JP3400061B2 - Wireless communication system and wireless communication terminal - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system for wirelessly transmitting packets between a plurality of wireless communication terminals such as a wireless LAN system, and more particularly to a system having a plurality of service areas and its wireless communication terminal. .

[0002]

[Prior Art] In offices and office buildings,
LA using a coaxial cable as the information transmission system
N (Local Area Network) is often used. In such a wired LAN, when the layout is changed from the initial installation state, it takes time and cost to re-install it. Therefore, a wireless LAN is strongly desired. Particularly in Japan, CSMA / CD (Carrier Sense Multiple Access with 10 Mbps of IEEE802.3 standard widely used as a wired LAN is used.
Collision detection) is being standardized, while ensuring compatibility with the method.

The wireless LAN currently under study has a communication area within a radius of several tens of meters. This value was targeted because most users of existing wired LANs such as 10BASE5 are using it within a building of 400 m ² or due to the technical difficulty of high-speed data transmission within the building. Is. This communication area is called a basic service area and is used as a minimum unit when configuring a wireless LAN system. Further, in the case of performing communication in a range wider than the basic service area, it is considered that a plurality of basic service areas are arranged and the basic service areas are interconnected and expanded by a wired LAN called a distribution system.

[0004]

By the way, wireless LAN
There are some issues to be solved in order to realize
One of them is location management of moving wireless communication terminals. That is, in the wireless LAN, the wireless communication terminal may move not only within the above-mentioned basic service area but also across the service area or even across the system. Therefore, it is necessary to manage the position of the wireless communication terminal so that data transmission / reception can be performed correctly wherever the wireless communication terminal exists.

When laying a wireless LAN, the traffic in each service area should be averaged.
It is common to construct a system in consideration of the requirements for determining traffic such as the number of wireless communication terminals and the type of data to be transmitted. However, due to layout changes etc., wireless communication terminals are concentrated in a specific service area,
When a wireless communication terminal that handles high traffic is newly added and the traffic is biased, data collision frequently occurs in the service area, resulting in chronic congestion. This reduces the throughput of the entire system and is very undesirable.

Further, in order to cope with an increase in the number of wireless communication terminals and to cover a wide service area, service areas of the same frequency are sufficiently separated from each other so as not to interfere with each other, as in a cellular radio telephone system. The system may be constructed by repeatedly arranging. But,
If a sufficient repetition distance cannot be secured due to structural limitations of the building, interference occurs and transmission quality deteriorates. Also, when another system sharing the frequency is present nearby, interference similarly occurs.

Therefore, when constructing and operating a wireless LAN, it is necessary to understand the traffic conditions of the own system and the conditions of neighboring frequency sharing systems. However, since the construction and management of the wireless LAN are usually performed by the user, it is practically difficult to grasp the various situations described above sufficiently accurately in advance. Therefore, an effective alternative solution was desired.

The present invention has been made in view of the above circumstances, and a first object thereof is a wireless communication system capable of performing high-quality data transmission without grasping traffic conditions in advance. And to provide its wireless communication terminal. A second object of the present invention is to provide a wireless communication system and a wireless communication terminal thereof capable of smoothly and reliably selecting a service area to which a user belongs.

[0009]

The present invention for achieving the above first object has a plurality of service areas arranged such that at least some of the areas overlap each other,
In a wireless communication system having a function of allowing a plurality of wireless communication terminals to perform data transmission via a wireless channel in these service areas, the wireless communication terminal is provided with a state determination means and a service area selection means. There is. Then, the state determination means determines the state of each service area according to the power-on of the terminal, determines the service area candidates to which the service area can belong based on the determination result, stores the candidate list, and stores the candidate list. Based on the selected candidate list, the service area to which the user belongs should be selectively selected from the plurality of service areas.

[0010]

[0011]

The state determination means determines whether or not the transmission quality of the packet transmitted within the service area to which it belongs has deteriorated below a predetermined value, and in response to the determination that the transmission quality has deteriorated below a predetermined value. A service area that should belong to a different service area is changed to another service area.

[0013]

[0014]

[0015]

[0016]

[0017]

Further, according to the present invention, by the above state judging means,
When the states of all the service areas stored as the candidate list do not satisfy a predetermined state, the operation of changing the candidate list of service areas to which the user can belong is also characterized.

On the other hand, in order to achieve the second object, the present invention has a plurality of service areas arranged such that at least some of the areas overlap each other, and the wireless communication terminals are provided in these service areas, respectively. In addition to fixedly installing a gateway station connected via a wireless channel to
In a wireless communication system having a function of connecting these gateway stations via a wired transmission line and having a plurality of wireless communication terminals located in different service areas perform data transmission via the gateway station and the wired transmission line The wireless communication terminal is provided with affiliation candidate determining means, state determining means, and service area selecting means. Then, the affiliation candidate determination means determines the candidate of the service area to which the service area can belong based on the reception state of the control packet including the service area identification information periodically transmitted from the gateway station for each of the service areas. The state determining means determines whether or not the state of the service area to which the user belongs is in a satisfactory state. Then, when it is determined by this state determination means that the service area to which it belongs is not in a satisfactory state, the service area selection means selects an appropriate service area from the candidates decided by the belonging candidate decision means. It is the one that is selected.

[0020]

[0021]

[0022]

As a result, according to the present invention, after the operation of the system is started, if, for example, the traffic increases or the transmission quality deteriorates in the service area to which the system belongs, the change in the status of these service areas causes the wireless communication terminal itself. Is determined by. Then, according to the determination result, the wireless communication terminal itself switches its own affiliation destination from the current service area to another service area to which it can belong.

Therefore, each wireless communication terminal always uses the optimum service area within a possible range without increasing the traffic conditions of its own system and the frequency sharing system in the vicinity. It becomes possible to perform quality data transmission. Also, since each wireless communication terminal autonomously selects a service area, compared to a system in which the status of each service area is centrally managed by a base station and the belonging of each wireless communication terminal is managed and controlled. The system configuration and control can be simplified, and an inexpensive system can be provided as a whole.

On the other hand, according to another aspect of the present invention, a control packet sent from a gateway station fixedly installed in each service area is received, and a list of service areas to which the user can belong is created based on the reception result. If the service area you belong to becomes unsatisfied, the next candidate for the service area is selected from the list above and the affiliation is switched to this service area. Can be done.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a uniformly distributed wireless LAN system according to an embodiment of the present invention. The equal distribution type is a system in which both the access control system and the information transmission system communicate in a distributed system.

This wireless LAN system includes a plurality of basic service areas (hereinafter simply referred to as service areas) E1,
It has E2, E3, ..., En. These service areas E1, E2, E3, ..., En are positioned such that adjacent service areas partially overlap each other. In addition, each service area E1, E
The range covered by 2, E3, ..., En is set to a radius of several tens of meters in consideration of the size of a general office and the technical difficulty of high-speed wireless transmission in a premises. Of the service areas E1, E2, E3, ..., En, mutually overlapping and close areas are assigned different radio frequencies in order to separate the areas from each other, and the distances such as the service areas E1 and En are different from each other. The same radio frequency is repeatedly allocated to the service areas sufficiently apart from each other in order to effectively use the radio frequency.

The wireless communication terminals M1, M2, ..., Mm belong to any of the service areas E1 to En and perform communication depending on their existing positions. That is, wireless communication terminals belonging to the same service area are directly connected via a radio frequency channel assigned to the service area, and wireless transmission of data is performed via this channel. The CSMA / CD method is used as an access protocol for this data transmission. CSMA / C
D is a method for a plurality of wireless communication terminals to share a common wireless transmission path, and each wireless communication terminal starts packet transmission after waiting for the carriers on the transmission path to run out. Then, when a packet collision is detected during transmission, the packet transmission is stopped at that point, and the packet is retransmitted after a random arbitrary time has elapsed.

Further, gateway stations R1 to Rn are installed in the service areas E1 to En, respectively.
1 to Rn are connected via a wired transmission line WL. Each of the gateway stations R1 to Rn and the wire transmission line WL constitutes a distribution system. The gateway stations R1 to Rn are wired transmission lines W
A wireless relay transfer function between L and the wireless communication terminals M1 to Mm and a position management registration function of wireless communication terminals belonging to the corresponding service areas E1 to En, and wireless belonging to different service areas. The communication terminals are connected to each other via the wired transmission line WL. In addition, each gateway station R1 to Rn
Connection between each of the wireless communication terminals M1 to Mm is performed via the radio frequency channels assigned to the service areas E1 to En, as in the case of the above wireless communication terminals.
The access protocol for the data transmission is CSMA.
/ CD method is used.

The wireless communication terminals M1 to Mm are composed of data terminals such as personal computers and workstations, various terminal devices such as voice terminals and image terminals, and a wireless module. FIG. 2 is a circuit block diagram showing the configuration of the wireless module.

The wireless module has a digital interface 11 to which the above-mentioned various terminal devices (not shown) are connected. The digital interface 11 performs level conversion of data between the terminal device and the wireless module main body, frame synchronization, speed conversion, and the like, and also drives the wireless module. The transmission data input from the terminal device via the digital interface 11 is input to the packet generation unit 12. This packet generator 12
Adds a preamble PA for wireless transmission, a start frame delimiter SFD, a target station address DA, a transmission station address SA, a packet type TYP and a data length LEN to the transmission data from the digital interface 11 to form a packet frame. To do.

FIG. 3 shows an example of the structure of the packet frame. Of these, in the destination station address DA, in addition to the addresses of the destination wireless communication terminal and the gateway station, in the case of broadcast transmission, a broadcast address consisting of all "0", for example, is also inserted. The packet types include information packets and control packets, and the control packets include location registration packets and area number notification packets. In each packet, for example, the information packet is “00”, the location registration packet is “10”,
The area number notification packet is provided with a packet type identification code such as "11".

The transmission packet frame output from the packet generation unit 12 is input to the error correction coding unit 13. The error correction coding unit 13 performs coding processing for error correction and error detection suitable for wireless transmission,
At the end of the packet, as shown in FIG. 3, the error correction code FE
C is added. Then, the transmission packet frame output from the error correction unit 13 is input to the modulation unit 14.

The modulator 14 modulates the transmission intermediate frequency signal with the transmission baseband signal that has been converted into a transmission packet frame, and outputs the modulated transmission intermediate frequency signal to a high frequency (R
F) Input into section 15. The high frequency unit 15 is a local oscillator,
It has a frequency mixer and a transmission power amplifier. Then, the transmission intermediate frequency signal is frequency-converted into a carrier wave corresponding to the radio channel frequency, level-converted to a predetermined transmission power level, and then supplied to the antenna 16 to be transmitted from the antenna 16 to the radio transmission path.

On the other hand, the modulated carrier wave coming from the communication partner terminal via the wireless transmission path is received by the antenna 16 and then input to the high frequency section 15. In the high frequency unit 15, the received modulated carrier wave is subjected to high frequency amplification and then frequency-converted into a reception intermediate frequency signal, which is input to the demodulation unit 17. The demodulation unit 17 demodulates the reception intermediate frequency signal into a baseband reception packet frame, and performs carrier synchronization and clock synchronization (clock reproduction) based on the reception intermediate frequency signal. Then, the received packet frame and the demodulated clock are supplied to the error correction decoding / detection unit 18.

The error correction decoding / detection unit 18 detects an error contained in the received packet frame and performs an error correction decoding process, and the received packet frame after the error correction is transferred to the packet decomposition unit 19. The packet disassembling unit 19 determines the destination station address DA, the transmission station address SA, the packet type TYP from the received packet frame.
And data DATA are decomposed and extracted. Then, if the destination station address matches the own station address, or if it is a broadcast address, the packet type is identified. When the packet type is an information packet, the destination station address, transmission address and user data are supplied to the digital interface 11 for transfer to the terminal device, while when the packet type is a control packet, the transmission station address and control data are supplied. To the control unit 30. If the destination station address is another station address, the received packet is discarded.

In addition to the control unit 30 as a control system, the wireless module includes a reception level (Rx level) measurement unit 21.
A carrier detection unit 22 and a collision detection unit 23. These circuits are used to perform access control by the CSMA / CD system and service area switching control which is a feature of the present invention.

That is, first, the reception level measuring section 21
The signal level in the specified frequency band in the received intermediate frequency signal is detected. The carrier detection unit 22 compares the signal level detected by the reception level measurement unit 21 with a predetermined threshold value, and determines whether the wireless transmission path is empty or not.
Further, it measures the reception level of the control packet coming from the gateway stations R1 to Rn and notifies the control unit 30 of the measured value.
The collision detection unit 23 takes in the received packet frame output from the demodulation unit 17, and the preamble PA or the random pulse for collision detection inserted before the preamble PA is received while maintaining the code state at the time of transmission. The occurrence of a collision is detected by determining whether or not the collision has occurred. The control unit 30 is notified of the occurrence of a collision. Further, the collision detection unit 23 counts the number of collision detections per unit time, and the count value is notified to the control unit 30.

The control unit 30 is provided with, for example, a microcomputer as a main control unit, and its control function is based on the control of each functional block described above and the detection results of the carrier detection unit 22 and the collision detection unit 23. CSM
A service area control unit 31 is provided in addition to A / CD access control, wireless channel frequency switching control associated with movement of a wireless communication terminal, and the like.

The service area control unit 31 creates a list of service areas to which its own wireless communication terminal can belong when the power is turned on or when its own wireless communication terminal moves to another service area. Then, the transmission quality and the traffic state in the service area to which it belongs are monitored, and the switching control of the service area to which they belong is performed based on the monitoring result.

Next, the operation of the radio communication terminals M1 to Mm configured as above will be described. Note that, for simplicity of description, it is assumed that the wireless communication terminals M1 to Mm manage their positions by registering their addresses in the gateway stations R1 to Rn of the service areas E1 to En. To do.

The gateway stations R1 to Rn of the respective service areas E1 to En shown in FIG. 1 repeatedly broadcast area notification packets at a constant cycle. For example, the gateway station R1 in the service area E1 uses the broadcast address as the target station address DA and the own station address # R1 as the transmitting station address SA.
“11” indicating that the packet is an area number notification packet is inserted in the packet type TYP, and “service area number # E1” is inserted in the data area DATA, and the packets are transmitted at a constant cycle T. Similarly, the service area E2
Of the gateway station R2 of the destination station address DA, the broadcast station address SA, its own station address # R2, and the packet type TYP of "11" indicating an area number notification packet in the data area DATA. "Service area number # E2" is inserted and transmitted in a constant cycle T. FIG. 4 shows an example of the broadcast timing of the area number notification packet by each of the gateway stations R1 to Rn.

In this state, the service area E1
When the power is turned on, the wireless communication terminal M2 existing in the area where E and E2 overlap with each other first moves to step 7a as shown in FIG. To create.

That is, the radio communication terminal M1 firstly receives the radio channel frequency f assigned to the service area E1.
In order to receive 1, the local oscillator of the high frequency unit 15 is set to the local oscillation frequency corresponding to the radio channel frequency f1. In this state, when the area number notification packet transmitted from the gateway station R1 using the radio channel frequency f1 is received, the "service area number # E1" and the source gateway station address # R1 are received from the received packet.
To extract. Then, it is determined whether or not the reception level at the time of receiving the reception packet, the interference level, the bit error rate, and the like satisfy a predetermined threshold value, and when it is determined that the satisfaction is satisfied, The extracted "service area number # E1" and the source gateway station address # R1 are stored in the corresponding area of the list memory provided in the service area control unit 31, together with the information indicating the reception quality such as the reception level. Remember.

When the list information about the service area E1 is obtained in this way, the radio communication terminal M1 receives the radio channel frequency f2 assigned to the service area E2, and then the local oscillator of the high frequency unit 15 receives the radio channel frequency f2. A local transmission frequency corresponding to the radio channel frequency f2 is set. Then, when the area number notification packet transmitted from the gateway station R2 by the radio channel frequency f2 is received, the reception level, the interference level, and the bit are the same as when the area number notification packet from the gateway station R1 is received. It is determined whether or not the error rate or the like satisfies a predetermined threshold value, and if it is determined that the error rate is satisfied, the "service area number # E1" and the source of the sender inserted in the received packet are determined. Enter the gateway station address # R1
With information indicating the reception quality such as the above reception level,
It is stored in the corresponding area of the list memory provided in the service area control unit 31.

Thereafter, similarly, the radio communication terminal M1 receives all the remaining service areas E3, E4, ..., E in the system.
Area number notification packets are sequentially received for each of the n radio channel frequencies f3, f4, ..., F1.
Then, when the area number notification packet is received with satisfactory quality, the "service area number" of the received packet and the gateway address of the transmission source are stored in the list memory in the service area control unit 31 together with the information indicating the reception quality. Remember. If the area number notification packet cannot be received with a satisfactory quality, the information indicating non-reception is stored in the corresponding area of the list memory. FIG. 5 shows an example of the list thus created.

Now, all service areas E
When the creation of the list for 1 to En is completed, the control unit 30 of the wireless communication terminal M1 proceeds to step 7b, and selects the service area to which it belongs. That is, based on the above list, one service area having the best reception quality is selected, and information indicating that it belongs to the area corresponding to the selected service area in the list memory is written. For example, if the reception quality in the service area E1 is the best, "O" indicating that the user belongs to the area corresponding to the service area E1 is stored as shown in FIG.

Further, as described above, the service area E to which the user belongs belongs
When 1 is selected, the wireless communication terminal M1 proceeds to step 7c and determines whether or not the next candidate of the service area that can belong to the list is registered here. And
If there is a service area to which the user can belong as in the case shown in FIG. 5, the process proceeds to step 7d to create a location registration packet. This location registration packet contains the destination station address D according to the previously selected service area E1.
The address # R1 of the gateway station R1 corresponding to this service area E1 is inserted into A, the own address # M1 is inserted into the source address SA, and it is shown that it is a position registration packet in the area of packet type TYP. 1
0 ”is inserted. Then, the wireless communication terminal M1 wirelessly transmits the created position registration packet to the gateway station R1 as shown in FIG. 4. If there is no next candidate for the service area to which it can belong. , The service area list is repeatedly created until the next candidate is found.

Upon receiving the position registration packet, the gateway station R1 extracts the address # M1 of the wireless communication terminal M1 inserted in the source address SA from the received position registration packet, and extracts this terminal address # M1. Register in the address management table.

Similarly, also in the other wireless communication terminals M2 to Mm, a list of service areas to which the wireless communication terminals M2 to Mm can belong is created in accordance with the same procedure, and the best service area is selected from this list. Then, the selected service area is registered in the list memory of its own wireless communication terminal, and is notified to the gateway station by the position registration packet and registered in the address management table.

As an example of the registration result, FIG. 6 shows that the wireless communication terminals M1 to M5 exist in the service areas E1 and E2, and the wireless communication terminals M1 to M5 belong to the gateway stations R1 and R2. It shows the case of registration in the table.

Next, an autonomous switching operation of the belonging service area by each of the wireless communication terminals M1 to Mm will be described. When the respective wireless communication terminals M1 to Mm have completed the registration of their own area as described above, the wireless communication terminals M1 to Mm transmit information packets at any time in response to the request, and then perform step 7e.
The state of the service area to which it belongs is monitored from 7h.

That is, in the access protocol based on the CSMA / CD method, when a collision occurs with a packet transmitted by another wireless communication terminal when a certain wireless communication terminal transmits a packet, the time at which this collision occurrence is detected. Then, both wireless communication terminals stop transmitting packets. The wireless communication terminal that stopped the packet transmission retransmits the packet after a random time elapses due to the backoff process, but if the traffic in the service area is extremely high, collisions will be repeated many times and the final In some cases, resending is also canceled. Therefore, the wireless communication terminals M1 to Mm determine in step 7e whether or not the number of collisions of the transmission packets per unit time is equal to or more than a predetermined threshold value.

Further, when the wireless communication terminal moves during transmission and the distance between the wireless communication terminal and the communication partner terminal greatly increases, or when the transmission quality deteriorates due to interference from other wireless communication terminals,
The bit error of the received bit string increases. When this bit error exceeds the error correction capability, the received packet cannot be reproduced and the packet is discarded. Especially wireless LA
In N, the frequency repetition distance may not be sufficient due to the restrictions of the building, or there may be other wireless communication terminals that use the same frequency in adjacent service areas, so the above-mentioned problems often occur. . The above problem also occurs when the packet reception level is greatly reduced due to the effects of fading or the like. Therefore, the wireless communication terminals M1 to Mm determine in step 7f whether or not the bit error rate (BER) has increased above a predetermined threshold value.

Further, even when the traffic is low and the transmission quality is good, the gateway stations R1 to R1 of the service area to which the user belongs belong
When the Rn has a failure or the transmission / reception operation is stopped due to maintenance work or the like, the area number notification packet which should be received periodically cannot be received. Therefore, the wireless communication terminals M1 to Mm detect the failure of the gateway stations R1 to Rn by monitoring whether or not the area number notification packet is received in step 7g.

Also, when the wireless communication terminals M1 to Mm move to other service areas across the service areas, normal reception of packets cannot be performed. Therefore, the wireless communication terminals M1 to Mm determine in step 7h whether or not they have moved to another service area based on the reception level of the carrier.

If any of these steps 7e to 7h is determined to be YES, the wireless communication terminal M1
~ Mm returns to step 7b and selects the next candidate of the service area to which it can belong based on the registered contents of its own service area list. Then, while registering "○" indicating that it belongs to the area corresponding to the next candidate of the above service area in its own list memory, "○" is registered from the area corresponding to the service area to which it belongs until now.
To erase. In addition, the location registration packet is transmitted to the gateway station of the service area which is a new affiliation destination, thereby registering its own terminal address in the address management table of the gateway station.

For example, in the state shown in FIG. 6, the wireless communication terminal M4 belonging to the service area E1 is
Detects an increase in traffic or deterioration in transmission quality,
It is assumed that the switching process to the service area E2 which is the next candidate is performed. Then, in the gateway station R2 of the service area E2 of the new affiliation, the terminal address # M4 of the wireless communication terminal M4 is newly registered in the address management table, while in the gateway station R1 of the service area E1 of the old affiliation destination. The terminal address # M4 of the wireless communication terminal M4 is deleted from the address management table. In this way, the switching of the service area to which the wireless communication terminals M1 to Mm are autonomously controlled is completed.

Note that it is necessary to delete the terminal address registered in the gateway station of the service area of the old affiliation as the affiliation service area is switched. This old terminal address can be deleted by exchanging information between the gateway stations via the wired transmission line WL, for example. As another means, "Life Time" that indicates the valid registration time of the terminal address is added to the data area of the location registration packet and transmitted, and this "Life Time" is registered in the gateway address management table together with the terminal address. I'll do it. Then, it is possible to use a means for automatically deleting the registration of the terminal address when the time corresponding to this "Life Time" has elapsed.

Further, when the service area to which the user belongs is switched due to the movement between the service areas, the wireless communication terminals M1 to Mm replay the service area list in the same manner as when the power is turned on.

As described above, in this embodiment, in each of the wireless communication terminals M1 to Mm, a list of service areas to which the wireless communication terminals M1 to Mm can belong is created when the power is turned on and when the service areas are moved to each other. It is stored in memory, and the state of the service area to which it belongs is determined by monitoring the packet collision rate and bit error rate.
When it is determined that the transmission quality cannot be maintained, the service area to which it belongs is switched to the next candidate based on the above list.

Therefore, each wireless communication terminal M1 to Mm always uses the best service area within a possible range without knowing in advance the traffic conditions of its own system and the conditions of neighboring frequency sharing systems. As a result, high quality data transmission can be performed. Further, since the wireless communication terminals M1 to Mm autonomously select the service areas E1 to En, the situation of each service area is centrally managed by a base station or the like, and the belonging of each wireless communication terminal is managed and controlled. Compared with such a system, the system configuration and control can be simplified, and as a result, an inexpensive system as a whole can be provided.

Next, another embodiment of the present invention will be described. In this embodiment, when creating a list of service areas to which the wireless communication terminals M1 to Mm can belong, all the gateway stations R1.
~ Rn is requested to transmit the area number notification packet, and a list is created for the service area of the gateway station that responded.

FIG. 8 is a timing chart showing the operation. In the figure, the wireless communication terminal M1 sequentially switches the wireless channel frequencies like f1, f2, ... At regular time intervals, and transmits an area number request packet each time one wireless channel frequency is set. . On the other hand, when the area number request packet arrives via each of the gateway stations R1 to Rn via the wireless channel frequencies f1, f2, ... To do. When the area number notification packet is received from the gateway station within a fixed time including the transmission period of the area number request packet, the wireless communication terminal M1 displays a list related to the corresponding service area based on the area number notification packet. create.

As described above, in this embodiment, the area number request packet is transmitted from the wireless communication terminals M1 to Mm, and the gateway stations R1 to Rn transmit the area number notification packet in response to this. The gateway stations R1 to Rn do not need to periodically transmit the area number notification packet, which can reduce the traffic in the service area.

The present invention is not limited to the above embodiments. For example, the gateway stations in each service area may be synchronized with each other, and the transmission timings of the area number notification packets may be sequentially shifted from the radio channel frequencies f1 to fn-1. In this case, the wireless communication terminal may sequentially switch the reception local oscillation frequency from the wireless channel frequency f1 to fn−1, and the timeout time when the area number notification packet cannot be received can be shortened. The time for creating a list of service areas can be shortened.

Further, in each of the above embodiments, a list of service areas to which the user can belong is created, and when the state of the service area to which the user belongs cannot be satisfied, the next candidate of the service area is selected based on this list. I switched the service area to which I belong, but without making a list,
It may be configured to switch the radio channel frequency to the frequency of the adjacent service area on a trial basis.

Further, in the above embodiment, the list is created and changed when the power of the wireless communication terminal is turned on and when the wireless communication terminal is moved across the service area. In addition to this, all the services stored as a candidate list are added. When the state of the area does not satisfy the predetermined state, the operation of changing the candidate list of service areas to which the user can belong may be performed.

In addition, the monitoring target for determining the status of the service area, the list creation control procedure of the service area to which it can belong and its control content, the list creation timing, the service area switching control procedure and control content, the wireless communication terminal The circuit configuration, the service area layout configuration, and the like can be variously modified and implemented without departing from the scope of the present invention.

[0069]

As described in detail above, according to the present invention, a plurality of service areas are arranged such that at least some of the areas overlap each other, and a plurality of wireless communication terminals are located in these service areas. In a wireless communication system having a function of performing data transmission via a wireless channel, a wireless communication terminal is provided with a state determination means and a service area selection means, and the state determination means causes each of The state of the service area is determined, the candidate of the service area to which the service area can belong is determined based on the determination result, the candidate list is stored, and the plurality of service areas to which the service area should belong are stored based on the stored candidate list. The service areas are selected from alternatives.

Therefore, according to the present invention, it is possible to provide a wireless communication system and its wireless communication terminal capable of smoothly and reliably selecting the service area to which the user belongs.

On the other hand, in another invention, there are a plurality of service areas arranged such that at least some of the areas overlap each other, and these service areas are respectively connected to a wireless communication terminal via a wireless channel. In addition to the fixed installation of the gateway stations, these gateway stations are connected via a wired transmission line, and multiple wireless communication terminals located in different service areas can transmit data via the gateway station and the wired transmission line. In a wireless communication system having a function to perform, the wireless communication terminal includes a belonging candidate determining unit, a state determining unit, and a service area selecting unit. Then, the affiliation candidate determination means determines the candidate of the service area to which the service area can belong based on the reception state of the control packet including the service area identification information periodically transmitted from the gateway station for each of the service areas. The state determining means determines whether or not the state of the service area to which the user belongs is in a satisfactory state. Then, when it is determined by this state determination means that the service area to which it belongs is not in a satisfactory state, the service area selection means selects an appropriate service area from the candidates decided by the belonging candidate decision means. I am trying to choose. Therefore, according to the present invention, it is possible to provide a wireless communication system and its wireless communication terminal capable of smoothly and reliably selecting the service area to which the user belongs.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a wireless LAN system according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a wireless communication terminal in the system shown in FIG.

FIG. 3 is a diagram showing a frame structure of a packet.

FIG. 4 is a timing chart for explaining a list creation means of a service area that can belong to the system shown in FIG.

FIG. 5 is a diagram showing an example of a list of available service areas.

FIG. 6 is a diagram showing an example of a configuration of an address management table in a gateway station.

7 is a flowchart showing the control procedure and control contents of the service area list creating means and the service area switching means in the wireless communication terminal shown in FIG.

FIG. 8 is a timing diagram for explaining a list of means for assignable service areas according to another embodiment of the present invention.

[Explanation of symbols]

E1-En ... Service area R1-Rn ... Kanmon station M1 to Mm ... wireless communication terminals WL ... Wired transmission line 11 ... Digital interface 12 ... Packet generator 13 ... Error correction code part 14 ... Modulator 15 ... Radio frequency (RF) section 16 ... Antenna 17 ... Demodulation unit 18 ... Error correction decoding / detection unit 19 ... Packet decomposition unit 21 ... Reception level (Rx level) measurement unit 22 ... Carrier detection unit 23 ... Collision detector 30 ... Control unit 31 ... Service area control unit

Claims (6)

(57) [Claims] 1. A function having a plurality of service areas arranged such that at least a part of the areas overlap each other, and a plurality of wireless communication terminals transmitting data via a wireless channel in these service areas. In the wireless communication system including the wireless communication terminal, the wireless communication terminal determines the state of each service area in response to power-on of the wireless communication terminal, and determines a candidate service area that can belong to based on the determination result. A state determining means for storing the candidate list, and a service area for selectively selecting a service area to belong to from the plurality of service areas based on the candidate list stored by the state determining means. A wireless communication system comprising: selecting means. 2. The state determination means performs an operation of changing the candidate list of service areas to which the user can belong when the states of all the service areas stored as the candidate list do not satisfy a predetermined state. The wireless communication system according to claim 1, which is performed. 3. A plurality of service areas arranged such that at least a part of the areas overlap each other, and a gateway station connected to a wireless communication terminal via a wireless channel is fixed to each of these service areas. As well as installing, connect these gateway stations via a wired transmission line,
In a wireless communication system having a function in which a plurality of wireless communication terminals located in different service areas perform data transmission via the gateway station and a wired transmission path, the wireless communication terminal is a gateway station for each service area. Based on the reception status of the control packet including the service area identification information, which is periodically transmitted from the Status determining means for determining whether or not the service area to which the service area belongs is not satisfied by the status determining means, and the candidate determined by the affiliation candidate determining means. And a service area selecting means for selecting an appropriate service area from among the wireless communication systems. 4. A function having a plurality of service areas arranged such that at least a part of the areas overlap each other, and a plurality of wireless communication terminals transmitting data through wireless channels in these service areas. In the wireless communication terminal used in the wireless communication system including, the state of each service area is determined according to the power-on of its own terminal, and the candidate of the service area to which it can belong is determined based on the determination result. State determining means for storing the candidate list, and a service for selectively selecting a service area to which the user belongs from the plurality of service areas based on the candidate list stored by the state determining means. A wireless communication terminal comprising area selecting means. 5. The status determining means selects a service area candidate list to which the terminal can belong when the status of all service areas stored as a candidate list does not satisfy a predetermined status. The wireless communication terminal according to claim 4, wherein the wireless communication terminal performs a changing operation. 6. A plurality of service areas are arranged such that at least a part of the areas overlap each other, and a gateway station connected to a wireless communication terminal via a wireless channel is fixed to each of these service areas. As well as installing, connect these gateway stations via a wired transmission line,
In the wireless communication terminal used in a wireless communication system having a function in which a plurality of wireless communication terminals located in different service areas perform data transmission via the gateway station and a wired transmission path, Membership deciding means for deciding a candidate service area that can belong to, based on the reception status of control packets including service area identification information that are periodically transmitted from the gateway station, and the status of the service area to which it belongs. Is determined by the state candidate determining means, and when the state determining means determines that the service area to which the user belongs does not satisfy the state, the belonging candidate determining means determines. And a service area selecting means for selecting an appropriate service area from the candidates. .