JPH02143725A - Multiple radio zone mobile communication system - Google Patents

Abstract

PURPOSE:To attain channel switching accurately and to reduce the control processing quantity even in a mobile equipment with fast moving speed by adopting multiple zones and selecting a connected zone in response to the state. CONSTITUTION:A service area is divided into plural small radio zones and also covered by a large radio zone simultaneously. Base stations a - g are provided on each small radio zone and other base station A is arranged respectively to a large radio zone. In the service area as above, control channels fa - fg and fA are selected as necessary in the zone of the mobile equipment 11 and communication is implemented between the selected base station and the mobile equipment 11. Thus, even in the mobile equipment 11 with fast moving speed, inaccurate channel switching is prevented and the control processing quantity is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multiple radio zone mobile communication system, and in particular, zones are installed in multiples (for example, a small radio zone and a large radio zone), and each zone is The present invention relates to a multiple radio zone mobile communication system in which a control channel for a mobile station is selected in a mobile communication system in which separate control channels are assigned to mobile devices.

[Conventional technology]

In mobile communications, in order to effectively utilize radio frequencies, the size of one radio zone is reduced, and the same frequency is repeatedly used in separate radio zones. This effect becomes larger as the zone becomes smaller, so as the capacity of mobile communication systems increases, the miniaturization of the zone is progressing more and more.

On the other hand, when zoning is performed, when a mobile station is moving while talking to a base station, there are many opportunities to enter from one wireless zone to another wireless zone. In this case, in order to be able to communicate with the mobile station without interruption, it is necessary to switch communication channels when the wireless zone changes. In addition, if this wireless channel switching is not performed accurately at the boundaries of wireless zones and channels are used outside the original wireless zone, not only will the reception level deteriorate and the call quality will deteriorate or the call will be interrupted midway. , will cause interference to channels of the same frequency that are used repeatedly.

Switching wireless channels like this requires a certain amount of time (10 to 20 seconds) for control purposes, so if you cross a wireless zone with a zone radius of several hundred meters at a speed of 60 km/h or more, channel switching may not be performed accurately. will no longer occur. Furthermore, as the frequency of channel switching increases, the control processing of base station devices and the like rapidly increases.

Additionally, with the spread of portable mobile devices, it is expected that their use at extreme visibility points such as the rooftops of buildings will increase.
When a mobile device is used in such a location, the transmitted waves from the mobile device do not suffer from normal transmission loss in a city, so in a wireless zone where the channel used by the mobile device is repeatedly used. You will be subject to interference. Due to such interference, the repetition distance of the communication channel becomes smaller as the zone becomes smaller, which causes a problem of deterioration of the quality of the communication channel.

Next, consider changes in call traffic when the zone is divided into small zones. The smaller the wireless zone, the greater the traffic fluctuation rate, and the occurrence of local congestion is expected. This is because when the wireless zone is large, the local concentration of traffic, which was averaged over the entire zone and did not pose a problem, becomes impossible to ignore as the zone becomes smaller. An example of localized traffic concentration is a case where only traffic in a specific zone is concentrated due to a concentration of cars due to traffic congestion or a concentration of people due to an event. Since such a switching state generally does not occur simultaneously in each zone, it can be avoided in large wireless zones due to the large swarm effect.

Furthermore, since the number of base stations increases due to the small zone, the probability that one of the base stations will fail becomes higher than in the case of a large zone. However, due to the large number of base stations, the economic efficiency of the base station equipment becomes important, and it is difficult to set up backups such as double equipment, and there are many stations that require time for people to rush to repair, making it difficult to recover from failures. The time required will be longer.

[Problem to be solved by the invention]

As described above, in the prior art, when zones are made smaller, channel switching for mobile devices that move at high speeds is not performed normally, and the amount of control processing increases. Furthermore, when mobile devices are connected in a place with good visibility, such as on the roof of a building, interference occurs in many zones. Furthermore, there is a problem in that an increase in the number of base stations, which are susceptible to local fluctuations in call traffic, increases the failure rate of the system as a whole.

The present invention was created in consideration of the above points, and the amount of control processing for channel switching does not increase even if the zone is made small, and interference does not occur in the zone even if the mobile device is connected in a place with good visibility. The purpose of the present invention is to provide a multiple radio zone mobile communication system that does not occur, is not affected by local fluctuations in call traffic, and does not increase the incidence of failure of the entire system due to an increase in the number of base stations. .

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention divides a service area into a plurality of small wireless zones, and includes a plurality of first base stations provided so as to correspond to each small wireless zone;
In the service area, a large wireless zone that overlaps with a plurality of small wireless zones and is larger than the small wireless zones is arranged, and a second base station is provided to correspond to the large wireless zone. 1st
Each of the base station and the second base station is assigned a wireless channel for calls and a control channel dedicated to connection control of calls. Includes mobile devices that can make calls to the nearest base station by selecting the control channel of the zone in which they are located in the service area, and select from the control channel of the small wireless zone or large wireless zone as necessary. Thus, a telephone call can be established between the first base station or the second base station and the mobile device.

[For production]

In the present invention, the service area is divided into a plurality of small wireless zones, and a large wireless zone larger than the small wireless zones is further arranged. In such a service area, a control channel is selected as necessary in the zone where the mobile device is located, and a call can be made between the selected base station and the mobile device. Each case will be explained below.

For example, this is the case when selecting one of the control channels depending on the moving speed of the mobile device. When the moving speed of the mobile device is high, the control channel is selected from among the control channels of the large wireless zone, and when the moving speed of the mobile device is slow, the control channel is selected from among the control channels of the small wireless zone. A call is established with the base station that has the selected control channel (the second base station in the case of a large wireless zone control channel, the first base station in the case of a small wireless zone control channel). .

This is also a case where control channels are selected depending on the reception level at the mobile device. When receiving multiple control channels of the small wireless zone, if the reception level of many control channels is high, select the control channel of the large wireless zone, and if the reception level of only a few control channels is high, select the control channel of the small wireless zone. Select from among the following control channels. A call connection is established between base stations having respective control channels.

Furthermore, there is a case where selection is made from among control channels depending on the congestion state of channels for communication. If the communication channels of each base station are converging, the convergence is reported on the control channel of the base station, and the mobile device is placed in a large wireless zone or a small wireless zone in which it is located, depending on whether the convergence is reported or not. Select the control channel. A call connection is established with the base station having the selected control channel. Thereby, it is possible to select the control channel on which the comparison is not broadcast.

Furthermore, if service cannot be provided at each base station due to a system failure, a control channel is selected from among the control channels depending on the failure state. That is, each base station reports the failure through its own control channel, and the mobile device selects the control channel of the large wireless zone or small wireless zone in which it is located. A call connection is established with the base station having the selected control channel. This makes it possible to select the control channel on which no failure has been reported.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example of a dual radio zone arrangement to which the present invention is applied.

In the figure, the service area is divided into a plurality of small wireless zones, but is also covered by a large wireless zone. Base stations a to g are placed in each small wireless zone, and another base station A is placed in each large wireless zone. Note that base stations located in other large wireless zones are omitted here.

A wireless channel for communication is assigned to each of the base stations a to g in the small wireless zone and the base station A in the large wireless zone. In addition, base station a in the small wireless zone
-g is assigned corresponding control channels f, ~f, and base station A in the large wireless zone is also assigned control channel fA.

These control channels f1 to f9 and fA are dedicated to controlling connection of telephone calls.

In a service area where dual wireless zones are formed in this way, the selection of a base station for a mobile device to make a call is as follows: ``(i) In the case of a mobile device traveling in an urban area.''
(ii) In the case of mobile devices used on the rooftops of high-rise buildings, etc.”
This will be explained separately below.

1'-ru Now, in the service area, it is assumed that a mobile device 11 such as a car is traveling in an urban area within a small zone of base station a. Frequency repetition distances in small zones are designed assuming large propagation losses in urban areas.
Here, it is assumed that zone a and zone d can be used repeatedly.

FIG. 2 shows a control procedure for the operation of a mobile station in an embodiment of the present invention.
, ~r9 and "," are stored.

Reference will now be made to FIGS. 1 and 2.

When the mobile device 11 is powered on, it first measures the reception levels of the control channels f8 to f in the small wireless zone for short periods of time (about several hundred milliseconds) (step 21). Now, since the mobile device 11 traveling in an urban area on the ground is within the zone of base station a, the level of the control channel f is the highest, and the levels of the other control channels rb to f are low due to propagation loss within the city. much lower than the control channel f.

Even if the mobile device 11 is located at the border of a zone, the number of control channels received at the zone peripheral level is three at most. Therefore, there is a possibility that the mobile device 11 selects and receives the control channel f. Therefore, it is determined whether there are four or more control channel reception levels that are higher than the zone peripheral level Lth (step 22). Now, if the reception level of the control channel higher than the zone peripheral level Lth is up to 3 (negative determination in step 22), then the control channel with the highest level is received (step 2).
3). Here, since the mobile device 11 traveling in a city area on the ground is within the zone of the base station a, the level of the control channel f is the highest, and the mobile device 11 receives the control channel f1.

Subsequently, it is determined whether the moving speed of the mobile device 11 is greater than or equal to 1 (step 24). If the moving speed of the mobile device 11 is equal to or higher than V (affirmative determination), the control channel f in the large radio zone will be selected.

By the way, as a method of measuring the moving speed, a method of estimating the fading pitch or the number of level crossings from fluctuations in the reception level can be considered. Regarding this, please refer to Part 6 of "Fundamentals of Mobile Communications" (written by Okumura et al.) published by the Institute of Electronics and Communication Engineers.
It is introduced on pages 7 to 70. In the case of a car, it is also possible to use the speedometer attached to the car, or to manually set it based on the user's judgment of the user of the mobile device 11.

Assuming that the moving speed is detected by either method, we will first consider the case where the moving speed is less than or equal to 1 (negative determination in step 24). In this case, the control channel r
1 is further received, and it is determined whether a comparison or a system failure has been reported (step 25). If no comparison or system failure has been reported (negative determination), the standby mode enters a state and determines whether the reception level has fallen below the zone surrounding level Lth (step 26).

Currently, the reception level is L around the zone. If the answer is above (negative determination in step 26), it is determined whether the receiver is off-hook (step 27). If it is in the off-footer state (affirmative determination), call connection control is started and call channel connection processing is performed (step 28). If it is an on-hook state (negative determination in step 27), the process returns to step 24 and repeats the procedure of determining the state of moving speed, presence or absence of notification regarding congestion or system failure, and state of reception level.

Note that if the moving speed exceeds 1, or if a collision or system failure is reported (affirmative determination in step 24.25), the control channel fA of the large wireless zone is selected. Further, if the reception level is lower than the zone surrounding level L (affirmative determination in step 26), step 21
The process returns to and repeats from the reselection of the control channels f, ~f, of the small wireless zone.

Next, consider the case of shifting to the control channel fA of the large wireless zone. Examples of this are when the reception level of control channels higher than the zone peripheral level L is four or more, when the moving speed is higher than L, and when congestion or system failure is reported. In this case, assuming that a plurality of large wireless zones are configured, the level of the control channel of each large zone is compared in the same manner as in the case of the small zone, and the control channel to be transferred is determined.

Therefore, when it is determined whether there are four or more reception levels of control channels that are higher than the zone peripheral level for the mobile device 11 (step 22), if the reception levels of the control channels that are higher than the zone peripheral level are four or higher, then (affirmative determination), the control channel shifts to the large wireless zone control channel fs. In other words, the standby mode for receiving the control channel fA remains until the handset is taken off-hook and connection control of the call is started.

The control channel f of the large wireless zone by the base station A is received (step 29). In this way the control channel f
When moving to A, the mobile device] determines whether congestion or system failure has been reported (step 30). If the base station A reports a comparison or a system failure (affirmative determination), the process returns to step 21 and reselection of the small wireless zone is executed.

On the other hand, if no interference or system failure is reported from base station A (negative determination at step 30), it is determined whether the receiver is off-footer or not at step 31.
), the call connection control is started (step 28).

If there are multiple large wireless zones, it is necessary to compare the levels of the control channels of each large wireless zone in the same way as for small wireless zones to determine which control channel should be migrated. There is. Furthermore, in the standby state, it is necessary to determine whether the reception level is lower than the surrounding level.

ii f Figure 3 shows a case where a portable mobile device is used on the roof of a high-rise building.

A case where the mobile device 31 shown in FIG. 3 selects a base station based on the order shown in FIG. 2 will be described.

When the mobile device 31 is powered on, it first measures the reception levels of control channels f and -f in the small wireless zone for short periods of time (about several hundred milliseconds) (Step 2) Compared to the case of the mobile device 11 described above in ``The case of ``, since the mobile device 31 is on the roof of a high-rise building, the control channels f1 to f of the base stations a-, -g are affected by the propagation loss in an urban area with no line of sight. Therefore, the reception level of the control channel is not only the control channel f4 of the base station d closest to the mobile device 31, but also the other control channels as well as the zone surrounding level Lth.
That's all. In particular, base stations c, e, adjacent to base station d,
H's control channel rC,r,.

f, is also sufficiently received, so in the control procedure shown in FIG. 2, this applies when the number of control channels with reception level Lth or higher is 4 or more (affirmative judgment in step 22), and the mobile device 31 is in a large radio zone. Shifts to control channel fA.

This operation is described in “(i) For a mobile device traveling in an urban area.”
This is the same as the case described above. In this way, when the mobile device 31 located in the small wireless zone of base station d makes a call in a high-rise building, etc., if it uses the communication channel of base station d, it will generate interference waves for the repeatedly placed base station a. However, in the embodiment of the present invention, since it is connected to base station A in a large zone, it is possible to prevent such interference from occurring.

According to the embodiment described above, by arranging the large zone in addition to the small zone, the zones to be connected are selected depending on the situation. As a result, by connecting a mobile device with a fast moving speed to a large zone, inaccurate channel switching can be prevented and the amount of control processing can be reduced. Furthermore, even if the mobile device connects at a place with good visibility, such as the roof of a building, interference can be prevented by connecting to a large zone. Furthermore, in response to local concentration of call traffic, overflow calls in a small zone can be relieved in a large zone. Even if some base stations in a small zone fail, service can be continued in a large zone, improving system reliability.

In the embodiment of the present invention described above, a case has been described in which one frequency is assigned to each base station as a control channel. The same applies in the case of use, provided that a similar dual radio zone arrangement is implemented for the communication channel.

Those skilled in the art will easily guess that there are various modifications to the present invention.

〔Effect of the invention〕

As mentioned above, according to the present invention, zones are multiplexed;
By selecting the connection zone according to the situation, even fast-moving mobile devices can switch channels accurately, reducing the amount of control processing, and allowing mobile devices to connect in a place with good visibility on the roof of a building. Even if a base station in a small zone fails, there is no interference, overflow calls in a small zone can be relieved in a large zone, and even if a base station in a small zone fails, service can be continued in the large zone, improving system reliability. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a multiple wireless zone mobile communication system according to an embodiment of the present invention, FIG. 2 is a flowchart showing a control procedure for explaining the multiple wireless zone mobile communication system according to an embodiment of the present invention, and FIG. FIG. 2 is an explanatory diagram of a multiple wireless zone mobile communication system according to another embodiment of the present invention. In the figure, 11.31 is the mobile device, f, ~f, , fA are the control channels, or the zone peripheral level, (1) or the moving speed. Figure 3

Claims (1)

[Claims] (1) Divide the service area into multiple small wireless zones,
A plurality of first base stations are provided to correspond to each of the small wireless zones, and a large wireless zone that overlaps the plurality of small wireless zones and is larger than the small wireless zones is placed in the service area, and a large wireless zone is provided to correspond to the plurality of small wireless zones. A second base station is assigned to each of the first base station and the second base station, and a wireless channel for calls and a control channel dedicated to connection control of calls are allocated to each of the first base station and the second base station. a mobile device capable of communicating with the nearest base station by selecting a control channel; A multiple wireless zone mobile communication system characterized in that a call connection is made between one base station or a second base station and the mobile device.