Wireless channel assignment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of searching for an allocated channel in dynamic channel allocation (DCA) for allocating an available free channel from all radio channels in accordance with the occurrence of a call in TDMA radio communication. Things.

[0002]

2. Description of the Related Art The quality of communication is defined by a desired wave to interference power ratio (CIR) and a desired wave to noise power ratio (CIR).
NR), bit error rate (BER), and the like. In the following description, the case where CIR is used as the quality will be described. The concept is the same when the quality is specified by other than CIR.

[0003] As a conventional technique, a first available (FA) method in which channels are searched in order and the one that satisfies a required CIR is assigned first, and the CIR of the one that searches all channels and satisfies the required CIR is the most effective There are two methods, a method of assigning a low (bad) one (referred to as a worst CIR method).

[0004] Each of the above methods in the case of multi-carrier TDMA will be described below. In the description, the number of slots is 3 and the number of carriers is 8 (the number of radio channels is 2
4), and the required CIR is 20 dB.

FIG. 1 is a diagram for explaining dynamic channel assignment, wherein reference numerals 1a to 1c denote base stations and 2a to 2c.
2c represents a wireless zone, 3a to 3e represent terminals,
(A) shows dynamic channel assignment (DCA: Dy)
1 shows a configuration of a mobile communication system that allocates a wireless channel by using a native channel assignment. Each of the base stations 1a to 1c selects one of the channels (24 channels: 3 slots × 8 carriers (FIG. 1B)) used in the system according to the generation of a call.
A radio channel having an R value of 20 dB or more is selected and assigned. For the purpose 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 blocked.

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

In the base station 1a, the wireless channel 5 (slot 1, carrier 5) is used for communication with the terminal 1a. The wireless channel cannot be assigned to the terminal 3e, but when there are a plurality of wireless transmitting / receiving apparatuses (for 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 a plurality of wireless transmitting / receiving apparatuses (for the number of carriers) are provided. In the case where only one wireless transmitting / receiving apparatus is provided, the same operation is performed if each method is applied to slots other than the slot being used in the base station. (1) When the first available (FA) method is applied In the FA method, the search order is determined in a certain direction as shown in FIG. And carrier) at random. The case where the search start channel is the wireless channel number 1 and the case where the search channel is the wireless channel number 18 in FIG. 2 will be described.

[0009] Since the required CIR is 20 dB, if the search start channel is the wireless channel number 1, the required CIR is 20 dB.
The wireless channel 7 (CIR value 40 dB) as the first channel described above is allocated to the terminal 3e (FIG. 5). The search start channel is the wireless channel number 18
In the case of, the radio channel 20 (CIR value 25 dB) is allocated to the terminal 3e (FIG. 6). In these figures, the hatched sections indicate the assigned channels. This is the same in FIG.

As described above, in the FA method, a radio channel to be randomly assigned is selected from radio channels satisfying a required CIR. On the other hand, the required CIR
Allocating a wireless channel closer to the above (of the wireless channels satisfying the required CIR) means that the same channel is repeatedly used at a shorter distance when viewed from the whole system, so that the frequency use efficiency is improved. It is desirable to

Therefore, the FA method has an undesired problem that the frequency utilization efficiency is reduced. (2) When the Worst CIR Method is Applied The worst CIR method searches all radio channels,
This is a method of allocating a radio channel having the worst CIR value among radio channels satisfying IR. C of wireless channel
When the IR value is as shown in FIG.
(CIR value 21 dB) is allocated to the terminal 3e (FIG. 7).

According to the worst CIR method, the same channel can be used repeatedly at a short distance.
The frequency use 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 undesired problem that the connection delay time from the occurrence of a call to the assignment of a wireless channel becomes long.

An object of the present invention is to provide a radio channel allocation method capable of improving the frequency use efficiency and reducing the time required for searching for an empty channel.

[0014]

According to the present invention, the above-mentioned object is 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, and the base station and the terminal transmit a plurality of carrier frequencies to a plurality of carriers. Perform communication through a multi-carrier TDMA radio channel used by dividing into time slots,
Assignment of a radio channel used for communication between a base station and a terminal is performed in a communication system performed by selecting a channel that satisfies a desired quality from all the radio channels in a base station or a terminal according to occurrence of a call. In the search for a radio channel to be allocated, a slot position on the time axis to be searched first is selected at random, channel quality is measured for carriers on all frequency axes at the slot position, and one channel is searched in the slot. When the above carriers satisfy the predetermined quality, a radio channel is allocated to a 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 not, search for a carrier at another slot position, and It is a radio channel allocation method for allocating radio channels for a call which generated the carrier satisfying.

According to a second aspect of the present invention, there are provided a plurality of base stations, a terminal, and a radio zone formed around the base station. The base station and the terminal assign a plurality of carrier frequencies to a plurality of time slots. Multicarrier T used by dividing
Communication is performed via the DMA radio channel, and the assignment of the radio channel used for communication between the base station and the terminal satisfies the desired quality from among all the radio channels in the base station or the terminal according to the occurrence of a call. In a communication system performed by selecting a channel to perform, a search for a radio channel to be allocated is performed by first randomly selecting a carrier on the frequency axis to be searched, and channel quality at all slot positions on the time axis on the carrier. When one or more slots satisfy predetermined quality in the carrier, a radio channel is allocated to a call of a slot having the lowest quality level among slots satisfying the predetermined quality, and all the carriers of the carrier are assigned. If the slot does not satisfy the predetermined quality, search for a 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]

According to the present invention, the quality of all carriers (CIR value in the description of the prior art) is measured in the slot where the search is started, and if there is a channel satisfying the predetermined quality, the quality is satisfied. If the channel having the lowest quality level among the channels is assigned, and there is no channel satisfying the predetermined quality in the slot from which the search has been started, the next slot is searched by the FA method, and the predetermined quality is first determined. The main feature of the present invention is to allocate a channel to be filled.
The difference is that the channel is searched by the method A.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the following three examples. In this section, the communication quality is also specified by CIR
It is assumed that each base station has a plurality of (for the number of carriers) wireless transmission / reception devices. When each base station has only one wireless transmission / reception device, the procedure described below can be applied by excluding a slot being used in the base station from the search target.

In the following description, first, a case will be described in which at least one radio channel that satisfies the required CIR exists in each slot. Next, a case where there is no wireless channel satisfying the required CIR in a certain slot will be described. Finally, all radio channels have the required CIR
The case in which is not satisfied will be described. (1) When at least one radio channel that satisfies the required CIR exists in each slot In the system shown in FIG. 1A, when a call is generated in the terminal 3e, the base station 1a selects a radio channel to be allocated. I do.

The case where the CIR value of each radio channel at the time when a call is generated at the terminal 3e is as shown in FIG. 8 will be described. First, a slot for starting a search is selected at random, and for that slot, a wireless channel that satisfies a required CIR is searched for all carriers. Now assume that the required CIR is 20 dB.

Radio channels satisfying the required CIR are shown by hatching in FIG. A typical method of selecting the first slot is to generate a random number in the base station so that the probability of selecting each slot is equal. Required C in search start slot
If there is a wireless channel satisfying the IR, the wireless channel having the worst CIR value among the wireless channels satisfying the required CIR is assigned.

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

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

When the search start slot is the second slot and the third slot, the required CIR is assigned to each slot.
Is present, 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 started. When the search is started from the third slot, the wireless channel 19 (CIR value 25d) is started.
B) are respectively assigned.

If the search start slot is the first slot, there is no radio channel that satisfies the required CIR even if all carriers on the first slot are searched, so that it is not possible to select an allocated radio channel. In this case, the process proceeds to the search for the next slot (second slot). However, in the slots other than the search start slot, the search is not performed on all carriers but by the FA method. Therefore, in the case of FIG. 9, the radio channel 11 (CIR value 21 dB) satisfying the required CIR is first selected on the second slot.

Since the search start slot is determined randomly, it can be considered that the number of radio channels in use is averaged among the slots. Therefore, when there is no allocatable channel (wireless channel satisfying the required CIR) in the search start slot, it can be considered that the number of allocatable channels in other slots is small. Therefore, even if a search is performed by the FA method in a slot other than the search start slot, if there is a wireless channel satisfying the required CIR, the same effect as the worst CIR method (the same wireless channel is repeatedly used at a sufficiently short distance) 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 reduced as compared with the worst CIR method in which the measurement of all wireless channels is always performed. (3) Case where All Radio Channels Do Not Satisfy Required CIR A case where the CIR value of each radio channel at the time when a call is generated at the terminal 3e is as shown in FIG. 10 will be described.

In this case, since there is no radio channel satisfying the predetermined CIR, the search start slot and other 2
All carriers are searched for slots, and it is determined that there is no assignable channel. Therefore, a call generated at the terminal 3e is not assigned a radio channel, resulting in a call loss.

In the FA method, if a call is lost, all wireless channels are searched, and the present invention does not increase the processing time. In the above description, a method of allocating an empty channel by searching for a frequency after determining a time slot is described. However, as in the invention of claim 2 of this specification, a frequency is first set. However, a similar effect can be obtained even when a configuration in which a time slot is searched next is adopted.

[0030]

As described above, the present invention has an advantage that high frequency use efficiency can be realized in a short radio channel search time.

FIG. 11 shows the result of a computer simulation of the comparison between the conventional method and the present invention. In the simulation, it is assumed that a wireless channel (the number of channels 84) having 3 slots and 28 carriers is used in an area composed of regular hexagonal zones as shown in FIG. Method, the worst CI
The R method and the present invention were obtained (the hatched portions in FIG. 12 indicate data acquisition cells). Call blocking rate is 3%
And the relationship between the number of search channels and the traffic in the case of 10%,
These are shown in FIG. 11A and FIG. 11B, respectively. In any case, according to the present invention, it can be seen that high frequency use efficiency almost equivalent to the worst CIR method is realized with about 40% of the number of search channels (search time) of the worst CIR method.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating dynamic channel assignment.

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

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

FIG. 4 is a diagram illustrating a search order of wireless channels in a conventional FA method.

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

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

FIG. 7 is a diagram illustrating channels assigned by the conventional hatched worst CIR method.

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

FIG. 9 is a diagram illustrating a case where a radio channel satisfying a required CIR does not exist in a certain slot.

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

FIG. 11 is a diagram illustrating the 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-1c Base station 2a-2c Wireless zone 3a-3d Terminal

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B ^7/ 24-7/26 102 H04Q ^7/ 00-7/38

Claims (2)

(57) [Claims] 1. A system comprising a plurality of base stations, a terminal, and a radio zone formed around the base station, wherein the base station and the terminal divide a plurality of carrier frequencies into a plurality of time slots for use. Communication is performed via a multi-carrier TDMA radio channel, and a radio channel used for communication between the base station and the terminal is allocated to the base station or the terminal according to the occurrence of a call. In a communication system performed by selecting a channel that satisfies the following conditions, a search for a wireless channel to be allocated is performed by first randomly selecting a slot position on the time axis to be searched, and searching for carriers on all frequency axes at the slot position. Measure the channel quality, and if one or more carriers satisfy the required quality in the slot, If a radio channel is assigned to a call that has generated the carrier with the lowest quality level out of all the channels, and if all the carriers in the slot do not meet the required quality, a search for carriers is performed in other slot positions. A radio channel assignment method, wherein a radio channel is assigned to a call that generates a carrier satisfying required quality. 2. A base station comprising a plurality of base stations, a terminal, and a radio zone formed around the base station, wherein the base station and the terminal divide a plurality of carrier frequencies into a plurality of time slots for use. Communication is performed via a multi-carrier TDMA radio channel. Regarding the assignment of a radio channel used for communication between the base station and the terminal, the base station or the terminal determines the desired quality from among all the radio channels in accordance with the occurrence of a call. In a communication system performed by selecting a channel that satisfies the following, a search for a radio channel to be allocated is performed by first randomly selecting a carrier on a frequency axis to be searched, and a channel at all slot positions on the time axis on the carrier. The quality is measured, and if at least one slot in the carrier satisfies the predetermined quality, the slot satisfying the required quality is used. The radio channel is allocated to the call of the slot with the lowest quality level, and if all the slots of the carrier do not meet the required quality, a search is made for slots on other carriers, and the required quality is first determined. Radio channel allocation scheme for allocating radio channels to calls in filled slots