JP2846039B2 - Communication network - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication network including a plurality of wireless terminals and a plurality of wireless base stations interconnected by wires that accommodate the wireless terminals. , A wireless channel allocation method.

[Prior Art] In mobile communication, available frequency resources are limited, and thus effective use of frequencies is an important issue. In a mobile phone system that is a typical example of mobile communication,
Communication is performed in accordance with the multi-channel access method based on the small zone method to achieve effective use of the frequency.

The channel allocation method of the multi-channel access communication system is roughly classified into a fixed channel allocation method and a dynamic channel method.

When the peak time of the traffic volume of each zone varies, it is generally said that the dynamic channel allocation improves the allocation efficiency. However, the dynamic channel method is complicated in control and requires time to search for an empty channel. Therefore, it takes time to determine a channel to be allocated, and the efficiency may be lower than in fixed allocation. For this reason, a channel allocation method with relatively simple control and high allocation efficiency has been studied.

[Problems to be Solved by the Invention] In any of the fixed channel allocation method and the dynamic channel method, based on the premise that zones are appropriately allocated and the positional relationship of each radio base station is clearly defined. I have.

However, when a two-layered network consisting of a wired upper network and a wireless lower network is applied to a network that covers the premises such as a LAN, the attenuation of radio waves is not uniform due to walls, etc. The positional relationship of the zones required by the channel arrangement method cannot be defined.

Therefore, there is a need for an improved dynamic channel allocation algorithm that allows each wireless base station to uniquely determine an adjacent wireless base station and determine a channel to be allocated in a short time with relatively simple control.

The present invention has been made in view of the above points,
An object of the present invention is to provide a communication network capable of realizing an appropriate channel arrangement even if an accommodation zone of a radio base station cannot be accurately defined.

[Means for Solving the Problems] In order to solve the problems, the present invention includes a plurality of wireless terminals, and a plurality of wireless base stations accommodating the wireless terminals and interconnected by wires. In addition, a communication network that applies a multi-channel access method to a wireless channel access method adopts the following method relating to channel arrangement.

That is, a wired network portion having a group broadcast function is applied. Also, when each adjacent base station receives a communication request from a wireless terminal that is not accommodated by itself, it recognizes the identification information of the wireless base station included in the communication request and detects the adjacent wireless base station. When the source of the assigned channel information transmitted by the group broadcast function is an adjacent wireless base station, the assigned channel information is stored.

The allocated channel information of the adjacent radio base station stored in this way can be used in various processes. However, when each radio base station needs to allocate a channel, Most used.

[Operation] It is not preferable that the entire upper network manages the assigned channel information from the viewpoint of the load on the network. Therefore, in the present invention, the management is performed by the wireless base station.

In this case, if each radio base station manages the channel information allocated by all the other radio base stations, there is no difference in effect from the management by the upper network. Therefore, it has been decided to manage the assigned channel information of the adjacent base station where the communication disturbance is a problem.

Receiving a communication request for another wireless base station means that there is a risk of communication interference. Therefore, a wireless base station that is not addressed to itself and is a destination of a received communication request is detected as an adjacent wireless base station.

According to this method, adjacent wireless base stations are not always unique, and transmission and reception of assigned channel information becomes a problem. Therefore, each wireless base station transmits the assigned channel information using the group broadcast function of the wired network portion, and stores the information when the assigned channel information is given from the wireless base station that has determined that the wireless base station is an adjacent station. I decided that.

[Embodiment] Hereinafter, the present invention is applied to a local area network (LAN).
An embodiment applied to the invention will be described in detail with reference to the drawings.

(A) Overall Configuration of Local Area Network First, the overall configuration of the LAN of this embodiment will be described with reference to FIG.

FIG. 2 shows this overall configuration. In FIG. 2, this LAN 1 is composed of an upper network using a wired communication medium and a lower network using a wireless communication.
It has a layered structure.

The upper network is a common bus 2 and the common bus 2
And a plurality of terminals 4 and at least one host computer 5 connected to each other via an input / output station 3. Also, a plurality of wireless base stations 6 serving as gateways for connecting the upper network and the lower network are connected to the input / output station 3 on the common bus 2.
Connected through.

The lower station includes the wireless base station 6 described above and a plurality of wireless terminals 7 that can execute wireless communication with the wireless base station 6. The zone 8 in which each wireless base station 6 can accommodate the wireless terminal 7 has a predetermined range (not a strict range).
Stipulated.

The reason why the plurality of wireless base stations 6 are provided is that all wireless terminals 7 must have a communication range that covers the entire network in a single zone configuration. This is because a large transmission output increases and the device configuration becomes large, and only one wireless terminal can use the same frequency at the same time.

As described above, since the communication medium of the upper network is wired and the communication medium of the lower network is wireless, the protocol control configuration of each component of the lower network is as shown in FIG. That is, the wireless terminal 7
Has a wireless protocol control unit 7a for realizing wireless communication, and the wireless base station 6 has a wired protocol control unit 6b for realizing wired communication in addition to the wireless protocol control unit 6a for realizing wireless communication. .

According to the network having such a two-layer structure, communication between the terminals 4 on the upper network can be executed, communication between the wireless terminals 7 using the upper network can be executed, and furthermore, wireless communication can be performed via the upper network. Communication between the terminal 7 and the terminal 4 can be executed. Communication may be performed between the wireless terminal 7 and the wireless base station 6 in order to determine the wireless base station 6 that accommodates the wireless terminal 7.

The network has a two-layer structure because the degree of freedom of the network layout can be increased as compared with a network using only a wire.

In view of the difference from the existing two-layer network, the problem of line quality and the difficulty of realizing a practical network due to the presence of an overheader at the start and end of communication in a wireless network are considered. In view of this, a new accommodation protocol, a communication protocol, and a channel allocation protocol for the wireless terminal 7, which will be described later, are adopted to realize a two-layer LAN.

Note that the higher-level network of this embodiment needs to have a group broadcast function, as described later.

(B) Accommodation of Wireless Terminal 7 in Wireless Base Station 6 Next, a method of accommodating the wireless terminal 7 in the wireless base station 6 will be described. Here, the logical connection operation of the lower network is described as accommodating the wireless terminal in the wireless base station.

 FIG. 4 is an explanatory diagram showing a method of accommodating a wireless terminal.

In this embodiment, the radio base station 6 is determined by the radio base station 6 instead of the radio terminal 7.

First, the wireless terminal 7A sends out an accommodation request packet to which its own identification number is added after the power is turned on (procedure 100). Upon receiving the accommodation request packet from the wireless terminal 7A, the wireless base station responds to the wireless terminal 7A by adding its own identification number (procedure 101). In the case of this embodiment, the wireless terminal and the accommodation destination radio base station do not correspond one-to-one, and all the radio base stations 6A, 6A, and 6B that have received the accommodation request packet are
6B and 6C respond to the wireless terminal 7A. In addition, although the zone is formed around the wireless base station, the zones are overlapped to some extent so that communication is reliably performed even if there is fading or noise, so that a plurality of wireless base stations 6A to 6C An accommodation request packet may be received.

The wireless terminal 7A identifies, using the identification number, the wireless base station that has transmitted the first response correctly received among the received responses, for example, the wireless base station 6A, and outputs the accommodation request packet again (step 102). . Only the designated wireless base station 6A responds, and the accommodation is completed (step 103).

In addition, for such communication for accommodation, for example, one communication control channel prepared separately from the data communication channel is used.

By the way, the wireless terminal 7 is moved due to a layout change of the office to which the LAN is applied, and the own terminal 7 is moved.
May be out of the communicable range of the wireless base station 6 in which is stored. At this time, a re-accommodation operation is performed. The reaccommodation operation is executed when a retransmission request is received from the radio base station 6 accommodated up to now at a certain rate or more. The re-accommodation operation is the same as the accommodating operation except that a re-accommodation request packet is transmitted instead of the accommodating request packet, and is accommodated in another radio base station.

(C) Communication Method / Communication Protocol Next, a communication method and a communication protocol will be described.

In the following, different from the general LAN communication, the uplink and downlink communication method and communication protocol between the wireless terminal 7 and the wireless base station 6, the communication method and communication protocol between the wireless base stations 6, A communication method and a communication protocol from the terminal 4 on the upper network to the wireless base station 6 will be sequentially described.

Here, a plurality of frequency channels are prepared for a lower network using wireless as a communication medium, one of which is allocated to a communication control channel and the other is allocated to a data communication channel. A multi-channel access scheme is applied in consideration of effective use of frequency and partial overlap of zones.

FIG. 5 is an explanatory diagram showing an uplink communication procedure from a wireless terminal to a wireless base station.

When a communication request is issued, the wireless terminal 7A sends out a communication channel assignment request packet in which an identification number for itself is added to a communication control channel (up) (procedure 200).

This communication assignment request may be received by a plurality of wireless base stations 6A to 6C. Only the wireless base station 6A accommodating the wireless terminal 7A that sent the request determines the data channel to be allocated and returns a response to the wireless terminal 7A (procedure 20).
1). Other wireless base stations 6B and 6C that do not accommodate the communication base station ignore the communication channel assignment request packet. A method for determining a channel for communicating data will be described later.

Upon receiving the response, the wireless terminal 7A transmits data to the wireless base station 6A using the assigned data channel (Step 202).

The wireless base station 6A that has received the transmission data determines whether the destination of the data is another wireless terminal accommodated by itself, and whether the destination is the terminal 4 or the host computer 5 on the upper network. Determine.

If the destination of the data is another wireless terminal accommodated by itself, a communication procedure for a downlink of a wireless channel described later (see procedures 205 and 206 in FIG. 6) is executed.

If the terminal 4 or the host computer 5 is on the upper network, the data is transferred to the destination terminal 4 or the host computer 5 by a transfer method similar to the conventional method.

If it is determined that the destination is neither the terminal 4 or the host computer 5 on the upper network nor any other wireless terminal accommodated by itself, the group broadcast function (see FIG. 6) of the upper network is used. , And transmits the identification number and data of the transmission source wireless terminal as one packet.

The reason why the group broadcast function is used for transmission is that the wireless base station 6 knows the wireless terminal that it owns, but the other wireless base station accommodates which wireless terminal This is because they do not have all the information about what they are doing.
The destination of the data transmitted by the group broadcast function is directed to the radio terminal accommodated therein, and the radio base station executes the below-described radio channel communication procedure (see FIG. 6).

FIG. 6 is an explanatory diagram showing a communication procedure between radio base stations and a downlink communication procedure from a radio terminal to a radio base station. This figure shows a case where the data received by the radio base station 6A is destined for the radio terminal 7B accommodated in the radio base station 6B.

The wireless base station 6A transmits the identification number and the data of the destination wireless terminal 7B as one packet to all the other wireless base stations 6B and 6C by the group broadcast function (procedure 20).
3).

The wireless base station 6C that does not accommodate the destination wireless terminal 7B does not perform any operation even when receiving this packet. On the other hand, the wireless base station 6B accommodating the wireless terminal 7B first returns an acknowledgment to the wireless base station 6A to which the packet is to be transmitted (step 204).

Thereafter, the radio base station 6B determines a channel to be allocated as described below, and notifies the channel information determined using the communication control channel to the wireless terminal 7B that is the destination of the packet. The packet is transferred using the data channel determined in this way (procedures 205 and 206).

The communication from the wireless terminal to the wireless base station, the communication from the wireless base station to another wireless base station, and the communication from the wireless base station to the wireless terminal have been described above. Communication to the station will be described.
Also in this case, as in the communication between the wireless base stations, the terminal 4
Is the group broadcast function for all radio base stations 6A, 6A
The identification number and data of the destination wireless terminal 7B are transmitted as one packet to B and 6C. The use of the group broadcast function is similar to the communication between wireless base stations.

(D) Determination of Communication Channel In this embodiment, as described above, a multi-channel access method is adopted in consideration of effective use of frequency.
Therefore, as described in the section on the communication method and the communication protocol, the channel must be determined in consideration of the channel already used for data communication of the lower network. That is, the arrangement of channels becomes a problem.

The channel allocation method of the communication network is roughly classified into a fixed channel allocation method and a dynamic channel method. However, since these have problems as described above, a new channel allocation method is adopted.

The radio base station 6 determines the channel as described above in consideration of simplification of the control configuration and reduction of the load on the upper network.

Hereinafter, a method for determining a channel will be described in the order of determination of an adjacent base station, creation of a channel assignment table, and a channel allocation algorithm.

(D-1) Determination of adjacent radio base station By knowing which radio base station is adjacent to which radio base station, the channel can be used effectively. That is, in order to determine a channel efficiently, it is necessary to know adjacent wireless base stations.

Position information of a wireless base station, which wireless base station is adjacent to which wireless base station, is indispensable data for a channel allocation method. If the location information has a network (for example, host computer 5) in advance, the load on the network increases and flexibility is impaired.
Since it is difficult to increase the number of radio base stations, each radio base station can dynamically acquire position information. First, a method for acquiring position information of an adjacent wireless base station will be described.

When an error in a communication line is random, a longer data requires a lower error rate in the communication line. In general, the shorter the communication distance is, the lower the error rate is. Therefore, the communication request packet reaches more accurately than the data packet. Accordingly, a communication request packet from a wireless terminal in a wider range than the zone 8 of each wireless base station is received by the wireless base station.

As described above, in the communication request packet of the wireless terminal,
The number of the accommodating wireless base station and the number of the wireless terminal are inserted and transmitted simultaneously.

Therefore, an adjacent wireless base station is detected using the communication request packet.

 FIG. 1 is a flowchart of such detection processing.

First, it is determined whether or not the received packet is a communication request packet (step 300). If you get a negative result,
The process returns to the main routine (for example, a housing operation is performed).

On the other hand, if the packet is a communication request packet, it is further determined whether the packet is from a wireless terminal accommodated therein (step 301). If a positive result is obtained also in this determination, the communication processing shown in FIG. 5 is executed (step 302).

If the wireless base station obtains a negative result because the received packet is not from the wireless terminal (wireless terminal in the zone) that the wireless base station accommodates, the wireless base station accommodates the communication request packet from outside the zone. Are defined as adjacent wireless base stations (step 303). Then, the number of the adjacent wireless base station received in the past fixed time is stored as an adjacent wireless base station list (step 304).

(D-2) Creation of Channel Assignment Table Next, a channel assignment table and a creation method thereof will be described.

In the dynamic channel allocation, when determining a channel to be allocated, the channel usage status of another wireless base station is required. Due to this information exchange, there is a disadvantage that the load on the upper network increases. In order to minimize the traffic and buffer area on the network,
The amount of information held by the radio base station should be kept to a minimum. Therefore, each wireless base station stores only the data of the assigned channel information of the adjacent wireless base stations, which may cause communication interference with each other.

Each of the wireless base stations is the neighbor list ｛N determined above.
1, N2,..., Ni｝, to the adjacent radio base station, which channel is currently being used by the adjacent radio base station by the group broadcast function on the higher-level network. By updating the channel usage status, a channel assignment table of the adjacent radio base station is created in the own station.

FIG. 7 is a flowchart of such processing. First,
It is determined whether or not the data provided by the group broadcast function is assigned channel information (step 400). If a negative result is obtained, another process (for example, a process of downlink communication to the wireless terminal 7 shown in FIG. 6) is executed (step 40).
1).

If a positive result is obtained from the assigned channel information, it is determined whether or not the transmission source is an adjacent wireless base station (step 402). If a negative result is obtained, the process ends without any processing, while if a positive result is obtained, the contents of the channel assignment table are updated accordingly (step
403).

Note that the wireless base station also stores its own assigned channel information in the table.

The channel allocation table also manages how many times a communication request packet has been received from a wireless terminal accommodated in the adjacent wireless base station in the past. This value is a guide to know how much interference will occur when using the same frequency as the adjacent radio base station,
Hereinafter, it is referred to as area multiplicity.

The radio base station determines a channel to be allocated to the radio terminal, and before using the radio terminal to notify the radio terminal and after releasing the allocated channel, uses the group broadcast function of the upper network to use the channel for each radio base station. Notify changes in circumstances. When each wireless base station receives the change in the channel usage status of the adjacent wireless base station through the upper network, it updates the channel usage status of its own channel assignment table based on the data. Since this method does not require information exchange of the upper network at the time of channel arrangement, the time required at the time of channel arrangement can be reduced.

FIG. 8 is an explanatory diagram of the channel assignment table that is continuously updated in this way.

FIG. 8 (B) shows a case where the wireless base station 61 houses the wireless terminal 71, the wireless base station 62 houses the wireless terminals 72 and 73, and the wireless base station 63 houses the wireless terminals 74 and 75. Fig. 8 (A)
In the accommodation relationship state as shown in, each radio base station 61,
The main body of the assignment table for the first channel, second channel,..., Fifth channel.

The radio base station 61, as shown in the area multiplicity column,
Since communication request packets have been received from the wireless terminals 72 and 73 accommodated in the wireless base station 62, the wireless base station 62 is identified as an adjacent wireless base station, and the wireless base station 62 The assigned channel transmitted by the station 62 (second
The channel (the fourth channel) is also stored in the channel use status column together with the channel (first channel) information assigned by itself.

The radio base station 62, as shown in the area multiplicity column,
Since it has not received a communication request packet from a wireless terminal accommodated in the other wireless base stations 61, 63,..., Only the channel (second channel and fourth channel) information allocated by itself is included in the channel usage status column. Has accumulated.

The radio base station 63, as shown in the area multiplicity column,
Since a communication request packet has been received from the wireless terminal 75 accommodated in the wireless base station 64, the wireless base station 64 is determined as an adjacent wireless base station, and the wireless base station 65 is The channel (fifth channel) transmitted by is also stored in the channel usage column together with the channel (third channel) information allocated by itself.

As described above, each radio base station accumulates only the channel allocated by itself and the channel information allocated by the adjacent radio base station, and executes the channel allocation control described later.

Since a channel is allocated independently of a radio base station that is so distant that a communication request packet is not received, effective use of frequency is achieved, and the capacity of a buffer memory for storing such a table is small. I can do it.

(D-3) Channel Allocation Algorithm Next, a channel allocation algorithm for determining a channel will be described.

FIG. 9 is a flowchart of such a channel arrangement process.

Upon receiving the communication request packet from the wireless terminal accommodated in the wireless base station 6, the wireless base station 6 executes the processing shown in FIG. Is determined as a channel to be assigned, which channel is not considered to cause interference.

In FIG. 9, first, based on the contents of the channel assignment table, it is determined whether or not there is a vacant channel among the channels to which it is assigned (step 500).

If there is an unused channel that is not used by the adjacent wireless base station and the own station, an allocated channel is determined at random from those unused channels (step 501). A channel (a channel assigned by a radio base station which is considered to be the farthest one of the stations) is selected (step 502).

After determining the channel, before notifying the radio terminal 7 of the determined channel, it is checked whether or not a notification to use this channel has been received from another adjacent radio base station. 7 (Step 50
3, 504).

If the use notification has been received from the adjacent wireless base station,
Redo the decision process.

Thereafter, the assigned channel information is notified to all the other wireless base stations using the group broadcast function (step 50).
Five).

Similarly, at the time of packet communication from the wireless base station to the wireless terminal, after determining the channel to be assigned from the table, the wireless terminal is called through the control channel and the assigned channel is notified to other wireless base stations.

(E) Effects of Embodiment According to the channel arrangement method applied in the above-described embodiment, the following effects are obtained.

Since the assigned channel information is exchanged in advance, a channel search in wireless communication can be performed in a short time.

Since there is a wired network between base stations, it is possible to exchange information for avoiding collision on the wired network (use information of a communication control channel, which is allocated channel information, etc.), and reduce communication collision. it can.

Since the base station manages the channel, the existing LA
The work when adding a wireless base station to N becomes easy. It is not necessary to change the configuration relating to the channel arrangement for the entire network.

Because it is a dynamic multi-channel communication system that adopts the above-mentioned channel allocation method, traffic density changes due to rearrangement such as office,
Suitable under conditions where the size of the network can be large.

(F) Other Embodiments Various types of high-order networks can be applied as long as they have a group broadcast function. That is,
CSMA / CD, token passing bus, token passing ring, broadband bus method, etc. can be applied. Further, the upper network may not have a terminal.

The channel arrangement method and the like can be applied not only to LANs but also to other two-layer networks.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a communication network capable of realizing an appropriate channel arrangement even if an accommodation zone of a wireless base station cannot be accurately defined.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a process of determining an adjacent wireless base station in a LAN according to an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing a protocol control configuration, FIG. 4 is an explanatory diagram of a method for accommodating a wireless terminal, and FIG. 5 is an explanatory diagram of a communication method from a wireless terminal to a wireless base station. FIG. 6 is an explanatory diagram of a communication method from a radio base station to a radio terminal accommodated in another radio base station, FIG. 7 is a flowchart of a process of creating a channel assignment table,
FIG. 8 is an explanatory diagram of a channel assignment table, and FIG. 9 is a flowchart of an assignment channel determination process. 1 ... LAN, 2 ... common bus, 4 ... terminal on upper network, 5 ... host computer, 6 ... wireless base station, 7 ... wireless terminal.

Claims (2)

(57) [Claims] 1. A multi-channel access system comprising a plurality of radio terminals and a plurality of radio base stations accommodating the radio terminals and interconnected by wires, and applying a multi-channel access system to a radio channel access system. In a communication network that has a group broadcast function applied to the wired network part, each wireless base station receives a communication request from a wireless terminal that is not accommodated by itself, and Recognizes the identification information of the current wireless base station, detects it as an adjacent wireless base station, and stores the assigned channel information when the source of the assigned channel information sent by the group broadcast function is the adjacent wireless base station. A communication network, characterized in that: 2. The radio base station according to claim 1, wherein when it is necessary to allocate a channel, the radio base station determines a channel to be allocated based on channel information already allocated by the radio base station itself and an adjacent radio base station. Claim 1.
A communication network according to.