JP6413339B2 - Wireless communication apparatus and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a wireless communication system, and can be applied to, for example, a wireless communication system applying CSMA / CA (Carrier Sense Multiple Access Collision Avidance).

  In a wireless communication system using CSMA / CA, backoff control is performed in order to reduce the probability of frame transmission collision.

  The backoff is to insert a random delay before frame transmission and carrier sense (hereinafter also referred to as “CCA”). Carrier sense here includes, in addition to the original meaning, determining whether or not the RSSI (Received Signal Strength Indication) value is equal to or greater than a threshold value, and if it is equal to or greater than the threshold value, also includes stopping frame transmission as carrier detection. .

  In the back-off scheme compliant with the IEEE 802.15.4 (Non-Patent Document 1) standard, the wireless communication apparatus performs CCA and performs frame transmission after performing back-off during frame transmission. However, when the carrier is detected, the backoff is performed again, so that the time until frame transmission becomes longer.

  In the back-off method compliant with the IEEE 802.11 standard (Non-Patent Document 2), the wireless communication device continues to perform CCA at all times during the back-off time. When the carrier is detected, the back-off period is extended by the time during which the carrier is detected. Compared to the technique described in Non-Patent Document 1, there is an advantage that a penalty when a carrier is detected can be minimized. However, since it is necessary to always perform CCA, power saving control cannot be performed.

  FIG. 1 is a diagram for explaining a back-off scheme compliant with the international communication standard “WiSUN” for the 920 MHz band specific low-power radio, Profile for EchoNetLite. This back-off method extends the back-off function described in Non-Patent Document 1 and extends the back-off time by the time taken to receive the frame only when reception of the frame is completed during the back-off period. (Hereinafter referred to as “WiSUN extended backoff method”). Compared with the back-off method described in Non-Patent Document 2, this method does not recognize fine noise as a carrier, and therefore has an advantage that the back-off time is not unnecessarily extended (the penalty is small). .

  Further, the WiSUN extended back-off method has an advantage over the case where the back-off method described in Non-Patent Document 2 is applied to the back-off method described in Non-Patent Document 1 as it is. In the back-off method described in Non-Patent Document 1, the minimum RSSI value for frame reception is lower than the RSSI threshold value that CCA recognizes as having a carrier (to increase the sensitivity of frame reception). .

  Therefore, if the back-off method described in Non-Patent Document 2 is applied as it is (in other words, the CCA carrier sense threshold used in the back-off period remains higher than the minimum RSSI value for frame reception), WiSUN extended back-off Compared to the method, there is a higher possibility that other nodes cannot recognize that frames are being transmitted.

IEEE 802.15.4 IEEE 802.11

  However, if the WiSUN extended back-off method is implemented as it is, the code for realizing the function becomes complicated. For example, the wireless communication apparatus normally receives only a frame addressed to itself, but when implementing the back-off function in the WiSUN specification, it is necessary to change the setting so that all frames are received only when the back-off is performed. Further, since the frame reception state is monitored at the time of backoff, it is necessary to connect the frame reception unit and the backoff / CCA processing unit, but this is technically difficult.

  Also, when the back-off period ends during frame reception, the CCA, which is the next process, always detects the carrier and back-off again.

  However, in a wireless communication device, it is easy to detect completion of frame reception based on frame reception processing, but it is difficult to detect that a frame is being received because the function is not implemented in a normal wireless communication device. It is.

  Therefore, a wireless communication device and a wireless communication system that can avoid unnecessary carrier sense and re-backoff processing in backoff processing are desired.

In the first aspect of the present invention, when the frame reception is completed during the back-off period, in the wireless communication device conforming to Wi-SUN that extends the back-off period, (1) as a basis for estimating that the frame is being received, A frame reception estimation means for estimating that a frame is being received when one or more preset conditions are met, and (2) the frame reception estimation means is receiving a frame during the back-off period. If it can be estimated, it comprises backoff period extending means for extending the backoff period by the frame reception period , and (3) received signal strength acquisition means for acquiring the received signal strength of the incoming radio wave, and (4) receiving the frame The estimation means includes at least the reception signal strength acquired by the reception signal strength acquisition means exceeding a preset threshold, and a preamble reception notification. On the condition that it has received a synchronization signal reception notification, and estimates to be in frame reception.

  A second aspect of the present invention is a wireless communication system comprising a plurality of wireless communication apparatuses, wherein the first aspect of the present invention is applied as a wireless communication apparatus that is a component of the wireless communication system.

  By estimating that the wireless communication apparatus is not only receiving the frame but also receiving the frame, and extending the back-off period by the frame receiving period, unnecessary carrier sense and re-back-off processes can be avoided.

It is explanatory drawing which shows a WiSUN extended backoff system. It is a block diagram which shows the structure of the radio | wireless communication apparatus of 1st Embodiment. It is explanatory drawing which shows the difference in operation | movement of the frame reception estimation part of 1st Embodiment, and a frame reception part. It is explanatory drawing which shows the frame structure used by WiSUN.

(A) 1st Embodiment Below, the 1st Embodiment of the radio | wireless communication apparatus and radio | wireless communications system by this invention is described in full detail, referring drawings.

(A-1) Configuration of First Embodiment FIG. 2 is a block diagram illustrating a configuration of a wireless transmission device according to the first embodiment.

  In FIG. 2, the wireless communication apparatus 100 includes an application unit 101, a frame reception unit 102, a backoff / CCA processing unit 103, a frame transmission unit 104, and a frame reception estimation unit 105.

  The application unit 101 is connected between the frame reception unit 102 and the frame transmission unit 104 and mediates both. The application unit 101 issues a communication processing request to the frame reception unit 102 and the frame transmission unit 104 according to the operation of the application. When the application unit 101 is notified from the frame receiving unit 102 that the frame has been received, the application unit 101 performs processing to extract the received frame.

  The frame reception unit 102 is connected to the application unit 101 and the frame reception estimation unit 105. The frame reception unit 102 discloses to the application unit 101 the frame reception completion and the period required for frame reception. Also, the frame receiving unit 102 discloses the received frame to the application unit 101.

  The back-off / CCA processing unit 103 is connected between the frame reception estimation unit 105 and the frame transmission unit 104 and mediates both.

  The back-off / CCA processing unit 103 performs back-off and CCA control of the WiSUN extended back-off method in response to a communication processing request from the frame transmission unit 104, and notifies the frame transmission unit 104 of the result. Further, when there is a frame reception estimation notification from the frame reception estimation unit 105 during the back-off process, the back-off / CCA processing unit 103 extends the back-off processing time by that period.

  The frame transmission unit 104 is connected to the application unit 101 and the backoff / CCA processing unit 103. When the frame transmission unit 104 receives a frame transmission request from the application unit 101, the frame transmission unit 104 notifies the backoff / CCA processing unit 103 to that effect, and notifies the backoff / CCA processing unit 103 that transmission can be started. In this case, frame transmission is performed.

  The frame reception estimation unit 105 is connected between the back-off / CCA processing unit 103 and the frame reception unit 102, and when it can be estimated that the current frame is received, the back-off / CCA processing unit 103 To notify.

  Although the wireless communication system according to the first embodiment is not shown, at least one wireless communication device 100 having the configuration shown in FIG. 1 and a plurality of wireless communication devices are arranged. Wireless communication is performed between the wireless communication apparatus 100 having the configuration shown and an arbitrary wireless communication apparatus.

(A-2) Operation of First Embodiment Next, an operation related to transmission of the wireless communication apparatus 100 of the first embodiment will be described.

  When there is a frame transmission notification from the application unit 101 to the frame transmission unit 104, the frame transmission unit 104 notifies the backoff / CCA processing unit 103 to that effect.

  The back-off / CCA processing unit 103 extends the back-off time during the period in which it is estimated that the frame reception estimation unit 105 is currently receiving a frame during the back-off period measurement.

  FIG. 3 is an explanatory diagram showing a difference in operation between the frame reception estimation unit 105 and the frame reception unit 102. The frame receiving unit 102 can only notify the completion of reception, but the frame reception estimating unit 105 continuously notifies that it is estimated that the current frame is being received. For example, the frame reception estimation unit 105 estimates that a frame is received in the following case.

  The frame reception estimation unit 105 estimates that a frame is received when the RSSI value is higher than a preset threshold value. Here, as the threshold value to be set, for example, there are an RSSI value for carrier detection in CCA processing, a minimum RSSI value for receiving a frame, and the like. The frame reception estimation unit 105 estimates that a frame is received when the frame reception unit 102 receives a carrier signal. In addition to the RSSI value being higher than the threshold value, the frame reception estimation unit 105 estimates that a frame is received, for example, when there is a preamble detection notification or a synchronization signal discovery notification from the frame reception unit 102. FIG. 4 shows a frame structure used in WiSUN. The WiSUN frame structure includes a preamble (bit synchronization), synchronization information (byte synchronization), a header, a payload, and an FCS. The preamble is a bit string having a preset pattern that is transmitted prior to the data body. The synchronization signal is a signal for timing transmission / reception between the transmission side and reception side wireless communication apparatuses.

  When the back-off / CCA processing unit 103 determines that there is no problem even if frame transmission is performed after the back-off processing and the CCA processing are completed, the back-off / CCA processing unit 103 notifies the frame transmission unit 104 to that effect.

  The frame transmission unit 104 receives the notification from the back-off / CCA processing unit 103 and performs frame transmission.

(A-3) Effect of First Embodiment By having the function of estimating that frames are being received, the WiSUN extended backoff function can be easily realized.

  Furthermore, it is possible to avoid unnecessary CCA and re-backoff processing by estimating that the wireless communication device is not only receiving a frame but also receiving a frame and extending the backoff period by the frame receiving period.

(B) Other Embodiments In addition to the first embodiment, a modified embodiment as exemplified below can be given.

  (B-1) The back-off / CCA processing unit 103 estimates that the frame reception estimation unit 105 is continuously receiving frames for an excessively long period (for example, a period of a preset value or more), and the back-off period If the time becomes sufficiently long, the extension of the back-off period may be interrupted. It is possible to prevent the back-off period from becoming too long.

  (B-2) The wireless communication apparatus and the wireless communication system according to the present invention can be applied not only to the WiSUN extended backoff method but also to a wireless communication device and a wireless communication system that employ a similar backoff method.

  DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus, 101 ... Application part, 102 ... Frame receiving part, 103 ... Back-off and CCA processing part, 104 ... Frame transmission part, 105 ... Frame reception estimation part

Claims (6)

When the frame reception is completed during the back-off period, in the wireless communication device conforming to Wi-SUN that extends the back-off period,
As a basis for estimating that a frame is being received, a frame reception estimation unit that estimates that a frame is being received when one or more preset conditions are met,
When the frame reception estimation means can estimate that the frame is being received during the backoff period, backoff period extension means for extending the backoff period by the frame reception period ;
Receiving signal strength acquisition means for acquiring the received signal strength of the incoming radio wave,
The frame reception estimation means is a frame on the condition that at least the reception signal strength acquired by the reception signal strength acquisition means exceeds a preset threshold and that a preamble reception notification or a synchronization signal reception notification is received. A wireless communication apparatus characterized by estimating that reception is in progress . The wireless communication apparatus according to claim 1 , wherein the threshold value is equal to a threshold value of received signal strength that is determined to be carrier detection. The wireless communication apparatus according to claim 1 , wherein the threshold value is equal to a minimum received signal strength for receiving a frame. The frame receiving estimating means, as one condition that it is receiving a carrier signal continuously, the radio communication apparatus according to any one of claims 1 to 3, characterized in that estimated to be in the frame received . The back-off period extension means, when it becomes more than the threshold value the backoff period is set in advance, the radio communication apparatus according to any one of claims 1 to 4, characterized in that to stop the extension of the back-off period. In a wireless communication system comprising a plurality of wireless communication devices,
The wireless as components to become the wireless communication device of the communication system, a wireless communication system, characterized in that the application of the wireless communication device according to any one of claims 1-5.

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