We consider physical network coding on a two-way relay channel. Two source nodes send their packets simultaneously over time-varying MIMO channels to a relay node. Assuming that the relay employs the joint decode-and-...
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We consider physical network coding on a two-way relay channel. Two source nodes send their packets simultaneously over time-varying MIMO channels to a relay node. Assuming that the relay employs the joint decode-and-forward strategy, the relay must be able to decode the individual source packets. This task requires a robust estimation of the source-to-relay channels. We design a message passing algorithm based on factor-graphs to solve this problem efficiently.
network codes designed specifically for distributed storage systems have the potential to provide dramatically higher storage efficiency for the same availability. One main challenge in the design of such codes is the...
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ISBN:
(纸本)9781467307734;9781467307758
network codes designed specifically for distributed storage systems have the potential to provide dramatically higher storage efficiency for the same availability. One main challenge in the design of such codes is the exact repair problem: if a node storing encoded information fails, in order to maintain the same level of reliability we need to create encoded information at a new node. One of the main open problems in this emerging area has been the design of simple coding schemes that allow exact and low cost repair of failed nodes and have high data rates. In particular, all prior known explicit constructions have data rates bounded by 1/2. In this paper we introduce the first family of distributed storage codes that have simple look-up repair and can achieve rates up to 2/3. Our constructions are very simple to implement and perform exact repair by simple XORing of packets. We experimentally evaluate the proposed codes in a realistic cloud storage simulator and show significant benefits in both performance and reliability compared to replication and standard Reed-Solomon codes.
In resource-limited wireless sensor networks(WSNs), network resource will run out soon due to communication of mass redundant data. We employ network coding as an effective in-network processing strategy to reduce the...
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In resource-limited wireless sensor networks(WSNs), network resource will run out soon due to communication of mass redundant data. We employ network coding as an effective in-network processing strategy to reduce the data transmission amount. With this concern, a comprehensive network-Calculus based analytical framework for Cluster-tree WSNs involving network coding is established in this paper. To specify, we firstly derive the service curve for sensor node performing network coding; then some useful performance expressions like input/output arrival curve, buffering requirements and end-to-end delay are calculated; finally, to show the effectiveness and superiority of our proposed analytical framework, we demonstrate how to apply the analytical framework to a special IEEE802.15.4/Zigbee protocol. Indeed, numerical results show that network coding does improve buffer requirement and end-to-end delay compared with classical scheduling strategy.
We present an improved decoding algorithm for joint turbo decoding and physical-layer network coding. Instead of decoding the individual (binary) messages separately at the relay, the proposed algorithm, from the supe...
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We present an improved decoding algorithm for joint turbo decoding and physical-layer network coding. Instead of decoding the individual (binary) messages separately at the relay, the proposed algorithm, from the superimposed faded signals, yields an XOR estimate of the sent messages. Moreover, we introduce a softening of the XOR values to improve the overall performance. Simulation results show that this simple idea yields gains up to 4.5 dB in a Rayleigh fading channel model when compared to a similar scheme.
The problem of maximum rate achievable with analog network coding for a unicast communication over a layered wireless relay network with directed links is considered. A relay node performing analog network coding scal...
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ISBN:
(纸本)9781467325790
The problem of maximum rate achievable with analog network coding for a unicast communication over a layered wireless relay network with directed links is considered. A relay node performing analog network coding scales and forwards the signals received at its input. Recently this problem has been considered under two assumptions: (A) each relay node scales its received signal to the upper bound of its transmit power constraint, (B) the relay nodes in specific subsets of the network operate in the high-SNR regime. We establish that assumption (A), in general, leads to suboptimal end-to-end rate. We also characterize the performance of analog network coding in a class of symmetric layered networks without assumption (B). The key contribution of this work is a lemma that states that in a layered relay network a globally optimal set of scaling factors for the nodes that maximizes the end-to-end rate can be computed layer-by-layer. Specifically, a rate-optimal set of scaling factors for the nodes in a layer is the one that maximizes the sum-rate of the nodes in the next layer. This critical insight allows us to characterize analog network coding performance in network scenarios beyond those that can be analyzed using the existing approaches. We illustrate this by computing the maximum rate achievable with analog network coding in one particular layered network, in various communication scenarios.
A novel network coding based coordinated multipoint (NC-CoMP) process, which allows one of the cooperative base stations (BSs) to serve one more non-cell-edge UE simultaneously in its own cell, is proposed in this pap...
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ISBN:
(纸本)9781467318808
A novel network coding based coordinated multipoint (NC-CoMP) process, which allows one of the cooperative base stations (BSs) to serve one more non-cell-edge UE simultaneously in its own cell, is proposed in this paper. To implement the NC-CoMP transmission, an alignment combined precoding(ACP) algorithm is designed to eliminate the inter-user interference and simultaneously to extract useful signal from the network coded signals. Two algorithms are presented to optimize the precoding vectors with the aim at maximizing the receive signal-to-noise rate(SNR) of the cell-edge users. Compared with the conventional two UE multi-user coherent joint processing CoMP (CJP-CoMP) scheme, the proposed NC-CoMP scheme can increase the date throughput significantly without requiring any extra resources. Simulations also illustrate that the bit error rate (BER) performance of the cell-edge users can be improved significantly when the NC-CoMP scheme is employed.
In order to improve broadcasting efficiency in LTE-A system, a novel HARQ scheme with network coding (NC) technology is presented in this paper. The implementation level of XORing NC is selected based on LTE system, a...
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ISBN:
(纸本)9781467358309
In order to improve broadcasting efficiency in LTE-A system, a novel HARQ scheme with network coding (NC) technology is presented in this paper. The implementation level of XORing NC is selected based on LTE system, and an XORing NC Combined (XNCC) strategy is developed to perform combined retransmission. The main idea of proposed scheme is to retransmit lost packets for multiple receivers simultaneously utilizing NC technology. Moreover, we extend the proposed scheme to relay broadcasting system. The simulation results illustrate that compared with traditional retransmission scheme, the average number of transmissions of the proposed NC-HARQ scheme can be sharply decreased, and the coding gains can be attributed to the potential advantage of NC technology.
network coding provides a powerful mechanism for improving performance of communication networks. In this paper, we present an analytical approach for per-flow performance analysis in network coding. Prior work on per...
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network coding provides a powerful mechanism for improving performance of communication networks. In this paper, we present an analytical approach for per-flow performance analysis in network coding. Prior work on performance analysis in network coding mainly focuses on the throughput of the overall network. Our approach aims to analyze the end-to-end performance of each flow in the network. The theoretical basis of our approach is Real-Time Calculus (RTC). Under the framework of RTC, we obtain theoretical formulations for computing the backlog and delay bounds of flows in network coding. Based on the formulations, we evaluate the per-flow performance in representative scenarios and investigate the effect of coding opportunities. Numerical results show that the coding opportunities at coding nodes can significantly affect the end-to-end performance of flows in network coding.
Cooperative communication, which utilizes neighboring nodes to relay the overhearing information, has been employed as an effective technique to deal with the channel fading and to improve the network performances. An...
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Cooperative communication, which utilizes neighboring nodes to relay the overhearing information, has been employed as an effective technique to deal with the channel fading and to improve the network performances. And network coding, which combines several packets together for transmission, is very helpful to reduce the redundancy at the network and to increase the overall throughput. Introducing network coding into the cooperative retransmission process, enables the relay node to assist other nodes while serving its own traffic simultaneously. To leverage the benefits brought by both of them, an efficient Medium Access Control (MAC) protocol is needed. In this paper, we propose a novel network coding aware cooperative MAC protocol, namely NCAC-MAC, for wireless networks. The design objective of NCAC-MAC is to increase the throughput and reduce the delay of the network. Simulation results reveal that our NCAC-MAC can improve the network performance under general circumstances.
Random linear network coding can provide robustness to link losses, and in this work we present an approach to achieve a chosen level of reliability. We formulate the subgraph construction problem, in which participat...
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Random linear network coding can provide robustness to link losses, and in this work we present an approach to achieve a chosen level of reliability. We formulate the subgraph construction problem, in which participating links are identified along with the number of coded packets contributed by each, as a min-cost network flow problem with probabilistic constraints to represent per-link reliability requirements. We show how to transform this problem into an integer linear program and provide an approximate algorithm to solve it. We then analyze the end-to-end reliability provided by the scheme, and present an algorithm to compute the probability of successful decoding at the destination node, in the case that the network coding subgraph is a Two Terminal Series Parallel (TTSP) graph. Results from numerical examples and Monte Carlo simulation indicate that the end-to-end reliability is accurately computed by our scheme, and that our subgraph construction approach provides a means to select the operating point in the tradeoff between reliability and subgraph cost.
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