Joint hop timing and frequency estimation for collision resolution in FH networks

With the rapid growth of frequency-hopped (FH) wireless networks, interference due to frequency collisions has become one of the main performance-limiting challenges. This paper proposes a novel multiuser detection method for joint hop timing and frequency estimation, which is capable of unraveling and demodulating multiple FH transmissions in the presence of collisions and unknown hop patterns without retransmission. The method is based on the principle of dynamic programming (DP) coupled with two-dimensional harmonic retrieval (2-D HR) or low-rank trilinear decomposition, and it remains operational even with multiple unknown hop rates, frequency offsets, and asynchronism. The model is based on frequency-shift keying (FSK) and phase-shift keying (PSK) modulation, but the algorithms are also evaluated with Gaussian minimum-shift keying (GMSK) modulation and shown to be robust.