JPH02200024A - Channel switching control method for moving wireless communication system - Google Patents

Abstract

PURPOSE:To always secure a communication quality by switching a speaking source channel to a switching candidate destination channel when a switching candidate destination communication level is at a prescribed value or more, and the ratio of the switching candidate destination communication level to an interfering wave level at the switching candidate destination channel is at the prescribed value or more. CONSTITUTION:One cluster C1 is formed for wireless zones Z1 to Z7 respectively around wireless base station B1 to B7, and the plural clusters are adjacently provided. In such a case, the ratio of the communication level to the interfering wave level at the communication channel is at the prescribed value or below, the switching candidate destination communication level in the other adjoining base station to the mobile station and the interfering wave level at the switching candidate destination channel to be the channel, which is not during the communication, in the base station are measured, and when the switching candidate destination communication level is at the prescribed value or more and the ratio of the switching candidate destination communication level to the interfering wave level at the switching candidate destination channel is at the prescribed value or more, the speaking source channel is switched to the switching candidate destination channel. Thus the communication quality of the all channels can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention 1 (Field of Industrial Application) The present invention relates to a channel switching control method for a mobile radio communication system in which the same frequency is commonly used in a plurality of radio zones.

(Prior art) In this type of mobile radio communication system, a radio zone is set around one radio base station in which it is possible to effectively communicate with mobile stations, and this base station and mobile stations share a radio channel. Setting up and communicating.

More specifically, what about a wireless zone configured around one wireless base station? A number of IJs are provided, and a plurality of clusters made up of the plurality of S line zones are provided adjacently. A channel of the same frequency is assigned to each corresponding wireless zone in each cluster consisting of a plurality of wireless zones, and a mobile station within each wireless zone connects to the wireless base of the wireless zone via the channel assigned to that wireless zone. Communicating with the station.

FIG. 5 shows the configuration of this mobile radio communication system. In the figure, B1. [32... B7 indicates wireless base stations, and the area surrounded by a hexagonal figure around these wireless base stations is a wireless zone, and each wireless zone is a wireless base station 81
-B7 are indicated by 71 to Z7, respectively.

Seven wireless zones 71 to Z7 each centering around the wireless base stations 81 to B7 constitute one cluster, and this cluster is shown surrounded by a thick line in the figure. A plurality of the same clusters configured in this way are set up adjacently within the service area, and even if the multiple wireless zones that make up each cluster are different, the SLJ channel of the same frequency is assigned to the corresponding wireless zone. It is being That is, as shown in FIG. 5, a first cluster C1 consisting of wireless base stations 81 to B7 and a second cluster C2 consisting of wireless base stations 81' to B7''
For example, the wireless channel of the same frequency is commonly assigned to the wireless zone of wireless base station B1 in the first cluster and the wireless zone Z- of wireless base station B1- in the second cluster. The same radio frequency channel is commonly assigned to the corresponding radio base stations, but the distance between the corresponding radio base stations is determined so as not to cause interference problems.

In this way, channels with the same frequency are assigned to wireless base stations that correspond between clusters, and the distance between base stations is determined so that there will be no interference problems, but this is just to ensure that interference does not occur on average. In reality, interference may occur depending on the positional relationship of the mobile stations.

Therefore, conventionally, when using a certain channel, the presence or absence of interference waves is checked, and if the interference wave is above a certain value, the channel is not used.

However, even with this method, it was not possible to deal with the case where the interference wave level was low before use, but then changed to become high.

In addition, the interference wave level is measured for channels that are not in communication within the same base station, and if the communication level, that is, the ratio of the desired wave level to the interference wave level, exceeds a predetermined value, the channel is not in communication. A control method such as switching between channels is used.

(Problem to be Solved by the Invention) Even with the conventional method described above, there are cases where there are no channels that are not communicating within the same base station, or there are channels that are not communicating, but the downlink (base station transmission → mobile station reception)
If there is a high correlation between the interference wave levels between the calling channel and the switching destination channel, as shown in the figure, and as a result, there is no channel where the ratio of the desired signal level to the interference wave level exceeds a predetermined value, the same frequency interference is There is a problem that it cannot be sufficiently reduced.

The present invention has been made in view of the above, and its purpose is to provide a channel switching control method for a mobile radio communication system that can accurately guarantee a predetermined call quality for all channels. It's about doing.

[Structure 1 of the Invention (Means for Solving the Problems) In order to achieve the above object, a channel switching control method for a mobile radio communication system according to the present invention provides a method for controlling channel switching in a mobile radio communication system, in which a plurality of radio A plurality of clusters consisting of wireless zones are provided adjacent to each other, and a channel of the same frequency is assigned to each corresponding wireless zone in each cluster consisting of a plurality of wireless zones, and a mobile station within each wireless zone is assigned a channel of the same frequency. A channel switching control method for a mobile wireless communication system in which a mobile station communicates with a wireless base station in a wireless zone through a channel assigned to the wireless base station, the mobile station communicating with the wireless base station using the channel assigned to the mobile station. The ratio of the communication level to the interference wave level in the calling channel is measured, and when the measured value is equal to or less than a predetermined value, the movement in another base station adjacent to the base station that is communicating with the mobile station is determined. The communication level of the switching candidate destination, which is the communication level with the base station, and the interference wave level in the switching candidate destination channel, which is a channel that is not in communication in the other base station, are measured, and the communication level of the switching candidate destination is equal to or higher than a predetermined level. , when the ratio of the interference wave level to the switching candidate communication level to the switching candidate channel J) is equal to or higher than a predetermined value, the Moeki calling channel is switched to the switching candidate channel.

(Function) In the channel switching control method for a mobile radio communication system of the present invention, when the ratio of the communication level to the interference wave level in the calling channel is less than or equal to a predetermined value, the switching candidate with the mobile station in another adjacent base station is determined. Measure the interference wave level in the switching candidate destination channel that is the channel that is not in communication in the other base station and the communication level of the destination communication level, and the communication level of the switching candidate destination is equal to or higher than a predetermined level, and the interference wave level in the switching candidate destination channel is measured. If the ratio of the switching candidate destination communication level to the switching candidate destination channel is greater than or equal to a predetermined value, the calling source channel is switched to the switching candidate destination channel.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram for explaining a channel switching control method for a mobile radio communication system according to an embodiment of the present invention.
FIGS. 2 to 4 are flowcharts explaining the operation. In addition, in the mobile and V-line communication system explained in FIG. 1, as shown in FIG.
1-[Wireless zones 71 to Z with 37 as the center
7 is formed, one cluster C1 is formed by these seven wireless zones 71 to Z7, and the raster like this is the fifth
As shown in the figure, multiple wireless zones are provided adjacently like clusters C1, C2, etc., and the multiple wireless zones that make up each cluster have the same frequency for the corresponding wireless zone even if the clusters are different. radio channels are assigned. More specifically, one wireless zone is allocated vl n channels for communication, a large number of mobile stations exist within this wireless zone, and these mobile stations communicate with base stations within that wireless zone. It is designed to communicate with. Furthermore, when the mobile FIJ station moves from the wireless zone in which it is talking to another wireless zone, it switches to the call channel used in the new wireless zone and continues the call. Note that these connection controls are described, for example, in Chapter 9 of "Automatic Telephone" edited by Moriji Kuwahara (IEICE).

In FIG. 1, wireless zones Z1. Z2. Z3 to Z7 and the adjacent wireless zone Z1-. constituting the second cluster C2. Z2-. Z3
=~Z7' is shown surrounded by a circle t'L-Fh, and each wireless zone 71~Z7. Zl"～Z7-
Radio base stations 81-87.81--B7' are shown corresponding to radio zones Z1. Mobile stations M1°M1' to M7- are shown in Zl'' to 27-.Furthermore, a radio channel control station MC3 that controls each radio base station and the like is shown.

In such a configuration, the mobile station M1 existing in the wireless zone 71 is in communication with the base station B1, which is the base station from which the call was made, and the call level of the mobile station M1 being received by the base station B1 is D. (81M1). Note that in this case, base station B2. B3. ... B7 is a base station adjacent to base station B1, and base station 81', which uses the same channel as base station B1, is in communication with mobile station M1'', and base station B
The base station 82' that uses the same channel as mobile station M
Similarly, base station 87', which uses the same channel as base station B7, is talking to mobile station M7'.

Then, the level received by the base station B1 of the mobile station Ml', which is communicating with the base station B1- which uses the same channel as the base station B1, that is, the interference wave level is defined as U (BIM
l '''), the ratio of the speech level D (81M1) of the mobile station M1 at the base station B1 to the interference wave level U (BIMl ') at the base station B1, that is, the desired signal power to interference wave power ratio (CIR) is The difference between the two in logarithmic representation is D(81M1')-U (BIMl->, and this amount of interference D(81M1)-U (81M1
′) is less than a predetermined value λ and interference deterioration occurs.

In this way, the uplink channel during which mobile station M1 is communicating with base station 81 is subject to interference, and this interference i'iD(81Ml)-
Assuming that U (BIMI = ) falls below a predetermined value λ, the calling base station B1 sends a channel switching request to the wireless network control station MC3 (as shown by line ■ in FIG. 1). Upon receiving this request, radio network control station MC8 connects base stations 82, 83 . . . adjacent to base station B1.
. . . A request for monitoring the reception level of mobile station M1 is output to B7 (route ■).

In this way, each base station B2゜83, .
B7 is the reception level D (8M1) of the mobile station M1, that is, D (
Measurement of D (82M1), D (83M1), . . . D (87M1) is started (step 110). Then, it is checked whether the reception level D (BiMl) of the mobile station M1 measured in this way is greater than or equal to the predetermined value γ (step 120).
). If the reception level D ([31M1) is equal to or higher than the predetermined value γ, step 13 checks whether there is an empty channel.
0), if there is an empty channel, the interference wave level U (Bi Mi') in that channel, that is, U (82M2-), U (83M3M, ... ()
337M7 is measured (step 140).

Then, each base station Bzt = 2 to 7) receives the reception level relative to the measured interference wave level U (Bi Mi -), that is, the desired wave level D (Bi Mi
) is the ratio of the amount of interference D(BiMi)−U(Bi Mi
), and it is checked whether the amount of interference is greater than or equal to a predetermined value λ (step 150). Then, when the amount of interference is greater than or equal to a predetermined value λ, each base station B+ receives a reception level D
(BiMl) and the amount of interference D(BiMl)−U(Bi
Mi) is transmitted to the wireless network control station MC8 and reported (step 160 and route 2 in FIG. 1). Note that in steps 120, 130, and 150, the reception level D (
When BM 1 ) is smaller than the predetermined value γ, when there is no empty channel, the interference wave amount D (Bi Ml ) −U (
If BMi) is smaller than a predetermined value λ, it is not particularly reported to the radio network control station MC8 (step 170).

The subsequent operations in the radio network control station MC3 are shown in the flowchart of FIG.
Ml) −U (Bi Mi ′) is received (
Step 210), this received reception level D (BiM
The base station Bi having the maximum value among l), for example, base station B2, is determined as the switching destination base station B. Step 220>, a switching command is sent from the calling base station B1 to the switching destination base station B2 (
step 230 and path ■).

By performing switching control between wireless base stations 8 in this way, when there are no channels that are not in use within the same base station, and even if there are channels that are not in use, it is possible to The correlation between the interference wave levels on the calling channel and the switching destination channel is high, and as a result, even if there is no channel where the ratio of the desired signal level to the interference wave level is higher than a predetermined value, interference can be avoided and the signal can be improved. This makes it possible to secure reliable calls.

In the above embodiment, the radio network control station MC8 selects the base station B with the highest reception level D (Bi Ml) and instructs it to switch from the calling base station B1 to the switching destination base station B2. However, the reception level D (Bi M
l ) instead of the amount of interference D ([3iM1)−Ll(B
The base station B with the maximum iMi −) may be selected and switched.

FIG. 4 is a flowchart showing the operation when controlling to select the maximum interference amount D(BiMl)-U(BiM') instead of the reception level D(BiMl). Step 3 in which the one with the maximum amount of interference is selected instead of step 220 in Figure 3
The only difference is that 20 is shown. By performing such control, the channel can be switched to the adjacent base station with the highest interference tolerance, and the amount of interference can be further reduced.

In addition, when combined with the conventional channel system (2I'R method) that switches channels degraded by interference to empty channels in the same zone, the adjacent base station and the own station's empty channels become candidates for switching, which further improves channel selection. The range of interference is widened, and even greater interference avoidance effects can be expected.

Note that in order to switch a call in progress to a channel of an adjacent base station, the procedure for switching a call channel in the current car telephone system for switching a call channel can be applied as is.

[Effects of the Invention] As explained above, according to the present invention, when the ratio of the communication level to the interference wave level in the calling channel is less than or equal to a predetermined value, switching candidate destinations with mobile stations in other adjacent base stations are determined. The communication level and the interference wave level in the switching candidate destination channel, which is a channel that is not in communication at the base station, are measured, and the communication level of the switching candidate destination is equal to or higher than a predetermined level, and the interference wave level in the switching candidate destination channel is measured. When the ratio of the communication level of the switching candidate destination to the switching candidate destination channel is greater than a predetermined value, the call source channel is switched to the switching candidate destination channel, so if the interference wave level increases and the call quality deteriorates, the specified call It is possible to create a tunnel that can ensure quality, and to ensure appropriate call quality at all times.As a result, the margin for the distance between interfering stations can be reduced, and frequencies can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a channel switching control method of a modern wireless communication system according to an embodiment of the present invention, and FIG.
4 are flowcharts showing the operation of the channel switching control method of the mobile radio communication system shown in FIG.
The figure is a geographical layout diagram showing the relationship among wireless zones, base stations, and clusters in the mobile network communication system. B1...Base station C1...Cluster MC8...Radio network control station Ml...Mobile station 7i...Wireless zone agent Patent attorney Hidekazu Miyoshi Figure 2 Figure 5 Procedure amendment (Spontaneous) 1999 2 5, Specification subject to amendment and Drawing 6, Engraving of the amended specification and drawings. (no change). As shown in the attached document (Amendment of representation procedure for representative case above content (voluntary) Patent 1j'i (1)5 filed on January 30, 1999 on February 8, 1999 0/-0/7/ , Subject of amendment (1) Application (2) Specification 6, Contents of amendment (1) The application is amended as shown in the attached sheet. (2) The title of the invention in the specification is "Channel switching control method for mobile radio communication system"'' shall be amended to ``Channel switching control method for mobile radio communication systems.'' Person making the amendment Name (422) Nippon Telegraph and Telephone Corporation Representative Kaio Yamaguchi

Claims (1)

[Claims] A plurality of clusters each consisting of a plurality of wireless zones each centered around at least one wireless base station are provided adjacently, and each corresponding wireless zone within each cluster consisting of a plurality of wireless zones has a channel of the same frequency. A channel switching control method for a mobile radio communication system in which a mobile station in each radio zone communicates with a radio base station in the radio zone via a channel assigned to the radio zone, the mobile station The mobile station that is communicating with the mobile station measures the ratio of the communication level to the interference wave level on the communication source channel that is the channel that is communicating, and when the measured value is less than a predetermined value, the base station that is communicating with the mobile station Measure the communication level of the switching candidate destination, which is the communication level with the mobile station in another base station adjacent to the mobile station, and the interference wave level in the switching candidate destination channel, which is a channel that is not in communication in the other base station, and When the destination communication level is at least a predetermined level and the ratio of the interference wave level in the switching candidate destination channel to the switching candidate communication level is at least a predetermined value, switching the calling source channel to the switching candidate destination channel. A channel switching control method for a mobile radio communication system, characterized in that: