Wireless relay device

Abstract

This wireless relay device comprises a wireless communication terminal unit and a base station unit. The wireless communication terminal unit comprises a plurality of wireless communication units for connecting and communicating with mutually different upstream communication devices, and a control unit for: acquiring, for each of the wireless communication units, communication quality information that is transmitted from the corresponding upstream communication device and that indicates the communication quality of an upstream link, which is a wireless link formed in an upstream wireless relay path further upstream of the upstream communication device; selecting, on the basis of the communication quality of the plurality of upstream links and the communication quality of a plurality of proximate links that are wireless links respectively formed between the plurality of wireless communication units and the upstream communication devices, one of the proximate links to be used for signal transfer; and outputting, to the base station unit, communication quality information generated on the basis of the communication quality of the selected proximate link and the communication quality of the upstream link corresponding to the selected proximate link. The base station unit comprises a base station communication unit for connecting and communicating with a downstream communication device and transmitting, to the downstream communication device, the communication quality information outputted from the control unit.

Description

Wireless relay device

[0001] This invention relates to a wireless relay device.

[0002] In wireless communication systems such as Wi-Fi (Local Area Network), which do not assume that a terminal will move across the communication areas of multiple wireless communication base stations (hereinafter simply referred to as "base stations"), a wireless communication terminal moving between base stations generally loses its communication connection with a base station when it leaves the communication area, then searches for another base station to connect to and re-establishes the communication connection. Therefore, in this case, a state of communication interruption may occur where the wireless communication terminal is not connected to any base station.

[0003] In contrast, there is a conventional technology that involves mounting multiple wireless communication devices (hereinafter referred to as "radio devices") on a single wireless communication terminal and controlling these multiple radio devices to communicate with different base stations (see, for example, Non-Patent Documents 1 and 2). This makes it possible for a single wireless communication terminal to form multiple radio links simultaneously, and even if the radio link with one base station is disconnected, communication can be continued through the radio link with the other base station, thus preventing communication interruptions. Furthermore, this conventional technology can improve communication quality by selecting the radio link with better communication quality from among the multiple radio links formed to send and receive signals.

[0004] This conventional technology, which prevents communication interruptions and improves communication quality by equipping a communication device with multiple radios and forming multiple wireless links, can be used not only in wireless communication terminals that connect to base stations, but also in transmission technology for wireless relays that involve multiple hops. For example, one could consider mounting both the above-mentioned base station and wireless communication terminal in a wireless relay station that relays signal transmission. The base station and wireless communication terminal mounted in the wireless relay station would be connected, for example, via a back-to-back connection (direct connection).

[0005] With this configuration, each of the multiple wireless relay stations can form wireless links with multiple communication devices such as other wireless relay stations and base stations, and select the wireless link with the best communication quality from among them. As a result, even in wireless propagation environments where the communication quality of a wireless link fluctuates due to obstacles that block radio waves (e.g., vehicles or people), the wireless relay station can successively select and switch to the wireless link with the best communication quality. In this way, by utilizing the above conventional technology in wireless relay stations, redundant links in wireless relay can be easily formed.

[0006] "World's First Realization of Uninterrupted, High-Capacity Wireless Transmission in High-Speed ​​Mobility Environments Using 60GHz Band Wireless LAN - Making Non-Mobile Wireless Communication, Similar to Millimeter-Wave Band Wireless LAN, Applicable to Mobile Devices such as Vehicles," Nippon Telegraph and Telephone Corporation, News Release, February 25, 2022, [Retrieved March 14, 2025], Internet (URL: https: / / group.ntt / jp / newsrelease / 2022 / 02 / 25 / 220225a.html) T. Iwakuni et al., "Handover Experiment of 60-GHz-Band Wireless LAN in over 200-km / h High-Speed ​​Mobility Environment," IEICE Trans. Communication, Vol.E106-B, No.4, pp.384-391, October 2022.

[0007] The conventional technology described above is fundamentally a technology for selecting a wireless link between a base station and a wireless communication terminal. Therefore, it basically selects the wireless link based on the communication quality of the wireless link between communication devices that are directly connected to each other wirelessly (hereinafter referred to as the "nearest link"). However, in the case of wireless relays that hop multiple times, in the wireless relay path, for example, there may be another communication device connected to a preceding communication device (wireless relay station) that is already connected to a certain wireless relay station. In this case, there is also a wireless link (hereinafter referred to as the "upstream link") between the preceding wireless relay station and the communication further upstream. Therefore, in the case of wireless relays that hop multiple times, when a wireless relay station selects the nearest link with a preceding communication device, it is necessary to consider not only the communication quality of the nearest link but also the communication quality of the upstream link.

[0008] However, simply applying the above-mentioned conventional technology to wireless relays that hop multiple times would result in selecting the nearest link based solely on the communication quality of the nearest link. In some cases, this might lead to selecting the nearest link in a wireless relay path that, for example, passes through an upstream link with poor communication quality. Furthermore, simply applying the above-mentioned conventional technology to wireless relays that hop multiple times might also lead to selecting the nearest link in a wireless relay path where, for example, the upstream link is disconnected and it is impossible to send or receive signals with the final communication partner.

[0009] Thus, conventional technology had the problem of sometimes selecting an inappropriate wireless link in wireless relays that involved multiple hops.

[0010] In light of the above circumstances, the aim is to provide a technology that can select an appropriate wireless link even in wireless relays that involve multiple hops.

[0011] One aspect of the present invention is a wireless relay device comprising a wireless communication terminal unit and a base station unit, wherein the wireless communication terminal unit comprises a plurality of wireless communication units that communicate with different higher-level communication devices, each of the wireless communication units acquires communication quality information indicating the communication quality of a higher-level link, which is a wireless link formed in a wireless relay path higher than the higher-level communication device, transmitted from each of the higher-level communication devices, and selects one of the nearest links to be used for signal transmission based on the communication quality of the plurality of nearest links, which are wireless links formed between the plurality of wireless communication units and the higher-level communication device, and the communication quality of the plurality of higher-level links, and outputs the communication quality information generated based on the communication quality of the selected nearest link and the communication quality of the higher-level link corresponding to the selected nearest link to the base station unit, and the base station unit is a wireless relay device comprising a base station communication unit that communicates with a lower-level communication device and transmits the communication quality information output from the control unit to the lower-level communication device.

[0012] According to the present invention, it becomes possible to select an appropriate wireless link even in the case of wireless relays that hop multiple times.

[0013] This is a schematic diagram showing the overall configuration of the wireless relay system 1 in one embodiment of the present invention. This is a schematic diagram showing the configuration of wireless relay station #1_1 in one embodiment of the present invention. This is a diagram for explaining the operation of the base station, the first-layer wireless relay station, and the second-layer wireless relay station in one embodiment of the present invention. This is a diagram for explaining the operation of the third-layer and above wireless relay stations in one embodiment of the present invention. This is a diagram for explaining the operation of the terminal wireless communication terminal in one embodiment of the present invention. This is a diagram for explaining the operation of the terminal wireless communication terminal in one embodiment of the present invention. This is a diagram for explaining the operation of the wireless relay station when the upper link is disconnected in one embodiment of the present invention.

[0014] Hereinafter, one embodiment of the wireless relay device of the present invention will be described in detail with reference to the drawings.

[0015] [Wireless Relay System Configuration] Figure 1 is a schematic diagram showing the overall configuration of wireless relay system 1 in one embodiment of the present invention. In Figure 1, "NW" is an abbreviation for "Network" and represents a communication network. "AP" is an abbreviation for "Access Point" and represents a base station (wireless communication base station). "STA" is an abbreviation for "Station" and represents a wireless communication terminal.

[0016] As shown in Figure 1, the wireless relay system 1 is connected to the network 10 and N ０ Individual base stations (AP#0_1, AP#0_2, ..., AP#0_N ０ ) and N １ Individual first-tier wireless relay stations (wireless relay station #1_1, wireless relay station #1_2, ..., wireless relay station #1_N) １ ) and N ２ Individual second-tier wireless relay stations (wireless relay station #2_1, wireless relay station #2_2, ..., wireless relay station #2_N) ２ ) and N ３ Individual end wireless communication terminals (STA#3_1, ..., STA#3_N ３ It consists of including the following:

[0017] Furthermore, the configuration of the wireless relay station is shown in Figure 2. Note that the wireless relay station is an example of the wireless relay device of the present invention. Figure 2 is a schematic configuration diagram showing the general configuration of wireless relay station #1_1 in one embodiment of the present invention. As shown in Figure 2, wireless relay station #1_1 is composed of a base station (AP #1_1) and a wireless communication terminal (STA #1_1). AP #1_1 and STA #1_1 are connected in a back-to-back connection (direct connection).

[0018] The Back-to-Back connection method may be a wired connection using an Ethernet cable or optical cable, or a wireless connection using a wireless LAN (Local Area Network), etc.

[0019] Further, as shown in FIG. 2, STA#1_1 is configured to include two wireless devices (wireless device #A, wireless device #B) and a control device. To simplify the description, in the present embodiment, all STAs are assumed to include only two wireless devices, but the number of wireless devices included in an STA may be three or more.

[0020] The wireless device #A and the wireless device #B each communicate and connect to any one of APs in the immediately upper layer (that is, in the case of the wireless device #A and the wireless device #B of STA#1_1, AP#0_1, AP#0_2, ..., AP#0_N ０ any one of them). Further, the wireless device #A and the wireless device #B communicate and connect to different APs from each other.

[0021] The control device controls switching of the APs to which the wireless device #A and the wireless device #B connect, based on the communication quality of the wireless links. Further, the control device performs control to select and use an immediate link with better communication quality based on the communication quality of the wireless links (the immediate link and an upper layer link).

[0022] Further, the control device transmits information indicating the communication quality of the wireless link (communication quality that takes into consideration not only the communication quality of the immediate link but also the communication quality of the upper layer link) to any one of the STAs in the immediately lower layer (that is, in the case of AP#1_1, STA#2_1, STA#2_2, ..., STA#2_N ２ any one of them). Details of the information indicating the communication quality notified to the STAs in the immediately lower layer (hereinafter referred to as "communication quality information") will be described later.

[0023] Although FIG. 2 shows the configuration of wireless relay station #1_1, the configuration of other wireless relay stations shown in FIG. 1 is the same as this.

[0024] As shown in FIG. 1, AP#0_1 to AP#0_N ０ are communicatively connected to a network 10. Further, the wireless relay stations #1_1 to #1_N in the first layer １ provided with STA#1_1 to STA#1_N １ are connected to AP#0_1 to AP#0_N ０each communicates with any one of them. In addition, each of STAs #2_1 to STA #2_N provided in wireless relay stations #2_1 to #2_N in the second layer ２ each communicates with any one of APs #1_1 to #1_N provided in wireless relay stations #1_1 to #1_N in the first layer ２ In addition, STAs #3_1 to #3_N, which are terminal wireless communication terminals, １ each communicate with any one of APs #2_1 to #2_N provided in wireless relay stations #2_1 to #2_N in the second layer １ respectively. ３ For simplicity of explanation, Fig. 1 shows a case where there are only two layers of hierarchies configured by wireless relay stations, namely the first layer and the second layer (that is, only two hops). However, the hierarchy configured by wireless relay stations may have three or more layers (that is, three or more hops). ２ STAs #3_1 to #3_N, which are terminal wireless communication terminals, ２ are not limited to a configuration in which they communicate with an AP provided in a bottom-layer wireless relay station (that is, wireless relay stations #2_1 to #2_N in the second layer). STAs #3_1 to #3_N may be configured to communicate with an AP provided in a wireless relay station of another layer (for example, wireless relay stations #1_1 to #2_N in the first layer), or an AP in communication connection with a network 10 (that is, APs #0_1 to #0_N).

[0025] Hereinafter, an example in which the hierarchy configured by wireless relay stations has three or more layers (that is, three or more hops) will be used to separately describe the operation of an AP connected in communication to a network 10, the operation of a wireless relay station in the first layer, the operation of a wireless relay station in the second layer, the operation of a wireless relay station in the third and higher layers, and the operation of a terminal wireless communication terminal.

[0026] ３ ２ ３ １ ０

[0027] ​​​​​​​

[0028] [Operation of APs communicatively connected to network 10] Figure 3 is a diagram for explaining the operations of a base station, a first-tier wireless relay station, and a second-tier wireless relay station according to an embodiment of the present invention.

[0029] The operations of AP#0_1 and AP#0_2, which are communicatively connected to the network 10, are the same as those of conventional general wireless communication base stations. AP#0_1 and AP#0_2 communicatively connect to, for example, radio #A or radio #B of STA#1_1 provided in wireless relay station#1_1 of the first tier. AP#0_1 and AP#0_2 also communicatively connect to, for example, radio #A or radio #B of STA#1_2 provided in wireless relay station#1_2 of the first tier.

[0030] [Operation of wireless relay stations constituting the first tier] Wireless relay station#1_1 to wireless relay station#1_N of the first tier １ STA#1_1 to STA#1_N provided therein １ select an immediate link to be used for signal transmission based on the communication quality of a plurality of immediate links. That is, STA#1_1 to STA#1_N １ use a plurality of wireless devices (e.g., radio #A and radio #B) to connect to different base stations (e.g., AP#0_1 and AP#0_2), respectively, to form respective immediate links. Then, STA#1_1 to STA#1_N １ select an immediate link (wireless device) with better communication quality to perform signal transmission.

[0031] Hereinafter, the operation of wireless relay station#1_1 will be described as an example with reference to FIG. 3. For example, it is assumed that two wireless devices are mounted on STA#1_1, one of the two wireless devices is communicatively connected to AP#0_1, and the other is communicatively connected to AP#0_2, so that respective immediate links are formed. In this case, the communication quality of each immediate link is expressed as follows, for example.

[0032] ・Communication quality of the immediate link between AP#0_1 and STA#1_1: Q0_1⇒1_1 ・Communication quality of the immediate link between AP#0_2 and STA#1_1: Q0_2⇒1_1

[0033] Furthermore, according to the communication quality notation described above, if the other STAs and APs are represented as "STA#i_j" and "AP#(i-1)_k (where i≧2)" respectively, the communication quality of the nearest link can be conveniently represented as follows.

[0034] - Communication quality of the nearest link between AP#(i-1)_k and STA#i_j: Q(i-1)_k ⇒ i_j

[0035] The STA#1_1 control unit compares the communication quality values ​​of each nearest link. For example, if the communication quality of Q0_1⇒1_1 is better than that of Q0_2⇒1_1, it selects the nearest link formed by the communication connection with AP#0_1.

[0036] Furthermore, when the control device of STA#1_1 selects the nearest link formed by a communication connection with AP#0_1, it immediately outputs the communication quality value (Q0_1⇒1_1) of that nearest link to AP#1_1 located in the same wireless relay station #1_1 via a Back-to-Back connection.

[0037] For example, the following values ​​can be used as the communication quality values ​​mentioned above. However, any communication quality value may be used as long as it objectively indicates the communication quality of the nearest link or upstream link.

[0038] - The value of the received signal strength (received signal level) of the radio waves from the AP to each STA radio. - The value of the transmission distance between each STA radio and the AP. - The value of the transmission speed between each STA radio and the AP. - The value of the throughput between each STA radio and the AP. - The value of the number of relay links (hops) between the NW and each STA radio (for example, in the case of Q0_1 ⇒ 1_1, the number of relay links is 1).

[0039] Selecting the nearest link with better communication quality means, for example, selecting it as follows:

[0040] - If the communication quality value is the received level (received signal strength), transmission speed, or throughput value, select the nearest link with the higher value. - If the communication quality value is the transmission distance or the number of relay links value, select the nearest link with the lower value.

[0041] Furthermore, a configuration may be implemented that considers multiple types of communication quality values ​​and selects the nearest link with the best communication quality.

[0042] For example, AP#0_1 to AP#0_N are used to obtain the transmission distance value. ０ The respective installation locations, and wireless relay station #1_1 to wireless relay station #1_N １ If the installation locations of each are fixed, a method can be devised to calculate the transmission distance by knowing those installation locations in advance. Also, even if the installation locations change, AP#0_1 to AP#0_N ０ Each of these, and wireless relay station #1_1 to wireless relay station #1_N １ One possible method for calculating the transmission distance is to pre-install equipment capable of determining the location of the device, such as a GPS (Global Positioning System) receiver, on each of these devices.

[0043] Furthermore, when using high-frequency broadband signals in wireless transmission, such broadband signals have high resolution, allowing for highly accurate distance measurement. Therefore, a method of calculating transmission distance using high-frequency broadband signals is also conceivable.

[0044] Next, AP#1_1 obtains the communication quality value (Q0_1⇒1_1) of the nearest link output from STA#1_1. AP#1_1 notifies the STA (radio relay station or terminal radio communication device) one level below its own device, of the obtained value as the communication quality value of the higher-level link of radio relay station#1_1. In other words, AP#1_1 transmits communication quality information indicating the communication quality value of the higher-level link (i.e., the Q0_1⇒1_1 value) to the STA connected to its own device.

[0045] Furthermore, the method for notifying the communication quality value of the upper-level link may be by broadcasting signals such as beacon signals, or by including it in the response signal sent back when a connection request is received from an STA at a lower level. In other words, any method can be used to notify the communication quality value of the upper-level link, as long as it allows the STA searching for the destination AP to recognize the communication quality of the upper-level link.

[0046] In the above explanation, we focused on the operation of wireless relay station #1_1 as an example, but the operation is the same for the other wireless relay stations that make up the first layer (wireless relay station #1_2, wireless relay station #1_3, ...).

[0047] [Operation of the Radio Relay Station Constituting the Second Layer] The operation of radio relay station #2_1 will be explained below using Figure 3 as an example. For example, STA #2_1 is equipped with two radios, and one of these two radios (radio #A) is in communication with AP #1_1 on the layer above, and the other radio (radio #B) is in communication with AP #1_2 on the layer above, forming the nearest links.

[0048] The control unit of wireless relay station #2_1 selects the wireless link with the best communication quality. At this time, the control unit of wireless relay station #2_1 identifies the wireless link with the best communication quality in the following manner.

[0049] First, radio #A of STA#2_1, which is connected to AP#1_1, receives communication control information notified from AP#1_1. The control device of radio relay station #2_1 recognizes the value of the communication quality of the upper link (Q0_1⇒1_1) based on the received communication control information.

[0050] Furthermore, the control unit of wireless relay station #2_1 measures the communication quality (Q1_1⇒2_1) of the nearest link between AP#1_1 and STA#2_1's radio #A. Then, based on the communication quality (Q1_1⇒2_1) of the nearest link and the communication quality (Q0_1⇒1_1) of the higher-level link, the control unit of wireless relay station #2_1 calculates an overall communication quality value that takes both into account.

[0051] For example, the following methods can be considered for calculating the overall communication quality value.

[0052] - If the communication quality value is the received level (received signal strength) value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the transmission distance value, the average value of both or the maximum value of both shall be used as the overall communication quality value. - If the communication quality value is the transmission speed value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the throughput value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the number of relay links value, the number of relay links up to the nearest link shall be used as the overall communication quality value.

[0053] Furthermore, any calculation method can be used to calculate the overall communication quality value, as long as it takes into account both the communication quality of the nearest link and the communication quality of the upstream link.

[0054] Similarly, radio #B of STA2_1, which is connected to AP#1_2, receives communication control information notified by AP#1_2. The control device of radio relay station #2_1 recognizes the value of the communication quality of the upper link (Q0_1⇒1_2) based on the received communication control information.

[0055] Furthermore, the control unit of wireless relay station #2_1 measures the communication quality (Q1_2⇒2_1) of the nearest link between AP #1_2 and STA #2_1's radio equipment #B. Then, based on the communication quality (Q1_2⇒2_1) of the nearest link and the communication quality (Q0_1⇒1_2) of the higher-level link, the control unit of wireless relay station #2_1 calculates the overall communication quality, which is the communication quality that takes both into account.

[0056] Then, the control device of radio relay station #2_1 compares the overall communication quality value when using radio #A of STA #2_1 with the overall communication quality value when using radio #B of STA #2_1, and selects the nearest link (radio) that provides better overall communication quality.

[0057] Furthermore, selecting the nearest link that provides better overall communication quality means, for example, the following:

[0058] - If the overall communication quality value is the value of the received level (received signal strength), the value of the transmission speed, or the throughput, select the nearest link with the larger value. - If the overall communication quality value is the value of the transmission distance or the value of the number of relay links (hops), select the nearest link with the smaller value.

[0059] Alternatively, the configuration may be designed to select the nearest link that provides the best overall communication quality by considering multiple types of overall communication quality values.

[0060] Furthermore, the control unit of STA#2_1 immediately outputs an overall communication quality value, which takes into account the communication quality value of the selected nearest link and the communication quality value of the higher-level link, to AP#2_1 located in the same radio relay station #2_1 via a Back-to-Back connection. Alternatively, instead of outputting the overall communication quality value, the control unit of STA#2_1 may output the communication quality value of the selected nearest link and the communication quality values ​​of each higher-level link individually.

[0061] Next, AP#2_1 obtains the overall communication quality value output from STA#2_1. AP#2_1 notifies the STA (radio relay station or terminal radio communication device) one level down of the network hierarchy of radio relay station #2_1 of the communication quality value of the upper link. In other words, AP#2_1 transmits communication quality information indicating the overall communication quality value to the STA one level down of the network hierarchy.

[0062] Alternatively, AP#2_1 may transmit communication quality information showing the communication quality value of the nearest link and the communication quality values ​​of each upstream link, instead of transmitting communication quality information showing the overall communication quality value.

[0063] Furthermore, the method for notifying the communication quality value of the upper-level link may be by broadcasting signals such as beacon signals, or by including it in the response signal sent back when a connection request is received from an STA at a lower level. In other words, any method can be used to notify the communication quality value of the upper-level link, as long as it allows the STA searching for the destination AP to recognize the communication quality of the upper-level link.

[0064] In the above explanation, we focused on the operation of wireless relay station #2_1 as an example, but the operation is the same for the other wireless relay stations that make up the second layer (wireless relay station #2_2, wireless relay station #2_3, ...).

[0065] [Operation of a wireless relay station constituting the third layer or higher] Figure 4 is a diagram illustrating the operation of a wireless relay station of the third layer or higher in one embodiment of the present invention.

[0066] The operation of radio relay station #K_1, which is a radio relay station of the K-th tier (where K≧3), will be explained below with reference to Figure 4. The operation of STA#K_1 to K_2 installed in radio relay station #K_1, as described below, is almost the same as the operation of STA#2_1 to 2_2 installed in the aforementioned second-tier radio relay station #2_1.

[0067] For example, suppose STA#K_1 is equipped with two radios (radio #A and radio #B), and one of these radios (radio #A) is in communication with AP#(K-1)_1, and the other radio (radio #B) is in communication with AP#(K-1)_2, forming the nearest links.

[0068] The control unit of wireless relay station #K_1 selects the wireless link with the best communication quality. At this time, the control unit of wireless relay station #2_1 identifies the wireless link with the best communication quality in the following manner.

[0069] First, radio #A of STA#K_1, which is connected to AP#(K-1)_1, receives communication control information notified from AP#(K-1)_1. For the sake of simplicity, we assume that there are two APs in the (K-1) layer, but what if there are N APs in the (K-1) layer? Ｋ－１ If there are individual values, then AP#(k-1)_j (where 1 ≤ j ≤ N) ｋ－１ ) can be expressed as

[0070] The control unit of wireless relay station #K_1 recognizes the communication quality value of the higher-level link based on the received communication control information. The control unit of wireless relay station #K_1 also measures the communication quality value (Q(K-1)_1⇒K_1) of the nearest link between AP#(K-1)_1 and radio equipment #A of STA#K_1. Then, the control unit of wireless relay station #K_1 calculates the overall communication quality, which is the communication quality that takes both the nearest link communication quality (Q(K-1)_1⇒K_1) value and the higher-level link communication quality value into consideration.

[0071] Similarly, radio #B of STA2_1, which is connected to AP#1_2, receives communication control information notified by AP#1_2. The control device of radio relay station #2_1 recognizes the value of the communication quality of the upper link (Q0_1⇒1_2) based on the received communication control information.

[0072] As a method for calculating the overall communication quality value, similar to the calculation method described above for the operation of the wireless relay stations constituting the second layer, the following methods can be considered.

[0073] - If the communication quality value is the received level (received signal strength) value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the transmission distance value, the average value of both or the maximum value of both shall be used as the overall communication quality value. - If the communication quality value is the transmission speed value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the throughput value, the average value of both or the minimum value of both shall be used as the overall communication quality value. - If the communication quality value is the number of relay links (hops), the value of the number of relay links up to the nearest link shall be used as the overall communication quality value.

[0074] Furthermore, if the information included in the communication quality information is the overall communication quality value of the upstream link, the method for calculating the "average value of both" in the above calculation method may be a simple binary average of the communication quality value of the nearest link and the overall communication quality value of the upstream link, or it may be a method in which the overall communication quality of the upstream link is weighted by the number of relay links and then the average of both is calculated. In the latter case, it will be the average value for each relay link. This also applies when calculating the maximum and minimum values, not just the average value.

[0075] Furthermore, if the information included in the communication quality information is the communication quality value of each upstream relay link, then, for example, the average of the communication quality values ​​of all wireless links, including the nearest link and each upstream relay link, can be calculated. Note that this applies not only to the average value but also when calculating the maximum and minimum values.

[0076] Furthermore, any calculation method can be used to calculate the overall communication quality value, as long as it takes into account both the communication quality value of the nearest link and the communication quality value of the upstream link.

[0077] Similarly, radio #B of STA2_1, which is connected to AP#1_2, receives communication control information notified by AP#1_2. The control device of radio relay station #2_1 recognizes the value of the communication quality of the upper link (Q0_1⇒1_2) based on the received communication control information.

[0078] Furthermore, the control unit of radio relay station #K_1 measures the communication quality (Q(K-1)_2⇒K_1) of the nearest link between AP#(K-1)_2 and radio equipment #B of STA#K_1. Then, the control unit of radio relay station #K_1 calculates the overall communication quality, which is the communication quality that takes both the nearest link communication quality (Q(K-1)_2⇒K_1) and the overall communication quality of the higher-level link into consideration.

[0079] Then, the control device of radio relay station #K_1 compares the overall communication quality value when using radio #A of STA#K_1 with the overall communication quality value when using radio #B of STA#K_1, and selects the nearest link (radio) that provides better overall communication quality.

[0080] Furthermore, selecting the nearest link that provides better overall communication quality means, as explained in the operation of the wireless relay stations that constitute the second layer above, for example, the following:

[0081] - If the overall communication quality value is the value of the received level (received signal strength), the value of the transmission speed, or the throughput, select the nearest link with the larger value. - If the overall communication quality value is the value of the transmission distance or the value of the number of relay links (hops), select the nearest link with the smaller value.

[0082] Alternatively, the configuration may be designed to select the nearest link that provides the best overall communication quality by considering multiple types of overall communication quality values.

[0083] Furthermore, the control unit of STA#K_1 immediately outputs an overall communication quality value, which takes into account the communication quality value of the selected nearest link and the communication quality value of the higher-level link, to AP#K_1 located in the same radio relay station#K_1 via a Back-to-Back connection. Alternatively, instead of outputting the overall communication quality value, the control unit of STA#K_1 may output the communication quality value of the selected nearest link and the communication quality values ​​of each higher-level link individually.

[0084] Next, AP#K_1 acquires the overall communication quality value output from STA#K_1. AP#K_1 notifies the STA (radio relay station or terminal radio communication device) one level down of the hierarchy of radio relay station#K_1 of the communication quality value of the upper link. In other words, AP#K_1 transmits communication quality information indicating the overall communication quality value to the STA one level down of the hierarchy.

[0085] Alternatively, AP#K_1 may transmit communication quality information indicating the communication quality value of the nearest link and the communication quality values ​​of each upstream link, instead of transmitting communication quality information indicating the overall communication quality value.

[0086] Furthermore, the method for notifying the communication quality value of the upper-level link may be by broadcasting signals such as beacon signals, or by including it in the response signal sent back when a connection request is received from an STA at a lower level. In other words, any method can be used to notify the communication quality value of the upper-level link, as long as it allows the STA searching for the destination AP to recognize the communication quality of the upper-level link.

[0087] In the above explanation, we focused on the operation of wireless relay station #K_1 as an example, but the operation is the same for other wireless relay stations that make up the Kth layer (i.e., layers 3 and above) (wireless relay station #K_2, wireless relay station #K_3, ...).

[0088] [Operation of the End Wireless Communication Terminal] Figures 5 and 6 are diagrams illustrating the operation of the end wireless communication terminal in one embodiment of the present invention.

[0089] Two possible operations for the end wireless communication terminal are described below. Figure 5 illustrates the first example of operation, and Figure 6 illustrates the second example of operation.

[0090] The first example of operation is as follows: As shown in Figure 5, the end wireless communication terminal is equipped with multiple radios (for example, radio #A and radio #B). The multiple radios each communicate with different APs and form wireless links (nearest links). The control device of the end wireless communication terminal selects the nearest link (radio) with the best communication quality from among the multiple nearest links formed and transmits the signal.

[0091] Thus, in the first example of operation, the control device of the end wireless communication terminal selects the nearest link (radio) to be used for signal transmission based solely on the communication quality of the nearest link (without considering the communication quality of the higher-level link), similar to conventional technology.

[0092] The second example of operation is as follows. As shown in Figure 6, the terminal wireless communication device is equipped with multiple radios (for example, radio #A and radio #B). The multiple radios each communicate with different APs and form wireless links (nearest links). The control device of the terminal wireless communication device selects the nearest link from among the multiple nearest links that has the best overall communication quality, calculated by considering the communication quality value of the nearest link and the communication quality value of the higher-level link, and transmits the signal.

[0093] Thus, in this second example of operation, the control device of the end wireless communication terminal selects the nearest link (radio) to be used for signal transmission based on the overall communication quality calculated by considering the communication quality of the nearest link and the communication quality of the higher-level link, similar to the operation of the wireless relay station described above.

[0094] Unlike the aforementioned wireless relay stations, the end-user wireless communication terminals do not have access points (APs) for back-to-back connections. Therefore, the end-user wireless communication terminals do not need to output communication quality information to the APs, such as the calculated overall communication quality value, the communication quality value of the nearest link, and the communication quality values ​​of each higher-level link.

[0095] [Operation when the upstream link is disconnected] The following describes an example of the operation of a wireless relay station when the upstream link is disconnected. Figure 7 is a diagram illustrating the operation of a wireless relay station when the upstream link is disconnected in one embodiment of the present invention.

[0096] In a wireless relay station #i_j (where i≧1, 1≦j≦Ni), if all of the multiple radios installed in STA#i_j of the wireless relay station #i_j are not connected to the AP of the higher layer (disconnected), STA#i_j outputs information to that effect to AP#i_j installed in the same wireless relay station #i_j via a back-to-back connection.

[0097] For example, in Figure 7, of the two radios installed in STA#K_2 of radio relay station #K_2, one radio (radio #A) has its radio link (nearest link) with AP#(K_1)_1 disconnected, and the other radio (radio #B) has its nearest link with AP#(K_1)_2 disconnected. In other words, all radios in STA#K_2 of radio relay station #K_2 are disconnected from higher-level APs. In this case, STA#K_2 outputs information to AP#K_2 of the same radio relay station #K_2 indicating that all radio links (nearest links) with APs are disconnected.

[0098] Specifically, a disconnected wireless link can occur when all wireless devices are unable to connect to a higher-level AP (Access Point) due to equipment failure, or when a communication connection with a higher-level AP is lost due to changes in the wireless propagation environment, etc.

[0099] When AP#i_j receives information from STA#i_j indicating that all radios are disconnected from the higher-level AP, it takes action to prevent lower-level STAs (for example, STAs of lower-level radio relay stations and terminal radio communication devices) from connecting to its own device (AP#i_j).

[0100] For example, in Figure 7, if AP#K_2 receives information from STA#K_2 indicating that all (two) radios are disconnected from the higher-level APs AP#(K-1)_1 and AP#(K-1)_2, it will take action to prevent lower-level STAs such as STA#(K+1)_1 from connecting to its own device (AP#K_2). For example, the following actions can be considered as actions to prevent lower-level STAs from connecting to its own device (AP).

[0101] (When no lower-level STAs are connected to the AP) - An action that prevents the transmission of broadcast signals such as beacon signals, which are necessary for lower-level STAs to connect to the AP, to lower-level STAs. - An action that prevents the AP from sending a response signal when a lower-level STA requests a connection to the AP. - An action that sends a response signal indicating that the connection is rejected when a lower-level STA requests a connection to the AP.

[0102] (Operation when a lower-level STA is already connected to the AP) - Sends a control signal to the connected STA to indicate that the connection will be terminated. - Stops sending notification signals (or synchronization signals) such as beacon signals necessary to maintain the communication connection to the lower-level STA.

[0103] Thus, when a lower-level STA is already connected to the AP, any action is acceptable as long as it prompts the connected STA to instantly switch its communication connection to another AP.

[0104] As described above, the wireless relay station in one embodiment of the present invention comprises a wireless communication terminal (STA) equipped with multiple radios that communicate with each higher-level communication device, and a base station (AP) that communicates with lower-level communication devices. The wireless relay station has a configuration that, in wireless relaying that involves multiple hops, selects the nearest link by considering not only the communication quality of the nearest link formed with the next higher-level communication device, but also the communication quality of the higher-level link. Furthermore, the wireless relay station has a configuration that notifies the lower-level communication device of information indicating the overall communication quality, which takes into account the communication quality of the nearest link and the communication quality of the higher-level link.

[0105] By having such a configuration, the wireless relay station in one embodiment of the present invention can prevent, for example, selecting the nearest link of a wireless relay path that goes through a higher-level link with inferior communication quality in a wireless relay that involves multiple hops.

[0106] Furthermore, the wireless relay station in one embodiment of the present invention is further configured to control itself so as not to establish a communication connection with a lower-level communication device when all nearest links are disconnected. By having such a configuration, the wireless relay station in one embodiment of the present invention can prevent the lower-level communication device from selecting the nearest link of a wireless relay path where the upper-level links are disconnected.

[0107] As described above, the wireless relay station in one embodiment of the present invention can select an appropriate wireless link even in the case of wireless relays that hop multiple times.

[0108] According to the embodiments described above, the wireless relay device comprises a wireless communication terminal unit and a base station unit. For example, the wireless relay device is a wireless relay station in the embodiment, the wireless communication terminal unit is an STA in the embodiment, and the base station unit is an AP in the embodiment. The wireless communication terminal unit comprises a plurality of wireless communication units and a control unit. For example, the wireless communication unit is a wireless device in the embodiment, and the control unit is a control device in the embodiment.

[0109] Multiple wireless communication units each communicate with different higher-level communication devices. The control unit acquires communication quality information for each wireless communication unit, which indicates the communication quality of the higher-level link, a wireless link formed in a wireless relay path higher than the higher-level communication device, transmitted from each higher-level communication device. The control unit selects one nearest link to be used for signal transmission based on the communication quality of multiple nearest links, which are wireless links formed between the multiple wireless communication units and the higher-level communication device, and the communication quality of multiple higher-level links. The control unit outputs communication quality information generated based on the communication quality of the selected nearest link and the communication quality of the higher-level link corresponding to the selected nearest link to the base station unit. For example, the communication quality information generated based on the communication quality of the selected nearest link and the communication quality of the higher-level link corresponding to the selected nearest link is communication quality information that includes the overall communication quality value in the embodiment. The base station unit includes a base station communication unit. The base station communication unit communicates with lower-level communication devices and transmits the communication quality information output from the control unit to the lower-level communication devices.

[0110] Furthermore, in the above-mentioned wireless relay device, the value of communication quality may be a value based on at least one of the following: radio wave received signal strength, transmission distance, transmission speed, throughput, and number of relay links.

[0111] In addition, in the above-mentioned wireless relay device, the base station communication unit may include communication quality information in a broadcast signal transmitted to multiple lower-level communication devices, or in a response signal to connection request signals transmitted from each of the multiple lower-level communication devices.

[0112] Furthermore, in the above-mentioned wireless relay device, the control unit may be configured to prevent the base station communication unit from establishing a communication connection with a lower-level communication device if all nearest links are disconnected.

[0113] Some or all of the configurations of the wireless relay station, wireless communication terminal, and base station in the above-described embodiment may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. Here, "computer system" includes hardware such as the OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Moreover, "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such a case. Furthermore, the above-mentioned program may be for implementing some of the functions described above, or it may be a program that can implement the above-mentioned functions in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0114] Although embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0115] 1 Wireless relay system 10 Network AP Base station STA Wireless communication terminal

Claims

1. A wireless relay device comprising a wireless communication terminal unit and a base station unit, wherein the wireless communication terminal unit comprises a plurality of wireless communication units that communicate with different higher-level communication devices, each of the wireless communication units acquires communication quality information for each wireless communication unit indicating the communication quality of a higher-level link which is a wireless link formed in a wireless relay path higher than the higher-level communication device, transmitted from each of the higher-level communication devices, selects one of the nearest links to be used for signal transmission based on the communication quality of a plurality of nearest links which are wireless links formed between the plurality of wireless communication units and the higher-level communication device and the communication quality of the plurality of higher-level links, and outputs the communication quality information generated based on the communication quality of the selected nearest link and the communication quality of the higher-level link corresponding to the selected nearest link to the base station unit, and the base station unit comprises a base station communication unit that communicates with a lower-level communication device and transmits the communication quality information output from the control unit to the lower-level communication device.

2. The wireless relay device according to claim 1, wherein the value of the communication quality is a value based on at least one of the received signal strength of radio waves, transmission distance, transmission speed, throughput, and number of relay links.

3. The wireless relay device according to claim 1, wherein the base station communication unit transmits the communication quality information in a broadcast signal to a plurality of lower-level communication devices, or in a response signal to connection request signals transmitted from each of the plurality of lower-level communication devices.

4. The wireless relay device according to claim 1, wherein the control unit controls the base station communication unit not to establish a communication connection with the lower-level communication device when all of the nearest links are disconnected.

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