JPH03250821A - Communication network - Google Patents

Abstract

PURPOSE:To execute proper channel arrangement even when an accommodated zone of a radio base station is not accurately specified by employing a wired network part having a group multiple address function for the network. CONSTITUTION:A wired network part having a group multiple address function is employed for the network. Upon the receipt of a communication request from a radio terminal equipment 7 not accommodated, each radio base station 6 recognizes identification information of the radio base station 6 included in the communication request and detects the station as an adjacent radio base station 6 and stores the allocated channel information when a sender of the allocated channel information sent by the group multiple address function is the adjacent radio base station 6. Thus, even when the accommodated zone of the radio base station is not accurately specified, the proper channel arrangement is executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a communication network including a plurality of wireless terminals and a plurality of wireless base stations that accommodate the wireless terminals and are interconnected by wires, and particularly relates to , relates to a wireless channel allocation method.

[Prior Art] In mobile communications, usable frequency resources are limited, and therefore effective use of frequencies has become an important issue.

In a car telephone system, which is a typical example of mobile communication, effective use of frequencies is achieved by communication based on a multi-channel access method using a small zone method.

Channel allocation methods for multi-channel access communication systems can be broadly classified into fixed channel allocation methods and dynamic channel allocation methods.

When the peak time of traffic volume in each zone varies, dynamic channel allocation is generally said to be more efficient. However, the dynamic channel method requires complicated control and requires time to search for free channels, so it takes time to decide which channel to allocate, and it may be less efficient than fixed allocation. For this reason, research is being conducted on channel placement methods that are relatively easy to control and have high placement efficiency.

[Problems to be Solved by the Invention] Both the fixed channel allocation method and the dynamic channel allocation method are based on the premise that zones are appropriately allocated and the positional relationship of each wireless base station is clearly defined. There is.

However, when a two-layered network consisting of a wired upper network and a wireless lower network is applied to a network such as a LAN that has a communication range within a campus, the attenuation of radio waves is uneven due to walls, etc. It is not possible to specify the positional relationship of zones, which is necessary in the channel arrangement method.

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

The present invention has been made in consideration of the above points, and aims to provide a communication network that can realize appropriate channel allocation even if the accommodation zone of a wireless base station cannot be accurately defined.

``Means for Solving the Problems J'' In order to solve the problems, the present invention provides a system comprising a plurality of wireless terminals and a plurality of wireless base stations accommodating the wireless terminals and interconnected by wires. Furthermore, a communication network that uses a multi-channel access method as its wireless channel access method has decided to adopt the following method for channel allocation.

That is, a wired network with a group broadcasting function was applied. In addition, when each adjacent base station receives a communication request from a wireless terminal that it does not accommodate, it recognizes the identification information of the wireless base station included in the communication request and detects the adjacent wireless base station. However, when the source of the allocated channel information sent by the group broadcast function is an adjacent wireless base station, the allocated channel information is stored.

The allocated channel information of adjacent wireless base stations stored in this way can be used in various processes, but when each wireless base station needs to allocate a channel, it is used when deciding which channel to allocate. most used.

[Operation] It is not preferable for the entire upper network to manage the allocated channel information in terms of network load and the like. Therefore, in the present invention, the wireless base station manages the information.

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

Being able to receive communication requests directed to other radio base stations means that there is a risk of communication interference.

Therefore, we decided to detect the wireless base station that is the destination of the received communication request that is not addressed to itself as an adjacent wireless base station.

With this method, adjacent radio base stations are not always unique, and the exchange of allocated channel information becomes a problem. Therefore, each wireless base station transmits allocated channel information using the group relay function of the wired network part, and stores the information when it is given allocated channel information from a wireless base station that it has determined is an adjacent station. And so.

[Example J Hereinafter, the present invention will be applied to a local area network (LAN).
An embodiment applied to the present 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 in this embodiment will be explained using FIG. 2.

FIG. 2 shows this overall configuration. In FIG. 2, the LAN 1 has a two-layer structure consisting of an upper network that uses wires as a communication medium and a lower network that uses wireless communication.

The upper network consists of a common bus 2, a plurality of terminals 4, and at least one host computer 5, which are connected to the common bus 2 via input/output stations 3. Further, a plurality of wireless base stations 6 that serve as a gateway and connect between an upper network and a lower network are connected to the common bus 2 via input/output stations 3.

The lower station is composed of the above-described wireless base station 6 and a plurality of wireless terminals 7 that can perform wireless communication with the wireless base station 6. A zone 8 in which each wireless base station 6 can accommodate wireless terminals 7 is determined within a predetermined range (not a strict range).

The reason why multiple wireless base stations 6 are provided is that in a single zone configuration, all wireless terminals 7 must have a communication range that covers the entire network. This is because the transmission output increases and the device configuration becomes larger, 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 related to the lower network is as shown in FIG. That is, the wireless terminal 7 includes a wireless protocol control unit 7a for realizing wireless communication, and the wireless base station 6 includes a wired protocol control unit for realizing wired communication in addition to the wireless protocol control unit 6a for realizing wireless communication. 6b.

According to such a two-layer network, it is possible to carry out communication between the terminals 4 on the upper network, it is also possible to carry out communication between the wireless terminals 7 using the upper network, and furthermore, it is possible to carry out communication between the wireless terminals 7 using the upper network. Communication between the wireless terminal 7 and the terminal 4 can be performed via the wireless terminal 7 and the terminal 4. Note that in order to determine the wireless base station 6 that accommodates the wireless terminal 7, communication may be performed between the wireless terminal 7 and the wireless base station 6.

The reason why the network has a two-layer structure is that the degree of freedom in network layout can be increased compared to a wired-only network.

In addition, in view of the differences from existing two-layer networks, and the problem that wireless networks have problems with line quality and the presence of overheads at the start and end of communication, it is difficult to realize a practical network. In view of this, we have decided to adopt new accommodation protocols, communication protocols, and channel arrangement protocols for wireless terminals, which will be described later, to realize a two-layer LAN.

Note that the upper network in this embodiment is required to have a group broadcasting function, as will be described later.

(B) Accommodating the wireless terminal 7 in the wireless base station 6 A method for housing the wireless terminal 7 in the wireless base station 6 will be described below. Note that the logical connection work of the lower-level network is expressed here as accommodating a wireless terminal in a wireless base station.

FIG. 4 is an explanatory diagram showing a method of accommodating wireless terminals. In this embodiment, the wireless base station 6, not the wireless terminal 7, determines the wireless base station to accommodate.

First, after turning on the power, the wireless terminal 7A sends out an accommodation request packet to which its own identification number is added (step 100).

When receiving an accommodation request packet from the wireless terminal 7A, the wireless base station responds to the wireless terminal 7A by adding its own identification number (step 101). In the case of this embodiment, there is not a one-to-one correspondence between the wireless terminal and the accommodation destination wireless base station, and all the wireless base stations 6A, 6B, and 6C that have received the accommodation request packet respond to the wireless terminal 7A. Do the following. Although zoning is performed centering on the wireless base stations, the zones overlap to some extent to ensure communication even in the presence of fading and noise, so multiple wireless base stations 6A to 6C can be used at the same time. Accommodation request packets may be received.

The wireless terminal 7A transmits the first response that was correctly received among the received responses, for example, the wireless base station 6A.
is identified using the identification number, and an accommodation request packet is output again (step 102).

Only the designated wireless base station 6A responds, and accommodation is completed (Step III 103).

Note that for communication for such accommodation, for example, one channel for communication control that is prepared separately from a channel for data communication is used.

By the way, if the wireless terminal 7 is moved due to changes in the layout of the office where the LAN is applied, the own terminal 7
may go out of the communication range of the wireless base station 6 in which the wireless base station 6 is accommodated. At this time, a reaccommodation operation is performed. The reaccommodation operation is executed when retransmission requests are received from the wireless base stations 6 that have been accommodated at a rate exceeding a certain rate. Note that the re-accommodation operation is similar to the accommodation operation except that a re-accommodation request packet is sent instead of the accommodation request packet, and thereby the base station is accommodated in another radio base station.

(C) Communication method/communication protocol Next, a communication method and communication protocol will be explained.

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

Here, for the lower-level network that uses wireless as a communication medium, multiple frequency channels are prepared, one of which is assigned as a communication control channel, and the other channels are assigned as data communication channels, making effective use of frequencies. A multi-channel access method is applied that takes into account partial overlapping 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 generated, the wireless terminal 7A sends out a communication channel allocation request packet in which an identification number for itself is added to the communication control channel (upstream) (step 200).

This communication assignment request may be received by a plurality of wireless base stations 6A to 6C. Decide which data channel to assign only to the wireless base station 6A that accommodates the wireless terminal 7A that sent the request, and send a response back to the wireless terminal 7A (Step 201). 6
C ignores the communication channel allocation request packet. For information on how to determine the channel for communicating data, see
This will be explained 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 that it accommodates, and whether it is the terminal 4 on the upper network or the host computer. Discern.

If the destination of the data is another wireless terminal that it accommodates, it executes the downlink communication procedure of the wireless channel (see steps 205 and 206 in FIG. 6), which will be described later.

If it is a terminal 4 or host computer on the upper network, the destination terminal 4 or host computer 5
be transferred using the same transfer method as before.

When determining that the destination is neither the terminal 4 nor the host computer 5 on the upper network, nor any other wireless terminal it accommodates, it uses the group relay function (see Figure 6) of the upper network to The identification number of the source wireless terminal and the data are transmitted as one packet.

The reason why the group broadcasting function is used for transmission is that although the radio base station 6 knows which radio terminals it accommodates, it also knows which radio terminals are accommodated by other radio base stations. This is because we do not have all the information about what is happening. The destination of the data sent by the group routing function is
The wireless base station, which is for the wireless terminals it accommodates, follows the downlink communication procedure (6th step) of the wireless channel, which will be described later.
(see figure).

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

The wireless base station 6A uses the group broadcasting function to transmit the identification number and data of the destination wireless terminal 7B as one packet to all other wireless base stations 6B and 6C (
Step 203).

Even if the wireless base station 6C that does not accommodate the destination wireless terminal 7B receives this packet, it does not perform any operation. 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 transmitted (step 204>.

Thereafter, the wireless base station 6B determines the channel to be allocated as described below, and notifies the wireless terminal 7B, which is the destination of the packet, of the determined channel information using the communication control channel. Transfer the packet using the data channel determined for (step 205
．． 206).

Above, we have explained communication from a wireless terminal to a wireless base station, communication from a wireless base station to another wireless base station, and communication from a wireless base station to a wireless terminal. Communication to the station will be explained. In this case, as well as communication between wireless base stations, the terminal 4
All wireless base stations 6A, 6B with group broadcast function
, 6C, the identification number and data of the destination wireless terminal 7B are transmitted as one packet. The use of the group relay function is similar to communication between wireless base stations.

(D> Determination of communication channel In this embodiment, as mentioned above, a multi-channel access method is adopted in consideration of effective use of frequencies. Therefore, as explained in the communication method and communication protocol section, , the channel must be determined by taking into consideration the channels already used for data communication in the lower network.In other words, channel placement becomes a problem.

Channel allocation methods for communication networks can be broadly divided into fixed channel allocation methods and dynamic channel allocation methods.
Since these methods have the problems mentioned above, a new channel arrangement method is adopted.

Note that, in consideration of simplifying the control configuration and reducing the load on the upper network, the wireless base station 6 determines the channel as described above.

The channel determination method will be explained below in the order of determining adjacent base stations, creating a channel allocation table, and channel allocation algorithm.

(D-1) Determination of Adjacent Radio Base Stations By knowing which radio base station is adjacent to which radio base station, channels can be used effectively. In other words, in order to efficiently determine a channel, it is necessary to know neighboring wireless base stations.

Location information of a radio base station, which indicates which radio base station a certain radio base station is adjacent to, is essential data for the channel allocation method. If this (i-page information) is stored in a network (for example, host computer 5) in advance, the load on the network will increase and flexibility will be lost.
Since it would be difficult to add more wireless base stations, each wireless base station is designed to be able to dynamically acquire location information. First, a method for acquiring location information of adjacent wireless base stations will be described.

When errors in the communication line are random, long data requires a low error rate on the communication line. in general,
The shorter the communication distance, the lower the error rate, so communication request packets can reach farther and more accurately than data packets. Therefore, the wireless base station receives communication request packets from wireless terminals in a wider range than zone 8 of each wireless base station.

As described above, the number of the accommodating wireless base station and the number of the wireless terminal are inserted into the communication request packet of the wireless terminal and transmitted at the same time.

Therefore, we decided to detect adjacent wireless base stations using communication request packets.

FIG. 1 is a flowchart of such detection processing.

First, it is determined whether the received packet is a communication request packet (step 300). If you get a negative result,
Return to main routine (for example, containment operation, etc. is performed)
.

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

If the wireless base station receives a negative result because the received packet is not from a wireless terminal that it accommodates (a wireless terminal within the zone), the wireless base station transmits the received packet to the wireless base station that accommodates the communication request packet from outside the zone. is defined as the adjacent wireless base station (
Step 303).

Then, the numbers of adjacent wireless base stations received within a certain period of time in the past are stored as an adjacent wireless base station list (step 304).

(D-2) Creation of channel assignment table Next, the channel assignment table and its creation method will be explained.

In dynamic channel allocation, the channel usage status of other wireless base stations is required when determining the channel to be allocated. This information exchange has the drawback of increasing the load on the upper network. In order to minimize the amount of communication on the network and the buffer area, the amount of information held by a wireless base station should be limited to the minimum necessary.

Therefore, each wireless base station is configured to accumulate only the data of the allocated channel information of adjacent wireless base stations that may cause communication interference with each other.

Each wireless base station has the neighboring station list (N1
, N2, ..., Ni),
The group broadcasting function on the upper network can be used to find out which channels neighboring wireless base stations are currently using.
A channel allocation table for adjacent wireless base stations is created within the local station by constantly updating the usage status of channels of corresponding adjacent wireless base stations.

FIG. 7 is a flowchart of such processing.

First, it is determined whether the data given by the group broadcast function is allocated channel information (step 400).
. If a negative result is obtained, other processing (for example, downlink communication processing to the wireless terminal 7 shown in FIG. 6) is executed (step 401).

When a positive result is obtained regarding the allocated channel information, it is determined whether the transmission source is an adjacent wireless base station (step 402). If a negative result is obtained, the process is terminated without any processing; on the other hand, if a positive result is obtained, the contents of the channel allocation table are updated accordingly (step 403).

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

The channel allocation table also manages the number of times communication request packets have been received from wireless terminals accommodated in the adjacent wireless base station in the past. This value is a guideline for knowing how much interference will occur between neighboring radio base stations when they use the same frequency, and is hereinafter referred to as area multiplicity.

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

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

FIG. 8(B) shows that the wireless base station 61 accommodates a wireless terminal 71, the wireless base station 62 accommodates wireless terminals 72 and 73,
In the accommodating state shown in FIG. 8 (A>) in which the radio base station 63 accommodates the radio terminals 74 and 75, the first channel, second channel, . . . of each radio base station 61, 62, 63, etc. - The main body of the allocation table for the fifth channel is shown.

As shown in the area multiplicity column, the wireless base station 61
Wireless terminals 72 and 73 accommodated in the wireless base station 62
Since the wireless base station 62 has received a communication request packet from channel) is also stored in the channel usage status column along with information on the channel assigned by the user (first channel).

As shown in the area multiplicity column, the wireless base station 62
Since no communication request packets are received from wireless terminals accommodated in other wireless base stations 61, 63, etc., only the channel usage status information (second channel and fourth channel) assigned to the self-assigned channel is displayed. It is stored in the column.

As shown in the area multiplicity column, the wireless base station 63
Since a communication request packet is received from the wireless terminal 75 accommodated in the wireless base station 64, the wireless base station 64 is determined to be an adjacent wireless base station, and the group relay function is used to send the wireless base station 65 to the wireless base station 64. Regarding the assigned channel (5th channel) sent by the self-assigned channel (5th channel),
3rd channel) information is stored in the channel usage status column.

In this way, each radio base station accumulates only information on channels assigned by itself and channels assigned by adjacent radio base stations, and executes channel assignment control to be described later.

Since channels are assigned independently of wireless base stations that are so far away that they do not receive communication request packets, effective use of frequencies is achieved, and the buffer memory capacity required to store such tables is also small. It's done.

(D-3) Channel Arrangement Algorithm Next, the channel arrangement algorithm for determining channels will be explained.

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

When the wireless base station 6 receives a communication request packet from the wireless terminal it accommodates, it executes the process shown in FIG.
Based on the channel allocation table managed by the own station, the channel that is currently thought to cause the least interference with the adjacent radio base station is determined as the channel to be allocated.

In FIG. 9, first, based on the contents of the channel allocation table, it is determined whether there is an empty channel among the channels to which it is allocated (step 500).

If there is an empty channel that is not used by the adjacent radio base station or the own station, randomly select an allocated channel from among them (step 501), otherwise select the one with the smallest sum of area multiplicities (adjacent radio base station (step 502).

After determining a channel, before notifying the wireless terminal 7 of the determined channel, it is checked whether a notification to use this channel has been received from another adjacent wireless base station, and then the determined channel is notified to the wireless terminal 7. 7 (step 50)
3.504).

If a usage notification has been received from an adjacent wireless base station, the determination process is redone.

After that, the group broadcast function is used to notify all other wireless base stations of the allocated channel information (step 505).
.

Similarly, when communicating packets from a wireless base station to a wireless terminal, after determining the channel to be allocated from the table, the wireless terminal is called through the control channel, and at the same time, the allocated channel is notified to other wireless base stations.

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

Since the allocated channel information is exchanged in advance, a channel search in wireless communication becomes possible in a short time.

Because there is a wired network between base stations, it is possible to exchange information to avoid collisions on the wired network (allocation channel information, communication control channel usage information, etc.), which reduces communication collisions. can.

Since the wireless base station manages the channel, existing LA
The work when adding a wireless base station to N becomes easier. There is no need to change the configuration related to channel allocation for the entire network.

Since it is a dynamic multi-channel communication method that employs the channel arrangement method described above, it is suitable for conditions such as offices where the traffic density may change due to rearrangement or the scale of the network may increase.

(F) Other Embodiments Various types of upper network can be applied as long as they have a group broadcasting function.

That is, C8MA/CD, token passing bus,
Token passing ring, broadband path method, etc. can be applied. Furthermore, the upper network may not have any terminals.

The channel arrangement method etc. can be applied not only to LAN but also to other two-layer structured networks.

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

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a process for determining adjacent wireless base stations in a LAN according to an embodiment of the present invention, FIG. 2 is a block diagram showing the LAN configuration of the embodiment, and FIG. 3 is a block diagram showing its protocol control configuration. Figure 4 is an explanatory diagram of a method of accommodating wireless terminals, Figure 5 is an explanatory diagram of a method of communication from a wireless terminal to a wireless base station, and Figure 6 is an illustration of a method of accommodating wireless terminals from a wireless base station to another wireless base station. Explanatory diagram of communication method to terminal, 7th
The figure is a flowchart of the channel allocation table creation process, FIG. 8 is an explanatory diagram of the channel allocation table, and FIG. 9 is a flowchart of the allocation channel determination process. 1... L, AN, 2... Common bus, 4... Terminal on the upper network, 5... Host computer, 6... Wireless base station, 7... Wireless terminal.

Claims (2)

[Claims] (1) Communication that includes a plurality of wireless terminals and a plurality of wireless base stations accommodating the wireless terminals and interconnected by wires, and that applies a multi-channel access method to the wireless channel access method. In the network, a group broadcasting function is applied to the wired network part, and when each wireless base station receives a communication request from a wireless terminal that it does not accommodate, it transmits the wireless information included in the communication request. It recognizes the identification information of the base station, detects it as an adjacent wireless base station, and stores the allocated channel information when the source of the allocated channel information sent by the group broadcast function is an adjacent wireless base station. A communication network characterized by: (2) The radio base station is characterized in that when it becomes necessary to allocate a channel, the radio base station determines the channel to be allocated based on channel information already allocated by itself and adjacent radio base stations. The communication network according to claim 1.