Coherent transmission from distributed wireless transmitters

摘要

In one aspect, a distributed coherent transmission system enables transmissions from separate wireless transmitters with independent frequency or clock references to emulate a system where all the transmitters share a common frequency or clock reference. Differences in frequency and/or phase between transmitters are addressed by suitably precoding signals before modulation at one or more of the transmitters based on a synchronizing transmission from one of the transmitters (e.g., a master transmitter) received at a corresponding receiver sharing the frequency or clock reference with each of the one or more transmitters. Such a distributed coherent transmission system can allow N single-antenna transmitters with independent frequency or clock references to emulate a single N-antenna Multi Input Multi Output (MIMO) transmitter, or implement schemes such as distributed superposition coding or lattice codes that require coherence across separate transmitters.

主权项

1. A method for operating a slave transmitter to provide coherent transmission with a master transmitter, the method comprising:
forming a first signal for a data frame for modulation and coherent transmission from the slave transmitter with a transmission of a corresponding signal from the master transmitter; maintaining an estimate of a time-varying phase offset determined from a frequency reference at the slave transmitter and a transmission received at the slave transmitter from the master transmitter; modifying the first signal for the data frame prior to modulation according to a time variation of phase within the data frame determined from the estimate of the time-varying phase offset; and modulating the modified first signal according to the frequency reference at the slave transmitter.