JP2002359864A - Method for switching attribute of mobile terminal station to base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower load of a radio base station by deconcentrating the access concentration of mobile terminal stations to the radio base station. SOLUTION: A mobile terminal station 1 belongs to a radio base station 2-B and conducts communication, but the mobile terminal station 1 simultaneously receives beacon signals from other radio base stations (2-A, 2-C and 2-D). When many mobile terminal stations belong to the radio base station 2-B in the above state, access load of the radio base station 2-B becomes large to lower network performance since all of the respective mobile terminal stations randomly conducts communication with the radio base station 2-B. The mobile terminal station 1 acquires information on the receiving power of beacons transmitted from each of the radio base stations, which the mobile terminal station 1 itself can receive, and on the number of terminals belonging to each radio base station, and performs decision control to switch to a radio base station to be an attribution destination, on the basis of the information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for switching a mobile terminal belonging to a base station, and more particularly to a CSMA / CA (Carrie).
rSense Multiple Access Wi
mobile terminal for switching the destination of a mobile terminal station to another base station when the number of mobile terminal stations belonging to a base station is large and the access load is large in a wireless LAN (Local Area Network) system The present invention relates to a base station belonging switching method for a station.

[0002]

2. Description of the Related Art Conventionally, in this type of mobile terminal base station belonging switching method, an example of a system for changing the belonging of a wireless LAN to a base station is described in, for example, a wireless LAN system (Japanese Patent Laid-Open No. 8-274782). Have been.
In this system, a plurality of slave units belonging to a specified master unit among a plurality of master units are connected by a wireless line, and the master unit exchanges data from the slave unit with another master unit or its own unit. In the case of distributing to a slave unit, means for belonging management, traffic monitoring, change instruction, and the like are provided on the wired network, and a change instruction of the parent unit to belong to is provided by these operations.

[0003]

The above-mentioned conventional method of switching the base station belonging to a mobile terminal has means for belonging management, traffic monitoring, change instruction, etc. on a wired network, and the base unit belonging to the base station by the operation thereof. Will be instructed to change
In order to realize these means, there is a problem that the scale of the entire system becomes large and base station belonging switching control is complicated.

[0004] It is an object of the present invention to reduce the load by dispersing the concentration of access of a mobile terminal to one base station, to provide a means for switching to another base station based on beacon information, and to change the state of the radio link. It is an object of the present invention to provide a base station belonging switching method for a mobile terminal which can flexibly cope with the problem.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for switching a base station belonging to a mobile terminal in a CSMA / CA wireless LAN system in which the mobile terminal can belong to any of a plurality of base stations. In a case where the number of mobile terminals is large and the access load of the base station is large, the affiliation is switched to another base station by the preset judgment control of the mobile terminal.

The base station to which the mobile terminal belongs is independent of each other in order to notify the information of the zone established by the mobile station to the mobile terminal to which the mobile terminal belongs, the nearby mobile terminal and the nearby base station. , A beacon signal is transmitted at regular intervals, and the mobile terminal receives a beacon signal from a base station to which the mobile terminal belongs and a beacon signal from peripheral base stations.

The base station is provided with means for monitoring the number of the mobile terminals to which the mobile station belongs, and outputting terminal number information, the terminal number information, the transmission interval of the beacon signal, and its own base station. Means for transmitting a beacon signal to which a zone ID is added.

[0008] The mobile terminal may receive beacon signals from a plurality of base stations, measure reception levels of beacon signals from each of the base stations, and transmit beacon signals from each of the base stations. Means for detecting the number-of-terminals information added to the base station, and selecting a base station to which the mobile station belongs based on the obtained reception level and the number-of-terminals information.

The wireless LAN module of the mobile terminal includes an interface unit for connecting an external device to transmit and receive a packet, an RF unit for transmitting and receiving a radio wave, and a modem unit for modulating and demodulating a signal between the RF units. M for controlling transmission and reception of signals between the modem unit and the interface unit
It has an AC unit and a CPU unit that controls the operation of each unit, and a signal received from a wireless line is demodulated by the modem unit through the RF unit and returned to data by deframing from a wireless frame by the MAC unit. The user data is transferred to an information processing unit (PC) via a PC interface unit, and wireless control data is processed by the CPU unit.

[0010] In the transmission to the wireless line by the wireless LAN module, user data is sent from the external device to the MAC unit via the PC interface unit, and control data is generated by the CPU unit and transmitted to the MAC unit. The data sent to the MAC unit is converted into a radio frame, modulated by the modem, and transmitted to the RF unit.
And transmitted to a wireless line through a communication unit.

[0011] The beacon signal received by the mobile terminal includes information on the reception power of the beacon signal by the modem unit and the number of terminals belonging to the base station that transmitted the beacon from the data of the beacon signal processed by the MAC unit. The CPU unit stores the data, and the stored data is updated by the acquired information every time a beacon signal from the same base station is received, and the received power is received a plurality of times for the same base station for each packet. An average value of the power information is obtained, and the CPU
The unit has a timer for starting switching determination and performs base station switching determination control at regular time intervals.

In addition, the base station switching judgment control to which the mobile terminal belongs is started by a notification from the timer, and the number of terminal belonging to the base station and the number of terminal belonging to another base station are started. Are compared, and a base station having less than a preset numerical value and having the largest received power is selected.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In the present embodiment, a plurality of wireless base stations 2 (2-2) are connected to a wired network 3 (Ethernet, etc.).
A, 2-B, 2-C, 2-D) are connected.

A CSMA / CA (Carrier) in which the mobile terminal station 1 can belong to any of a plurality of radio base stations 2
Sense Multiple Access Wi
In the wireless LAN system of the th Collision Avoidance (collision avoidance type carrier detection multiple access) method, when the number of mobile terminal stations 1 belonging to the wireless LAN system is large and the access load of the wireless base station 2 is large, the preset mobile terminal station 1 Is switched to another wireless base station by the judgment control of.

The radio base station 2 to which the mobile terminal station 1 belongs
In order to notify the mobile terminal station 1 belonging thereto and the nearby mobile terminal station 1 and the surrounding wireless base station 2 of the information of the zone established by the own station, a beacon signal is transmitted independently and at a constant interval. The mobile terminal station 1 receives a beacon signal from the wireless base station 2 to which the mobile terminal station 1 belongs and a beacon signal from the surrounding wireless base station 2.

The mobile terminal station 1 performs communication while belonging to the radio base station 2-B, but the other radio base stations (2-A, 2-A).
C, 2-D) are also received at the same time. If the number of mobile terminal stations 1 belonging to the radio base station 2-B is large in the above state, all the mobile terminal stations randomly communicate with the radio base station 2-B. The access load on the station 2-B increases, and the performance of the network decreases.

The mobile terminal station 1 obtains information on the reception power of the beacon signal transmitted from all the radio base stations that can be received by the mobile terminal station 1 and the number of terminals to which the mobile base station belongs, and based on the information, the radio base station to which the mobile terminal station belongs. The switching control to the station is performed.

FIG. 2 is a block diagram showing a beacon processing unit of the radio base station according to the present embodiment. Beacon processing unit 1 of FIG.
In 6, the beacon identification unit 11 extracts a beacon frame from the received frame and sends a transmission beacon frame to the modem. The mobile terminal monitoring unit 12 monitors the number of mobile terminal stations belonging to the own radio base station 2 based on a signal from the beacon identification unit 11 and outputs terminal number information. Terminal number information adding section 13 adds terminal number information to the transmission signal and outputs the transmission signal. The beacon information transmitting section 14 transmits the beacon information including the terminal number information from the terminal number information adding section 13 and the zone ID from the zone ID information adding section 15 to the beacon identification 1.
Send to 1.

FIG. 3 is a block diagram showing details of the mobile terminal station of the present embodiment. In FIG. 3, a mobile terminal station 1 is configured by connecting a wireless LAN module 4 and a PC 5.
The PC 5 is a personal computer, a workstation, or the like. The PC interface 6 of the wireless LAN module 4 is a PC
The PC 5 such as an MCIA card and a PCI bus has a function for connecting an external device.

The LAN module 4 is connected to the
F unit 9, modem unit 8, MAC unit 7, and PC interface unit 6.
The U section 10 is connected. PC interface 6
Exchanges packets with the PC 5. The MAC unit 7 controls wireless transmission and reception. The modem unit 8 performs wireless modulation and demodulation. The RF unit 9 is a wireless transmitting / receiving unit.

Next, the operation of this embodiment will be described. First, in FIG. 1, it is assumed that the mobile terminal station 1 belongs to the radio base station 2-B. Each radio base station 2 (2-A, 2-
C, 2-D) are each independently provided at a fixed interval in order to notify the mobile terminal station 1 and the neighboring mobile terminal stations and the surrounding radio base stations to which the information of the zone established by the own station belongs. Transmits a beacon signal. Then, it is assumed that the mobile terminal station 1 is receiving not only the beacon of the radio base station 2-B but also the beacons of the radio base stations 2-A, 2-C and 2-D.

The information in the beacon signal includes the transmission interval of the beacon signal, the zone ID established by the own radio base station 2-B, and the like. It is necessary to include information on the number of mobile terminals that are present.
The beacon signal received by the mobile terminal station 1 is generated by the CPU 10 in the same manner as the control data described above,
It is sent to the AC unit 7. In this case, in this embodiment, the reception power of the beacon signal in the modem unit 8 and the number of mobile terminals belonging to the wireless base station 2 that transmitted the beacon signal from the data in the beacon signal processed in the MAC unit 7 The CPU unit 10 acquires and stores the above information. The stored information data is updated with the acquired information every time a beacon signal is received from the same wireless base station.

Since the received power of the beacon signal is expected to vary from packet to packet, the average value of the power information received a plurality of times for the same radio base station may be taken. C
The PU unit 10 has a timer for switching determination start, and performs determination control of base station switching at regular time intervals based on the flowchart of FIG.

In FIG. 3, a signal received from a wireless line is demodulated by a modem unit 8 via an RF unit 9 and returned to data by a MAC unit 7 from a wireless frame by deframing or the like. Here, the user data is transferred to the PC 5 via the PC interface unit 6. The control data received from the wireless line is processed by the CPU 10. In transmission to a wireless line, user data is sent from the PC 5 to the MAC unit 7 via the PC interface unit 6. The control data is generated by the CPU 10 and sent to the MAC 7. M
The data sent to the AC unit 7 is converted into a wireless frame, modulated by the modem 8, and transmitted to the wireless line via the RF unit 9.

Next, the operation of the present embodiment will be described with reference to the flowchart shown in FIG. 4. In step S1, the process starts in response to a notification from the timer, and the terminal of each wireless base station which has been acquired in advance. Compare the number of belongings.
Now, the number of terminals belonging to the radio base station to which the own mobile terminal station belongs (A) is compared with the number of terminals belonging to another radio base station (B), and (A) − (B)> K1 : (K1 is a constant) It is determined whether or not there is another wireless base station represented by the formula. Note that K
The value of 1 needs to be set to an appropriate value in advance depending on the environmental conditions (the number of radio base stations, the number of mobile terminals, the installation location of the radio base station, etc.) in which the system is used.

If there is no base station satisfying the equation in step S1, (NO) nothing is performed and the process ends. In step S2, if there is a radio base station that satisfies the formula, it is determined whether there is a radio base station whose beacon reception power is higher than the radio base station with which the own mobile terminal is synchronized among the corresponding radio base stations to decide. If there is a radio base station with a large reception power, the radio base station with the highest reception power is selected (step S4), and the radio base station to which the radio base station currently belongs is released. (Step S5).

In step S2, if there is no wireless base station having a large received power, it is determined whether there is a wireless base station that satisfies the following among wireless base stations that satisfy the formula (step S3).

The received power (C) of the radio base station to which the own mobile terminal belongs and the received power (D) of the other radio base stations are compared, and (C)-(D) <K2: ( (K2 is a constant) The value of K2 also needs to be set in advance by the system in the same manner as K1.

If no wireless base station satisfies the equation in step S3 (NO), the process ends. If there is a wireless base station that satisfies the formula, the wireless base station with the highest received power is selected from them (step S
4), release the affiliation of the wireless base station to which the wireless base station currently belongs, and perform the process of belonging to the selected wireless base station (step S).
5).

[0031]

As described above, according to the present invention, a CS that allows a mobile terminal to belong to any of a plurality of base stations is provided.
In the MA / CA wireless LAN system, when the number of mobile terminals belonging to one base station is large and the access load is large, the destination is switched to another base station at the discretion of each mobile terminal and the access load is changed. By dispersing
The first effect is to reduce the load by dispersing the access concentration of the mobile terminal station to one wireless base station. The reason is that each terminal has a means for switching to another base station based on information based on the beacon signal.

The second effect is that it is possible to flexibly cope with a change in the status of the radio line. The reason is that the switching decision is made at regular intervals by the timer.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system configuration according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a wireless base station according to the present embodiment.

FIG. 3 is a block diagram illustrating a configuration of a terminal station according to the present embodiment.

FIG. 4 is a flowchart for explaining the operation of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mobile terminal station 2 (2-A, 2-B, 2-C, 2-D) Radio base station 3 Wired network 4 Wireless LAN module 5 PC 6 PC interface 7 MAC section 8 Modem section 9 RF section 10 CPU section 11 Beacon identification unit 12 Mobile terminal monitoring unit 13 Terminal number information addition unit 14 Beacon information transmission unit 15 Zone ID information addition unit 16 Beacon processing unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K033 AA07 CA07 CB01 CC01 DA02 DA19 EA03 EA05 5K067 AA28 BB21 CC08 DD17 EE02 EE10 FF23 FF24 FF25 FF27 HH22 HH23 JJ37 KK13 LL01 LL11

Claims (8)

[Claims] 1. In a CSMA / CA wireless LAN system in which a mobile terminal station can belong to any of a plurality of base stations, when the number of mobile terminal stations to which the mobile terminal station belongs is large and the access load of the base station is large. A method for switching a mobile terminal station to another base station according to a preset determination control of the mobile terminal station. 2. The base station to which the mobile terminal station belongs is for notifying the information of the zone established by the mobile terminal station to the mobile terminal station to which the mobile terminal station belongs, the nearby mobile terminal station, and the nearby base station. The mobile terminal according to claim 1, wherein the mobile terminal transmits beacon signals from a base station to which the mobile terminal station belongs and a beacon signal from peripheral base stations independently. A method for switching a base station belonging to a station. 3. The base station monitors a number of the mobile terminal stations belonging to the base station and outputs terminal number information. The terminal number information, a transmission interval of a beacon signal, and a base station established by the base station. Means for transmitting a beacon signal to which a zone ID is added.
A method for switching a base station belonging to a mobile terminal station according to the above description. 4. The mobile terminal station includes: means for receiving beacon signals from a plurality of the base stations; means for measuring a reception level of a beacon signal from each of the base stations; and a beacon from each of the base stations. The mobile terminal according to claim 1 or 2, wherein the mobile terminal according to claim 1 or 2, wherein means for detecting information on the number of terminals added to a signal, and a base station to which the mobile station belongs is selected based on the obtained reception level and the information on the number of terminals. A method for switching a base station belonging to a station. 5. The wireless LAN module of the mobile terminal station comprises: an interface unit for connecting an external device to transmit and receive a packet; an RF unit to transmit and receive a radio wave;
A modem unit for modulating and demodulating a signal between the F units, and a MA for controlling transmission and reception of signals between the modem unit and the interface unit
A C section, and a CPU section for controlling the operation of each section,
A signal received from a radio line is demodulated by the modem unit via the RF unit, returned to data by deframing from a radio frame by the MAC unit, and user data is transmitted to a PC.
5. The method according to claim 4, wherein wireless control data is transferred to an information processing unit (PC) via an interface unit, and wireless control data is processed by the CPU unit. 6. In transmission to a wireless line by the wireless LAN module, user data is sent from the external device to the MAC unit via the PC interface unit, and control data is generated by the CPU unit and transmitted to the M
5. The mobile terminal station according to claim 4, wherein data sent to an AC unit and sent to the MAC unit is converted into a radio frame, modulated by the modem, and sent to a wireless line via the RF unit. Base station belonging switching method. 7. The beacon signal received by the mobile terminal station, the received power of the beacon signal by the modem unit,
The CPU unit stores information on the number of terminals belonging to the base station that transmitted the beacon signal from the data of the beacon signal processed by the MAC unit, and acquires the stored data every time a beacon signal from the same base station is received. The data is updated with the information, and the received power is obtained by averaging the power information received a plurality of times for the same base station for each packet.
7. The method according to claim 4, 5 or 6, wherein the unit has a timer for starting switching determination and performs base station switching determination control at fixed time intervals. 8. The base station switching judgment control to which the mobile terminal station belongs starts processing based on a notification from the timer, and the terminal belonging number of the belonging base station and the terminal belonging number of another base station. Compare the number, less than the preset number,
8. The method according to claim 7, wherein the base station having the highest received power is selected.