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: DBLP


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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    • "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.
    IEEE Transactions on Wireless Communications 10/2014; 13(10):5582-5595. DOI:10.1109/TWC.2014.2330591 · 2.50 Impact Factor
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    ABSTRACT: Recently, physical-layer network coding (PNC) attracts much attention due to its ability to improve throughput in relay-aided communications. However, the implementation of PNC is still a work in progress, and synchronization is a significant and difficult issue. This paper investigates the feasibility of synchronous PNC with M-ary quadrature amplitude modulation (M-QAM). We first propose a synchronization scheme for PNC. Then, we analyze the synchronization errors and overhead of potential synchronization techniques, which includes phase-locked loop (PLL) and maximum likelihood estimation (MLE) based synchronization schemes. Their effects on the average symbol error rate and the goodput are subsequently discussed. Based on the analysis, we perform numerical evaluations and reveal that synchronous PNC can outperform conventional network coding (CNC) even when taking synchronization errors and overhead into account. The theoretical throughput gain of PNC over CNC can be approached when using the MLE based synchronization method with optimized training sequence length. The results in this paper provide some insights and benchmarks for the implementation of synchronous PNC.
    IEEE Transactions on Wireless Communications 08/2013; 12(8):4048-4057. DOI:10.1109/TWC.2013.052213.121583 · 2.50 Impact Factor
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    ABSTRACT: In this paper, we investigate the carrier sensing range (CSR) of a general 802.11 network with physical-layer network coding (PNC). We aim to derive a sufficient CSR that can prevent the hidden-node collisions in a general 802.11 PNC network. The analysis includes two steps. First, we analyze the six link-to-link interference cases in an 802.11 PNC network to show that the mutual interference will be most severe when each node in the network initiates a two-hop end node link. Second, we consider the worst interference case that all concurrently transmitting links in the network are two-hop end node links and placed in the densest manner and develop a closed-form expression of a sufficient CSR that prevents the hidden-node collisions in a PNC network. From the analysis results, we find that to prevent the hidden-node collisions, the CSR in PNC network should be bigger than the one in traditional non-network-coding network. Furthermore, we carry out extensive simulations to find out the throughput gain of PNC scheme in a general wireless network when considering the impact of CSR. Simulation results show that compared with the non-network-coding scheme, PNC scheme has throughput gain when a large proportion (i.e., 90%) of links in the network are two-hop links and the link density has little effect on the throughput gain of PNC scheme. Copyright © 2014 John Wiley & Sons, Ltd.
    Wireless Communications and Mobile Computing 07/2014; DOI:10.1002/wcm.2489 · 0.86 Impact Factor
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