Cross-Layer Scheduling with QoS Support over a Near-Optimum Distributed Queueing Protocol for Wireless LANS

Cross-Layer Scheduling with QoS Support over a Near-Optimum Distributed Queueing Protocol for Wireless LANS

E. Kartsakli (Signal Theory and Communications Department, Technical University of Catalonia (UPC), Spain), J. Alonso-Zárate (Telecommunications Technological Centre of Catalonia (CTTC), Spain), L. Alonso (Signal Theory and Communications Department, Technical University of Catalonia (UPC), Spain) and C. Verikoukis (Telecommunications Technological Centre of Catalonia (CTTC), Spain)
DOI: 10.4018/978-1-61520-771-8.ch002
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Abstract

Distributed Queueing Collision Avoidance (DQCA) is an efficient MAC protocol designed for infrastructure Wireless LANs. In this chapter, a thorough description of the protocol is given, along with a set of protocol rules and an example of its operation. In continuation, four algorithms are proposed that alter the FIFO scheduling order of DQCA in order to meet specific network requirements. The proposed schemes combine the efficiency of opportunistic scheduling with the QoS provisioning through service differentiation. The opportunistic policy encourages transmissions at higher rates when the channel condition is good and is implemented through a cross-layer dialogue between the PHY and the MAC layers. The key idea of service differentiation is to assign priorities to traffic flows with different requirements in order to provide QoS guarantees. The throughput, delay and jitter performance of the proposed schemes have been evaluated through simulations for a scenario with heterogeneous traffic of voice, video, best-effort and background data traffic flows.
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Background

Advances in the physical layer have led to a significant capacity increase in WLANs. The widely deployed IEEE 802.11g standard (IEEE Std. 802.11g, 2003), for example, defines a set of eight rates ranging from 6 to 54 Mbps and the emerging IEEE 802.11n standard promises rates beyond 100Mbps (IEEE Std 802.11n, 2008). Lower rates are more robust to channel noise whereas higher ones require larger signal-to-noise ratio (SNR) values over the wireless link.

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