JP2006157637A - Radio communication method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish low delay, low delay fluctuation, high throughput, and high QoS guarantee in a wireless multihop communication network. <P>SOLUTION: One radio station is defined as an incoming side gateway radio station, and another radio station is defined as an outgoing side gateway radio station. Each of the radio stations sends a packet transmitted from the present station or relayed thereby to the next radio station along with a unidirectional path where the present station is interposed between the two gateway radio stations. The outgoing side gateway radio station transfers a packet to an external network or to the incoming side gateway radio station through a path not via the radio stations in accordance with the destination of the packet transmitted from the present station or received thereby. The incoming side gateway radio station sends a packet transmitted from the present station or a packet delivered from the external network or from the outgoing side gateway radio station to the next radio station along with a unidirectional path from the present station to the outgoing side gateway radio station in accordance with the destination of that packet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication method and a wireless communication system in a wireless multi-hop communication network including a plurality of wireless stations.

  Currently, a technology called a wireless multi-hop communication network that enables communication between wireless stations that do not receive direct radio waves by configuring a network with multiple wireless stations (nodes) and relaying packets between adjacent nodes Is attracting attention.

  In a wireless multi-hop communication network, when performing real-time communication or the like, priority control or the like is performed by distinguishing between packets of real-time communication and other data packets and relaying the former with priority.

  For example, normally, after waiting for a random time at the time of relaying, as in CSMA / CA (Carrier Sense Multiple Access Avidance), which is also adopted in the MAC protocol of the IEEE802.11 standard, Observe channel usage and send / receive packets. On the other hand, in the case of a packet whose priority is controlled, the waiting time for relaying is shorter and may be a fixed time.

Further, as described in Patent Document 1, there is a method in which each wireless station on a relay route is assigned a radio access time and a radio channel by centralized control, and relays according to the assignment.
JP 2002-325273 A

  However, in a wireless multi-hop communication network, there are a plurality of wireless stations on the network, and data flows through a plurality of paths simultaneously. When relaying from a radio station to a radio station is repeated, radio resource usage areas frequently overlap between multiple paths, or uplink and downlink flows on the same path frequently overlap radio resource usage areas. Interference, signal collision, etc. occur.

  As a mechanism for avoiding radio interference and signal collision, there is a conventional method, but in CSMA / CA, it is necessary to set a longer standby time. In the disclosed technique of Patent Document 1, there are a plurality of routes to be managed. In addition, it is necessary to assign different radio access times or radio channels, and there is a problem that the communication capacity is remarkably reduced.

  In the wireless multi-hop communication network, the present invention enables simultaneous communication as much as possible with respect to a large number of connection paths while suppressing transmission delay as much as possible, and avoids radio interference and signal collision to improve communication quality. An object of the present invention is to provide a wireless communication method and a wireless communication system.

  A first aspect of the present invention is a wireless communication method comprising a plurality of wireless stations, wherein each of the wireless stations communicates with another wireless station directly or via at least one of the wireless stations, One radio station becomes an ingress gateway radio station, and at least one other radio station becomes an egress gateway radio station. Each radio station relays a packet from its own station or from its own station. To the next radio station or the egress gateway radio station along a predetermined one-way path where the own station from the incoming gateway radio station to the outgoing gateway radio station is interposed. It is characterized by sending out.

  A second aspect of the present invention is a radio communication system having a plurality of radio stations, wherein each radio station communicates with other radio stations directly or via at least one radio station, One of the radio stations is an ingress gateway radio station, and at least one other radio station is an egress gateway radio station. And the packet relayed by the local station, the next wireless station or the outgoing side along a predetermined one-way path where the local station is interposed from the incoming gateway wireless station to the outgoing gateway wireless station. The first route management means stores and manages the first route management means for storing and managing the route information transmitted to the gateway radio station, and the packet transmitted from the own station and the packet relayed by the own station. Follow the route information And having a first transmission control means for controlling transmission.

  The third aspect of the present invention is characterized in that the wireless communication system of the second aspect of the present invention is a unit system and is composed of a plurality of unit systems.

  According to the present invention, in a wireless multi-hop communication network, a wireless communication method and a wireless communication method that enables simultaneous communication as much as possible while suppressing transmission delay as much as possible, and that can improve communication quality by avoiding wireless interference and signal collision. A communication system can be provided.

(A) First Embodiment Hereinafter, a first embodiment of a wireless communication method and a wireless communication system according to the present invention will be described with reference to the drawings. The wireless communication system according to the first embodiment is a system in a wireless multi-hop communication network.

(A-1) Configuration of the First Embodiment FIG. 1 shows a configuration example of the wireless communication system 1 of the first embodiment. 1, the wireless communication system according to the first embodiment includes wireless stations A to O having a detailed configuration shown in FIG. 2, and gateway wireless stations GIn and Gout having a detailed configuration shown in FIG. In the wireless communication system of the first embodiment, two gateway wireless stations GIn and GOut are at both ends, and a plurality (15 in the example of FIG. 1) of wireless stations A to O are appropriately arranged such as a hexagonal lattice. As described above, the plurality of radio stations A to O are configured to exist on a route having the two gateway radio stations GIn and GOut as both ends.

  Here, one gateway radio station GIn is an incoming gateway radio station (hereinafter referred to as an incoming gateway radio station), and the other gateway radio station Gout is an outgoing gateway radio station (hereinafter referred to as an outgoing gateway radio station). Called).

  As described above, each of the radio stations A to O is interposed in one or more paths among a number of one-way paths from the incoming gateway radio station GIn to the outgoing gateway radio station Gout. The route information is internally managed as will be described later.

  Each of the wireless stations A to O transmits a packet that is a transmission source of the wireless station A to O to all or a part of the one-way route to the outgoing gateway wireless station Gout, and the packet relayed by itself is also sent to the outgoing gateway wireless station Gout. To all or part of the unidirectional path. It is meaningless to reach the radio station in the reverse direction, and the unidirectionality of the route is ensured.

  When the incoming gateway radio station GIn receives a packet addressed to each of the radio stations A to O and Gout from the external network or the outgoing gateway radio station Gout, the incoming gateway radio station GIn sends the packet to the outgoing gateway radio station Gout or Send to some unidirectional path. Note that packets can be transferred from the outgoing gateway radio station Gout to the incoming gateway radio station GIn via a wireless or wired network or a dedicated line other than the network shown in FIG.

  The outgoing gateway radio station Gout transfers, to the external network or the incoming gateway radio station GIn, packets addressed from A to O from the radio stations in the network shown in FIG.

  As described above, in the first embodiment, wireless multi-hop communication of packets is realized by using a one-way path from the incoming gateway radio station GIn to the outgoing gateway radio station Gout.

  FIG. 2 is a block diagram showing a basic configuration of the radio station 100 (corresponding to radio stations A to O in FIG. 1) of the first embodiment.

  2, the radio station 100 includes a radio transmission unit 101, a radio reception unit 102, a transmission control unit 103, a reception control unit 104, a synchronization control connection management unit 105, a path management unit 107, and a central control unit 108.

  The wireless transmission unit 101 transmits a wireless signal. The wireless receiving unit 102 receives a wireless signal. Note that the communication method of the wireless line is not limited.

  The transmission control unit 103 generates or updates management information in a packet such as a destination and the number of hops, and converts the packet into a radio signal. The packet to be transmitted is a packet that is sent from the central control unit 108 or is relayed by the radio station given from the reception control unit 104.

  The reception control unit 104 extracts a packet from the received radio signal and refers to management information in the packet. The reception control unit 104 gives the received packet to the central control unit 108 when the packet is destined for itself, and gives it to the transmission control unit 103 when the received packet is relayed by itself.

  The route management unit 107 manages route information (see FIG. 4) according to the destination of the packet or relay packet having the wireless station as the transmission source, and the connection destination (relay destination, transmission destination, etc.) to the transmission control unit 103. It is a notification.

  The synchronization control connection management unit 105 performs wireless media access control in synchronization with other wireless stations and gateway wireless stations. The synchronization control connection management unit 105 stores timing information (see FIG. 4) that may be transmitted by the own radio station. When the value of the internal timer or the like becomes a value specified by the timing information, the transmission control unit The transmission operation 103 is made valid. Each radio station or gateway radio station performs media access to radio resources based on the timing indicated by the synchronization control connection management unit 105.

  In a conventional radio station (not shown), a CSMA / CA control connection management unit that performs radio media access control by CSMA / CA operation is provided. In this first embodiment, a CSMA / CA control connection is provided. Instead of the management unit, the above-described synchronization control connection management unit 105 is provided.

  The central control unit 108 includes, for example, a CPU, a ROM, a RAM, and the like, and controls the above-described units 101 to 107. The central control unit 108 controls the units 101 to 107 not only during a normal communication operation but also during a communication operation for acquiring management information (such as time slot allocation information).

  FIG. 3 is a block diagram illustrating a basic configuration of the gateway radio station 200 (corresponding to the gateway radio stations GIn and GOut in FIG. 1) of the first embodiment. The gateway radio station 200 has a gateway function for connecting to an external network such as the Internet by wire or the like in addition to the function as the radio station 100.

  In FIG. 3, the gateway radio station 200 includes a radio transmission unit 201, a radio reception unit 202, a transmission control unit 203, a reception control unit 204, a synchronization control connection management unit 205, a path that are almost the same as corresponding elements in the general radio station 100. In addition to the management unit 207 and the central control unit 208, a gateway transmission unit (GW transmission unit) 209 and a gateway reception unit (GW reception unit) 210 are included.

  The GW transmission unit 209 transmits a signal via a wired connection to connect to an external network such as the Internet. The GW reception unit 210 transmits a signal via a wired connection to connect to an external network such as the Internet. The GW transmission unit 209 and the GW reception unit 210 receive media access to an external network based on the timing of CSMA / CD control in the case of wired connection indicated by the synchronization control connection management unit 205. Is to execute.

  FIG. 3 shows the detailed configuration of the gateway radio station that can be either an ingress gateway radio station or an egress gateway radio station. However, if it is applied only to the ingress gateway radio station GIn, the configuration of FIG. From the configuration of FIG. 3, the wireless transmission unit 201 and the GW reception unit may be configured by excluding the wireless reception unit 202 and the GW transmission unit 209 from the configuration of FIG. The unit 210 may be excluded from the configuration.

  FIG. 4 shows slot allocation of link operation timing for a link between two gateway radio stations and two radio stations among a plurality of radio stations in the arrangement of the gateway radio station and the general radio station shown in FIG. It is explanatory drawing.

  In FIG. 4, the slot assignment is divided into two slot sets X and Y.

  In the slot set X, the number of hops from the incoming gateway radio station GIn is approximately small on the route having the two gateway radio stations GIn and GOut as both ends in ascending order of the slot numbers assigned 01 to 10. Links are arranged in order.

  The slot group Y is obtained by shifting the arrangement of the slot group X by several (the one in FIG. 4 is shifted by 5 time slots). The amount of deviation of the slot set Y from the slot set X is such that, for each slot number, any one of the links described in the corresponding slot number frame of one slot set X and the slot set Y The same slot is selected so that any one of the links described in the corresponding slot number frame can be used at the same time, and such a relationship is established. The link in the number frame is selected.

  Each radio station 100 (A to O) and each gateway radio station 200 (GIn, GOut) determine the timing for transmitting a radio signal based on the time slot allocation information shown in FIG. In the example of FIG. 4, one hop signal is transferred for each slot while selecting one link from a plurality of links fixedly assigned from the gateway radio station GIn to the gateway radio station GOut. With this operation, the incoming gateway radio station GIn functions as an incoming gateway, and the outgoing gateway radio station GOut functions as an outgoing gateway.

  The information shown in FIG. 4 defines not only time slot allocation but also the counterparts with which each radio station 100 (A to O) and each gateway radio station 200 (GIn, GOut) can communicate packets. Yes. For example, the wireless station B can receive a packet only from the wireless station A and can transmit a packet to the wireless stations F and C.

  Note that each wireless station 100 (A to O) and each gateway wireless station 200 (GIn, GOut) are allowed only one-way communication in which a packet can be transmitted only to a communication partner as shown in FIG. Communication for link establishment and disconnection, such as exchange of link requests and link acceptance requests, necessary for executing such communication, is made possible in both directions.

  Each radio station 100 (A to O) and each gateway radio station 200 (GIn, GOut) store and hold all of the information shown in FIG. 4 or a part related to the own station.

  In FIG. 4, the slot set X and the slot set Y describe the same link sequence except for the timing difference, but they may be different. For example, the slot set X is a set describing a sequence of links in which only GIn → A is the first link assignment, and the slot set Y is a set describing a sequence of links in which only GIn → E is the first link assignment. (However, the timing deviation is the same as in FIG. 4).

(A-2) Operation of the First Embodiment Next, the operation of the wireless communication system of the first embodiment will be described. In the following description of the operation, the arrangement of the radio station 100 and the gateway radio station 200 is assumed to be the arrangement shown in FIG.

  First, a communication operation for allowing all the radio stations 100 (A to O) and the gateway radio station 200 (GIn, GOut) to share the same information will be described with reference to FIG. 5 similar to FIG.

  For example, in such a case, the wireless station that supplies such information requests the incoming gateway wireless station GIn to broadcast the information by a communication operation between two stations described later.

  When the incoming gateway radio station GIn receives a request for broadcast transmission of such information, it establishes a link at the timing assigned to itself and sends the broadcast packet to the next radio on all routes. Transmit to stations A and E. For example, if the incoming gateway radio station GIn receives the request at the timing of slot number 03, it transmits a broadcast packet at the timing of slot number 06, which is its own transmission timing in slot set Y.

  The wireless stations A and E that have received the broadcast packet also transmit the broadcast packet after establishing a link at the timing of slot number 07. Similarly, wireless stations B and D transmit a broadcast packet after establishing a link at the timing of slot number 08, and wireless stations F, C, and L establish a link at the timing of slot number 09. Broadcast station, wireless stations G, I and K establish a link at the timing of slot number 10 and then transmit the broadcast packet. Radio stations H and J link at the timing of slot number 01. After establishing the broadcast packet, the wireless stations M and O establish a link at the timing of the slot number 02 and transmit the broadcast packet, and the wireless station N establishes the link at the timing of the slot number 03. The broadcast packet is transmitted after being established.

  As described above, all the radio stations 100 (A to O) and the gateway radio stations 200 (GIn, GOut) receive the information within the eight hop period after the incoming gateway radio station GIn transmits the broadcast packet. To do.

  Next, a communication operation from one wireless station to another wireless station (communication operation between two stations) will be described with reference to FIG. Here, the wireless station M is a packet transmission source, and the wireless station H is a packet destination. FIG. 5 shows the selected time slots and links.

  The transmission timing of the radio station M is slot number 07 for slot set X and slot number 02 for slot set Y. If the wireless station M needs to transmit such a packet at the slot number 04, the wireless station H transmits the target packet to the wireless station N after establishing a link at the timing of the slot number 07. .

  Since the wireless station N is not addressed to itself, it establishes a link at the timing of the slot number 08 and relays the target packet to the outgoing gateway wireless station GOut. The relay transmission may be pure relay transmission or relay transmission that adds data to the destination.

  Since the outgoing gateway radio station GOut is not addressed to itself but is addressed to the radio station H in the network, the outgoing gateway radio station GOut is transmitted to the incoming gateway radio station GIn via an external network or a dedicated line. Here, it is assumed that the above-mentioned packet arrives at the entrance gateway radio station GIn at the timing of the slot number 10.

  The incoming gateway radio station GIn performs relay transmission because the target packet is not addressed to itself. In this case, the ingress gateway radio station GIn can transmit to both the radio station A and the radio station E, but one route corresponding to the destination of the target packet (in the case of the arrangement shown in FIG. 1, to the radio station A) Route). For example, the incoming gateway radio station GIn transmits the target packet to the radio station A after establishing a link at the timing of the slot number 01. As described above, all of the radio stations 100 (A to O) and the gateway radio stations 200 (GIn, GOut) also have information on the destination of the packet to be relayed and to which radio station the route information is transmitted. Hold as part.

  The wireless station A transmits a target packet to be relayed to the wireless station B after establishing a link at the timing of the slot number 02.

  There are two routes with a minimum number of hops of 3 from the wireless station B to the wireless station H. Therefore, information is managed using one as a selected route and the other as an alternative route. For example, when a packet destined for the wireless station H is received, if the route to the wireless station F is a selected route, the link is attempted to be established at the timing of slot number 03. Here, when the link on the selected route cannot be established, the target packet is transmitted to the wireless station C after establishing the link with the wireless station C on the alternative route. For example, at this time, the route information is updated with the route to the wireless station C as the selected route and the route to the wireless station F as the alternative route. It is preferable to select a time slot time so that there is no problem even if switching to such an alternative route is executed. However, if transmission at the timing of the current slot number 03 assigned to itself is impossible, the timing of slot number 08 assigned to itself in the other slot set Y or the slot number 03 Relay transmission to the wireless station C is performed at the next timing.

  Thereafter, the wireless station C transmits a target packet to the wireless station I after establishing a link at the timing of the slot number 04, and the wireless station I establishes a link at the timing of the slot number 05 and then transmits the target packet. To the wireless station H, and since the wireless station H is addressed to itself, the information of the packet is taken inside.

  Note that when the wireless station H is the packet transmission source and the wireless station M is the packet destination, which is the reverse of the above case, the timing at which the wireless station H is allocated to itself (slot number 01 or 06) If the packet is transmitted to the wireless station M, the communication is immediately terminated.

  Further, in the case of communication from the wireless station in the wireless communication system of the first embodiment to the external network, the packet from the wireless station is transferred to the outgoing gateway wireless station GOut in the same manner as described above. The outgoing gateway radio station GOut performs a transmission operation to the external network.

  Further, a packet from the external network to the radio station in the radio communication system of the first embodiment is given to the ingress gateway radio station GIn, and is transferred from the ingress gateway radio station GIn to the destination radio station. The operation is the same as in the case of communication between the two stations described above.

  The slot allocation information as shown in FIG. 4 may be created by a network administrator and set in the radio station 100 or the gateway radio station 200. However, by doing the following, The wireless communication system can acquire autonomously. The following creation operation is executed, for example, at the time of media access control (MAC) operation as well as system startup.

[0] Initial condition A radio station and a gateway radio station are physically arranged as shown in FIG. 1, for example.

[1] Media Access Control Layer Setting Preparation Operation 1.1: The incoming gateway radio station GIn broadcasts a HELLO packet [source: GIn destination: GOUT relay: [] hop count: 0].

  1.2: The wireless station Ni1 that has received the HELLO packet from the incoming gateway wireless station GIn broadcasts the HELLO packet [source: GIn destination: Gout relay [Ni1] hop count: 1].

  Similarly, the wireless station Ni (m + 1) that receives the HELLO packet [source: GIn destination: GOut relay: [Ni1, Ni2, Ni3,..., Nim] hop count: m] receives the HELLO packet [source: GIn Destination: GOut Relay: [Ni1, Ni2, Ni3,..., Nim, Ni (m + 1)] The number of hops: m + 1] is broadcast.

  1.3: Gateway wireless station GOut that has received a number of HELLO packets [source: GIn destination: GOut relay: [Ni1, Ni2, Ni3,..., Nin] hop count: n] Based on the number of hops, a route table is created, link information is newly created or updated, and the link information is transferred to GIn via an external network or the like.

  1.4: The gateway radio station GIn that has received the link information, if the link information is first acquired, or if the link information has been updated from the existing link information, Transmit to the next wireless station on the GOut path.

  Similarly, the wireless station that has received the link information also transmits the link information to the next wireless station on the GIn → GOut route.

  By the above 1.1-1.6, the link information showing the arrangement relationship as shown in FIG. 1 is obtained.

[2] Slot allocation This slot allocation process may be executed by a specific station such as an ingress gateway radio station GIn, an egress gateway radio station GOut, or a management station (not shown), and includes a plurality of radio stations (including gateway radio stations). However, the execution subject is not limited. In this slot assignment, the information obtained in the above-described setting preparation operation [1] of the media access control layer is processed without performing communication.

  2.0: For each wireless station, the route with the shortest number of hops including the wireless station on the route from the incoming gateway wireless station GIn to the outgoing gateway wireless station GOut is the preparation for setting the media access control layer described above. Obtained in operation [1]. In the case of FIG. 1, the number of hops of the route with the shortest hop number is 8 for each of all the wireless stations A to O. However, depending on the arrangement of the wireless stations, the number of hops of each wireless station can be somewhat different. is there. In addition, there may be a plurality of shortest hop paths for each wireless station (for example, wireless station C has four paths and wireless station F has one path).

  2.1: Follow the link of each route with the shortest number of hops one hop at a time, and link between wireless stations at that number of hops while eliminating duplication of assignment of the same link in each route. Allocate to enter slot (slot number).

    (A) At this time, when the number of hops to a link having the same wireless station as the transmission side differs depending on the route (this does not occur in the arrangement of FIG. 1), the route with the larger number of hops Assign the link to the slot first. The route with the smaller number of hops waits until assignment to the slot of the link having the same wireless station as the transmission side is performed, and the subsequent route portion is again assigned.

    (A) When there are a plurality of routes including the link having the same wireless station as the transmission side as a route with the shortest hop count for a certain wireless station, the different wireless links are assigned to slots.

  A set of slot assignments formed by the above processing is referred to as a slot set X. However, at this stage, slots with slot numbers 09 and 10 are not formed.

[3] Confirmation of Simultaneously Available Links In order to form the slot set Y, confirmation of links that can be used simultaneously without causing problems such as interference even if they are simultaneously used is performed. Since this operation has a problem of interference or the like, it becomes a cooperative work of all the radio stations and gateway radio stations. A station that controls such collaborative work with leadership is a specific station such as the gateway radio station Gin.

  3.1.1: Search for a link that can be used simultaneously with the link having the gateway radio station Gin as a transmission source. A link where the signal from the gateway radio station GIn is not an interference wave (for example, a link used at a position where the relative signal intensity is −10 dB or less as the receivable signal intensity) is searched. While performing packet transfer on the link from the gateway radio station Gin, it is checked whether carrier sense is performed in another radio station, and the link between the radio stations that have not been carrier sensed is a link made up of the gateway radio. Whether or not simultaneous use is determined based on whether or not packet transfer at the same time as packet transfer on the link from the station Gin succeeds. For example, in this search, links F → G, G → H, I → H, I → J, L → K, K → J, H → M, J → O, M → N, O → N, N → Assume that GOut becomes a link that can be used simultaneously.

  3.1.2: A link that can be used simultaneously with a link (radio station A → B, E → D) in FIG. Explore. The specific search method is the same as in the case of 3.1.1 described above. For example, in the search at this time, it is assumed that links H → M, J → O, M → N, O → N, and N → GOut are links that can be used simultaneously.

  3.1.3: A link having a transmission source of a two-hop wireless station from the incoming gateway wireless station GIn on the GIn → GOOut route (in FIG. 4, wireless stations B → F, B → C, D → C, D → L) Search for links that can be used simultaneously. The specific search method is the same as in the case of 3.1.1 described above. For example, in the search at this time, it is assumed that link N → GOOut is a link that can be used simultaneously.

  3.1. n: Searches for a link that can be used simultaneously with a link having a transmission source of a radio station of (n−1) hops from the incoming gateway radio station GIn on the GIn → GOut route in the same manner as described above.

  3.1.1-3.1. The operation of n is repeated until it becomes impossible to search for links that can be used simultaneously. Incidentally, in the arrangement example of FIG. 1, links that can be used simultaneously can be searched when n = 3, but links that can be used simultaneously cannot be searched when n = 4.

  3.2: A separate table (a table for slot set Y) is provided alongside slot set X, and links that can be used simultaneously are allocated to the same slot number. At this time, the links that can be used simultaneously in 3.1 to 3.3 are allocated by narrowing down to links of different routes one by one. Alternate links are placed in the same slot. This is a slot set Y. Thereby, in FIG. 4, slot numbers 01 to 08 are filled.

  3.3: A slot is added to a link included in the slot set X and is not allocated to the slot set Y, and a link is allocated using the slot set Y. As a result, slot numbers 09 to 10 are added in FIG.

  The time slot allocation information created as described above is used to control the transmission timing of each station during the communication operation as described above.

(A-3) Effect of First Embodiment Conventionally, since radio resources are allocated to links by CSMA / CA control, a lot of time when radio resources are not used for any link occurs, resulting in a large overhead. It was.

  In the wireless communication system of this embodiment, the link use timing is selectively determined from a fixed combination as described above, thereby reducing the throughput due to the overhead generated in the conventional CSMA / CA control. By avoiding an increase in delay, throughput can be improved and delay can be shortened.

  In other words, in this radio communication system, the following effects can be obtained by repeating transfer between two gateway radio stations in a certain direction in the geographical area where the gateway radio station and the radio station are arranged.

  1. It is possible to avoid collision between the use of radio resources at the time of uplink and the use of radio resources at the time of downlink, and it is possible to improve throughput and shorten delay.

  2. Coordination with the use of radio resources in adjacent areas can be facilitated, and the spatial reuse efficiency of radio resources can be improved and the throughput can be improved. This is because the use of radio resources transitions in a certain direction even when viewed from adjacent areas, so that spatial reuse of radio resources becomes easy.

  3. When each wireless station is connected to an external network such as the Internet, the sum of delays required for signal uplink and downlink is a constant value. As a result, the radio station having the maximum sum of the uplink and downlink delays is not much different from the average delay. Conventionally, a radio station far from a gateway has a larger delay required for signal up and down than a radio station close to the gateway, and the sum of the delay required for uplink and downlink is the distance from the gateway. Therefore, there was a radio station having a delay approximately twice as large as the average delay. As a result, the delay can be shortened.

  4). By using two gateways, signals originating from and destined for the gateway, which are likely to become bottlenecks in throughput and delay, can be distributed, the load can be reduced, throughput can be improved, and delay can be reduced. .

(B) Second Embodiment Next, a second embodiment of the wireless communication method and the wireless communication system according to the present invention will be described with reference to the drawings.

  FIG. 6 is an explanatory diagram illustrating an arrangement example of wireless stations and gateway wireless stations in the wireless communication system according to the second embodiment.

  6, the wireless communication system according to the second embodiment includes a plurality of subnets a1, a2, b1 to b3, c1 to c3, d2, d3,.

  Each subnet is described by taking the subnet b1 as an example. Two gateway radio stations b1 and b2 whose detailed configuration is shown in FIG. 3 are arranged at both ends, and 15 radio stations whose detailed configuration is shown in FIG. A plurality of radio stations are configured to exist on a path having two gateway radio stations as both ends.

  The subnets are spread out in a plane in the vertical and horizontal directions, and each radio station belongs to one of the subnets, while each gateway radio station is a common element of the two subnets. For example, the gateway radio station b2 is an outgoing gateway radio station in the subnet b1 and an incoming gateway radio station in the subnet b2. From another point of view, the subnet b2 also has an ingress gateway radio station b2 and an egress gateway radio station b3, and is similar to the radio communication system of the first embodiment.

  FIG. 7 is a table in which channels are assigned to each subnet in the wireless communication system of the arrangement example of FIG. For example, when four channels are available, subnets are assigned to the four channels so that they are not consecutively arranged vertically and horizontally. Here, the difference between the channels may be different carrier frequencies, different spread codes in spread spectrum communication, and different factors that can distinguish the channels depending on the applied communication method. It should be.

  FIG. 8 is a table in which, in the wireless communication system of the arrangement example of FIG. 6, when each subnet has the configuration as shown in FIG. Since the same channel is reused in different subnets, the case where the spatial reuse of radio resources is not performed in the same subnet is shown in order to maintain the desired wave gain with respect to the interference wave of 10 dB (slot set is 1). set). Even in this case, the creation of the slot allocation table is performed in accordance with the procedure for creating the slot set X in the description of the operation in the first embodiment.

  If the subnet size is small and the same time slot is assigned to each subnet, and the radio wave of the nearby subnet becomes an interference wave, different time slots are assigned between the neighboring subnets. Like that. In other words, the same time slot can be assigned to each subnet when there is no interference between subnets. Whether or not an interference wave is generated is determined as in the above-described simultaneous link confirmation operation. In this case, it is preferable that a gateway radio station common to both subnets takes the initiative of this confirmation operation.

  Other configurations and operations are substantially the same as those in the first embodiment, and thus description thereof is omitted.

  In the wireless communication system according to the second embodiment, as described above, the timing of using the link is selectively determined from a fixed combination, and channel assignment to the subnet is fixed. Thus, it is possible to improve throughput and shorten delay by avoiding a decrease in throughput, an increase in delay, and radio interference with an adjacent subnet caused by overhead generated in the conventional CSMA / CA control.

  In other words, in this wireless communication system, the following effects can be obtained in addition to the effects described in the first embodiment.

  Efficient radio resources when constructing a wireless communication system that covers multiple geographical areas in a wide area environment such as stadiums, theme parks, and urban areas where multiple gateway wireless stations can be installed. Space reuse can be realized.

(C) Other Embodiments In the description of each of the above-described embodiments, various modified embodiments have been referred to. However, modified embodiments as exemplified below can be given.

  In the first embodiment, two slot groups are assigned. However, when there are many links that can be used simultaneously, three or more slots may be assigned. For example, in the search for a link that can be used simultaneously, how many sets are assigned according to the value of n at which no link can be found, and the amount of deviation in the slot set is determined in advance and three or more sets are assigned. Anyway.

  In the second embodiment, one slot set is shown for each subnet. However, two or more slot sets may be assigned to each subnet.

  Further, in the first embodiment, the same channel is used in the wireless communication system, and in the second embodiment, the same channel is used in the subnet. Multiple channels may be used in the system or subnet.

  Furthermore, in the first embodiment, communication in only the direction from the first gateway radio station (incoming gateway radio station) to the second gateway radio station (outgoing gateway radio station) is permitted. However, in addition to this, communication in the direction from the second gateway radio station to the first gateway radio station may be permitted. For example, the channel (for example, carrier frequency) is changed between the former direction and the latter direction so as to avoid interference in both directions.

  Further, in the first embodiment, the entry gateway radio station and the exit gateway radio station are shown one by one, but if the direction from the entrance gateway radio station to the exit gateway radio station can be secured, There may be two or more incoming gateway wireless stations and outgoing gateway wireless stations. For example, in this case, for example, one set of slots assigned with time slots for each combination of an incoming gateway radio station and an outgoing gateway radio station is obtained, and depending on whether each link can be used simultaneously, Shift the phase of.

  In the first embodiment described above, the simultaneous availability of each link is determined according to the measurement result obtained by executing the actual communication. However, the arithmetic processing is performed according to the distance between the wireless stations. You may make it decide in.

It is explanatory drawing of the example of a radio station arrangement | positioning in a radio | wireless communications system in 1st Embodiment. It is a block which shows the structure of the radio station of 1st Embodiment. It is a block which shows the structure of the gateway radio station of 1st Embodiment. It is explanatory drawing which shows the example of allocation of the time slot to each radio station of 1st Embodiment. It is explanatory drawing of the time slot and link which function by communication between two stations of 1st Embodiment. It is explanatory drawing of the example of a radio station arrangement | positioning in a radio | wireless communications system in 2nd Embodiment. It is explanatory drawing which shows the example of allocation of the channel of each subnet of 2nd Embodiment. It is explanatory drawing which shows the example of allocation of the time slot of each subnet of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless station, 101, 201 ... Wireless transmission part, 102, 202 ... Wireless reception part, 103, 203 ... Transmission control part, 104, 204 ... Reception control part, 105, 205 ... Synchronization control connection management part, 107, 207 ... route management unit, 108, 208 ... central control unit, 200 ... gateway radio station, 209 ... gateway transmission unit (GW transmission unit), 210 ... gateway reception unit (GW reception unit).

Claims (15)

A wireless communication method comprising a plurality of wireless stations, wherein each wireless station communicates with another wireless station directly or via at least one wireless station,
At least one of the radio stations becomes an ingress gateway radio station, and at least one other radio station becomes an egress gateway radio station,
Each of the wireless stations has a predetermined direction in which the own station from the incoming gateway wireless station to the outgoing gateway wireless station intervenes a packet transmitted from the own station or a packet relayed by the own station. Transmitting to the next wireless station or the outgoing gateway wireless station along the route.   The egress gateway radio station transfers the source packet or the received packet to the external network according to the destination of the source packet or the received packet, or the ingress side gateway radio station The wireless communication method according to claim 1, wherein the wireless communication method is transferred to a gateway wireless station through a route not via each wireless station.   The ingress gateway radio station sends a packet sent from its own station, a packet received from an external network, or a packet received from the egress gateway radio station from the own station according to the destination of the packet. The wireless communication method according to claim 1 or 2, wherein the wireless communication method transmits to the next wireless station along a predetermined one-way route to the outgoing gateway wireless station. A wireless communication system having a plurality of wireless stations, wherein each wireless station communicates with other wireless stations directly or via at least one wireless station;
At least one of the above radio stations is an ingress gateway radio station, and at least one other radio station is an egress gateway radio station,
Each of the above radio stations
The next packet along the predetermined one-way route where the own station is mediated by the own station from the incoming gateway radio station to the outgoing gateway radio station. First route management means for storing and managing route information transmitted to the wireless station or the outgoing gateway wireless station;
A first transmission control unit configured to control transmission of the packet transmitted by the own station and the packet relayed by the own station according to the path information stored and managed by the first path management unit. Wireless communication system. The outgoing gateway radio station is
Depending on the destination of the source packet or the received packet, the local station forwards the source packet or the received packet to an external network, or sends each radio station to the incoming gateway radio station. A second route management means for storing and managing route information to be transferred by a route that does not pass through;
5. The second transmission control means for controlling transmission of the packet of the transmission source or received by the own station according to the path information stored and managed by the second path management means. The wireless communication system according to 1. The incoming gateway radio station is
A packet sent from the local station to the outgoing gateway radio station according to the destination of the packet of the packet sent from the local station, the packet received from the external network, or the packet received from the outgoing gateway radio station. Third route management means for storing and managing route information to be sent to the next wireless station along the one-way route;
The local station controls transmission of packets sent from the source network, packets received from the external network, or packets received from the outgoing gateway radio station according to the path information stored and managed by the third path management means. 6. The wireless communication system according to claim 4, further comprising third transmission control means.   The route information stored and managed by the first route management means is the number of relays in the one-way route from the incoming gateway wireless station to the outgoing gateway wireless station via its own station. The wireless communication system according to claim 4, wherein the wireless communication system is minimized.   During the media access control operation, a route search control packet is broadcast from the ingress gateway radio station to the egress gateway radio station, and each radio station is described in the route search control packet during transfer. 8. The link information of the network is collected by updating the route information, and the route information stored and managed by the first to third route management means is obtained. Wireless communication system.   All or a part of the first to third route management means also manage a partial alternative route for a predetermined one-way route from the incoming gateway wireless station to the outgoing gateway wireless station. The wireless communication system according to any one of 4 to 8, wherein all or part of the first to third transmission control means switches to an alternative route for transmission when the main route state deteriorates.   Communication timings of the entrance gateway radio station, the radio stations, and the exit gateway radio station related to a certain one-way path from the entrance gateway radio station to the exit gateway radio station In accordance with the progression of the route, each time slot is different, and the incoming gateway radio station, each radio station, and the outgoing gateway radio station each store and manage its communication timing. The wireless communication system according to claim 4, further comprising a management unit.   The set of the communication timings that are different for each time slot is prepared in a plurality of sets that are shifted by a timing that can eliminate mutual interference in each set. Wireless communication system.   12. A radio communication system comprising the radio communication system according to claim 4 as a unit system and a plurality of unit systems.   The wireless communication system according to claim 12, wherein a set of communication timings used in each of the plurality of unit systems is the same in the plurality of unit systems.   14. The wireless communication system according to claim 12, wherein each of the plurality of unit systems is assigned different channels to adjacent unit systems that cannot be used simultaneously when the same channel is used. . 15. The radio communication system according to claim 12, wherein an entrance gateway radio station of a certain unit system operates as an exit gateway radio station of an adjacent unit system.

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