Threshold-less mobile-driven handoff method for cellular systems using unlicensed spectrum
In wireless networks where multiple base stations are deployed, handsets may handoff from one base station to the other while in a voice call. In this disclosure a layer-2 hand-off mechanism for cellular systems designed to operate in unlicensed spectrum is described. More specifically a proposed method that does not use any pre-determined thresholds to initiate the hand-offs is disclosed.
1. A threshold-less method for mobile node handset handoff between channels of multiple base stations having a medium access control protocol used for forwarding Internet Protocol packets between multiple base stations and mobile nodes in voice over the Internet protocol systems on a wireless network comprising:
multiple base stations in electrical communication with the Internet;
said multiple base stations having channels;
one or more mobile nodes in wireless electrical communication with one of said multiple base stations over said channels;
said multiple base stations and said one or more mobile nodes each having a medium access control protocol;
each of said multiple base stations transmitting a beacon signal;
said beacon signal containing information regarding current Signal to Interference-plus-Noise Ratio, uplink interference, and channel capacity for each of said channels;
said one or more mobile nodes scanning said beacon signal and storing said information regarding current Signal to Interference-plus-Noise Ratio for each of said channels;
said one or more mobile nodes averaging said Signal to Interference-plus-Noise Ratio from multiple scans to determine an average Signal to Interference-plus-Noise Ratio;
each of said one or more mobile nodes storing said average Signal to Interference-plus-Noise Ratio for a channel it is communicating over and determining a preferred channel list that contains a list of channels that have the best average Signal to Interference-plus-Noise Ratio; and,
wherein when one of said one or more mobile nodes determines that the average Signal to Interference-plus-Noise Ratio of a new channel is better by a set amount than the average Signal to Interference-plus-Noise Ratio of said channel said mobile node is communicating with said mobile node hands off to said new channel if said uplink interference and channel capacity of said new channel allow handoff.
2. The threshold-less method for mobile node handset handoff between channels of multiple base stations of claim 1 wherein if the average Signal to Interference-plus-Noise Ratio of said channel said mobile node is communicating with is over a set level said mobile node does not handoff to said new channel.
3. The threshold-less method for mobile node handset handoff between channels of multiple base stations of claim 1 wherein Packet Error Rate and Received Signal Strength Indicator are also included in the information of said beacon and stored in said one or more mobile node such that if the average Signal to Interference-plus-Noise Ratio of said new channel and a second new channel are close in value said stored Packet Error Rate and Received Signal Strength Indicator can also be used to determine which channel said mobile node will select for handoff.
4. The threshold-less method for mobile node handset handoff between channels of multiple base stations of claim 1 wherein proactive scanning of said beacons is used by said one or more mobile nodes when said one or more mobile node are in an active communication with said multiple base stations transferring voice or data
5. The threshold-less method for mobile node handset handoff between channels of multiple base stations of claim 1 wherein once said new channel is selected for handoff a set period of time must pass with the average Signal to Interference-plus-Noise Ratio of said new channel, continuing to be better by a set amount than the average Signal to Interference-plus-Noise Ratio of said channel said mobile node is communicating with to allow handoff if said uplink interference and channel capacity of said new channel still allow handoff.