Shashi Raj Singh

Polytechnic Institute of New York University, Brooklyn, NY, United States

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Publications (3)0.72 Total impact

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    ABSTRACT: Cooperative communication is a buzz word in research community today. It enables nodes to achieve spatial extensive investigations have been directed to closely examine its performance by means of both analysis and simulation. However, the study of this new technology in an imple- mentation based system is very limited. In this paper, we present two implementation approaches to demonstrate the viability of realizing cooperation at the MAC layer in a real environment. The paper describes the technical challenges encountered in each of the approaches, details the cor- responding solution proposed, and compare the limitations and benefits of the approaches. The experimental measurements are reported, which not only help developing a deeper understand- ing of the protocol behavior but also confirm that the cooperative communication is a promising realistic technology for boosting the performance of next generation wireless networks.
    Preview · Article · Jan 2009 · EURASIP Journal on Wireless Communications and Networking
  • Shashi Raj Singh · Thanasis Korakis · Pei Liu · Shivendra Panwar
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    ABSTRACT: Cooperative communication is a promising approach to improve the reliability of a received signal at the physical layer. Cooperating nodes create a virtual MIMO system that provides spatial diversity even though the nodes have a single antenna. Therefore, tremendous improvements in system capacity and delay can be achieved. An implementation approach has been pursued in this demonstration to confirm the viability and efficacy of cooperation at the physical layer. The implemented cooperative physical layer scheme is called CoopPHY and is based on cooperative coding. In this technique, the source node transmits only a portion of its encoded data bits based on channel conditions among cooperating nodes. Helper nodes transmit the rest of the encoded bits. The destination node, finally, combines and decodes signals received via different channels and therefore increases the decoding reliability. In this demo, a Matlab video clip is streamed frame by frame from a source to destination node using sequentially the direct communication scheme, relaying via one helper, relaying via another helper and finally cooperative scheme. CoopPHY protocol delivers a smooth user experience, while the video playout over the direct scheme shows frequent distortions. In addition to this cooperative coomunication shows better quality than just relaying via any of the helpers.
    No preview · Article · Jan 2009
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    ABSTRACT: Cooperation in wireless networks has shown significant performance gains in comparison to legacy wireless networks. Cooperative wireless protocols achieve such efficiency by enabling cooperation among nodes to exploit spatial diversity. CoopMAC is a medium access control (MAC) protocol that enables cooperation by using an intermediate node as a helper to a direct communication under poor channel conditions. The helper is typically located in a position where it experiences a good channel with both the source and destination. Therefore, it increases the efficiency of the communication by forwarding a packet from the source to the destination using high transmission rates. In an earlier attempt, we demonstrated the benefits of cooperation at the MAC layer by implementing the CoopMAC protocol using an open source wireless driver platform. However, due to some limitations posed by the hardware, the full potential of the protocol could not be explored. In this paper, we proceed with a complete implementation of the cooperative MAC protocol using an OFDM based software defined radio (SDR) platform. We investigate the benefits of the SDR approach, describe the details of the implementation, as well as the experiments we run in order to evaluate the protocol. Experimental results show that CoopMAC can easily be implemented and can lead to a significant improvement in the performance of wireless networks.
    Preview · Conference Paper · Oct 2008