Department of Computer Science and Information Systems
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1928
Browse
6 results
Search Results
Item Cooperative data transmission framework for IEEE 802.16j mobile multihop relay networks(Springer, 2014-05) Rajya Lakshmi, L.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 methodItem PRIME: A partial path establishment based handover management technique for QoS support in WiMAX based wireless mesh networks(Elsevier, 2015-06) Rajya Lakshmi, L.In this paper, we propose a novel handover management technique called PaRtIal path establishment based handover Management tEchnique (PRIME) for WiMAX based wireless mesh networks (WMNs). Different from the currently existing methods for WiMAX networks, PRIME addresses handover management in WiMAX WMNs deployed with distributed scheduling. In these networks, to continue the quality of service (QoS) constrained flows to a mobile node (MN) after its handover, a new path with the required bandwidth and which passes through its new base station (BS) needs to be established as quickly as possible. To address that issue, PRIME handles re-routing and scheduling issues of a handing over MN together. To provide lossless and seamless service, PRIME tries to establish new path(s) in the wireless mesh with the required bandwidth to the MN before it enters into the coverage area of the new BS. The present paper proposes a novel crossover node based partial path establishment algorithm to establish new path(s) which support QoS requirements of handoff calls. To analyze the performance of PRIME, the present paper proposes a multi-dimensional Markov model. Unlike previous models which analyze the performance of wireless networks, our proposed model represents nodes in terms of the number of transmission and reception available slots. The theoretical upper and lower bounds on the call dropping probabilities of handoff calls are obtained. To study the performance advantages of PRIME, we devise another handover management method called RFPHMT which does not use the concept of crossover base station in the new path establishment of a handing over node. The performance of PRIME and RFPHMT are compared in terms of call dropping probabilities and call setup delays. PRIME shows superior performance than RFPHMT. For a random topology, at a high call arrival rate of 1/2000 (calls/milliseconds), the handover call dropping probability of PRIME is 40% less than that of RFPHMT. The call dropping probabilities of PRIME with the simulations are always within the theoretical bounds which proves that the obtained bounds are close to the real call dropping probabilities.Item Handover management framework for WiMAX Point-to-Multi-Point networks(Elsevier, 2016-11) Rajya Lakshmi, L.In this paper, a distributed base station cooperation-based handover management method is proposed for WiMAX Point-to-Multi-Point networks to provide quality of service to handover nodes. Moreover, a delay reduction method is proposed to reduce the packet delivery delays during handover. A Call Admission Control (CAC) algorithm is proposed to handle handover calls of various service classes fairly, according to their priorities. A bandwidth borrowing scheme is proposed to reduce the handover call dropping probabilities of various service classes while not starving the ongoing calls of lower priority service classes. A Markov model is developed to analyze the proposed CAC method and to obtain the approximate handover call dropping probabilities of various service classes. Simulation experiments are conducted to establish the performance advantages of the proposed handover management and CAC methods.Item Adaptive Zone Size Selection Method for IEEE 802.16j Mobile Multihop Relay Networks(Springer, 2017-08) Rajya Lakshmi, L.IEEE 802.16j relay networks are capable of extending the coverage areas of IEEE 802.16 networks and can support the data rate requirements of users at cell edges. In these networks, each frame is divided into various zones to facilitate data transmission between various types of nodes. As the link qualities in the network change, accordingly the zone sizes should also change to support the Quality of Service (QoS) requirements of flows and to avoid bandwidth wastage. To address this issue, in this paper, we propose an adaptive zone size selection method for IEEE 802.16j networks. With this method, zone sizes of scheduling nodes are adaptively changed in accordance with their changing link qualities. As the link qualities degrade, the scheduling nodes may not be able to support the QoS requirements of flows due to the lack of free bandwidth availability in the corresponding zones. To handle this issue with less control overhead, we propose a cross-zone bandwidth allocation method. A zone size reselection method is also proposed to handle the situations where the cross-zone bandwidth allocation is not possible. Performance of the proposed method is compared with the performance of a fixed zone size selection method and a zone size selection method proposed in the literature. The proposed method shows significantly better performance than the other two methods in terms of traffic admittance, bandwidth utilization, and satisfaction ratios of flows.Item Fair Scheduling of Concurrent Transmissions in Directional Antenna Based WPANs/WLANs(IEEE, 2018-07) Rajya Lakshmi, L.With their capability to support high data rates, millimeter-Wave (mmWave) communications are evolving as a promising and potential technology to support high data rate applications in short range networks. This paper addresses the problem of fair scheduling in mmWave wireless personal and local area networks (WPANs/WLANs) to support applications with varying quality of service (QoS) requirements. To ensure fairness while exploiting the spatial reuse facilitated by directional antennas, concurrent transmission scheduling in mmWave WPANs/WLANs is formulated as a multi-objective optimization problem. Two heuristic schedulers are developed to obtain a schedule in real-time. These schedulers first satisfy the minimum QoS requirements of as many flows as possible, and then, allocate the remaining bandwidth to various flows while ensuring long-term and short-term fairness among the flows. Results from extensive simulations conducted in a dense mmWave WPAN show that the proposed fair schedulers provide better fairness and throughput, compared to existing methods.Item Link Quality Aware Dynamic Frame Partition Method for WiMAX Mesh Networks(Springer, 2023-05) Rajya Lakshmi, L.IEEE 802.16 networks deployed in the mesh mode help to extend the coverage areas of the base stations (BSs). Two types of scheduling methods can be used in these networks: centralized and distributed scheduling. It is also possible to use these two scheduling methods together by partitioning the frames between the centralized and distributed flows. As link qualities in the network change, the bandwidth requirements of the nodes change. To support the quality of service (QoS) requirements of the centralized flows that run between the BSs and the subscriber stations and for efficient bandwidth utilization, the partition sizes should be adjusted dynamically according to the changing bandwidth requirements of nodes. To handle this issue, the present paper proposes a dynamic partition size selection method for IEEE 802.16 mesh networks. With this method, nodes change the partition sizes locally according to the changing bandwidth requirements of the centralized flows that are induced by the varying link qualities in the network. The partition sizes are changed network-wide when most of the nodes in the network are affected by the local partition size adjustments. Simulations are performed to compare the performance of the proposed method with the partition method proposed in the IEEE 802.16 standard. It is observed that, in the environments where link qualities vary, the proposed method fulfills the QoS requirements of flows in a better way, compared to the partition method.