Multiple symbol differential detection in jammed FH systems

Noncoherent detection is usually applied in frequency hopping (FH) systems, because reliable coherent detection is very difficult. With multiple symbol differential detection (MSDD) a noncoherent system can achieve the performance of coherent differentially encoded systems. Due to its is complexity, two computationally simpler hard-decision feedback algorithms, multiple-symbol based decision-feedback differential detection (MSD DF-DD) and multiple symbol observation interval (MSOI), are studied and compared in partial-band jammed FH system. Additionally the system which uses maximum-a-posteriori (MAP) algorithm as inner decoder is studied and its performance is compared to MSD DF-DD and MSOI. The performance improvement of the MSD DF-DD and MSOI using two simple limiters are also studied. The noniterative versions of MSD DF-DD and MSOI have very similar performance. MSD DF-DD benefits from the iterative processing more effectively than MSOI in jammed and nonjammed simulations. The impact of jamming depends strongly on its bandwidth. The narrower the jamming band is, the more the performance of the algorithms decrease. MAP-based decoding performs significantly better than either of the algorithms