JP3957491B2 - Wireless communication system - Google Patents

Wireless communication system Download PDF

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Publication number
JP3957491B2
JP3957491B2 JP2001346042A JP2001346042A JP3957491B2 JP 3957491 B2 JP3957491 B2 JP 3957491B2 JP 2001346042 A JP2001346042 A JP 2001346042A JP 2001346042 A JP2001346042 A JP 2001346042A JP 3957491 B2 JP3957491 B2 JP 3957491B2
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frequency
radio
router
communication
inter
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JP2003152732A (en
Inventor
弘司 江藤
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沖電気工業株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication system, and is suitable for application to, for example, a wireless LAN (local area network) system.
[0002]
[Prior art]
A conventional LAN is configured by a wired line such as Ethernet (registered trademark).
[0003]
On the other hand, in a wireless LAN (wireless LAN), communication is performed using a wireless line. Standard specifications such as IEEE802.11, IEEE802.11a, and IEEE802.11b are defined as standards for this wireless LAN.
[0004]
[Problems to be solved by the invention]
By the way, in a wireless LAN using radio waves, problems such as interference due to adjacent frequencies and deterioration of communication lines due to jamming waves may occur. However, the above-described IEEE802.11, IEEE802.11a, and IEEE802.11b may occur. The specification does not clearly define these points, and the arrangement of wireless routers and wireless switches, the frequency allocation method, etc. are unsolved problems.
[0005]
In addition, if the routing procedure of a LAN composed of wired lines is applied to a wireless LAN as it is, the transmission speed of the wireless LAN is generally slower than the transmission speed of the wired line, so that the speed of the wireless line allocated by routing becomes extremely slow. Depending on the terminal, communication failure may occur due to communication timeout.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the present invention Each wireless communication system is wireless Multiple radio base stations with areas Each radio With terminal stations in the area Wireless between Communicate Ruda Not just adjacent other Between radio base stations Also communicate wirelessly In a wireless communication system, each The radio base station (1) Send / receive frequency management list information having at least a plurality of radio frequencies set with priorities to be used in advance and allocation status information of each radio frequency to and from other adjacent radio base stations. A frequency management list information sharing means for sharing management list information; and (2) when performing wireless communication, referring to the frequency management list information, a radio frequency having a higher priority among radio frequencies not assigned to others, Radio frequency allocating means for allocating as a radio frequency to be used between terminal stations or other radio base stations in the radio area of the own station; and (3) using the radio frequency allocated by the radio frequency allocating means, Wireless communication means for wireless communication between terminal stations and / or other wireless base stations in the wireless region of It is characterized by providing.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
(A) Embodiment
Hereinafter, an embodiment will be described by taking a case where a wireless communication system according to the present invention is applied to a wireless LAN system as an example.
[0008]
If a LAN that does not use a wired line such as a cable as a communication line is a wireless LAN, general wireless LANs may include those that use radio waves, those that use infrared rays, those that use laser light, and the like. In the following embodiments, a wireless LAN mainly using radio waves will be described.
[0009]
Wired LANs such as Ethernet are basically built on the concept of distributed control in which each node (including not only terminals but also routers) on the LAN has an equal relationship, and even when accessing transmission media, it is a competitive CSMA. / CD is used, but in the case of a wireless LAN, distributed control may not always be appropriate, and it may be necessary to adopt a centralized control system configuration in which the relationship between the controlling node and the controlled node is clear.
[0010]
(A-1) Configuration of the first embodiment
An example of the overall configuration of the wireless LAN system 10 of this embodiment is shown in FIG.
[0011]
In FIG. 1, the wireless LAN system 10 includes routers 1 to 3, stations 1 </ b> S to 3 </ b> S and 1 </ b> S <b> 1, a wired LAN cable 20, and a server 21.
[0012]
Although the illustrated router includes three routers 1 to 3, these routers 1 to 3 can be regarded as all the routers in the system 10, and more routers included in the system 10. It can be considered that only a part is taken out from FIG.
[0013]
Each of the routers 1 to 3 is a device having a function as a base station for wireless communication in addition to a function as a router, and has different service areas 1A to 3A for each of the routers 1 to 3. That is, the router 1 has a service area 1A, the router 2 has a service area 2A, and the router 3 has a service area 3A.
[0014]
In the state shown in the figure, the stations 1S and 1S1 exist in the service area 1A, the station 2S exists in the service area 2A, and the station 3S exists in the service area 3A. Of course, the number of stations present in each service area 1A-3A need not be the same, and may be more than one.
[0015]
Various communication devices can be used as the stations 1S to 3S and 1S1, and they may have mobility as necessary. In many cases, however, the station is equipped with a wireless LAN LAN card (LAN adapter). A typical example is a laptop personal computer or a notebook personal computer.
[0016]
Generally, the size of the service area is determined according to the transmission power value of each router, and the two-dimensional shape of the service area is a directivity pattern in the horizontal plane of the antenna that each router uses for wireless transmission to each station. It depends on. In addition, for example, in order to cover an entire geographical area having a certain size without omission in any service area, adjacent service areas need to overlap each other. This is not necessary if there may be uncovered areas.
[0017]
In the example of FIG. 1, the shapes of the service areas 1A to 3A are substantially circular, and the service areas 1A and 2A overlap, but the service areas 3A do not overlap both 1A and 2A.
[0018]
There may be various distances between adjacent routers and distances between the router and the terminal. In wireless LAN, for example, the distance between adjacent base stations is 1 to 2 kilometers, and the distance between the terminal and the base station. May be several tens of meters. If this is applied to the present embodiment and the distance between the router and the station (for example, the distance between the router 1 and the station 1S) is 50 meters (maximum value) and the distance between the routers is 1 kilometer, the service of FIG. It is easy to configure so that no overlap occurs between the areas 1A and 2A.
[0019]
Further, the frequency used for communication (intra-area communication) between the router and the station (for example, the router 1 and the station 1S) in each service area is not necessarily one, and may be plural. However, in order to save frequency resources, the number is preferably one. Also in the present embodiment, a single frequency is used for the intra-area communication. That is, the frequency f1 is used in the communication in the service area 1A, the frequency f2 is used in the communication in the service area 2A, and the frequency f3 is used in the communication in the service area 3A.
[0020]
As long as a radio signal of a single frequency is used for intra-area communication, any one service area (for example, 1A) among the service areas 1A to 3A is one segment under each router (for example, 1). This corresponds to (one collision domain). Therefore, in this case, a collision occurs when a plurality of devices (stations or routers) simultaneously transmit wirelessly within one service area. In the case of wireless communication, it is difficult to use CSMA / CD (Carrier Sense Multiple Access with Collision Detection) like Ethernet, so in many cases CSMA / CA (CSMA with Collision Avoidance) is used to avoid collision. The
[0021]
Furthermore, in the present embodiment, the routers 1 to 3 not only communicate with each station (1S or the like) but also communicate with other routers (for example, the router 2 or 3 for the router 1). (Inter-communication) also uses radio, so it is necessary to consider that intra-area communication and inter-area communication do not interfere. Here, the routers 1 to 3 are connected to each other only by communication between the areas, and are not connected using a wired line.
[0022]
A configuration example of the main part of the routers 1 to 3 is shown in FIG.
[0023]
Since the functions of the routers 1 to 3 may be substantially the same, the description will be made assuming that the router 1 is mainly shown in FIG. However, the router 1 connected to the wired LAN (Ethernet) ET 1 via the wired cable 20 is also equipped with a unique function that the other routers 2 and 3 do not have.
[0024]
(A-1-1) Configuration example of router
In FIG. 2, the router 1 includes antennas AT <b> 0 to AT <b> 6, radio units 30 to 36, a control unit 37, and an Ethernet interface unit 38.
[0025]
Among these, the antenna AT0 is an omnidirectional antenna for performing communication within the area, and has an omnidirectional directivity pattern in a horizontal plane.
[0026]
Antennas AT1 to AT6 are directional antennas for performing communication between the areas, and exhibit directivity in a horizontal plane. As described above, when the routers 1 to 3 are all the routers in the system 10, the router 1 only needs to perform inter-area communication with at most two routers (2 and 3). Two antennas are sufficient. However, when the routers 1 to 3 are illustrated by extracting only a part from a larger number of routers included in the system 10, three or more directional antennas are used. May need to be provided.
[0027]
Since it is a problem that depends on the network configuration with which router a certain router performs inter-area communication, in general, the router 1 is not necessarily all neighboring routers that are arranged geographically adjacent to each other (for the router 1). For example, it is not necessary for the routers 2 and 3 to perform inter-area communication with adjacent routers). However, here, it is assumed that inter-area communication is performed with all adjacent routers.
[0028]
In this case, the provision of the six directional antennas AT1 to AT6 corresponds to the case where the router 1 has six adjacent routers and performs inter-area communication with all of them. If all directions in the horizontal plane with the router 1 as the center are divided into six equal parts, the arrangement of the directional antennas AT1 to AT6 is as shown in FIG. 3, and the directional antennas AT1 to AT6 have a radiation angle of 60 degrees.
[0029]
If the directivity patterns of the directional antennas AT1 to AT6 are sharply narrowed into a beam shape, higher accuracy is required for the positional relationship of the routers 1 to 3 and the like to be installed and the direction adjustment of the directional antennas AT1 to AT6. However, it is possible to reduce or eliminate the geographical influence of inter-area communication on intra-area communication performed in the surrounding service area, so that other routers can communicate within the area within other service areas. This makes it easier to use the frequency used for inter-area communication, improving the frequency utilization efficiency in the geographical area.
[0030]
Depending on the overlap status of each service area, etc., as long as there are at least three frequencies, as shown in FIG. 7, all inter-area communications and all intra-area communications are performed for six neighboring routers. Can be covered.
[0031]
FIG. 7 illustrates four of the six neighboring routers for the router 1, and shows a configuration in which routers RX1 and RX2 are added in addition to the two routers 2 and 3 illustrated in FIG. As is apparent from FIG. 7, the frequency used by the router 1 for inter-area communication of the router 1 for intra-area communication and the frequency used by the router 1 itself for intra-area communication (here, f1) Any other frequency may be used for inter-area communication.
[0032]
Therefore, inter-area communication using f3 is performed with the router R2 using f2 in intra-area communication, and inter-area communication using f2 is performed with the router R3 using f3 in intra-area communication. Inter-area communication using f2 (this f2 can be replaced with f3) is performed with the router RX1 that uses f1 in internal communication, and f3 is used with the router RX2 that uses f2 in internal communication Inter-area communication is performed.
[0033]
Note that, when the above-described overlap occurs between service areas, the operation in a station located on the overlapped area can be a problem. In particular, there is a problem with respect to overlap occurring between service areas using the same frequency for intra-area communication (for example, overlap between service areas 1A and 4A in FIG. 7).
[0034]
In response to this, for example, a frequency repeat pattern (12 cell repeat pattern) of a small zone system of a car phone is used so that the frequency of in-area communication of any two overlapping service areas is always different. However, in this case, twelve frequencies are required, and the frequency utilization efficiency is lowered.
[0035]
The simplest way to solve this problem while conserving frequency resources is to not allow the occurrence of such overlap itself. As described above, if the size of the service area of each router is sufficiently small compared to the distance between routers that perform inter-area communication (for example, service areas 1A and 4A compared to the distance between router 1 and RX1). If the size of is small enough, the overlap does not occur.
[0036]
Alternatively, even if the occurrence of overlap itself is allowed, it can be dealt with by executing an operation in which a station (for example, 1S) is not arranged in the overlapping area.
[0037]
In FIG. 2, radio units 30 to 36 are connected to one omnidirectional antenna AT0 and six directional antennas AT1 to AT6 of the router 1, respectively. The functions of the radio units 30 to 36 are substantially the same. When radio transmission is performed from a connected antenna, modulation processing is performed, and encoding processing, encryption processing, etc. are performed as necessary. In addition, when a radio signal is received from an antenna, it is a part that performs demodulation processing and performs decoding processing as necessary.
[0038]
The frequency received and demodulated by each radio unit is fixed to the assigned specific frequency after the assignment of the frequency is determined, and the frequency is maintained until the assignment is changed due to a failure or the like. However, in the initial state before allocation is performed, reception is performed for all frequencies that may be allocated. Specific values of all frequencies that may be assigned may be stored in a non-volatile memory (not shown) built in the radio unit.
[0039]
As long as each router is in this initial state, each router basically does not perform inter-area communication, but performs radio transmission at a specific frequency assigned after the frequency assignment is determined. The same applies to transmission in that the frequency is maintained until the assignment is changed due to a failure or the like. The frequency for radio transmission and the frequency for reception for each router may be provided separately, but the same frequency is used in this embodiment.
[0040]
The radio unit also has a function of detecting and notifying the occurrence of a failure. An IP packet output to the control unit 37 is used for notification of the occurrence of a failure.
[0041]
In the configuration of the present embodiment, it is natural that even the wireless units in the same router (for example, the wireless units 30 and 31 in the router 1) need to be able to operate independently of each other.
[0042]
Basically, one antenna and one radio unit (for example, AT0 and 30) connected thereto can be regarded as one port in the Ethernet router.
[0043]
Here, it is assumed that the radio unit 30 executes processing in a layer below the MAC sublayer located in the data link layer of the OSI reference model.
[0044]
The control unit 37 basically functions as the routing processing unit 40 (see FIG. 5), and performs routing using a routing table (not shown) prepared in advance. The said control part 37 as the routing process part 40 may be the same as the routing process part which performs routing in the router for normal Ethernet.
[0045]
Therefore, for example, if the routing processing unit 40 corresponds to IP (Internet Protocol) as the network layer protocol of the OSI reference model, the MAC obtained in the wireless unit 30 based on the wireless signal WL1 wirelessly transmitted by the station 1S. (Media access control) Inter-area communication is necessary when it is found from the MAC address table or the like that the frame destination MAC address exists in the service area 1A (for example, the MAC address of the station 1S1). Therefore, the wireless unit 30 does not output the IP packet BA1, and the control unit 37 (routing processing unit 40) does not perform any processing, but the destination MAC address is the MAC address of the LAN card installed in the router 1 itself. If is wireless 30 extracts an IP packet from the MAC frame and supplies it to the control unit 37. The control unit 37 refers to the routing table based on the destination IP address of the IP packet and outputs it to the necessary radio unit. .
[0046]
For example, when the destination IP address is the IP address of the station 3S, the control unit 37 outputs the IP packet BA8 to the wireless unit 33 for performing inter-area communication with the router 3.
[0047]
Receiving this, the wireless unit 33 wirelessly transmits the wireless signal WL8 from the directional antenna AT3 to perform inter-area communication toward the router 3.
[0048]
In addition, when the transmission destination MAC address of the MAC frame exists in the service area 1A, for example, the stations 1S and 1S1 directly communicate using the frequency f1 without passing through the router 1 (this is also an area). Internal communication).
[0049]
On the other hand, the Ethernet interface unit 38 connected to the control unit 37 is also one port similar to the wireless units 31 to 36 when viewed from the control unit 37, but the entity of the Ethernet interface unit 38 is the wireless unit 31. It is completely different from ~ 36.
[0050]
That is, the Ethernet interface unit 38 functions as an access point (AP) from the wireless LAN system 10 to the wired LAN system ET1, and is an IEEE 802.3 protocol used in general Ethernet (here, the wired LAN system ET1). And a gateway that performs interface conversion with a protocol (for example, IEEE802.11 protocol) used in the wireless LAN system 10.
[0051]
The Ethernet interface unit 38 is a function unique to the router 1 that is not provided in other routers (for example, 2, 3) that are not connected to the wired LAN system.
[0052]
The control unit 37 has, for example, an internal configuration shown in FIG.
[0053]
(A-1-2) Internal configuration example of control unit
In FIG. 5, the control unit 37 includes a routing processing unit 40, a frequency allocation unit 41, a list update unit 42, and a list storage unit 43.
[0054]
Among these, the function of the routing processing unit 40 is as described above, but the constituent elements with which the routing processing unit 40 exchanges IP packets are not limited to the radio units 30 to 36 and the Ethernet interface unit 38, but the frequency allocation unit. 41 and a list update unit 42 are also included.
[0055]
The frequency allocation unit 41 is a part that changes the allocation of frequencies used in the intra-area communication and inter-area communication when, for example, a dynamic factor such as a failure occurs.
[0056]
For Ethernet using a wired line, communication cannot be continued unless the wired cable is physically damaged, except when the line is duplicated, but it is used when a wireless line is used. In many cases, communication can be continued by changing the frequency (channel). Since the characteristics of propagation paths in wireless communication generally vary greatly depending on the frequency, the quality of communication using a certain frequency is extremely poor (for example, this corresponds to the case where the cable is disconnected in wired communication) This is because communication using other frequencies can often be performed well.
[0057]
The list accumulation unit 43 is a kind of database that accumulates a frequency list indicating the allocation status of frequencies currently used for intra-area communication and inter-area communication. When it is necessary to save the contents of the frequency list even when the power supply is cut off, the list storage unit 43 needs to be configured by a non-volatile storage means such as a hard disk.
[0058]
The frequency list is generated based on the logical structure shown in FIGS. 6A and 6B as an example. Here, the table of FIG. 6A is an allocation table, and the table of FIG. 6B is a priority table. The allocation table in FIG. 6A includes three data items. That is, “assignment destination” indicating the assignment destination of each frequency (channel), “failure occurrence” indicating whether or not a failure has occurred in each assignment destination, and “channel number” uniquely specifying each frequency.
[0059]
Also, the priority order table of FIG. 6B includes “priority order” that defines the order of use of each frequency and the “channel number” as data items. Since the channel number is provided as a common data item in the table of FIG. 6A and the table of FIG. 6B, it is obvious that both tables can be naturally combined using the channel number. . A table obtained by naturally combining both tables is used as a frequency list.
[0060]
This frequency list is a table in which “priority”, which is a data item of the priority table, is added in addition to “allocation destination”, “failure occurrence”, and “channel number” which are data items of the allocation table. . In the example of FIG. 6A, the priority value of each tuple is the priority value (1), (2), (3), (2), (2), (2) ), (1),..., (4), (5), (6).
[0061]
In the priority table shown in FIG. 6B, the channel number of frequency f1 is CN (f1), the channel number of frequency f2 is CN (f2), the channel number of frequency f3 is CN (f3), and the channel number of frequency f4 Is CN (f4), the channel number of frequency f5 is CN (f5), and the channel number of frequency f6 is CN (f6). Therefore, the frequencies that can be used in the entire wireless LAN system 10 are six frequencies f1 to f6. . However, normally, only the upper three priority frequencies (f1, f3, f2) are used, and the remaining three frequencies (f4 to f6) are spare frequencies prepared in case of a failure.
[0062]
In the allocation table shown in FIG. 6A, the allocation destination indicates the code of the service area that is the allocation destination when communication using the frequency is intra-area communication, and communication is performed when communication between areas is performed. The codes of both routers are shown.
[0063]
Therefore, the tuple arranged at the top of FIG. 6A is the frequency f1 designated by the channel number CN (f1) for the frequency used in the intra-area communication of the service area 1A. It indicates that no failure has been detected in the intra-area communication used. Similarly, in the tuple arranged second from the top in FIG. 6A, the frequency used in the inter-area communication performed between the routers 1 and 2 is f3 specified by the channel number CN (f3). This indicates that no failure has been detected in the inter-area communication using the frequency f3 at that time.
[0064]
It should be noted that the tuples arranged in the lower order in FIG. 6A, for example, the lowest tuple, the assignment destination is “not yet”, the failure has occurred “not yet”, and the channel number is CN (f6). Indicates that the assignment has not yet been made and is therefore not subject to detection of the failure.
[0065]
If necessary, the frequency used for intra-area communication and the frequency used for inter-area communication may be clearly distinguished and defined in the priority order table, but in FIG. No distinction is made. Therefore, all the frequencies f1 to f6 can be used for intra-area communication and inter-area communication.
[0066]
For example, the frequency list shown in FIG. 6A is stored in the list storage unit 43. This frequency list is supplied to the router 1 from the server 21 with the priority shown in FIG. 6B. Based on the ranking table, the routers 1 to 3 and the like are dynamically generated as a result of the cooperation.
[0067]
The list update unit 42 connected to the list storage unit 43 by a signal MP is a part that updates the contents of the frequency list as necessary. The update of the frequency list is performed in response to the progress of frequency allocation for intra-area communication and inter-area communication at the beginning of operation, and is also performed as needed when a failure is detected during operation.
[0068]
The occurrence of an event that triggers list update, such as the progress of frequency allocation or the occurrence of a failure, and the contents of the event are determined by the routers 1 to 3 by the IP packet BAY supplied from the routing processing unit 40 to the list update unit 42. Is transmitted from the corresponding wireless unit to the list updating unit 42 of the router 1.
[0069]
It can be said that the frequency allocation change executed by the frequency allocation unit 41 is an operation for physically realizing the logical update contents of the frequency list. The change of the frequency assignment that the frequency assignment unit 41 transmits to each wireless unit (for example, 30 or 31 or the wireless unit of another router) is transmitted as an IP packet supplied to the routing processing unit 40 as a signal RE. Whether it has been executed or not is notified to the frequency allocation unit 41 by a response IP packet BAH.
[0070]
The server 21 provides the priority order table in response to a request from the router 1.
[0071]
The operation of the present embodiment having the above configuration will be described below. Here, the operation will be described by taking as an example a case where communication between all areas and communication within all areas in the wireless LAN system 10 is basically performed using only the three frequencies f1 to f3.
[0072]
(A-2) Operation of the first embodiment
First, an initial operation when the wireless LAN system 10 is configured will be described.
[0073]
(A-2-1) Initial operation
First, when the router 1 connected to the wired LAN system ET1 is turned on and the router 1 is activated, the router 1 is connected to the server 21 from the server 21 in accordance with a procedure that can be executed on a normal Ethernet, for example, FIG. The priority table as shown in FIG.
[0074]
The state of the other routers 2, 3 and the like at the time when the router 1 is activated can be both a case where it has not been activated and a case where it has already been activated. In addition, the already activated cases include cases where each activated router is not already executing intra-area communication or inter-area communication.
[0075]
However, here, when the router 1 is activated, it is assumed that other routers have not yet been activated, or even if they have been activated, at least inter-area communication has not started yet, and inter-area communication is started first. It is assumed that the router 1 and the other routers sequentially start these communications following the router 1.
[0076]
That is, the router 1 generates a frequency list, for example, as shown in FIG. 6A according to the received priority list, and stores the frequency list stored in the list storage unit 43 of each router other than the router 1. In addition, consistency between the frequency lists is ensured so that the content is the same as the frequency list stored in the list storage unit 43 in the router 1. For this process, a process used for ensuring consistency of update contents in the distributed database can be used as it is.
[0077]
Since the assignment has not yet been established for any of the frequencies f1 to f6 immediately after the router 1 is activated, the value of each data item in each tuple of the frequency list is not valid.
[0078]
Since at least inter-area communication is not yet executed in any router, the router 1 at this time is basically free to use any frequency in the priority table, but here, Based on the priority value, the frequency f1 of the channel number CN (f1) with the highest priority is used.
[0079]
That is, the router 1 uses the frequency f1 to send control information to the service area 1A through the radio unit 30 and the antenna AT0. When there is data to be transmitted at that time, a terminal in the service area 1A that has received this control information, for example, the station 1S, sends a request signal for receiving service in the service area 1A of the router 1 at the frequency f1. Return it. When the router 1 receives this request signal, it sends a permission signal at the frequency f1, and the connection between the router 1 and the station 1S is completed. This procedure may be in accordance with, for example, IEEE 802.11b or Bluetooth.
[0080]
Normally, connectionless communication is performed in a wired LAN segment such as Ethernet, but here connection-type communication is performed.
[0081]
The reception of the control information is not limited to the station 1S, but can be executed by all terminals (for example, 1S1) in the service area 1A, so that each terminal can be used for intra-area communication by the reception. Among the plurality of possible frequencies (here, f1 to f6), the frequency (here, f1) conveyed by the control information is used between the router 1 and the terminal (here 1S1 or 1S) and between the terminals (between stations). A common recognition that it will be used for communication with other routers can be formed.
[0082]
If there is already data to be transmitted to both the stations 1S and 1S1 at this time, there is a possibility that the request signal is returned almost simultaneously at the same frequency f1, and at the same frequency f1 as the transmission of the request signal. When the router 1 transmits a permission signal, collision may occur between the request signal and the permission signal. In this case, for example, the above-described collision avoidance method such as CSMA / CA can be used. It is.
[0083]
Even if the same frequency is used, the MAC address assigned to each station's LAN card is unique, so by using the MAC address, the router 1 grants permission to only one station by a permission signal. It is possible to uniquely specify a station that can transmit data. As a result, it is possible to prevent the occurrence of collision at the time of data transmission that may occur in Ethernet or the like.
[0084]
This is processing corresponding to the above-described centralized control system configuration in which the node to be controlled is a station (for example, 1S, 1S1) and the node to be controlled is a router 1.
[0085]
After the process related to the intra-area communication or simultaneously with the process related to the intra-area communication, the router 1 wirelessly transmits a predetermined control signal to execute the process for realizing the connection related to the inter-area communication. To do. This control signal includes the frequency list.
[0086]
The processing for inter-area communication connection performed by the router 1 is performed for each adjacent router of the router 1, but the content of the processing is substantially the same.
[0087]
Among neighboring routers that accept this processing from the router 1, for example, the router 2 executes necessary processing according to the processing procedure written in advance in the nonvolatile memory when the power is turned on.
[0088]
For this reason, the operation of the router 2 differs depending on the contents of the processing procedure. For example, a process for starting an effective operation after the frequency used for intra-area communication in its own service area 2A and the frequency for inter-area communication with its own neighboring routers is determined in cooperation with the router 1 Although it is possible to use a procedure, when the service area 2A does not have the above-described overlap in relation to any service area, for example, the necessity for at least intra-area communication is low.
[0089]
Therefore, when there is no overlap, the router 2 can execute intra-area communication at an arbitrary frequency even before the frequency assigned for intra-area communication is determined. Therefore, communication can be performed between terminals in the service area 2A such as the station 2S.
[0090]
In this case, like the router 1, the router 2 can exchange the control information, the request signal, and the permission signal with a station (for example, 2S) in the service area 2A. This also applies to other neighboring routers (3, RX1, RX2, etc.) other than the router 2 and routers not adjacent to the router 1, and each station can perform intra-area communication within each service area. it can.
[0091]
In this way, with each station in the service area of each router performing intra-area communication for each individual under the control of each router, for example, the router 1 is connected to the inter-area communication from the router 1. A control signal for realization is wirelessly transmitted. The main component of this control signal is the frequency list. The frequency list and the priority order table at this point are the frequency list, but the frequency list is not in the state shown in FIG. 6 (A). In this state, there is only a tuple located at the top.
[0092]
Any router may be used as long as the router 1 first starts this processing as long as the router 1 is adjacent to the router 1. However, since it is assumed that the router 2 is selected first, the router 1 For inter-area communication between the routers 2, the frequency f3 corresponding to the second from the top in the priority table shown in FIG. 6B is used. The use of f3 may be forced from the router 1 to the router 2, or may be determined by arbitration between the router 2 and the router 1 if necessary.
[0093]
For example, when the router 2 has already used the f3 for intra-area communication, if the frequency of intra-area communication is not to be changed, a frequency other than f3 (for example, f2) is desired as the inter-area communication frequency. Is possible.
[0094]
On the router 2 side, in order to receive the radio signal from the router 1, all the radio channels assigned in the system (here, f1 to f6) are preliminarily stored in the non-volatile memory, The control signal is received by sequentially performing the search. And for this reception, a directional antenna and each radio | wireless part 31-36 connected to them are used.
[0095]
The router 2 also tries to receive the control signal from the router 1 for the frequency used for intra-area communication in its service area 2A. At this time, it is necessary for the router 2 to temporarily suspend intra-area communication or perform it at a different frequency.
[0096]
In any case, when the frequency used in the inter-area communication between the routers 1 and 2 is determined, it is reflected in the frequency list. For example, when it is determined that the frequency f3 is used for the inter-area communication, the frequency list is the second tuple from the top with respect to the uppermost part in FIG. Thus, a tuple having a channel number CN (f3) is added.
[0097]
Therefore, the frequency list in this state is accumulated in the list accumulation units 43 of both the router 1 and the router 2, and the consistency of the frequency list is ensured. At this point, inter-area communication cannot be performed for routers other than routers 1 and 2 (for example, 3), so that the consistency of the frequency list is ensured only between routers 1 and 2. become.
[0098]
Next, the frequency used by the router 2 for intra-area communication executed in the service area 2A is determined. Since this determination is performed based on the judgment of the router 2 itself, it is necessary to return the determination result to the router 1. Various methods are conceivable as to how the router 2 selects a use frequency for intra-area communication. For example, it is possible to select a frequency that has been used for intra-area communication so far, or to ignore this and select a frequency only according to the priority value, but at least for inter-area communication with the router 1 It is necessary that the frequency is different from the frequency f3 determined to be used.
[0099]
In addition, when it is necessary to consider the overlap between the service area 1A of the router 1 and the service area 2A of the router 2, the frequency must be different from the frequency f1 determined to be used by the router 1 for intra-area communication. There is. In order to determine whether or not there is an overlap, or in which service area the overlap will occur, the geographical location and distance between each adjacent router, and each adjacent router Naturally, the router 2 needs to recognize various information related to the physical configuration of the wireless LAN, such as the size and shape of the service area.
[0100]
When the router 2 selects a frequency different from the frequency used for the intra-area communication until then, the frequency used for the intra-area communication is changed before and after the determination, and this change is performed within the service area 2A. It is transmitted to each station (for example, 2S).
[0101]
For example, when f2 is determined as the frequency used by the router 2 for intra-area communication, the third tuple from the top of FIG. 6A is further added to the frequency list, and this is returned to the router 1. . However, if it is known that the router 2 always determines the frequency to be used for intra-area communication according to the priority value, the router 1 can reliably predict the determination result of the router 2, so Although it is not necessary to return a final result to the router 1, at least as long as the control signal transmitted by the router 1 has been normally received as long as the wireless communication quality is not necessarily good, the router 2 Need to be communicated to router 1.
[0102]
The processing for inter-area communication and intra-area communication similar to the router 2 is repeated for the other routers adjacent to the router 1, and a tuple is added to the frequency list each time.
[0103]
The above processing will be described with reference to FIG. 7. First, the frequency f1 used for the intra-area communication of the router 1 is determined, and subsequently, the inter-area communication frequency f3 between the routers 1 and 2 is determined. The frequency f2 for intra-area communication is determined, and the frequency for inter-area communication and intra-area communication is determined in turn for the other adjacent routers 3, RX1, RX3. As a result, basically, for example, as shown in FIG. 4, routers connected to each other by inter-area communication can communicate with each other.
[0104]
In FIG. 4, the frequency of inter-area communication extending radially around the router is distinguished by a triple line, a dotted line, and a solid line. Here, for example, the triple line may indicate the frequency f3, the dotted line may indicate the frequency f2, and the solid line may indicate the frequency f1.
[0105]
For all the routers that exist and operate in the wireless LAN system 10, the frequency of the inter-area communication and the intra-area communication is determined, and when the determination is reflected in the frequency list, the above initial operation ends. Then, after the initial operation is completed, a steady operation state in which intra-area communication and inter-area communication are executed is performed for each router according to the frequency list.
[0106]
At this time, a signal wirelessly transmitted by each station (for example, 1S) by intra-area communication is transmitted to a station (for example, 2S) that is a destination of the wireless signal as necessary, in order to deliver the signal to a router (for example, 1S). ) And is transmitted to a router (for example, 2) under the station serving as the destination by using required communication between areas, and further transmitted from the router to the destination. If so, data can be transmitted to any destination within and between areas.
[0107]
When such routing is normally performed in the entire wireless LAN system 10, there is no failure in each assigned channel number shown in FIG.
[0108]
However, if such a steady operation state is continued, for example, any inter-area communication or intra-area communication in the wireless LAN system 10 is caused by a noise generation source inside or outside the system 10. It may happen that it cannot be executed normally. In this case, various types of failure may occur depending on the intensity and frequency of noise (interference wave), the position of the noise generation source, and the like.
[0109]
For example, if the noise source is at position N in FIG. 7, the noise frequency is f3, and the noise intensity is not so strong, only the inter-area communication between the routers 1 and 2 becomes impossible. Intra-area communication and inter-area communication can be performed normally, but if this noise is strong, other inter-area communication using the frequency f3 (for example, inter-area communication between the router 1 and RX 2) Communication may also be disabled, and if the noise frequency band extends not only to f3 but also to f1 and f2, inter-area communication and intra-area communication using f1 and f2 will be affected. there is a possibility.
[0110]
However, here, as an example, since the noise source is at position N in FIG. 7, the noise frequency is f3, and the noise intensity is not so strong, only communication between the areas between the routers 1 and 2 is impossible ( Alternatively, even if communication can be continued, a transmission path with a very high BER (bit error rate) is in a poor state, and other intra-area communication and inter-area communication can be normally performed. Next, the recovery operation will be described.
[0111]
It is detected by the router 1 or 2 that the communication between the areas between the routers 1 and 2 cannot be normally performed, and by the detection, the failure of the second tuple from the top in FIG. Updated.
[0112]
(A-2-2) Recovery operation
As described above, in such a wired LAN system, in such a case, the router 1 gives up direct communication with the router 2 and performs, for example, inter-area communication using a detour route via the router 3. However, in the case of wireless, unlike the case of wired communication, the inability to communicate is not always a fatal failure of the line.
[0113]
Inability to communicate frequently due to jamming waves in the channel caused by some cause or interference with other systems may occur, and recovery is expected by changing the channel frequency used.
[0114]
Of course, even in the case of wireless, using a detour route is one of the restoration methods, as in the case of wired communication. For example, when the frequency band of the interference wave is extremely wide and covers all the frequencies f1 to f6. Even in the case of wireless communication, the use of the detour route may be the only restoration method. However, when restoration is performed using a detour route, a larger communication traffic flows through the router existing on the detour route than before the restoration, and a large load is applied. Even though the wireless LAN has a communication speed slower than that of the wired LAN, even if the communication speed is further reduced due to such an increase in load, the communication failure due to the communication timeout described above may occur. It is not preferable in various points.
[0115]
In order to avoid such a situation, when the router 1 and the router 2 detect a communication failure caused by the noise generation source at the position N, the frequency list at that time (this is the case except for the second tuple from the top, FIG. According to (A), communication at a high priority frequency is attempted.
[0116]
However, at this time, the frequency f1 used by the router 1 for intra-area communication and the frequency f3 used by the router 2 for intra-area communication cannot be selected. When communication between the areas between the routers 1 and 2 is performed with a directional antenna having a beam-like sharp directivity, or when there is no overlap with adjacent service areas (for example, 4A, 3A), The frequency can be selected without being conscious of the frequency used for intra-area communication, but if this is not the case, it is necessary to select the frequency by excluding the frequency used for intra-area communication within the adjacent service area. is there.
[0117]
Assuming that the state of the frequency list at the time of failure detection is as shown in FIG. 6A except for the second tuple from the top, the spare frequency is f4 specified by the channel number CN (f4) and the channel number. Since f5 specified by CN (f5) and f6 specified by channel number CN (f6), the highest priority is frequency f4. Inter-area communication using frequency f4 is attempted.
[0118]
When it is confirmed between the routers 1 and 2 that the communication between the areas can be normally performed, the channel number of the second tuple from the top is updated from CN (f3) to CN (f4), and the third channel from the bottom. The tuple with the number CN (f4) is deleted, and the recovery operation ends. If only the inter-area communication between the routers 1 and 2 was using the frequency f3 before the restoration, the restoration results in a new assignment destination not yet, failure has not occurred, and the channel number is CN (f3). The tuple is added to the bottom of the frequency list. However, in FIG. 6A, since the frequency f3 is also used for inter-area communication between the routers 1 and 3, such addition is not performed. Eventually, the spare frequency is reduced by 1 to 2 frequencies.
[0119]
If necessary, for all-area communication and intra-area communication using the frequency f3 before restoration, an update may be performed to change the frequency f3 to the frequency f4. With such an update, the spare frequency can be maintained at 3 frequencies.
[0120]
It should be noted that the content of this update is ensured in consistency in the list storage unit 43 of all routers in the wireless LAN system 10.
[0121]
Since the noise from the noise source at position N that caused this failure may disappear naturally or may be erased by conscious work, it does not remain permanently. The frequency f3 that becomes the frequency can be reused after the noise disappears. Further, even before the disappearance of the noise, if the noise is not strong, the frequency f3 can be reused at a place other than between the routers 1 and 2 (for example, intra-area communication performed in the service area 4A). is there.
[0122]
If it is confirmed that the inter-area communication using the frequency f4 cannot be normally performed, the inter-area communication using the frequencies f5 and f6 is sequentially tried according to the priority order.
[0123]
Even when a trial using the lowest priority frequency f6 is performed, if the normal inter-area communication cannot be performed, the bypass route may be used.
[0124]
However, even in this case, since the frequencies f1 and f2 have not been tried yet, it is good to try the frequencies f1 and f2 that are already used as necessary. Of course, using the frequency f1 for the inter-area communication means changing the frequency of the intra-area communication performed in the service area 1A of the router 1, and using the frequency f2 for the inter-area communication. This means that the frequency of intra-area communication performed in the service area 2A of the router 2 is changed. The effect of this change also affects other intra-area communications and inter-area communications, and thus has a significant effect on the entire wireless LAN system 10, but in terms of communication speed compared to the case of using a detour route. It is advantageous.
[0125]
If necessary, the communication between the areas is not simply attempted sequentially using each frequency (for example, f4), but the noise frequency is measured and the communication between the areas is performed according to the measurement result. The frequency to be used may be determined. This may shorten the time required for the recovery operation.
[0126]
In addition, when setting a detour route, select a route that reduces the number of routers (hops) existing on the detour route, and consider the free bandwidth of each router to increase the speed of new communication traffic. It is desirable to select a route that has a high possibility of being transmitted.
[0127]
In order to select this detour route, in addition to the priority table, a routing list indicating routes that are normally connected when a failure occurs (this includes the MAC address of each router and the router connected to each route). The relationship between the MAC addresses is described, and the frequency information (channel number and the like) used in the connection between the routers is also described therein. The routing list can be configured by appending the MAC address of each router to the frequency list.
[0128]
After the restoration operation is completed, the normal operation state is restored, and intra-area communication and inter-area communication are executed for each router according to the frequency list.
[0129]
The recovery operation as described above is the same even when a failure occurs in inter-area communication other than between the routers 1 and 2 (for example, inter-area communication between the routers 2 and 3) and intra-area communication. In the initial operation, the router 1 played a special role. In a normal operation state, the routers (1 to 3, RX1, RX2, etc.) in the wireless LAN system 10 are in an equal relationship, This is because the system configuration belongs to the category of distributed control.
[0130]
As for the power-on for each router in the wireless LAN system 10 performed during the initial operation, a network for powering on may be separately configured as necessary.
[0131]
(A-3) Effects of the first embodiment
As described above, according to the present embodiment, it is possible to realize efficient router arrangement and frequency allocation in a wireless LAN system.
[0132]
Further, in this embodiment, by using a frequency list, a routing list, etc., a large-scale wireless LAN system can be configured, and a radio frequency can be used effectively, enabling high-speed and stable communication and high-speed routing. .
[0133]
Furthermore, it is possible to flexibly cope with a dynamic factor such as the occurrence of a failure while suppressing a decrease in communication speed and maintaining overall consistency.
[0134]
(B) Second embodiment
Below, only the point from which this embodiment is different from 1st Embodiment is demonstrated.
[0135]
In the first embodiment, the same frequency is used for inter-area communication and intra-area communication in the wireless LAN system 10, but in the present embodiment, these are clearly distinguished.
[0136]
In terms of frequency utilization efficiency, it is advantageous not to distinguish between the two, but in a method that does not distinguish between the two, it is highly necessary for the router to recognize various pieces of information regarding the physical configuration of the wireless LAN, and any one of the pieces of information ( For example, when the distance between the routers 1 and 3) changes, it is highly likely that the frequency used for inter-area communication and intra-area communication will need to be changed accordingly. Although the usage efficiency is relatively low, it is less necessary for the router to recognize various information related to the physical configuration of the wireless LAN, and any of the various information (for example, the distance between the routers 1 and 3) changes. However, it is less necessary to change the frequency used for inter-area communication and intra-area communication accordingly. Even if it is necessary to change the communication, intra-area communication and inter-area communication are clearly distinguished, and therefore the range of influence is limited.
[0137]
(B-1) Configuration and operation of the second embodiment
In this embodiment, it is assumed that the 2.4 GHz band, which is the IEEE802.11b method, is used for intra-area communication, and the 5 GHz band, which is the IEEE802.11a standard, is used for inter-area communication.
[0138]
In this embodiment, the routing list and frequency list are basically used as they are, but the type of the frequency band to which the frequency specified by each channel number belongs is added in association with each channel number in the routing list or frequency list. Only the point is different.
[0139]
Other points may be the same as in the first embodiment.
[0140]
(B-2) Effects of the second embodiment
According to this embodiment, an effect equivalent to that of the first embodiment can be obtained.
[0141]
In addition, in this embodiment, by using different frequency bands for intra-area communication and inter-area communication, the number of channels that can be used for each increases, and the number of terminals (stations) that can be accommodated in the entire system increases. As well as transmission efficiency within each service area.
[0142]
Further, as described above, since it is less necessary for the router to recognize various information related to the physical configuration of the wireless LAN, the router setting and the like are simplified.
[0143]
Furthermore, even if any of the various information (for example, the distance between the routers 1 and 3) changes, it is less necessary to change the frequency used for inter-area communication or intra-area communication accordingly. The control when changing the frequency used for intra-area communication or inter-area communication is simplified.
[0144]
Furthermore, even if it is necessary to change, since the intra-area communication and the inter-area communication are clearly distinguished, the influence range is limited, and it can be expected that the control is simplified also in this respect.
[0145]
(C) Other embodiments
In the first embodiment, the frequency list shown in FIG. 6A is linked to the routers 1 to 3 based on the priority table shown in FIG. 6B supplied from the server 21 to the router 1. However, at least the contents of the frequency list at the beginning of operation can be statically determined in advance. Therefore, the statically determined frequency list itself is supplied from the server 21 to the router 1, and the router 1 and other routers determine frequencies to be used for intra-area communication and inter-area communication according to the frequency list. You may do it.
[0146]
In the first and second embodiments, the wireless method in the service area and the wireless method between the routers are similar (related to IEEE 802.11). However, since the two do not need to be similar, they can be configured with different communication methods.
[0147]
For example, what is shown in FIG. 8 can be used as a combination of methods related to routers (inter-area communication) and service areas (intra-area communication).
[0148]
In FIG. 8, the first combination uses IEEE802.11a (5GHz) between routers and Bluetooth (2.4GHz) within the service area, and the second combination uses B1uetooth between routers and PHS within the service area. (1.9GHz) is used, and in the third combination, IEEE802.11b (2.4GHz) is used between routers and PHS is used in the service area. In the fourth combination, IEEE802.11a is used between routers. PHS is used in each area, and in the fifth combination, Bluetooth (2.4 GHz) is used in each 802.11b (2.4GHZ) service area between routers.
[0149]
Moreover, the combination which replaced the system between the routers in the 1st-5th combination and the system in a service area as needed is also useable.
[0150]
The first to fifth combinations and their replacements provide 10 variations for the frequency design of the wireless LAN system. Which one is used depends on the traffic in each system. It can be decided according to the situation.
[0151]
Of course, a different wireless system may be used for each service area.
[0152]
Although IEEE802.11b and Bluetooth are in the same frequency band, it is possible to communicate with minimum influence by distinguishing the type of antenna.
[0153]
In the above description, there is one wireless router (router 1) connected to the wired LAN. However, two or more wireless routers connected to the wired LAN can be provided, and no wireless router can be provided. It is also possible to make a LAN system closed only by the above.
[0154]
Furthermore, in the above description, a router that performs relay processing belonging to the network layer of the OSI reference model has been described as an example. However, the present invention can also be applied to devices other than routers. For example, the present invention is also applicable to a wireless communication device corresponding to a layer 2 switch (switching hub) that performs relay processing belonging to the data link layer of the OSI reference model.
[0155]
【The invention's effect】
As described above, according to the present invention, it is possible to efficiently allocate radio frequencies to be used for communication between radio base stations in the arrangement of coverage, coverage areas, and between radio base stations. It is possible to execute the reassignment of the radio frequency in response to the factor flexibly.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of the overall configuration of a wireless LAN system according to first and second embodiments.
FIG. 2 is a schematic diagram illustrating a configuration example of a main part of a router used in the first and second embodiments.
FIG. 3 is a schematic diagram illustrating an antenna arrangement example in a router used in the first and second embodiments.
FIG. 4 is a schematic diagram showing an example of frequency arrangement in the wireless LAN systems of the first and second embodiments.
FIG. 5 is a schematic diagram illustrating a configuration example of a main part in a control unit used in the routers of the first and second embodiments.
FIG. 6 is a schematic diagram illustrating a configuration example of a table used in the first embodiment.
FIG. 7 is a schematic diagram for explaining in more detail an example of frequency arrangement in the wireless LAN system of the first embodiment;
FIG. 8 is a schematic diagram illustrating an example of a combination of methods relating to routers (inter-area communication) and service areas (intra-area communication) in another embodiment.
[Explanation of symbols]
1-3, RX1, RX2 ... router, 1A-5A ... service area, 1S-3S, 1S1 ... station, 30-36 ... radio unit, 37 ... control unit, 38 ... Ethernet interface unit, 40 ... routing processing unit, 41 ... frequency allocation part, 42 ... list update part, 43 ... list storage part.

Claims (5)

  1. A plurality of radio base stations each having a radio area not only perform radio communication with a terminal station in the radio area of the local station using the frequency in the area, but also with other adjacent radio base stations . In a wireless communication system that performs wireless communication between regions using inter-region frequencies ,
    Each radio base station is
    Information on a plurality of radio frequencies for which priorities to be used in advance are set, allocation status information on each radio frequency as the intra-region frequency and the inter-region frequency, and a frequency for assigning the intra-region frequency or the inter-region frequency Frequency management list information sharing means for exchanging frequency management list information having at least fault occurrence information indicating the presence or absence of a fault in the allocation target with the other radio base stations adjacent to each other and sharing the frequency management list information When,
    When performing radio communication and reviewing radio frequency allocation due to failure occurrence , refer to the frequency management list information and relate to the frequency allocation target in which a failure affecting the own station has occurred. Among the radio frequencies that are not radio frequencies and are not assigned to other frequency assignment targets that affect the radio communication of the local station, a radio frequency having a higher priority is selected as the intra-region frequency of the local station or between the regions. a radio frequency allocation means for allocating a frequency,
    Using the intra-regional frequency assigned by the radio frequency allocating unit , wireless communication is performed with a terminal station in the radio region of the local station, and the inter- regional frequency assigned by the radio frequency allocating unit is set. use, wireless communication system comprising: a wireless communication means for wireless communication with another wireless base station that is adjacent.
  2. 2. The wireless communication system according to claim 1, wherein the frequency management list information is preset with an intra-region frequency or an inter-region frequency for each frequency allocation target as an initial state .
  3. Wirelessly between the wireless communication unit, a wireless unit for mobile terminal for the terminal station and the wireless communication of the wireless area of the own station by using a non-directional antenna, and the other radio base station using a directional antenna A base station radio unit for communication;
    The radio frequency allocating means is
    The terminal radio unit and the base station radio unit are allowed to use the same radio frequency,
    The radio frequency having higher priority is newly allocated among the radio frequencies that are not allocated by referring to the frequency management list information when an overlapping portion of radio areas using the same radio frequency occurs. Item 3. The wireless communication system according to Item 1 or 2.
  4. The frequency management list information sharing means between said different radio base station, according to any one of claims 1 to 3, characterized in that it has an updating unit for updating the contents of said frequency management list information Wireless communication system.
  5. The wireless communication system according to any one of claims 1 to 4 and the area in the frequency, and the region between the frequencies, characterized by selecting from the different frequency bands.
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