Hierarchy Schedule Sensing Protocol for CDMA Wireless Networks and Its Performance under Multiple Collision and Capture Effect∗

This paper proposes a new protocol for ad hoc based CDMA wireless local area networks, Hierarchy Schedule Sensing (HSS) protocol. It adopts hierarchical sensing to schedule transmission requests to avoid collisions. Multi-level group spreading codes are used to reduce scheduling delay. The network performance under the HSS protocol is evaluated using a two-dimensional Markov chain model in consideration of collided packets capture effect at receivers. The paper also focuses on the impacts of multiple packet collisions on the performance. A closed formula of the average collision rate is derived explicitly. The results show that the HSS protocol offers a robust performance with low hardware requirement. key words: wireless network, spread spectrum, CDMA, protocol