JP6082994B2 - Transmission route determination method and wireless communication system - Google Patents

Description

  The present invention relates to a communication technique in a wireless communication network, and more particularly to a communication technique in a wireless communication network in which a relay station exists between a transmitting station and a receiving station.

In recent years, cooperative relay transmission in which a relay station is introduced between a transmitting station and a receiving station has attracted attention in order to improve the communication quality of a wireless communication network. From the viewpoint of a radio link, signal processing techniques in various physical layers in cooperative relay transmission, such as AF (Amplify and Forward), DF (Decode and Forward), and distributed self-space code, have been proposed.
On the other hand, from the viewpoint of a wireless communication network constructed by a large number of wireless links, various protocols in a medium access control (MAC) layer in cooperative relay transmission have been proposed. In this way, studies for introducing cooperative relay transmission are being developed in each layer of the communication network.

In general, cooperative relay transmission is multi-hop transmission of two or more hops. In multi-hop transmission, not only a one-hop wireless medium is reserved as in single-hop transmission, but a wireless medium is reserved over a multi-hop wide area.
As a one-hop wireless medium reservation method, see the IEEE (the Institute of Electrical and Electronic Engineers) 802.11 standard (see Non-Patent Document 1, for example), which is widely used as a standard for a wireless local area network (LAN). There is a DCF (Distributed Coordination Function) system defined in (1).
As a technique for reserving a wireless medium (wireless resource) over a multi-hop wide area assuming an arbitrary number of hops, there is an EMAC method (see, for example, Non-Patent Document 2).

IEEE 802.11-2007, IEEE Standard for Information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements-Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications S. Du, Y. Sun and D.B. Johnson, “EMAC: An asynchronous routing-enhanced MAC protocol in multihop wireless networks,” In Proc. GLOBECOM 2010, Miami, FL, USA, pp. 1-6, Dec. 2010.

  The DCF method is a technology that originally assumes transmission of one hop. In order to perform end-to-end data transmission from a traffic generation terminal to a destination terminal by multi-hop transmission using the DCF method, it is necessary to perform random medium access at each hop. For this reason, in the DCF method, a large overhead is caused due to collision caused by medium access at each hop, random backoff control, and the like, resulting in waste of radio resources.

  In addition, the EMAC scheme reserves a wireless medium over an end-to-end wide area assuming an arbitrary number of hops, and in the reserved wireless medium, through a single or a plurality of relay terminals from a traffic generation terminal, This is a technique for transmitting data to the destination terminal in an end-to-end manner. This eliminates the need for random medium access at each hop on the multi-hop transmission path, thereby reducing overhead that is a problem with the DCF method and improving transmission efficiency.

  However, both Non-Patent Documents 1 and 2 are premised on the use of a predetermined multi-hop route determined by an existing routing technique, and are not optimized for a multi-hop route considering application of cooperative relay transmission. On the other hand, many existing cooperative relay transmission technologies completely discard the conventional routing technology, and it is difficult to achieve consistency with the conventional network layer technology. In summary, in multi-hop transmission, there is a problem that there is no communication method that is consistent with each other while taking advantage of each of the cooperative relay transmission technology and the routing technology.

  In view of the above circumstances, the present invention provides a transmission route determination method for performing communication consistent with each other while taking advantage of each of the cooperative relay transmission technology and the routing technology in multi-hop transmission in a wireless communication network, and An object is to provide a wireless communication system.

  One aspect of the present invention is a transmission route determination method executed by a wireless communication system having a plurality of wireless stations, wherein a transmission frame between a start station and an end station in a transmission route of multihop transmission composed of the wireless stations. The radio station that is a relay station that relays the relay station and the radio station that is the end station receive a control frame from another radio station on the start station side in the transmission route, and directly based on the received control frame A transmission quality calculation step of calculating transmission quality of transmission and calculating transmission quality of relay transmission and transmission quality of cooperative relay transmission based on transmission quality in the other radio station set in the control frame; When the control frame is received from another radio station on the start station side having a radio link with the own station in the transmission route, the transmission quality calculation scan is performed. A route reselecting step of selecting a transmission method based on the transmission quality calculated in the step, and resetting the transmission route based on the selected transmission method; and And a control frame transmission step of transmitting the transmission quality set in the control frame when the transmission method selected in the reselection step is used.

  One aspect of the present invention is the transmission route determination method described above, wherein a window is sequentially slid by a slide width from the start station to the end station side in the transmission route of multi-hop transmission, and the window in the window The radio station that is a relay station and the radio station that is the end station execute the transmission quality calculation step when the control frame is received from another radio station on the start station side in the window, It is characterized by.

  One aspect of the present invention is the above-described transmission route determination method, wherein the wireless station in the transmission route reconfigured in the route reselection step is reconfigured by the selected transmission method. The method further comprises a multi-hop transmission step of performing multi-hop transmission between the start station and the end station according to a transmission route.

  Another aspect of the present invention is the above-described transmission route determination method, wherein the wireless station that is the start station acquires a communication right according to a medium access control method, and the communication right acquisition step. And further comprising: a pre-processing start step for transmitting a control frame when a communication right is acquired, and a communication right release step for releasing the communication right when the multi-hop transmission step is completed. To do.

  One embodiment of the present invention is a wireless communication system having a plurality of wireless stations, wherein a relay station relays a transmission frame between a start station and an end station in a multihop transmission transmission route including the wireless stations. The radio station that is the end station and the radio station that is the end station receive control frames from other radio stations on the start station side in the transmission route, and improve the transmission quality of direct transmission based on the received control frames. A transmission quality calculation unit that calculates transmission quality of relay transmission and transmission quality of cooperative relay transmission based on transmission quality in the other radio station set in the control frame, and the local station in the transmission route The transmission quality calculated in the transmission quality calculation unit when the control frame is received from another radio station on the start station side having a radio link with And a route reselection unit that reconfigures the transmission route based on the selected transmission method, and the wireless station that is the relay station selects the route reselection unit. A wireless communication system, further comprising a control frame transmission unit configured to transmit the transmission quality when the transmission method is used in the control frame.

  According to the present invention, in multi-hop transmission in a wireless communication network, it is possible to determine a transmission route for performing communication consistent with each other while taking advantage of each of the cooperative relay transmission technology and the routing technology.

1 is a configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a block diagram which shows the internal structure of the radio station by the embodiment. It is a figure which shows the flow of the whole process in the radio | wireless communication network by the embodiment. It is a figure which shows the structural example of the multihop transmission by the same embodiment. It is a figure which shows the case where a sliding window is introduced into the example of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a wireless communication system according to an embodiment of the present invention. The wireless communication network realized by the wireless communication system shown in the figure is configured by a plurality of wireless stations 10 and performs multi-hop transmission. Of the radio stations 10 in the radio communication system, the radio stations T1 and T2 belong to a radio communication network and are any one radio station pair that performs communication. The communication direction between the radio station T1 and the radio station T2 may be the direction from the radio station T1 to the radio station T2, the direction from the radio station T2 to the radio station T1, or the two-way communication between the radio station T1 and the radio station T2. Either of these may be used. In addition, among the radio stations 10 in the radio communication system, the radio stations R1, R2,..., Rp (p is an integer of 1 or more) are relay stations that cooperate in communication between the radio station T1 and the radio station T2 in the radio communication network. It is. The radio stations 10 other than the radio stations T1, T2, and R1 to Rp are radio stations that do not cooperate with communication between the radio stations T1 and T2 and are not selected as relay stations. Note that any of the wireless stations 10 described above need not be limited to AP (Access Point) or STA (Station).

  FIG. 2 is a block diagram showing an internal configuration of the radio station 10, and only functional blocks related to the present embodiment are extracted and shown. As shown in the figure, the radio station 10 includes an antenna 11, a radio communication unit 12, and a communication control unit 13. The antenna 11 transmits and receives radio signals. Although the figure shows a case where a plurality of antennas 11 are provided, one antenna may be used. The wireless communication unit 12 performs wireless signal transmission processing, reception processing, and relay processing. In the relay process, data obtained by demodulating / decoding the radio signal received by the antenna 11 may be encoded / modulated by the transmission process and output to the antenna 11, or the radio signal received by the antenna 11 may be output. May be amplified and output to the antenna 11.

  The communication control unit 13 controls the wireless communication unit 12 and includes a route selection unit 14, a communication right acquisition unit 15, a preprocessing unit 16, and a transmission control unit 17. The route selection unit 14 determines a transmission route for multihop transmission using an existing routing technique. The communication right acquisition unit 15 acquires the communication right by the existing communication right acquisition control.

The preprocessing unit 16 resets the transmission route for multihop transmission determined by the route selection unit 14 as preprocessing for multihop transmission. The preprocessing unit 16 includes a transmission quality calculation unit 161, a route reselection unit 162, and a control frame transmission unit 163. The transmission quality calculation unit 161 performs direct transmission based on a control frame relayed along the transmission route of the multi-hop transmission determined by the route selection unit 14 or a control frame received by a wireless link not included in the transmission route. The transmission quality is calculated, and the transmission quality of relay transmission and the transmission quality of cooperative relay transmission are recursively calculated. The route reselection unit 162 selects the best transmission method based on the transmission quality calculated by the transmission quality calculation unit 161, and selects the transmission route of multihop transmission determined by the route selection unit 14 based on the selected transmission method. Reset it. The control frame transmission unit 163 sets transmission information on the transmission quality when the transmission method selected by the route reselection unit 162 is used, and transmits the control frame.
The transmission control unit 17 controls the wireless communication unit 12 to perform multihop transmission according to the transmission route reset by the route reselection unit 162 and the selected transmission method. Further, the transmission control unit 17 controls transmission of a response indicating success or failure of multihop transmission.

FIG. 3 is a diagram showing the flow of overall processing in the wireless communication network of this embodiment.
In advance, the route selection unit 14 of each radio station 10 determines the transmission route of the multi-hop transmission by controlling the wireless communication unit 12 and transmitting / receiving a control frame for selecting the transmission route of the multi-hop transmission. Keep it. An existing routing technique can be used to determine the transmission route of this multi-hop transmission. Hereinafter, the determined transmission route of multi-hop transmission is referred to as a “default route”.

  In a wireless communication network, wireless stations 10 having untransmitted transmission frames compete for communication rights according to an existing medium access method. For example, in the case of a wireless LAN (Local Area Network), the communication right acquisition unit 15 of each wireless station 10 having an untransmitted transmission frame is based on a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method. Compete for communication rights. As a result, the communication right acquisition unit 15 of the wireless station 10 that desires multi-hop transmission acquires the communication right in the wireless communication network to which the own station belongs (step S1). For example, the wireless station T1 in FIG. 1 acquires a communication right within the wireless communication network.

  Next, the wireless station 10 constituting the predetermined route includes a start station (transmitting station) that is a wireless station 10 of multihop transmission that has acquired a communication right, and an end station (reception station) that is a wireless station 10 that is the destination of multihop transmission. A route reselection procedure is performed along a predetermined route as pre-processing for multi-hop transmission so that communication can be performed with a station). In this route reselection procedure, a part or all of a multi-hop transmission start station (wireless station T1) to an intermediate relay station (wireless stations R1, R2,..., Rp) and a destination end station (wireless station T2). The transmission quality information is recursively calculated for the transmission route, and the transmission route with the best transmission quality is selected again (step S2).

  For execution of the route reselection procedure, a control frame for preprocessing (hereinafter referred to as “preprocessing control frame”) is used. The wireless station 10 of the predetermined route relays the preprocessing control frame from the start station to the end station along the predetermined route. When relaying the preprocessing control frame, the transmission quality calculation unit 161 of the wireless station 10 of the default route recursively calculates transmission quality information for possible transmission routes other than the default route using the radio link information. The route reselection unit 162 reselects the transmission route with the best transmission quality based on the transmission quality information calculated by the transmission quality calculation unit 161. The control frame transmission unit 163 sets the transmission quality information of the transmission route reselected by the route reselection unit 162 in the preprocessing control frame so that the transmission quality can be calculated in the other radio station 10 on the end station side. The wireless communication unit 12 is instructed to transmit.

The wireless link information here refers to various information that can be used for communication between a certain wireless station pair. For example, as radio link information, radio channel information (CSI: Channel State Information), received signal to noise power ratio (SNR) information, modulation coding scheme (MCS) information, Information related to various wireless links such as traffic (TSI: Traffic State Information) information can be considered. The wireless propagation path information and the received signal-to-noise power ratio information can be obtained as indirect information from the reception state of the training signal or the like in the wireless communication unit 12. Further, the modulation system coding system can be obtained directly from information set in the preprocessing control frame or the like by the transmission source radio station 10. The traffic information can be obtained by monitoring the transmission source of the wireless signal received by the wireless communication unit 12.
The transmission quality information here means an index for evaluating transmission quality such as transmission capacity, transmission error rate, transmission delay, etc. in a certain transmission route.

  In the present embodiment, the scope of application of the technology is not limited by the types of radio link information and transmission quality information used. Therefore, in application to a real system, it is not necessary to limit to the radio link information and transmission quality information listed above.

  Next, the wireless station 10 of the default route performs multihop transmission and success / failure according to the transmission route (hereinafter referred to as “reselection route”) re-selected by the route reselection unit 162 in the process in step S2 and the transmission method. A response is executed (step S3). That is, the transmission control unit 17 of the start station instructs the radio communication unit 12 to transmit the transmission frame as a radio frame for multihop transmission, and the antenna 11 transmits the transmission frame by radio. The transmission control unit 17 of the relay station receives a transmission frame transmitted from another radio station 10 (starting station or other relay station) on the start station side along the reselection route, and relays the received transmission frame. The wireless communication unit 12 is instructed to transmit to the other wireless station 10 on the end station side. By repeating this, the destination radio station 10 receives the transmission frame by multi-hop transmission. Further, the transmission control unit 17 of the end station instructs the wireless communication unit 12 to transmit the success / failure response as a radio frame, and the antenna 11 transmits the success / failure response wirelessly. The success / failure response frame is relayed to the start station using a transmission route that has been traced back to the predetermined route, a transmission route that has been traced back to the reselection route, or a transmission route that has been selected by another method. Since the success / failure response has a smaller amount of data than the transmission frame, a transmission route corresponding to the amount of data can be used. For example, a transmission route that has followed the reselection route in reverse can be notified by transmitting a control frame from the end station to the start station in the reverse order of the default route after the end of route reselection.

  Finally, the communication right acquisition unit 15 of the start station releases the communication right to the wireless communication network after completing the multi-hop transmission and the success / failure response (step S4).

Next, details of the process of step S2 for reselecting a transmission route by pre-processing along a predetermined route for multi-hop transmission determined by routing will be described.
In step S2, the wireless station 10 of the default route operates as follows.
(1) The wireless station 10 of the default route relays the preprocessing control frame along the default route of multihop transmission determined by the routing technique.
(2) Each relay station of the predetermined route selects a transmission route with the highest quality in the local station, stores the transmission quality information C of the selected transmission route in a control frame, and relays it.

  The transmission quality information C is expressed as the following equation (1). Note that “max” indicates that the largest element is selected from the elements listed in {}. The direct transmission quality is the transmission quality of the direct transmission from the start station, the relay transmission quality is the transmission quality of the relay transmission via other relay stations on the start station side, and the cooperative relay transmission quality is the start station and This is the transmission quality of cooperative relay transmission using two or more of the other relay stations on the start station side.

  C = max {direct transmission quality, relay transmission quality, cooperative relay transmission quality} (1)

  Here, a method of route reselection by preprocessing for multi-hop transmission with five relay stations and six hops between the start station and the end station will be described. Note that the method of applying the preprocessing described here is also obvious for multihop transmission with an arbitrary number of relay stations and hops, and does not exceed the scope of the description of this embodiment.

  FIG. 4 is a diagram illustrating a configuration example of multihop transmission, and illustrates an example in which there are five relay stations. Here, all the radio stations 10 participating in the multi-hop transmission are arranged in order from the start station to the end station along the predetermined route of the multi-hop transmission determined by the routing technique. Hereinafter, the radio station 10 that is the start station is referred to as the start station 1, the radio station 10 that is the relay station in the predetermined route is referred to as relay station 2 to relay station 6, and the radio station 10 that is the end station is referred to as the end station 7.

  In order to select an optimal transmission route, information on all desired links and listening links from the start station 1 to the end station 7 is aggregated in the end station 7, and transmission quality information is calculated based on the information. This is a general technique. The desired link here is a wireless link on the predetermined route, and the listening link is a wireless link not on the predetermined route. For example, the radio link Lk12 indicated by a solid line in FIG. 4 is a desired link between the start station 1 and the relay station 2, and the radio link Lk13 indicated by a dotted line is between the start station 1 and the relay station 3. It is a hearing link. The transmission quality information Ci (i = 2 to 6) is the transmission quality information C calculated by the relay station i according to the equation (1).

  As the number of hops in multi-hop transmission increases, the number of listening links increases rapidly, so that transmitting all the information of the listening links to the end station 7 of multi-hop transmission causes a considerable overhead. In order to avoid this, transmission quality information in the latent route is calculated together with the relay of the preprocessing control frame by the recursive method described below.

  The start station 1, the relay stations 2 to 6, and the end station 7 transmit preprocessing control frames used for performing route reselection from the start station 1 to the end station 7 along a predetermined route determined by the routing technique. Relay. In the example shown in FIG. 4, the pre-processing control frames are relayed on the transmission route of the start station 1, relay station 2, relay station 3, relay station 4, relay station 5, relay station 6, and end station 7, for a total of six frames. 6 time steps corresponding to hops are used. Hereinafter, the j-th time step is described as time step #j (j = 1 to 6).

  In time step # 1, that is, in hops 1 and 2, the start station 1 wirelessly transmits a preprocessing control frame. The relay station 2 having a desired link with the start station 1 in the predetermined route, the relay stations 3 to 6 that are hearing stations, and the end station 7 (hereinafter referred to as “listening stations 3 to 7”) are the previous ones. A processing control frame is received. That is, the control frame transmission unit 163 of the start station 1 instructs the wireless communication unit 12 to transmit the preprocessing control frame, and the wireless communication unit 12 generates a preprocessing control frame including a training signal and transmits it from the antenna 11. Transmit by radio. The relay station 2 and the listening stations 3 to 7 receive the preprocessing control frame by the antenna 11, and the wireless communication unit 12 performs the reception processing of the preprocessing control frame. The transmission quality calculation unit 161 of the relay station 2 and the listening stations 3 to 7 uses the training signal included in the pre-processing control frame received and processed by the wireless communication unit 12 to perform wireless communication between the start station 1 and its own station. Estimate link information. Radio link information between the start station 1 and the own station estimated by the relay station 2 is set as desired radio link information L-12, and between the start station 1 and the own station estimated by the listening stations 3, 4, 5, 6, and 7. Are radio channel link information L-13, L-14, L-15, L-16, and L-17, respectively. However, there may be radio link information that cannot be estimated due to a distance from the start station 1 or an obstacle.

  The transmission quality calculation unit 161 of the relay station 2 uses the obtained desired radio link information L-12, as shown in the following formula (2), transmission quality information by direct transmission with the start station 1 in its own station Is calculated as transmission quality information C2.

  C2 = f (L-12) (2)

  Note that f () is a function that calculates transmission quality information of direct transmission using radio link information as a parameter. The control frame transmission unit 163 of the relay station 2 adds the transmission quality information C2 to the preprocessing control frame received from the start station 1, and prepares to notify the next relay station 3.

  Similarly, the transmission quality calculation unit 161 of the listening station i that has been able to estimate the listening wireless link information L-1i (i = 3, 4, 5, 6, 7) also uses the listening wireless link information L-1i, The transmission quality information by direct transmission with the start station 1 in the own station is calculated. Thereby, the transmission quality calculation units 161 of the listening stations 3, 4, 5, 6, and 7 respectively transmit the transmission quality information f (L-13), f (L-14), and f ( L-15), f (L-16), and f (L-17) are obtained.

  At time step # 2, that is, at hops 2 and 3, relay station 2 relays the preprocessing control frame. That is, the control frame transmission unit 163 of the relay station 2 instructs the wireless communication unit 12 to transmit the preprocessing control frame to which the transmission quality information C2 is added. The wireless communication unit 12 performs a preprocessing control frame transmission process, and transmits the preprocess control frame wirelessly from the antenna 11.

  A relay station 3 having a desired link with the relay station 2 in a predetermined route, and relay stations 4, 5, 6 and an end station 7 (hereinafter referred to as “listening stations 4 to 7”) which are hearing stations. The preprocessing control frame transmitted from the relay station 2 is received by the antenna 11, and the wireless communication unit 12 performs a preprocessing control frame reception process. The transmission quality calculation unit 161 of the relay station 3 and the listening stations 4 to 7 uses the training signal included in the preprocessing control frame received and processed by the wireless communication unit 12, and wirelessly communicates between the relay station 2 and the own station. Estimate link information. The radio link information between the relay station 2 and the own station estimated by the relay station 3 is set as desired radio link information L-23, and the radio between the relay station 2 and the own station estimated by the listening stations 4, 5, 6, and 7 is used. The link information is referred to as hearing radio link information L-24, L-25, L-26, and L-27, respectively.

  The transmission quality calculation unit 161 of the relay station 3 uses the obtained desired radio link information L-23 and the transmission quality information C2 set in the preprocessing control frame received from the relay station 2 to As shown in (3), the transmission quality information by the relay transmission relaying the relay station 2 in the own station is calculated.

  Transmission quality information by relay transmission relaying the relay station 2 in the relay station 3 = g (C2, L-23) (3)

  Note that g () is a function for calculating transmission quality information for relay transmission using radio link information and transmission quality information as parameters. With this function g (), both transmission quality information up to the current last hop (here, transmission quality information C2) and radio link information (here, desired radio link information L-23) with the current last hop. Thus, transmission quality information of relay transmission can be uniquely determined.

  Further, the transmission quality calculation unit 161 of the relay station 3 calculates transmission quality information by cooperative relay transmission using the start station 1 and the relay station 2 as follows using the following equation (4). For the calculation, transmission quality information f (L-13) by direct transmission with the start station 1 calculated at the previous hop, and transmission quality information by relay transmission relaying the relay station 2 calculated by equation (3). g (C2, L-23) is used.

  Transmission quality information by cooperative relay transmission using the start station 1 and the relay station 2 in the relay station 3 = h (f (L-13), g (C2, L-23)) (4)

  Note that h () is a function for calculating transmission quality information of cooperative relay transmission. By this function h (), cooperative relay is performed by a combination of transmission quality by direct transmission (here, f (L-13)) and transmission quality by relay transmission (here, g (C2, L-23)). Transmission quality information of transmission can be uniquely determined.

  Finally, the route reselection unit 162 of the relay station 3 selects a transmission method having the best transmission quality from the three types of direct transmission from the start station 1, relay transmission, and cooperative relay transmission, and selects the selected transmission. The transmission route corresponding to the method and the transmission method are stored. The transmission quality information C3 of the relay station 3 determined by route reselection can be expressed as the following equation (5).

  C3 = max {f (L-13), g (C2, L-23), h (f (L-13), g (C2, L-23))} (5)

  The control frame transmission unit 163 of the relay station 3 adds the calculated transmission quality information C3 to the received preprocessing control frame, and prepares to notify the next relay station 4.

  Similarly, the listening station i that has been able to estimate the listening radio link information L-2i (i = 4, 5, 6, 7) also calculates transmission quality information in its own station. That is, the transmission quality calculation unit 161 of the hearing station i calculates f (L-2i), g (C2, L-2i), and h (f (L-1i), g (C2, L-2i)). .

  From time step # 3, hop 3 · 4 to time step # 6, to hop 6 · 7, each relay station 4-6 and end station 7 relays the preprocessing control frame, and directly transmits and relays in the same manner as above. Transmission quality information by transmission and cooperative relay transmission is calculated, and if a preprocessing control frame is received from a relay station one hop ahead (one starting station side having the desired link with the local station) in a predetermined route, the calculated transmission The best transmission method is selected based on the quality information, and the transmission route is reset based on the selected transmission method. In the case of a relay station, the selected transmission route and its transmission method are stored, and transmission quality information corresponding to the selected transmission method is added to the preprocessing control frame and transmitted to the end station side relay station or end station. .

  For example, at time step # 3, at hops 3 and 4, the relay stations 4, 5, 6 and the end station 7 each receive the preprocessing control frame transmitted by the relay station 3, and transmit quality information f (L-34). , F (L-35), f (L-36), and f (L-37) are calculated. Subsequently, each of the relay stations 4, 5, 6 and the end station 7 uses the transmission quality information C3 set in the preprocessing control frame by the relay station 3, and uses the transmission quality information g (C3, L-34) of the relay transmission. , G (C3, L-35), g (C3, L-36), and g (C3, L-37) are calculated. Further, each of relay stations 4, 5, 6 and end station 7 calculates possible transmission quality information of cooperative relay transmission. The possible cooperative relay transmission uses start station 1 and relay station 2, start station 1 and relay station 3, relay station 2 and relay station 3, start station 1, relay station 2 and relay station 3. The relay station 4 can take transmission quality information f (L-14) of direct transmission from the start station 1, transmission quality information g (C2, L-24), g (C3, L-34) of relay transmission, and possible The best transmission quality information is selected from the transmission quality information of cooperative relay transmission. The relay station 4 stores the transmission route corresponding to the selected transmission quality information and its transmission method, and transmits a preprocessing control frame in which the selected transmission quality information is added as C4 in the next time step # 4.

  Also, for example, at time step # 4 and at hops 4 and 5, the relay stations 5 and 6 and the end station 7 each receive the preprocessing control frame transmitted by the relay station 4 and transmit quality information f (L-45). , F (L-46), f (L-47) are calculated. Subsequently, the relay stations 5 and 6 and the end station 7 respectively use the transmission quality information C4 set in the preprocessing control frame by the relay station 4 to transmit transmission quality information g (C4, L-45), g of relay transmission. (C4, L-46) and g (C4, L-47) are calculated. Further, each of the relay stations 5 and 6 and the end station 7 calculates possible transmission quality information of cooperative relay transmission. The relay station 5 transmits transmission quality information f (L-15) for direct transmission from the start station 1 and transmission quality information g (C2, L-25), g (C3, L-35), g (C4) for relay transmission. L-45) and possible transmission quality information of cooperative relay transmission. The relay station 5 stores the transmission route and the transmission method corresponding to the selected transmission quality information, and transmits a preprocessing control frame in which the selected transmission quality information is added as C5 in the next time step # 5.

  Similar processing is performed in time step # 5, hops 5 and 6, time step # 6, and hops 6 and 7. In the above, the example using the radio link information estimated from the training signal is shown. However, other radio link information may be used instead, or other radio link information may be used together. .

  As described above, in each relay station and end station, desired radio link information and listening radio link information obtained based on the preprocessing control frame, etc., and the current hop stored in the preprocessing control frame It is possible to calculate transmission quality information by direct transmission, relay transmission, and cooperative relay transmission using the transmission quality information up to. Accordingly, transmission of a large amount of desired radio link information and listening radio link information can be avoided, and as a result, the overhead of route reselection can be greatly reduced.

  However, the amount of information / computation necessary for the above-described route reselection procedure increases in proportion to the number of multi-hops. This is because the pattern of cooperative relay transmission increases significantly as the relay station has a later hop count. Therefore, in order to reduce the amount of information and computation required for the route reselection procedure, a slide window is introduced to control the window width and slide width. By this control, the multihop transmission range is subdivided, and the transmission route is reselected in each subdivided range. As a result, even if the number of hops in multi-hop transmission increases, the route reselection range can be controlled by subdivision. Therefore, the increase in the necessary information amount and calculation amount is not proportional to the increase in the hop number. In this way, by introducing the sliding window and controlling the window width and the sliding width, it is possible to trade off the characteristics of the above embodiment and the amount of calculation necessary for calculating the transmission quality information C.

  FIG. 5 is a diagram showing a case where a sliding window is introduced in the example of FIG. Here, two patterns of a window width Nw = 3 hops and a slide width Ns = 1 hop, and a window width Nw = 3 hops and a slide width Ns = 3 hops are shown. As in the case of the slide width Ns = 1 hop, the control ranges may be overlapped by setting the slide width.

  The slide of the window starts from the start station 1 of the predetermined route and continues to slide until the end station 7 is reached. In this way, in order to realize routing in consideration of cooperative relay transmission with window control in all routes, the window is slid from the start station to the end station. In each slide, the preprocessing control frame transmitted by the radio station 10 at the beginning of the window is received by the radio station 10 at the end of the window (within the window width), and recursively as described above. The transmission quality information of direct transmission, relay transmission, and cooperative relay transmission is calculated. As a result, cooperative relay transmission patterns are limited to those using start stations or relay stations within the window width range, so the number of cooperative relay transmission patterns is significantly reduced compared to when sliding windows are not introduced. To do. Accordingly, the amount of information and the amount of calculation necessary for calculating the transmission quality information are controlled by the window width Nw and the slide width Ns.

When the window width Nw = 3 hops and the slide width Ns = 1 hop, the start station 1 which is the beginning of the window first transmits a preprocessing control frame. This preprocessing control frame is received by the relay stations 2, 3, and 4 within the window width Nw (= 3 hops), and the transmission quality information of the direct transmission is calculated.
Since the transmission of the preprocessing control frame for the slide width Ns (= 1 hop) is completed within the window, the window moves by the slide width Ns, and the start end of the window becomes the relay station 2. Therefore, when the relay station 2 transmits the preprocessing control frame in which the transmission quality information C2 is set, the relay stations 3, 4, and 5 within the window width Nw (= 3 hops) from the start end receive and directly communicate with the relay station 2. The transmission quality information of the transmission and the relay transmission relayed through the relay station 2 is calculated, and the relay stations 3 and 4 receiving two or more preprocessing control frames further calculate the transmission quality information of the cooperative relay transmission. The relay station 3 resets the default route by the transmission method selected based on the calculated transmission quality information.
Since the transmission of the preprocessing control frame for the slide width Ns (= 1 hop) is completed within the window, the window moves by the slide width Ns, and the start end of the window becomes the relay station 3. Therefore, when the relay station 3 transmits the preprocessing control frame in which the transmission quality information C3 is set, the relay stations 4, 5, and 6 within the window width Nw (= 3 hops) from the start end receive and directly communicate with the relay station 3. The transmission quality information of the transmission and the relay transmission relayed through the relay station 3 is calculated, and the relay stations 4 and 5 receiving two or more preprocessing control frames further calculate the transmission quality information of the cooperative relay transmission. The relay station 4 resets the default route by the transmission method selected based on the calculated transmission quality information.
Repeat the above and slide the windows in order.

On the other hand, when the window width Nw = 3 hops and the slide width Ns = 3 hops, the start station 1 which is the beginning of the window first transmits a preprocessing control frame. This preprocessing control frame is received by the relay stations 2, 3, and 4 within the window width Nw (= 3 hops), and the transmission quality information of the direct transmission is calculated.
Since the transmission of the preprocessing control frame for the slide width Ns (= 3 hops) in the window has not been completed yet, the window does not slide. Therefore, when the relay station 2 transmits the pre-processing control frame in which the transmission quality information C2 is set, the relay stations 3 and 4 within the window width Nw (= 3 hops) from the start end receive the direct transmission, relay transmission, and cooperation. Calculate transmission quality information for relay transmission. The relay station 3 resets the default route by the transmission method selected based on the calculated transmission quality information.
Since the transmission of the preprocessing control frame for the slide width Ns (= 3 hops) in the window has not been completed yet, the window does not slide. Therefore, when the relay station 3 transmits the preprocessing control frame in which the transmission quality information C3 is set, only the relay station 4 within the window width Nw (= 3 hops) from the beginning receives the direct transmission, relay transmission, and cooperative relay. Calculate transmission quality information of the transmission. The relay station 4 resets the default route by the transmission method selected based on the calculated transmission quality information.
As a result, the transmission of the preprocessing control frame for the slide width Ns (= 3 hops) within the window is completed, so the window moves by the slide width Ns, and the start end of the window becomes the relay station 4, and the same processing as described above is performed. repeat.

  According to the embodiment described above, the multihop transmission route determined by the conventional routing technique is used as the basis of the route researching, and the multihop route researching in consideration of the effect of cooperative relay transmission is realized. As a result, in the wireless communication network to which the present embodiment is finally applied, improved communication quality such as higher system throughput and shorter transmission delay can be realized as compared with the conventional wireless communication network.

In existing routing technology, transmission routes are selected on the assumption of hop-by-hop multi-hop transmission. Therefore, even when applied to cooperative relay transmission, transmission routes are not optimized in consideration of cooperative relay transmission. It was. Therefore, as described above, in the present embodiment, a control frame including a training signal necessary for route reselection is transmitted along a predetermined route constructed by an existing routing technique, and is directly transmitted at each relay station. The transmission quality of the relay transmission and the cooperative relay transmission is calculated recursively. Then, the best transmission method is selected based on the calculated transmission quality, the default route is reset, and a control frame including the transmission quality information is transmitted to the next hop destination. Accordingly, it is possible to perform multi-hop transmission by selecting an optimal transmission method from among transmission methods including cooperative relay transmission.
Further, by further performing the sliding window control, it is possible to limit the range of route reselection and reduce the amount of calculation in route reselection.

  The functions of all or part of the wireless communication unit 12 and the communication control unit 13 of the wireless station 10 in the above-described embodiment are ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), FPGA (Field Programmable Gate Array), and the like. The hardware (electronic circuit) may be used, or may be realized by a computer. When all or part of the functions of the wireless communication unit 12 and the communication control unit 13 of the wireless station 10 are realized by a computer, a program for realizing the function is recorded on a computer-readable recording medium, and this recording is performed. You may implement | achieve by making a computer system read the program recorded on the medium and executing it. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program that holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  The present invention can be applied to a wireless communication network in which a relay station exists between a transmitting station and a receiving station.

DESCRIPTION OF SYMBOLS 10 Radio station 11 Antenna 12 Wireless communication part 13 Communication control part 14 Route selection part 15 Communication right acquisition part 16 Preprocessing part 161 Transmission quality calculation part 162 Route reselection part 163 Control frame transmission part 17 Transmission control part

Claims (5)

A transmission route determination method executed by a wireless communication system having a plurality of wireless stations,
The wireless station that is a relay station that relays a transmission frame between a start station and an end station in a transmission route of multihop transmission including the wireless station and the wireless station that is the end station,
A first control frame is received from another radio station on the transmission station side in the transmission route, a transmission quality of direct transmission is calculated based on the received first control frame, and the first control frame A transmission quality calculation step of calculating the transmission quality of relay transmission and the transmission quality of cooperative relay transmission based on the transmission quality in the other radio station set to
The transmission quality of the direct transmission calculated in the transmission quality calculation step when the first control frame is received from another radio station on the start station side having a radio link with the own station in the transmission route, A route reselection step of selecting a transmission method based on the transmission quality of relay transmission and the transmission quality of the cooperative relay transmission, and resetting the transmission route based on the selected transmission method;
A first control frame transmission step in which the wireless station as the relay station sets the transmission quality in the first control frame when the transmission method selected in the route reselection step is used, and transmits the first control frame; ,
A second control frame is sent to the start station side in the reverse order of the transmission route before the resetting, by the wireless station being the end station following the transmission route reconfigured in the route reselection step. A second control frame transmission step for notifying by transmitting
A transmission route determination method characterized by comprising: In the transmission route of multi-hop transmission, slide the window by the slide width in order from the start station to the end station side,
The radio station that is the relay station in the window and the radio station that is the end station receive the first control frame from another radio station on the start station side in the window. Perform the quality calculation step,
The transmission route determination method according to claim 1, wherein: The wireless station in the transmission route reconfigured in the route reselection step performs multi-hop transmission between the start station and the end station according to the transmission route reconfigured by the selected transmission method. Further comprising performing a multi-hop transmission step,
The transmission route determination method according to claim 1, wherein the transmission route is determined. The wireless station that is the starting station is
A communication right acquisition step of acquiring a communication right according to the medium access control method;
A pre-processing start step of transmitting a control frame when a communication right is acquired in the communication right acquisition step;
A communication right releasing step of releasing the communication right when the multi-hop transmission step is completed;
The transmission route determination method according to claim 3, wherein: A wireless communication system having a plurality of wireless stations,
The radio station that is a relay station that relays a transmission frame between a start station and an end station in a transmission route of multihop transmission composed of the radio station and the radio station that is the end station are:
A first control frame is received from another radio station on the transmission station side in the transmission route, a transmission quality of direct transmission is calculated based on the received first control frame, and the first control frame A transmission quality calculation unit for calculating the transmission quality of relay transmission and the transmission quality of cooperative relay transmission based on the transmission quality in the other radio station set to
The transmission quality of the direct transmission calculated by the transmission quality calculation unit when the first control frame is received from another radio station on the start station side having a radio link with the own station in the transmission route, Selecting a transmission method based on the transmission quality of relay transmission and the transmission quality of the cooperative relay transmission, and a route reselecting unit for resetting the transmission route based on the selected transmission method,
The wireless station which is the relay station is
Further comprising a first control frame transmitting unit for transmitting the transmission quality in the case of using the transmission method in which the route reselection unit selects sets the first control frame,
The wireless station which is the end station is
A transmission route obtained by reversing the transmission route reconfigured by the route reselection unit is notified by transmitting a second control frame to the start station in reverse order of the transmission route before reconfiguration. A control frame transmission unit;
A wireless communication system.

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