Department of Computer Science and Information Systems
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Item Link Quality Based Path Selection Methods for IEEE 802.16j Mobile Multihop Relay Networks(Springer, 2013-08) Lakshmi, L.R.IEEE 802.16j mobile multihop relay (MMR) networks are developed to enhance the coverage area and the throughput of IEEE 802.16 networks. Path selection is an important research problem related to these networks. In the networks where the link qualities are highly varying, to provide consistent quality of service to the users, it is very important to select paths consisting of links with consistent link qualities. To address this issue, in this paper, two path consistency based path selection methods are proposed for IEEE 802.16j MMR networks. Through simulations, the performance of the method proposed for the mobile nodes is compared with the performance of two path selection methods proposed in the literature. It is observed that the proposed method provides better performance than the methods selected from the literature.Item Cooperative data transmission framework for IEEE 802.16j mobile multihop relay networks(ACM Digital Library, 2014-10) Lakshmi, L.R.IEEE 802.16j Mobile Multihop Relay specification is an amendment of the IEEE 802.16 standard and it is developed to extend IEEE 802.16e. Quality of Service (QoS) constrained service flow management is an important issue related to these networks. In the situation where the link quality between a superordinate station and one of its subordinate Non-Transparent Relay Stations (NTRSs) is poor then it is difficult to fulfill the QoS requirements of the flows that are passing through that NTRS. To handle such situations, in this paper, a novel Cooperative Data Transmission (CDT) framework is proposed. It uses the Transparent Relay Stations (TRSs) which are the common neighbors of the NTRSs and their superordinate stations to fulfill the QoS requirements of the flows that are passing through the NTRSs. The changes required to the network entry, path establishment, bandwidth allocation and data transmission processes of the IEEE 802.16j standard for the CDT framework are proposed in this paper. Also, the performance gains achievable with the proposed CDT framework in terms of the throughput are analyzed numerically. The upper and lower bounds on the throughput gain are obtained. Through simulations, the performance of the proposed CDT framework is studied and compared with the performance of the normal data transmission where no cooperation from TRSs is involved in the data transmission. The CDT framework showed significant performance advantages when compared with the normal data transmission method.Item Handover rate based dynamic guard bandwidth allocation method for call admission control in IEEE 802.16j Mobile Multihop Relay networks(Elsevier, 2014-07) Lakshmi, L.R.IEEE 802.16j MMR (Mobile Multihop Relay) networks are developed to extend the coverage area and enhance the throughput of IEEE 802.16 networks. Call Admission Control (CAC) is an important research issue related to these networks. In this paper, a novel dynamic guard bandwidth allocation method is proposed for CAC in IEEE 802.16j networks; the guard bandwidth allocated at a station depends upon the handover rates from its neighbors and at its descendent stations. A bandwidth wastage prevention policy is proposed to utilize the unused guard bandwidth to fulfill the requests of lower priority calls and eventually to improve the bandwidth utilization of the network. Based on the total amounts of the guard bandwidth received by the lower priority calls, a novel bandwidth borrowing scheme is proposed. A Markov model is developed to analyze the performance of the proposed CAC method; analytical handover call dropping probabilities and new call blocking probabilities of various service classes are obtained using the proposed Markov model. Simulation experiments are conducted to compare the performance of the proposed CAC method with a fixed guard bandwidth based CAC method. The proposed method showed superior performance than the fixed guard bandwidth based method. Also, the simulation results are compared with the analytical results.