coding-aware routing can create more coding opportunities by selecting the proper routing path. The main challenge in exploiting network coding is how to develop an effective network coding conditions. In this paper, ...
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coding-aware routing can create more coding opportunities by selecting the proper routing path. The main challenge in exploiting network coding is how to develop an effective network coding conditions. In this paper, we develop the active intersession network coding (AINC) which can create more intersession network coding opportunities than the general intersession network coding (GINC) by actively exploiting the redundancy information in the network with the deliberately built bridge links. With the aim to find multiple candidate parallel paths for each unicast, the conventional Bellman-Ford algorithm is enhanced. Built on AINC and the enhanced Bellman-Ford algorithm, we propose the active intersession network coding-aware routing (AINC-AR) scheme for the wireless network which supports multiple unicasts. The basic idea of AINC-AR is to select the path from all available candidate ones by jointly considering the effects of network coding gains and path costs on the overall network costs, so as to minimize the total network costs. Simulations are conducted to demonstrate the advantages of AINC-AR over GINC-AR and the conventional routing scheme without considering network coding.
With the rapid increase of space applications, the amount of information to be transmitted between spacecrafts and ground stations increases exponentially and space-sky-ground Transport Control Protocol (TCP) network ...
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With the rapid increase of space applications, the amount of information to be transmitted between spacecrafts and ground stations increases exponentially and space-sky-ground Transport Control Protocol (TCP) network is highly demanded. However, the traditional TCP cannot be directly applied to space data communication. This article deeply studies the TCP/network coding (NC), which can effectively improve terrestrial wireless communication system throughput. Combined with characteristics of Space Communication Protocol Specification-Transport Protocol (SCPS-TP) and advantages of terrestrial TCP/NC, an improved protocol referred to as SCPS-TP/NC, is proposed for space data communication. This article provides detailed process of protocol design, mathematical modelling and throughput analysis of the proposed SCPS-TP/NC. Finally, we implement the SCPS-TP/NC protocol and evaluate its performance by network Simulator (Version 2). Simulation results show that SCPS-TP/NC can effectively increase the end-to-end system throughput, reduce the packet loss rate, shorten the transmission delay and improve the Quality of Service (QoS) of space data communication to a certain degree.
In recent years, network coding has emerged as an innovative method that helps a wireless network approach its maximum capacity by combining multiple unicasts in one broadcast. However, the majority of research conduc...
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In recent years, network coding has emerged as an innovative method that helps a wireless network approach its maximum capacity by combining multiple unicasts in one broadcast. However, the majority of research conducted in this area is yet to fully utilize the broadcasting nature of wireless networks and still assumes a fixed route between the source and destination that every packet should travel through. This assumption not only limits coding opportunities but can also cause buffer overflow in some specific intermediate nodes. Although some studies considered scattering of the flows dynamically in the network, they still face some limitations. This paper explains pros and cons of some prominent research in network coding and proposes a Flexible and Opportunistic network coding Scheme (FlexONC) as a solution to such issues. Furthermore, this research discovers that the conditions used in previous studies to combine packets of different flows are overly optimistic and would affect the network performance adversely. Therefore, we provide a more accurate set of rules for packet encoding. The experimental results show that FlexONC outperforms previous methods especially in networks with high bit error rate, by better utilizing redundant packets spread in the network.
network coding is a technique that can be used to improve the performance of communication networks by performing mathematical operations at intermediate nodes. An important problem in coding theory is that of finding...
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network coding is a technique that can be used to improve the performance of communication networks by performing mathematical operations at intermediate nodes. An important problem in coding theory is that of finding an optimal coding subgraph for delivering network data from a source node throughout intermediate nodes to a set of destination nodes with the minimum transmission cost. However, in many real applications, it can be difficult to determine exact values or specific probability distributions of link costs. Establishing minimum-cost multicast connections based on erroneous link costs might exhibit poor performance when implemented. This paper considers the problem of minimum-cost multicast using network coding under uncertain link costs. We propose a robust optimization approach to obtain solutions that protect the system against the worst-case value of the uncertainty in a prespecified set. The simulation results show that a robust solution provides significant improvement in worst-case performance while incurring a small loss in optimality for specific instances of the uncertainty.
network coding (NC) for wireless local area network has received a lot of attention from researchers. It replaces the traditional methods of video erasure protection. The principal of NC is to combine several packets ...
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network coding (NC) for wireless local area network has received a lot of attention from researchers. It replaces the traditional methods of video erasure protection. The principal of NC is to combine several packets together before their transmission. Thus, NC is able to provide higher throughput, reliability and efficient transmission. Up to now, many works have been done to ensure the advantages and the robustness of NC against the packet loss and link failures. The performance gains of NC are successfully processed not only for data to increase throughput, but also for video streaming over wireless networks. In this context, this paper surveys and discusses the most popular approaches based on NC of both data and video transmission over wireless network (static or dynamic). Strength and limitations for robust video streaming and data transmission are deeply discussed.
This study is concerned with the network coding (NC) problem in error-prone wireless multicast networks. A hash searching and NC-based constant retransmission scheme (HSNCR) is proposed to make combination selection, ...
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This study is concerned with the network coding (NC) problem in error-prone wireless multicast networks. A hash searching and NC-based constant retransmission scheme (HSNCR) is proposed to make combination selection, where the retransmission of the packet losses can be carried out during the whole process of original packet transmission, and thus the HSNCR can increase the possibility of NC. Furthermore, this new scheme maximises the efficiency of every retransmission by only retransferring an optimum combination or maximum combination of original lost packets. To support HSNCR, an efficient hash searching approach is also designed for the combination selection of original lost packets. Simulation results show that the authors' proposed scheme indeed outperforms previous works in reducing the number of retransmission.
This paper considers the downlink traffic from a base station to two different clients. When assuming infinite backlog, it is known that inter-session network coding (INC) can significantly increase the throughput. Ho...
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This paper considers the downlink traffic from a base station to two different clients. When assuming infinite backlog, it is known that inter-session network coding (INC) can significantly increase the throughput. However, the corresponding scheduling solution (when assuming dynamic arrivals instead and requiring bounded delay) is still nascent. For the two-flow downlink scenario, we propose the first opportunistic INC + scheduling solution that is provably optimal for time-varying channels, i.e., the corresponding stability region matches the optimal Shannon capacity. In particular, we first introduce a new binary INC operation, which is distinctly different from the traditional wisdom of XORing two overheard packets. We then develop a queue-length-based scheduling scheme and prove that it, with the help of the new INC operation, achieves the optimal stability region with time-varying channel quality. The proposed algorithm is later generalized to include the capability of rate adaptation. Simulation results show that it again achieves the optimal throughput with rate adaptation. A byproduct of our results is a scheduling scheme for stochastic processing networks with random departure, which relaxes the assumption of deterministic departure in the existing results.
We consider a large class of bidirectional relaying scenarios with physical layer network coding, and analytically characterize the relay's error performance in decoding the network-coded combination at high signa...
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We consider a large class of bidirectional relaying scenarios with physical layer network coding, and analytically characterize the relay's error performance in decoding the network-coded combination at high signal-to-noise ratio (SNR). Our analysis applies to scenarios with 1) binary or higher order real/complex modulation, 2) real or complex channel coefficients, and 3) linear or non-linear network maps for network coding at the relay. We consider block fading and allow the relay to choose from a set of network maps based on the channel coefficients of the source to relay links in every block. We derive expressions for pairwise error probability and approximate expected overall error probability. We also derive lower bounds for these error probabilities. We validate these expressions using simulations and show that our approximations are tight in the high SNR regime.
This paper presents the first reliable physical-layer network coding (PNC) system that supports real TCP/IP applications for the two-way relay network (TWRN). Theoretically, PNC could boost the throughput of TWRN by a...
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This paper presents the first reliable physical-layer network coding (PNC) system that supports real TCP/IP applications for the two-way relay network (TWRN). Theoretically, PNC could boost the throughput of TWRN by a factor of 2 compared with traditional scheduling (TS) in the high signal-to-noise (SNR) regime. Although there have been many theoretical studies on PNC performance, there have been relatively few experimental and implementation efforts. Our earlier PNC prototype, built in 2012, was an offline system that processed signals offline. For a system that supports real applications, signals must be processed online in real-time. Our real-time reliable PNC prototype, referred to as RPNC, solves a number of key challenges to enable the support of real TCP/IP applications. The enabling components include: 1) a time-slotted system that achieves mu s-level synchronization for the PNC system;2) reduction of PNC signal processing complexity to meet real-time constraints;3) an ARQ design tailored for PNC to ensure reliable packet delivery;and 4) an interface to the application layer. We took on the challenge to implement all of the above with general-purpose processors in PC through an SDR platform rather than ASIC or FPGA. With all of these components, we have successfully demonstrated image exchange with TCP and two-party video conferencing with UDP over RPNC. Experimental results show that the achieved throughput approaches the PHY-layer data rate at high SNR, demonstrating the high efficiency of the RPNC system.
In this paper, the authors show that using physical layer network coding (PNC) in wireless relay systems does not always increase throughput performance, and to achieve maximum throughput, PNC should be exploited inte...
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In this paper, the authors show that using physical layer network coding (PNC) in wireless relay systems does not always increase throughput performance, and to achieve maximum throughput, PNC should be exploited intelligently regarding to the channel conditions. In this study, they propose a selective PNC (SPNC) scheme in bidirectional relay systems for binary phase shift keying. In the proposed scheme, the relay chooses either to detect network-coded data from superimposed signal by PNC scheme or single source data by a so-called single node detection (SND) scheme, based on which offers more end-toend throughput for current channel realisation. They analytically determine the region of channel state plane in which SPNC selects SND scheme. Also, they obtain expressions for instantaneous bit error rates (BERs) of PNC and SND protocols. Moreover, they derive upper bounds in closed-form for average BERs of PNC and SND schemes during multiple access phase at the relay. Then, they investigate SPNC with high-order modulations. Simulations and analytical results confirm that SPNC achieves considerable throughput gain over PNC in Rayleigh fading channels.
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