  Random Access MAC protocols are simple and effective when the nature of the
traffic is unpredictable and sporadic. In the following paper, investigations
on the new Enhanced Contention Resolution ALOHA (ECRA) are presented, where
some new aspects of the protocol are investigated. Mathematical derivation and
numerical evaluation of the symbol interference probability after SIC are here
provided. Results of the optimum header positioning which is found to be in the
beginning and in the end of the packets, are exploited for the evaluation of
ECRA throughput and Packet Error Rate (PER) under imperfect knowledge of
packets positions. Remarkable gains in the maximum throughput are observed for
ECRA w.r.t. Contention Resolution ALOHA (CRA) under this assumption.
