JP2012015794A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system which reduces transmission delay caused by relay by effectively utilizing frequency resources while sharing frequencies with a plurality of nodes.SOLUTION: A radio communication system transmitting data from a transmission source node 1A to a transmission destination node 1C through a relay node 1B comprises: the transmission source node 1A which includes a frequency scan part 13 detecting usage state of each frequency, a transmission frequency determination part 13 determining a transmission frequency based on the usage state of each frequency, a frequency information transmission part 13 transmitting the determined transmission frequency to the relay node, and a data transmission part 13; and the relay node 1B which includes the frequency scan part 13 detecting the usage state of each frequency, a determination part 13 determining a relay frequency based on frequency information and the usage state of each frequency, a frequency information transmission part 13 transmitting the relay frequency to the transmission destination node, and a data transmission part 13 performing relay transmission by using the relay frequency.

Description

  The present invention relates to a wireless communication system that exchanges route information such as an OLSR (Optimized Link State Routing) protocol and performs communication using a plurality of frequency frequencies between a plurality of wireless communication devices.

  Conventionally, ad hoc communication is known in which route information is exchanged between a plurality of wireless communication devices to optimize the route.

  Patent Document 1 discloses an ad hoc network technology that improves communication capacity by maintaining the latest route information.

JP 2009-296262 A

In CSMA / CA used in wireless LANs, etc., when a plurality of nodes share the same frequency and other nodes are not communicating (frequency is not used), it transmits its own node. Do. Therefore, in ad hoc communication, when a communication method in which a plurality of nodes share the same frequency as in CSMA / CA is adopted, the transmission source node and the adjacent relay node cannot transmit at the same time. There was a problem that the delay became remarkable.
Further, in order to effectively use frequency resources, a communication system that manages unused frequencies requires a base station that controls each node.
It is an object of the present invention to provide a wireless communication system that reduces transmission delay due to relay while sharing frequency between a plurality of nodes by effectively using frequency resources.

One embodiment to solve the problem is:
In a wireless communication system in which data is transmitted from a transmission source node (wireless communication device 1A) to a transmission destination node (wireless communication device 1C) via a relay node (wireless communication device 1B), the transmission source node (wireless communication device 1A) is A frequency scanning unit (control unit 13) that scans a plurality of frequencies to detect a usage state of each frequency, and a transmission frequency determination that determines a transmission frequency based on the usage state of each frequency detected by the frequency scanning unit A frequency information transmission unit (control unit 13, modem unit 16, radio unit 17, antenna 18) that transmits the transmission frequency determined by the transmission frequency determination unit to the relay node as frequency information, A data transmission unit for transmitting data using the transmission frequency determined by the transmission frequency determination unit (control unit 13, modem unit 16, radio unit 17, The relay node (wireless communication device 1B) is transmitted from the transmission source node and a frequency scanning unit (control unit 13) that scans a plurality of frequencies and detects a use state of each frequency. A relay frequency determining unit (control unit 13) for determining a relay frequency to be used in relay transmission based on the frequency information and a use state of each frequency detected by the frequency scanning unit of the own node; and the relay frequency determining Frequency information transmission unit (control unit 13, modem unit 16, radio unit 17, antenna 18) for transmitting the relay frequency determined by the unit to the destination node as frequency information, and the relay frequency determined by the relay frequency determination unit Is used to relay and transmit data transmitted from the transmission source node (control unit 13, modem unit 16, radio unit 17, antenna 1). ) And a wireless communication system characterized by comprising.

  In the relay node, a plurality of frequencies are scanned to detect the usage state of each frequency, the frequency information transmitted from the transmission source node (transmission frequency of the transmission source node), and each frequency detected by the frequency scanning unit Since the relay frequency used for relay transmission is determined based on the use state of the network, the frequency resource can be used effectively while sharing the frequency among a plurality of nodes, and the transmission delay due to relay is reduced. be able to.

1 is a block diagram showing a configuration of a wireless communication device that constitutes a wireless communication system according to an embodiment of the present invention. Explanatory drawing which similarly shows an example of communication between radio | wireless communication apparatuses. Explanatory drawing at the same time when wireless communication devices relay at a single frequency. Explanatory drawing at the same time when wireless communication devices relay at a plurality of frequencies. Explanatory drawing when wireless communication devices also exchange sensing information and routing information. Similarly, an explanatory diagram when wireless communication devices relay at four frequencies. 6 is a flowchart illustrating an example of a channel determination procedure when the wireless communication devices are not multiplexed. Explanatory drawing which shows an example of the communication image in case the wireless communication apparatuses are not multiplexed similarly. The flowchart which shows an example of the channel determination procedure in the case of multiplexing in the same radio communication apparatus. Explanatory drawing which shows an example of a communication image in case the same radio communication apparatus is multiplexed. 6 is a flowchart illustrating an example of multi-channel determination processing when communication is performed as a transmission source in the same wireless communication device. 7 is a flowchart showing an example of multi-channel determination processing when communication is performed as a repeater in the same wireless communication device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A wireless communication device 1 (wireless communication devices 1A, 1B, and 1C described later) realized by, for example, a software defined wireless device (not limited to this) according to an embodiment of the present invention is shown in detail in FIG. An operation unit 11 for operation by a user, an interface unit 12 for communicating with a client PC or server S, ad hoc routing processing, frequency scanning processing, transmission (relay) frequency determination processing, multi-frequency determination, which will be described later In order to perform independent multiplex communication with the control unit 13 that controls each part of the wireless communication device 1 by performing various processes including the process, the ROM 14 that stores the operation program, and the RAM 15 that stores the operation program and control information. And a plurality of (for example, five) modem units 16 that are modulation / demodulation functions and a plurality (for example, modulation / demodulation functions for independent multiplex communication) A radio unit 17 of the example, if 5 groups), and has an antenna 18 for radiating a communication wave.

  Next, the wireless communication device 1 having such a configuration uses ad hoc communication in this embodiment, and adopts an OLSR (Optimized Link State Routing) protocol as an example of the ad hoc protocol. Here, an outline of OLSR will be briefly described.

  OLSR is a proactive protocol that always exchanges route information, and is characterized in that flooding is performed by collecting a minimum number of relay nodes (MPR: Multipoint Relay). In OLSR, path construction is performed mainly by exchanging HELLO packets and TC (Topology Control) packets.

  The HELLO packet is transmitted from each node and includes link information of the own node and information such as MPR and MPR selector. MPR is a node in charge of relay, and each node is selected with reference to link information of one hop ahead of an adjacent node in order to perform efficient flooding. An MPR selector is a node that has selected its own node as an MPR.

  If only MPR is selected, a communication path is not yet established. Therefore, in OLSR, the topology of the entire network is constructed using TC packets. The TC packet includes information on the MPR selector set and is transmitted from each node selected as the MPR. The TC packet is flooded throughout the network by the MPR.

  With this TC packet, all nodes in the network can acquire information on MPR and its MPR selector set. Each node calculates a shortest route to the transmission destination (destination) based on the information and creates a route table. In one embodiment of the present invention, information on channels that can be used is included in the HELLO packet, so that the channels that can be used by nodes in the communication area can be recognized.

  As shown in FIG. 2, a wireless communication device 1 using an ad hoc network according to an embodiment of the present invention communicates between a plurality of wireless communication devices and is multiband compatible. In the embodiment, an example of five channels is shown, but the present invention is not limited to this. In such a wireless communication device 1, communication is performed with other wireless communication devices 1 in the communication area by, for example, half-duplex communication. Note that the present invention is not limited to half-duplex communication. Half-duplex communication is a communication method in which data cannot be transmitted or received from both sides at the same time in bidirectional communication, and transmission is only possible from one direction at a time interval. In this case, as shown in FIG. 3, the first packet may be transmitted from the first wireless communication device 1A to the second wireless communication device 1B at the first frequency F1 at time t1, but at time t2, the second packet is transmitted. Is continuously transmitted from the first wireless communication device 1A to the second wireless communication device 1B, the first packet is being transmitted at the same frequency F1 from the second wireless communication device 1B to the third wireless communication device 1C. Yes, communication at the same frequency cannot be performed simultaneously. For this reason, in order to transmit data from the first wireless communication device 1A that is the transmission source node to the third wireless communication device 1C that is the transmission destination node, the second wireless communication that is the relay node is transmitted from the first wireless communication device 1A. It takes more than twice the time to transmit to the machine 1B.

  On the other hand, according to the case of FIG. 4, the first packet is transmitted from the first wireless communication device 1A to the second wireless communication device 1B at the first frequency F1 at time t1, and at time t2, the second wireless communication is performed. Since the first packet is transmitted from the device 1B to the third wireless communication device 1C by the channel of the second frequency F2 instead of the first frequency F1, the second packet is transmitted from the first wireless communication device 1A to the second wireless communication device 1B. Can be transmitted at the first frequency F1. Therefore, this makes it possible to shorten the data transmission time from the first wireless communication device 1A to the third wireless communication device 1C as compared with the case of FIG. This reduction in transmission time becomes more significant as the number of relay nodes increases.

In one embodiment of the present invention, frequency scanning (five frequencies) is periodically performed, and the result is included in the above-described HELLO packet and flooded to the peripheral nodes as sensing information.
As shown in FIG. 5, wireless communication is performed by exchanging HELLO packets including sensing information between a plurality of wireless communication devices 1A, 1B, and 1C using a control channel, for example, frequency F1 as described later. The control unit 13 of the device 1 can always recognize the state of a nearby wireless communication device (such as a frequency that can be used for transmission at a link destination). In this embodiment, the example in which F1 is set as the control channel is shown to stabilize the transmission of the HELLO packet, but other frequencies are used as appropriate without necessarily setting the dedicated control channel. However, if a collision does not occur, an equivalent technical effect can be obtained.

  In one embodiment of the present invention, as shown in FIG. 6, based on sensing information exchanged between a plurality of wireless communication devices 1A, 1B, 1C,..., Wireless communication devices 1A, 1B, 1C,. In the meantime, it is possible to perform multiplex communication not only at one frequency but at a plurality of frequencies. As a result, the communication capacity can be automatically expanded according to the communication status.

-Frequency determination process The transmission (relay) frequency determination process in a transmission source node and a relay node is demonstrated.
In the present embodiment, there are five frequency bands from F1 to F5. F1 is used as a control channel for notifying transmission / reception of the above-mentioned HELLO packet and TC packet, transmission (relay) frequency information to be described later, destination information of data to be transmitted, and the like. The frequency is used for data transmission used for transmitting data packets.

  First, the frequency determination process of the transmission source node will be described. The control unit 13 of the transmission source node periodically performs frequency scanning and acquires information on available frequencies (sensing information). Also, the sensing information included in the HELLO packet transmitted from the relay node (MPR) is acquired. Then, a frequency that can be used for transmission by the own node and the relay node (a frequency at which vacancy is detected in any node) is determined as a transmission frequency. When there are a plurality of usable frequencies, an arbitrary frequency (for example, the frequency having the smallest F number) is selected.

Next, the relay node frequency determination process will be described. The control unit 13 of the relay node periodically performs a frequency scan and acquires information on available frequencies (sensing information). Also, sensing information included in the HELLO packet transmitted from the transmission destination node (or the next relay node) is acquired.
Then, the transmission source node (or the previous relay node) determines the frequency that can be used for transmission at the local node and the transmission destination node (or the next relay node) (the frequency at which vacancy is detected at any node). A frequency other than the transmitted frequency is determined as a relay frequency. When there are a plurality of usable frequencies, an arbitrary frequency (for example, the frequency with the smallest number) is selected.
The transmission frequency determined by the transmission source node (or the previous relay node) is transmitted to the relay node as frequency information and notified using the control channel F1.
When there is no usable frequency, transmission is performed after the frequency determined by the transmission source node (or the previous relay node) becomes available by CSMA / CA.

Specific Communication Example Next, a specific communication example between the plurality of wireless communication devices 1A, 1B, 1C, and 1D will be described in detail with reference to FIGS.
In the description of FIG. 7 and FIG. 8, the transmission frequency of the wireless communication device 1A is determined as F2, the transmission frequency of the wireless communication device 1B is determined as F3, and the transmission frequency of the wireless communication device 1C is determined as F2 by the frequency determination process described above. Shall.
In the flowchart of FIG. 7, the first wireless communication device 1A decides to use F2 for transmission based on its own sensing information, and uses F1, and uses “F2 for communication with the second wireless device 1B. To the second wireless communication device 1B (step S1). The second wireless communication device 1B decides to use F3 for communication with the third wireless device 1C based on the information that the first wireless communication device 1A uses F2 and the sensing information that the second wireless communication device 1A uses. The user uses F3 for communication with the third wireless device 1C, and notifies the third wireless communication device 1C that the adjacent wireless device uses F2 (step S2). The third wireless communication device 1C has information that the second wireless communication device 1B uses F3 and that there is a wireless device using F2 in the communication area of the second wireless communication device 1B Based on the sensing information, the F4 is determined to be used, and the F4 uses the F4 for communication with the fourth wireless communication device 1D, and the fourth wireless communication device indicates that the adjacent wireless device uses the F3. 1D is notified (step S3). Thereafter, the first wireless communication device 1A to the fourth wireless communication device 1D perform data packet transmission using the secured frequency (step S4). As a result, as shown in FIG. 8, since the wireless communication devices in the communication area communicate using different frequencies, from the first wireless communication device 1A to the fourth wireless communication device 1D. Transmission delay can be reduced.
When the fourth wireless communication device 1D further transfers data to the fifth wireless communication device, F2 is selected if the rule of selecting the lowest numbered frequency among the available frequencies is adopted. It will be.

Further, a case where multiplexed communication is performed using a plurality of channels in the flowchart of FIG. 9 will be described. In this example, description will be made on the assumption that the frequency band exists from F1 to F7.
The first wireless communication device 1A decides to use F2 · F3 for transmission based on its own sensing information, and uses F1 to “use F2 · F3 for communication with the second wireless device 1B. (Step S5) The second wireless communication device 1B uses the third wireless communication device 1B based on the information that the first wireless communication device 1A uses F2 and F3 and the sensing information that it has. Decide to use F4 / F5 for communication with Aircraft 1C, use F1, use F4 / F5 for communication with 3rd Radio 1C, and use adjacent radios for F2 / F3 (Step S6) The third wireless communication device 1C uses the F4 / F5 for the second wireless communication device 1B and communicates with the second wireless communication device 1B. None using F2 or F3 in the area Decides to use F6 / F7 based on the information that there is a device and the sensing information that it has, and uses F2 / F3 for communication with the fourth wireless communication device 1D and the adjacent wireless The wireless communication device notifies the fourth wireless communication device 1D that the device is using F4 / F5 (step S7), and then the first wireless communication device 1A to the fourth wireless communication device 1D use the reserved multiple channels. Then, packet transmission is performed (step S8).

As a result, as shown in FIG. 10, the wireless communication devices in the communication area perform multiplex communication using channels of different frequencies. Accordingly, the first wireless communication device 1A to the fourth wireless communication device 1D can simultaneously perform communication with a communication capacity almost twice that in the case of FIG. 7 and FIG. 8, so that the communication speed can be improved.
If the fourth wireless communication device 1D further transfers data to the fifth wireless communication device and adopts the rule of selecting the lowest numbered frequency among the available frequencies, F2 and F3 are set. Will choose.

Communication processing in each wireless communication device Next, the multi-channel determination processing for realizing the above-described multi-channel communication processing, which is performed in the control unit (channel determination unit) 13 of each wireless communication device, is described with reference to FIGS. This will be described in detail with reference to the flowchart shown in FIG.
First, a case where the wireless communication device 1 according to an embodiment of the present invention functions as a transmission source node, that is, a case where, for example, the wireless communication device 1A transmits a signal to the wireless communication device 1B will be described. The control unit 13 having a frequency determination function of the wireless communication device 1 periodically includes HELLO including sensing information with other wireless communication devices 1 existing in the communicable area according to a program stored in the ROM 14 or the like. Packets are transmitted and received (step S11). In the control unit 13 of the wireless communication device 1, when a transmission task is generated as a transmission source (step 12), the number of usable frequencies is determined based on the sensing information described above (step S13).

  That is, the control unit 13 of the wireless communication device 1 determines how many of the frequencies F1 to F5 shown in the explanatory diagram of FIG. 10 can be used, and sets the operation setting by the user (number of frequencies used, priority) The frequency (single or plural) to be actually used is selected and determined from the available frequencies (step S14 to step S17). In addition, the wireless communication device 1 responds to changes in the communication status among a plurality of wireless communication devices by repeatedly returning to step 11 and repeating while the communication continues according to the flowchart shown in FIG. Change the frequency to be used and its number.

  Next, in the flowchart of FIG. 12, a case where the wireless communication device 1B functions as a relay node, that is, a case where the wireless communication device 1B receives a signal from the wireless communication device 1A and transfers the signal to the wireless communication device 1C will be described. The control unit 13 having a frequency determination function of the wireless communication device 1 periodically includes HELLO including sensing information with other wireless communication devices 1 existing in the communicable area according to a program stored in the ROM 14 or the like. Packets are transmitted and received (step S21). When the control unit 13 of the wireless communication device 1B recognizes that it should function as a relay node from the destination information of the received transmission data, the sensing information acquired from the modem unit 16 and the wireless unit 17 and the transmission source node The number of frequencies that can be used by itself is determined based on the frequency information transmitted from (step S24).

  That is, the control unit 13 of the wireless communication device 1B determines which of the remaining frequencies F1 to F5 shown in the explanatory diagram of FIG. 10 is usable, and uses which frequency (single or plural). Is determined based on the operation setting by the user (number of frequencies to be used, order of frequencies to be preferentially selected), etc. (step S25 to step S28). In addition, the wireless communication device 1 responds to a change in the communication status among the plurality of wireless communication devices by repeatedly returning to step 21 and repeating while the communication continues according to the flowchart shown in FIG. Change the frequency to be used and its number.

A plurality of the various embodiments described above can be implemented at the same time. With these descriptions, those skilled in the art can realize the present invention, but various modifications of these embodiments can be conceived. It is easy for a person skilled in the art and can be applied to various embodiments without inventive ability. Therefore, the present invention covers a wide range consistent with the disclosed principle and novel features, and is not limited to the above-described embodiments.
For example, in the above-described embodiment, the case of a software wireless communication device that performs half-duplex communication using five channels has been described as an example. However, the number of channels, the communication form, and the form of the wireless communication device are described in the case of the embodiment. The present invention is not limited, and the present invention can be implemented with any number of channels, communication forms, and wireless communication apparatuses.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication device, 11 ... Operation part, 12 ... Interface part, 13 ... Control part, 14 ... ROM, 15 ... RAM, 16 ... Modem part, 17 ... Wireless part, 18 ... Antenna.

Claims (1)

In a wireless communication system for transmitting data from a source node to a destination node via a relay node,
The source node is
A frequency scanning unit that scans a plurality of frequencies to detect a use state of each frequency; and
Based on the usage state of each frequency detected by the frequency scanning unit, a transmission frequency determining unit that determines a transmission frequency;
A frequency information transmission unit that transmits the transmission frequency determined by the transmission frequency determination unit to the relay node as frequency information;
A data transmission unit that transmits data using the transmission frequency determined by the transmission frequency determination unit, and
The relay node is
A frequency scanning unit that scans a plurality of frequencies to detect a use state of each frequency; and
A relay frequency determining unit that determines a relay frequency to be used in relay transmission based on the frequency information transmitted from the transmission source node and a use state of each frequency detected by the frequency scanning unit of the own node;
A frequency information transmitting unit that transmits the relay frequency determined by the relay frequency determining unit to the destination node as frequency information;
A data transmission unit that relays and transmits data transmitted from the transmission source node using the relay frequency determined by the relay frequency determination unit;
A wireless communication system comprising:

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