OFDM-MFSK as a Special Case of Noncoherent Communication Based on Subspaces

The combination of OFDM and FSK leads to attractive wireless transmission methods for fast time-varying channels because no channel knowledge is required in the receiver. Their drawback is the moderate or bad bandwidth efficiency. We show in this paper that OFDMMFSK and its multitone variant are special cases of more general methods which use vector subspaces for transmission and which are commonly discussed in MIMO context. Beside a better theoretical understanding this opens a window for future work with the goal to increase the bandwidth efficiency of OFDM-MFSK while keeping its robustness with respect to fast time-varying wireless channels.