JP2794980B2 - Channel allocation method for mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel allocation system for a cellular mobile communication system.

[0002]

2. Description of the Related Art In a large-capacity mobile communication system such as an automobile telephone system, a service area is covered by a plurality of base stations, and a base station which does not cause interference is repeatedly used by the same frequency channel to thereby reduce the frequency. Is being used effectively. Such a system is called a cellular system.

There are roughly two types of channel allocation methods used in each base station. One method is a method in which a channel used by each base station is fixedly assigned in advance so as not to cause interference from a prediction result of propagation characteristics, and is called a fixed channel assignment and is a general method in the current mobile telephone system. It is. Another method is
This is a method called dynamic channel allocation in which a channel that does not cause interference is selected and used for each communication.
Although the control method and device configuration are complicated, any channels can be used freely as long as interference does not occur.
There is an advantage that the number of subscribers that can be accommodated is larger than that of fixed channel assignment, and adoption thereof in a car telephone system is being studied.

In the dynamic channel assignment system, various systems have been proposed as algorithms for selecting a communication channel. In particular, a flexible reuse system is known as a system having high frequency use efficiency (documents: Shuji Yasuda, Seizou Onoe, "Mobile Communication System",
-141036, and Seiso Onoe an
d Syuji Yasuda, "Flexible
Re-useforDynamic Channel
Assignment in MobileRadio
Systems ", Conference Reco
rd of IEEE ICC '89, Boston,
June 1989. ). In this method, as shown in FIG. 3, a desired signal-to-interference-wave power ratio (hereinafter referred to as CIR) of a downlink in the own zone when each channel is used for all available channels, and an uplink in the own zone. The CIR of the line, the CIR of the uplink and the CIR of the downlink in other zones that are already using the channel are obtained, and a channel is allocated in which each CIR satisfies a required value and its average value is minimized. is there. By doing so, the repetition distance of the same frequency is shortened, and the frequency use efficiency is improved.

[0005]

In the above-described flexible reuse system, in order to preferentially allocate a communication channel having a small margin of a desired signal-to-interference wave power ratio, CIRs in all available communication channels in the own zone and other zones are used.
Is measured, the result is compared with a required value of CIR, and an average value is calculated.

An object of the present invention is to provide a channel allocation method with high frequency use efficiency without performing complicated processing.

[0007]

According to the channel allocation method of the present invention, a base station provided in each of a plurality of cells selects a communication channel from all communication channels in response to a communication request, A channel allocation method for a cellular mobile communication system for allocating a speech channel when a desired signal-to-interference wave power ratio in a channel is equal to or greater than a required value, wherein the plurality of cells include a speech channel in the same order as one another. Is selected.

[0008]

According to the present invention, in order to eliminate complicated processing such as calculation of the average value of the CIR in the own zone and other zones for all vacant channels and selection of the channel having the minimum average CIR, a fixed order is used. Select a call channel. In this case, the frequency use efficiency is improved when the communication channel selection order is the same for all cells, rather than different for each cell. The reason will be described below. Here, it is assumed that there are n communication channels in all, and that each cell is preferentially selected from the communication channel # 1. In this way, the frequency of using the communication channel is as high as that of communication channel # 1,
It becomes lower for the communication channel #n. Therefore, no matter which base station or mobile station measures the interference level of an idle communication channel, a tendency is observed that the interference level is higher for the communication channel # 1 and lower for the communication channel #n. In such a situation, if the communication channel # 1 is preferentially selected, a communication channel having a small margin of the desired signal-to-interference wave power ratio will be allocated as in the flexible reuse scheme.

Further, according to the present invention, a mobile station near the base station is assigned a high-priority communication channel having a large interference level because the desired signal level is sufficiently high.
Mobile stations distant from the base station tend to be assigned low priority traffic channels with low interference levels due to the low desired signal level. Therefore, the distance between the base station and the mobile station using each call is substantially equal, and the high-priority channel is frequently used repeatedly by the mobile station near the base station, and the low-priority channel is used. Efficient channel assignment is realized, which is used by mobile stations far from the base station at large repetition intervals. In the flexible reuse method, there is no waste because the distance between the base station and the mobile station using each communication channel is not equal.

[0010]

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

FIG. 2 shows an example of the configuration of a mobile communication system using the channel assignment method of the present invention. This mobile communication system includes an exchange 200, a base station 201,
02, a plurality of other base stations, mobile stations 203 and 204, and a plurality of other mobile stations. A base station 201 and a base station 202 are provided in cells 205 and 206, respectively. Also, Du
p, Up, Ddown, and Down are an uplink desired wave level at the base station 201, an uplink interference wave level at the base station 201, a downlink desired wave level at the mobile station 203, and a downlink interference wave level at the mobile station 203, respectively. When a call request is issued to the mobile station 203 located in the cell of the base station 201, an uplink desired wave-to-interference wave power ratio (Dup-Up) at the base station 201 and a downlink desired wave-to-interference wave power ratio at the mobile station 203 are generated. (Ddown-Udo
A communication channel whose wn) is equal to or larger than a required value is selected and used.

FIG. 1 is a flowchart for explaining the control of a base station that implements the channel assignment method of the present invention. The base station periodically determines the interference wave level Uu of the idle communication channel.
p (i) is received and stored. The transmission power of the mobile station (or less P _MS is omitted) and (abbreviated hereinafter P _BS) transmission power of the base station is assumed to be known.

When a call request is generated, the base station sets the reception level of a call request signal (in the case of a mobile station call) or a paging response signal (in the case of a mobile station call) received on the control channel to an uplink desired signal. It is stored as a level (Dup) (FIG. 1
Step 100). The next minus the Dup from P _MS,
It is assumed that a propagation loss between the base station and the mobile station (hereinafter abbreviated as L) (step 101). Reversibility holds the uplink and downlink, because the propagation loss L is considered equal, downstream desired signal level at the mobile station by subtracting the L from P _BS (Ddo
wn) can be obtained (step 102). Here, the parameter i for identifying the traffic channel is set to 1 (step 103), and the value obtained by subtracting the uplink interference wave level Up (1) of the traffic channel # 1 from Dup, that is, the desired uplink to interference power ratio and the required Value (hereinafter abbreviated as CIRth)
Are compared with each other (step 104). If the uplink desired wave-to-interference wave power ratio is equal to or more than CIRth, the base station instructs the mobile station to measure the downlink interference wave level Udown (1) of speech channel # 1, and receives the result from the mobile station (step 10).
5). Then, a value obtained by subtracting Udown (1) from Ddown, that is, the ratio of the power of the desired downlink signal to the interference wave and the CIRth are compared (step 106). As a result, if the downlink desired wave-to-interference wave power ratio is equal to or more than CIRth, the communication channel # 1
Is assigned to the call request (step 107). If the uplink desired wave-to-interference wave power ratio or the downlink desired wave-to-interference wave power ratio of the communication channel # 1 is less than CIRth, 1 is added to the parameter i to select the next channel # 2 (step 1).
09), and thereafter, similarly, 104 to 106 are repeated to determine the interference condition. A determination is made for the last communication channel #n (step 108), but if no usable communication channel is found, a call is lost (step 110).

If each base station preferentially selects from communication channel # 1 in accordance with this flowchart, a high priority channel is frequently used repeatedly by mobile stations near the base station, and a low priority channel is used by the base station. Channel allocation with high frequency use efficiency, which is used at a large repetition interval by mobile stations far from the station, can be realized.

[0015]

As described above in detail, according to the present invention, it is possible to provide a channel allocation method with high frequency use efficiency by simple control.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining control of a base station implementing a channel assignment scheme according to the present invention.

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

FIG. 3 is a flowchart for explaining a flexible reuse method in the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Measurement of desired uplink signal level 101, 102 Measurement of desired downlink signal level 103 Initial value setting of selected communication channel 104-106 Measurement of desired signal to interference power ratio 109 Update of selected communication channel 200 Exchange 202, 202 base Stations 203, 204 Mobile stations 205, 206 cells

Claims (1)

(57) [Claims] 1. A base station provided in each of a plurality of cells selects a communication channel from all communication channels in response to a call request, and a desired wave to interference wave power ratio in the communication channel is equal to or more than a required value. , A channel allocation method for a cellular mobile communication system that allocates the communication channel, wherein the plurality of cells select a communication channel in the same order as one another. Assignment method.