Erasure Insertion for Coded DUSTM-FHSS Systems without A Priori Knowledge

In this paper, we consider coded frequency-hopping spread spectrum (FHSS) systems with differential unitary space-time modulation (DUSTM). We investigate the erasure insertion (EI) techniques for improving the decoding error probability, especially in presence of strong partial-band interference (PBI). Conditional likelihood functions are derived for the decision-feedback demodulation and used for EI. The two proposed erasure rules do not require knowledge of the distribution of the noise plus interference power, in contrast to their counterparts in [14]. Instead of assuming the unknown parameters involved in decision-feedback demodulation and EI to be known, a joint estimation-demodulation scheme based on the adaptive recursive least square (RLS) algorithm is proposed. The sensitivity of the proposed EI rules to mismatched thresholds is studied by simulation. Numerical results show that EI can improve the decoding error probability significantly in presence of PBI, even when the required parameters have to be estimated and suboptimal thresholds are used.