JP6315598B2 - Multi-hop wireless communication system, multi-hop wireless communication method, and terminal device - Google Patents

Description

  The present invention relates to a multi-hop wireless communication system, a multi-hop wireless communication method, and a terminal device in which a terminal device adjusts a detectable range of carrier sense during data transmission and performs multi-hop data transfer.

  In a wireless communication environment where a large number of terminal devices exist, the terminal device performs carrier sense to prevent interference with peripheral terminal devices during data transmission, and confirms that the peripheral terminal devices are not transmitting data before transmission. I do. Such transmission control of the terminal device is performed based on a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) system defined by IEEE802.11. The presence / absence of data transmission (busy / idle) at the time of carrier sense is determined by determining the reception level of signals from peripheral terminal devices as a threshold. Usually, the threshold value is a fixed value (IEEE802.11 specification).

  The same applies to a multi-hop network. For example, a fixed threshold value of 1: 2 is used as a ratio of a distance at which data can be transmitted and a distance at which carrier sense is possible (Non-Patent Document 1). That is, when the terminal device transmits data to the terminal device 1 hop ahead, the carrier sense sensitivity (threshold) is set so that the detectable range of carrier sense is, for example, up to 2 hops away.

FIG. 7 shows an example of the arrangement of terminal devices and data transfer control in a multi-hop network.
In FIG. 7, terminal devices A to E are configured to transfer data in a multi-hop manner. Here, the data D1 transmitted from the terminal device A is transferred to the terminal device E via the terminal devices B, C, D, and the data D2 transmitted from the terminal device E is transmitted via the terminal devices D, C, B. It is assumed that it is transferred to the terminal device A. Note that the data routing destination is known, and the terminal information of the routing destination and transfer destination (adjacent) is included in the data. Note that “adjacent terminal device” in this specification means “terminal device adjacent in the data transfer path”, and other terminal devices not in the data transfer path of the terminal device are excluded.

  Data can be transmitted and received only between adjacent terminal devices (1 hop), and carrier sense can be detected up to 2 hops away. The terminal device that has received the data returns an ACK, and the terminal device that has transmitted the data retransmits the data when no ACK is received. If there is data waiting to be transferred after transmission of one data and reception of ACK, the terminal device randomly shifts the timing by backoff control, transmits when the carrier is sensed and the channel is idle, and waits for transmission when it is busy (Normal CSMA / CA procedure).

  A control example shown in FIG. 7 will be described. Data D1 transmitted from the terminal device A is sequentially transferred from the terminal device B to the terminal device C. The terminal device C performs carrier sense for transmitting the data D1 to the terminal device D after returning the ACK. On the other hand, the terminal device E performs carrier sense for transmitting the data D2 to the terminal device D. Here, the terminal device E first transmits the data D2, and the terminal device C enters a standby state. When the terminal device D receives the data D2, it returns an ACK.

  Next, the terminal device D that has transmitted ACK performs carrier sense for transmitting the data D2 to the terminal device C. On the other hand, the terminal device C performs carrier sense for transmitting the transfer waiting data D1 to the terminal device D. Here, the terminal device C first transmits the data D1, and the terminal device D enters a standby state. When the terminal device D receives the data D1, it returns an ACK. At this time, the terminal device D has data D2 to be transmitted to the terminal device C and data D1 to be transmitted to the terminal device E. The data D2 received earlier is transmitted to the terminal device C, and the terminal device C ACK is returned.

  Next, the terminal device C that has transmitted ACK performs carrier sense for transmitting the data D2 to the terminal device B. On the other hand, the terminal device D performs carrier sense for transmitting the transfer waiting data D1 to the terminal device E. Here, the terminal device C first transmits the data D2, and the terminal device D enters a standby state. When the terminal device B receives the data D2, it returns an ACK. The terminal device B that has returned the ACK performs carrier sense for transmitting the data D2 to the terminal device A. On the other hand, the terminal device D performs carrier sense for transmitting the transfer waiting data D1 to the terminal device E. Here, the terminal device B first transmits the data D2, and the terminal device D continues in the standby state. When the terminal device A receives the data D2, it returns an ACK.

  The terminal device D is waiting for transfer of data D1 transmitted to the terminal device E, but detects ACK and data D2 transmitted by the terminal device B by carrier sense, and transmits data D2 from the terminal device B. Data D1 cannot be transmitted until the end of. Then, when the terminal device B finishes transmitting the data D2, the data D1 is transmitted from the terminal device D to the terminal device E.

“[Invited Talk] Throughput Analysis in IEEE802.11 Multihop Networks”, IEICE Tech. 110 (129), 19-24, 2010-07-15

  As shown in FIG. 7, the terminal device D has a longer waiting time for data D <b> 1 to be transmitted to the terminal device E. The reason is that the terminal devices C and B that transmit the data D2 and the terminal device D that transmits the data D1 are located within two hops of each other and are within a carrier sense detectable range. That is, since the conventional detectable range of carrier sense is fixed at 2 hops, when one of the terminal devices within 2 hops transmits, the other becomes a transfer standby. However, even if the terminal device D transmits the data D1 at the timing when the terminal device C or the terminal device B transmits the data D2, the destination terminal devices B and E are separated by two hops, and the data collision occurs. Since this does not occur, the transfer waiting in the terminal device D is a useless delay.

  The present invention relates to a multi-hop wireless communication system, a multi-hop wireless communication system, and a multi-hop wireless communication system that can adjust a detectable range of carrier sense according to data transmission / reception status between adjacent terminal devices and reduce a data transfer delay to a necessary minimum. An object is to provide a communication method and a terminal device.

  The first invention is a multi-hop radio in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing prescribed carrier sense that can be detected up to two hops in the data transfer path. In a communication system, a terminal apparatus receives data 1 from an adjacent terminal apparatus in a data transfer path, detects data crossing in which data 2 is transmitted to the adjacent terminal apparatus immediately before or immediately after that, and further, a specified carrier After detecting data transmission from the adjacent terminal device to the next terminal device by sense and busy due to subsequent ACK, it is possible to detect up to one hop ahead by lowering the sensitivity of the specified carrier sense before transmitting data 1 And data 1 is transmitted with the carrier sense start timing delayed from the specified carrier sense. In subsequent data transmission comprises control means for performing carrier sense defined.

The second invention is a multi-hop wireless system in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a predetermined carrier sense that can be detected up to two hops in the data transfer path. in the communication system, terminal device, after detecting a data interleaving for receiving data 1 from the terminal device adjacent the data transfer path, and transmits the data 2 to the terminal device that the adjacent immediately before or immediately after, the data if 1 and data 2 are the same data size, by omitting a detectable to or provision of a carrier sense to less than one hop lower the sensitivity of the carrier sense defined before transmitting the data 1, data the first transmission is performed simultaneously with the transmission of data 2 by neighboring terminals, the control hand performs carrier sense defined in the subsequent data transmission Equipped with a.

  The third invention is a multi-hop wireless system in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path. In the communication method, the terminal device receives the data 1 from the adjacent terminal device in the data transfer path, and detects the data crossing in which the data 2 is transmitted to the adjacent terminal device immediately before or immediately after the data crossing, and the data crossing. After detecting the above, a step of detecting data transmission from the adjacent terminal device to the next terminal device by the prescribed carrier sense and subsequent busy by ACK, and before transmitting data 1 after detecting the busy, Decrease the sensitivity of the specified carrier sense so that it can be detected up to one hop away, and the start of carrier sense The has a step of transmitting the data 1 is delayed than the carrier sense defined and performing carrier sense defined in the data transmission after the transmission of the data 1.

The fourth invention is a multi-hop wireless system in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path. a communication method, terminal device, detecting a data interleaving for receiving data 1 from the terminal device adjacent the data transfer path, and transmits the data 2 to the terminal device that the adjacent immediately before or immediately after, A step of determining whether or not data 1 and data 2 have the same data size, and if data 1 and data 2 have the same data size, before transmitting data 1 after detection of data crossing, a prescribed carrier or a detectable to less than one hop down a sense sensitivity, or by omitting the provision of carrier sense, the end adjacent the transmission of data 1 Apparatus and performing at the same time as the transmission of data 2 by, in the data transmission after the transmission of the data 1 and performing a carrier sense defined.

  The fifth invention is a multi-hop wireless system in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a predetermined carrier sense that can be detected up to two hops in the data transfer path. A terminal device of a communication system receives data 1 from an adjacent terminal device in a data transfer path, detects data intermingling in which data 2 is transmitted to the adjacent terminal device immediately before or immediately thereafter, and further detects a specified carrier sense After detecting data transmission from the adjacent terminal device to the next terminal device and subsequent busy due to ACK, before the data 1 is transmitted, the sensitivity of the specified carrier sense is lowered to enable detection up to one hop ahead And, data 1 is transmitted by delaying the carrier sense start timing from the specified carrier sense, In the data transmission after a control means for performing carrier sense defined.

A sixth invention is a multi-hop wireless system in which a plurality of terminal apparatuses perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a predetermined carrier sense that can be detected up to two hops in the data transfer path. in the terminal device of the communication system, after detecting a data interleaving for receiving data 1 from the terminal device adjacent the data transfer path, and transmits the data 2 to the terminal device that the adjacent immediately before or immediately after the data 1 and if the data 2 have the same data size, by omitting a detectable to or provision of a carrier sense to less than one hop lower the sensitivity of the carrier sense defined before transmitting the data 1, data 1 sent conducted concurrently with the transmission of data 2 by neighboring terminals, control means for performing carrier sense defined in the subsequent data transmission Provided.

  In the first, third, and fifth inventions, when different data is transferred bi-directionally between adjacent terminal devices, when one terminal device transfers the data first, The terminal device of this device is put on standby due to carrier sense, but by making the detectable range of carrier sense 1 hop at the next timing, it becomes possible to simultaneously transmit with the terminal device 2 hops away, avoiding unnecessary delay be able to.

  In the second, fourth, and sixth inventions, when different data are transferred bi-directionally between adjacent terminal devices, if the different data have the same data size, the adjacent terminals By making the detectable range of carrier sense less than one hop in both devices or omitting carrier sense, simultaneous transmission with an adjacent terminal device is possible, and unnecessary delay can be avoided.

It is a time chart which shows the control example 1 of Example 1 of this invention. It is a time chart which shows the control example 2 of Example 1 of this invention. 5 is a flowchart illustrating an example of a processing procedure of a terminal device according to the first embodiment. It is a figure which shows the structural example of the terminal device in this invention. 10 is a flowchart illustrating an example of a processing procedure of a terminal device according to the second embodiment. It is a time chart which shows the control example of Example 2 of this invention. It is a time chart which shows the example of arrangement | positioning of a terminal device of a multihop network, and data transfer control.

Example 1
FIG. 1 shows a control example 1 of the first embodiment of the present invention. The terminal devices A to E are arranged in the same arrangement as the conventional configuration shown in FIG. The adjacent terminal devices shown here are adjacent in the data transfer path as described above.

  In FIG. 1, the terminal device C receives the data D1 transmitted from the terminal device B, and the terminal device D receives the data D1 transmitted from the terminal device E at the timing t1 and uses the data D1 and D2 as transfer destinations, respectively. In order to transmit, a prescribed carrier sense that can be detected up to two hops ahead is performed. Here, terminal device C first transmits data D1 and receives ACK from terminal device D, and then terminal device D transmits data D2 and receives ACK from terminal device C. This order may be reversed. As described above, the operation up to data crossing (1) in which the terminal device D receives the data D1 from the adjacent terminal device C and transmits the data D2 to the terminal device C immediately before or immediately after the data D1 is the control shown in FIG. Same as example.

  In the example of FIG. 1, the data crossing (1) occurs in the terminal devices C and D, but the adjacent terminal devices in which the data crossing (1) occurs depending on the data transfer status are not constant and are adjacent. In some cases, data interlace (1) does not occur between terminal devices. The present invention is applied to an adjacent terminal device in which data crossing (1) occurs.

  Next, at a timing t2, the terminal device C transmits data D2 to the terminal device B, and the terminal device D transmits data D1 to the terminal device E, so that each carrier can be detected up to two hops away. Make sense. Here, when the terminal device C first transmits the data D2 by the random back-off control, until the terminal device B receives the ACK, the terminal device D enters the transfer standby (2). In the terminal device D in this transfer standby (2), it is possible to detect the data signal transmitted / received between the terminal devices C and B and busy due to ACK by the prescribed carrier sense, but this is detected from the terminal device D itself to the terminal device C first. It can be estimated that the transmitted data D2 is transferred to the terminal device B ahead. Note that the data D2 may be demodulated to confirm that the data transmitted by the terminal device D itself is moving away.

  On the other hand, as shown in FIG. 2, when the data intersection (1) occurs between the adjacent terminal devices C and D and the terminal device D transmits the data D1 first at the timing t2, the time until the ACK is received from the terminal device E is reached. In the meantime, the terminal device C is in transfer standby (2). In the terminal device C in this transfer standby (2), it is possible to detect the data signal transmitted / received between the terminal devices D and E by the prescribed carrier sense and busy due to ACK, but this is detected from the terminal device C itself to the terminal device D first. It can be estimated that the transmitted data D1 is transferred to the terminal device E ahead.

  The feature of the first embodiment of the present invention is that in the adjacent terminal devices C and D in which the data crossing (1) is detected, the terminal device that has been in the standby state (2) (D in the case of FIG. 1, D in the case of FIG. 2) C) at the next timing t3, the sensitivity of carrier sense is lowered (threshold is raised), the detectable range is changed from 2 hops to 1 hop, and terminal devices separated by 2 hops (in the case of FIG. 1, B and D, In the case of FIG. 2, C and E) are in a position where simultaneous transmission is possible. In the subsequent data transfer, the data transfer is performed by returning to the prescribed carrier sense in which the detectable range of carrier sense is 2 hops.

FIG. 3 illustrates an example of a processing procedure of the terminal device according to the first embodiment.
In FIG. 3, the terminal device determines whether or not data crossing has been detected between adjacent terminal devices (S1). In this data crossing detection determination, the terminal device D among the terminal devices C and D shown in FIGS. 1 and 2 receives the data D1 from the adjacent terminal device C and immediately (or immediately before) receives the data D1. This can be done by transmitting the data D2 to C, and receiving the data D2 from the adjacent terminal device D and transmitting the data D1 to the terminal device D immediately before (or immediately after) the terminal device C. .

  When data crossing is not detected, the terminal device performs data transfer to other adjacent terminal devices while performing a normal carrier sense that can be detected up to two hops ahead (S6, S7).

  On the other hand, if the terminal device detects data crossing with the adjacent terminal device, the specified carrier sense is performed (S2), and the busy detection by the data transmission of the adjacent terminal device and immediately after the busy detection by ACK Whether or not the terminal device is in a transfer standby state is determined based on the presence or absence of (S3, S4). The terminal device (D in the case of FIG. 1 and C in the case of FIG. 2) that has been waiting for transfer increases the sensitivity of the carrier sense (lowers the threshold value) and changes the detectable range from 2 hops to 1 hop. The carrier sense start timing is delayed from the prescribed carrier sense (S5), and data is transferred to another adjacent terminal device (S7). On the other hand, when the terminal device is not in a transfer standby state (S3 or S4 is No), data transfer is performed to another adjacent terminal device while performing a normal carrier sense that can be detected up to two hops ahead (S6, S6). S7).

  Of the adjacent terminal devices (C and D in the case of FIGS. 1 and 2) that have been interlaced with each other by the processing of step S5, the terminal device that has been waiting for transfer (D in the case of FIG. 1, D in FIG. 2). In the case C), at the timing t3, the carrier sense detection range is set to 1 hop, and the carrier sense start timing is delayed, so that the destination terminal device (B in FIG. 1 and E in FIG. 2) Data transmission is preceded by the terminal device, and data transfer is continuously performed to another adjacent terminal device (E in FIG. 1 and B in FIG. 2) without detecting the busy state. It can be carried out. That is, in FIG. 1 or FIG. 2, the data D1 and D2 can be transferred almost simultaneously between the terminal devices separated by 2 hops, and the time during which one of them is waiting can be shortened.

FIG. 4 shows a configuration example of a terminal device according to the present invention.
In FIG. 4, a wireless transmission / reception unit 11 transmits and receives data wirelessly using an antenna or the like. The wireless interface unit 12 performs processing such as data transmission / reception and carrier sensing in accordance with instructions from the transmission / reception control unit 13. The transmission / reception control unit 13 controls the execution timing of data transmission / reception and carrier sense, and further performs the carrier sense characteristic of the present invention according to the processing procedure of the first embodiment shown in FIG. 3 or the processing procedure of the second embodiment described later. Performs processing to control sensitivity. The routing control unit 14 determines the data transfer destination and notifies the transmission / reception control unit 13. The data storage unit 15 temporarily stores data that is in a transfer standby state and data to be retransmitted. The data format processing unit 16 converts a data format such as data division / combination between the data input / output unit 17 and the wireless transmission / reception unit 11. The data input / output unit 17 performs data input / output processing.

(Example 2)
FIG. 5 illustrates an example of a processing procedure of the terminal device according to the second embodiment.
In FIG. 5, the terminal device determines whether or not the crossed data has the same data size when detecting the data crossing between the adjacent terminal devices (S1, S8). If the mixed data is not the same data size, the processing of the first embodiment shown in FIG. 3 is performed. That is, the processing of steps S2 to S6 in FIG. 3 selects whether the sensitivity of carrier sense is reduced from 2 hops to 1 hop or remains 2 hops, and performs data transfer processing to other adjacent terminal devices (S7). ).

  On the other hand, when the mixed data has the same data size, the sensitivity of the specified carrier sense is lowered (the threshold is raised) to be less than 1 hop, or the specified carrier sense is omitted (S9), Data transfer processing to the terminal device is performed (S7). As a result, simultaneous transmission can be performed between adjacent terminal devices without performing transfer standby in the first embodiment.

FIG. 6 shows a control example of the second embodiment of the present invention. The terminal devices A to E are the same as the arrangement used in the description of the first embodiment.
In FIG. 6, when data crossing (1) is detected in the adjacent terminal devices C and D, and the crossed data has the same data size, the carrier specified by both the adjacent terminal devices C and D at the timing t2. Decrease the sensitivity of the sense (increase the threshold value) to make it less than 1 hop, or omit the specified carrier sense and transmit the data D1 and D2 simultaneously, respectively. In the subsequent data transfer, the data transfer is performed by returning to the prescribed carrier sense in which the detectable range of carrier sense is 2 hops.

A, B, C, D, E Terminal device 11 Wireless transmission / reception unit 12 Wireless interface unit 13 Transmission / reception control unit 14 Routing control unit 15 Data storage unit 16 Data format processing unit 17 Data input / output unit

Claims (6)

In a multi-hop wireless communication system in which a plurality of terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path, respectively.
The terminal device receives the data 1 from an adjacent terminal device in the data transfer path, detects a data intersection in which the data 2 is transmitted to the adjacent terminal device immediately before or immediately thereafter, and further detects the specified data After detecting data transmission from the adjacent terminal device to the next terminal device by carrier sense and subsequent busy by ACK, before transmitting the data 1, the sensitivity of the specified carrier sense is lowered and one hop ahead And a control means for transmitting the data 1 with a carrier sense start timing delayed from the prescribed carrier sense and performing the prescribed carrier sense in subsequent data transmission. Hop wireless communication system. In a multi-hop wireless communication system in which a plurality of terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path, respectively.
The terminal device, after receiving the data 1 from an adjacent terminal, and detects a data interleaving for transmitting the data 2 to the terminal device that the adjacent immediately before or immediately after the previous SL data transfer path, said data if 1 and the data 2 are the same data size, either a detectable to less than one hop lower the sensitivity of the carrier sense of the provisions before transmitting the data 1, or to omit the carrier sense of the defining Thus , the multi-hop wireless communication is characterized in that the data 1 is transmitted simultaneously with the transmission of the data 2 by the adjacent terminal device, and the control means for performing the prescribed carrier sense in the subsequent data transmission is provided. system. In a multi-hop wireless communication method in which multiple terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path,
The terminal device
Receiving the data 1 from an adjacent terminal device in the data transfer path, and detecting a data crossing in which the data 2 is transmitted to the adjacent terminal device immediately before or immediately after the data transfer route;
After detecting the data crossing, detecting data transmission from the adjacent terminal device to the subsequent terminal device by the prescribed carrier sense and subsequent busy by ACK,
Before transmitting the data 1 after detecting the busy, the sensitivity of the specified carrier sense is lowered to enable detection up to one hop ahead, and the carrier sense start timing is delayed from the specified carrier sense. Sending data 1;
The data transmission after the transmission of the data 1 includes the step of performing the prescribed carrier sense. In a multi-hop wireless communication method in which multiple terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path,
The terminal device,
Receiving the data 1 from an adjacent terminal device in the data transfer path, and detecting a data crossing in which the data 2 is transmitted to the adjacent terminal device immediately before or immediately after the data transfer route;
Determining whether or not the data 1 and the data 2 have the same data size; and if the data 1 and the data 2 have the same data size, the data 1 is transmitted after the data crossing is detected before either can be detected to less than one hop lower the sensitivity of the carrier sense of the provision or by omitting the carrier sense of the provisions, the transmission of the data 1 by the adjacent terminal data 2 To be performed simultaneously with sending
The data transmission after the transmission of the data 1 includes the step of performing the prescribed carrier sense. In a terminal device of a multi-hop wireless communication system, in which a plurality of terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path. ,
Receiving the data 1 from the adjacent terminal device in the data transfer path, detecting data crossing in which the data 2 is transmitted to the adjacent terminal device immediately before or immediately thereafter, and detecting the adjacent data by the specified carrier sense After detecting data transmission from the terminal device to the subsequent terminal device and subsequent busy due to ACK, before transmitting the data 1, the sensitivity of the specified carrier sense is lowered to enable detection up to one hop ahead, And a control means for transmitting the data 1 with a carrier sense start timing delayed from the specified carrier sense, and performing the specified carrier sense in subsequent data transmission. Terminal device. In a terminal device of a multi-hop wireless communication system, in which a plurality of terminal devices perform multi-hop transfer of different data 1 and data 2 in opposite directions while performing a prescribed carrier sense that can be detected up to two hops in the data transfer path. ,
After detecting the pre SL receives the data 1 from an adjacent terminal in the data transfer path, the data interleaving for transmitting the data 2 to the terminal device that the adjacent immediately before or immediately after, the data 1 and the data 2 Are the same data size, the sensitivity of the specified carrier sense is lowered before transmission of the data 1 to enable detection to less than 1 hop, or the specified carrier sense is omitted , so that the data the first transmission is performed simultaneously with the transmission of the data 2 by the adjacent terminal apparatus, the terminal apparatus of a multi-hop wireless communication system comprising the control means for performing carrier sense of the provisions in the subsequent data transmission.

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