Last resort frequency mechanism in a wireless communication system
A novel and useful acknowledgement and adaptive frequency hopping mechanism for use in wireless communication systems such as IO-Link Wireless. One or two additional acknowledgement bits are added to packet transmissions. One is a current acknowledgment bit which indicates whether a packet was successfully received anytime during the current cycle. The second bit is a previous acknowledgment bit which indicates whether packets were received successfully anytime during the previous cycle. An adaptive hopping table is constructed using a greedy algorithm which chooses frequencies with the best PER for transmission of higher priority packets, while equalizing the PER products across cycles. A last resort frequency mechanism further improves transmission success by switching to a better performing channel for the last subcycle when previous attempts to transmit a high priority packet have failed.
1. A method of reliable communications between a master and a plurality of devices in a wireless communications network, comprising:
said master and/or at least one of said plurality of devices autonomously hopping to a last resort frequency channel during a communications cycle for receipt of a high priority packet if a last subcycle of a cycle is reached and all previous high priority packet reception attempts were unsuccessful;
wherein said master and/or at least one of said plurality of devices autonomously hopping to said last resort frequency channel does not rely on any communications therebetween within said wireless communications network; and
wherein both said master and said plurality of devices are configured a priori with said last resort frequency channel to be used to transmit high priority packets.
2. The method according to claim 1 , wherein said last resort frequency is selected from a group of best performing frequency channels thereby giving reception of the high priority packet in a last subcycle a relatively high probability of success.
3. The method according to claim 1 , wherein said last resort frequency channel is the frequency channel allocated to a first subcycle in a preceding cycle thereby giving reception of the high priority packet in a last subcycle a relatively high probability of success.
4. The method according to claim 1 , further comprising said master and/or at least one of said plurality of devices hopping to a next frequency channel in an original frequency channel hopping scheme previously configured in said master and said plurality of devices in the event any previous high priority packets were successfully received.
5. The method according to claim 1 , further comprising said master and/or at least one of said plurality of devices hopping to a next frequency channel in a frequency channel table previously configured in said master and said plurality of devices for receipt of a low priority packet in the event any previous high priority packets were successfully received.
6. The method according to claim 1 , wherein said master and/or at least one of said plurality of devices comprise a radio transmitter and a radio receiver configured to conform to the IO-Link Wireless standard.
7. A method of reliable communications between a master and a plurality of devices in a wireless communications network, comprising:
said master and/or at least one of said plurality of devices autonomously hopping to a last resort frequency channel for transmission of a high priority packet if a last subcycle of a cycle is reached, high priority packet retransmissions have been attempted in previous subcycles, and all acknowledgements received as responses to said high priority packet retransmissions indicate unsuccessful transmissions, or if no acknowledgements are successfully received; and
wherein both said master and said plurality of devices are configured a priori with said last resort frequency channel to be used to transmit high priority packets.
8. The method according to claim 7 , wherein said last resort frequency channel is selected from a group of best performing frequency channels thereby giving transmission of the high priority packet in a last subcycle a relatively high probability of success.
9. The method according to claim 7 , wherein said last resort frequency channel is the frequency channel allocated to a first subcycle in a preceding cycle thereby giving transmission of the high priority packet in a last subcycle a relatively high probability of success.
10. The method according to claim 7 , further comprising said master and/or at least one of said plurality of devices otherwise hopping to a next frequency channel in an original frequency channel hopping scheme previously configured in said master and said plurality of devices.
11. The method according to claim 7 , further comprising said master and/or at least one of said plurality of devices otherwise hopping to a next frequency channel in a frequency channel table previously configured in said master and said plurality of devices for transmission of a low priority packet.
12. The method according to claim 7 , wherein said master and said plurality of devices autonomously hopping to said last resort frequency channel does not rely on any communications within said wireless communications network.
13. An apparatus for reliable communications between a master and a plurality of devices in a frequency hopping wireless communications network, comprising:
a frequency hopping radio transmitter;
a frequency hopping radio receiver;
a processor coupled to and operative to control said frequency hopping radio transmitter and said frequency hopping radio receiver;
said processor programmed to autonomously hop to a last resort frequency channel during a communications cycle for receipt of a high priority packet if a last subcycle of a cycle is reached and all previous high priority packet reception attempts were unsuccessful;
wherein said processor autonomously hopping to said last resort frequency channel in said master and/or said plurality of devices does not rely on any communications therebetween within said wireless communications network; and
wherein both said master and said plurality of devices are configured a priori with a last resort frequency channel to be used to transmit high priority packets.
14. The apparatus according to claim 13 , wherein said radio transmitter and said radio receiver are configured to conform to the IO-Link Wireless standard.
15. The apparatus according to claim 13 , wherein said last resort frequency channel is selected from a group of best performing frequency channels thereby giving reception of the high priority packet in a last subcycle a relatively high probability of success.
16. An apparatus for reliable communications between a master and a plurality of devices in a frequency hopping wireless communications network, comprising:
a frequency hopping radio transmitter;
a frequency hopping radio receiver;
a processor coupled to and operative to control said frequency hopping radio transmitter and said frequency hopping radio receiver;
said processor programmed to autonomously hop to said last resort frequency channel for transmission of a high priority packet if a last subcycle of a cycle is reached, high priority packet retransmissions have been attempted in previous subcycles, and all acknowledgements received indicate unsuccessful transmissions, or if no acknowledgements are successfully received; and
wherein both said master and said plurality of devices are configured a priori with a last resort frequency channel to be used to transmit high priority packets.
17. The apparatus according to claim 16 , wherein said radio transmitter and said radio receiver are configured to conform to the IO-Link Wireless standard.
18. The apparatus according to claim 16 , wherein said last resort frequency is selected from a group of best performing frequency channels thereby giving transmission of the high priority packet in a last subcycle a relatively high probability of success.
19. The apparatus according to claim 16 , wherein said last resort frequency channel is the frequency channel allocated to a first subcycle in a preceding cycle thereby giving reception of the high priority packet in a last subcycle a relatively high probability of success.
20. The apparatus according to claim 16 , wherein said master and/or at least one of said plurality of devices hopping to a next frequency channel in a frequency channel table previously configured in said master and said plurality of devices for receipt of a low priority packet in the event any previous high priority packets were successfully received.