JPH1056667A - Wireless communication system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable high-speed and reliable handover by storing channel information of handover return and storing the radio channel for a certain period of time. When a mobile station switches base stations, the mobile station issues a channel reservation instruction to the base station before switching, and the base station control device reserves the wireless communication channel. When the mobile station issues a communication restart instruction to the reserved base station,
Communication is promptly resumed by the reserved channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system including a mobile station and a plurality of base stations, and more particularly, to a radio system capable of switching between base stations during communication when the mobile station moves. In a communication system, the present invention relates to a handover for switching a base station.

[0002]

2. Description of the Related Art In recent years, with the advancement of advanced information in society in general, mobile communication systems excellent in immediacy and functionality have attracted much attention, and are used in various forms such as mobile phones and car phones. In addition, the effective use of frequency may be attempted, and in the field of mobile communications, the transition from the conventional analog system to the digital system is progressing in order to economically realize high quality and various information communications. It is the current situation.

[0003] In Japan, PHS (Personal Handyphone) is used as a digital mobile communication service.
System) has been started. On the other hand, in the United States, PACS (Personal Ac)
cess Communications System
m) is a PCS (Personal)
Communication Services). In PACS, TDMA (Time Division) is used as a radio access method.
Multiple Access (FD) (Frequency Division) is used as a transmission method.
Duplexing) method is DQS as a modulation method.
The PSK method is adopted. In PHS, TD
MA-TDD (Time Division Dupl)
exing) method is employed.

In PACS, like PHS in Japan,
A service area is composed of a number of wireless zones.
For this reason, when a mobile station moves geographically while continuing communication with one base station and approaches a wireless zone of another base station, or when radio deterioration occurs due to the occurrence of an obstacle, the mobile station moves. The station needs a handover function to switch the radio link from the original base station to the new base station and continue communication. With this handover function, the user can move within the area of the wireless zone without disconnecting the communication.

[0005] An example of a wireless communication system having a handover function is disclosed in, for example, Japanese Patent Laid-Open No. 5-130021. The mobile station or the base station detects the radio quality deterioration, the mobile station selects the destination base station, sets a new communication channel with the destination base station, and establishes a link between the base station and the communication network. Is switched to the line with the new base station, and the channel with the base station before the movement is released, thereby switching the wireless channel.

FIG. 11 is a configuration diagram of such a conventional wireless communication system. In FIG. 11, a wireless communication system includes a base station controller 102 connected to a communication network 101.
And a plurality of base stations connected to and managed by the base station controller 102 (here, the base stations 103 and 104 are representative).
Only shown) and the wireless zone 10 managed by those base stations.
5 and 106, and a mobile station 111 located in one of the wireless zones. As the communication network 101, a telephone network, an ISDN (Integrated Services Digital Network), a wireless line, or another communication line is used. The wireless zones 105 and 106 correspond to the wireless zones managed by the base stations 103 and 104, respectively.
Reference numeral 11 is wirelessly connected to the base station 103. In addition,
In the present embodiment, it is assumed that digital communication using TDMA is employed for communication between the base stations 103 and 104 and the mobile station 111 in the wireless zone 105 or 106.

FIG. 12 is a block diagram showing a configuration related to a handover of a mobile station apparatus and a base station controller in a conventional radio communication system having a handover function. The mobile station device 111 includes a wireless state measuring unit 61 that measures a communication state with each base station, a base station switching determining unit 62 that determines switching of a base station based on information stored in a wireless state table, The wireless communication apparatus includes a base station switching unit 63 that switches the base station based on the determination of the station switching determination unit 62, and a wireless state table 64 that stores the measurement results of the wireless state measuring unit 61. In addition, the base station control device 102 includes a switching unit 65 that controls switching of base stations.

[0008] In the conventional radio communication system configured as described above, the operation in the case where the base station is switched with the movement of the mobile station device will be described. Here, a case will be described in which the mobile station 111 switches from the base station 103 to the base station 104 as the mobile station 111 moves, that is, a handover process is performed.

The radio condition measuring section 61 is a base station to be measured (including the base station 103 currently used for communication).
Is measured, and the measurement result is stored in the wireless state table 64. The radio state table 64 stores base station information and information such as the measured received electric field strength as a set. The base station switching determination unit 62 determines the wireless state of the base station 103 that is currently communicating based on the information stored in the wireless state table 64. If the received electric field strength of the base station 103 is higher than the threshold value, it is determined that wireless deterioration has not occurred, and the base station 103 continues communication.

If the received electric field strength is equal to or less than the threshold value, it is determined that radio deterioration has occurred and the base station is to be switched, and
The base station having the highest received electric field strength (here, the base station 104) is selected as the destination base station, and the base station switching unit 63 is requested to switch the base station. The base station switching unit 63 detects an empty slot of the destination base station 104,
The detected empty slot is captured, and when the capturing of the empty slot is successful, a base station switching request to the destination base station 104 is transmitted using the captured slot, and the switching unit 65 of the base station control apparatus 102 transmits the destination Upon receiving the communication start notification from the base station 104, the destination base station 10
By transmitting a base station switching completion instruction to the base station 104, the switching to the destination base station 104 is completed. Further, when the acquisition of the empty slot fails, the communication is resumed using the pre-move base station 103 by transmitting a communication restart instruction to the pre-move base station 103 assuming that the switching has failed. That is, communication with the pre-movement base station 103 can be resumed until the handover is completed.

On the other hand, in the base station control apparatus, upon receiving the base station switching request transmitted by mobile station 111, switching section 65 transmits base station 103 to base station 104 as a base station used for communication with mobile station 111. Is performed, a communication start notification is transmitted to the mobile station 111, and the mobile station 1
Communication with the H.11 starts.

[0012] The handover process is performed as described above, and the mobile station can switch to a new base station or resume communication with the previous base station to continue communication.

[0013]

In the conventional wireless channel switching method in a wireless communication system, if a handover process is being performed, a wireless channel is secured at the base station before moving, and an empty channel at the moving destination can be captured. It can be used when there is no access, but in the communication after the completion of handover, if it is desirable to shift the base station, for example, if radio deterioration is detected again, the free slot of a new base station should be captured each time. To perform a handover to the captured slot. Therefore, a lot of time is required for the handover process, and a call disconnection during communication accompanying the process frequently occurs. In particular, when reciprocating between base stations determined in a narrow area is repeated, movement to the same base station is repeated many times, and the same processing is repeated each time, resulting in waste. In addition, there is a frequent danger that handover cannot be performed due to a failure in capturing an empty slot, for example, when there is no empty slot in the destination base station.

[0014] The present invention has been made in view of the above-mentioned problems, and holds a radio channel between a mobile station and a base station before a handover for a certain period of time, thereby ensuring a handover in a short time. It is an object to provide a communication system.

[0015]

According to a first aspect of the present invention, there is provided a mobile station, a plurality of base stations, and a base station controller for managing the plurality of base stations. Wireless communication between a base station and a mobile station located in a wireless zone managed by the base station, wherein the mobile station can switch the base station to be wirelessly connected during communication. In the system, the mobile station determines, during communication, whether or not to switch a base station to be wirelessly connected to the mobile station, and if it is determined to perform the switch, the mobile station is wirelessly connected before switching. A base station switching determining unit for instructing the base station to reserve a wireless channel used for the wireless connection without using the wireless channel for another wireless connection; Reserve instruction, reserves a wireless channel without using it for wireless connection with others, refers to a reserved base station information table that stores information about reserved base stations, and refers to information in the reserved base station information table. By the determination of the base station switching determination unit, the base station to be switched, the destination base station determination unit to determine whether or not the reserved base station, information of the reserved base station, By acquiring from the reserved base station information table and instructing the base station to resume communication, the reservation of the wireless channel held by the base station is released, and communication by wireless connection in the wireless channel is performed. A reserve base station resuming unit for resuming communication, and when reserving is instructed, or when resuming communication and resuming communication, A wireless communication system, characterized in that those comprising a reserve base station information updating unit for updating the Chikyoku information table.

According to a second aspect of the present invention, there is provided a mobile station, a plurality of base stations, and a base station control device for managing the plurality of base stations, and the base station and a radio station managed by the base station. In a wireless communication system capable of wirelessly connecting to a mobile station located in a zone, wherein the mobile station can switch the base station to be wirelessly connected during communication, the base station control device includes a mobile station. And a base station to suspend communication by wireless connection, and reserve the wireless channel used for the wireless connection without using it for wireless connection with the other. A mobile station that releases its reserved state, and that has been suspended, and a reserve restart unit that restarts the communication by wireless connection with the base station via the wireless channel. A wireless communication system to symptoms.

The invention according to claim 3 is based on claim 2.
In the wireless communication system described above, the base station control device measures the time in a reserved state with respect to the wireless channel reserved by the reserve start means, and in the time measurement, a predetermined period of time. When a time-out signal elapses, a reserve timer that outputs a time-out signal, and when a time-out signal is output from the reserve timer, a reserve state in a reserved wireless channel that is being measured by the reserve timer And a reserve end unit with a timer that enables the wireless channel to be used by another wireless connection with the wireless channel. The reserve start unit interrupts communication by wireless connection between the mobile station and the base station. Therefore, the wireless channel used for the wireless connection must not be used for the wireless connection with others. When making a reserve, the reserve timer is a reserve start unit with a timer for instructing the reserve timer to start measuring the time during which the wireless channel is in a reserved state, and the reserve restart unit is configured to reserve the wireless channel for the reserved wireless channel. In order to release the reserved state and restart the communication by the wireless connection between the suspended mobile station and the base station on the wireless channel,
A wireless communication system, characterized in that it is a reserve restart unit with a timer for instructing the reserve timer to stop measuring the time.

The invention according to claim 4 comprises a mobile station, a plurality of base stations, and a base station control device for managing the plurality of base stations, and the base station and a radio station managed by the base station. In a wireless communication system in which a mobile station located in the zone can be wirelessly connected, and the mobile station can switch the base station to be wirelessly connected during communication, the mobile station, during communication, Determine whether to switch the base station wirelessly connected to the mobile station,
If it is determined that switching is to be performed, an instruction is given to the base station that is wirelessly connected before the switching to reserve the wireless channel used for the wireless connection without using the wireless channel for other wireless connections. By issuing a reserve instruction from the base station switching determining unit and the base station switching determining unit,
Reserve the wireless channel without using it for wireless connection with others, reserve base station information table storing information about the reserved base station, and refer to the information of the reserved base station information table, the base station By the determination of the switching determination unit, the base station to be switched, the destination base station determination unit to determine whether or not the reserved base station, information of the reserved base station,
Obtained from the reserved base station information table, by instructing the base station to resume communication, cancel the reservation of the wireless channel held by the base station,
A reserve base station resuming unit for resuming communication by wireless connection in the wireless channel, and a reserve base station information updating unit for updating the reserve base station information table when a reservation is instructed, or when reserving and resuming communication. Wherein the base station controller suspends communication by wireless connection between the mobile station and the base station, and reserves the wireless channel used for the wireless connection without using the wireless channel for other wireless connections. A reserve start unit that releases the reserved state for the reserved wireless channel, and resumes the communication by the wireless connection between the interrupted mobile station and the base station via the wireless channel. A wireless communication system characterized in that:

The invention according to claim 5 is the invention according to claim 4.
In the wireless communication system described above, the base station control device measures the time in a reserved state with respect to the wireless channel reserved by the reserve start means, and in the time measurement, a predetermined period of time. When a time-out signal elapses, a reserve timer that outputs a time-out signal, and when a time-out signal is output from the reserve timer, a reserve state in a reserved wireless channel that is being measured by the reserve timer And a reserve end unit with a timer that enables the wireless channel to be used by another wireless connection with the wireless channel. The reserve start unit interrupts communication by wireless connection between the mobile station and the base station. Therefore, the wireless channel used for the wireless connection must not be used for the wireless connection with others. When making a reserve, the reserve timer is a reserve start unit with a timer for instructing the reserve timer to start measuring the time during which the wireless channel is in a reserved state, and the reserve restart unit is configured to reserve the wireless channel for the reserved wireless channel. In order to release the reserved state and restart the communication by the wireless connection between the suspended mobile station and the base station on the wireless channel,
A wireless communication system, characterized in that it is a reserve restart unit with a timer for instructing the reserve timer to stop measuring the time.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a configuration diagram of a wireless communication system according to Embodiment 1 of the present invention. In FIG. 1, 1 is a communication network, 2 is a base station controller, 3 and 4 are base stations, 5 and 6
Is a wireless zone, and 11 is a mobile station. The wireless communication system according to the first embodiment includes a base station controller 2 connected to the communication network 1 and a plurality of base stations connected to and managed by the base station controller 2 (here, the base station 3 4 only), and the wireless zones 5 and 6 managed by those base stations.
Mobile station 11 located in any of the wireless zones
It is composed of The communication network 1 includes a telephone network and an ISD
N (Integrated Services Digital Network), wireless lines, or other communication lines are used. The wireless zones 5 and 6 correspond to the wireless zones managed by the base stations 3 and 4, respectively. The mobile station 11 located in the wireless zone 5
It is connected to the base station 3 by radio. In the system of the first embodiment, the base stations 3 and 4 and the wireless zone 5
It is assumed that digital communication using TDMA is employed for communication between the mobile stations 11 in the first and sixth mobile stations.

FIG. 2 is a block diagram showing the configuration of the base station controller 2 and the base station 3 (the same applies to the base station 4) in FIG. As shown in FIG. 2, the base station control device 2 includes a base station connection unit 26, a communication control unit 27, an input unit 28, an output unit 29, and a line control unit 30. The base station connecting unit 26 is connected to the base station 3 and the communication control unit 27, transmits data received from the communication control unit 27 to the base station 3, and notifies the communication control unit 27 of the data received from the base station 3. I do. The communication control unit 27 includes a CPU, a ROM, and a RAM.
And the like, and controls the communication state between the base station and the base station controller. The input unit 28 includes a keyboard, a microphone, and the like, and inputs data and voice to the communication control unit 27. The output unit 29 is configured by a magnetic disk device, a display device, a speaker, and the like, and stores, displays, outputs sound, and the like, the data output from the communication control unit 27.
The line control unit 30 is connected to the communication network 1 and the communication control unit 27, and controls connection states and switching of lines.

The base station 3 includes a transmitting / receiving antenna 21, a radio controller 22, a modulator 24, and a demodulator 25.
And a base station controller connection unit 23. The radio control unit 22 has a function of transmitting the modulated data given from the modulation unit 24 on the radio carrier and transmitting the modulated data from the antenna 21;
A function of receiving a signal in a predetermined frequency band from high-frequency signals induced in the antenna 21; The modulation unit 24
The transmission data output from the base station control device connection unit 23 is modulated (for example, quadrature phase modulation) by a predetermined method and output to the radio control unit 22. The demodulation unit 25 includes the wireless control unit 2
And demodulates the signal received by the base station controller 2 and supplies the demodulated signal to the base station controller connection unit 23. The base station control device connection unit 23 notifies the data received from the base station control device 2 to the modulation unit 24 or the radio control unit 22, and transmits the data received from the demodulation unit 25 to the base station control device 2. Note that the wireless control unit 22 switches between the transmission mode and the reception mode in response to a transmission / reception switching instruction given from the communication control device 27 via the base station connection unit 26 and the base station control device connection unit 23.

FIG. 3 is a block diagram showing the configuration of the mobile station 11 in FIG. 1 in more detail. As shown in FIG. 3, the mobile station 11 includes an antenna 31 and a radio control unit 32.
, A communication control unit 33, a modulation unit 34, a demodulation unit 35,
It comprises an input unit 36 and an output unit 37. The wireless control unit 32 has a function of transmitting modulated data provided from the modulation unit 34 on a wireless carrier wave and transmitting the modulated data from the antenna 31 and a function of receiving a signal in a predetermined frequency band from high-frequency signals induced in the antenna 31. Have. The communication control unit 33 includes:
It includes a CPU, ROM, RAM, etc., and controls the communication state of the mobile station. The modulation unit 34 modulates (for example, quadrature phase modulation) transmission data output from the communication control unit 33 by a predetermined method, and outputs the data to the wireless control unit 32. The demodulation unit 35
The signal received by the wireless control unit 32 is demodulated and provided to the communication control unit 33. The input unit 36 includes a keyboard, a microphone, and the like, and inputs data and voice to the communication control unit 33. The output unit 37 is configured by a magnetic disk device, a display device, a speaker, and the like, and stores, outputs, outputs sound, and the like, the data output from the communication control unit 33. The wireless control unit 32 switches the communication channel in response to a channel switching instruction given from the communication control unit 33.
3 is switched between the transmission mode and the reception mode in response to the transmission / reception switching instruction given from the communication device 3.

FIG. 4 is a diagram showing an example of the structure of data transmitted and received between the mobile station and the base station used in the radio communication system according to the first embodiment. (A) is a figure which shows the data format about one time slot on the downlink radio link in a PACS system. In the PACS system, one TDMA frame is 2.5 msec, and the communication is performed in the downlink direction (from the base station to the mobile station) using one 312.5 μsec time slot obtained by equally dividing the TDMA frame into eight. . As shown in the figure, one time slot includes a 14-bit synchronization channel (SYC),
It is assigned to a slow channel of 10 bits (SC), a fast channel (FC) of 80 bits, an error correction code (CRC) of 15 bits, and a power control channel (PCC) of 1 bit. . Information to be transmitted to the mobile station is transmitted using FC, and a use state such as a slot being used or not being used is notified using SC.

FIG. 2B is a diagram showing a data format for one time slot on an uplink radio link in the PACS system. In the PACS system, one TDMA frame is 2.5 msec, which is further divided into eight equal parts, and an interval (Guard Time) for protecting data transmitted by each mobile station from being destroyed by each other.
e) Uplink communication (mobile station → base station communication direction) is performed using one 281 μsec time slot excluding 12 bits. As shown in the figure, one time slot has two bits of Differential E.
ncoding Reference Symbol
(DE), 10-bit slow channel and (S
C), 80-bit fast channel (FC) and 1
An error correction code (CRC) for 5 bits and a reserve for 1 bit are allocated. Information to be transmitted to the base station is transmitted using FC, and a use state such as using or not using a slot is notified using SC.

(C) and (d) are diagrams showing the data format of the FC shown in (a) and (b), where (c) shows the case where all information to be transmitted is stored in one time slot. , (D) has a configuration in which all information to be transmitted is stored over two time slots. In the case shown in (c), the FC of 80 bits is composed of a header part, a data storage part, and a data check part.
In the case of (d), the preceding FC allocation slot is composed of a header section and a data storage section, and the next allocation slot is a header section indicating that data is continuing and a data storage section. And a data check unit. Even when the information to be transmitted extends over three or more time slots, the middle time slot similarly has a header indicating that data continues, and the last time slot includes a data check unit.

The operation at the time of communication in the wireless communication system according to the first embodiment configured as shown in FIGS. 1 to 3 will be described below. In the downlink direction, that is, in the communication from the base station to the mobile station, the communication is performed as follows. The transmission data transmitted from the communication network 1 to the mobile station 11 passes through the line control unit 30 and is controlled by the communication control unit 27 from the base station connection unit 26 to the base station control device connection unit 2 of the base station 3.
3 and is modulated by the modulation unit 24 in a predetermined manner, and passed to the wireless control unit 22. At this time, the radio control unit 22 includes the base station connection unit 26 and the base station control device connection unit 23
The transmission mode is set by the transmission / reception switching instruction given from the communication control device 27 through the
The modulated data passed from the antenna 21 is transmitted on the wireless carrier from the antenna 21. The format at this time is as shown in FIG. 4A, and the data therein is transmitted in the format of (c) or (d).

The high-frequency signal composed of the radio carrier and the modulation data is transmitted to the antenna 31 of the mobile station 11, and is transmitted to the radio control unit 32 in the reception mode according to the transmission / reception switching instruction given from the communication control unit 33. A signal of a predetermined frequency band is received from the inside, and the signal is demodulated from the modulated data in the demodulation unit 35, transmitted to the communication control unit 33, and output by the output unit 37.

The communication in the uplink direction, ie, from the mobile station to the base station, is performed as follows. In the mobile station 11, data input from the input unit 36 is transmitted from the communication control unit 33 to the modulation unit 34, modulated in a predetermined format, and transmitted to the wireless control unit 32. Communication control unit 33
The radio control unit 32 in the reception mode in response to the transmission / reception switching instruction given from the antenna transmits the modulated data passed from the modulation unit 34 on the radio carrier wave from the antenna 31. The format at this time is as shown in FIG.
The data therein has the format of (c) or (d).

In the base station 3, the high frequency signal transmitted to the antenna 21 and composed of the radio carrier and the modulation data is:
In accordance with a transmission / reception switching instruction given from the communication control device 27 via the base station connection unit 26 and the base station control device connection unit 23, the radio control unit 22 in the reception mode outputs a predetermined frequency band from the high frequency signal. Is demodulated from the modulated data by the demodulation unit 25 and transmitted from the base station control unit connection unit 23 to the base station connection unit 26 of the base station control unit 2. Then, in the base station control device 2, under the control of the communication control unit 27,
It is sent from the line control unit 30 to the communication network 1.

The wireless communication system operating as described above can communicate with a communication system connected via the communication network 1.

Embodiment 1 A wireless communication system according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram illustrating a configuration related to a handover process between the mobile station device and the base station control device in the wireless communication system according to the first embodiment. The mobile station apparatus 11 includes a wireless state measuring unit 41, a base station switching determining unit 42, a destination base station determining unit 43, a base station switching unit 44, a reserved base station restarting unit 45, and updating of reserved base station information. Part 46,
It has a radio status table 47 and a reserved base station information table 48. The wireless state measuring unit 41 measures the reception electric field strength of each base station (including the base station 3 currently used for communication) to be measured, and stores the measurement result in the wireless state table 47. Base station switching determination unit 42
Determines the wireless state of the currently communicating base station 3 based on the information stored in the wireless state table 47, and sends a reserve instruction to the base station before moving if it determines to switch. The destination base station determination unit 43 determines whether the destination base station selected by the base station switching determination unit 42 is a reserved base station based on the information stored in the reserved base station information table 48. I do. The base station switching unit 44 performs a reserve instruction to the pre-movement base station, detects an empty slot in the destination base station, and performs base station switching.
The reserve resuming unit 45 stores the reserved base station information table 4
8, the information of the destination base station is obtained, a communication restart instruction is issued to the destination base station based on the obtained information, and the communication is restarted. The reserved base station information updating unit 46 updates the reserved base station information table 48 at the time of base station switching or reservation cancellation. The wireless state table 47 stores a set of information such as base station information and the received electric field strength measured by the wireless state measuring unit 41. The reserved base station information table 48 stores information on base stations that are currently reserved.

The base station control device 2 includes a reserve start unit 51
, A switching unit 52, a reserve restart unit 53, and a reserve end unit 54. The reserve start unit 51
When receiving the channel reservation instruction transmitted by the mobile station 11, the connection of the wireless channel used for communication with the mobile station 11 is maintained without being released. Upon receiving the base station switching request transmitted by the mobile station 11, the switching unit 52 switches to a base station used for communication with the mobile station 11 and transmits a communication start notification to the mobile station 11. Reserve restart section 53
Receives the communication restart instruction transmitted by the mobile station 11,
The reservation of the wireless channel is released, and the communication with the mobile station 11 is restarted. Upon receiving the channel reservation release instruction transmitted by the mobile station 11, the reserve ending unit 54 releases the reserved wireless channel.

FIG. 6 is a sequence diagram showing a handover process in which the mobile station switches base stations during communication, and FIG. 7 is a sequence diagram showing a process when a reservation release request is generated on the mobile station side. .

In the wireless communication system according to the first embodiment configured as described above, (A) handover (switching)
And (B) the operation at the time of reservation release will be described with reference to FIGS. 1 and 5 to 7.

(A) Handover In the communication system according to the first embodiment, the operation when the mobile station 11 communicating with the base station 3 switches the communication to the base station 4 using the base station 3 as a reserved base station. 6 will be described with reference to FIG. 1 and FIG. In the following description, when the mobile station 11 switches to the base station 4 while communicating with the base station 3, the base station 3 and the base station 4 are controlled by the base station controller 2, and the base station 4
Has shown the case where the wireless channel is being reserved as a reserved base station, but the same operation as described below is performed when the base station is switched to another mobile station or another base station. Further, the base station 3 communicates with the communication channel CH1.
It is assumed that the base station 4 is assigned the communication channel CH2.

First, the radio condition measuring section 41 of the mobile station 11
Measures the received electric field strength of each base station (including the base station 3 currently used for communication) to be measured, and stores the measurement result in the wireless state table 47. The wireless state table 47 stores a set of information such as base station information and the received electric field strength measured by the wireless state measuring unit 41.

The base station switching determination section 42 refers to the radio state table 47 to determine the communication state with the base station. First, for the base station 3 currently communicating, the received electric field strength is compared with a preset threshold value. If the received electric field strength is higher than the threshold value, it is determined that radio deterioration has not occurred, and communication with the base station 3 is performed. continue.

If the received electric field strength is equal to or less than the threshold value, it is determined that radio deterioration has occurred, and the channel having the strongest received electric field strength is selected with reference to the radio state table 47, and firstly, the channel having the current communication strength is selected. It is determined whether the channel is a medium channel (the communication channel CH1 assigned to the base station 3). C
If H1 is the strongest channel, communication with the base station 3 is continued. When the communication channel CH2 assigned to the base station 4 is the strongest channel, the base station switching determination unit 42 determines the base station 4 as a destination base station, and determines whether the base station 4 is currently communicating with the base station (hereinafter, “before moving”). A channel reserve instruction is transmitted to the base station 3 (referred to as a base station).
When the reserve start unit 51 of the base station control device 2 receives this reserve instruction, the communication between the base station 3 and the mobile station 11 is interrupted, and the connection of the used wireless channel CH1 is maintained without being released.

Next, the destination base station determination unit 4 of the mobile station 11
3 is a case where the base station 4 selected as the destination base station is determined to be in the information of the reserved base station information table 48 in which information of the currently reserved base station is stored, and the base station 4 is being reserved. , Reserved base station restart section 45
If the reservation is not being made, the base station switching unit 44 is requested to switch the base station. In this case, the destination base station determining unit 43 detects that the base station 4 is being reserved, and requests the reserved base station resuming unit 45 to switch the base station.

Next, the mobile station 11 shifts to the communication channel CH2 assigned to the base station 4, and the reserved base station resuming unit 45 uses the communication channel CH2 to
Is transmitted. Then, the reserved base station information updating unit 46 deletes the base station information of the movement destination base station 4 from the reserved base station information table 48, and replaces the base station information of the base station 3 before movement with the reserved base station information table 48.
To be stored. Reserve resuming unit 53 of base station controller 2
Receives the communication restart instruction transmitted by the mobile station 11,
The reservation of the wireless channel CH2 is released, and the communication between the base station 4 and the mobile station 11 is restarted. Thus, the switching to the base station 4 is completed.

If the base station 4 is not in reserve at the stage of the determination by the destination base station determining section 43, the following is performed.

In the mobile station 11, the destination base station determining unit 43 requests the base station switching unit 44 to switch, and the base station switching unit 44 detects and captures an empty slot of the destination base station 4. When the acquisition of the empty slot is successful, the target base station 4 is used by using the acquired slot.
Is transmitted to the switching unit 52 of the base station control device 2 and the switching process is performed by the switching unit 52. When the base station switching unit 44 receives the communication start notification, the base station from the base station switching unit 44 By transmitting the switching completion instruction, the switching to the destination base station 4 is completed. Further, when the acquisition of the empty slot fails, a request for resuming communication with the base station 3 is issued to the reserve base station resuming unit 45 assuming that the switching has failed, and the reservation is being performed as described above. By the same operation as the case of resuming communication with the base station 4, communication using the pre-movement base station 3 is continued again.

(B) Release of Reserve As a result of (A), from the stage where the base station 3 sets the communication channel CH1 with the mobile station 11 currently communicating with the base station 4 to the reserved state, the mobile station 11 side releases the reserve. The operation of the wireless communication system according to the first embodiment when a request is issued will be described with reference to FIGS. 1 and 5 according to the sequence diagram of FIG.

When the mobile station 11 issues a reserve release request to the reserved base station 3, the mobile station 1
The information of the base station 3 stored in the reserved base station information table 48 is acquired by the first reserved base station information updating unit 46, and the channel CH1, which is the channel with the base station 3 whose reservation is to be released, is transferred. When a reserve release instruction to the base station 3 is sent through CH1, and the reserve end unit 54 of the base station control device 2 receives this,
The reserved channel CH1 is released.

Next, in the mobile station 11, the information of the base station 3 is deleted from the reserved base station information table 48 by the reserved base station information updating section 46, and the mobile station 11 returns to C
By shifting to H2, communication with the base station 4 is continued. This is the end of the reservation release process.

In the radio communication system according to the first embodiment, when base station switching due to deterioration of the radio condition is determined by the base station switching determining unit of the mobile station, the base station switching determining unit determines the base station before switching. When the reservation start unit of the base station control device receives this instruction, the mobile station and the base station before the switching use release the radio channel used for communication to another mobile station. Therefore, it is kept in a reserved state without any trouble. If the mobile station needs to resume communication with the reserved base station, the reserve base station resuming unit of the mobile station issues a communication resuming instruction, and the reserve resuming unit of the base station controller receives the instruction. Then, by releasing the reserved state of the communication channel from the reserved state and restarting the communication, it is possible to restart the communication without delay. For this reason, even when the mobile station is moving near the boundary of the wireless zone of a plurality of base stations, or when the wireless state is frequently degraded due to obstacles or the like, the mobile station can be moved even when handover processing is frequently used. The station can surely secure a wireless channel, and furthermore, high-speed handover is possible because processing such as acquisition of an empty slot is not required.

Embodiment 2 FIG. A wireless communication system according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 8 is a block diagram illustrating the configurations of the mobile station device and the base station control device in the wireless communication system according to the second embodiment. The configuration of the mobile station device 11 is the same as that of the mobile station 11 in FIG.

The base station controller 2 includes a reserve start unit with timer 51a, a switching unit 52, a reserve restart unit with timer 53a, a reserve end unit with timer 54a, and a reserve timer 55. When receiving the channel reserve instruction transmitted by the mobile station 11, the reservation start unit with timer 51a activates the reserve timer 55 while maintaining the connection of the wireless channel used for communication with the mobile station 11 without releasing it. . The switching unit 52 receives the base station switching request transmitted by the mobile station 11,
Switching as a base station used for communication with the mobile station 11,
A communication start notification is transmitted to the mobile station 11. When receiving the communication restart instruction transmitted by the mobile station 11, the reservation restart unit with timer 53a cancels the reservation of the wireless channel,
At the same time as the communication with the mobile station 11 is resumed, the reserve timer 55 is stopped. Reserve end unit 54a with timer
Receives the channel reservation release instruction transmitted by the mobile station 11, releases the reserved radio channel and stops the reserve timer 55 at the same time. When the reserve timer 55 outputs a time-out signal, the reserved end unit with timer 54a releases the wireless channel being reserved. The reserve timer 55 is a timer used to hold a radio channel with the mobile station 11 and measure a reserve time for each base station, which is a time for disabling use of another mobile station, for each base station. In measuring the time, when a predetermined time has elapsed, a time-out signal is sent to a reserve end unit 54 with a timer.
a.

FIG. 9 is a sequence diagram showing processing when the mobile station switches base stations during communication, and FIG. 10 is a sequence diagram showing processing when a reservation release request is generated on the mobile station side.

In the wireless communication system according to the second embodiment configured as described above, the operations at the time of (A) handover and (B) release of reserve are shown in FIG. 1 and FIGS.
Explanation will be made using 0.

(A) Handover In the communication system according to the second embodiment, the operation when the mobile station 11 communicating with the base station 3 switches the communication to the base station 4 using the base station 3 as a reserved base station. 9 and FIG. 9 will be described with reference to FIGS.
In the following description, when the mobile station 11 switches to the base station 4 while communicating with the base station 3, the base station 3 and the base station 4 are controlled by the base station controller 2, and the base station 4 is reserved. Although the case where the radio channel is reserved as the base station has been described, the same operation as described below is performed when the base station is switched to another mobile station or another base station. Further, the base station 3 sets the communication channel CH1 to:
It is assumed that the base station 4 is assigned the communication channel CH2.

First, the radio condition measuring section 41 of the mobile station 11
Measures the received electric field strength of each base station (including the base station 3 currently used for communication) to be measured, and stores the measurement result in the wireless state table 47. The wireless state table 47 stores a set of information such as base station information and the received electric field strength measured by the wireless state measuring unit 41.

The base station switching determination section 42 refers to the radio state table 47 to determine the communication state with the base station. First, for the base station 3 currently communicating, the received electric field strength is compared with a preset threshold value. If the received electric field strength is higher than the threshold value, it is determined that radio deterioration has not occurred, and communication with the base station 3 is performed. continue.

If the received electric field strength is equal to or less than the threshold value, it is determined that radio deterioration has occurred, and the channel having the strongest received electric field strength is selected by referring to the radio state table 47, and firstly, the channel having the current communication strength is selected. It is determined whether the channel is a medium channel (the communication channel CH1 assigned to the base station 3). C
If H1 is the strongest channel, communication with the base station 3 is continued. When the communication channel CH2 assigned to the base station 4 is the strongest channel, the base station switching determination unit 42 determines the base station 4 as a destination base station,
The base station 3 transmits a channel reserve instruction to the base station 3 that is currently communicating (hereinafter, referred to as a pre-movement base station). Reserve start unit 51 with timer of base station controller 2
a receives this reserve instruction, suspends communication between the base station 3 and the mobile station 11 and returns to the C of the radio channel being used.
At the same time that the connection of H1 is maintained without being released, the reserve timer 55 is activated, and the measurement of the reserve time for the base station 3 is started.

Next, the destination base station determining unit 4 of the mobile station 11
3 is a case where the base station 4 selected as the destination base station is determined to be in the information of the reserved base station information table 48 in which information of the currently reserved base station is stored, and the base station 4 is being reserved. , Reserved base station restart section 45
If the reservation is not being made, the base station switching unit 44 is requested to switch the base station. In this case, the destination base station determining unit 43 detects that the base station 4 is being reserved, and requests the reserved base station resuming unit 45 to switch the base station.

Next, the mobile station 11 shifts to the communication channel CH2 assigned to the base station 4, and the reserved base station resuming unit 45 uses the communication channel CH2 to
Is transmitted. Then, the reserved base station information updating unit 46 deletes the base station information of the movement destination base station 4 from the reserved base station information table 48, and replaces the base station information of the base station 3 before movement with the reserved base station information table 48.
To be stored. Upon receiving the communication restart instruction transmitted by the mobile station 11, the reserve restart unit with timer 53a of the base station controller 2 cancels the reservation of the wireless channel CH2,
At the same time as the communication between the base station 4 and the mobile station 11 is resumed, the reservation timer 55 stops measuring the reserve time for the base station 4. The reserve timer 55
Is assumed to have started measuring the reserve time of the base station 4 at the time when the channel reserve instruction was issued for the base station 4. Thus, the switching to the base station 4 is completed.

The operation performed when the base station 4 is not reserved at the stage of determination by the destination base station determining unit 43 is the same as that of the first embodiment. Communication with the reserved base station 3 is resumed in the same manner as described above if the acquisition of an empty slot for
According to the instruction of 3a, the measurement of the reserve time of the base station 3 by the reserve timer 55 is stopped.

(B) Release of Reserve As a result of (A), from the stage where the base station 3 sets the communication channel CH1 with the mobile station 11 currently communicating with the base station 4 to the reserved state, the mobile station 11 reserves FIG. 1 shows the operation of the wireless communication system according to the second embodiment when a release request is issued.
0 will be described with reference to FIGS. 1 and 8 according to the sequence diagram of FIG.

When the mobile station 11 issues a reserve release request to the reserved base station 3, the mobile station 1
The information of the base station 3 stored in the reserved base station information table 48 is acquired by the first reserved base station information updating unit 46, and the channel CH1, which is the channel with the base station 3 whose reservation is to be released, is transferred. When the reserve release instruction to the base station 3 is sent through the channel CH1, and the reserve end unit with timer 54a of the base station control device 2 receives this, the reserved channel CH1 is released. The timer-equipped reserve end unit 54a also stops measuring the reserve time of the base station 3 by the reserve timer 55.

Next, in the mobile station 11, the information of the base station 3 is deleted from the reserved base station information table 48 by the reserved base station information updating unit 46, and the mobile station 11 returns to C
By shifting to H2, communication with the base station 4 is continued.

The above description is for the case where a request for release of reserve has been made from the mobile station side, and the case where no such request has been made is as follows.

When the measurement of the reserve time of the base station 3 by the reserve timer 55 reaches a time-out, the reserve timer 55 outputs a time-out signal to a reserve end unit with a timer 54a, and the reserve end unit with a timer 54 outputs.
In response to this, a transmits a reserve release command to the reserve base station information updating unit 46 of the mobile station 11. Then, in the mobile station 11, the reserved base station information updating unit 46
The information of the base station 3 is deleted from the reserved base station information table.

In the wireless communication system according to the second embodiment, similarly to the system according to the first embodiment, when the mobile station is moving near the boundary of the wireless zone of a plurality of base stations, or when the mobile station Even in cases where handover processing is frequently used, such as when deterioration occurs frequently, the mobile station can reliably secure a radio channel, and further, since processing such as capturing empty slots is not required, high-speed handover is possible. In addition to being able to overrun, the base station controller has a reserve timer, and the reserve start part, reserve resumption part, and reserve end part of the base station controller are of the reserve timer type, so that the radio channel being reserved is By limiting the standby time to a fixed time, there is no waste due to the presence of wireless channels that wait unnecessarily, and the overall system is more efficient It can communicate to so allow.

In each of the embodiments, the deterioration of the radio condition is detected by measuring the received electric field strength at the mobile station. In addition, other parameters indicating the radio condition are measured. Radio deterioration may be detected. Further, the base station control device may be provided with a radio condition measuring unit and a radio condition table, perform radio monitoring on the base station side, and notify the mobile station of radio deterioration to start the base station switching.

Further, the base station controller cancels the reservation of the radio channel in response to a channel reservation cancellation instruction from the mobile station or occurrence of a timer timeout, but is not limited to this. When the communication is released after the end of the reserved communication, or when the communication is disconnected for any reason, the disconnection is notified from the mobile station, the communication network, or the base station controller itself, or the reservation release instruction is issued. In response to this, it is also possible to stop the reservation of the wireless channel, or to release the reserve in response to an emergency call from another mobile station or the like.

Also, it is assumed that the base station before switching is managed by the same base station controller. However, the present invention is not limited to this. The communication between the base station controllers causes the base station to be managed by a different base station controller. It is also possible to switch.

Further, the number of base stations that can be reserved at the same time is not limited to one, and it is also possible to set such that the base station instructed to reserve the channel can refuse to hold the radio channel. is there.

[0069]

According to the wireless communication system of the first aspect,
In the case where the mobile station device switches base stations in response to movement or radio condition deterioration, it instructs the base station to reserve the wireless channel currently used for communication before switching. By instructing from the reserve base station resuming unit of the mobile station to resume communication using the reserved radio channel as needed, communication can be resumed without delay. Therefore, at the time of handover, when switching back to the base station that was connected immediately before, the wireless channel is held, so that the wireless channel can be reliably secured, and processing such as capturing an empty slot can be performed. Since it is not necessary, high-speed handover is possible.

According to the wireless communication system of the second aspect, the base station control device interrupts the communication between the mobile station and the base station during communication by the reserve start unit, and changes the wireless channel used for the communication. Reserved to make it unavailable for use by other mobile stations, and by the reserve resuming unit having a function of resuming communication using the reserved radio channel, the mobile station can immediately perform handover at the time of handover in the mobile station. When switching back to the base station that was connected to the, the wireless channel is held, so the wireless channel can be reliably secured, and processing such as capturing empty slots is not required, so high-speed handover Becomes possible.

According to the wireless communication system of the fourth aspect, when the base station is switched due to the geographical movement of the mobile station or the deterioration of the wireless condition, the base station switching determining unit of the mobile station determines the base station before the switching. When a channel reservation instruction is issued and the instruction is received by the reserve start unit of the base station controller, the radio channel used for communication between the mobile station and the base station before switching is released to another mobile station. Not
It will be kept in the reserved state. If the mobile station needs to resume communication with the reserved base station, the reserve base station resuming unit of the mobile station issues a communication resuming instruction, and the reserve resuming unit of the base station controller receives the instruction. Then, by releasing the reserved state of the communication channel from the reserved state and restarting the communication, it is possible to restart the communication without delay. For this reason, even when the mobile station is moving near the boundary of the wireless zone of a plurality of base stations, or when the wireless state is frequently degraded due to obstacles or the like, the mobile station can be moved even when handover processing is frequently used. The station can surely secure a wireless channel, and furthermore, high-speed handover is possible because processing such as acquisition of an empty slot is not required.

According to the wireless communication system of the third or fifth aspect, at the time of handover at the mobile station, the wireless channel with the base station with which the mobile station was communicating immediately is kept in a reserved state and the handover process is performed. Even in a situation where the mobile station is frequently used, the mobile station can reliably secure a radio channel, and further, since there is no need to perform processing such as capturing an empty slot, a high-speed handover can be performed. A reserve timer is provided in the control device, and the reserve start unit, the reserve restart unit, and the reserve end unit of the base station control device are set to the reserve timer type, so that the standby time of the reserved wireless channel can be limited to a certain time. Eliminate the waste caused by wireless channels waiting unnecessarily, and efficiently communicate as a whole system. It is possible to obtain so.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a base station control device and a base station according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing a configuration of a mobile station according to Embodiment 1 of the present invention.

FIG. 4 is a diagram showing a data configuration used in a wireless communication system.

FIG. 5 is a block diagram illustrating a configuration of a wireless communication system according to the first embodiment of the present invention.

FIG. 6 is a sequence diagram showing an operation at the time of base station switching in the wireless communication system according to the first embodiment of the present invention.

FIG. 7 is a sequence diagram illustrating an operation of the wireless communication system according to the first embodiment of the present invention at the time of reservation release.

FIG. 8 is a block diagram illustrating a configuration of a wireless communication system according to a second embodiment of the present invention.

FIG. 9 is a sequence diagram illustrating an operation at the time of base station switching in the wireless communication system according to the second embodiment of the present invention.

FIG. 10 is a sequence diagram illustrating an operation at the time of reservation release in the wireless communication system according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a wireless communication system according to a conventional technique.

FIG. 12 is a block diagram illustrating a configuration of a wireless communication system according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Communication network 2, 102 Base station controller 3, 4, 103, 104 Base station 5, 6, 105, 106 Wireless zone 11, 111 Mobile station 21, 31 Antenna 22, 32 Radio controller 23 Base station controller Connection units 24, 34 Modulation units 25, 35 Demodulation units 26 Base station connection units 27, 33 Communication control units 28, 36 Input units 29, 37 Output units 30 Line control units 41, 61 Wireless state measurement units 42, 62 Base station switching Determination unit 43 Destination base station determination unit 44, 63 Base station switching unit 45 Reserved base station restart unit 46 Reserved base station information updating unit 47, 64 Wireless information table 48 Reserved base station information table 51 Reserve start unit 52, 65 Switching unit 53 Reserve resumption unit 54 Reserve end unit 51a Reserve start unit with timer 53a Reserve with timer Breakfast resumption portion 54a reserve end portion 55 reserve timer with timer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Yamaguchi 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] A mobile station, a plurality of base stations, and a base station controller that manages the plurality of base stations, wherein the base station and a mobile station located in a wireless zone of the base station are wireless. In a wireless communication system which is capable of connecting and wherein the mobile station is capable of switching the base station to which the mobile station is connected during communication, the mobile station is connected to the base station which is wirelessly connected to the mobile station during communication. It is determined whether or not to perform switching, and if it is determined that switching is to be performed, the wireless channel used for the wireless connection is transmitted to the base station that has been wirelessly connected before switching to another base station. A base station switching determining unit that issues an instruction to reserve the wireless channel without using it for connection; and a reserve instruction from the base station switching determining unit that reserves a wireless channel without using it for wireless connection with another. A reserved base station information table that stores information about the reserved base station, and a base station that is scheduled to be switched by the determination of the base station switching determining unit by referring to the information of the reserved base station information table. Is a destination base station determining unit that determines whether or not the base station is being reserved, and acquires information on the reserved base station from the reserved base station information table and communicates with the base station. A reserve base station resuming unit that cancels the reservation of the wireless channel held by the base station and resumes communication on the wireless channel by instructing the reservation to be resumed, or at the time of the reserve instruction, or when the reservation is canceled and the communication is resumed. A reserve base station information updating unit that updates the reserve base station information table. That the wireless communication system. 2. A mobile station comprising: a mobile station; a plurality of base stations; and a base station control device for managing the plurality of base stations, wherein the base station and a mobile station located in a wireless zone of the base station are wireless. In a wireless communication system which can be connected and the mobile station can switch the base station to be wirelessly connected during communication, the base station control device performs communication by wireless connection between the mobile station and the base station. Suspend, reserve the wireless channel used for the wireless connection, and reserve the wireless channel without using it for other wireless connections.Release the reserved state for the reserved wireless channel, and suspend. And a reserve restart unit for restarting the communication by wireless connection with the base station through the wireless channel. 3. The wireless communication system according to claim 2, wherein the base station control device measures a time in a reserved state with respect to the wireless channel reserved by the reserve starting means. A reserve timer that outputs a time-out signal when a predetermined time elapses, and a time-out signal output from the reserve timer. A reserve end unit with a timer that cancels a reserved state in the reserved wireless channel and enables use by wireless connection with another of the wireless channel, wherein the reserve start unit includes a mobile station, a base station, Suspends the communication through the wireless connection, and changes the wireless channel used for the wireless connection to the other. A reserve start unit with a timer for instructing the reserve timer to start measuring the time during which the wireless channel is kept in a reserve state without using the line connection, and the reserve restart unit includes: When the reserved state is released for the reserved wireless channel and the communication is resumed by the wireless connection between the suspended mobile station and the base station via the wireless channel, the reservation timer is timed. A wireless communication system, which is a reserve restart unit with a timer for instructing a stop. 4. A mobile station comprising a mobile station, a plurality of base stations, and a base station control device for managing the plurality of base stations, wherein the base station and a mobile station located in a wireless zone of the base station are wireless. In a wireless communication system which is capable of connecting and wherein the mobile station is capable of switching the base station to which the mobile station is connected during communication, the mobile station is connected to the base station which is wirelessly connected to the mobile station during communication. It is determined whether or not to perform the switching, and if it is determined to perform the switching, the wireless channel used for the wireless connection is wirelessly connected to another base station before the switching. A base station switching determining unit that issues an instruction to reserve the wireless channel without using it, and reserves a wireless channel without using it for wireless connection with another by a reserve instruction from the base station switching determining unit. A reserved base station information table storing information about the reserved base station, and by referring to the information in the reserved base station information table, the base station to be switched is determined by the base station switching determination unit. A destination base station determining unit that determines whether the base station is a reserved base station, and obtains information on the reserved base station from the reserved base station information table to communicate with the base station. By instructing to resume, the reserved base station resuming unit which cancels the reservation of the wireless channel held by the base station and resumes communication on the wireless channel. A reserve base station information updating unit for updating the reserve base station information table, wherein the base station A controller for interrupting communication by a wireless connection between the mobile station and the base station and reserving a wireless channel used for the wireless connection without using the wireless channel for another wireless connection; A reserved channel for releasing the reserved state of the wireless channel, and restarting the communication by wireless connection between the interrupted mobile station and the base station in the wireless channel. Wireless communication system. 5. The wireless communication system according to claim 4, wherein the base station control device measures a time in a reserved state for the wireless channel reserved by the reserve start means. A reserve timer that outputs a time-out signal when a predetermined time elapses, and a time-out signal output from the reserve timer. A reserve end unit with a timer that cancels a reserved state in the reserved wireless channel and enables use by wireless connection with another of the wireless channel, wherein the reserve start unit includes a mobile station, a base station, Suspends the communication through the wireless connection, and changes the wireless channel used for the wireless connection to the other. A reserve start unit with a timer for instructing the reserve timer to start measuring the time during which the wireless channel is kept in a reserve state without using the line connection, and the reserve restart unit includes: When the reserved state is released for the reserved wireless channel and the communication is resumed by the wireless connection between the suspended mobile station and the base station via the wireless channel, the reservation timer is timed. A wireless communication system, which is a reserve restart unit with a timer for instructing a stop.