Capacity Analysis for CDMA Based Cellular and Ad hoc Co-existence Networks

Abstract

The cellular and ad hoc co-existence network is expected as a complete solution for the wireless networks in the future. Traditionally, it is believed that under light traffic conditions, the low cost ad-hoc systems are preferred because of its dynamic feature and flexibility. The packets can be rapidly and directly transmitted to the intended nodes without the need of the centralized administration and infrastructure. On the contrary, if the traffic loading is heavy, frequent contention and collision on the MAC layer will seriously degrade the performance of the ad-hoc systems. Therefore, a centrally controlled architecture is necessary in large covered and densely populated districts. However, different from the conventional RTS/CTS mechanism, CDMA based ad-hoc systems are capable of the multipacket reception. The capacity tradeoffs between the CDMA based cellular and the ad-hoc networks not only monotonously depend on the traffic loading but also the cellular to ad hoc coverage ratio. In this paper, those tradeoffs are investigated. The throughput evaluation and an active defense against the multiple access interference in ad-hoc systems are also provided.