JPH07274232A - Method for supervising peripheral base station - Google Patents

Abstract

PURPOSE:To supervise a peripheral base station efficiently while minimizing the deterioration in the communication quality for the current communication with respect to the supervisory system for the peripheral base station to allow a mobile station to select a radio zone of a transfer destination in the mobile communication system. CONSTITUTION:A mobile station measures communication quality with a radio base station for the communication (1), the mobile station starts supervision of a peripheral base station when the mobile station discriminates the occurrence of communication quality deterioration after that (2, 4), and the mobile station predicts the time when the succeeding communication quality deterioration based on the measurement result of the communication quality to set a time to continue the supervision of the peripheral base station (3), while the mobile station supervises the peripheral base station, the communication with the radio base station is stopped and the communication with the radio base station is restarted after the lapse of time for continuing the supervision of the peripheral base station set in advance (5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system, in which a mobile station takes a initiative in selecting a destination wireless zone when the mobile station shifts the wireless zone during communication, thereby contributing to channel switching. It is related to the monitoring of mid-peripheral base stations.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a system configuration of a mobile communication system, in which a radio base station 41 forms a radio zone 42 and shows a state of communicating with a mobile station 43 existing in the radio zone 42. Shows.

The mobile station 43 moves in the direction of the arrow while communicating, and moves to the destination wireless zone (the wireless zone 45 in the illustrated example).
When the channel is switched to the wireless base station (the wireless base station 44 in the example shown in the figure) that forms the network and the communication is continued, the mobile station 43 itself sends out to the peripheral base stations (44, 46, 48 in the figure). Measure the signal level to identify the target wireless zone.

FIG. 5 is a diagram for explaining a method of measuring a transmission level of a peripheral base station of a time division multiple access (TDMA) mobile communication system. The horizontal direction in the figure represents the passage of time.
Now, the mobile station 43 receives the reception timing 51 at the radio base station 41.
Suppose you are communicating with. In this case, the peripheral base station transmission level measurement is performed in a period other than the reception timing 51. At that time, the synthesizer set frequency for the receiver in the mobile station is shown in the figure.

FIG. 6 is a diagram for explaining a method of measuring the transmission level of neighboring base stations after detecting the deterioration of communication quality. In this case, when the mobile station 43 detects quality deterioration during communication with the radio base station 41 (61 in the figure), it disconnects the line with the radio base station 41 and measures the transmission level of neighboring base stations. The synthesizer set frequency for the receiver in the mobile station at that time is shown in the figure.

[0006]

Since the method described above with reference to FIG. 5 is premised on the TDMA mobile communication method, it cannot be applied to any method other than TDMA. Further, if the TDMA frame length (52 in FIG. 5) becomes short, the peripheral base station monitoring time for the TDMA frame length 52 also becomes short. Therefore, in order to measure the peripheral base station transmission level which fluctuates due to fading or the like with high accuracy, There is a drawback that the number of base station monitoring increases.

Further, if the interval between the reception timing 51 and the next reception timing 51 becomes shorter than the synthesizer switching time, the peripheral base station cannot be monitored, so that the communication must be interrupted. In such a case, the method described with reference to FIG. 6 is applied, but in this case, since the transfer destination wireless zone cannot be specified before the communication quality deteriorates, a search for a neighboring base station is not performed at the time of channel switching. Will result. Therefore, since the peripheral base station is continuously monitored after the quality deterioration, the communication interruption time becomes long and, as a result, the communication quality deteriorates remarkably.

[0008] The present invention makes it possible to minimize the deterioration of communication quality and efficiently specify the transfer destination wireless zone when the peripheral base station is monitored during communication.
It is an object of the present invention to provide a peripheral base station monitoring method applicable not only to the TDMA method as described above but also to other methods.

[0009]

According to the invention, the aforesaid problems are solved by the means defined in the claims.

That is, according to the invention of claim 1, the mobile station
After starting communication with the wireless base station in the wireless zone in which you are located,
A peripheral base station monitoring method for monitoring a signal sent from a peripheral base station by the mobile station, wherein the mobile station measures communication quality with a wireless base station in communication, and a measurement result of the communication quality. Then, when it is determined that the communication quality deterioration will occur thereafter, the peripheral base station monitoring is started, and the mobile station further predicts the time after which the communication quality deterioration continues from the measurement result of the communication quality, While setting the time to continue station monitoring, while the mobile station monitors peripheral base stations, communication with the wireless base station is stopped, peripheral base station monitoring is performed, and the mobile station sets it first. It is a peripheral base station monitoring method of stopping the peripheral base station monitoring and restarting communication with the wireless base station after a lapse of time for continuing monitoring of the peripheral base stations.

A second aspect of the present invention is a peripheral base station monitoring method, wherein a mobile station starts communication with a radio base station in a radio zone in which the mobile station is located, and then monitors the signal sent from the peripheral base station by the mobile station. If the mobile station measures the communication quality with the wireless base station in communication and determines from the measurement result of the communication quality that the communication quality will be deteriorated thereafter, the peripheral base station monitoring is started. Then, while the mobile station monitors the peripheral base stations, it stops the communication with the radio base station and monitors the peripheral base stations, and after the mobile station continues to monitor the peripheral base stations for a certain period of time, It is a peripheral base station monitoring method of stopping the peripheral base station monitoring and restarting communication with the wireless base station.

[0012]

In general, it is known that the fading reception wave envelope fluctuation in mobile communication follows the Rayleigh distribution law. This makes it possible to theoretically calculate the average value of the duration (fade duration) in which the received wave continuously falls below a certain level, and the calculation results are publicly available in the literature (eg, Okumura, Shinji). , "Basics of Mobile Communications", IEICE).

In the present invention, as an example, it is expected in advance that the received wave falls below a certain level and does not become a significant signal even if it is received by utilizing the statistical property of such fading received wave envelope fluctuation. In this case, control can be performed to monitor the surrounding base stations. Hereinafter, the operation and the like of the present invention will be described in detail based on Examples.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the structure of an embodiment of the present invention, showing the structure of the functions provided on the mobile station side.

In the figure, numeral 1 is a communication quality measuring means for measuring the signal quality of a mobile station which has received a signal from a radio base station, and 2 is a judgment as to whether or not to start monitoring peripheral base stations. Monitoring start determining means 3, monitoring continuation time setting means 3 for setting the monitoring continuation time of the peripheral base stations, and 4 peripheral base station monitoring means for stopping communication with the radio base station and monitoring the peripheral base stations after the monitoring start is determined. Reference numeral 5 denotes a communication resuming means for stopping the peripheral base station monitoring after the mobile station elapses the peripheral base station monitoring duration and restarting communication with the wireless base station.

FIG. 2 is a flow chart for explaining the control of the embodiment and shows the operation of the mobile station during communication. Numerical symbols with the alphabetic symbol "S" in the drawings represent steps of operation, and are quoted in parentheses in the text to correspond to the description. The operation of the embodiment will be described below with reference to FIGS.

When the mobile station is in communication with the radio base station (S-21), the communication quality measuring means 1 is always available.
The quality of the received signal is measured by (S-22). From this measurement result, the monitoring start determining means 2 determines the start of the peripheral base station monitoring when the deterioration of the communication quality is expected to continue for a certain time thereafter (S-23).

When it is decided to start monitoring, the monitoring duration setting means 3 sets the duration of the peripheral base station monitoring based on the expected duration of communication quality deterioration (S-24), and the receiver synthesizer is set. The transmission frequency is switched to the peripheral base station transmission frequency (S-25), and the peripheral base station monitoring means 4 identifies the transfer destination wireless zone (S-26).

During the peripheral base station monitoring, it is judged whether or not the set peripheral base station monitoring duration time has elapsed (S-27),
After the lapse of the monitoring duration, the communication resuming unit 5 stops the peripheral base station monitoring, switches the receiver synthesizer to the communication frequency again (S-28), and returns to the communication state (S-21).

FIG. 3 is a time chart showing an example of a peripheral base station monitoring method of a mobile station in the case of a time division duplex (TDD) mobile communication system in which transmission / reception is performed at different timings on the same frequency in TDMA. The case where the flow chart described in the above is followed is shown. In the figure, numeral symbols 31 and 33 are reception timings of the mobile station, and 32 and 34 are transmission timings of the mobile station.

As a result of measuring the quality of the signal received at the reception timing 31 by the mobile station, it is expected that the communication quality will continue to deteriorate for a certain period of time thereafter (in the example of the figure, the transmission timing 32 and It is assumed that the quality deterioration of the signal transmitted / received at the reception timing 33 is predicted).

The mobile station sets the peripheral base station monitoring continuation time (the set value in the example of the figure is 3 from immediately after the reception timing 31).
Immediately before 4), the synthesizer for the receiver is immediately switched to shift to the peripheral base station monitoring. When the peripheral base station monitoring continuation time has expired, the communication state returns from the reception timing immediately after (the reception timing 34 in the example in the figure).

According to the present invention, even when the mobile station is communicating as described above, the present invention is not implemented even if the communication is interrupted by predicting deterioration of communication quality in advance. By comparison, peripheral wireless base stations can be monitored without significantly degrading communication quality, and the transfer destination wireless zone can be specified during communication.

The invention of claim 2 does not set the continuation time of the peripheral base station monitoring each time, but sets it to a fixed time, and the rest is the same as the control of the above embodiment.
Hereinafter, a method and the like in the case of actually realizing the respective means and the like constituting the above embodiment will be described.

[1] The communication quality measuring means 1 measures a received signal level, or detects an error if it is a signal with an error detection code. This can be realized by a known technique. [2] Monitoring start determining means 2 and monitoring duration setting means 3
Will be described.

The monitoring start determining means 2 uses the average fade duration as described above. That is, from the measurement result of the communication quality measuring means, if the signal received right now is not a significant signal, it can be expected that the subsequent signal will also contain a code error due to the temporal correlation of the fading received wave envelope variation.

Therefore, even if the method of the present invention is not carried out, the signal quality is deteriorated. Therefore, even if the communication is interrupted and the peripheral base station is monitored, it is judged that the quality is equivalent, and the peripheral base station monitoring is started. To decide. Further, even if the received signal is a significant signal, it is possible to determine the start of peripheral base station monitoring from the level difference from the previously received signal and the level fluctuation tendency.

The monitoring duration setting means 3 uses the average fade duration like the monitoring start determining means 2. That is, the average fade duration, which is the average duration time during which the received wave continuously falls below a certain level, may be set as it is as the monitoring duration time. However, since this value is an average value, it is conceivable to set a time shorter than the average fade duration in order to suppress the quality deterioration due to the implementation of the present invention as much as possible.

[3] The peripheral base station monitoring means 4 measures the reception level of each peripheral base station, if the signal has an error detection code, the error detection rate, or receives the signal currently in communication. By comparing the levels or the error detection rates, the transfer destination wireless zone of the mobile station is specified.

[0030]

As described above, according to the present invention, by measuring the quality of a received signal with which communication is being performed and predicting the quality of the received signal thereafter, the communication quality equivalent to that in the case where the present invention is not implemented is achieved. The mobile station monitors surrounding base stations during communication. As a result, it becomes possible to specify the transfer destination wireless zone with high accuracy during communication, and it is possible to efficiently perform channel switching between wireless zones. Further, the present invention is not limited to the TDMA mobile communication system, but can be applied to other communication systems.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a flow chart showing control of the embodiment.

FIG. 3 is a time chart showing an example of a peripheral base station monitoring method in the case of the TDMA-TDD mobile communication system.

FIG. 4 is a diagram showing a system configuration of a mobile communication system.

FIG. 5 is a diagram illustrating a peripheral base station level measuring method of a conventional TDMA mobile communication system.

FIG. 6 is a diagram illustrating a conventional method for measuring the level of a peripheral base station after deterioration of communication quality.

[Explanation of symbols]

 1 Communication Quality Measuring Means 2 Monitoring Start Determining Means 3 Monitoring Duration Setting Means 4 Peripheral Base Station Monitoring Means 5 Communication Resuming Means 31, 33 Reception Timing 32, 34 Transmission Timing

Claims (2)

[Claims] 1. A peripheral base station monitoring method for monitoring a signal sent from a peripheral base station by a mobile station after the mobile station starts communication with a wireless base station in a radio zone in which the mobile station is located, the mobile station comprising: Measures the communication quality with the wireless base station during communication, and starts monitoring peripheral base stations when it determines from the measurement result of the communication quality that the communication quality deteriorates thereafter. From the measurement result of the communication quality, predict the time after which the communication quality will continue to deteriorate and set the time to continue monitoring the surrounding base stations, while the mobile station monitors the surrounding base stations. The communication with the base station is stopped, the surrounding base station is monitored, and after the time when the mobile station continues to monitor the surrounding base station set previously, the surrounding base station monitoring is stopped and the wireless base station A method for monitoring peripheral base stations, characterized by restarting communication with 2. A peripheral base station monitoring method for monitoring a signal transmitted from a peripheral base station by the mobile station after the mobile station starts communication with a wireless base station in a radio zone in which the mobile station is located. Measure the communication quality with the wireless base station in communication, and if it determines from the measurement result of the communication quality that the communication quality will deteriorate thereafter, it starts monitoring the surrounding base stations, and the mobile station While monitoring peripheral base stations, communication with wireless base stations is stopped, peripheral base station monitoring is performed, and after the mobile station continues monitoring peripheral base stations for a certain period of time, it monitors peripheral base stations. A method for monitoring peripheral base stations, characterized by stopping and restarting communication with the wireless base station.