Capacity bounds and performance of precoder index modulation

Abstract

Precoder index modulation (PIM) is a recently proposed transmission scheme in which the index of the chosen precoder matrix from a set of predetermined pseudo-random phase precoder (PRPP) matrices will also convey information bits in addition to the information bits conveyed through conventional modulation symbols. In this paper, first we derive lower and upper bounds on the capacity of PIM. Second, since the optimum PIM detection has an exponential complexity in the precoder size, we propose a low complexity message passing based detection algorithm suited for large precoder sizes. Simulation results show that PIM with a precoder matrix of size 150 × 150 and BPSK achieves a BER of 10^-5 at an SNR of about 10 dB using the proposed detection algorithm in flat Rayleigh fading channels. Third, we also propose an enhanced PIM (E-PIM) scheme which provides additional signaling support to the index bits, but without loosing spectral efficiency compared to PIM. Simulation results show that the proposed E-PIM scheme achieves better performance compared to PIM.