Browsing by Author "Kannan, Lakshmi Narasimhan, 1984-"
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Item Ad Hoc 802.11b cooperative protocols: performance in a slow fading channel(The University of Texas at Dallas, 2013-05-24) Agarwal, Niraj, 1977-; ChanneGowda, Divya, 1981-; Kannan, Lakshmi Narasimhan, 1984-; Tacca, Marco, 1973-; Fumagalli, Andrea; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.This paper investigates the use of cooperative communications in the context of ad hoc IEEE 802.11b to combat radio signal degradations due to slow fading. The performance gain of both an existing cooperative protocol and the one proposed in the paper is discussed. It is quantitatively shown how much the two cooperative protocols increase throughput, lower delivery latency, and extend transmission span, when compared to the conventional IEEE 802.11b protocol. These features may help improve connectivity and network performance in ad hoc applications, where nodes’ relative locations are difficult to control and predict.Item An analytical model with improved accuracy of IEEE 802.11 protocol under unsaturated conditions(The University of Texas at Dallas, 2013-05-23) Vijayasankar, Kumaran, 1984-; Taufique, Azar; Kannan, Lakshmi Narasimhan, 1984-; Tacca, Marco, 1973-; Fumagalli, Andrea; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.In this work the authors present an analytical model that - compared to previously published work- more accurately captures the delay of IEEE 802.11 protocol under low, medium, and near-saturation load conditions. A Markov chain is used to keep track of the instantaneous number of (active) nodes that have a frame to transmit. The number of active nodes varies over time and is a function of various parameters, including the frame individual maximum retransmission count. One advantage of the proposed analytical model is its ability to estimate the IEEE 802.11 protocol latency and delivery ratio in the presence of quality of service (QoS) classes, each class being defined by a specific maximum retransmission count. Such QoS classes can be adopted to support real time applications for which both latency and delivery ratio must be closely monitored for satisfactory operation. The analytical estimation of these performance parameters may offer useful feedback to admission control schemes.Item Combining cooperative link layer protocols with distributed routing protocols in mobile ad hoc networks – perspectives and performance analysis(The University of Texas at Dallas, 2013-06-18) Vijayasankar, Kumaran, 1984-; Kannan, Lakshmi Narasimhan, 1984-; Ilango, Sathya; Tacca, Marco, 1973-; Fumagalli, Andrea; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.In cooperative link layer protocols the use of relay nodes may increase the capacity of the radio links. The study in this paper investigates what (if any) performance gain may be passed onto the routing protocol of a mobile ad hoc network. Two popular routing protocols are considered, AODV and OLSR, as each provides a unique route acquisition mechanism. A distributed procedure to choose the relay node at the link layer is combined with the two routing protocols. Analysis via simulation confirms some expected (and perhaps some other less expected) benefits when using a cooperative link layer protocol in place of a non-cooperative one, e.g., improved delivery ratio, end-to-end delay, and reduced signaling overhead.Item Cooperative communications in multihop networking: a case study based on the IEEE 802.11 protocol(The University of Texas at Dallas, 2013-05-24) Kannan, Lakshmi Narasimhan, 1984-; Vijayasankar, Kumaran, 1984-; ChanneGowda, Divya, 1981-; Agarwal, Niraj, 1977-; Fumagalli, Andrea; Tacca, Marco, 1973-; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.This paper combines multi-hop networking with single-hop cooperative communications. The solution is built upon the standard IEEE 802.11 protocol operating in the ad hoc mode. A simulation based comparison is carried out in order to evaluate the performance gains and benefit of cooperative communications applied to multi-hop networking. Preliminary results indicate that network performance in terms of both throughput and end-to-end delay improves. Additionally, cooperative communications increases robustness against uncertainties in the wireless channel.Item A cross layer routing metric with wireless cooperative protocols(The University of Texas at Dallas, 2013-06-18) Vijayasankar, Kumaran, 1984-; Kannan, Lakshmi Narasimhan, 1984-; Tacca, Marco, 1973-; Fumagalli, Andrea; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.Cooperative link layer protocols are typically used in single hop networks. In such protocols, a special node called the relay node helps deliver frames from a source to a destination. The performance benefits of cooperation at link layer can be streamlined into multi-hop networks as well. In multi-hop networks, a frame is sent from an original source to the final destination through a series of intermediate nodes. The paper extends the expected transmission time metric — proposed for multi-hop wireless ad hoc networks — to the context of cooperative IEEE 802.11 link layer protocol. The designed metric is called cooperative expected transmission time (CETT). CETT carefully accounts for the higher probability of successful frame transmission and therefore the reduction in expected transmission time brought about by the relay node in the cooperative protocol. CETT jointly optimizes both the route computation and the selection of the cooperative relay at the link layer. Route optimization helps jointly choose the best set of intermediate nodes and cooperation optimization helps choose the best relay node for each link in the multi-hop. As a result, CETT helps distinguish the case wherein it is better to use a node as a relay as compared to using it as an intermediate node. For comparison, the case where cooperation is applied after route computation is also presented. Minimizing the expected transmission time may result in more efficient link utilization and increased overall end-to-end network throughput. It is also shown that joint optimization of route and relay selection is better than finding routes and then applying cooperation.