JP5082590B2 - Communication device and communication network - Google Patents

Description

  The present invention relates to a communication device and a communication network that perform communication connection using a carrier sense function.

  As a communication network having a carrier sense function, for example, a wireless LAN (Local Area Network) is known. As a wireless LAN technology, for example, one standardized by IEEE 802.11 is known. As a document disclosing a wireless LAN compliant with IEEE802.11, for example, the following Patent Document 1 is known.

  In a wireless LAN, since a plurality of neighboring wireless communication terminals simultaneously perform wireless transmission, there is a possibility that transmission signals collide with each other and normal communication cannot be performed. As one of techniques for preventing such signal collision, CSMA (Carrier Sense Multiple Access) is known. In CSMA, carrier sense is performed in order to avoid collision of radio signals. Carrier sense is processing for determining that communication is not being performed when carrier non-detection continues for a certain time (IFS: Inter Frame Space). However, even when carrier sense is performed, a collision may occur. Such a signal collision is likely to occur, for example, when a plurality of wireless communication terminals are in a transmission waiting state during communication of any one of the wireless communication terminals belonging to the same network. This is because these transmission-waiting wireless communication terminals start the IFS time simultaneously with the end of the communication, and therefore the end timing of the IFS time is also the same.

  Back-off control is known as a technique for further reducing the collision occurrence probability. The back-off control is control in which, after performing carrier sensing for the IFS time, the wireless communication terminal further continues carrier sensing for a randomly determined time (that is, back-off time). By setting the back-off time at random, it is possible to further reduce the probability that the radio signals collide compared with the case of waiting for only IFS. As the back-off control, for example, one standardized by IEEE 802.11 is known.

  FIG. 11 is a conceptual diagram for explaining the back-off control defined in IEEE 802.11. Here, a case where three wireless communication terminals DIV1, DIV2, and DIV3 are waiting for transmission to the access point AP will be described as an example.

  In FIG. 11, from time t0 to time t1, for example, another wireless communication terminal transmits to the access point AP. A transmission request is generated in each of the wireless communication terminals DIV1, DIV2, and DIV3 during the communication of the wireless communication terminal. Thereby, the radio communication terminals DIV1, DIV2, and DIV3 start carrier sense.

  The wireless communication terminals DIV1, DIV2, and DIV3 determine that the communication is completed when the duration of the state in which no carrier is detected reaches the IFS time (that is, from time t1 to time t2). Further, the wireless communication terminals DIV1, DIV2, and DIV3 start back-off control. As described above, the length of the IFS time is the same among the wireless communication terminals DIV1, DIV2, and DIV3, but the length of the back-off time is random. The length of this back-off time is, for example, the product of a randomly generated back-off value (for example, any one of 0 to 15) and the slot time. The back-off value is generated using a random number generation function built in the wireless communication terminals DIV1, DIV2, and DIV3. The slot time is, for example, 51.2 microseconds when the wireless communication speed is 10 Mbps, and 5.12 microseconds when the wireless communication speed is 100 Mbps.

In the example of FIG. 11, the back-off time of the wireless communication terminal DIV1 is 7 × slot time, the back-off time of the wireless communication terminal DIV2 is 10 × slot time, and the back-off time of the wireless communication terminal DIV3 is 15 × slot time. Therefore, when the wireless communication terminal DIV1 starts transmission at time t3, the wireless communication terminals DIV2 and DIV3 do not start transmission. Then, the wireless communication terminals DIV2 and DIV3 detect the start of transmission of the wireless communication terminal DIV1 by carrier sense, and therefore do not start transmission even when their own back-off time ends. Therefore, in the case of FIG. 11, no signal collision occurs.
Japanese Patent Laid-Open No. 2002-247051 (see paragraphs 0001 to 0012)

  However, the conventional back-off control cannot completely prevent signal collision. This is because the above-described back-off value may match between different wireless communication terminals.

  In the example of FIG. 12, the backoff times of the radio communication terminals DIV1 and DIV2 are both 7 (backoff value) × slot time. The wireless communication terminals DIV1 and DIV2 perform carrier sense between times t1 and t3, but communication of other wireless communication terminals is not detected. For this reason, the radio communication terminals DIV1 and DIV2 start transmission simultaneously at time t3, and signal collision occurs. Thus, in the conventional back-off control, signal collision occurs when a plurality of wireless communication terminals having the smallest back-off value are generated.

  Here, it is also possible to reduce the probability of occurrence of signal collision by increasing the types of back-off values that can be generated (and therefore the types of back-off times that can be selected). However, even if the types of back-off values are increased, the signal collision probability when the IFS time ends simultaneously cannot be made zero. In addition, as the types of back-off values that each wireless communication terminal DIV1, DIV2, and DIV3 can take increase, the possibility that the back-off time becomes longer increases accordingly, and as a result, there are wireless communication terminals that are in a transmission waiting state. Nevertheless, the average value of the time when communication is not started (see t2 to t3 in FIG. 11) increases. As a result, the bandwidth usage efficiency of the communication network is reduced.

  An object of the present invention is to provide a communication network that can prevent signal collision and has high band use efficiency.

  The first invention includes carrier sense means for performing carrier sense, transmission timing processing means for determining the duration of the carrier sense after detection of non-execution of communication, and communication start is not detected during the duration It is related with the communication apparatus which has a transmission means which starts transmission in the case of being.

The transmit timing processing means, a random number generator for generating a random number, a seed supply portion for supplying the random number generator with the time information and shea over de, is the communication device to join with the seed using the identification number string including the identification numbers of all communication devices included in the communication network that is transmitted from the access point of the communication network, the priority sequence indicating a transmission priority according to all the communication devices, using the random number generated Te, it determines the transmission priority of its own device based on the priority sequence, and a duration calculator for determining the continuation time in accordance with the transmit priority.
In the second invention, the transmission timing means of the communication device includes identification numbers of all the communication devices of the communication network in which the random number generation unit, the seed supply unit, and the communication device participate. Using the identification number sequence, a priority sequence indicating the transmission priority order for all communication devices is generated using this random number, the transmission priority order of the own device is determined based on the priority sequence, and the transmission priority order And a duration calculation unit for determining the duration according to the number of identification numbers of each communication device included in the identification number string is determined according to the communication band ratio of each communication device.

The third invention is a carrier sense means for performing carrier sense, a transmission timing processing means for determining the duration of carrier sense after detection of non-execution of communication, and a case where communication start is not detected during the duration The present invention relates to a communication network that accommodates a plurality of communication devices having transmission means for starting transmission.

The transmission timing processing means of each communication device generates a random number using a seed, a seed supply unit for supplying time information as a seed to the random number generator , and identification of all communication devices using the identification number string including the number, the priority sequence indicating a transmission priority according to all communication devices, generated using a random number, determines the transmission priority of its own device based on the priority sequence, the A duration calculation unit that determines a duration according to the transmission priority order, and determines the number of identification numbers of each communication device included in the identification number string according to the communication band ratio of each communication device.

  In the communication device and the communication network of the present invention, a priority sequence of communication devices is generated using random numbers. Then, each communication device determines its own transmission priority from this priority sequence, and determines the duration of carrier sense.

  Here, in the present invention, since time information is used as a seed, when a plurality of communication devices simultaneously perform random number generation computation, the same seed is used, and therefore, these communication devices are determined. The priority sequences thus matched also match each other. For this reason, when these communication devices detect the end of another communication at the same time, there is no possibility that the durations of carrier sense match between these communication devices. Therefore, the signal collision probability when communication non-execution is simultaneously detected can be made zero.

  Further, according to the present invention, since there is no need to increase the types of durations that can be selected, there is no increase in the average time during which communication is not started even though there are wireless communication terminals waiting to be transmitted. Therefore, it is possible to reduce the signal collision probability without reducing the bandwidth usage efficiency of the communication network.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the size, shape, and arrangement relationship of each component are shown only schematically to the extent that the present invention can be understood, and the numerical conditions described below are merely examples. .

<First Embodiment>
A communication network according to an embodiment of the present invention will be described with reference to FIGS. 1 to 8 by taking as an example the case where the present invention is applied to a wireless LAN.

  FIG. 1 is a conceptual diagram showing a network configuration of a wireless LAN according to this embodiment. As illustrated in FIG. 1, the wireless LAN 100 according to this embodiment includes one wireless access point 101 and three wireless communication terminals 111, 112, and 113.

  FIG. 2 is a block diagram showing a main configuration of each wireless communication terminal 111, 112, 113. As illustrated in FIG. 2, the wireless communication terminals 111, 112, and 113 include an application data generation unit 210, an application data processing unit 220, an access control unit 230, a transmission unit 240, and a reception unit 250.

  The application data generation unit 210 sends the wireless transmission data generated by the application to the access control unit 230.

  The application data processing unit 220 receives the wirelessly received data from the access control unit 230 and performs predetermined processing.

  The access control unit 230 performs processing for sending data received from the application data generation unit 210 to the transmission unit 240 and processing for sending data received from the reception unit 250 to the application data processing unit 220. The internal configuration of the access control unit 230 will be described later.

  The transmission unit 240 converts data received from a transmission buffer 231 (described later) of the access control unit 230 into a radio signal and outputs the radio signal.

  The receiving unit 250 receives a radio signal, converts it into electrical data, and sends it to a reception buffer 232 (described later) of the access control unit 230. In addition, the receiving unit 250 converts the radio wave received at the time of carrier sensing into an electric signal and sends it to a carrier sensing unit 233 (described later) of the access control unit 230. Furthermore, the receiving unit 250 receives the synchronization signal and sends it to a transmission timing processing unit 234 (described later) of the access control unit 230.

  Next, the internal configuration of the access control unit 230 will be described. As illustrated in FIG. 2, the access control unit 230 includes a transmission buffer 231, a reception buffer 232, a carrier sense unit 233, and a transmission timing processing unit 234.

  The transmission buffer 231 temporarily stores the transmission data received from the application data generation unit 210, and sends the wireless transmission data to the transmission unit 240 when a transmission instruction signal (described later) is received.

  The reception buffer 232 temporarily stores the reception data received from the reception unit 250 and outputs it in response to a request from the application data processing unit 220.

  The carrier sense unit 233 detects the intensity of the signal input from the receiving unit 250, and generates and outputs carrier information based on the detection result. For example, when the detected value exceeds a predetermined threshold value, carrier information indicating carrier detection (for example, signal value “1”) is generated and output, and the detected value falls below the threshold value. If it is detected, carrier information (for example, signal value “0”) indicating carrier non-detection is generated and output.

  The transmission timing processing unit 234 generates a transmission instruction signal and sends it to the transmission buffer 231. The transmission timing processing unit 234 includes a random number generation unit 234a, an identification number management unit 234b, a backoff time calculation unit 234c, a transmission instruction generation unit 234d, a timer 234e, and a synchronization processing unit 234f.

  The random number generator 234a performs a random number calculation using a seed. As is well known, in a random number calculation using a seed, the random numbers calculated using the same seed are the same (see, for example, paragraph 0005 of JP-A-2004-234153). Therefore, when the wireless communication terminals 111, 112, and 113 perform random number calculation using the same seed, the same random number is obtained.

  The identification number management unit 234b stores an identification number assigned to the terminal itself and an identification number string composed of identification numbers of all terminals. In this embodiment, the identification numbers of the wireless communication terminals 111, 112, and 113 (see FIG. 1) are “1”, “2”, and “3”. Therefore, for example, “1” is stored as the identification number of the own terminal in the identification number management unit 234 b of the wireless communication terminal 111. In this embodiment, as the identification number string, all combinations of the arrangement numbers of the identification numbers of the terminals, that is, (1,2,3), (1,3,2), (2,1,3),. .. Are all stored.

  The back-off time calculation unit 234c generates a priority sequence indicating the transmission priority order for all the communication terminals 111, 112, and 113 using the random numbers generated by the random number generation unit 234a, and the priority sequence. A process for determining the transmission priority of the terminal itself based on the transmission priority and a process for determining a backoff time (corresponding to the “duration” of the present invention) according to the transmission priority (described later).

  Upon receiving an external transmission command, the transmission instruction generation unit 234d checks the carrier information received from the carrier sense unit 233 until the IFS time elapses. If no carrier is detected, the transmission instruction generation unit 234d further performs a backoff time. The carrier information is checked until elapses. If the carrier is not detected even after the back-off time has elapsed, the transmission instruction generation unit 234d generates a transmission instruction signal and sends it to the transmission buffer 231.

  The timer 234e generates time information and supplies it as a seed to the random number generator 234a. This seed may be, for example, information on the time itself, or information indicating an elapsed time since the wireless LAN 100 was started up. If the value that changes according to the time and the value corresponding to the same time always becomes the same value, it can be adopted as the time information according to this embodiment.

  The synchronization processing unit 234f synchronizes the timers 234e of the wireless communication terminals 111, 112, and 113. For example, the synchronization processing unit 234f of each wireless communication terminal 111, 112, 113 corrects the timer 234e based on the synchronization information transmitted from the wireless access point 101, so that the timers of these wireless communication terminals 111, 112, 113 234e can be synchronized. The method of providing the synchronization information from the wireless access point 101 to the wireless communication terminals 111, 112, and 113 is arbitrary. For example, the synchronization information is stored in a connection information packet or a control packet called a beacon and wireless access is performed. It can be sent from the point 101 to each wireless communication terminal 111, 112, 113.

  Next, the operation of the wireless LAN 100 will be described with reference to FIGS.

  FIG. 3 is a conceptual diagram for explaining the processing of the back-off time calculation unit 234c.

  First, the backoff time calculation unit 234c generates a priority sequence. The priority sequence can be generated, for example, by shuffling the identification number sequence according to a random number. Although the shuffling method is arbitrary, for example, a plurality of types of identification number sequences are stored in a table in the identification number management unit 234b (see FIG. 2), and any one identification number sequence is set according to the random number value. To select. In addition, for example, a method of performing the process of exchanging the pair of identification numbers according to the value of the random number may be performed once or a plurality of times (in this case, the identification number string stored in the identification number management unit 234b may be one type). ). Any method can be used as the shuffle method of this embodiment as long as the shuffle results corresponding to the same random number (and therefore the same seed) are always the same.

  Next, the backoff time calculation unit 234c determines the transmission priority of the terminal itself. This determination is performed by determining the position of the own terminal in the priority sequence (that is, the identification number sequence after shuffling) (what number the identification number of the own terminal is from the higher order side). In the example of FIG. 3, since the priority order column is (1, 3, 2), the priority order of the wireless communication terminal 111 is first, the priority order of the wireless communication terminal 112 is third, and the priority order of the wireless communication terminal 113 is Second (here, it is assumed that the transmission priority is higher on the left side).

  Subsequently, the back-off time calculation unit 234c calculates a back-off time according to the transmission priority order of the terminal itself. The back-off time is determined by calculating the product of the back-off value and the slot time. In this embodiment, the result of subtracting “1” from the transmission priority is used as the back-off value. As a result, in the case of FIG. 3, since the wireless communication terminal 111 has the first priority, the back-off time is “0”. Further, since the wireless communication terminal 112 has the third priority, the back-off time is twice the slot time. Further, since the wireless communication terminal 113 has the second priority, the back-off time is one time the slot time. The slot time can be set arbitrarily, and may be the same as before (51.2 microseconds when the wireless communication speed is 10 Mbps, 5.12 microseconds when the wireless communication speed is 100 Mbps).

  4A and 4B are conceptual diagrams for explaining an operation of storing an identification number and an identification number string in the identification number management unit 234b of each wireless communication terminal 111, 112, 113.

  When the wireless LAN 100 is started up or when a wireless communication terminal to be accommodated is added or changed, the identification number and identification number string are updated from the wireless access point 101 to each wireless communication terminal 111, 112, 113. A communication frame for notification is transmitted. As shown in FIG. 4A, the communication frame includes a transmission source address (that is, the address of the wireless access point 101), a destination address (that is, an address of the wireless communication terminal that is the destination), and an identification number ( That is, it includes an identification number of the wireless communication terminal corresponding to the destination address) and an identification number string (that is, an identification number string including identification numbers of all the wireless communication terminals after update). As described above, the identification number string is determined according to the shuffle method. For example, when the shuffle method is a method of selecting any one of a plurality of types of identification number sequences according to a random number value, all of the plurality of types of identification number sequences are stored in the communication frame (FIG. 4). (See (B)). On the other hand, in the case of the shuffle method for generating the transmission priority from one identification number string, only such one identification number string is stored in the communication frame.

  As shown in FIG. 4B, the wireless access point 101 generates a communication frame for each wireless communication terminal and wirelessly transmits it. Each wireless communication terminal 111, 112, 113 receives these communication frames at the receiving unit 250, reads the received address, determines the destination of the communication frame, and if the destination is its own terminal, the identification number The identification number string is stored in the identification number management unit 234b. If the destination is not its own terminal, the wireless communication terminals 111, 112, and 113 discard the communication frame.

  FIG. 5 is a flowchart for explaining the operation of the transmission instruction generation unit 234d.

  The transmission instruction generation unit 234d starts checking whether a transmission request is generated or not at the same time when the wireless communication terminal is powered on (see step S501).

  When a transmission request is generated, the transmission instruction generation unit 234d checks whether other wireless communication is performed as follows.

  First, the transmission instruction generation unit 234d instructs the carrier sense unit 233 to start generating carrier information (see step S502).

  Then, the transmission instruction generator 234d sets the IFS time T1 to “0” (see step S503).

  The transmission instruction generation unit 234d inputs the carrier information and checks carrier detection / non-detection (see step S504). If a carrier is detected, it is determined that one of the wireless communication terminals is transmitting to the wireless access point 101, and the process returns to step S503.

  On the other hand, if no carrier is detected in step S504, the transmission instruction generation unit 234d adds a predetermined constant C1 to the no-communication time timer value T1 (see step S505). The value of the constant C1 is determined according to the processing time for one time of the loop composed of steps S504 to S506, and is therefore determined in consideration of the operating frequency of the processor that executes the processing according to this flowchart.

  Next, the transmission instruction generation unit 234d compares the value T1 with the IFS time (see step S506), and if T1 ≦ IFS, returns to step S504.

  If T1> IFS in step S506, that is, if the duration of the carrier non-detection state has reached IFS, the transmission instruction generation unit 234d determines that no other communication is performed. Then, the transmission instruction generation unit 234d starts back-off control.

  In the back-off control, first, the transmission instruction generation unit 234d instructs the back-off time calculation unit 234c to calculate the back-off time (see step S507). As described above, the back-off time calculation unit 234c generates a priority sequence by shuffling the identification number sequence using the random number input from the random number generation unit 234a, and determines the priority order of the terminal from the priority sequence. Determine the back-off value by subtracting '1' from this priority. Further, the back-off time calculation unit 234c calculates the back-off time by multiplying the back-off value by the slot time. The calculation result is sent from the back-off time calculation unit 234c to the transmission instruction generation unit 234d.

  The transmission instruction generation unit 234d sets the built-in timer value T2 to ‘0’ (see step S508).

  Subsequently, the transmission instruction generation unit 234d compares the value T2 with the backoff time Tb received from the backoff time calculation unit 234c (see step S509).

  Next, when the value T2 is T2 ≦ Tb in step 509, the transmission instruction generation unit 234d inputs the carrier information and checks carrier detection / non-detection (see step S510). If a carrier is detected, it is determined that one of the wireless communication terminals is transmitting to the wireless access point 101, and the process returns to step S502.

  On the other hand, if no carrier is detected in step S510, the transmission instruction generation unit 234d adds a predetermined constant C2 to the no-communication time timer value T2 (see step S511). The value of the constant C2 is determined according to the processing time for one time of the loop composed of steps S509 to S511, and is therefore determined in consideration of the operating frequency of the processor that executes the processing according to this flowchart.

  When the value T2 is larger than the back-off time in step S509, that is, when the duration in which no carrier is detected reaches the back-off time, the transmission instruction generation unit 234d determines that other communication has not started. The transmission instruction signal is output (see step S512). As a result, the transmission buffer 231 (see FIG. 2) starts transmission.

  6 and 7 are conceptual diagrams for explaining the overall operation of the wireless LAN 100. FIG.

  In FIG. 6, at time t0, one of the wireless communication terminals 111, 112, and 113 (or another wireless communication terminal not shown) starts transmission to the access point 101. A transmission request is generated in each of the wireless communication terminals 111, 112, and 113 during the communication of the wireless communication terminal. Thereby, the radio communication terminals 111, 112, and 113 start carrier sense.

  At time t1, such communication ends. Thereby, each wireless communication terminal 111, 112, 113 starts measuring the IFS time (see FIG. 5).

  At time t2, the duration in which no carrier is detected reaches the IFS time. As a result, each of the wireless communication terminals 111, 112, and 113 determines that this communication has ended. As described above, when a transmission request is generated in each of the wireless communication terminals 111, 112, and 113 while another communication is continued, the wireless communication terminals detect the end of the communication at the same timing. Therefore, the wireless communication terminals 111, 112, and 113 simultaneously start back-off control.

  As a result, each wireless communication terminal 111, 112, 113 starts calculating the back-off time at the same time (see FIG. 5). As described above, each wireless communication terminal 111, 112, 113 generates a random number using the seed generated by the timer 234e, and shuffles the identification number sequence according to this random number. Here, since the timers 234e of the wireless communication terminals 111, 112, and 113 are synchronized, when these wireless communication terminals simultaneously start back-off control, the seed value is the same among the wireless communication terminals. Further, when the seeds are the same, the generated random values are also the same. Furthermore, when the random number values are the same, the shuffle results are also the same. Therefore, each wireless communication terminal 111, 112, 113 generates the same shuffle result (that is, the same priority sequence). For example, in FIG. 3 described above, the same priority sequence (1, 3, 2) is generated in all the wireless communication terminals 111, 112, 113.

  Thereafter, each wireless communication terminal 111, 112, 113 determines its own transmission priority from the priority sequence generated by each, and calculates the back-off time using this transmission priority. As described above, since these priority sequences are the same, there is no possibility that the priorities of the wireless communication terminals 111, 112, and 113 are the same. Accordingly, there is no possibility that the back-off times of the wireless communication terminals 111, 112, and 113 are the same.

  In the example of FIG. 3, the priority of the wireless communication terminal 111 is “1”, the priority of the wireless communication terminal 112 is “3”, and the priority of the wireless communication terminal 113 is “2”. Therefore, the back-off time is “0” for the wireless communication terminal 111, “2 × slot time” for the wireless communication terminal 112, and “1 × slot time” for the wireless communication terminal 113. For this reason, the wireless communication terminal 111 immediately starts transmission, but the other wireless communication terminals 112 and 113 continue carrier sense without starting transmission (see FIG. 7).

  When the wireless communication terminal 111 starts transmission, in the wireless communication terminals 112 and 113, the carrier sense unit 233 detects the carrier. Therefore, the transmission instruction generation unit 234d of the wireless communication terminals 112 and 113 stops the back-off control (see FIG. 5). Therefore, the wireless communication terminals 112 and 113 do not start transmission even when the back-off time has elapsed, and therefore no signal collision occurs.

  If a transmission request is not generated in the wireless communication terminal 111, the wireless communication terminal 113 starts transmission after “1 × slot time” has elapsed since the start of backoff control. Thereby, in the wireless communication terminal 112, since the carrier sense part 233 detects a carrier, back-off control is stopped.

  If no transmission request is generated in both the wireless communication terminals 111 and 113, the wireless communication terminal 112 starts transmission after ‘2 × slot time’ has elapsed since the start of the back-off control.

  As described above, in the wireless LAN according to this embodiment, each wireless communication terminal does not randomly generate only its own backoff time as in the prior art, but first, priorities of all wireless communication terminals are set. A priority sequence including the same is generated, and its own back-off time is determined according to the priority of the own terminal included in the priority sequence. In the present invention, the seeds generated at the same time are the same among a plurality of wireless communication terminals, and therefore the random numbers are the same, and therefore the priority sequence is the same. For this reason, each terminal calculates the back-off time according to the priority of its own terminal using the same priority sequence. Therefore, in this embodiment, when a plurality of wireless communication terminals perform back-off control at the same time, the back-off times of these wireless communication terminals always have different values, and there is no possibility of signal collision.

  Furthermore, according to this embodiment, the type of back-off time that can be selected may be the same as the number of wireless communication terminals accommodated in the wireless LAN 100. Therefore, the non-communication time due to the fact that communication is not started despite the presence of a wireless communication terminal waiting for transmission is very short. Therefore, according to this embodiment, the band use efficiency of the wireless LAN can be improved. However, the present invention is not limited to the case where the type of back-off time that can be selected is the same as the number of wireless communication terminals.

<Second Embodiment>
Next, a communication network according to a second embodiment of the present invention will be described with reference to FIGS. 8 and 9, taking as an example a case where it is applied to a wireless LAN.

  This embodiment is an example of a wireless LAN that can accommodate a plurality of wireless communication terminals having different communication bands.

  FIG. 8 is a conceptual diagram for explaining the network configuration of the wireless LAN according to this embodiment.

  As shown in FIG. 8, the wireless LAN 800 according to this embodiment includes one wireless access point 801 and three wireless communication terminals 811, 812, and 813.

  Here, the wireless communication terminals 811, 812, and 813 communicate with the wireless access point 801 using the same frequency band. In this embodiment, the identification number of the wireless communication terminal 811 is ‘1’, the identification number of the wireless communication terminal 812 is ‘2’, and the identification number of the wireless communication terminal 813 is ‘3’. Further, the ratio Z1: Z2: Z3 of communication bands assigned to the wireless communication terminals 811 812 813 is 1: 2: 3.

  The configuration of the wireless communication terminal according to this embodiment is substantially the same as that of the first embodiment described above. However, the information stored in the identification number management unit 234b (see FIG. 2) is different from that in the first embodiment.

  Each identification number string of the identification number management unit 234b includes one “1”, two “2”, and three “3”. That is, the number of identification numbers included in the identification number sequence is determined according to the communication band ratios Z1, Z2, and Z3 of the wireless communication terminals corresponding to these identification numbers. Similar to the first embodiment, the identification number management unit 234b includes all combinations of the arrangement order of these identification numbers, that is, (1, 2, 2, 3, 3, 3), (1, 2, 3, 2, 3, 3), (1, 3, 3, 2, 2, 3),... Can be stored in a table. As in the first embodiment, these identification number sequences are converted into communication frames, for example, and supplied from the wireless access point 801 to the wireless communication terminals 811 812 813.

  FIG. 9 is a conceptual diagram for explaining the operation of the wireless LAN according to this embodiment.

  The back-off time calculation unit 234c selects any one of these identification number strings during the shuffle process. As a result, a priority sequence is generated. Note that only one type of identification number sequence, for example, (1, 2, 2, 3, 3, 3) is stored in the identification number management unit 234b, and the shuffling process of the back-off time calculation unit 234c allows The arrangement order of the identification numbers may be changed.

  Subsequently, the back-off time calculation unit 234c calculates the back-off time of each wireless communication terminal 811, 812, 813 using this priority sequence. First, the back-off time calculation unit 234c assigns back-off values “0”, “1”, and “2” one by one in descending order of priority among the wireless communication terminals 811, 812, and 813. For example, when the identification number string after shuffling is (3, 2, 2, 3, 1, 3), the back-off time calculation unit 234c sets the back-off value to “0” for the first identification number “3”. And a back-off value “1” is assigned to the second identification number “2”. The third identification number is “2”, but this identification number “2” is already assigned a back-off value “1”, and is ignored. Similarly, no back-off value is assigned to the fourth identification number “3”. Then, a back-off value “3” is assigned to the fifth identification number “1”.

  Thereafter, each back-off time calculation unit 234c calculates the back-off time by multiplying the back-off value by the slot time.

  Thereafter, transmission according to the priority order is performed in the same manner as in the first embodiment. Here, since the priority order of the wireless communication terminal 813 is “1”, the wireless communication terminal 813 performs transmission with a turn-off time of “0”.

  According to such processing, the probability that the transmission priority of each of the wireless communication terminals 811, 812, 813 is “1” is 1: 2: 3.

  Other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted.

  As described above, according to this embodiment, the ratio of communication bands allocated to the wireless communication terminals 811, 812, 813 can be set only by the number of identification numbers included in the identification number string. That is, according to this embodiment, the communication band ratio can be set easily and inexpensively in a wireless LAN that accommodates a plurality of wireless communication terminals using the same frequency.

  In addition, the wireless LAN according to this embodiment can completely prevent signal collision when a plurality of communication devices simultaneously start back-off control for the same reason as in the first embodiment. Bandwidth usage efficiency can be improved.

<Third Embodiment>
Next, a communication network according to a third embodiment of the present invention will be described with reference to FIG.

  This embodiment is an example of a wireless LAN in which a transmission priority can be set for each wireless communication terminal.

  FIG. 10 is a conceptual diagram for explaining the network configuration of the wireless LAN according to this embodiment.

  As shown in FIG. 10A, the wireless LAN 1000 according to this embodiment includes one wireless access point 1001 and five wireless communication terminals 1011, 1012, 1013, 1014, and 1015.

  In this embodiment, the identification number of the wireless communication terminal 1011 is “1”, the identification number of the wireless communication terminal 1012 is “2”, the identification number of the wireless communication terminal 1013 is “3”, and the identification number of the wireless communication terminal 1014 is “ 4 ”and the identification number of the wireless communication terminal 1015 is“ 5 ”. Further, the transmission priority of the wireless communication terminals 1011 and 1013 is set as the higher rank, and the transmission priority of the other wireless communication terminals 1012, 1014 and 1015 is set as the lower rank.

  The configuration of the wireless communication terminal according to this embodiment is substantially the same as that of the first embodiment described above. However, the data structure of the identification number sequence stored in the identification number management unit 234b (see FIG. 2) and the shuffling method of the back-off time calculation unit 234c are different from those in the first embodiment.

  The identification number management unit 234b stores a group of identification number sequences consisting of only identification numbers with higher transmission priority and a group of identification number sequences with lower transmission priority (see FIG. 10B). These identification number strings are supplied from the wireless access point 1001 to the wireless communication terminals 1011 to 1015 and stored in the respective identification number management units 234b.

  In this embodiment, the back-off time calculation unit 234c shuffles the identification number sequence for each group individually during the shuffling process. As in the first embodiment, the shuffling method may be a method of selecting any one of a plurality of types of groups including the same identification number, or preparing only one type of identification number sequence for each group. A method of changing the order of the identification numbers in the group may be used. Here, the shuffle result of the upper group is (3, 1), and the shuffle result of the lower group is (4, 5, 2).

  Subsequently, the back-off time calculation unit 234c generates a priority sequence by combining the shuffled groups. At this time, these groups are combined so that the transmission priority of the identification numbers belonging to the higher rank group becomes higher. Here, the priority sequence is (3, 1, 4, 5, 2).

  The backoff time calculation unit 234c determines a backoff value for each of the wireless communication terminals 1011 to 1015 based on this priority sequence. As in the first embodiment, the back-off value is a value obtained by subtracting ‘1’ from the transmission priority. In the example of FIG. 10, the back-off value of the wireless communication terminal 1011 is “1”, the back-off value of the wireless communication terminal 1012 is “4”, the back-off value of the wireless communication terminal 1013 is “0”, The back-off value is “2”, and the back-off value of the wireless communication terminal 1015 is “3”.

  Further, the back-off time calculation unit 234c calculates the back-off time by multiplying each back-off value by the slot time.

  Thereafter, transmission according to the priority order is performed in the same manner as in the first embodiment. Here, since the priority order of the wireless communication terminal 1013 is ‘1’, the turn-off time of the wireless communication terminal 1013 becomes ‘0’. Therefore, when a transmission request is generated in the wireless communication terminal 1013, the wireless communication terminal 1013 performs transmission.

According to such processing, the wireless communication terminals 1011 and 1013 can always perform transmission with priority over the other wireless communication terminals 1012, 1014, and 1015.
Since the operation is the same as that of the first embodiment, description thereof is omitted.

  As described above, according to this embodiment, the transmission priority can be set for each wireless communication terminal. Therefore, the higher priority wireless communication terminal can perform transmission with priority over the lower wireless communication terminal.

  In addition, the wireless LAN according to this embodiment can completely prevent signal collision when a plurality of communication devices simultaneously start back-off control for the same reason as in the first embodiment. Bandwidth usage efficiency can be improved.

It is a conceptual diagram which shows the structure of the communication network which concerns on 1st Embodiment. It is a block diagram which shows the principal part structure of the radio | wireless communication terminal which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating operation | movement of the communication network which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating operation | movement of the communication network which concerns on 1st Embodiment. It is a flowchart for demonstrating operation | movement of the communication network which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating operation | movement of the communication network which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating operation | movement of the communication network which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating the structure of the communication network which concerns on 2nd Embodiment. It is a conceptual diagram for demonstrating operation | movement of the communication network which concerns on 2nd Embodiment. It is a conceptual diagram for demonstrating the structure of the communication network which concerns on 3rd Embodiment. It is a conceptual diagram for demonstrating the conventional back-off control. It is a conceptual diagram for demonstrating the conventional back-off control.

Explanation of symbols

100 wireless LAN
DESCRIPTION OF SYMBOLS 101 Wireless access point 111,112,113 Wireless communication terminal 210 Application data generation part 220 Application data processing part 230 Access control part 231 Transmission buffer 232 Reception buffer 233 Carrier sense part 234 Transmission timing processing part 234a Random number generation part 234b Identification number management part 234c Backoff time calculation unit 234d Transmission instruction generation unit 234e Timer 234f Synchronization processing unit 240 Transmission unit 250 Reception unit

Claims (10)

Carrier sense means for performing carrier sense, transmission timing processing means for determining the duration of the carrier sense after communication non-execution is detected, and transmission start when communication start is not detected during the duration A communication device comprising:
The transmission timing processing means is
A random number generator that generates a random number using a seed;
A seed supply unit for supplying time information to the random number generation unit as the seed;
Priority indicating transmission priority for all communication devices using an identification number string including identification numbers of all communication devices included in the communication network transmitted from an access point of the communication network in which the communication device participates the column was generated using the random number, and determines the transmission priority of its own device based on the priority order row, and duration calculator for determining the duration in accordance with the transmission priority,
A communication apparatus comprising: The communication apparatus according to claim 1, wherein the number of the identification number of each of the communication devices included in the identification number string, and wherein the Rukoto determined according to the communication band ratio of each of the communication device. The duration calculation unit
A shuffle process for determining equal priority sequences in all the communication devices included in the communication network by shuffling an identification number sequence including all of the identification numbers assigned to each of the communication devices;
A priority determination process for determining the transmission priority of the device based on the order of the identification numbers in the priority sequence;
The communication device according to claim 1 or 2, wherein the communication device is executed. The shuffling process is a process of obtaining the priority sequence by selecting any one of a plurality of types of identification number sequences stored in advance in the communication device according to the value of the random number. The communication device according to claim 3.   5. The communication apparatus according to claim 3, wherein the shuffling process uses, as the identification number string, a number string including the identification numbers by the number corresponding to a communication band allocated to the communication apparatus. . The shuffle process is
A process of grouping all the communication devices included in the communication network for each transmission priority;
The identification number column, a process of the transmission priority is shuffled for each of the groups consisting of only the same said identification number,
Wherein as transmission priority becomes higher as the transmission priority is higher the communication device, a process of coupling the group of these identification numbers,
The communication apparatus according to claim 3 or 4, characterized by comprising: Carrier sense means for performing carrier sense, transmission timing processing means for determining the duration of the carrier sense after communication non-execution is detected, and transmission start when communication start is not detected during the duration A communication device comprising :
The previous Symbol transmission timing processing means,
A random number generator that generates a random number using a seed;
A seed supply unit for supplying time information to the random number generation unit as the seed;
The communication device using the identification number string that contains the identification number of all the communication devices of the communication network to participate, the priority sequence indicating a transmission priority according to all communication devices, generated using the random number, the Determining a transmission priority of the own device based on a priority sequence, and determining a duration according to the transmission priority;
Equipped with a,
Wherein the number of the identification number of each of the communication devices included in the identification number column, a communication device according to claim Rukoto determined according to the communication band ratio of each of the communication device.   The seed supply unit
  A timer for supplying the seed to the random number generator;
  A synchronization processing unit for synchronizing the time of the timer among all the communication devices;
  Including
  The duration calculation unit sets the duration obtained by multiplying the slot time by a value obtained by subtracting 1 from the transmission priority order in each of the communication devices.
The communication apparatus according to claim 7. The communication apparatus according to claim 7 or 8, wherein the priority sequence is generated using the identification number sequence transmitted from an access point of the communication network.   Carrier sense means for performing carrier sense, transmission timing processing means for determining the duration of the carrier sense after communication non-execution is detected, and transmission start when communication start is not detected during the duration A communication network that accommodates a plurality of communication devices having transmission means for
  The transmission timing processing means of each of the communication devices,
  A random number generator that generates a random number using a seed;
  A seed supply unit for supplying time information to the random number generation unit as the seed;
  Using the identification number sequence including the identification numbers of all the communication devices, a priority sequence indicating the transmission priority order for all the communication devices is generated using the random number, and based on the priority sequence, the own device A duration calculation unit for determining a transmission priority and determining the duration according to the transmission priority;
  With
  A communication network characterized in that the number of identification numbers of each of the communication devices included in the identification number string is determined according to a communication band ratio of each of the communication devices.

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