Cooperative random access with long PN spreading codes

Cooperative wireless communication systems have attracted much attention in recent years, due to the diversity advantage they can afford. Existing cooperative transmission modalities have been developed in conjunction with fixed-rate multiplexing based on TDMA, CDMA or FDMA. We advocate user cooperation as the method of choice for enabling diversity in wireless random access networks. The specific protocol developed herein exploits the fact that user cooperation can be viewed as a form of multipath, and capitalizes on the suitability of long pseudo-noise (PN) spreading codes for dealing with multipath channels. Analysis and numerical results confirm that throughput increases considerably when random access via spread-spectrum slotted Aloha protocols is aided by user collaboration.