JPH0691492B2 - Mobile wireless communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mobile wireless communication system, and particularly to a mobile wireless communication system such as a public car wireless system, which is based on a service area of the entire system in which a mobile station moves. Multiple service areas (wireless zones) adjacent to each other for station correspondence
The present invention relates to a mobile radio communication system in which a communication line is set up between a mobile station and a base station in which the electric field levels of radio waves coming from other stations satisfy predetermined judgment criteria.

[Conventional technology]

Conventionally, this type of mobile wireless communication system wirelessly communicates with a plurality of service areas that are divided based on a predetermined standard and are adjacent to each other and a mobile station that individually handles these service areas And a control station that controls each base station by receiving notification of the communication status between these base stations and mobile stations, and the electric field levels of the radio waves coming from the other stations are mutually In a mobile radio communication system in which a communication line is set up between a mobile station and a base station that meet predetermined criteria so that the mobile station can communicate while moving, the control station detects the usage rate of the communication line of each base station. However, when the usage rate of a certain base station exceeds a predetermined design value and there is a vacancy in the line of another base station adjacent to the one base station, the transmission power of the one base station is changed. Set to the specified value Is provided with a means for transmitting the transmission power control signal, and each base station is provided with means for changing the transmission power of its own station when receiving the transmission power control signal. By changing the range of the service area provided by the mobile radio communication system, a technique "mobile radio communication system" aiming to improve the connection rate of the entire system using the mobile radio communication system (Japanese Patent Laid-Open No. 57-210).
739) has been proposed.

[Problems to be solved by the invention]

The conventional mobile radio communication system described above measures the usage rate of the communication line (channel) for each base station, increases or decreases the transmission power of the base station between adjacent base stations, and increases the size of the service area covered by the base station. The load is distributed to the traffic by changing the height, but the following drawbacks occur for weak electric fields. That is, there is a strong positive correlation between telephone traffic and vehicle traffic, and the increase and decrease correspond to
Car traffic will increase as telephone traffic increases,
Since the time required for passing between two points also increases, the probability of disconnecting the communication channel in the weak electric field area increases. In addition, there is a drawback in that the weak electric field area is expanded by decreasing the transmission power of the base station with increased traffic, and the probability of disconnection of the communication channel is further increased.

The object of the present invention is to eliminate the above-mentioned drawbacks, measure the call line (channel) usage rate of each base station, the call line disconnection rate in a weak electric field, and determine the transmission power and the call line switch (base station switch). An object of the present invention is to provide a mobile radio communication system capable of improving a call service rate (connection rate, 1 / disconnection rate) by providing a means for changing a reception electric field level threshold value.

[Means for solving problems]

The present invention provides a plurality of base stations each of which has a plurality of service areas adjacent to each other divided based on a predetermined criterion and connects a wireless communication line to a mobile station, and a plurality of base stations from these base stations. The mobile station and the base station having a control station that controls each base station by receiving a notification of the communication status with the mobile station, and electric field levels of radio waves arriving from the other station satisfy predetermined judgment criteria. In a mobile radio communication system in which the communication line is set between the communication lines, means for detecting, in the control station, a usage rate of the communication line for each base station and a disconnection rate of a communication due to deterioration of a received electric field level. , A method of determining a transmission power value and a reception electric field level threshold value of each base station based on the detection results of the usage rate and the disconnection rate and transmitting a control signal designating these values to the corresponding base station. Means for changing, in each of the base stations, a transmission power of a transmission radio wave to the mobile station according to a designated transmission power value of the control signal, and determining effective reception of a reception radio wave from the mobile station. For changing the electric field level threshold for the control signal according to the designated received electric field level threshold of the control signal; the disconnection rate exceeds a first predetermined value, and the usage rate does not exceed a second predetermined value. To the second base station whose disconnection rate exceeds the first predetermined value and the usage rate exceeds the second predetermined value. On the other hand, the transmission power and the reception electric field level threshold are respectively increased, and the transmission power is increased for a third base station adjacent to the second base station and having a vacant communication line. Is.

[Action]

The mobile radio communication system of the present invention is provided with a plurality of base stations that individually carry a plurality of mutually adjacent service areas divided according to a predetermined standard and that communicate with a mobile station, and control for controlling these base stations. Have a station. The operating principle of the mobile wireless communication system of the present invention will be described with reference to FIGS.

FIG. 5 is an explanatory diagram showing an example of changes in the service area with respect to changes in the transmission power and the reception electric field level threshold according to the present invention. In this example, the structure is simplified in order to explain the operation principle in an easy-to-understand manner, and the transmission power of the transmission radio wave from the base station to the mobile station has two levels (P> P).
(Small), the reception electric field level threshold value of the radio wave received from the mobile station in the base station consists of 3 levels (TH large> TH medium> TH small) (the same is true for the example shown in FIG. 6). In FIG.
Base station 1 corresponding to each of service areas 101 to 107
When the transmission power of ~ 7 is the same value P is small and the reception electric field level threshold is the same value TH is small, each service range of the service areas 101 to 107 is shown by a solid line. At this time, for example, if the reception electric field level threshold value of the base station 1 in the service area 101 is kept at TH small and the transmission power is increased to P large,
The service area 101 expands as shown by a broken line 101b. Here, if the reception electric field service threshold is increased to TH (> TH small), the area of the service area 101 can be returned to the solid line, and if the reception electric field level threshold is increased to TH large (> TH), the service area is increased. It is possible to reduce the area 101 within the alternate long and short dash line 101c.

Based on the above, if the call traffic, that is, the line usage rate does not exceed the design value (for example, 70%) and the call disconnection rate due to the weak electric field exceeds the design value (for example, 20%), the corresponding base station,
For example, by increasing the transmission power of the base station 1 from a small P to a large P and increasing the reception electric field level threshold from a small TH to a large TH, the movement in the vicinity of the area boundary without changing the area of the service area 101 is performed. It is possible to improve the disconnection rate due to the weak electric field to the station (mobile device) 181 and the like.

FIG. 6 is an explanatory diagram showing a method for improving the call service rate in a service area in which both the disconnection rate due to a weak electric field and the line usage rate exceed design values. In FIG. 6, reference numerals 110 to 119 are service areas. Disconnection rate of service area 110,
It is assumed that the line usage rate is higher than each design value (20%, 70%), and only the service area 111 has a spare line out of the service areas adjacent to the service area 110, that is, the service areas 111 to 116. At this time, service area 1
Only the transmission power of the base stations 10, 11 corresponding to 10, 111 is increased from small to large, that is, from P small to P large, and the service area 112
The transmission powers of the other base stations 12 to 16 corresponding to ~ 116 are kept at P small. Further, only the reception electric field level threshold value of the base station 10 of the service area 110 is increased to TH or TH is large, and the reception electric field level threshold values of the other base stations 11 to 16 are kept at TH small.

By the above processing, the area of the service area 110 is reduced and the area of the service area 111 is expanded,
The mobile station (mobile device) 182 connected to the base station 10 comes to be connected to the base station 11, and the call volume from within the service area 110 decreases, so that the line connection rate improves. Further, by increasing the transmission power of the base station 10, the weak electric field area of the service area 110 is reduced, and the disconnection rate due to the weak electric field can be reduced.

The present invention is to provide a mobile radio communication system which can significantly improve the call service rate by using the above principle.

〔Example〕

 Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The control station 160 distributes a car telephone line (channel) 62 of a public network (not shown) to a plurality of base station-specific lines (channels) 63-1 to 63-n of a plurality of base stations 1-n and mobile stations (not shown). The line control unit 61 that controls the call of the (mobile device) and the reception level monitoring of the wireless line (call channel) during the call with the mobile station in each of the base stations 1 to n are controlled to switch the channel to the line control unit 61. Based on the information from the reception level monitoring unit 60 that supplies disconnection determination information and the reception level monitoring unit 60 and the line control unit 61, the disconnection rate, which is the rate at which a call is not normally terminated due to a weak electric field per unit time, is set. A weak electric field disconnection rate detection unit 65, a line usage rate detection unit 66 that detects a line usage rate that is a communication channel occupancy rate per unit time based on information from the line control unit 61, and a weak electric field disconnection rate detection unit. 65 and line utilization detection unit 66 detection results Based determines the transmission power value and the received field level threshold of each base station 1~n a control signal for specifying these values control signal lines 64-1 to 64-n
Transmission power / reception level threshold value setting unit 67 for transmitting to the corresponding base stations 1 to n respectively.

Each of the base stations 1 to n has the same configuration (only the base station 1 has an internal configuration shown), and the base stations 1 to n are connected to the mobile station via the transmission / reception common unit 141 in correspondence with the base station-specific lines 63-1 to 63-n. The transmission power of the transmission radio wave of the transmission unit 142 is transmitted in accordance with the control signal from the transmission unit 142 and the reception unit 144 that connect to the wireless line and transmit and receive the radio signal, and the transmission power / reception level threshold value setting unit 67 of the control station 160. An electric field level for determining effective reception of radio waves of the reception unit 144 (necessity of channel switching) in accordance with a control signal from the transmission power / reception level threshold value setting unit 67, which is also changed by the transmission power control unit 143. A reception level monitoring control unit that changes the threshold value and monitors the reception level of the received radio wave according to the threshold value and notifies the reception level monitoring unit 60 when deterioration is detected.
145 and a control unit (not shown) for controlling these. Base station-specific lines 63-1 to 63-n and control signal line 64-1 that connect these base stations 1 to n and the control station 160.
.About.64-n can be made into a single transmission line corresponding to a base station by using an appropriate well-known time division communication technique.

The basic functions and configurations of the transmission / reception shared unit 141, the transmission unit 142, the reception unit 144, and the control unit (not shown) of each base station 1 to n can be realized by an appropriate conventional technique. Is omitted. Further, the same applies to the mobile station, so description thereof will be omitted.

Next, the operation will be described. First, together with FIG. 1, FIG. 2 showing a processing flow of a base station in which the mobile station (mobile device) is in a call, FIG. 3 showing a processing flow of the control station, and movement of the mobile station (mobile device). With reference to FIG. 4 showing the processing flow of the base station, switching of a communication channel (service area) at a normal time accompanying movement of a mobile device will be described. The configuration of the service area of each base station 1 to n and the settable values of the transmission power and the reception electric field level threshold are the same as those shown in FIGS. 5 and 6, and the initial value of the transmission power is P small. In addition, it is assumed that the initial value of the reception electric field level threshold value is set to TH small.

Each of the base stations 1 to n has a mobile unit timer / timeout monitoring means and a reception level monitoring control unit 14 in a control unit (not shown).
A reception level monitoring means, a reception level determination means, and a reception level deterioration notifying means are provided in the unit 5, and the processes corresponding to steps 201 to 204 in FIG. 2 are performed. In addition, from FIG.
The connectors 1 to 3 in FIG. 4 are symbols showing the connection relationship between the respective processing flows.

In each of the base stations 1 to n, after detecting the timeout of the monitoring timer for each mobile device in the call in its own service area (step 201), the reception level monitoring means is used to receive the reception radio wave from the mobile device on the communication channel. Monitor level (step
202), a reception electric field level threshold THi (reception electric field level threshold (TH small, medium TH, TH of base station i (= 1 to n) of which the reception level is designated by the control station 160 by the reception level determination means.
(Large))) or less (step 203), and if the reception level is higher than the specified threshold, the mobile station is considered to continue to be in the same service area and the step is repeated.
Performs 201 timer monitoring processing. On the other hand, if the reception level is less than or equal to the specified threshold, it is considered that the mobile unit is approaching the boundary of the service area, and deterioration of the reception level is controlled by the control station 16.
Notify 0 (step 204). The timer value of the mobile unit timer / timeout monitoring means for instructing the timing of the reception level monitoring is determined by the size of the service area (for example, TH small, TH medium, TH large as in the service area 110 in FIG. 6). (Area corresponding to the reception electric field level threshold value) and the moving speed of the mobile device are set in advance, and in a normal case, it is, for example, about 200 ms. Further, this set value can be changed by the control station 160. Step 204 of FIG. 2 is combined with step 301 of FIG.

The control station 160 includes a reception level monitoring instruction unit in the reception level monitoring unit 60, a reception level measurement result collection unit in the line control unit 61, a reception level upper two base station detection unit, a maximum reception level base station determination unit, and a transmission power. It has a judging means, a reception level judging means, an empty channel selecting means, an empty channel notifying means, and a mobile device timer value notifying means, which respectively perform the processes corresponding to steps 301 to 310 in FIG.

In the control station 160, the transmission power / reception level threshold setting unit 67 stores the magnitude value of the transmission power and the reception electric field level threshold information designated for each of the base stations 1 to n. Upon receiving a notification of reception level deterioration from any of the base stations, the reception level monitoring unit 60 instructs the reception level monitoring instructing means to monitor the reception electric field level to the base station and the adjacent base station that have notified the reception level deterioration. Yes (step 301). The line control unit 61 collects the measurement result of the reception electric field level of the notification base station and the adjacent base station by the reception level measurement result collection means (step 302), and retrieves the measurement result by the reception level upper two base station detection means. Then, the top two base stations having the highest reception level and the next highest reception level are selected (step 303). Next, it is determined whether or not the base station with the highest reception level is the notification base station (step 304), and if the base station with the highest reception level is not the notification base station, the mobile station selects another from the service area of the notification station. It is considered that the mobile station has moved to the service area, the base station with the highest reception level (adjacent base station) is set as the movement destination base station, and the empty channel is selected (step 307). Notify (step 309). When the base station with the highest reception level is the notification base station, the line control unit 61 determines the magnitude of the transmission power of the notification base station (step 305), and when the transmission power of the notification base station is small (small P). The mobile device is considered to be moving from the weak electric field part within the service area of the notification base station to the outside of the service area of the entire mobile radio communication system, and the call channel between the notification base station and the mobile device is not changed. The communication is continued as long as possible and waits for the next notification from the base station. If the base station having the highest reception level is the notification base station and the transmission power of the notification base station is high, the reception level of the base station (adjacent base station) having the second highest reception level is further received. A comparison is made with the level threshold TH being small (step 306). If the reception level is greater than the threshold TH, the line controller 61 considers that the mobile device has already moved to the service area of the adjacent base station, selects an empty channel of the destination base station (step 308), and The base station is notified of the free channel number (step 309). On the other hand, if the reception level is less than or equal to the threshold TH, the line controller 61 considers that the mobile device is still present near the area boundary within the notification base station service area,
When changing (shortening) the monitoring period of the reception level of the received radio wave from the mobile device in order to detect the movement of the adjacent base station to the service area early, notify the notification base station of the mobile device timer value ( Step 310), waiting for the next notification from the base station. If there is no need to change the reception level monitoring cycle for the mobile device, the process of step 310 may not be performed. Step 309 in FIG. 3 is step 4 in FIG.
01 and step 310 are respectively combined with step 201 of FIG.

Each of the base stations 1 to n also has a free channel number notifying means in the control unit (not shown), and the base station notified of the free channel number by the control station 160 as the destination of the mobile device is the free channel. The number is notified to the mobile device and the call channel is switched (step 401).

Note that the line control unit 61 of the control station 160 is equal to or less than the threshold value for which the reception level for the mobile device is specified in all the base stations of the base station that has notified the reception level deterioration of the mobile device in communication and the base station adjacent to the base station. When the state of (weak electric field) continues for a predetermined time (for example, 2 seconds) or more, it is determined that the call cannot be continued even if the channel is switched, and the call line of the mobile device is disconnected. As described above, the ratio of calls that are not normally terminated due to the weak electric field among the calls connected to the line is called a disconnection rate due to the weak electric field.

Next, the cutting rate due to the weak electric field in the control station 160 (hereinafter,
The processing operation corresponding to the detection result of the disconnection rate) and the line usage rate (hereinafter, abbreviated as usage rate) will be described.

The control station 160 corresponds to the base stations 1 to n, and the reception level monitoring unit 60
Monitors the reception level of each mobile unit during a call by receiving the necessary data from the line control unit 61 and detects the weak electric field disconnection rate.
The disconnection rate is detected by 65, and the usage rate is detected by the line usage rate detection section 66. The outputs of the weak electric field disconnection rate detection section 65 and the line usage rate detection section 66 are used to transmit power / reception level threshold value setting section 67. Adjust the transmission power and reception level threshold to maximize the call service rate of the entire system. The details of the adjustment will be described below.

(1) When the disconnection rate and the usage rate both exceed the respective designed values As described in the [Operation] column, in the base station 10 in the service area 110 shown in FIG. %), And the line usage rate also exceeds its design value (for example, 70%). In this case, the transmission power of the base station 10 is increased to P and the reception electric field level threshold is increased to TH (or TH is high). Along with that, the service area
Check the usage rates of the base stations 11 to 16 in the adjacent service areas 111 to 116 of 110, and all the base stations (the usage rate is less than or equal to the design value) with a line (only the base station 11 in the example of FIG. 6). The transmission power of () is increased to P (the reception electric field level threshold remains unchanged). As a result, in the service area 110, the call traffic is reduced due to the reduction of the area and the line connection rate is improved, and the weak electric field area is reduced and the disconnection rate is reduced due to the increase of the transmission power. Note that the traffic reduction amount in the service area 110 is processed in an adjacent service area where the line has a margin and the area is expanded, and the traffic load is distributed.

(2) When the disconnection rate exceeds the design value and the line utilization rate is less than or equal to the design value As described in the [Operation] column, in the base station 1 in the service area 101 shown in FIG. 5, the disconnection rate is the designed value. However, the usage rate remains below the design value. In this case, the transmission power of the base station 1 is increased to P and the reception electric field level threshold is increased to TH. The transmission power and the reception electric field level threshold of the base stations 2 to 7 of the adjacent service areas 102 to 107 of the service area 101 are left unchanged. As a result, in the service area 101, the cutting rate is reduced without changing the area.

(3) When the disconnection rate is less than or equal to the design value and the line usage rate exceeds the design value As in the prior art (see Japanese Patent Laid-Open No. 57-210739 mentioned above), the transmission power at the base station whose usage rate exceeds the design value To increase the transmission power of a base station with a low usage rate among the adjacent base stations. The reception electric field level threshold of each base station is left unchanged. This makes it possible to balance the load of call traffic.

(4) When the cutting rate and the usage rate are both less than or equal to the design values No special processing is performed and the previous values are maintained.

As described above, both the usage rate and the disconnection rate of each base station are measured, and the transmission power to the mobile device and the reception electric field level threshold for determining the communication channel (service area) are changed according to the combination of these values. By doing so, the weak electric field area can be reduced while the load of call traffic in each service area is distributed, and the call service rate can be improved.

In the present embodiment, the transmission power of the transmission radio wave at the base station is 2 levels, and the reception electric field level threshold of the reception radio wave is 3 levels.
Although the levels are configured, the present invention is not limited thereto, and the present invention can be applied to more levels.

〔The invention's effect〕

As described above, the mobile radio communication system of the present invention allows a control station for controlling a plurality of base stations individually serving a plurality of service areas adjacent to each other, to a communication line of a mobile station for each base station. A means for detecting a call disconnection rate due to a utilization rate and a reception electric field level deterioration, and means for determining a transmission power value and a reception electric field level threshold value of each base station based on the detection results and transmitting the control signal as a control signal, For each base station,
Disconnection is provided with means for changing the transmission power of the transmission radio wave to the mobile station according to the specified value of the control signal, and means for changing the electric field level threshold value for judging the effective reception of the reception radio wave from the mobile station. For the first base station whose rate exceeds a predetermined value and whose usage rate does not exceed a predetermined value, the transmission power and the reception electric field level threshold are respectively increased, and the disconnection rate and the usage rate exceed the respective predetermined values. For each base station, the transmission power and the reception electric field level threshold are increased, and the transmission power is increased for the third base station adjacent to the second base station and having a vacant communication line. By doing so, it is possible to reduce the weak electric field area while adjusting the call traffic load sharing of each service area, so compared to the conventional method that changes the transmission power by measuring only the usage rate. Reduce the rate of cleavage by the reception electric field level degradation can be remarkably improved call service rate.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 4 is a flowchart showing the processing contents of the base station with which the mobile device is talking, FIG. 3 is a flowchart showing the processing contents of the control station, FIG. 4 is a flowchart showing the processing contents of the movement-destination base station, and FIG. FIG. 6 is a diagram for explaining a change in a service area with respect to a change in transmission power and a reception electric field level threshold in the present invention, and FIG. 6 is a method for improving a call service rate in a service area in which both a disconnection rate due to a weak electric field and a line usage rate exceed design values It is a figure for explaining. 1-7, 10-16, n ... Base station, 60 ... Reception level monitoring unit,
61 …… Line control unit, 62 …… Car phone line, 63-1 to 63-n
...... Lines by base station, 65 …… Weak electric field disconnection rate detection unit, 66 ……
Line usage rate detector, 67 ... Transmission power / reception level threshold setting unit, 101-107, 110-119 ... Service area, 142 ...
Transmitting unit, 144 ... Receiving unit, 143 ... Transmission power control unit, 145
...... Reception level monitoring control unit, 160 ...... Control station, 181,182 ...
… Mobile station (mobile device).

Claims (1)

[Claims] 1. A plurality of base stations, each of which is provided with a plurality of mutually adjacent service areas divided based on a predetermined standard, and which connects a wireless communication line to a mobile station.
The mobile station having a control station that controls each base station by receiving a notification of the communication status from the base station to the mobile station, and the electric field levels of the radio waves coming from the other station satisfy a predetermined criterion. In a mobile radio communication system in which the communication line is set up between a station and the base station to mediate communication, the control station is provided with a usage rate of the communication line for each base station and a call disconnection rate due to deterioration of a received electric field level. Means for detecting each, and determining the transmission power value and the reception electric field level threshold value of each base station based on the detection result of the usage rate and the disconnection rate, and sending the control signal designating these values to the corresponding base station Means for changing the transmission power of the transmission radio wave to the mobile station according to the designated transmission power value of the control signal to each of the base stations, and the effective reception radio wave from the mobile station. And a means for changing the electric field level threshold value for judging the signal in accordance with the designated reception electric field level threshold value of the control signal, wherein the disconnection rate exceeds a first predetermined value and the usage rate is a second predetermined value. For the first base station that does not exceed, the transmission power and the reception electric field level threshold are respectively increased, and the disconnection rate exceeds the first predetermined value and the usage rate exceeds the second predetermined value. In addition to increasing the transmission power and the reception electric field level threshold for the base station of
A mobile radio communication system characterized by increasing transmission power of a third base station adjacent to the second base station and having a vacant communication line.