Non-Coherent Demapping for Stationary Rayleigh Fading Channels using Semidefinite Programming

In this paper, we consider the problem of detecting a QPSK signal transmitted over a flat-fading channel without using pilot symbols. Instead, our aim is to approximate ML sequence detection, which is a nonconvex and discrete problem. To solve this problem, we use semidefinite relaxation and randomization to find a solution close to optimal. We propose a new solver based on the alternative direction method of multipliers to solve this problem efficiently. To verify this approach, we have developed and implemented a complete communication framework. We thoroughly simulated the conventional scheme using pilot-based channel estimation, as well as our newly proposed method and compared the achieved bit error rates. For high channel dynamics, our approach outperforms the pilo