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Interclass Collision Protection for IEEE 802.11e Wireless LANs
조운선,이채영 에스케이텔레콤 (주) 2009 Telecommunications Review Vol.19 No.6
Distributed Coordination Function (DCF) in IEEE 802.11 and Enhanced Distributed Channel Access (EDCA) in IEEE 802.11e are contention-based access mechanism in wireless LAN. Both DCF and EDCA reduce collisions based on Inter-Frame Space (IFS) and backoff mechanisms. However, collisions are unavoidable even with the two mechanisms. Especially, in the EDCA, collisions can be classified into interclass and intra-class collision. To eliminate interclass collision in wireless LAN, we propose an Interclass Collision Protection (ICP) scheme by employing Collision Protection Period (CPP) after backoff. Different number of backoff time-slots is inserted to each class. Higher class stations are allowed to transmit before lower class stations end backoff period. Analysis is performed with one dimensional discrete-time markov chain for the EDCA and proposed ICP-based EDCA. Collision probability and throughput of each channel access is examined. Throughput increase is more than doubled with reduced collision probability when the system is saturated.