Analog Transmission of Correlated Sources in SIMO MAC using Hexagonal Lattices

We address the transmission of correlated sources over the fading single-input and multiple-output (SIMO) multiple access channel (MAC) using an analog joint sourcechannel coding (JSCC) mapping based on hexagonal lattices. The complex-valued source symbols are individually encoded at each user from the points defined by the generator matrix of the hexagonal lattice. Then, the encoded symbols are sent to a receiver node which is equipped with multiple antennas. At the receiver, the correlation between the user symbols is exploited by joint decoding of the information received from all users with the minimum mean squared error (MMSE) estimator. However, the huge computational cost of the decoding operation would make the proposed system impractical, even for a small number of users. A sphere decoder is also employed to simplify the required search in the lattice space, lowering the overall complexity of the system. The obtained results show that the proposed scheme provides a certain gain with respect to the existing schemes based on modulo functions for the same scenario.