JP6074795B2 - Multi-hop wireless communication system - Google Patents

Description

  The present invention relates to a multi-hop wireless communication system that performs wireless communication based on an OFDMA scheme in a white space band.

  Orthogonal frequency division multiple access (Orthogonal Frequency Division Multiple Access) is used for IEEE802.16 WiMAX, IEEE802.22 WRAN, etc., which are commercial systems. This OFDMA is an access method based on the OFDM method. In the OFDM method, data is mapped to a large number of subcarriers arranged so as to be orthogonal to each other, and a time series signal is derived by performing inverse Fourier transform on the data group, and a transmission symbol for radio transmission is created. On the receiving side, a transmitted data group is derived by Fourier transforming such symbols, and the transmission data is reproduced by restoring individual data associated with each subcarrier. Such OFDMA can support a more flexible service level by sharing a subchannel among a plurality of users.

  In addition to such OFDMA, a channel segment access method has been proposed in which a communication channel is divided into several subchannels to improve network capacity.

  However, the above-described channel segment access scheme in OFDMA is a single hop wireless communication network, that is, a method in which direct communication is performed between a base station and a wireless terminal, and before communication is started in the network. It is necessary to set a channel segment in advance. For this reason, a multi-hop wireless network (Multi-hop Wireless Networks) is a network that consists of only wireless nodes and that can communicate without going through an infrastructure such as a wired network by relaying packets autonomously. ) Cannot be applied to this.

IEEE Std. 802.22-2011 "IEEE 802.22-2011 (TM) Standard for Cognitive Wireless Regional Area Networks (RAN) for Operation in TV Bands"

  There has been proposed a radio network system capable of improving network capacity and reducing signal interference by applying a channel segment access scheme to OFDMA.

  However, in the above communication control method, it is performed by direct communication between a single-hop wireless communication network, that is, a base station and a wireless terminal, and cannot be applied to the communication control method in a so-called multi-hop wireless communication network. . In addition, it is necessary to set a channel segment in advance before the network is operated, and there is a problem that it is difficult to freely set a channel segment according to the network situation.

  In particular, in multi-hop wireless communication, an opportunity to relay wireless communication by another communication terminal increases, so that the possibility of a communication collision increases or it is necessary to effectively suppress this.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to position the communication terminal in applying the OFDMA and the channel segment access method in the multi-hop wireless communication network. By using information, it is possible to set a flexible and accurate channel according to network conditions, and to provide a multi-hop wireless communication system suitable for increasing network capacity (capacity). .

  In order to solve the above-described problem, the present inventor, in a multi-hop wireless communication system that performs wireless communication based on the OFDMA scheme in the white space band, one or more communication devices and management devices that perform wireless communication based on the OFDMA scheme; And a base station that manages a plurality of sub-networks, each of the base stations acquires position information received from a GPS satellite by a management device in each sub-network, and sub-indexes determined from the acquired position information Based on the positional relationship between the networks, a method for allocating frames in successive frames constituting each OFDMA superframe between sub-networks is determined.

  The multi-hop wireless communication system according to claim 1 is a multi-hop wireless communication system that performs wireless communication based on an OFDMA scheme in a white space band, and performs wireless communication based on the OFDMA scheme with one or more communication devices. A sub-network having a management device, a base station that manages a plurality of the sub-networks, and position information transmitting means for transmitting position information to the management device in the sub-network, Each management device in each subnetwork acquires the position information received from the position information transmission means, and each superframe of OFDMA between the subnetworks based on the positional relationship between the subnetworks determined from the acquired position information. Consists of Assign any frame and any frequency subchannel in the frame group, assign different frames in the continuous frame group constituting each superframe of OFDMA between the sub-networks, or OFDMA between the sub-networks It is characterized in that it is determined whether to assign different frequency subchannels to the same frame in a continuous frame group constituting each superframe.

  A multi-hop wireless communication system according to a second aspect of the present invention is the multi-hop wireless communication system according to the first aspect, wherein the base station newly communicates when an available frame is present in a continuous frame group constituting a super frame. The empty frame is assigned to the subnetwork to be started.

  The multi-hop wireless communication system according to claim 3 is the multi-hop wireless communication system according to claim 2, wherein the base station has another sub-network in a predetermined distance range of each sub-network based on a positional relationship between the sub-networks. If not, it is characterized in that an arbitrary frequency subchannel is allocated in an arbitrary frame in a continuous frame group constituting each OFDMA superframe between the sub-networks.

  A multi-hop wireless communication system according to a fourth aspect of the present invention is the multi-hop wireless communication system according to the third aspect, wherein the base station has the sub-network when there is another sub-network within a predetermined distance from the sub-network where communication is newly started. Assign different frames in consecutive frames constituting each OFDMA superframe between networks, or use the same frame and different frequencies in successive frames constituting each OFDMA superframe between the sub-networks. It is characterized by assigning subchannels.

  The multi-hop wireless communication system according to claim 5 is the multi-hop wireless communication system according to claim 4, wherein the base station is configured to receive the sub-network when another sub-network exists within a predetermined distance from the sub-network where communication is newly started. It is characterized in that different frames in consecutive frames constituting each OFDMA superframe are assigned between networks, and further different frequency subchannels are assigned.

  The multi-hop wireless communication system according to claim 6 is the multi-hop wireless communication system according to any one of claims 1 to 5, wherein the base station performs different frames between the sub-networks and mutually When different frequency subchannels cannot be allocated, control is performed such that the communication output is lowered for the communication device and the management device in each subnetwork.

  In a multi-hop wireless communication system in which OFDMA frames can be assigned to sub-networks based on the above-described method, the location information of the management device, and thus the sub-network, is effectively used, and flexible and accurate according to the status of the sub-network. Channel settings can be made. As a result, it is possible to improve the storage density of the subnetwork per unit area and further reduce signal interference. As a result, a multi-hop wireless communication system can be configured on a large scale. For this reason, when urgent communication is required in the event of a disaster, it is more prominent when it is required to improve the capacity per unit area of the subnetwork or when it is difficult to predict the status of the subnetwork. It is possible to achieve an advantageous effect.

It is a system block block diagram of the multihop radio | wireless communications system to which this invention is applied. It is a figure which shows the super-frame format required when performing OFDMA communication between a management device and a communication device. It is a figure which shows the detail of an OFDMA frame. It is a flowchart which shows the allocation of the frame in the multihop radio | wireless communications system to which this invention is applied. It is a figure for demonstrating three distance classification | category centering on one management device. It is a conceptual diagram which allocates arbitrary frames. It is a figure for demonstrating the operation | movement of step S15. It is a figure for demonstrating the operation | movement of step S16. It is a figure for demonstrating the operation | movement of step S17. It is a figure for demonstrating the Example of the multihop radio | wireless communications system to which this invention is applied. It is another figure for demonstrating the Example of the multihop radio | wireless communications system to which this invention is applied.

  Hereinafter, embodiments of a multi-hop wireless communication system to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 shows a system block configuration diagram of a multi-hop wireless communication system 1 to which the present invention is applied. This multi-hop wireless communication system 1 is used for IEEE802.16 WiMAX, IEEE802.22 WRAN, and the like. The multi-hop wireless communication system 1 is premised on using a so-called white space band.

  As shown in FIG. 1, the multi-hop wireless communication system 1 includes a base station 20 and a plurality of sub-networks 3 formed around the base station 20. Incidentally, the base station 20 and the plurality of sub-networks 3 form a network 2. Each subnetwork 3 includes communication devices 40 a and 40 b and a management device 30 that performs wireless communication based on the OFDMA (Orthogonal Frequency Division Multiple Access) method with the communication devices 40. The base station 20 is connected to the public communication network 6, and a database 5 is connected to the public communication network 6. Further, the multi-hop wireless communication system 1 includes a GPS (Global Positioning System) satellite 8.

  The base station 20 is a device for managing wireless communication by the plurality of sub-networks 3. The base station 20 also serves as a wireless access point that relays communication with a plurality of sub-networks 3 and also serves as an interface with the public communication network 6. The base station 20 includes a location information management unit 21 and a frame allocation unit 22. The location information management unit 21 receives location information from each of the sub-networks 3 and, consequently, the management device 30 that constitutes the sub-network 3, and manages the location information. The frame allocation unit 22 allocates a frame necessary for wireless communication performed in each subnetwork 3 based on the location information managed by the location information management unit 21. The base station 20 transmits position information regarding its own position and position information managed by the position information management unit 21 to the database 5 via the public communication network 6. Further, the base station 20 receives channel information relating to a channel necessary for communication from the database 5 via the public communication network 6.

  The public communication network 6 includes ISDN (Integrated Services Digital Network) / B (broadband) -ISDN connected to the TA / modem as well as the Internet network connecting the database 5 and the base station 20 via a telephone line. Thus, it is a network or the like that enables bidirectional transmission and reception of information. The public communication network 6 may be any communication network that can be accessed from a mobile terminal, a smartphone, or a personal computer (PC).

  The database 5 receives position information from the base station 20 via the public communication network 6 and stores it. Further, the database 5 transmits to the base station 20 communication channel information and the like in other base stations 20 and other communication systems as necessary.

  The management device 30 in the sub-network 3 is a device for controlling wireless communication in the sub-network 3 and is realized by any device such as a portable information terminal, a smartphone, and a PC. The management device 30 is assumed to be configured by a so-called H-CPE (High-capability Consumer Premise Entity), and can acquire position information from the GPS satellite 8. The management device 30 includes a GPS position information unit 31 and a frame allocation unit 32. The GPS position information unit 31 stores and manages its own position information received from the GPS satellite 8. The frame allocation unit 32 performs a process for allocating a frame necessary for communication by each communication device 40.

  The management device 30 is assigned by the base station 20 an OFDMA frame necessary for performing OFDMA communication with the communication device 40. The management device 30 performs OFDMA communication with the communication device 40 using the allocated OFDMA frame.

  The communication devices 40a and 40b are embodied by any device including a mobile information terminal, a smartphone, and a PC, for example. The communication devices 40a and 40b may be configured by an L-CPE (Low-capability Consumer Premise Entity) incapable of acquiring position information from the GPS satellite 8, but are not limited thereto. 8 may be configured by an H-CPE capable of acquiring position information from 8. The communication terminal devices a and 40b use the OFDMA frame assigned by the management device 30 when actually performing wireless communication using OFDMA.

  The GPS satellite 8 is an artificial satellite that transmits position information to the management device 30 in each subnetwork 3. Based on the position information sent from the GPS satellite 8, the management device 30 can acquire the position information at the current position.

  In the multi-hop wireless communication system 1 having the above-described configuration, for example, a superframe format as shown in FIG. 2 is used when performing OFDMA communication between the management device 30 and the communication device 40.

  In this superframe format, superframes n-1, n, n + 1,... Separated by beacons are consecutive. The period of this super frame is, for example, 160 ms. Each super frame is further divided into 16 frames # 0 to # 15 having a length of, for example, 10 ms. Incidentally, a super frame preamble, a frame preamble, an SCH (Superframe Control Header), and the like are attached to the head of the frame 0, and so-called management information and the like are described. The actual data described in these frames # 0 to # 15 constitutes a so-called OFDMA frame.

  FIG. 3 shows the details of the OFDMA frame. In this OFDMA frame, it is possible to assign to each subnetwork 3 a subchannel composed of a combination of a frequency axis logical channel obtained by dividing subcarriers and a time slot. At the same time, symbols generated along the time axis can be assigned to each subnetwork 3. In other words, this OFDMA frame can be assigned to each subnetwork 3 on the two axes of the time (t) axis and the frequency (f) axis.

  The ODFMA frame describes a frame preamble for describing management information, a frame control header (FCH), USMAP in which uplink burst signal allocation information is described, and downlink burst signal allocation information. DSMAP or the like is provided at the head portion in the time (t) direction. Also, in this OFDMA, a DS subframe composed of downlink bursts # 11, # 12,..., #M as downlink data areas to be assigned to the subnetwork 3, a ranging subchannel, and an uplink burst #, respectively. , #N, and a US subframe consisting of #n. A TTG (transmission / reception switching gap) is provided between the DS subframe and the US subframe. An RTG (reception / transmission switching gap) is provided at the end of the US subframe.

  The multi-hop wireless communication system 1 to which the present invention is applied allocates the OFDMA frame as described above to each sub-network 3 based on the method described below. As shown in the flowchart shown in FIG. 4, first, the location information is transferred from each management device 30 in the subnetwork 3 to the base station 20. Each management device 30 is in a state in which position information is transmitted from the GPS satellite 8. For this reason, the management device 30 can transfer the position information received from the GPS satellite 8 to the base station 20 as necessary or constantly.

  Next, the process proceeds to step S <b> 12, and the base station 20 identifies the position information received from the management device 30. Based on the position information received from the management device 30, the base station 20 can also identify the position of the sub-network 3 deployed around the management device 30.

  Next, in step S13, the base station 20 assigns a non-assigned frame in the superframe. In other words, in this step S13, if there is a frame that is not allocated in the superframe, no matter how far the subnetwork 3 is separated or how close the subnetwork 3 is, the priority is assigned to it. It is.

  In addition, the order of each process of this step S12 and step S13 may be changed and performed.

  Next, the process proceeds to step S14, and the base station 20 pays attention to one management device 30a in the subnetwork 3 to which a frame is to be drunk from among the management devices 30 identified based on the position information identified in step S12. . As shown in FIG. 5, it can be classified into three distances centered on one management device 30a. First, the distance A indicates the communication range within the sub-network 3 constituting the management device 30a. Further, the distance B is expressed by, for example, A × 2, and if the communication device 40 exists on the boundary line of the communication range of the distance A, the maximum arrival of radio waves from the communication device 40 Indicates distance. The distance C is expressed by, for example, A × 3. When the communication device 40 ′ in another subnetwork 3 is located on the distance C line, the radio wave from the communication device 40 ′ is a distance. The distance when reaching B is shown. That is, when the management device 40 ′ of the other subnetwork 3 exists in a range shorter than the distance C, the other subnetwork 3 may cause communication interference with the subnetwork centered on the one management device 30a. is there.

  For this reason, the base station checks whether or not another subnetwork 3 exists within a distance C from the one management device 30a in the subnetwork 3 to which a frame is to be allocated. Specifically, it is confirmed whether or not there is a subnetwork 3 to which a frame in the superframe is assigned in the distance C. As a result, if there is a subnetwork 3 to which a frame in the superframe is allocated within the distance C, the process proceeds to step S15, and if not, the process proceeds to step S18.

  When the process proceeds to step S18, an arbitrary frame in a continuous frame group constituting each superframe of OFDMA is allocated to one management device 30a in the subnetwork 3 to which a frame is to be allocated. FIG. 6 is a conceptual diagram for assigning such an arbitrary frame. Assume that frame # 3 is assigned to one management device 30a in the subnetwork 3 to which a frame is to be assigned. Assume that this frame # 3 has already been used as the frame f1 by the sub-network 3 located farther than the distance C. Even in such a case, communication interference does not occur because the other sub-networks 3 are separated from each other by the distance C. Therefore, even if an arbitrary frame is assigned to the subnetwork 3 to which a frame is to be assigned, there will be no particular obstacle during communication. As a result of assigning an arbitrary frame to the subnetwork 3 to which a frame is to be assigned, communication interference does not occur in the same manner even if this is a different frame from the other subnetwork 3.

  When the process proceeds to step S15, there is a case where another subnetwork 3 exists within the range of the distance C with the one management device 30a as the center, and there is a possibility that communication interference may occur. In such a case, as shown in FIG. 7, the sub-network 3a centered on one management device 30a and the sub-frames 3b that are different from each other in the successive frames constituting each OFDMA super-frame between the other sub-networks 3b and 3c Allocate a frame. That is, the sub-network 3a to which the frame is to be allocated is controlled to allocate different frames so as not to overlap with frames already used by the other sub-networks 3b and 3c. In other words, the control is performed so that different frames in the continuous frame group constituting each of the OFDMA superframes are allocated between the plurality of sub-networks 3.

  However, when all the frames are filled by the other sub-network 3 and there is no frame that can be allocated, the process proceeds to step S16, and frames having different frequency channels are allocated to each other. For example, as shown in FIG. 8, when all the frames are filled with another sub-network 3, it is assumed that frame 1 is allocated to the sub-network 3 to which a frame is to be allocated. Also in such a frame 1, another subnetwork 3 has already been assigned. For this reason, frames having different frequency channels are assigned to each other in the frame 1. For example, when 30 subchannels are prepared in advance, this is divided into three and assigned to different subnetworks 3. That is, control is performed so that different frequency subchannels are allocated to the same frame in the continuous frame group constituting each superframe of OFDMA between the subnetworks 3. Thereby, since the frequency axes in performing OFDMA communication can be made different between the sub-networks 3, it is possible to prevent mutual communication interference.

  If the OFDMA sub-channel is already occupied by another sub-network in step S16 and it is difficult to make a new assignment, the process proceeds to step S17.

  When the process proceeds to step S17, the base station 20 cannot allocate different frames and different frequency subchannels between the sub-networks 3 by any of the methods of steps S15 and S16. In such a case, as shown in FIG. 9B, the communication device 40 and the management device 30 in each subnetwork 3 are controlled so as to lower the communication output. As a result, the distance C for determining the presence or absence of communication interference can be made smaller than before the communication output as shown in FIG. As a result, it is possible to further reduce the possibility that the subnetwork 3 is included in the distance C in the determination in step S14.

  Incidentally, you may make it return to either of steps S11-S14 again after transfering to this step S17. Further, the communication output (radio wave output) in step S17 is not limited to all the sub-networks but may be a part thereof.

  In the multi-hop wireless communication system 1 capable of assigning OFDMA frames to the sub-network 3 based on the above-described method, the location information of the management device 30 and thus the sub-network 3 is effectively used, and the sub-network 3 is adapted to the situation of the sub-network. Flexible and accurate channel setting. As a result, the accommodation density of the sub-network 3 per unit area can be improved, and further, signal interference can be reduced. As a result, a multi-hop wireless communication system can be configured on a large scale. For this reason, when performing emergency communication in the event of a disaster, etc., when it is required to improve the capacity per unit area of the subnetwork 3, or when it is difficult to predict the status of the subnetwork 3, A more remarkable effect can be achieved.

  The present invention is not limited to the above-described embodiment. For example, the method of step S15 and step S16 may be combined. That is, when another subnetwork 3 exists within a predetermined distance range from the subnetwork 3 from which communication is newly started, different frames in the continuous frame group constituting each OFDMA superframe are allocated between the subnetworks 3. In addition, different frequency subchannels may be allocated.

  Furthermore, the present invention is not limited to the embodiment described above. Any one that executes the processing operation of steps S15, S16, and S18 based on the positional relationship between the subnetworks determined from the positional information acquired from the management device 30 in each subnetwork 3 may be used. Of course it is good.

  An embodiment of the multi-hop wireless communication system 1 to which the present invention is applied will be described. For example, as shown in FIG. 10A, it is assumed that frames # 13 to # 15 can be allocated to the subnetwork 3 in the continuous frame group constituting each superframe. Further, it is assumed that the management devices 30b to 30d of the other sub-networks 3 with the management device 30a as the center are in a positional relationship as shown in FIG. Further, as shown in Table 1, it is assumed that frame # 13 is already assigned to the management device 30b, frame # 14 is already assigned to the management device 30c, and frame # 15 is already assigned to the management device 30d.

  For this reason, since all the management devices 30b to 30d of the other subnetwork 3 are included in the range of the distance C with respect to the management device 30a, there is a possibility of causing communication interference. In addition, usable frame # 13 to frame # 15 are all filled with these other sub-networks 3. Accordingly, since the process of step S15 described above cannot be executed, the process proceeds to step S16.

  In step S16, as shown in FIG. 11, the subnetwork 3 including the management device 30a is allocated to the frame # 13. Although this frame # 13 is already assigned to the management device 30b, it is possible to prevent communication interference by using different subchannels (segment 1, segment 2) with the management device 30a. Become.

DESCRIPTION OF SYMBOLS 1 Multihop radio | wireless communications system 2 Network 3 Subnetwork 5 Database 6 Public communication network 8 GPS satellite 20 Base station 21 Position information management part 22 Frame allocation part 30 Management device 31 Position information part 40 Communication device

Claims (6)

In a multi-hop wireless communication system that performs wireless communication based on the OFDMA scheme in a white space band,
A sub-network having one or more communication devices and a management device that performs wireless communication based on the OFDMA scheme with the communication devices;
A base station managing a plurality of the sub-networks;
Position information transmitting means for transmitting position information to the management device in the sub-network,
The base station acquires the position information received from the position information transmitting means by the management device in each subnetwork, and based on the positional relationship between the subnetworks determined from the acquired position information, Assign any frame and any frequency subchannel in a continuous frame group constituting each superframe of OFDMA or different frames in a continuous frame group constituting each superframe of OFDMA between the sub-networks. A multi-hop wireless communication system characterized by deciding whether to allocate or to assign different frequency subchannels in the same frame in a continuous frame group constituting each OFDMA superframe between the sub-networks. The base station allocates the empty frame to the sub-network to newly start communication when there is an empty frame that can be used in a continuous frame group constituting the super frame. Multi-hop wireless communication system. The base station, based on the positional relationship between the sub-networks, if there are no other sub-networks within a predetermined distance range of the respective sub-networks, the base station constitutes a continuous frame constituting each OFDMA superframe between the sub-networks. The multi-hop wireless communication system according to claim 2, wherein any frame in the group and any frequency subchannel are allocated. When there is another subnetwork within a predetermined distance from the subnetwork where communication is newly started, the base station transmits different frames in successive frames constituting each OFDMA superframe between the subnetworks. The multi-hop wireless communication system according to claim 3, wherein the multi-hop wireless communication system is assigned, or different frequency subchannels are assigned to the same frame in a continuous frame group constituting each OFDMA superframe between the sub-networks. When there is another subnetwork within a predetermined distance from the subnetwork where communication is newly started, the base station transmits different frames in successive frames constituting each OFDMA superframe between the subnetworks. The multi-hop wireless communication system according to claim 4, wherein the multi-hop wireless communication system is further assigned and further assigned different frequency subchannels. If the base station cannot allocate different frames and different frequency subchannels between the sub-networks by any of the methods described above, the base station can output communication to the communication device and the management device in each sub-network. The multi-hop wireless communication system according to any one of claims 1 to 5, wherein the multi-hop wireless communication system is controlled to be low.

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