An opportunistic MAC protocol for multiple code channels DS-CDMA wireless networks

Abstract

We propose a contention based medium access control (MAC) protocol which will extend traditional single channel wireless network such as IEEE 802.11 distributed coordination function (DCF) to be used in multiple code channels direct sequence code division multiple access (DS-CDMA) wireless networks. The DCF is a special case in our proposed MAC protocol. We assume the system exist a maximum allowable simultaneously transmissions M which is dependent on the degree of multiple access interference (MAI). To control the access of multiple code channels in DS-CDMA wireless network, we define the channel regulation (CR) which is smaller than M and three channel states which are random access (RA) state, CR state and busy state respectively. The channel is in RA state, CR state and busy state whenever simultaneously transmissions are smaller than CR, between CR and M and larger than M respectively. Nodes can randomly access channel whenever they detect RA state and do p-persistent transmission while CR state is detected. If channel is detected in busy state, nodes have to run backoff algorithm to prepare next time of transmission. The simulation results show that the proposed MAC protocol algorithm performs very well.