JP2009071581A - Radio apparatus, and radio network using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio apparatus capable of improving reliability in broadcasting communication. <P>SOLUTION: Each radio apparatus includes a reception module 21 for receiving emergent packets PKT1, PKT3, PKT4, and outputting bit strings [1, 1, 1, 1, -1], [1, -1, 1, -1, -1], [1, -1, 1, 1, 1] indicating information included in the emergent packets PKT1, PKT3, PKT4 to a synthesizer 50 when the transfer of the labels L of the received emergent packets PKT1, PKT3, PKT 4 is started by a transmission module 47. The synthesizer 50 synthesizes the bit strings [1, 1, 1, 1, -1], [1, -1, 1, -1, -1], [1, -1, 1, 1, 1], and generates the same bit string [1, -1, 1, 1, -1] being the same as the bit string generated by a generation source. The transmission module 47 transmits the bit string [1, -1, 1, 1, -1]. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless device and a wireless network using the wireless device, and more particularly to a wireless device that transfers a broadcast packet and a wireless network using the wireless device.

  Techniques described in Non-Patent Documents 1 to 4 are known as techniques for improving communication reliability.

  The technique described in Non-Patent Document 1 is a technique for improving communication reliability by a space diversity function using a MIMO (Multi-Input Multi-Output) channel.

  The technique described in Non-Patent Document 2 is a technique for improving communication reliability by retransmitting a packet by an acknowledgment from a receiving terminal.

  Furthermore, the technique described in Non-Patent Document 3 is a technique for improving communication reliability by using a cooperative relay terminal.

Furthermore, the technique described in Non-Patent Document 4 is a technique for improving communication reliability by using network coding.
I. Telatar, “Capacity of multi-antenna Gaussian channels”, Bell Labs Technical Memorandum, June 1995. EJ Weldon, “An Improved selection repeat ARQ strategy”, IEEE Trans. Commun., Vol. COM-30, pp. 480-486, Mar. 1982. JN Laneman, David NC Tse, GW Wornell, “Cooperative diversity in wireless networks: efficient protocols and outage behavior”, IEEE Trans. Information Theory, vol. 50, No. 12, pp. 3062-3080, 2004. R. Ahlswede, N. Cai, SY. R. Li, RW Yeung, “Network Information Flow”, IEEE Trans. Information Theory, vol. 46, No. 4, pp. 1204-1216, 2000.

  However, since the techniques described in Non-Patent Documents 1 to 4 are techniques for unicast communication between two terminals, there is a problem that it is difficult to apply to broadcast communication.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a radio apparatus capable of improving the reliability in broadcast communication.

  Another object of the present invention is to provide a wireless network including a wireless device capable of improving reliability in broadcast communication.

  According to the present invention, the wireless device is a wireless device that transfers a broadcasted packet, and includes a reception unit and a transfer unit. The receiving means receives a plurality of packets from a plurality of different wireless devices. The transfer unit combines the plurality of packets received by the receiving unit, and transfers the combined packet.

  Preferably, the transfer unit starts combining the plurality of packets and transferring the combined packet before reception of the plurality of packets by the receiving unit is completed.

  Preferably, each of the plurality of packets includes emergency information.

  Preferably, the wireless device further includes a determination unit. The determination means detects identification information for identifying the type of information included in the packet from the head of each of the plurality of packets, and whether the plurality of packets include the same identification information based on the detected plurality of identification information Determine whether or not. Then, when the determination unit determines that the plurality of packets include the same identification information, the transfer unit starts combining the plurality of packets and transferring the combined packet.

  Preferably, the transfer unit includes a synthesis unit, a bit determination unit, and a transmission unit. The combining means combines a plurality of bit strings included in the plurality of packets. The bit determination unit performs bit determination on the combined bit string combined by the combining unit. The transmission means transmits the bit string determined by the bit determination means.

  Preferably, the transfer unit includes a plurality of first bit determination units, a combination unit, a second bit determination unit, and a transmission unit. The plurality of first bit determination means are provided corresponding to the plurality of packets, and each bit determines data included in the corresponding packet. The synthesizing unit synthesizes a plurality of bit strings whose bits are determined by the plurality of first bit determining units. The second bit determining means performs bit determination on the combined bit string combined by the combining means. The transmitting means transmits the bit string determined by the second bit determining means.

  Preferably, the receiving means is arbitrarily selected from N (N is an integer equal to or larger than 2) channel groups consisting of an integer equal to or greater than a division value obtained by dividing the transmission time at the transmission source of a plurality of packets by the delay time in packet transfer by the transfer means. A plurality of packets are received using m (m is a positive integer) channels included in the first channel group selected in (1). The transfer means transfers the composite packet using n (n is a positive integer) channels included in the N channel groups and included in the second channel group different from the first channel group. To do.

  Preferably, each of the plurality of packets has a packet size equal to or larger than a reference size. The N channel groups are composed of three or more channel groups.

  Preferably, when the plurality of packets include an error, the transfer unit combines and transfers the plurality of packets.

  According to the present invention, a wireless network includes the wireless device according to any one of claims 1 to 9.

  In the present invention, a plurality of packets transmitted from a plurality of wireless devices to one wireless device in the course of packet broadcast are combined and transferred. As a result, the packets are transferred one after another while retaining as much information as possible about the packets transmitted from the wireless device as the transmission source.

  Therefore, according to the present invention, reliability in broadcast communication can be improved.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram of a wireless network according to an embodiment of the present invention. The wireless network 100 includes wireless devices 1 to 9.

  The wireless devices 1 to 9 are arranged in a wireless communication space and are mounted on a vehicle, for example. The antennas 11 to 19 are attached to the wireless devices 1 to 9, respectively. The wireless devices 1 to 9 autonomously configure a network between a transmission source and a transmission destination, and broadcast packets in the configured network. In this case, each of the wireless devices 1 to 9 spreads the packet PKT and transmits the spread packet PKT using one of the frequency channels Ch1 to Ch4 (hereinafter referred to as “channels Ch1 to Ch4”). Each of the wireless devices 1 to 9 transfers the packet received from the wireless device on the transmission side to the wireless device on the transmission destination side by a method described later.

[Embodiment 1]
FIG. 2 is a schematic block diagram showing a configuration of the wireless device 1 shown in FIG. 1 in the first embodiment. The wireless device 1 includes an antenna 20, reception modules 21 to 24, switches SW1 to SW4, terminals TM1 to TM8, delay circuits 25 to 28, multipliers 29 to 32, a synthesis module 33, and a bit determination unit. 34, buffers 35 to 39, a label check / scheduling module 40, a timer 41, a MAC (Media Access Control) module 42, and transmission modules 43 to 47.

  The reception modules 21 to 24 and the transmission modules 43 to 47 are equal to or less than the number of frequency channels. The number of despreaders and bit determiners provided in each of the receiving modules 21 to 24 is equal to or less than the number of spreading codes.

  The antenna 20 constitutes each of the antennas 11 to 19 shown in FIG.

  The reception modules 21 to 24 and the transmission modules 43 to 47 are arranged in the physical layer, and switches SW1 to SW4, terminals TM1 to TM8, delay circuits 25 to 28, multipliers 29 to 32, a synthesis module 33, a bit determination unit 34, The buffers 35 to 39, the label check / scheduling module 40, the timer 41, and the MAC module 42 are arranged in the MAC layer.

  The antenna 20 receives the transmission signal Tx from any of the transmission modules 43 to 47, and transmits the received transmission signal Tx to other wireless devices via the wireless communication space. The antenna 20 receives a signal from another wireless device via the wireless communication space, and outputs the received reception signal Rx to any of the reception modules 21 to 24.

  The reception modules 21 to 24 receive the transmitted packets PKT through the channels Ch1 to Ch4, respectively, and perform demodulation, inverse spread spectrum, and the like on the received packets PKT. Then, the receiving modules 21 to 24 output the demodulated packet PKT to the switches SW1 to SW4.

The reception module 21 includes despreaders 211 to 214 and bit determiners 215 to 218. Condensate diffuser 211 to 214 receives the received signal Rx from the antenna 20, the received reception signal Rx and inversion spectral spreading with the spread code _c 1 to c ₄ respectively, a signal _y 1 ~y ₄ was the reverse spread spectrum The data are output to bit determiners 215 to 218, respectively.

Bit determiners 215 to 218 receive signals y ₁ to y ₄ from despreaders 211 to 214, respectively, and perform bit determination on the received signals y _{1 to} y ₄ to generate bit strings B _{1 to} B ₄ . Then, the bit determiners 215 to 218 output the bit strings B1 to B4 to the switches SW1 to SW4, respectively.

  The receiving modules 22 to 24 have the same configuration as the receiving module 21 except that the packets PKT are received by the channels Ch2 to Ch4, respectively. Accordingly, each of the bit determiners 215 to 218 of the reception modules 22 to 24 outputs the generated bit string to the corresponding switch.

  The switch SW1 is connected to the terminal TM1 or the terminal TM2 by a signal SS1 from the label check / scheduling module 40. More specifically, the signal SS1 has an H (logic high) level or an L (logic low) level, and the switch SW1 receives the H level signal SS1 from the label check / scheduling module 40 and is connected to the terminal TM1. When the L-level signal SS1 is received from the label check / scheduling module 40, it is connected to the terminal TM2.

  Similarly, the switches SW2 to SW4 are connected to terminals TM3, TM5, TM7 or terminals TM4, TM6, TM8 by signals SS2 to SS4 from the label check / scheduling module 40, respectively.

  Terminals TM1, TM3, TM5, and TM7 are connected to delay circuits 25 to 28, respectively. Terminals TM2, TM4, TM6, and TM8 are connected to buffers 35 to 38, respectively.

  Delay circuits 25 to 28 respectively delay bit strings B1 to B4 received from terminals TM1, TM3, TM5, and TM7 by times Δ (t1) to Δ (t4), and multiply the delayed bit strings B1 to B4, respectively. Output to 29-32.

The multiplier 29-32, respectively, the delay circuits 25 to 28 receives a bit string B1~B4 from each multiplied by the weight coefficient _CW 1 _{~CW 4} bit string B1~B4 having received them, the multiplication result B1 * _CW 1, B2 * CW ₂ , B3 * CW ₃ , and B4 * CW ₄ are output to the synthesis module 33.

The synthesis module 33 receives the multiplication results B1 * CW ₁ , B2 * CW ₂ , B3 * CW ₃ , B4 * CW ₄ from the multipliers 29 to 32, respectively, and the received multiplication results B ₁ * CW ₁ , B 2 * CW. ₂ , B3 * CW ₃ , B4 * CW ₄ are combined by a method described later, and the combined signal Z is output to the bit decision unit 34.

  The bit determination unit 34 receives the combined signal Z from the combining module 33, performs bit determination on the received combined signal Z, and outputs the determination result BG to the buffer 39 and the transmission module 47.

  Buffers 35 to 38 receive bit strings B1 to B4 from terminals TM2, TM4, TM6, and TM8, respectively, and hold the received bit strings B1 to B4. The buffer 39 receives the bit string BG from the bit decision unit 34 and holds the received bit string BG.

  The label check / scheduling module 40 determines whether each of the packets PKT1 to PKT4 received by the wireless apparatus 1 includes emergency information based on each of the bit strings B1 to B4 and BG stored in the buffers 35 to 39. To do.

  Then, the label check / scheduling module 40 generates an H level signal for the switch corresponding to the packet including the emergency information among the packets PKT1 to PKT4, and outputs the generated H level signal to the corresponding switch. At the same time, the combined packet (= consisting of the bit string BG) stored in the buffer 39 is transferred by the cut-through method described later.

  In the present invention, “transfer by the cut-through method” means that transfer of a plurality of packets PKT is started before reception of a plurality of packets PKT from a plurality of wireless devices is completed.

  On the other hand, the label check / scheduling module 40 generates an L level signal for packets that do not include emergency information among the packets PKT1 to PKT4, and outputs the generated L level signal to the corresponding switch. The PKT is transferred by a method described later.

When the timer 41 receives the waiting time T _CD from the label check / scheduling module 40, the timer 41 measures the waiting time T _CD , and when the waiting time T _CD elapses, notifies the label check / scheduling module 40 that the waiting time has ended. To do.

  The MAC module 42 performs an error check on the packet PKT stored in the buffers 35 to 39, and sends the packet PKT after the error check to the upper layer. Further, the MAC module 42 outputs the packet PKT from the upper layer to the transmission modules 43 to 46.

  The transmission modules 43 to 46 transmit the packet PKT from the upper layer through the antenna 20 as the transmission signal Tx. The transmission module 47 transmits the label L stored in the buffer 39 and also transmits the signal (= combined packet) from the bit determination unit 34. In this case, the transmission modules 43 to 46 transmit the packet PKT using the channels Ch1 to Ch4, respectively.

  In addition, the transmission module 47 transmits the packet through a channel different from the reception channels in the reception modules 21 to 24. For example, when the reception module 21 receives a packet to be combined, the transmission module 47 uses a channel (any one of the channels Ch2 to Ch4) different from the reception channel Ch1 in the reception module 21 from the buffer 39 or the bit determination unit 34. Send the packet. The same applies when any of the reception modules 22 to 24 receives a packet to be combined.

  Note that each of the wireless devices 2 to 9 illustrated in FIG. 1 has the same configuration as the configuration of the wireless device 1 illustrated in FIG. 2.

  FIG. 3 is a configuration diagram of a packet. The packet PKT includes a label and data. The label is an identifier of the packet PKT and is attached by the generation source of the packet PKT. The label includes a flag FG and the packet size of the packet PKT. The flag FG includes EMG indicating that the packet PKT is an urgent packet, or NM indicating that the packet PKT is a normal packet. Data consists of emergency information or normal information.

  FIG. 4 is a configuration diagram of the synthesizer. The combiner 50 includes delay circuits 51 to 53, multipliers 54 to 56, a combine module 57, and a bit determiner 58.

Delay circuits 51 to 53, respectively, receives a signal _y 1 ~y ₃ consisting of bit strings, to delay the received signals _y 1 ~y ₃ only each time Δ (t1) ~Δ (t3) . Then, the delay circuits 51 to 53 output the delayed signals y _{1 to} y ₃ to the multipliers 54 to 56, respectively.

Multipliers 54 to 56 multiply the signals received from delay circuits 51 to 53 by weighting factors CW _{1 to} CW ₃ , respectively, and output the multiplication results to synthesis module 57.

  The synthesis module 57 synthesizes the multiplication results received from the multipliers 54 to 56 by a method described later, and outputs the synthesized signal Z to the bit decision unit 58.

  The bit determination unit 58 performs bit determination on the bit string of the composite signal Z and specifies each bit constituting the bit string.

The weighting coefficient CW _i (i = 1 to 3) is determined by a bit string synthesis method. As a bit string synthesis method, there are MRC (Maximum Ratio Combining), EGC (Equal Gain Combining), and SC (Selective Combining).

MRC is enough signal power to interference power ratio SINR (Signal to Interference Noise Ratio) is high, a synthetic method of weight coefficient CW _i is set larger. EGC is a combining method in which the amount of information held by each of the signals y _{1 to} y ₃ is equal. Furthermore, SC is a combining method for selecting only a signal having the highest signal power to interference power ratio SINR from among the signals y _{1 to} y ₃ to be combined.

If the synthesis is carried out by MRC, weight coefficient CW _i is, if the relatively high signal power to interference power ratio SINR _i of the signal _{y i,} is set to a relatively large value, the signal power to interference power ratio SINR _{If i} becomes relatively low, it is set to a relatively small value. The synthesized signal Z is expressed by the following equation.

When the synthesis is performed by EGC, the weighting coefficient CW _i is set to “1”. The synthesized signal Z is expressed by the following equation.

Furthermore, if the synthesis is carried out by the SC, the weight coefficient CW _i is the signal-to-interference power ratio SINR _i is set to "1" to the highest signal _{y k,} "for other signals _{y i} Set to 0 ”. The synthesized signal Z is expressed by the following equation.

  Therefore, the synthesis module 57 synthesizes the multiplication results received from the multipliers 54 to 56 using any one of the above-described MRC, EGC, and SC methods, and outputs the synthesized signal Z to the bit decision unit 58.

  Each of the wireless devices 1 to 9 includes delay circuits 25 to 28, multipliers 29 to 32, a synthesis module 33, and a bit determination unit 34 (see FIG. 2). To 32, the synthesis module 33 and the bit determination unit 34 are the same as the connection relationships of the delay circuits 51 to 53, the multipliers 54 to 56, the synthesis module 57 and the bit determination unit 58 of the synthesis unit 50 (FIG. 2). And FIG. 4).

  Therefore, each of the wireless devices 1 to 9 includes the combiner 50 shown in FIG. 4, and generates a combined packet by combining a plurality of packets using any of the above-described methods of MRC, EGC, and SC.

  FIG. 5 is a diagram illustrating an example of synthesis using EGC. The wireless device 1 broadcasts a packet PKT1 composed of a bit string [1, -1,1,1, -1] (see (a) in FIG. 5), and the wireless devices 2 to 4 transmit packets that the wireless device 1 broadcasts. PKT1 is received, and the received packet PKT1 is transferred by the cut-through method (see FIG. 5B).

  Then, the wireless device 5 receives the packets transferred by the wireless devices 2 to 4. In this case, the packet PKT2 transferred by the wireless device 2 is composed of the bit string [1, 1, 1, 1, -1], and the packet PKT3 transferred by the wireless device 3 is the bit string [1, -1, 1, 1, −1, −1], and the packet PKT4 transferred by the wireless device 4 includes a bit string [1, −1, 1, 1, 1]. Therefore, the packets PKT <b> 2 to PKT <b> 4 transferred by the wireless devices 2 to 4 each contain an error of 1 bit with respect to the packet PKT <b> 1 broadcast by the wireless device 1.

  The wireless device 5 combines the packets PKT <b> 2 to PKT <b> 4 using EGC (see FIG. 5D), and generates a packet PKT <b> 5 composed of the bit string [1, −1,1,1, −1]. Then, the wireless device 5 transfers the packet PKT5 by the cut-through method (see (c) of FIG. 5). That is, the wireless device 5 combines the three packets PKT2 to PKT4 transferred by the wireless devices 2 to 4 and transfers them by the cut-through method.

  Thus, by combining a plurality of packets using EGC, a packet PKT5 having the same bit string as the packet PKT1 transmitted by the transmission source wireless device 1 can be generated. As a result, reliability in broadcast communication can be improved.

  Similarly, when a plurality of packets are combined using MRC and SC, it is possible to generate a packet having the same bit string as the packet transmitted by the transmission source wireless device.

FIG. 6 is a diagram showing the packet transfer timing by the cut-through method. The wireless device 1 that is the transmission source generates a packet, starts transmitting the generated packet at time t _s ¹ , and ends transmission of the packet at time t _e ¹ .

The wireless device 2 starts to receive the packet transmitted from the wireless device 1 at time r _s ² and ends reception of the packet at time r _e ² . Then, the wireless device 2 starts to transmit at a time t _s ² before the time r _e ² at which reception of the packet from the wireless device 1 is started, and transmits a packet at a time t _e ² after the time r _e ^2. Exit.

The wireless device 3 starts to receive the packet transmitted from the wireless device 2 at time r _s ³ and ends reception of the packet at time r _e ³ . Then, the wireless device 3 transmits a packet in a wireless device than the time r _e ³ packets start receiving from 2 starts sending the previous time t _s ^3, time r _e ³ time t _e ³ later than Exit.

  As a result, the wireless device 1 transmits the packet at the transmission time tx1, the wireless device 2 transfers the packet transmitted from the wireless device 1 at the reception time rx1, and transfers the packet at the time tx2. The wireless device 3 While receiving the packet transmitted from the wireless device 2 at the reception time rx2, the packet is transferred at the time tx3.

Therefore, the transfer delay time in the wireless device 2 is CT1 from time r _s ² to time t _s ^2, and the transfer delay time in the wireless device 3 is CT 2 from time r _s ³ to time t _s ^3. .

  As described above, the transfer of the packet by the cut-through method is started before the reception of the packet is completed. On the other hand, the packet transfer by the normal method is started after the reception of the packet is completed.

  Therefore, the transfer delay time can be shortened by transferring the packet by the cut-through method. That is, the packet can be transferred at high speed by using the cut-through method.

  In this invention, the wireless devices 1 to 9 are mounted on a vehicle and cut through an emergency packet including emergency information indicating that a traffic accident has occurred and a dangerous situation such as sudden braking has occurred. Transfer by method. Thereby, the emergency packet is quickly broadcast to each of the wireless devices 1 to 9, and a traffic accident can be avoided.

  In the following, urgent packet transfer using the cut-through method will be described.

  FIG. 7 is a flowchart for explaining a packet transfer method according to the present invention. FIG. 8 is a diagram for explaining a method of calculating a delay time in the delay circuits 25 to 28 shown in FIG.

  In FIG. 7, the packet transfer method will be described by taking as an example the case where the reception module 21 of the wireless device 1 receives the packet PKT. Further, it is assumed that the switches SW1 to SW4 of the wireless device 1 are initially connected to the terminals TM2, TM4, TM6, and TM8, respectively.

When a series of operations is started, the reception module 21 of the wireless device 1 determines whether or not reception of the packet PKTi is newly started via the antenna 20 (step S1). When the reception module 21 determines that reception of the packet PKTi is newly started, the despreaders 211 to 214 of the reception module 21 reverse the reception signal Rx of the packet PKT with the spreading codes c _{1 to} c ₄ , respectively. Spread spectrum.

In this case, since the packet PKT is spectrum-spread by any _one of the spreading codes c _{1 to} c ₄ , the received signal Rx is one spreading code (for example, spreading code c) among the spreading codes c _{1 to} c _{4. 1} ) Inverse spread spectrum is performed.

Accordingly, the despreader 211 despreads the received signal Rx with the spread code c ₁ and outputs the received signal Rx after the despread spectrum to the bit determiner 215. Note that the despreaders 212 to 214 do not output anything to the bit determiners 216 to 218 because the received signals Rx cannot be reverse spectrum spread by the spread codes c _{2 to} c ₄ , respectively.

  The bit determination unit 215 receives the reception signal Rx from the despreader 211 and performs bit determination on the received reception signal Rx (step S2). The bit determination unit 215 stores the received signal after the bit determination in the buffer 35 via the switch SW1 and the terminal TM2 in symbol (= bit) units or byte units.

  When the received signal starts to be stored in the buffer 35, the label check / scheduling module 40 checks the label L of the packet PKTi (step S3).

  Then, the label check / scheduling module 40 determines whether the packet PKTi is an emergency packet based on the check result of the label L (step S4). More specifically, the label check / scheduling module 40 determines that the packet PKTi is an emergency packet when the label L includes the flag FG including EMG, and the label L includes the flag FG including the flag NM. It is determined that the packet PKTi is not an emergency packet (= normal packet).

  When it is determined in step S4 that the packet PKTi is not an emergency packet, when the MAC module 42 finishes receiving the packet PKTi (step S5), the packet PKTi is checked for errors (step S6). The packet PKTi is transferred to the upper layer (step S7). Thereafter, the series of operations returns to step S1.

  In step S5, the MAC module 42 determines whether or not reception of the packet PKTi is completed by determining whether or not the entire packet PKTi is stored in the buffer 35.

  On the other hand, if it is determined in step S4 that the packet PKTi is an urgent packet, the label check / scheduling module 40 further determines whether or not to wait for combining for the label L (step S8). That is, before receiving the label L of the packet PKTi, the label check / scheduling module 40 receives the packet PKT having the same label L and confirms whether or not the synthesis process is to be started.

In step S8, when it is determined not to be synthesized waiting regard label L, then the label check / scheduling module 40 is configured to initiate synthesis waiting timer passes the timer 41 a waiting time T _CD, label stored in the buffer 35 L is stored in the buffer 39 for the composite packet (step S9). The waiting time T _CD is a difference in arrival times of packets including the same emergency information, and is set in consideration of a difference in radio wave propagation delay.

  After step S9, the label check / scheduling module 40 generates an H level signal SS1, and outputs the generated H level signal SS1 to the switch SW1.

  The switch SW1 switches the connection destination from the terminal TM2 to the terminal TM1 according to the H level signal SS1 from the label check / scheduling module 40. That is, the switch SW1 is switched to the synthesis module 33 side (step S10). As a result, the part following the label L of the packet PKTi is stored in symbol units from the receiving module 21 to the delay circuit 25 on the synthesizing module 33 side.

After step S10, the label check / scheduling module 40 calculates the delay time in the delay circuit 25 to which the signal is input, and sets the calculated delay time in the delay circuit 25 to which the signal is input (step S11). In this case, since the receiving module 21 has received an urgent packet for the first time, the label check / scheduling module 40 calculates the delay time in the delay circuit 25 as the combined waiting time T _CD and uses the calculated delay time T _CD as the delay circuit 25. Set to. Thereafter, the series of operations returns to step S1.

  On the other hand, when it is determined in step S8 that the label L is waiting for composition, the label check / scheduling module 40 switches the switch to the composition module 33 side in the same manner as in step S10 (step S12), and is the same as step S11. By the method, the delay time in the delay circuit to which the signal is input is set (step S13).

  When the series of operations shifts from “YES” in Step S8 to Steps S12 and S13, it is a case where the receiving module 21 receives an emergency packet including the same emergency information from the second time onward. For example, when the label L stored in the buffer 37 includes a flag FG made of EMG, 40 generates an H level signal SS3 and outputs it to the switch SW3, and switches the switch SW3 to the synthesis module 33 side. Then, the delay time of the delay circuit 27 is calculated, and the calculated delay time is set in the delay circuit 27.

In this case, the label check / scheduling module 40 calculates the delay time in the delay circuit 27 by the following method. As shown in FIG. 8, in step S9, the timing at which the composition waiting timer is started is t1, and the timing at which the emergency packet including the same emergency information is received for the second time or later is tj (j = 2, 3,... In the case of ()), the label check / scheduling module 40 calculates DT = T _CD − (tj−t1) to calculate the delay time DTj in the delay circuit 27.

  After step S13, the timer 41 determines whether or not the composition waiting timer has expired (step S14). When it is determined that the composition waiting timer has not expired, the series of operations returns to step S1.

  On the other hand, when it is determined in step S14 that the composition waiting timer has expired, the timer 41 notifies the label check / scheduling module 40 of the end of the composition waiting time (step S15).

  Thereafter, the synthesizer including the delay circuits 25 to 28, the multipliers 29 to 32, the synthesis module 33, and the bit determination unit 34 uses a plurality of packets using any one of the above formulas (1) to (3). And the combined packet is transferred by the cut-through method using the transmission module 47 (step S16).

  When the packet synthesis is completed, the label check / scheduling module 40 generates L-level signals SS1 to SS4 and outputs them to the switches SW1 to SW4, respectively. Accordingly, the switches SW1 to SW4 are connected to the terminals TM2, TM4, TM6, and TM8, respectively. That is, the switch is switched to the buffers 35 to 38 side (step S17).

  Thereafter, the MAC module 42 performs an error check of the packet (= combined packet) stored in the buffer 39 (step S18), and passes the packet after the error check to the upper layer (step S19). Thereby, a series of operation | movement is complete | finished.

  In step S7, after the packet is passed to the upper layer, the upper layer detects that the packet received from the MAC module 42 is a broadcast packet, and transmits the transmission module (any of the transmission modules 43 to 46). ) And the antenna 20. Accordingly, each of the wireless devices 1 to 9 processes a normal packet other than the emergency packet received from the other wireless device according to the flowchart shown in FIG. 7, and transfers the packet by a normal method.

  FIG. 9 is a flowchart for explaining the detailed operation of step S16 shown in FIG. After step S 15 shown in FIG. 7, the label check / scheduling module 40 reads the label L stored in the buffer 39 and outputs it to the transmission module 47. In this case, the label L stored in the buffer 39 is the label L stored in the buffer 39 in step S9. When it is determined that the emergency packet is received for the first time, the label L is stored from any of the buffers 35 to 38 to the buffer 39. The copied label L. Accordingly, after step S15 in FIG. 7, transfer of the copy of the label L stored in the buffer 39 for the composite packet is started (step S161).

  Then, the delay circuits 25 to 28 delay the signal by the delay time set by the label check / scheduling module 40, and output the delayed signals to the multipliers 29 to 32, respectively.

  Multipliers 29 to 32 multiply the signals received from delay circuits 25 to 28 by weighting factors CW 1 to CW 4, respectively, and output the multiplication results to synthesis module 33. The synthesizing module 33 synthesizes the multiplication results received from the multipliers 29 to 32 using any one of the equations (1) to (3) described above. That is, the synthesis module 33 synthesizes a plurality of signals of a plurality of packets (step S162).

  Then, the synthesis module 33 outputs the synthesized signal after synthesis to the bit decision unit 34. The bit decision unit 34 performs bit decision on the synthesis signal from the synthesis module 33, and buffers the bit-determined synthesis signal in symbol units. The data is stored in 39 and output to the transmission module 47.

  Thereafter, the label check / scheduling module 40 selects a channel Cht different from the reception channel Chr (step S163), and outputs the selected channel Cht to the transmission module 47.

  Then, the transmission module 47 transmits the combined signal received in units of symbols from the bit determination unit 34 using the channel Cht received from the label check / scheduling module 40. As a result, the synthesized signal is transferred in symbol units by the cut-through method and stored in the buffer 39 (step S164).

  Thereafter, the series of operations proceeds to step S17 in FIG. As a result, the detailed operation of step S16 shown in FIG. 7 ends.

  FIG. 10 is a view for explaining packet reception processing according to the flowchart shown in FIG. Before the reception module 21 receives a packet, the switches SW1 to SW4 are connected to terminals TM2, TM4, TM6, and TM8, respectively.

  When the series of operations is executed in accordance with “YES” in step S1 → step S2 → step S3 → “YES” in step S4 → “NO” in step S8 → step S9 → step S10 → step S11, the receiving module 21 Starts a new reception of the packet PKT1 (see “YES” in step S1). For example, the despreader 211 succeeds in the despread spectrum of the packet PKT1, and the bit determiner 215 receives the packet from the despreader 211. The bit of the signal is determined (see step S2), and the bit string is stored in the buffer 35 via the switch SW1 (see (a) of FIG. 10).

  The label check / scheduling module 40 checks the label L stored in the buffer 35 (see step S3) and determines that the packet PKT1 is an urgent packet (see “YES” in step S4).

  After that, the label check / scheduling module 40 receives the urgent packet for the first time, and therefore determines that the label L is not waiting for composition (see “NO” in step S8), starts a composition waiting timer, and uses the label L for composition. The data is stored in the buffer 39 (see step S9).

  Then, the label check / scheduling module 40 generates an H-level signal SS1 and outputs it to the switch SW1, and switches the connection destination of the switch SW1 from the terminal TM2 to the terminal TM1 (see step S10). As a result, the portion following the label L of the packet PKT1 is input from the bit determiner 215 to the delay circuit 25 via the switch SW1 (see FIG. 10B).

  Then, the label check / scheduling module 40 calculates the delay time in the delay circuit 25 by the method described above, and sets the calculated delay time in the delay circuit 25 (see step S11).

  Thereafter, the receiving module 21 newly starts receiving the packet PKT2 (see “YES” in step S1), the despreader 212 succeeds in the despread spectrum of the packet PKT2, and the bit determiner 216 receives the despreader. The bit from the signal from 212 is determined (see step S2), and the bit string is stored in the buffer 36 via the switch SW2 (see (b) of FIG. 10).

  The label check / scheduling module 40 checks the label L stored in the buffer 36 (see step S3) and determines that the packet PKT2 is not an emergency packet (see “NO” in step S4). Thereafter, steps S5 to S7 described above are sequentially executed. Therefore, in this case, the switch SW2 remains connected to the terminal TM4 and normal packet reception processing is performed.

  Thereafter, the reception module 21 newly starts receiving the packet PKT3 (see “YES” in step S1), the despreader 213 succeeds in the despread spectrum of the packet PKT3, and the bit determiner 217 receives the despreader. The bit from the signal from 213 is determined (see step S2), and the bit string is stored in the buffer 37 via the switch SW3 (see (b) of FIG. 10).

  The label check / scheduling module 40 checks the label L stored in the buffer 37 (see step S3) and determines that the packet PKT3 is an urgent packet (see “YES” in step S4).

  After that, the label check / scheduling module 40 receives the urgent packet for the second time, and therefore determines that the label L is waiting for composition (see “YES” in step S8).

  Then, the label check / scheduling module 40 generates an H level signal SS3 and outputs it to the switch SW3, and switches the connection destination of the switch SW3 from the terminal TM6 to the terminal TM5 (see step S12). As a result, the portion following the label L of the packet PKT3 is input from the bit determiner 217 to the delay circuit 27 via the switch SW3 (see (c) of FIG. 10).

  Then, the label check / scheduling module 40 calculates the delay time in the delay circuit 27 by the method described above, and sets the calculated delay time in the delay circuit 27 (see step S13).

  Thereafter, the label check / scheduling module 40 determines that the composition waiting timer has not expired (see “NO” in step S14).

  Subsequently, the despreader 214 and the bit determiner 218 of the reception module 21 newly receive the packet PKT4 which is an urgent packet, and “YES” in step S1 → step S2 → step S3 → “YES” in step S4. → "YES" in step S8 → step S12 → step S13, the part following the label L of the packet PKT4 is input to the delay circuit 28 via the switch SW4, and the delay time in the delay circuit 28 is set (FIG. 10). (See (c)).

  Then, the timer 41 determines that the combination waiting timer has expired (see “YES” in step S14), and the combination module 33 combines the packets PKT1, PKT3, PKT4, the label check / scheduling module 40, and the transmission module 47. Transfers the combined packet by the cut-through method (see steps S15 and S16).

  When the packet reception process is executed according to the flowchart shown in FIG. 7, when only one emergency packet is received before the combining waiting timer expires, the combining module 33 selects one of the multipliers 29 to 32. Since the multiplication result is received from only one, the received multiplication result is output to the bit decision unit 34 as the synthesized signal Z.

  Therefore, even when only one emergency packet is received before the combination waiting timer expires, the packet reception process can be executed according to the flowchart shown in FIG.

  As described above, the emergency packet broadcast by executing the packet reception process according to the flowchart shown in FIG. 7 is combined and transferred, so that the reliability in broadcast communication can be improved.

  Moreover, since the emergency packet is transferred by the cut-through method, the packet can be transferred at high speed.

  Furthermore, since the emergency packet including the emergency information is transferred by the cut-through method, the emergency information can be transferred at high speed.

  Furthermore, since it is determined whether or not to synthesize a packet based on a label (= identification information) added to the head of the packet, it is possible to quickly determine whether or not to synthesize a packet. As a result, the synthesized packet can be transferred at high speed.

  FIG. 11 is a conceptual diagram according to Embodiment 1 when an emergency packet is synthesized and transferred by the cut-through method. 11 includes switches SW1 to SW4, delay circuits 25 to 28, multipliers 29 to 32, a synthesis module 33, and a bit determination unit 34.

  The receiving module 21 sequentially receives the packets PKT1, PKT3, and PKT4. When each of the packets PKT1, PKT3, and PKT4 is determined to be a packet to be combined, each of the received signals of the packets PKT1, PKT3, and PKT4 is bit-determined. The bit string [1,1,1,1, -1], [1, -1,1, -1, -1], [1, -1,1,1,1] are sequentially output to the combiner 50. To do.

  When the transmission module 47 starts to transfer the label L, the synthesizer 50 receives the bit string [1, 1, 1, 1, −1], [1, −1, 1, −1, -1], [1, -1,1,1,1] to generate a bit string [1, -1,1,1, -1], and the generated bit string [1, -1,1,1] 1, -1] is output to the transmission module 47, and the transmission module 47 transmits the bit string [1, -1, 1, 1, -1].

  As a result, a combined packet obtained by combining the packets PKT1, PKT3, and PKT4 is transferred by the cut-through method.

  As described above, the transfer of the emergency packet according to the present invention is executed by the physical layer and the MAC layer, so that the emergency packet can be transferred at high speed.

  In FIG. 11, after the reception of the packets PKT, PKT3, and PKT4 by the receiving module 21 is completed, the combiner 50 performs the bit string [1, 1, 1, 1, −1], [1, −1, 1, -1, -1], [1, -1, 1, 1, 1] are illustrated as starting, but in practice, the synthesizer 50 does not combine a plurality of packets PKT, PKT3, PKT4. Before completion of reception, the bit string [1, 1, 1, 1, -1], [1, -1, 1, -1, -1], [1, -1, 1, 1, 1] is synthesized. Start.

  FIG. 12 is a diagram showing a specific example of packet transfer in the wireless network 100 shown in FIG. The wireless devices 1 to 9 are mounted on the vehicles C1 to C9, respectively. The vehicles C1 to C3, C5, C7, and C8 are traveling in the same direction, and the vehicles C4, C6, and C9 are traveling in the same direction in the direction opposite to the traveling direction of the vehicles C1 to C3, C5, C7, and C8. Running.

  In this situation, when the vehicle C1 suddenly brakes, the wireless device 1 mounted on the vehicle C1 generates and broadcasts an emergency packet PKT1 including emergency information indicating that the vehicle C1 has suddenly braked. .

  Then, the wireless devices 2 to 4 respectively mounted on the vehicles C2 to C4 receive the emergency packet PKT1 from the wireless device 1, refer to the label L of the received emergency packet PKT1, and the emergency packet PKT1 is the emergency information. Detect that the packet contains Then, the wireless devices 2 to 4 transfer the emergency packet PKT1 as the emergency packets PKT2 to PKT4 by the cut-through method, respectively.

  The wireless device 5 mounted on the vehicle C5 receives the emergency packets PKT2 to PKT4 transmitted from the wireless devices 2 to 4, respectively, and refers to the label L of the received emergency packets PKT2 to PKT4, It is detected that PKT2 to PKT4 are packets to be combined, and the emergency packets PKT2 to PKT4 are combined and transferred by the cut-through method by the method described above.

  When receiving a plurality of emergency packets, the wireless devices 6 to 9 mounted in the vehicles C6 to C9 also synthesize the plurality of emergency packets and transfer them by the cut-through method, similarly to the wireless device 5.

  As a result, the emergency packet PKT1 generated and broadcast by the wireless device 1 is transferred at high speed by the cut-through method after the second hop.

  Therefore, the wireless devices 3, 5, 7, and 8 mounted on the vehicles C3, C5, C7, and C8, which are the vehicles following the vehicle C1, can quickly detect that the vehicle C1 is suddenly braked, and the rear-end collision can be detected. Can be prevented.

  Further, when an emergency packet is transferred by the cut-through method, a plurality of emergency packets are combined and transferred, so that the information generated by the wireless device 1 that is the generation source can be accurately transmitted to the wireless devices 7 and 8. . Therefore, reliability in broadcast communication can be improved.

  In the above description, a case has been described in which each of the wireless devices 1 to 9 combines a plurality of emergency packets received on the same channel and transfers them by the cut-through method. However, the present invention is not limited to this, and each wireless device In accordance with the flowcharts shown in FIGS. 7 and 9, the devices 1 to 9 synthesize a plurality of emergency packets received on different channels and transfer them by the cut-through method. For example, each of the wireless devices 1 to 9 includes the emergency packet PKT1 received by the receiving module 21 on the channel Ch1, the emergency packet PKT2 received by the receiving module 22 on the channel Ch2, and the emergency packet PKT3 received by the receiving module 24 on the channel Ch4. Are combined and transferred by the cut-through method. In this case, the transmission module 47 transmits the composite packet using a channel Ch3 other than the reception channels Ch1, Ch2, and Ch4 in the reception modules 21, 22, and 24.

  When the receiving modules 21 to 24 combine the emergency packets PKT1, PKT2, PKT3, and PKT4 received on the channels Ch1, Ch2, Ch3, and Ch4, respectively, and transfer them by the cut-through method, the transmitting module 47 includes the receiving modules 21 to 21. 24, the composite packet is transmitted using the reception channel of the reception module (any one of the reception modules 21 to 24) that has started receiving the emergency packet earliest.

  The receiving module that started receiving the urgent packet earliest completes the receiving of the urgent packet earliest. Therefore, when the synthesized packet is started to be transferred by the cut-through method, the receiving module that started receiving the urgent packet earliest This is because it is highly possible that the reception of the packet has been completed, and the channel used for receiving the urgent packet by the receiving module that started receiving the urgent packet earliest can be used for transmitting the composite packet.

  In addition, the transmission module may use a channel having the smallest signal power to interference power ratio SINR for transmission of the combined packet.

  Further, when the reception modules 21 to 24 combine the emergency packets PKT1, PKT2, PKT3, and PKT4 received on the channels Ch1, Ch2, Ch3, and Ch4, respectively, and transfer them by the cut-through method, the transmission module 47 includes the reception modules 21 to 21. 24, except for the emergency packet (emergency packet PKT1, PKT2, PKT3, PKT4) received by the reception module (any one of the reception modules 21 to 24) that started receiving the emergency packet latest Are combined, and the combined packet is transmitted using the reception channel of the receiving module that started reception of the urgent packet most recently. This increases the possibility of avoiding the self-interference problem described later.

  Note that the label check / scheduling module 40 starts receiving any of the packets earlier or later, based on the time when the labels L of the packets PKT1 to PKT4 are stored in the buffers 35 to 38. It is determined. Further, since the label checking / scheduling module 40 knows the channel used by the receiving modules 21 to 24 for receiving the packet, the label checking / scheduling module 40 can easily determine the channel used for transmitting the combined packet.

  FIG. 13 is a diagram showing the relationship between the average signal noise ratio per channel and the number of channels. In FIG. 13, the vertical axis represents the average signal-to-noise ratio per channel, and the horizontal axis represents the number of channels. The average signal-to-noise ratio per channel indicates the improvement in SNR (Signal to Noise Ratio) relative to the case where packets are not combined in decibels. The number of channels means the number of packets to be combined. Furthermore, curves k1 to k3 respectively show the relationship between the average signal noise ratio per channel and the number of channels when packets are combined using the above-described equations (1) to (3).

  From the result shown in FIG. 13, when the number of packets to be combined is the same, the performance of packet combining increases in the order of SC, EGC, and MRC. When the combining method is the same, the packet combining performance improves as the number of packets to be combined increases.

  Therefore, the performance of packet synthesis is improved when many packets are synthesized.

  FIG. 14 is a diagram for explaining the self-interference and the perspective problem. FIG. 15 is a timing chart of packet transmission / reception when self-interference occurs. Self-interference is a problem that when a packet is transmitted using a packet reception channel, the packet reception process is not performed correctly due to the high interference caused by the packet transmission.

  For example, as illustrated in FIG. 14, a case is assumed in which the wireless device 4 receives packets including the same information from the wireless devices 1 to 3. The wireless device 1 transmits a packet on the channel Ch1, and the wireless devices 2 and 3 transmit a packet on the channel Ch2. In this case, if the wireless device 4 combines the three packets received from the wireless devices 1 to 3 and transfers the combined packet using the channel Ch1, the packet from the wireless device 1 cannot be correctly received due to self-interference. This is a problem of self-interference.

  This self-interference is because, as can be seen from FIG. 15, the reception of the packet and the transmission of the packet in the wireless device 4 overlap in time. Therefore, the wireless device 4 cannot set the packet received from the wireless device 1 as an object of packet synthesis. As a result, the packet combining performance is degraded.

  On the other hand, in FIG. 14, the distance from the wireless device 2 to the wireless device 4 and the distance from the wireless device 3 to the wireless device 4 are relatively different, and the wireless device 4 correctly receives the packet transmitted from the wireless device 2. A perspective problem that cannot be done may occur. When the perspective problem occurs, the wireless device 4 cannot set the packet received from the wireless device 2 as a packet synthesis target. As a result, the packet combining performance is degraded.

  FIG. 16 is a diagram illustrating a perspective problem that occurs when the packet size is large. FIG. 17 is a timing chart of packet transmission / reception when a perspective problem occurs due to a large packet size.

  The wireless device 2 transfers the packet transmitted from the wireless device 1 using the channel Ch1 to the channel Ch2 by the cut-through method, and the wireless device 3 transfers the packet transmitted from the wireless device 2 to the channel Ch1 by the cut-through method. Suppose that it was transferred. Further, it is assumed that the distance from the wireless device 3 to the wireless device 2 is much shorter than the distance from the wireless device 1 to the wireless device 2.

  As a result, as shown in FIG. 17, the wireless device 3 starts transmitting a packet before the wireless device 1 finishes transmitting the packet. Accordingly, the wireless device 2 cannot correctly receive the packet from the wireless device 1, and a perspective problem occurs. Then, the wireless device 2 cannot use the packet from the wireless device 1 as a packet synthesis target.

  In this case, not only packet combining performance is degraded, but multi-hop packet transfer may fail.

  A packet having a large packet size means a packet having a size equal to or larger than a reference size, and the reference size is a transfer by a cut-through method in the wireless device 2 whose transmission time tx in the wireless device 1 on the transmission side is a transfer terminal. The packet size is approximately equal to the delay time CT.

  Therefore, a method for solving the self-interference and perspective problems described in FIGS. 14 to 17 will be described below.

  When the transmission delay time by the cut-through method in each wireless device 1-9 is CT and the packet transmission time in the transmitting wireless device is Tx, the label check / scheduling module 40 of each wireless device 1-9 is An integer N satisfying the following equation is calculated.

  The label check / scheduling module 40 of each of the wireless devices 1 to 9 can calculate the transfer delay time CT by the cut-through method in the wireless devices 1 to 9 on which the wireless devices 1 to 9 are mounted. Further, since the label check / scheduling module 40 of each of the wireless devices 1 to 9 knows the transmission rate of each of the wireless devices 1 to 9, if the packet size stored in the label L of the packet is seen, the wireless on the transmission side The transmission time Tx in the apparatus can be obtained. Accordingly, the label check / scheduling module 40 of each of the wireless devices 1 to 9 can calculate an integer N that satisfies Equation (4).

  In each wireless device 1-9, the label check / scheduling module 40 calculates an integer N and divides all channels used in the wireless network 100 into N groups.

  For example, when N = 2, the label check / scheduling module 40 of each of the wireless devices 1 to 9 divides the four channels Ch1 to Ch4 into two groups G1 and G2. In this case, the group G1 includes, for example, channels Ch1 and Ch2, and the group G2 includes, for example, channels Ch3 and Ch4.

  FIG. 18 is a diagram for explaining a channel selection method for solving the self-interference and perspective problems. The wireless device 1 is a transmission terminal at the first hop when transmitting a packet, the wireless devices 2 to 4 are transmission terminals at the second hop, and the wireless devices 5 and 6 are transmission terminals at the third hop. Yes, the wireless devices 7 to 9 are transmission terminals of the fourth hop.

  The wireless device 1 transmits a packet using the channel Ch1 included in the group 1, and the wireless devices 2 to 4 transfer the packets received from the wireless device 1 using the channels Ch3 and Ch4 included in the group 2 by the cut-through method. To do. Further, the wireless devices 5 and 6 transfer the packets received from the wireless devices 2 to 4 using the channels Ch1 and Ch2 included in the group 1 by the cut-through method, and the wireless devices 7 to 9 transmit the wireless devices 5 and 6 to each other. Are transferred using the channels Ch3 and Ch4 included in the group 2 by the cut-through method. In this way, the same channel can be reused every N hops.

  As a result, the wireless devices 2 to 4 transfer the packet by the cut-through method using the channels Ch3 and Ch4 different from the channel Ch1 used by the wireless device 1 for packet transmission, and therefore, between the first hop and the second hop. The problem of self-interference does not occur. Similarly, the problem of self-interference does not occur between the second hop and the third hop and between the third hop and the fourth hop.

  Therefore, in the present invention, in order to solve the problem of self-interference, two or more different channels are employed in the wireless network 100, and the two or more channels may be divided into two or more channel groups. That's fine. In this case, one channel group includes one or more channels.

  Further, when each channel group includes two or more channels, the perspective problem can be suppressed. For example, in FIG. 18, when the wireless device 3 transmits a packet using the channel Ch3 and the wireless device 4 transmits a packet using the channel Ch4, the wireless device 5 is transmitted from both the wireless device 3 and the wireless device 4. Packets can be received normally.

  As a result, the wireless device 5 can set the packet from the wireless device 3 and the packet from the wireless device 4 to be subject to packet composition, and can improve the performance of packet composition.

  Therefore, in the present invention, in order to suppress the perspective problem, four or more channels different from each other are adopted in the wireless network 100, and the four or more channels may be divided into two or more channel groups. That's fine. In this case, one channel group includes two or more channels.

  Furthermore, when there are three or more channel groups and each channel group includes one or more channels, the perspective problem when the packet size is large can be solved. For example, in FIG. 18, wireless devices 2 to 4 transmit packets using channel Ch1 included in channel group 1, wireless devices 5 and 6 transmit packets using channel Ch2 included in channel group 2, If the wireless devices 7 to 9 transmit a packet using the channel Ch3 included in the channel group 3, even if the wireless device 5 receives a packet with a large packet size from the wireless devices 2 to 4, the wireless device 5 Packets can be received normally. As a result, the perspective problem when the packet size is large can be solved.

  Therefore, in the present invention, in order to solve the perspective problem when the packet size is large, three or more channels are adopted in the wireless network 100, and the three or more channels are divided into three or more channel groups. It only has to be done. In this case, each channel group includes one or more channels.

  As described above, by dividing a channel into a plurality of channel groups so that the same channel can be reused every N hops, the above-described self-interference and perspective problems can be solved or suppressed.

  In the above description, the four channels Ch1 to Ch4 are sequentially divided into the channels Ch1 and Ch2 into the group 1, and the channels Ch3 and Ch4 are divided into the group 2. However, the present invention is not limited to this. These channels may be divided into a plurality of groups by an arbitrary method. In this case, the number of channels included in each group may be the same or different.

  FIG. 19 is a flowchart for explaining another detailed operation of step S16 shown in FIG. The flowchart shown in FIG. 19 is the same as the flowchart shown in FIG. 9 except that step S163 in the flowchart shown in FIG. 9 is replaced with step S163A.

  After the above-described steps S161 and S162, the label check / scheduling module 40 determines a group (= G2 or G1) different from the group (= G1 or G2) including the reception channel Chr (= Ch1, Ch2 or Ch3, Ch4). The channel Cht (= Ch3, Ch4 or Ch1, Ch2) included in is selected (step S163A).

  Thereafter, step S164 described above is executed, and the series of operations proceeds to step S17 shown in FIG.

  By executing the detailed operation of step S16 shown in FIG. 7 according to the flowchart shown in FIG. 19, the above-described self-interference and perspective problems can be avoided. As a result, the number of packet synthesis targets is increased, and the performance of packet synthesis is improved. Therefore, reliability in broadcast communication can be improved.

[Embodiment 2]
FIG. 20 is a schematic block diagram showing the configuration of the wireless devices 1 to 9 shown in FIG. 1 in the second embodiment. In the second embodiment, wireless devices 1 to 9 include wireless device 1A shown in FIG.

  The wireless device 1A deletes the delay circuits 25 to 28, the multipliers 29 to 32, the synthesis module 33, and the bit determination unit 34 of the wireless device 1 shown in FIG. 2, and replaces the reception modules 21 to 24 with the reception modules 21A to 24A. The transmission modules 43 to 47 are replaced with the transmission module 48, and the others are the same as those of the wireless device 1. The reception modules 21A to 24A and the transmission module 48 are arranged in the physical layer.

  The receiving modules 21A to 24A receive the packets using the channels Ch1 to Ch4, respectively. Then, the receiving modules 21A to 24A store the received packet in the buffers 35 to 38 when the received packet is a normal packet. If the received packet is an emergency packet, the receiving modules 21A to 24A store the label L of the packet in the buffers 35 to 35. 38, and the part following the label L is synthesized and output to the transmission module 48.

  The transmission module 48 transmits the emergency packet label from the buffer 39 and the emergency packet from the reception modules 21A to 24A on a channel different from the reception channel in the reception modules 21A to 24A.

  The reception module 21A includes despreaders 211 to 214, switches SW1 to SW4, delay circuits 221 to 224, multipliers 225 to 228, a synthesis module 229, and bit determination units 230 to 234.

  The despreaders 211 to 214 and the switches SW1 to SW4 are as described above. In the second embodiment, the switches SW1 to SW4 are connected to the despreaders 211 to 214, respectively.

  Delay circuits 221 to 224 are connected to terminals TM1, TM3, TM5, and TM7, respectively. Multipliers 225 to 228 are connected to delay circuits 221 to 224, respectively. The synthesis module 229 is connected to the multipliers 225 to 228. The bit determiner 230 is connected to the synthesis module 229, and the bit determiners 231 to 234 are connected to terminals TM2, TM4, TM6, and TM8, respectively.

  Delay circuit 221 delays the signal received via terminal TM 1 by delay time Δ (t 1) set by label check / scheduling module 40, and outputs the delayed signal to multiplier 225.

  Delay circuit 222 delays the signal received via terminal TM 3 by delay time Δ (t 2) set by label check / scheduling module 40, and outputs the delayed signal to multiplier 226.

  Delay circuit 223 delays the signal received via terminal TM5 by delay time Δ (t3) set by label check / scheduling module 40, and outputs the delayed signal to multiplier 227.

  Delay circuit 224 delays the signal received via terminal TM 7 by delay time Δ (t 4) set by label check / scheduling module 40, and outputs the delayed signal to multiplier 228.

Multipliers 225 to 228 multiply the signals received from delay circuits 221 to 224 by weighting factors CW _{1 to} CW ₄ , respectively, and output the multiplication results to synthesis module 229. The combining module 229 combines the multiplication results received from the multipliers 225 to 228 using any one of the above-described expressions (1) to (3), and outputs the combined result to the bit determination unit 230.

  The bit determination unit 230 receives the combined signal from the combining module 229 and performs bit determination on the received combined signal. Then, the bit determination unit 230 outputs the signal after the bit determination to the transmission module 48.

  Bit determiners 231 to 234 receive the signals subjected to inverse spectrum spread by despreaders 211 to 214 via switches SW1 to SW4, respectively, and perform bit determination on the received signals. Then, the bit determiners 231 to 234 output the signals after the bit determination to the buffers 35 to 38, respectively.

  Each of the receiving modules 22A to 24A has the same configuration as the receiving module 21A.

  Thus, in the second embodiment, packet synthesis is performed in the physical layer, and bit determination is performed after packet synthesis.

  When the wireless devices 1 to 9 include the wireless device 1A shown in FIG. 20, the packet reception processing in each of the wireless devices 1 to 9 is executed according to the flowcharts shown in FIGS. Is done.

  FIG. 21 is a conceptual diagram in Embodiment 2 when an emergency packet is synthesized and transferred by a cut-through method. 21 includes switches SW1 to SW4, delay circuits 221 to 224, multipliers 225 to 228, a synthesis module 229, and a bit determination unit 230.

  The operation of combining the emergency packets PKT1, PKT3, and PKT4 and transferring them by the cut-through method is the same as that described in FIG. In this case, in the description of FIG. 11, the receiving module 21, the transmitting module 47, and the combiner 50 may be read as the receiving module 21A, the transmitting module 48, and the combiner 50A, respectively.

  As shown in FIG. 21, in the second embodiment, the operation of combining the emergency packets PKT1, PKT3, and PKT4 and transferring them by the cut-through method is executed in the physical layer. Emergency packets can be transferred faster than transfer.

  In addition, since the wireless device 1A illustrated in FIG. 20 performs packet combining before bit determination, the performance of packet combining can be improved as compared with the case where the wireless devices 1 to 9 have the configuration illustrated in FIG. In addition, in the second embodiment, the same effects as in the first embodiment can be obtained.

  On the other hand, when the wireless devices 1 to 9 have the configuration shown in FIG. 2, the wireless devices 1 to 9 have a feature that they are easier to implement than when the wireless devices 1 to 9 have the configuration shown in FIG. 20.

  Others are the same as in the first embodiment.

[Embodiment 3]
In the first and second embodiments described above, it has been described that the packets are combined when the packets are transferred by the cut-through method. However, in this third embodiment, the packet is not a cut-through method but a normal method. Packets are combined when transferred by.

  FIG. 22 is a schematic block diagram showing a configuration in the third embodiment of wireless devices 1 to 9 shown in FIG. When the packet is not transferred by the cut-through method, the wireless devices 1 to 9 include the wireless device 1B illustrated in FIG.

  The wireless device 1B includes switches SW1 to SW4, delay circuits 25 to 28, multipliers 29 to 32, a synthesis module 33, a bit determination unit 34, buffers 35 to 39, and a label check / scheduling module 40 of the wireless device 1 illustrated in FIG. The timer 41, the MAC module 42, and the transmission modules 43 to 47 are replaced with buffers 61 to 64, a MAC module 65, a timer 66, multipliers 67 to 70, a synthesis module 71, a bit determination unit 72, and a transmission module 73. The others are the same as those of the wireless device 1 shown in FIG.

  The buffers 61 to 64, the MAC module 65, the timer 66, the multipliers 67 to 70, the synthesis module 71, and the bit determination unit 72 are arranged in the MAC layer, and the transmission module 73 is arranged in the physical layer.

  Buffers 61 to 64 hold packets PKT received from bit determiners 215 to 218, respectively.

  The MAC module 65 performs an error check on the packets PKT held in the buffers 61 to 64 in the order in which the packets PKT are stored, and determines whether or not the packets PKT contain errors.

  Then, when the packet PKT does not include an error, the MAC module 65 passes the packet PKT to the upper layer.

  On the other hand, when the packet PKT includes an error, the MAC module 65 holds the packet PKT. Then, the MAC module 65 measures a certain time by the timer 66 from the time when the packet PKT is first held.

  Thereafter, when the MAC module 65 receives a packet including the same information as the packet PKT held first before a predetermined time elapses, the MAC module 65 holds the received packet. The MAC module 65 repeats this operation until a predetermined time elapses. When a predetermined time passes, a plurality of packets held until the predetermined time passes are output to multipliers (the same number of multipliers as the number of packets among the multipliers 67 to 70).

  On the other hand, if the MAC module 65 does not receive a packet including the same information as the initially held packet PKT by the time a fixed time elapses, the MAC module 65 discards the initially held packet PKT.

  Further, the MAC module 65 performs an error check on the combined packet received from the bit determination unit 72. If the combined packet does not include an error, the MAC module 65 passes the combined packet to an upper layer. If the combined packet includes an error, the MAC packet 65 Hold it as the target of packet synthesis.

  The timer 66 measures a predetermined time according to an instruction from the MAC module 65, and notifies the MAC module 65 that the predetermined time has ended when the predetermined time ends.

Multipliers 67 to 70 multiply the packets PKT received from the MAC module 65 by weight coefficients CW _{1 to} CW ₄ , respectively, and output the multiplication results to the synthesis module 71. The synthesizing module 71 synthesizes the multiplication results from the multipliers 67 to 70 using any one of the above formulas (1) to (3), and outputs the synthesized signal Z to the bit decision unit 72.

  The bit determination unit 72 determines the bit of the combined signal Z received from the combining module 71 and outputs the combined signal Z after the bit determination to the MAC module 65.

  The transmission module 73 transmits the packet received from the upper layer via the antenna 20.

  FIG. 23 is a flowchart for explaining another method of transferring a packet according to the present invention. In the following, a case where the reception module 21 receives a packet will be described.

  When a series of operations is started, the reception modules 21 of the wireless devices 1 to 9 receive new packets. For example, the despreader 211 despreads the received packet and outputs the despread spectrum packet to the bit determiner 215.

  Bit determiner 215 determines the bit of the packet received from despreader 211 and stores the packet after the bit determination in buffer 61. Thereby, reception of a new packet is completed (step S21).

  Thereafter, the MAC module 65 performs an error check on the packet stored in the buffer 61 (step S22), and determines whether there is an error (step S23).

  If the MAC module 65 determines in step S23 that there is no error, it passes the packet to the upper layer (step S24).

  On the other hand, if it is determined in step S23 that there is an error, the MAC module 65 holds the packet (step S25) and measures a certain time by the timer 66.

  Thereafter, the MAC module 65 determines whether or not a certain time has elapsed (step S26). And when it determines with fixed time not having passed in step S26, a series of operation | movement returns to step S1.

  On the other hand, if it is determined in step S26 that the predetermined time has elapsed, the MAC module 65 further determines whether there is a packet to be combined (step S27). More specifically, the MAC module 65 determines whether or not there is a packet to be combined by determining whether or not a plurality of packets having the same information and having an error are held. In this case, if the MAC module 65 holds a plurality of packets that contain the same information and have an error, the MAC module 65 determines that there is a packet to be combined.

  If the MAC module 65 determines in step S27 that there is a packet to be combined, the MAC module 65 outputs the held packets to multipliers (for example, multipliers 67 to 69).

Multipliers 67 to 69 multiply the packets received from MAC module 65 by weight coefficients CW _{1 to} CW ₃ , respectively, and output the multiplication results to combining module 71. The synthesis module 71 receives the three multiplication results from the multipliers 67 to 69, synthesizes the received three multiplication results using any of the above-described equations (1) to (3), and generates a synthesized signal. Z is output to the bit decision unit 72. As a result, the packets are combined (step S28). Thereafter, the series of operations returns to step S22.

  On the other hand, if it is determined in step S27 that there is no packet to be combined, the MAC module 65 discards the held packet (step S29).

  And a series of operation | movement is complete | finished after step S24 or step S29.

  In step S24, after the packet is passed to the upper layer, the upper layer detects that the packet received from the MAC module 65 is a broadcast packet and transmits the packet via the transmission module 73 and the antenna 20. . Accordingly, each of the wireless devices 1 to 9 processes the packet received from the other wireless device according to the flowchart shown in FIG. 23, and transfers the packet by a normal method.

  As described above, when a packet contains an error, information can be accurately transferred by combining and transferring the packet. As a result, reliability in broadcast communication can be improved.

  Others are the same as in the first embodiment.

  As described above, the transmission modules 47 and 48 transfer the synthesized packet by a cut-through method using a channel different from the channel used by the reception modules 21 to 24 and 21A to 24A for receiving the packet. Depending on the reason.

  FIG. 24 is a diagram showing a cut-through method using the same channel. A case is assumed in which the wireless device 2 mounted on the vehicle B transfers a packet received from the wireless device 1 mounted on the vehicle A immediately before to the same channel as the reception channel by the cut-through method.

When the transmission power of each of the wireless devices 1 and 2 is Tx, the reception power R _xs of the packet that the wireless device 2 receives from the wireless device 1 is expressed by the following equation.

In the equation (5), G _AB is a path loss and is expressed by the following equation.

In Expression (6), L _IV is a vehicle-to-vehicle distance (strictly speaking, a distance between the antenna 20 of the wireless device 1 and the antenna 20 of the wireless device 2). Moreover, in Formula (6), (alpha) is a constant and consists of a value between 2-5.

Since the wireless device 2 uses the cut-through method to transfer a packet using the same channel while receiving the packet, the interference power R _xI due to the transfer packet is expressed by the following equation.

In Expression (7), G _AS is a path loss and is represented by the following expression.

In equation (8), L _AS is the distance between the transmitting and receiving antennas of the wireless device 2. In this case, the antenna 20 of the wireless device 2 is composed of a transmitting antenna 20A and the receiving antennas 20B, closest to the transmitting antenna 20A and the receiving antennas 20B _is set to _{L AS.}

  In order for the wireless device 2 to correctly receive the packet from the wireless device 1, the following equation needs to be satisfied.

Here, if the distance between the transmitting and receiving antennas 20A and 20B of the vehicle B is 5 m, the spreading gain is 31, the threshold SINR of signal to interference plus noise is 5 dB, and α is 2, the condition of L _IV <12.5 m Is obtained. This condition is shorter than the braking distance of a vehicle traveling at a speed of 40 km / h and is not realistic.

  Therefore, in the present invention, the packet transfer by the cut-through method to the same channel is not adopted, but the packet transfer by the cut-through method to different channels is adopted.

  In the above description, the number of reception modules is four. However, the present invention is not limited to this, and the number of reception modules may be any number.

  In the present invention, the despreaders 211 to 214 constitute “receiving means”.

  In the present invention, the bit determination units 215 to 218, the delay circuits 25 to 28, the multipliers 29 to 32, the synthesis module 33, the bit determination unit 34, the label check / scheduling module 40, and the transmission module 47 are “transfer means”. Is configured.

  Further, in the present invention, the label check / scheduling module 40 constitutes “determination means”.

  Further, in the present invention, the bit determiners 215 to 218 constitute “a plurality of first bit determination means”, the delay circuits 25 to 28, the multipliers 29 to 32 and the synthesis module 33 constitute “synthesis means”. The bit decision unit 34 constitutes “second bit decision unit”, and the transmission module 47 constitutes “transmission unit”.

  Further, in the present invention, the delay circuits 221 to 224, the multipliers 225 to 228, the synthesis module 229, the bit determination unit 230, and the transmission module 48 constitute “transfer means”.

  Further, in the present invention, the delay circuits 221 to 224, the multipliers 225 to 228, and the synthesis module 229 constitute “synthesis unit”, the bit decision unit 230 constitutes “bit decision unit”, and the transmission module 48. Constitutes "transmission means".

  Further, in the present invention, the bit determination units 215 to 218, the buffers 61 to 64, the MAC module 65, the multipliers 67 to 70, the synthesis module 71, the bit determination unit 72, and the transmission module 73 constitute "transfer means". .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a radio apparatus capable of improving reliability in broadcast communication. The present invention is also applied to a wireless network including a wireless device capable of improving reliability in broadcast communication.

1 is a schematic diagram of a wireless network according to an embodiment of the present invention. FIG. 2 is a schematic block diagram illustrating a configuration of the wireless device illustrated in FIG. 1 in the first embodiment. It is a block diagram of a packet. It is a block diagram of a combiner | synthesizer. It is a figure which shows the example of the synthesis | combination using EGC. It is a figure which shows the timing of the packet transfer by a cut-through system. 3 is a flowchart for explaining a packet transfer method according to the present invention; FIG. 3 is a diagram for explaining a method of calculating a delay time in the delay circuit shown in FIG. 2. It is a flowchart for demonstrating the detailed operation | movement of step S16 shown in FIG. It is a figure for demonstrating the reception process of the packet according to the flowchart shown in FIG. FIG. 3 is a conceptual diagram in Embodiment 1 when urgent packets are combined and transferred by a cut-through method. It is a figure which shows the specific example of the packet transfer in the radio | wireless network shown in FIG. It is a figure which shows the relationship between the average signal noise ratio per channel, and the number of channels. It is a figure for demonstrating a self-interference and a perspective problem. 6 is a timing chart of packet transmission / reception when self-interference occurs. It is a figure which shows the perspective problem which arises when a packet size is large. It is a timing chart of packet transmission / reception when a perspective problem due to a large packet size occurs. It is a figure for demonstrating the channel selection method for solving a self-interference and a near-far problem. It is a flowchart for demonstrating other detailed operation | movement of step S16 shown in FIG. FIG. 3 is a schematic block diagram illustrating a configuration of a wireless device illustrated in FIG. 1 in a second embodiment. It is a conceptual diagram in Embodiment 2 when combining an emergency packet and transferring by a cut-through method. FIG. 6 is a schematic block diagram showing a configuration of a wireless device shown in FIG. 1 in a third embodiment. It is a flowchart for demonstrating the other transfer method of the packet by this invention. It is a figure which shows the cut-through system using the same channel.

Explanation of symbols

  1-9, 1A, 1B wireless device, 11-20 antenna, 100 wireless network, 21-24, 21A-24A reception module, 25-28, 51-53, 221-224 delay circuit, 29-32, 54-56 , 67 to 70, 225 to 228 multiplier, 33, 57, 71, 229 synthesis module, 34, 58, 72, 215 to 218, 230 to 234 bit decision unit, 35 to 39, 61 to 64 buffer, 40 label check / Scheduling module, 41, 66 timer, 42, 65 MAC module, 43-48, 73 transmission module, 50, 50A combiner, 211-214 despreader.

Claims (10)

A wireless device that forwards broadcast packets,
Receiving means for receiving a plurality of packets from a plurality of different wireless devices;
A wireless device comprising transfer means for combining a plurality of packets received by the receiving means and transferring the combined packets.   The wireless device according to claim 1, wherein the transfer unit starts combining the plurality of packets and transferring the combined packet before the reception unit finishes receiving the plurality of packets.   The wireless device according to claim 2, wherein each of the plurality of packets includes emergency information. Whether identification information for identifying the type of information included in the packet is detected from the head of each of the plurality of packets, and whether or not the plurality of packets include the same identification information based on the detected plurality of identification information A determination means for determining
4. The transfer unit according to claim 2 or 3, wherein when the determination unit determines that the plurality of packets include the same identification information, the transfer unit starts combining the plurality of packets and transferring the combined packet. Wireless devices. The transfer means includes
Combining means for combining a plurality of bit strings included in the plurality of packets;
Bit determining means for determining a bit of the combined bit string combined by the combining means;
The wireless device according to claim 4, further comprising: a transmission unit that transmits a bit string determined by the bit determination unit. The transfer means includes
A plurality of first bit determining means provided corresponding to a plurality of packets, each of which determines a bit of data included in the corresponding packet;
Combining means for combining a plurality of bit strings determined by the plurality of first bit determining means;
Second bit determining means for determining a bit of the combined bit string combined by the combining means;
The wireless device according to claim 4, further comprising: a transmission unit that transmits the bit string determined by the second bit determination unit. The receiving unit is arbitrarily selected from N (N is an integer of 2 or more) channel groups, which are integers equal to or greater than a division value obtained by dividing the transmission time at the transmission source of the plurality of packets by the delay time in packet transfer by the transfer unit. Receiving the plurality of packets using m (m is a positive integer) channels included in the first channel group selected in
The transfer means uses the n (n is a positive integer) number of channels included in the N channel groups and included in a second channel group different from the first channel group, and the combined packet. The wireless device according to claim 1, wherein the wireless device is transferred. Each of the plurality of packets has a packet size greater than or equal to a reference size;
The radio apparatus according to claim 7, wherein the N channel groups include three or more channel groups.   The wireless device according to claim 1, wherein when the plurality of packets include an error, the transfer unit combines and transfers the plurality of packets.   A wireless network comprising the wireless device according to any one of claims 1 to 9.

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