Detection of colliding users in OFDM based Random Access Networks

Whenever there is a collision involving several transmitted packets, the traditional approach for MAC (Medium Access Control) protocols is to discard all packets involved and request their retransmission, with a consequent loss in the overall throughput. Based on conventional Multiple Input Multiple Output (MIMO) techniques, a multipacket detector for OFDM schemes (Orthogonal Frequency Division Multiplexing) which does not discard the packets involved in a collision has been recently proposed. One of the major problems in resolving collisions using the multipacket detector is to discover how many and which users were transmitting. In this paper we will present a method to solve this problem.