Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Cross-Layer Design for Medium Access Control in CDMA Ad Hoc Networks | EURASIP Journal on Applied Signal Processing 2005 2 129-143 2005 Hindawi Publishing Corporation Cross-Layer Design for Medium Access Control in CDMA Ad Hoc Networks Amit Butala Qualcomm Inc. San Diego CA 92121 USA Email abutala@ Lang Tong School of Electrical and Computer Engineering Cornell University Ithaca NY 14853 USA Email ltong@ Received 7 August 2003 Revised 3 May 2004 A medium access control MAC protocol for spread-spectrum ad hoc networks with dynamic channel allocation DCA is presented. DCA can support large systems with a smaller number of channels by dynamically assigning channels only when a node has a packet to transmit. The protocol extends cross layer with the scheduling at the MAC and assignment of channels at the physical layer by means of a query. It is shown that DCA is collision free under ideal conditions. By assigning channels dynamically DCA offers improved throughput normalized by available bandwidth. Analytical results are presented for the performance of the query detection and the throughput for a fully connected network. Keywords and phrases MAC dynamic channel allocation spread spectrum query hypothesis detection. 1. INTRODUCTION There are several challenges in the design of medium access control MAC protocol for code division multiple access CDMA ad hoc networks. While it is possible to apply single-channel MAC protocols such as MACAW 1 DBTMA 2 and FAMA 3 to a multichannel CDMA network by treating channels independently such approaches do not exploit the rich diversity of CDMA nor do they offer an efficient utilization of available spectrum. Specifically the classical problem of hidden exposed nodes manifests itself differently in the presence of multiple access channels multiple data channels and a control channel can coexist using different spreading codes. If the spreading codes have good cross-correlation properties contention on one channel does not cause interference on the other channels. The selection
