JPH08154266A - Radio communication system - Google Patents

Abstract

PURPOSE: To switch a radio channel without causing interruption in communication even when switching of a channel is required for another radio base station because a radio terminal in communication with a radio base station moves. CONSTITUTION: A reception electric field strength detection section 6 of radio base stations C1-C3 detects a reception electric field strength of a radio signal from radio terminals P1-P5 and sends the reception electric field strength value of each of the radio terminals P1-P5 to an exchange B. The reception electric field strength for a radio base station for each of the radio terminals P1-P5 and a name of the radio base stations C1-C3 connecting to a channel are stored in a base station information table 12 of the exchange B and a radio channel of the radio terminals P1-P5 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system in which a plurality of wireless base stations are arranged in a service area and a wireless circuit between each wireless base station and a wireless terminal is connected by a switch. is there.

[0002]

2. Description of the Related Art A wireless communication system of this type is, for example,
As shown in FIG. 7, a plurality of radio base stations C1 to C3 are arranged in the service area, and the radio base stations C1 to C3 are the exchanges B.
And the exchange B is further connected to a wired line such as a public line network L. The radio base stations C1 to C3 respectively have zones Z1 to Z3 which are communicable areas with the radio terminal P1. The exchange B has a wireless terminal P1 and wireless base stations C1 to C1.
The wireless line is switched to and from C3. Here, the radio base stations C1 to C3 measure the reception electric field strength of the radio signal from the radio terminal P1, and when the radio terminal P1 is located in the zones Z1 to Z3, the reception electric field strength value is obtained. Exceeds a predetermined threshold E _S.
The threshold value E _S of the electric field strength value is set to a value slightly larger than the minimum value of the electric field strength value with which communication is possible. Assuming that the wireless terminal P1 moves through the points G1 to G3, each point G1
Let E _1P1 , E _1P2 , and E _1P3 be the received electric field strength values of the wireless terminal P1 measured by the wireless base station C1 in _{G3 to G3} , respectively.
E _1P1 ＞ E _1P2 ＞ E _1P3 and point G2 is zone Z1
, The received electric field strength E _1P2 = E _S. In the radio base stations C1 to C3, the measured value of the received electric field strength of the radio terminal P1 is sent to the exchange B.
Now, it is assumed that the wireless terminal P1 located in the zone Z1 is moving while communicating with the wireless base station C1. At this time,
, The wireless terminal P1 is in the zone Z of the wireless base station C1.
Since it is within 1, the received electric field strength value E _1P1 of the wireless terminal P1 at the wireless base station C1 exceeds the threshold value E _S , and the wireless line is connected between the wireless base station C1 and the wireless terminal P1. As shown in FIG. 8, when the wireless terminal P1 reaches the position of the point G2, the received electric field strength value E _1P2 becomes equal to the threshold value E _S, and when it further approaches the point G3 from this position, the received electric field strength value E _1P2 becomes equal to the threshold value E _S. Becomes smaller than the threshold value E _S , and communication cannot be performed. In the exchange B, the measured value of the received electric field strength of the wireless terminal P1 sent from the wireless base stations C1 to C3 is compared with the threshold value E _S , and at the point G2, the received electric field strength of the wireless terminal P1 in the wireless base station C2 is In order to detect that the threshold value E _S is exceeded and to continue communication with the wireless terminal P1, the exchange B to the wireless base station C1 to the wireless terminal P are connected.
As shown in FIG. 9, the line between the switch 1 and the switch B is switched to the line between the exchange B to the wireless base station C2 to the wireless terminal P1. That is, the wireless line is connected to the wireless terminal P1 and the wireless base station C2.

[0003]

However, in the above-described radio communication system, when the radio line of the radio terminal P1 is switched to the radio line of the radio base station C2, the radio line of the radio base station C2 is changed. If all the lines are in use, the wireless line cannot be switched and the communication is interrupted.

The present invention has been made in view of the above points, and an object of the present invention is to switch a line to another wireless base station when a wireless terminal communicating with the wireless base station moves. It is another object of the present invention to provide a wireless communication system capable of switching a wireless line without interrupting communication even when a need arises.

[0005]

According to a first aspect of the present invention, a wireless terminal communicates with the wireless terminal via a wireless line, and wireless base stations installed at a plurality of locations, and the wireless base. In a wireless communication system including an exchange that switches a wireless line between a station and the wireless terminal, the wireless base station includes a reception field strength detection unit that detects a reception field strength of a wireless signal from the wireless terminal. And the reception field strength value of each wireless terminal detected by the reception field strength detection unit is sent to the exchange, and the exchange receives the reception field strength value of each wireless terminal and the name of the wireless base station connected to the line. And a radio base station information table for storing the radio base station information table, and based on each data of the received electric field strength value and the line connected radio base station name stored in the radio base station information table, It is characterized in that to perform the switching of the line circuit.

According to a second aspect of the present invention, in the first aspect of the present invention, the received electric field strength value at the wireless base station connected to the line at that time of the wireless terminal becomes smaller than the threshold value, and the received electric field strength is reduced. When switching to connect to another wireless base station whose value is larger than the threshold value, disconnect the line connection of the wireless terminal with the lowest received electric field strength among the wireless terminals that are connected to the wireless base station of the switching destination. It is characterized by having done.

According to a third aspect of the invention, in the second aspect of the invention, priority data indicating the priority of line connection of each wireless terminal is stored in the wireless base station information table, and At that time, the received electric field strength value at the wireless base station connected to the line becomes lower than the threshold value, and when switching to connect to another wireless base station whose received electric field strength value is larger than the threshold value, the priority data The wireless terminal to be disconnected is determined based on the received electric field strength value.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the determined wireless terminal to be disconnected is wirelessly connected to another wireless base station with which communication is possible. It is characterized by that.

[0009]

According to the invention of claim 1, in the radio base station, the reception electric field strength detection unit detects the reception electric field strength of the radio signal from the radio terminal, and the detected reception electric field strength value of each radio terminal is sent to the exchange. In the exchange, the base station information table stores the received electric field strength value at the wireless base station for each wireless terminal and the name of the wireless base station connected to the line, and based on these data, the wireless terminal wireless The line is switched.

According to a second aspect of the present invention, in the first aspect of the present invention, the exchange causes the received electric field strength value at the radio base station connected to the line of the radio terminal at that time to become smaller than the threshold value, and the reception When switching to connect to another wireless base station whose electric field strength value is larger than the threshold value,
Of the wireless terminals that are connected to the switching destination wireless base station,
The vacant wireless line is used by disconnecting the line connection of the wireless terminal having the smallest received electric field strength.

According to a third aspect of the invention, in the second aspect of the invention, priority data indicating the priority of line connection of each wireless terminal is stored in the wireless base station information table,
At the time of switching to connect to another wireless base station whose received electric field strength value at the wireless base station currently connected to the line of the wireless terminal becomes lower than the threshold value and whose received electric field strength value is larger than the threshold value, The wireless terminal to be disconnected is determined based on the priority data and the received electric field strength value.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the determined wireless terminal to be disconnected is wirelessly connected to another wireless base station capable of communicating, We are trying to continue communication.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a radio base station and an exchange according to an embodiment of a radio communication system of the present invention. C is a wireless base station, and as shown in FIG. 1A, an antenna 1, an RF unit 2, a modulation / demodulation unit 3, a CODEC unit 4, an exchange I / F unit 5, a reception electric field strength detection unit 6, and a communication control unit. 7 is included. The RF unit 2 receives a wireless signal from a wireless terminal within its own zone via the antenna 1 and transmits a wireless signal to the wireless terminal via the antenna 1. The modulation / demodulation unit 3 demodulates a signal received from the wireless terminal and also modulates a signal transmitted to the wireless terminal. The CODEC unit 4 decodes the demodulated received signal from the wireless terminal and also encodes the signal to be transmitted to the wireless terminal. The exchange I / F unit 5 serves as an interface for signals between itself and the exchange. The received electric field strength detection unit 6 detects the received electric field strength of the wireless signal received from the wireless terminal during communication. The communication control unit 7 controls each of the above units. That is, under the control of the communication control unit 7, the wireless signal from the wireless terminal receives the antenna 1, the RF unit 2,
Through the modem unit 3, the CODEC unit 4, and the exchange I / F unit 5, the received value of the received electric field intensity detected by the received electric field intensity detection unit 6 is also sent to the exchange. There is.

Reference numeral B denotes an exchange, which has a radio base station I / F unit 8, a line exchange unit 9, a public line network I / F unit 10 and a line control unit 11, as shown in FIG. 1 (b). Become. The wireless base station I / F unit 8 serves as an interface with the wireless base station, and is provided for each wireless base station connected to itself. The line switching unit 9 switches the line connection between the wireless terminal and the wireless base station based on the control signal from the line control unit 11. The public line network I / F unit 10 serves as an interface to the public line network,
Based on the control signal of the line control unit 11, the signal from each radio base station is sent to those to be sent to the public line network, and the signal from the public line network is taken in. The line control unit 11 controls each of the above-mentioned units, and in particular, the radio base station information table 1 internally held therein.
The control signal for switching the connection of the line between the wireless terminal and the wireless base station is sent to the line switching unit 9 with reference to the data of 2. In the wireless base station information table 12, as shown in FIG. 2, for each wireless terminal, the measured value of the received electric field strength transmitted from the wireless base station for each wireless terminal and the wireless base station name passing through, that is, the line The name of the wireless base station being connected is stored. Here, the line control unit 11 refers to the data of the radio base station information table 12 to refer to the radio terminal whose reception electric field strength value becomes smaller than a predetermined threshold value, to the radio terminal currently connected. The wireless link with the base station is controlled so as to switch to the wireless link to the wireless base station exhibiting the received electric field strength larger than the predetermined threshold value. At this time, if the wireless base station showing the received electric field strength value larger than the predetermined threshold does not have a vacant line, the received electric field strength value of the wireless terminal connected to the wireless base station is the highest. By disconnecting the line connection of a small one, the free line is used. Note that the threshold value of the electric field strength value is set to a value slightly larger than the minimum value of the communicable electric field strength value, and if the received electric field strength value becomes smaller than the threshold value, communication becomes unstable and communication becomes impossible in the end. is there. Also, as shown in FIG.
If the priority order of the line connection for each wireless terminal is set in advance in the wireless base station information table 12, for example, the line connection of the wireless terminal having the lowest received electric field strength value among some wireless terminals having a low priority order. May be disconnected.

Regarding the wireless terminal whose line connection has been cut off, a wireless line with another wireless base station whose received electric field strength is larger than a threshold value may be connected.

Next, the operation of this embodiment will be described. Now, as shown in FIG. 4, it is assumed that radio base stations C1 to C3 each having four radio lines are installed in the service area. The wireless terminal P1 located in the zone Z1 which is the communicable area of the wireless base station C1 moves in the direction from the point G1 to the point G2 while communicating with the wireless base station C1, and the communicable area of the wireless base station C2. The wireless terminals P2 to P5 are present in the zone Z2, which is in communication with the wireless base station C2. That is, the wireless terminal P1 is line-connected to the wireless base station C1, and the wireless terminals P2 to P5 are line-connected to the wireless base station C2. In the figure, the dotted line indicates that a wireless line is connected. Wireless terminal P1 is zone Z1
When it reaches the position as shown in FIG. 5 beyond the point G2 on the boundary line of the line and the received electric field strength of the wireless terminal P1 at the wireless base station C1 becomes smaller than the threshold value, the exchange B at the wireless base station C1. Data from the wireless base station information table 12 indicates that the received electric field strength value of the wireless terminal P1 is smaller than the threshold value and that the received electric field strength from the wireless terminal P1 exceeds the threshold value in the wireless base station C2. Therefore, the line between the exchange B to the radio base station C1 to the radio terminal P1 is switched to the line between the exchange B to the radio base station C2 to the radio terminal P1.

Here, the radio base station C2 is the radio terminal P2.
For communication with P5, when all four lines are in use, the line of the wireless terminal (the wireless terminal P2 in this embodiment) having the smallest received electric field strength value among the wireless terminals P2 to P5 is used. Wireless base station C
2 to the wireless lines of the wireless terminal P1 are connected.

Further, as shown in FIG. 3, as the radio base station information table 12, for example, the priority of the line connection of the radio terminals P2 to P5 is P2, P3, P4, P5 in ascending order.
If a wireless terminal to be disconnected is determined from the two wireless terminals having a low priority by considering the received electric field strength value, the wireless terminal P2 having a low priority, By comparing the received electric field strength values of P3, it is decided to disconnect the wireless terminal P2 having a smaller received electric field strength value.

Therefore, in the above embodiment, the lines between the wireless terminal P1 and the wireless base stations C1 to C3 are temporarily disconnected because all the lines are being used at the moving destination wireless base station C2. It will disappear.

In the above embodiment, when it is determined that the wireless terminal P2 is the wireless terminal to be disconnected, the exchange B refers to the received electric field strength value of the wireless terminal P2 in the wireless base stations C1 and C3, As shown in FIG. 6, the wireless terminal P
If 2 is in the zone Z3 of the radio base station C3, the received electric field strength at the radio base station C3 becomes a value larger than the threshold value and communication is possible, so the radio base station C3 and the radio terminal P
If the wireless line with the wireless terminal P is connected,
The second communication will not be interrupted.

[0021]

As described above, according to the invention of claim 1, in the radio base station, the reception electric field strength detection unit detects the reception electric field strength of the radio signal from the radio terminal, and
The detected received electric field strength value of each wireless terminal is sent to the exchange, and the exchange stores the received electric field strength value in the wireless base station of each wireless terminal and the wireless base station name connected to the base station information table. Then, based on these data, since the wireless line of the wireless terminal is switched, the wireless terminal communicating with the wireless base station moves,
It has been possible to provide a wireless communication system capable of switching a wireless line without interrupting communication even when a line needs to be switched to another wireless base station.

According to a second aspect of the present invention, in the first aspect of the invention, the exchange causes the received electric field strength value at the wireless base station connected to the line of the wireless terminal at that time to become smaller than the threshold value. , When switching to connect to another wireless base station whose received electric field strength is greater than the threshold value, make a line connection of the wireless terminal with the smallest received electric field strength among the wireless terminals that are connected to the wireless base station of the switching destination. By disconnecting, I made use of the vacant wireless line, so when the wireless terminal communicating with the wireless base station moves,
When it becomes necessary to switch the line to another wireless base station, and even if there is no free line in the wireless base station to switch to, the wireless line can be switched without interrupting communication. .

According to a third aspect of the present invention, in the second aspect of the present invention, the wireless base station information table stores priority order data indicating a priority of line connection of each wireless terminal,
The priority of the wireless terminal when switching to connect to another wireless base station whose received field strength value at the wireless base station connected to the circuit at that time is lower than the threshold and the received field strength is larger than the threshold Since the wireless terminal to be disconnected is determined based on the order data and the received electric field strength value, when determining the wireless terminal to be disconnected, the wireless terminal which should not be disconnected should be given a high priority. If so, the line connection can be preferentially continued.

In the invention according to claim 4, in the invention according to claim 2 or claim 3, the determined wireless terminal to be disconnected is connected to another wireless base station capable of communicating. Therefore, it is possible to eliminate the interruption of the communication of the determined wireless terminal to be disconnected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a wireless base station and an exchange according to an embodiment of a wireless communication system of the present invention.

FIG. 2 is a schematic diagram showing an example of a base station information table according to the above.

FIG. 3 is a schematic diagram showing another embodiment of the base station information table related to the exchange of FIG.

FIG. 4 is an operation explanatory diagram according to an embodiment of a wireless communication system of the present invention.

FIG. 5 is an operation explanatory diagram according to an embodiment of a wireless communication system of the present invention.

FIG. 6 is an operation explanatory diagram according to another embodiment of the wireless communication system of the present invention.

FIG. 7 is an operation explanatory diagram according to a conventional example.

FIG. 8 is an operation explanatory diagram according to a conventional example.

FIG. 9 is an operation explanatory diagram according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 antenna 2 RF section 3 modem section 4 CODEC section 5 exchange I / F section 6 received electric field strength detection section 7 communication control section 8 radio base station I / F section 9 circuit switching section 10 public line network I / F section 11 line control Part 12 Radio base station information table B Switch C Radio base station C1 to C3 Radio base station Z1 to Z3 Zone L Public line network P1 to P5 Radio terminal G1 to G3 Point

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04B 7/26 108 B

Claims (4)

[Claims] 1. A wireless terminal communicates with the wireless terminal via a wireless line, and a wireless base station installed at a plurality of locations, and a wireless line between the wireless base station and the wireless terminal is switched. In a wireless communication system including an exchange, the wireless base station is provided with a reception field strength detection unit that detects a reception field strength of a radio signal from the wireless terminal, and the reception field strength detection unit detects the reception field strength. The received electric field strength value of each wireless terminal is sent to the exchange, and the exchange is provided with a wireless base station information table for storing the received electric field strength value for each wireless terminal and the name of the wireless base station connected to the line, and Based on the received electric field strength value stored in the wireless base station information table and each data of the wireless base station name connected to the line, the wireless line of the wireless terminal is switched. A characteristic wireless communication system. 2. A radio base station connected to a line of a radio terminal at that point of time has a received electric field strength value smaller than a threshold value, and is connected to another radio base station whose received electric field strength value is larger than the threshold value. 2. The wireless communication system according to claim 1, wherein, when switching to the wireless communication system, the wireless terminal having the smallest received electric field strength among the wireless terminals connected to the wireless base station of the switching destination is disconnected. . 3. The wireless base station information table stores priority order data indicating the priority of line connection of each wireless terminal, and the received electric field at the wireless base station to which the wireless terminal is line connected at that time. When the strength value becomes lower than the threshold value and the connection is switched to another radio base station whose reception field strength value is larger than the threshold value, the wireless terminal to be disconnected is determined based on the priority data and the reception field strength value. The wireless communication system according to claim 2, wherein 4. The wireless communication system according to claim 2, wherein the determined wireless terminal to be disconnected is wirelessly connected to another wireless base station with which communication is possible.