Analysis of Channel Estimation Error in Physical Layer Network Coding

Dept. of Electr. & Comput. Eng., Univ. of Maine, Orono, ME, USA
IEEE Communications Letters (Impact Factor: 1.27). 11/2011; 15(10):1029 - 1031. DOI: 10.1109/LCOMM.2011.082011.110301
Source: IEEE Xplore


This article investigates the effect of erroneous channel estimation on performance of physical layer network coding over fading channels. In this scenario, the relay maps the superimposed noisy modulated data, received from the two end terminals, to network coded combination of the source packets. We consider channel estimation error to be Gaussian distributed and formulate the network coding error by the distance between real and estimated points in the channel coefficients plane. Using this model, we present a statistical lower bound on variance of estimation error that can be tolerated by the relay terminal without imposing a network coding error on the system.

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    • "Depending on the application of NC the implementation affects different OSI layers. In multicast scenarios NC is typically implemented in the application layer while two stage NC for increased spectrum efficiency is deployed in the physical layer [10]. We are interested in opportunistic NC for static wireless mesh networks such as metropolitan WiFi networks [11] for unicast traffic. "
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    ABSTRACT: This paper presents a novel, practical, routing-independent network-coding algorithm: BON-Bearing opportunistic network coding. Simplicity is its main benefit as it introduces little overhead to the network since nodes do not need to keep track of received traffic for their neighbouring nodes. Algorithm makes coding decisions based solely on the information about the packet previous and next hop node position. Algorithm functions between the MAC and link layers, with small modifications made only to the MAC layer. Using different topologies and different traffic loads and distributions in the simulation model we evaluated algorithm performance and compared it to a well-known COPE algorithm.
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    • "a set of independent reliable channels, the nature of practical wireless channels is far from this assumption. Consequently, the research of WNC techniques have already revealed several non-trivial research problems which do not appear in the conventional (wireline) NC systems, including the sensitivity to channel parametrization [6]–[10] or challenging multisource transmission synchronization [11]–[13]. "
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    ABSTRACT: Favorable characteristics of wireless channels (including the inherent broadcast and superposition nature) provide a fertile ground for the extension of conventional network coding (NC) principles to wireless communication networks. However, the research of emerging wireless (physical layer) network coding (WNC) techniques have already revealed several non-trivial research problems that do not appear in the conventional (wireline) NC systems, including the sensitivity to channel parametrization and challenging multi-source transmission synchronization. In this paper, we uncover another significant research challenge typical for multi-node WNC systems. We show that the performance of contemporary WNC bi-directional relaying strategies is dominated by the availability of a specific hierarchical side information (HSI), required for the successful decoding of desired information from hierarchical (WNC-coded) data streams. We analyze the impact of unreliable transmission of HSI on the performance of a wireless butterfly network (WBN), and we show that all state-of-the-art relaying strategies must be appropriately modified to avoid the deterioration of WBN performance in the limited HSI regime.
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