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" Knowing is not enough; we must apply.
Willing is not enough; we must do."

- Johann Wolfgang von Goethe

Research Summary

Research work @ IITH, refer: Networked Wireless Systems (NeWS) Lab

  • COGNET (Past Work @ UC San Diego and IIT Madras)

    • Deployment of a testbed for Cognitive wireless networking research
    • Cost-effective and scalable sampling stratagies for traffic characterization in multi-channel wireless networks
    • Spatio-temporo-spectral traffic characterization in UCSD wireless LAN environment
    • Design of a Cognitive controller using ANNs for channel assignment in wireless LAN
  • Adaptive-FEC based Packet Loss Resilience Scheme for Supporting Voice Communication over Ad hoc Wireless Networks

    • By exploiting the strengths of path diversity, packet level media-dependent adaptive FEC, layered coding, and multiple description coding, an effective packetization scheme is proposed to achieve the best perceived voice quality while not increasing the overheads associated in transmitting small sized voice packets in Ad hoc wireless networks.
    • We presented an analytical approach based on renewal error process to evaluate the performance of proposed scheme in terms of two parameters: residual packet loss rate and average burst length of voice data after FEC recovery. The values of both these parameters depend on FEC-Offset (the distance between original voice frame and piggybacked redundant voice frame) and loss rate present in the network. Finally, these parameters are computed for a Gilbert-Elliott two-state Markov error model and compared with experimental data. %Our scheme adaptively selects the FEC-Offset (it chooses FEC-Offset that minimizes RPLR and ABL as much as possible) based on the loss rate feedback obtained from the destination.
  • Providing MAC QoS for Multimedia Traffic in IEEE 802.11e MAC Based Multi-hop Ad hoc Wireless Networks

    • Our contribution is threefold: First we propose dynamic ReAllocative Priority (ReAP) scheme, wherein the priorities of packets in the MAC queues are not fixed, but keep changing dynamically based on laxity and hop count.
    • Second, we introduce Adaptive-TXOP (A-TXOP), where transmission opportunity (TXOP) is the time interval during which a node has the right to initiate transmissions. This scheme reduces the latency of video traffic by reducing the number of channel accesses required to transmit large video frames (especially I-frames).
    • Finally, we have TXOP-sharing, which is aimed at reducing the latency of voice traffic. The three schemes work together to improve the performance of multimedia transmission, while at the same time does not deviate much from the existing standard, enabling it to be implemented easily with minimal modification.
  • Investigated the Influence of QoS Routing on the Achievable Capacity in TDMA-based Ad hoc Wireless Networks

    • Analysis takes into consideration the behavior of the routing protocol and the inter-dependence of resources (time-slots) of neighboring regions in a wireless network.
    • Derived analytical bounds on the call acceptance and the system saturation for the case of differentiated-classes of users in TDMA-based ad~hoc wireless network framework. %These bounds depend on the routing protocol and the sharing of resources across regions.
    • Simulation studies indicate that the current routing protocols fall short of the established bounds. Amongst the protocols compared, the one that incorporated load-balancing out-performed the shortest-path routing based protocol. This clearly indicates the importance of load-balancing in the attainment of high network performance, and the provision of better QoS guarantees.
  • Designed a Novel Multi-path Routing Protocol that simultaneously tackles the twin issues of Reliability (protection against failures of multiple paths) and Security, while ensuring minimum Data redundancy in Mobile Ad hoc wireless networks

    • Optimal coding schemes based on packet-level systematic Forward Error Correction (FEC) are employed to minimize the data redundancy.
    • The protocol proposed is adaptive as the failure model and the number of paths to be setup for a session are decided depending on the current nature of the paths available between the source and destination nodes, and the reliability and security requirements specified by the source.
  • Designed Multiple-tree Multicast Routing Protocols for Robust and Efficient Video and Voice Multicasting in Mobile Ad hoc Wireless Networks

    • Exploited the path-diversity and the error resilience properties of Multiple Description Coding (MDC) technique for achieving robust video and voice multicasting.
    • Employed a novel path-based Steiner tree heuristic to reduce the number of forwarders in each tree, and construct multiple trees in parallel with reduced number of common nodes among them.
    • Comparison of various Multiple Description Coding (MDC)-FEC schemes for robust video multicasting in mobile ad~hoc networks.

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