In this paper,we rethink delay Doppler channels(also called doubly selective channels).We prove that no modulation schemes(including the current active VOFDM/OTFS)can compensate a non-trivial Doppler spread well.We th...In this paper,we rethink delay Doppler channels(also called doubly selective channels).We prove that no modulation schemes(including the current active VOFDM/OTFS)can compensate a non-trivial Doppler spread well.We then discuss some of the existing methods to deal with time-varying channels,in particular time-frequency(TF)coding in an OFDM system.TF coding is equivalent to space-time coding in the math part.We also summarize state of the art on space-time coding that was an active research topic over a decade ago.展开更多
文摘In this paper,we rethink delay Doppler channels(also called doubly selective channels).We prove that no modulation schemes(including the current active VOFDM/OTFS)can compensate a non-trivial Doppler spread well.We then discuss some of the existing methods to deal with time-varying channels,in particular time-frequency(TF)coding in an OFDM system.TF coding is equivalent to space-time coding in the math part.We also summarize state of the art on space-time coding that was an active research topic over a decade ago.
