Method for industrial wireless communication based on self-adaptive channel hopping within the timeslot

• US 8,228,859 B2
• Filed: 09/04/2009
• Issued: 07/24/2012
• Est. Priority Date: 09/11/2008
• Status: Active Grant

• Current Assignee: Chongqing University of Posts and Telecommunications (Chongqing Education Commission)
• Original Assignee: Chongqing University of Posts and Telecommunications (Chongqing Education Commission)
• Inventors: Wang, Ping, Wang, Quan
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Hyun, Soon-Dong
• Application Number:
  US12/554,064
• Publication Number:
  US 20100061362A1
• Time in Patent Office: 1,054 Days
• Field of Search: None
• US Class Current: 370/329
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 1/74 for increasing reliability, e.g. using redundant or spare channels or apparatus replacing by standby devices for amplifiers H03F1/52, H03F1/542
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

The present invention is intended to protect an industrial wireless communication method based on self-adaptive channel hopping within timeslot, which belongs to industrial wireless communication technology field. Aiming to solving existing problem that wireless devices can not correspondingly self-adaptive channel hopping according to environment changing, a method for making the two communication sides self-generate and execute channel switch when the preferred channel was interfered. The sender will monitor whether the channel is idle within SWTW before sending data through mechanisms such as CCA or non-persistent CSMA. If the channel is still busy till the SWTW times out, the sender will give up sending data and implement channel switching control command by considering this communications channel as interfered. If no packets were received till the RWTW time-outs, the receiver will thinks the communication channel was interfered and automatically implement channel switching control commands. Thus, the receiver will change its backup channel into communication channel. So far, the sender and receiver all independently hop to the backup channel for new communication process after a channel switching cycle. Different time synchronization algorithm will be used in accordance with whether channel switch is carried out or not. The present invention can fully enhance the channel utilization and communication success rate, improve the reliability and real-time of data communication, reduce additional network load by means of reduced retransmission, and perfectly satisfy the requirement of industrial wireless application.

Claims

1. An industrial wireless communication method based on Self-Adaptive Channel Hopping within Timeslot (SACHT), the method comprising:

assigning two communication channels including a preferred channel and a backup channel to each communication link within one time slot, the length of Send Waiting Time Window (SWTW) and Receive Waiting Time Window (RWTW) for communication are negotiated and defined before starting; and

selecting the preferred channel as a communication channel at the beginning of a given time slot,

wherein if the preferred channel is interfered, a sender does not send a message due to detecting the preferred channel interfered within the SWTW, and a receiver does not receive an expected message within the RWTW, a channel switching control command being generated and implemented respectively by the sender and the receiver, and then the sender and the receiver communicating on the backup channel.

2. The industrial wireless communication method as recited in claim 1, wherein the sender re-detect whether the backup channel is interfered or not within a second SWTW after channel switch, and the sender gives up this time slot communication if the backup channel is also interfered.

3. An industrial wireless communication method based on Self-Adaptive Channel Hopping within Timeslot (SACHT), the method comprising:

assigning more than two communication channels including a preferred channel and a backup channels to each communication link within one time slot, the length of Send Waiting Time Window (SWTW) and Receive Waiting Time Window (RWTW) for communication are negotiated and defined before starting; and

selecting the preferred channel as a communication channel at the beginning of a given time slot,

if the preferred channel is interfered, a sender does not send message due to detecting the preferred channel interfered within the SWTW, and the receiver does not receive expected message within the RWTW, a channel switching control command being generated and implemented by the sender and the receiver, and the sender and the receiver communicating on the backup channel,

if a former backup channel is interfered, the sender and the receiver switch to a later backup channel for communication.

4. The industrial wireless communication method as recited in claim 3, further comprising:

defining and fixing the length of a time slot (specified by T_Slot ), Value of sending offset 1 (specified by T^TxOffset ), and Value of sending offset 2 (specified by T^TxOffset2 ) before starting in the industrial wireless network;

implementing time synchronization with a sender according to a time synchronization equation by a receiver,

wherein if a channel switch does not happen, T_Tx0ffset1is chosen in the time synchronization equation;

if the channel switch happens, T_TxOffset2 will be chosen in the time synchronization equation;

if the sender wants to send packet immediately stead of waiting till the end of the SWTW, the sender marks and adds the T_TxRest in a packet to the receiver;

the receiver extracts the T_TxRest from the packet, and then adds the T^TxRest in the right of the time synchronization equation which is

5. The industrial wireless communication method as recited in claim 4, wherein for a successful channel switch within a time slot, the sender and the receiver of communication take the previous preferred channel as the present backup channel and the previous backup channel as the present preferred channel in future communication time-slots.