This paper proposed four types of differential modulation to map the unitary code into the orthogonal frequency division multiplexing(OFDM) signal. The time-varying channel model is established and the norm of detecti...This paper proposed four types of differential modulation to map the unitary code into the orthogonal frequency division multiplexing(OFDM) signal. The time-varying channel model is established and the norm of detection metric is deduced. The norm is the inherent interference of the time-varying channel, so it can be used as criterion to evaluate the performance of the mapping schemes. The simulation results agree with the analytic conclusion.展开更多
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This paper proposed four types of differential modulation to map the unitary code into the orthogonal frequency division multiplexing(OFDM) signal. The time-varying channel model is established and the norm of detection metric is deduced. The norm is the inherent interference of the time-varying channel, so it can be used as criterion to evaluate the performance of the mapping schemes. The simulation results agree with the analytic conclusion.
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.
