JPH04351126A - Channel allocation system for mobile communication system - Google Patents

Abstract

PURPOSE:To attain the channel allocation giving a high frequency utilizing efficiency with a simple control by allowing plural cells to select a talking channel according to the same sequence. CONSTITUTION:The system consists of an exchange station 200, base stations 201, 202, other plural base stations 203, 204, and other plural mobile stations and a cell 205 (206) is provided with the base station 201 (202). In this case, an incoming desired wave level of the base station 201 is referred to as Dup, an incoming interference wave level of the base station 202 is referred to as Uup, an outgoing desired wave level of the mobile station 203 is referred to as Ddown, and outgoing interference wave level of the mobile station 203 is referred to as Udown. When a talking request takes place in the mobile station 203 resident in the cell of the base station 201, a talking channel is selected and used, in which an incoming desired wave versus interference wave power ratio (Dup-Uup) in the base station 201 and an outgoing desired wave versus interference wave power ratio (Ddown-Udown) in the mobile station 203 are required ratios or above.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art] In a large-capacity mobile communication system such as a car telephone system, a service area is covered by a plurality of base stations, and the same frequency channel is repeatedly used between the base stations where interference does not occur. We are trying to make effective use of this. This type of system is called a cellular system.

[0003] There are roughly two types of channel allocation methods used in each base station. One method is to allocate channels for each base station in a fixed manner based on the prediction results of propagation characteristics in order to prevent interference from occurring. This method is called fixed channel allocation and is common in current car phone systems. It is. Another method 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 equipment configuration are complicated, any channel can be used freely as long as no interference occurs.
It has the advantage of accommodating a larger number of subscribers than fixed channel allocation, and its adoption in car telephone systems is also being considered.

In the dynamic channel allocation method, various methods have been proposed as algorithms for selecting communication channels. The flexible reuse method is known as a method with particularly high frequency utilization efficiency (Reference: Shuji Yasuda, Seizo Onoe, "Mobile Communication System", Japanese Patent Application Laid-open No. 2003-20020-1.
141036 publication, and Seizo Onoe a
nd Syuji Yasuda, “Flexib
le Re-use for Dynamic Cha
nnel Assignment in Mob
ileRadio Systems”,Confer
ence Record of IEEE ICC
'89, Boston, June 1989
．． ). As shown in Figure 3, this method calculates the downlink desired to interference power ratio (hereinafter referred to as CIR) in its own zone when each channel is used, and the uplink power ratio in its own zone, as shown in Figure 3. Determine the CIR of the line, the CIR of the uplink, and the CIR of the downlink in other zones that are already using that channel, and calculate each CIR.
satisfies the required value and the channel whose average value is the minimum is allocated. By doing so, the repetition distance of the same frequency is shortened, and frequency utilization efficiency is improved.

[0005]

[Problem to be Solved by the Invention] In the above-mentioned flexible reuse system, in order to prioritize and allocate communication channels with a small margin of desired signal to interference signal power ratio, the CIR of all vacant communication channels in the own zone and other zones is
It is necessary to measure the CIR, compare the results with the required value of CIR, and calculate the average value.

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

[0007]

[Means for Solving the Problems] In the channel allocation method of the invention of the present application, a base station provided in each of a plurality of cells selects a communication channel from among all communication channels in response to a communication request, and A channel allocation method for a cellular mobile communication system that allocates the communication channel when the desired wave to interference wave power ratio in the channel is equal to or higher than a required value, wherein the plurality of cells mutually allocate the communication channels in the same order. It is characterized by selecting.

[0008]

[Operation] In the present invention, in order to eliminate the need for complicated processing such as calculating the average value of CIR in the own zone and other zones for all vacant channels and selecting the channel with the minimum average CIR, Select a call channel. In this case, frequency utilization efficiency is improved by making the selection order of communication channels the same in all cells rather than making them different for each cell. The reason for this will be explained below. Here, it is assumed that there are a total of n communication channels, and each cell selects communication channel #1 preferentially. In this way, the frequency in which a call channel is used is higher as call channel #1 is used,
It becomes lower as the communication channel #n increases. Therefore, no matter which base station or which mobile station measures the interference level of an idle communication channel, it is observed that the interference level tends to be higher in communication channel #1 and smaller in communication channel #n. In such a situation, if the communication channel #1 is selected preferentially, a communication channel with a small margin in the desired wave to interference wave power ratio will be allocated, as in the flexible reuse method.

Furthermore, according to the present invention, a high-priority communication channel with a large interference level is assigned to a mobile station near a base station because the desired signal level is sufficiently large;
For mobile stations located far from the base station, there is a tendency for a low-priority traffic channel with a low interference level to be assigned because the desired signal level is low. Therefore, the distance between the base station and mobile station using each call will be approximately the same, and high priority channels will be used repeatedly by mobile stations near the base station, while low priority channels will be used repeatedly by mobile stations near the base station. Efficient channel allocation is achieved in that mobile stations located far from the base station are used at larger repetition intervals. In the flexible reuse system, the distances between the base station and mobile station using each communication channel are never the same, resulting in waste.

0010

Embodiments Next, embodiments 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 in which the channel allocation method of the present invention is used. This mobile communication system includes a switching center 200, base stations 201, 2
02 and other plural base stations, mobile stations 203 and 204 and other plural mobile stations, and a base station 201 and a base station 202 are provided in cells 205 and 206. Also, Dup
, Uup, Ddown, and Udown are the uplink desired wave level at the base station 201, the uplink interference wave level at the base station 201, the downlink desired wave level at the mobile station 203, and the downlink interference wave level at the mobile station 203, respectively. When a call request occurs to a mobile station 203 located in the cell of the base station 201, the uplink desired wave to interference wave power ratio (Dup-Uup) at the base station 201 and the downlink desired wave to interference wave power ratio at the mobile station 203. (Ddown-Udow
Select and use a communication channel for which n) is greater than or equal to the required value.

FIG. 1 is a flowchart for explaining control of a base station implementing the channel allocation method of the present invention. The base station periodically checks the interference wave level Uu of the idle communication channel.
p(i) is received and stored. In addition, mobile station transmission power (hereinafter abbreviated as PMS) and base station transmission power (hereinafter referred to as PB)
S) is assumed to be known.

[0013] When a call request occurs, the base station uses the reception level of the call request signal (in the case of a mobile station call) or the paging response signal (in the case of a mobile station call) received on the control channel as an uplink desired signal. Stored as level (Dup) (Figure 1
Step 100). Next, the value obtained by subtracting Dup from PMS is defined as the propagation loss between the base station and the mobile station (hereinafter abbreviated as L) (
Step 101). Since reversibility is established in the uplink and downlink, and the propagation loss L is considered to be the same, the L
By subtracting the downlink desired wave level (D
(step 102). Here, the parameter i for identifying the call channel is set to 1 (step 103), and the call channel #1 is set from Dup to call channel #1.
The value obtained by subtracting the uplink interference wave level Uup(1), that is, the uplink desired wave to interference wave power ratio, is compared with a required value (hereinafter abbreviated as CIRth) (step 104). When the uplink desired wave to interference wave power ratio is greater than or equal to CIRth, the base station informs the mobile station of the downlink interference wave level Udown (1) of communication channel #1.
instruct the measurement of the mobile station and receive the results from the mobile station (Step 1)
05). Then, the value obtained by subtracting Udown (1) from Ddown, that is, the downlink desired wave to interference wave power ratio, is compared with CIRth (step 106). As a result, if the downlink desired wave to interference wave power ratio is also greater than or equal to CIRth, the communication channel #
1 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 communication channel #1 is less than CIRth, add 1 to parameter i and select the next channel #2 (step 109), and the same goes. Interference conditions are determined by repeating steps 104 to 106. The last call channel #n is judged (step 108), but if no usable call channel is found, the call is lost (
Step 110).

[0014] If each base station preferentially selects communication channel #1 according to this flowchart, channels with high priority will be frequently and repeatedly used by mobile stations near the base station, and channels with low priority will be used repeatedly by mobile stations near the base station. It is possible to realize channel allocation with high frequency utilization efficiency, in which mobile stations located far from the station are used at large repetition intervals.

[0015]

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

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining control of a base station that implements the channel allocation method of 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 conventional technology.

[Explanation of symbols]

100 Measurement of uplink desired wave level 101, 102 Measurement of downlink desired wave level 103
Setting the initial value of the selected communication channel 104 to 106 Measuring the desired wave to interference wave power ratio 109 Updating the selected communication channel 200 Switching center 202, 202 Base station 203, 204 Mobile station 205, 206 Cell

Claims (1)

[Claims] Claim 1: A base station provided in each of a plurality of cells selects a communication channel from among all communication channels in response to a communication request, and selects a communication channel from among all communication channels, and selects a communication channel from among all communication channels in response to a communication request, and selects a communication channel in which the power ratio of desired waves to interference waves in the communication channel is equal to or greater than a required value. A channel allocation method for a cellular mobile communication system in which the communication channels are allocated in the case where the communication channels are selected according to the same order in which the plurality of cells mutually select communication channels. Allocation method.