Linear Frequency Modulation-Based Architecture for SM Systems

In this work, a new architecture using linear frequency modulation (LFM) as an alternative to the conventional fixed carrier frequency version for spatial modulation (SM) systems is proposed. SM signaling allows a new transmission mechanism in MIMO structures where the data and the activated antenna index are sent in a single block. Herein, we propose to exploit LFM to activate either, solely, the pair- or the odd-indexed antennas among the total available number and restrain the antenna index decoding to either pair or odd cases at the LFM chirp detector in the same way, depending on the recognized LFM signal. The objective of the proposed solution, in addition to reduce the research space range of antenna indices, is to lower the indices ambiguity between adjacent antennas, thereby enhancing their estimation. Furthermore, the impacts of channel estimation errors and receive antennas correlation on the performance are investigated for the iterative maximum ratio combiner (i-MRC).