Browsing by Subject "IEEE 802.11 DCF"

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Open Access
An analysis of IEEE 802.11 DCF and its application to energy-efficient relaying in multihop wireless networks
(IEEE, 2010-12-17) Aydogdu, C.; Karasan, E.
We present an analytical model for the IEEE 802.11 DCF in multihop wireless networks that considers hidden terminals and accurately works for a large range of traffic loads. An energy model, which considers energy consumption due to collisions, retransmissions, exponential backoff and freezing mechanisms, and overhearing of nodes, and the proposed IEEE 802.11 DCF analytical model are used to analyze the energy consumption of various relaying strategies. The results show that the energy-efficient relaying strategy depends significantly on the traffic load. Under light traffic, energy spent during idle mode dominates, making any relaying strategy nearly optimal. Under moderate traffic, energy spent during idle and receive modes dominates and multihop transmissions become more advantageous where the optimal hop number varies with processing power consumed at relay nodes. Under very heavy traffic, where multihopping becomes unstable due to increased collisions, direct transmission becomes more energy efficient. The choice of relaying strategy is observed to affect energy efficiency more for large and homogeneous networks where it is beneficial to use multiple short hops each covering similar distances. The results indicate that a cross-layered relaying approach, which dynamically changes the relaying strategy, can substantially save energy as the network traffic load changes in time.
Open Access
An analytical model of IEEE 80211 DCF for multi-hop wireless networks and its application to goodput and energy analysis
(2010) Aydoğdu, Canan
In this thesis, we present an analytical model for the IEEE 802.11 DCF in multihop networks that considers hidden terminals and works for a large range of traffic loads. A goodput model which considers rate reduction due to collisions, retransmissions and hidden terminals, and an energy model, which considers energy consumption due to collisions, retransmissions, exponential backoff and freezing mechanisms, and overhearing of nodes, are proposed and used to analyze the goodput and energy performance of various routing strategies in IEEE 802.11 DCF based multi-hop wireless networks. Moreover, an adaptive routing algorithm which determines the optimum routing strategy adaptively according to the network and traffic conditions is suggested. Viewed from goodput aspect the results are as follows: Under light traf- fic, arrival rate of packets is dominant, making any routing strategy equivalently optimum. Under moderate traffic, concurrent transmissions dominate and multihop transmissions become more advantageous. At heavy traffic, multi-hoppingbecomes unstable due to increased packet collisions and excessive traffic congestion, and direct transmission increases goodput. From a throughput aspect, it is shown that throughput is topology dependent rather than traffic load dependent, and multi-hopping is optimum for large networks whereas direct transmissions may increase the throughput for small networks. Viewed from energy aspect similar results are obtained: Under light traf- fic, energy spent during idle mode dominates in the energy model, making any routing strategy nearly optimum. Under moderate traffic, energy spent during idle and receive modes dominates and multi-hop transmissions become more advantageous as the optimum hop number varies with processing power consumed at intermediate nodes. At the very heavy traffic conditions, multi-hopping becomes unstable due to increased collisions and direct transmission becomes more energy-efficient.The choice of hop-count in routing strategy is observed to affect energyefficiency and goodput more for large and homogeneous networks where it is possible to use shorter hops each covering similar distances. The results indicate that a cross-layer routing approach, which takes energy expenditure due to MAC contentions into account and dynamically changes the routing strategy according to the network traffic load, can increase goodput by at least 18% and save energy by at least 21% in a realistic wireless network where the network traffic load changes in time. The goodput gain increases up to 222% and energy saving up to 68% for denser networks where multi-hopping with much shorter hops becomes possible.
Open Access
Goodput and throughput comparison of single-hop and multi-hop routing for IEEE 802.11 DCF-based wireless networks under hidden terminal existence
(John Wiley and Sons Ltd, 2016) Aydogdu, C.; Karasan, E.
We investigate how multi-hop routing affects the goodput and throughput performances of IEEE 802.11 distributed coordination function-based wireless networks compared with direct transmission (single hopping), when medium access control dynamics such as carrier sensing, collisions, retransmissions, and exponential backoff are taken into account under hidden terminal presence. We propose a semi-Markov chain-based goodput and throughput model for IEEE 802.11-based wireless networks, which works accurately with both multi-hopping and single hopping for different network topologies and over a large range of traffic loads. Results show that, under light traffic, there is little benefit of parallel transmissions and both single-hop and multi-hop routing achieve the same end-to-end goodput. Under moderate traffic, concurrent transmissions are favorable as multi-hopping improves the goodput up to 730% with respect to single hopping for dense networks. At heavy traffic, multi-hopping becomes unstable because of increased packet collisions and network congestion, and single-hopping achieves higher network layer goodput compared with multi-hop routing. As for the link layer throughput is concerned, multi-hopping increases throughput 75 times for large networks, whereas single hopping may become advantageous for small networks. The results point out that the end-to-end goodput can be improved by adaptively switching between single hopping and multi-hopping according to the traffic load and topology. Copyright © 2015 John Wiley & Sons, Ltd.