JPH0645991A - Simultaneous communication system - Google Patents

Abstract

PURPOSE:To ensure a high quality communication by selecting the other base station whose reception level is the maximum, and operating a simultaneous communication by a portable terminal, when a reception level from a base station in a communication is less than a threshold value, in a mobile communication system. CONSTITUTION:When a reception level R1 from a base station all in communication is less than a threshold value H1, the mobile terminal selects a base station b42 whose reception level R2 is the maximum, and request the simultaneous communication to an exchange control station 1. The exchange control station 1 houses a line from an address outside link and the base stations a41 and b42 in a synthesizing/branching trunk T3, and connects the both base stations with the address outside link. When one of the reception levels R2 and R2 is larger than a threshold value H2 set larger than the threshold value H1, the mobile terminal informs it to the exchange control station, and the other communication is disconnected. Thus, the deterioration of a communication quality accompanied with the movement of the mobile terminal, or an instantaneous interruption or a processing delay due to a switching processing can be eleminated, and the high quality communication can be ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simultaneous communication system in a mobile communication system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a general mobile communication system. In FIG. 5, 5 is a switching control station, 61, 62, ... 6n are radio base stations, 71, 72 ,.
7 m is a mobile unit, 51 is a switch in the exchange control station 5, A,
B and C are external links. FIG. 5 shows a state in which the mobile device 71 is connected to the external link A of the exchange control station 5 via the radio base station 61. As shown in FIG. 4, in this case, the switch 51 in the exchange control station 5 connects the currently relayed radio base station 61 and the external link A.

On the other hand, one of the characteristics of the wireless communication system is the movement of a mobile unit during a call, and the mobile unit switches the radio base station with which it communicates. In FIG. 5, the mobile device 71
When the mobile terminal moves and comes close to the base station 62, the mobile device 71 will now communicate via the radio base station 62. At this time, the switch 51 in the exchange control station 5 is switched so that the external link A and the radio base station 62 are connected. As described above, in the mobile communication system, it is necessary to control the switching of the base stations during a call as the mobile device moves. This is called handoff.

[0004]

As described above, the handoff requires the switching of the switch of the switching control station, and therefore, in the conventional mobile communication system, a momentary interruption of several tens of milliseconds occurs, which causes a problem in the communication quality. As the number of handoffs increases, the processing load on the switching control station becomes a problem. This occurs especially when the mobile device is located near the boundary between the coverage areas of the two base stations, and frequent handoff occurs due to moving back and forth near the boundary.

The above handoff is mainly caused by a change in the distance from the base station due to the movement of the mobile unit, but in addition to that, even a slight movement causes the deterioration of the call quality due to shadowing and fading. But some kind of measure is necessary. Shadowing occurs when radio waves are blocked by the influence of obstacles, and fading occurs when a terminal moves and crosses a spatial standing wave generated by the synthesis of multiple reflected waves. In both cases, the reception level greatly changes with a movement of only a few tens of centimeters, so there is a big problem that it is impossible to apply the same channel switching as the conventional handoff control.

[0006]

According to the simultaneous communication system of the present invention, a portable mobile terminal in a mobile communication system uses the above-mentioned wireless when a reception level from a wireless base station in communication falls below a first threshold value. While communicating with the base station, another radio base station having the highest reception level is selected from the other radio base stations, and the radio base stations of the two stations are simultaneously communicated using different radio channels. If the reception level of one of the radio base stations becomes larger than the second threshold value during communication with the two stations, communication with the other radio base station is terminated and normal one station correspondence is performed. It is characterized by returning to the communication of.

When the reception level of one of the radio base stations becomes equal to or lower than a third threshold value which is smaller than the first threshold value during communication with the two stations, another radio base station is further provided. When the reception level of the radio base station having the maximum reception level is larger than the fourth threshold value, the communication with the radio base station having the lower reception level is terminated and the reception level maximum It is characterized by newly starting communication with the wireless base station.

[0008]

According to the present invention, deterioration of communication quality due to shadowing or fading can be avoided without frequent handoff control, and delay caused by normal handoff control can be avoided even in a low reception level area such as a boundary area. No interruption occurs.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 and 2 are flow charts of the operation of the mobile terminal showing the first and second embodiments of the simultaneous communication system of the present invention, and FIG. 3 explains the state of the switching control station in the embodiments shown in FIGS. FIG. 4 is a diagram showing a wireless section frame structure to which the simultaneous communication system of the present invention can be applied.

As shown in FIG. 3A, it is assumed that the external link A is already communicating with the base station a41 via the switch 2 of the exchange control station 1. In FIG. 1, the mobile terminal observes the reception level from the base station a41 during communication for each reception frame (step S1). Here, the reception level will be referred to as R1. Next, the reception level R1 is compared with the threshold value H1 (S2). If the reception level R1 is less than or equal to H1 (YES), the reception level of the signal frame transmitted from another base station is measured (S
3) Then, communication is started using a new channel to, for example, the base station b42 having the highest reception level among them (S4). Thereafter, the base stations a41 and b42 are simultaneously communicated. That is, the mobile device is the base station a4
The same information is transmitted to 1 and b42, and the transmission frames from both base stations are simultaneously received. During simultaneous communication, the mobile station receives the reception level R from both base stations.
1, R2 is measured (S5) and compared with the threshold value H2 (S6). If one exceeds the threshold value H2 (YE
In S), the communication with the other base station is disconnected (S7).
The threshold value H2 is set to be larger than the threshold value H1.

Next, the operation of the first embodiment will be described. At the time of being in communication with the base station a41, the switching control station 1 connects the line from the base station a41 to the destination external link A. The state of the exchange control station 1 at this time is shown in FIG. Block T3 in the figure indicates a composite / branch trunk which will be described later.

When the mobile station requests the simultaneous communication with the base station b42, the switching control station 1 once combines / extracts the destination external link and the line from the base station a41 with the branch / trunk T3.
And the line from the base station b42 is accommodated in the combining / branching trunk T3 to enter the three-party call state. The state of the exchange control station 1 at this time is shown in FIG. Synthesis here /
The branch trunk T3 does not add all the inputs like a normal three-way trunk, but rather the base stations a41 and b42.
The information input from the base stations a41 and b42 is added and the information input from the destination external link is output to the base station a41 and b42.

In this simultaneous communication state, when the mobile station makes a communication end request with one of the base stations (for example, the base station a41), the switching control station 1 then uses the line from the base station b42 and the destination external link. Is released from the combining / branching trunk T3 to directly connect the two, and the line from the base station a41 is also released from the combining / branching trunk T3. This returns to the normal one-to-one communication state with the base station b42. The state of the exchange control station at this time is shown in FIG.

Next, the operation of the mobile device according to the second embodiment of the present invention will be described with reference to FIG. The steps up to measuring the reception levels from both base stations during the simultaneous communication in S7 are the same as those in the first embodiment shown in FIG. Here, both measurement levels R1 and R2 are compared with a threshold value H2 (S
6) If one of the thresholds is equal to or more than the threshold value H2, the communication with the other base station is terminated as in the first embodiment (S7). If both are below the threshold value H2, the measurement levels of both are further compared with the threshold value H3 (S8). The threshold value H3 is set lower than the threshold value H1. If one of the base stations a41 is less than or equal to the threshold value H3, the mobile station further measures the reception level of the transmission signal from the base stations other than the communicating base stations a41 and b42 (S9), and the maximum reception level is obtained. Of the base station (referred to as base station c43), and compares the reception level of the base station c43 with the fourth threshold value H4 (S
10) If the reception level of the base station c43 is equal to or higher than the threshold value H4, the communication with the base station a41 whose reception level is equal to or lower than the threshold value H3 is terminated (S1).
1) Then, communication with the base station c43 is newly started (S12). As a result, a new simultaneous communication state with the new base station b42 and the new base station c43 is entered.

Next, the operation of the second embodiment will be described. In the simultaneous communication state with the base stations a41 and b42, the mobile station simultaneously issued a request to end communication with the base station a41 whose reception level was less than the threshold value H3 and a request to start communication with a new base station c43. in case of,
The switching control station 1 first releases the line from the base station a41 from the combining / branching trunk T3, and newly connects the line from the base station c43 to the combining / branching trunk T3. The state of the exchange control station 1 at this time is shown in FIG.

Finally, a supplement to the above description of the embodiment of the present invention will be described. In all of the above explanations, the mobile station performed an operation by comparing the reception level with each threshold value, but instead of the reception level, the level ratio of the desired wave and the interference wave, or the level of the desired wave and the noise level. A method using a ratio or the like is also possible.

Further, in the above description, the switching control station, in the state of simultaneous communication with two base stations, uses the combining / branching trunk to combine the signals from the two base stations and to send the signals from the destination external link to the two base stations. Although an example of branching has been shown, in addition to the method of using a combining / branching trunk, the switching control station compares the levels of signals from two base stations, selects only one and transmits it to the destination external link, and the destination. It is also possible to carry out the information from the external link using the broadcast function of the switch of the exchange control station.

Further, in the mobile communication system described above, it is necessary that one mobile unit can simultaneously communicate with two base stations and that the reception level of another base station can be easily measured during the communication. However, these can be realized by adopting a wireless section communication system as described below. The system using the communication frame in the wireless section shown in FIG. 4 is a system called time division multiplexing / ping-pong system, which is currently proposed for the next-generation cordless telephone system in Europe. An upstream frame from the mobile station to the base station and a downstream frame from the base station to the mobile station are multiplexed on one frequency, and a plurality of communication channels are time-division multiplexed in the upstream and downstream frames. Further, the downlink channel has a configuration in which a channel for communication information and a channel for control information are multiplexed in each communication channel. Each base station constantly broadcasts its own ID using at least one downlink communication channel control information channel. According to this frame structure, each mobile device can easily measure the reception level of another base station even during communication, and can simultaneously perform transmission / reception with a plurality of base stations.

[0019]

As described above, according to the present invention, the handoff caused by the movement between the base stations and the channel switching for preventing the deterioration of the communication quality due to the shadowing and the fading are achieved by the same means. It is possible to eliminate the effect of instantaneous interruption and deterioration of communication quality due to the switching control processing load on the switching control station and the switching processing delay. INDUSTRIAL APPLICABILITY The present invention is particularly effective for indoor wireless communication that requires high call quality.

[Brief description of drawings]

FIG. 1 is a flow chart of the operation of a mobile terminal showing a first embodiment of the simultaneous communication system of the present invention.

FIG. 2 is a flow chart of the operation of the mobile terminal showing the second embodiment of the simultaneous communication system of the present invention.

FIG. 3 is a diagram for explaining a state of a switching control station in the embodiment shown in FIGS. 1 and 2.

FIG. 4 is a diagram showing a wireless section frame structure to which the simultaneous communication system of the present invention can be applied.

FIG. 5 is a block diagram showing an example of a general mobile communication system.

[Explanation of symbols]

 1, 5 Switching control station 2, 51 Switch 3 Combined / branch trunk (T) 41, 42, 43 Base station a, b, c 61, 62, ~ 6n Radio base station 71, 72, ~ 7m Mobile station

Claims (2)

[Claims] 1. A mobile mobile terminal in a mobile communication system performs communication with the wireless base station when the reception level from the wireless base station in communication falls below a first threshold, Another radio base station having the highest reception level is selected from among the radio base stations, and the radio base stations of the two stations are simultaneously communicated using different radio channels. When the reception level of the wireless base station of 1 is larger than the second threshold, the communication with the other wireless base station is terminated and the normal communication for one station is resumed. . 2. A third reception level of one of the radio base stations during communication with the two stations is smaller than the first threshold value.
If the reception level of the other radio base station is smaller than the threshold value, and the reception level of the radio base station having the maximum reception level is larger than the fourth threshold value, the reception level is lower. 2. The simultaneous communication system according to claim 1, wherein the communication with the wireless base station of 1 is ended and the communication with the wireless base station having the maximum reception level is newly started.