JPH11103480A - Mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system that can smoothly perform a channel switching. SOLUTION: When a mobile station 40 in communication moves to a range of reception of another base station, a mobile communication system for switching a radio channel and continuing communication are provided with a carrier reception level measurement means 41 for measuring a reception level of a carrier signal from the base station, a carrier reception level accumulation means 32 for receiving data at the reception level and calculating comparison information in the base stations 1 to n, a position information detection part 31 for detecting a moving speed and a moving direction of the mobile station as position information, a mobile station position information accumulation part 11 for accumulating the position information in a radio line control station 20, a base station destination prediction part 12 for predicting a destination of the mobile station 40 on the basis of the comparison information and the position information, a radio channel removal part 21 for grasping a radio channel of the destination base station and a base station radio channel changeover part 13 for switching to a grasped radio channel.

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, and more particularly to a handover (radio channel switching) in a microcell mobile communication system having a minimum radio zone.
It is about.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing radio channel switching (hereinafter referred to as handover) performed when a mobile station moves from one radio zone to another radio zone in a mobile communication system. FIG. 3 is a block diagram of a mobile communication system that performs a conventional handover process. In FIG. 3, reference numeral 100 denotes a radio channel switching device, which is provided in the radio network controller 200. The radio network controller 200 controls a plurality of base stations, checks which base station is closest to the mobile station, and determines a radio channel with which the mobile station communicates. A plurality of wireless base stations 1 to n (hereinafter, referred to as base stations) are connected to the wireless channel switching device 100. Each of the base stations 1 to n includes at least a reception level detection unit 310 that detects a reception level of a carrier signal transmitted from the mobile station 400 and transmits the carrier signal to the wireless channel switching device 100.

The radio channel switching device 100 comprises a mobile station reception information storage unit 110, a base station destination determination unit 120, and a base station radio channel switching unit 130. The mobile station reception information accumulation unit 11 accumulates a report of the monitoring result of the carrier signal transmitted by the reception level detection units 310 of the base stations 1 to n. The base station move destination determining unit 120 determines a base station to which the mobile station moves based on a comparison between the result of monitoring the reception level of the carrier signal from each base station and a predetermined threshold. Also, the channel capturing unit 210 of the radio network controller 200
Causes a free radio channel of the selected destination base station to be captured. When the wireless channel capturing unit 210 captures a vacant wireless channel in the base station within the destination wireless zone, the base station call channel switching unit 130 transmits the wireless channel captured from the wireless channel currently used by the mobile station. Switch the radio channel of the mobile station to the channel.

A conventional handover process in a mobile communication system will be described with reference to FIGS.
In FIG. 2, reference numeral 500 denotes a mobile communication switching center,
It is connected to the base station via a wired line and exchanges lines. 2 and 3, it is assumed that the mobile station 400 is an automobile that is a high-speed mobile unit.

[0005] Each of the base stations 1 to n constantly monitors a radio channel used by a mobile station communicating within its own radio zone. Here, when a certain mobile station 400 moves from the wireless zone 1 to the wireless zone 2 during a call, the wireless zone 1
Then, the reception level of the carrier signal of the mobile station 400 decreases. When the base station detects this, the radio network controller 20
0 is notified of reception level deterioration. The radio network controller 200 issues an instruction to the peripheral base station to monitor the reception level of the carrier signal on the radio channel. The peripheral base station that has received the monitoring instruction transmits a report of the monitoring result of the wireless channel to the radio network controller 200. The mobile station reception information storage unit 110 of the wireless channel switching device 100
The report of the monitoring result from each base station is accumulated. Based on the report, the base station movement destination determining unit 120 determines the base station that has reported the monitoring result having the highest reception level of the wireless channel among the surrounding base stations in the movement destination wireless zone (wireless zone 2) of the mobile station. Determined as a base station, the radio channel acquisition unit 210
Causes the base station to capture a vacant radio channel.
Further, the mobile communication switching center 500 is requested to switch the wired line between the base station and the mobile communication switching center 500.

[0006] The mobile communication switching center 500 first conducts a continuity test using a wired line with the base station. If it is determined that the continuity test is good, mobile switching center 500 issues an instruction to switch from the currently used wireless channel to a new wireless channel to mobile station 400, and upon receiving the instruction, mobile station 40 issues a radio switch. Switch the channel to the frequency band of the new radio channel. The base station radio channel switching unit 130
Thus, the base station in the destination wireless zone performs a wireless continuity test with the mobile station, and if it determines that the continuity test is good, notifies the mobile communication switching center 500 Switches the communication path of the wired line from the line of the base station currently in use to the line of the base station in the new wireless zone, and ends the handover process.

Here, in a macrocell mobile communication system in which a wireless zone has a coverage range of several km to several tens km, such as a car telephone system, for example, a high-speed mobile body such as an automobile passes through the wireless zone. Since a sufficiently long time is required, there is a comparatively long time for performing wireless channel switching when crossing the boundary of the wireless zone, and there is no need to increase the processing speed of the wireless channel switching device.

[0008]

However, in order to increase the channel capacity of a mobile subscriber, a micro-cell mobile communication system in which the radio zone is made smaller and the same frequency band is used as efficiently as possible to improve the frequency use efficiency is proposed. Since the coverage of the wireless zone is several hundred meters, it takes only a few seconds for a high-speed moving object such as a car to pass through the wireless zone, and continuously crosses the boundary of the wireless zone in a short time. Thus, there is no room for switching the communication channel. Therefore, a high-speed processing capability is required for a wireless channel switching device in a microcell mobile communication system.
If the processing capability of the radio channel switching device in the radio network controller is not sufficient for such a call channel switching request, there is a problem that the call is disconnected.

[0009] Therefore, it has been desired to realize a channel switching device capable of performing switching smoothly even in a system such as a microcell mobile communication system in which switching of wireless zones must be performed in a short time.

[0010]

According to the mobile communication system of the present invention, when a communicating mobile station moves from a receiving range of a base station performing wireless communication to a receiving range of another base station,
A radio network controller that controls a plurality of base stations switches communication from a radio channel of a mobile station to a radio channel assigned to another base station from a radio channel assigned to a base station performing radio communication. In a mobile communication system to be continued, in a mobile station, a carrier reception level measuring means for measuring a reception level of a carrier signal transmitted from a base station, and in the base station, a reception level of the carrier signal measured by the carrier reception level measurement means. Carrier reception level storage means for receiving and storing data and calculating a comparison result compared with a predetermined threshold value, and position information detecting means for detecting the moving speed and moving direction of the mobile station during communication as position information. Mobile station position information in which a radio network controller stores position information detected by position information detecting means of a plurality of base stations. And a base station for predicting a base station in a reception range to which a mobile station in communication moves based on the comparison result calculated by the accumulation unit and the position information stored by the mobile station position information storage unit. Move destination predicting means, a radio channel capturing means for capturing an unused radio channel of the moving destination base station predicted by the base station move destination predicting means, and a radio channel of the communicating mobile station,
Base station radio channel switching means for switching from the radio channel used by the mobile station to the radio channel captured by the radio channel capturing means. In the present invention,
In switching the radio channel when the mobile station moves from the reception range of one base station to the reception range of another base station, the carrier reception level measuring means of the mobile station determines the reception level of the carrier signal transmitted from the base station. Measure. The carrier reception level accumulation means of the base station receives and accumulates the data of the reception level of the carrier signal, calculates a comparison result compared with a predetermined threshold value, and guarantees that the mobile station is within the reception range. I do. The position information detecting means detects a moving speed and a moving direction of a mobile station performing wireless communication. The moving speed and moving direction are transmitted to the radio network controller as position information. The mobile station position information storage means of the radio network controller stores the position information of the mobile station. The base station movement destination prediction means predicts a base station in a reception range to which the mobile station in communication moves based on the position information and the comparison result. The wireless channel capturing means captures a vacant wireless channel of the base station in the reception range of the predicted movement destination. The base station wireless channel switching means switches from the wireless channel used by the mobile station to the wireless channel captured by the wireless channel capturing means. By performing the prediction first based on the position information, the handover process can be performed smoothly without increasing the processing capability.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram of the mobile communication system according to the first embodiment of the present invention. In the figure, 4
Reference numeral 0 denotes a mobile station, which has at least a carrier reception level measurement unit 41 that receives a carrier signal transmitted from a transmission unit (not shown) of the base station and measures a reception level. 1 to n are base stations, each base station calculates a moving speed and a moving direction of each mobile station based on a carrier signal transmitted from each mobile station in its own radio zone,
A carrier reception level accumulating section 32 for accumulating the reception level of the carrier signal measured by the position information detecting section 31 and the carrier reception level measuring section 41 for detecting as the position information, comparing with a predetermined threshold value, and outputting the comparison information. At least.

Reference numeral 10 denotes a radio channel switching device, which is installed in the radio network controller 20. The wireless channel switching device 10 includes a mobile station position information storage unit 11, a base station destination prediction unit 12, and a base station wireless channel switching unit 13.

[0013] The mobile station location information accumulating section 11 includes base stations 1 to
A management table is generated and accumulated for the position information of each mobile station transmitted every predetermined period from n. The base station movement destination prediction unit 12 moves each mobile station during a call based on the comparison information transmitted from the carrier reception level storage unit 31 and the position information of the management table stored in the mobile station position information storage unit 11. Predict ahead. Further, the time at which the mobile station reaches the boundary between the wireless zone of the base station with which communication is currently performed and the predicted wireless zone of the destination base station is predicted. In addition, the wireless channel capturing unit 21 is configured to capture a vacant wireless channel of the base station in the predicted destination wireless zone. The base station radio channel switching unit 13 changes the radio channel of each mobile station based on the time predicted by the base station destination prediction unit 12 at the predicted time at which each mobile station reaches the boundary. Switches to an unused channel that has been captured.
The timer 14 gives time data to the base station destination prediction unit 12 and the base station radio channel switching unit 13. Base stations 1 to n of the present embodiment are assumed to be base stations of a microcell mobile communication system having a small coverage range. In the present embodiment, mobile station 40 is assumed to be a high-speed mobile vehicle.

Next, handover processing of the mobile communication system according to the present embodiment will be described focusing on wireless channel switching. Each mobile station transmits a carrier signal in a frequency band of a wireless channel during a call. Base stations 1 to n
The position information detection unit 31 receives the carrier signal transmitted from the mobile station 40 and calculates the position information of the mobile station 40. There are several methods for calculating position information. The base station antenna has a function of measuring the incident angle of radio waves using a directional antenna, and the function of measuring the propagation time of a radio signal transmitted and received between the base station and the mobile station. There is a method of calculating the position of the mobile station from the angle of incidence and the propagation time based on the antenna of the base station by using the measurement function. When two base station antennas are installed on the base station side, there is a method of calculating the position of the mobile station from a distance based on the propagation time based on the two antennas. Further, when a spread spectrum system is used as a wireless signal, a pseudo noise signal (PN code) is wirelessly transmitted between the base station and the mobile station, so that the base station side transmits and receives the PN code transmitted and received between the base station and the mobile station. There is a method of measuring the distance by detecting the phase difference of the distance. In the spread spectrum method, in the spread spectrum demodulation on the receiving side,
Since the multipath by a plurality of propagation paths can be separated and identified, the shortest distance between the base station and the mobile station can be measured from the shortest propagation time based on the phase difference of the PN code.

The base stations 1 to n transmit the position information calculated every predetermined period to the mobile station position information storage unit 11 of the wireless channel switching device 10. The mobile station location information storage unit 11
It creates a management table and stores the location information for each mobile station transmitted from the base stations 1 to n.

The base station destination estimating unit 12 checks the base station in the wireless zone where the mobile station 40 is located based on the comparison information. Also, based on the position information of the management table stored in the mobile station position information storage unit 11 and the time data from the timer 14, the destination wireless zone is predicted, and the wireless zone that each mobile station is passing through and the new location of the destination are determined. Predict the time to cross the boundary with the wireless zone. In addition, the base station movement destination prediction unit 12 causes the wireless channel capturing unit 21 to capture a vacant wireless channel of the base station within the wireless zone of the predicted movement destination.
The base station movement destination prediction unit 12 uses the data of the wireless channel captured by the wireless channel capturing unit 21 and the predicted time data as the base station movement destination determination result, and outputs the base station wireless channel switching unit 13.
Send to The mobile communication switching center 50 switches the wired line.

The base station radio channel switching unit 13 changes the radio channel currently used by the mobile station 40 at the predicted time based on the base station destination judgment result transmitted from the base station destination prediction unit 12. Switch to the captured wireless channel. The handover process ends.

As described above, according to the first embodiment,
By the carrier reception level accumulation unit 32 of the base stations 1 to n,
By comparing the height of the reception level with a predetermined threshold,
The wireless zone in which the mobile station 40 is located is guaranteed, and the position information detecting unit 31 detects the moving speed data and the moving speed data of each mobile station based on the carrier signal transmitted from the mobile station in the wireless zone in which the mobile station 40 is in charge. The mobile station position information storage unit 11 of the wireless switching device 10 creates a management table based on the position information, and the base station destination estimating unit 12 transmits the management information to the management table. , The arrival time of the boundary between the currently active wireless zone and the wireless zone to which the mobile station moves is predicted in advance, and the wireless channel capturing unit 21 informs the wireless channel capturing unit 21 in advance of the vacant wireless channel of the destination base station. When the switching time comes, the base station communication channel switching unit 13 switches from the wireless channel currently used by the mobile station to the wireless channel that has been captured. Therefore, the time spent for the wireless channel switching process is increased, and the burden can be reduced. Therefore, even in a system having one small wireless zone such as a microcell communication system, it is possible to perform frequent wireless channel switching by a high-speed mobile station. The communication quality can be ensured, for example, the call is not disconnected.

Embodiment 2 FIG. In the first embodiment described above, it is assumed that the present invention is used in a microcell mobile communication system having a narrow wireless zone, such as a road-to-vehicle communication system between an automobile running on a highway and a roadside base station. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to a macrocell mobile communication system having a large wireless zone. The same wireless channel switching is performed for each of a plurality of mobile stations.

[0020]

As described above, according to the present invention, the carrier reception level of each base station is switched when the mobile station moves from the reception range of one base station to the reception range of another base station. By comparing the level of the reception level with a predetermined threshold value by the storage means, the wireless zone where the mobile station is present is guaranteed, and the position information detecting means determines the moving speed and speed of the mobile station performing wireless communication. Detect the moving direction, transmit it as position information, store it in mobile station position information storage means,
In the base station destination prediction means, based on the position information,
The mobile station during communication predicts a base station in a reception range to which the mobile station moves, and captures a vacant wireless channel of the base station in the reception range of the movement destination predicted by the wireless channel capturing means in advance. Since the wireless channel switching means switches the wireless channel, rather than determining the destination based on the deterioration of the reception level when moving to the boundary between the base stations, the prediction is made faster in time, and the channel switching is performed. Therefore, even if the processing capability of channel switching is not so high, it can be used in a mobile communication system having a narrow reception range of a base station such as a microcell mobile communication system,
Communication quality such that the call is not disconnected can be ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram of a mobile communication system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating wireless channel switching performed when a mobile station moves from one wireless zone to another wireless zone.

FIG. 3 is a block diagram of a mobile communication system that performs a conventional handover process.

[Explanation of symbols]

 1 to n base station 10 wireless channel switching device 11 mobile station position information storage unit 12 base station destination prediction unit 13 base station wireless channel switching unit 14 timer 20 wireless channel control station 21 wireless channel capturing unit 31 position information detecting unit 32 carrier Receiving level storage unit 40 Mobile station 41 Carrier receiving level measuring unit

Claims (5)

[Claims] When a mobile station in communication moves from a reception range of a base station performing wireless communication to a reception range of another base station, a radio channel control station controlling a plurality of base stations includes: In a mobile communication system for switching a radio channel of the mobile station from a radio channel assigned to the base station performing the radio communication to a radio channel assigned to the another base station and continuing communication, the mobile station A carrier reception level measuring means for measuring a reception level of a carrier signal transmitted from the base station; and in the base station, wirelessly receiving data of the reception level of the carrier signal measured by the carrier reception level measurement means. Carrier reception level accumulation means for calculating comparison information compared with a predetermined threshold value, and a moving speed of the mobile station during communication and Position information detecting means for detecting a moving direction as position information; mobile station position information storing means for storing the position information detected by the position information detecting means of a plurality of base stations in the radio network controller; A base station destination that predicts a base station in a reception range to which a mobile station in communication moves based on the comparison result calculated by a reception level storage unit and the position information stored by the mobile station position information storage unit. Predicting means, a radio channel capturing means for capturing an unused radio channel of the destination base station predicted by the base station destination prediction means, and a radio channel of the communicating mobile station, Base station radio channel switching means for switching from a radio channel used by a station to a radio channel captured by the radio channel capturing means. Mobile communication system. 2. The position information detecting means confirms that a mobile station exists in a radio zone based on a reception level of the carrier signal, and based on a carrier signal transmitted from the communicating mobile station. Detecting a distance and an angle to the mobile station at a fixed period, and calculating a moving speed and a moving direction of the mobile station based on the distance and the angle to the mobile station detected at the fixed period. The mobile communication system according to claim 1. 3. The mobile station location information accumulating means generates a management table in which the location information is stored for each mobile station at the predetermined period, and accumulates the location information. Mobile communication system. 4. The base station movement destination prediction unit predicts a base station in a reception range to which a communicating mobile station moves based on a moving direction of the position information, and bases a base station on the moving speed based on the moving speed. 2. The mobile communication system according to claim 1, wherein a time at which a station reaches a boundary of a reception range is predicted. 5. The base station radio channel switching means, wherein the base station destination predicting means predicts that each mobile station will reach a boundary of a reception range between base stations, and the radio channel of the mobile station The wireless channel switching device according to claim 1, wherein the wireless channel switching unit switches the wireless channel from the wireless channel used by the mobile station to the wireless channel captured by the wireless channel capturing unit.