Methods and apparatus for reliable point to multipoint communications

Abstract

An advance over the prior art is achieved through an efficient method to retransmit erroneous frames by identifying the users who are most likely to experience a frame error and requests retransmissions from them. Since the recovery is done by starting with the most likely, second most likely etc., the invention results in faster recovery of data. Moreover, the invention reduces the battery consumption of subsequent mobile nodes by suppressing the retransmission requests that were already made by nodes preceding it. A key element of the invention is to rank the set of receiver nodes in the order of decreasingly worse channel conditions, i.e., from worst to best. Hence, with K receiver nodes, a transmit node assigns rank 1 to a receiver node to which it has the poorest radio channel condition. Similarly, it assigns rank K to the receiver node to which it has the best radio channel condition. The channel condition is known at the receiver by keeping a simple measure of the number of data frames correctly received so far and the total number of frames transmitted to it. This information can be periodically sent back to the transmitter and thus aiding in the ranking procedure. Alternatively, if the transmitter is capable of sending a pilot/beacon, the receiver can do some averaging of received signal strength and provide such information back to the transmitter.