METHOD FOR INDUSTRIAL WIRELESS COMMUNICATION BASED ON SELF-ADAPTIVE CHANNEL HOPPING WITHIN THE TIMESLOT

• US 20100061362A1
• Filed: 09/04/2009
• Published: 03/11/2010
• 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, Quan, Wang, Ping
• Granted Patent: US 8,228,859 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• 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), wherein two communication channels, in which one is the preferred channel and the other is the backup channel, are assigned 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. At the beginning of a given time slot, the sender and the receiver firstly select the preferred channel as communication channel. If the preferred channel is interfered, the sender will not send message due to detecting the preferred channel interfered within its SWTW, and the receiver will not receive its expected message within RWTW, thus a channel switching control command will be generated and implemented respectively by both sides themselves, and then both sides will all try to communicate on their 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 its second SWTW after channel switch, and it will give up this time slot communication if the backup channel is also interfered.

3. The industrial wireless communication method as recited in claim 1, wherein more than two communication channels, in which one is the preferred channel and the others are the backup channels, are assigned to each communication link within one time slot. If former backup channel is interfered, both sides of communication can switch to later backup channel for communication.

4. The industrial wireless communication method as recited in claim 3, wherein the time synchronization method is that:

In this kind of industrial wireless network, length of a time slot (specified by T_Slot), Value of sending offset 1 (specified by T_Txoffset1), and Value of sending offset 2 (specified by T_Txoffset2) are all defined and fixed before starting. The receiver can implement time synchronization with its sender according to Eq. 1. If channel switch does not happen, then T_TxOffset1 will be chosen in the time synchronization equation. If channel switch happened, then T_TxOffset2 will be chosen in the time synchronization equation. If channel switch does not happen, the T_TxOffset1 will be chosen in the time synchronization equation. If channel switch happened, the 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 its SWTW, it could mark and add the T_TxRest in its packet to the receiver. The receiver could extract the T_TxRest from the packet, and then add the T_TxRest in the right of the Eq. 1.

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