JPH0470094A - Mobile radio communication system and mobile station device - Google Patents

Abstract

PURPOSE:To reduce a load required for a control at a base station by realizing a mobile station controlling system in which the base station does not operate a decentralized traffic control while monitoring the mobile station, and in which the mobile station selects for itself the base station so that the traffic can not be concentrated. CONSTITUTION:Each base station 11-13 gives the information of the operation rate of its own channel to a mobile station 5 in an area, and the mobile station 5 obtains the information of the control channel frequency of an adjacent base station from the base station during communication at present. The mobile station 5 receives the control channel of the adjacent base station except for the base station during communication at present, based on the information of the control channel frequency of this adjacent base station, and obtains the information of the channel operation rate of the base station, and the information of a reception level from the base station. Then, the mobile station 5 selects the base station whose channel operation rate is less than a prescribed value, and whose reception level is more than the prescribed one, as the base station being the next destination of a channel switchover, communicates this station to the base station during communication, and operates the channel switchover. Thus, the traffic distribution control can be operated without increasing the load required for the control at the base station.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distributed system for reducing traffic concentration in mobile communications.

The present invention measures and broadcasts the channel utilization rate of the base station in cellular one-way mobile communication in which a mobile station communicates with a plurality of zones while switching communication with the base station of the zone, and the mobile station receives this information. This prevents traffic concentration by selecting a base station whose reception level from the base station is above a predetermined value and whose channel utilization rate is below a predetermined value as the switching destination base station.

[Conventional technology]

A method of distributing base station traffic in cellular one-way mobile communications where base stations are placed in multiple zones and when a mobile station moves between base stations, it switches channels to the destination base station. The following are considered as:

First, there is a method of increasing or decreasing the transmission power of a communication channel of a base station.

When the transmission power of a base station is reduced, the communication area of that base station is narrowed, the number of mobile stations that communicate with this base station is reduced, and as a result, the traffic of the base station is reduced. In this case, by reducing the transmission power of the base station, the transmission power of the surrounding base station is increased so that a dead zone does not occur, and the mobile station that was communicating with this base station is made to talk to the surrounding base station. As a result, traffic is distributed to surrounding base stations.

This method has the problem of increasing the burden on the base station that increases or decreases transmission power, its surrounding base stations, and the control base station that supervises these base stations. Furthermore, when increasing the transmission power, there is a problem that control must be performed so as not to cause co-channel interference.

Furthermore, as a method that does not increase or decrease the transmit power of the base station,
A method in which a control base station that controls multiple base stations connects a base station where traffic is not concentrated to a mobile station located in a location where it can communicate with multiple base stations (this is called an overlap zone). There is.

Furthermore, although base station traffic is not distributed, there is a dynamic channel allocation method as a countermeasure against traffic concentration. This method does not fix the channel arrangement of base stations over time, but instead allocates channels as needed by looking at the channel usage status of the entire service area. This method has the advantage of significantly improving frequency usage efficiency when the number of channels allocated to the base station is small. However, it requires an antenna duplexer that can arbitrarily share frequency channels, and requires complex control of the base station to allocate an available channel each time a call occurs.

[Problem to be solved by the invention]

Since all of these methods involve traffic distribution control performed on the base station side, there is a problem in that the burden required for control of the base station increases.

An object of the present invention is to allow a mobile station in an overlap zone to control base station traffic by controlling the mobile station to select a base station to switch channels based on the channel utilization rate and reception level broadcast by each base station. The objective is to provide a mobile communication system that can be distributed.

[Means to solve the problem]

In the present invention, the service area is composed of a plurality of zones,
Base stations are placed corresponding to each zone, and a mobile station communicates with one of these base stations, and when the mobile station moves into the area of an adjacent base station during communication, it selects the base station to communicate with. In a mobile communication system in which communication is continued by switching to an adjacent base station, each of the base stations is equipped with means for reporting the control channel frequency of the adjacent station and the channel utilization rate of the own station, and the mobile station Means for monitoring the broadcasted channel utilization rate and the reception level from each base station, and the monitoring result of this means, when the reception level is equal to or higher than a predetermined value.
According to a second aspect of the present invention, there is provided a mobile station for use in the mobile communication system described above, characterized in that the mobile station is characterized in that the mobile station is equipped with means for selecting a base station whose channel utilization rate is less than or equal to a predetermined value as a switching destination base station. The device receives the control channel of the adjacent base station based on the control channel frequency information of the adjacent base station broadcast from the base station with which it is communicating, and monitors the reception level and the channel utilization rate broadcast from the adjacent base station. means for selecting, as a channel switching destination base station, a base station whose reception level of a control channel is equal to or higher than a predetermined value and whose channel utilization rate is equal to or lower than a predetermined value based on a monitoring result of the means; The present invention is characterized by comprising means for requesting channel switching.

[Effect]

Each base station broadcasts its own channel utilization rate to mobile stations within its area.

The mobile station also obtains information about the control channel frequency of an adjacent base station from the base station with which it is currently communicating.

The mobile station receives the control channel of an adjacent base station other than the base station with which it is currently communicating based on the control channel frequency information of this adjacent base station, and receives the channel utilization information of that base station and the information from that base station. Get reception level information.

Then, the mobile station selects a base station whose channel utilization rate is smaller than a predetermined value and whose reception level is higher than a predetermined value as the next base station to which the channel will be switched, and notifies the base station with which it is communicating to change the channel. Make the switch.

〔Example: The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a system configuration of a mobile communication system according to an embodiment of the present invention.

In FIG. 1, the symbols It, 12.1- indicate each base station, and the symbols 24.2□, 23 indicate the respective base stations 1□ to 1.
The area of the zone corresponding to 3 is shown.

Also, reference numbers 3□ and 32.33 indicate the base station 1. 13 and the mobile station 5, and reference numerals 40, 42, and 43 indicate control channels of the base stations 11 to 13.

The shaded area with numeral 6 indicates the overlap zone,
The mobile station 5 moves in the direction of the arrow in the figure and visits the base stations 1□ to 1.
．． Suppose you are communicating by switching channels.

In the present invention, in such a cellular mobile communication system, each base station 11 to 13 uses the control channel frequency of an adjacent station and the channel utilization rate of its own station as a control channel 4. ~
43, and the mobile station 5 receives the channel utilization rate and each base station 1 reported from each of the base stations 11 to 13.
means for monitoring the reception level from 1 to 13; and means for selecting a base station whose reception level is above a predetermined reception level and below a predetermined channel utilization rate as a switching destination base station based on the monitoring result of the means. It is characterized by the presence of

Next, the operation of this embodiment will be described with reference to a flowchart of channel switching operation shown in FIG.

First, the mobile station 5 starts with the base station 1. During communication, base station 11 communicates with adjacent base station 1. through control channel 4□. ．． 13 control channel 42.4 can be obtained (Sl).

Each base station 1. ~13 measures the channel utilization rate of its own station,
Channel operation rate information is broadcast to mobile stations 5 within the area at a constant transmission power on each control channel 4 (S2).

When the base station 5 enters the overlap zone 6 of the three zones by moving in the direction of the arrow, it approaches the currently communicating base station 1. Since it becomes possible to receive the control channels of base stations other than 12 and 130, the control channels are monitored to obtain channel utilization rate information and reception level information of each base station. In addition, channel utilization rate information and reception level information of the base station 1 in communication are obtained (S3).

The mobile station 5 selects the next channel switching destination base station using one of the following selection methods based on the channel utilization rate and reception level of each base station 11 to 13 (S4).

■ Among the base stations whose reception level is above a certain value, select the base station with the lowest channel utilization rate.

■ Among the base stations whose channel utilization rate is below a certain value, select the base station with the highest reception level.

■ Select arbitrarily from among base stations whose reception level is above a certain value and whose channel utilization rate is below a certain value.

The minimum requirements for these selection criteria are that the reception level from the base station is above a certain value and the channel utilization rate is below a certain value. Since there is no need to take the trouble to select the base station with the maximum reception level and the minimum channel utilization rate, the above selection method is used to reduce the amount of control required for selection.

Case (2) is effective in areas where the overlap zone is large, the reception level from each base station is sufficiently high, and the channel utilization rate is high. The opposite is true for case (2), which is effective in areas where the channel utilization rate is low and the reception level is not very high. Case ♦ is effective in cases between ◯ and ◯.

If the base station 11 in communication is selected, communication continues as is. When using the selection method (2), if there is base station 1 in communication among the selection options, base station 1 in communication remains unchanged. Continue to communicate with.

When the mobile station 5 determines the channel switching destination base station, it notifies the channel switching destination base station to the currently communicating base station 11 using the control channel 4° (S6). The base station 11 contacts the channel switching destination base station and executes channel switching for the mobile station 5 (S7, S8).

FIG. 3 is a block diagram showing the configuration of the mobile station 5 used in this embodiment. Reference numeral 10 indicates a mobile station antenna.

A transmitter/receiver distributor 11 is connected to the mobile station antenna 10, and the transmitter/receiver distributor 11 includes a receiver 12 and a transmitter 1.
3 is connected. The receiver 12 and the transmitter @13 are connected to a control device 14, and a terminal 15 and a channel switching destination selection device 16 are connected to the control device 14.

When a signal enters the mobile station antenna 10, it passes through the receiver 12 and is separated into a communication signal and a control signal by the control device 14. The communication signal is processed by the terminal 15, such as voice conversion. The channel switching destination selection device 16 selects a channel switching destination by determining the reception level of the control channel 4 of the peripheral base station and the channel utilization rate information contained therein. This selection result is transmitted through the control device 14 and transmitter 13 to the base station currently communicating.

FIG. 4 is a configuration diagram of a TDMA frame for explaining this embodiment.

This is an embodiment of the present invention in which a base station 1 and a mobile station 5 are performing TDMA communication.

FIGS. 4(a), (b), and (C) show the base station 1. This shows the structure of the transmission TDMA frame on the ~13 side, and base station 1
1 transmits a frame consisting of a control thrower) C, a communication transmission slot T11, TI2, . . . at a frequency f1. Similarly, the base station 12 transmits frames with control slot C2, communication transmission thrower) T21, Ta2... on frequency f2, and the base station 13 transmits frames with control slot C3, communication transmission thrower) T3□, on frequency f3. A frame of T32... is transmitted.

FIG. 4(d) is a configuration diagram of a TDMA frame on the mobile station side, where Co is an empty slot, TX□ is a reception slot for communication, and T2 is a transmission slot for communication.Since the frequencies of transmission and reception are different, The communication reception slot T, 11 and the communication transmission slot (TX2) have different frequencies.

Now, mobile station 5 is connected to base station 1. When communicating with the mobile station 5, the mobile station 5 receives the communication transmission slot T11 at the communication reception slot T)ll at the frequency f1. In addition, the base station 11 broadcasts information on frequencies f2, f of the control slots of neighboring base stations in the control slot C1, and the mobile station 5 uses the control slot C1
Receive at 6.

Surrounding base stations 1. ．． 13 uses the control slots C2 and C3 to notify the mobile station 5 of channel utilization information with the same transmission output, and the mobile station 5 sequentially changes the receiving frequency of the empty slot C8 to control each base station, 12.13. Thrower) C2-C
Receive 3.

The selection result of the base station to which the channel is to be switched is transmitted from the mobile station 5 via the free slot (C8) and received by the control slot (C+) of the base station 1.

〔Effect of the invention〕

In the communication method of the present invention, in the overlap zone,
Since the traffic is distributed and there is no need to control the increase/decrease in the transmission power of the base station, there is an advantage that the control necessary for increasing/decreasing the transmission power is not necessary.

Furthermore, instead of the base station monitoring mobile stations and controlling traffic distribution, the mobile station selects a base station on its own to avoid concentration of base station traffic, reducing the control burden on the base station. It can be reduced.

Furthermore, as the area of one base station becomes smaller by making the zone smaller, the ratio of the overlap zone to the radio wave propagation area increases. The traffic distribution method of the present invention using an overlap zone capable of communicating with a plurality of base stations has an even greater effect on traffic distribution in mobile communication using a microcell method in which the ratio of overlap zones increases.

Channel switching destination selection device.

Patent applicant: Nippon Telegraph and Telephone Corporation Agent: Patent Attorney Naotaka Ide

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the embodiment. FIG. 3 is a block diagram of an embodiment mobile station. FIG. 4 is a TDMA frame configuration diagram of the embodiment. 1, ~13...Base station, 21~23...Zone, 3
, ~33...Communication channel novel 4. ~43... Control channel node 5... Mobile station, 6... Overlap zone, 10... Mobile station antenna, 11... Transmission/reception distributor, 12... Receiver, 13... Transmitter, 14...
Control device, 15...terminal, 16...cha ryo zu lol hanchu 1's kiritetsu flow ryo 2 times actual view gu j ryo appetizer aE1's f + precept 3 times (a) 4 soil temperature 1 +'s TDMA7 The base station for example? ! Dynamic TDMA frame island 4 Figure

Claims (1)

[Claims] 1. A service area is composed of a plurality of zones, base stations are arranged corresponding to each zone, and a mobile station communicates with one of these base stations, and during communication, the mobile station In a mobile communication system in which, when a station moves into the area of an adjacent base station, it switches the communicating base station to that adjacent base station and continues communication, each base station receives the control channel frequency information of the adjacent station and its own station. The mobile station is equipped with a means for reporting the channel operation rate, and a means for monitoring the channel operation rate reported from each base station and the reception level from each base station, and a means for monitoring the reception level based on the monitoring result of this means. 1. A mobile communication system comprising means for selecting a base station whose channel utilization rate is greater than or equal to a predetermined value and less than or equal to a predetermined value as a switching destination base station. 2. The service area consists of multiple zones, base stations are placed corresponding to each zone, and a mobile station communicates with one of these base stations, and during communication, the mobile station communicates with an adjacent base station. In a mobile station device in mobile communication, which switches the communicating base station to an adjacent base station and continues communication when moving to an area, based on the control channel frequency information of the adjacent base station broadcast from the base station with which it is communicating. means for receiving the control channel of the adjacent base station and monitoring the reception level thereof and the channel utilization rate reported from the adjacent base station; A mobile station device for mobile communications, comprising means for selecting a base station whose channel utilization rate is less than a predetermined value as a channel switching destination base station, and means for requesting channel switching to the selected base station. .