Network Coding Scheme Research Articles

Distance Spectrum and Performance of Channel-Coded Physical-Layer Network Coding for Binary-Input Gaussian Two-Way Relay Channels

We investigate a channel-coded physical-layer network coding (CPNC) scheme for binary-input Gaussian two-way relay channels. In this scheme, the codewords of the two users are transmitted simultaneously. The relay computes and forwards a network-coded (NC) codeword without complete decoding of the two users' individual messages. We propose a new punctured codebook method to explicitly find the distance spectrum of the CPNC scheme. Based on that, we derive an asymptotically tight performance bound for the error probability. Our analysis shows that, compared to the single-user scenario, the CPNC scheme exhibits the same minimum Euclidean distance but an increased multiplicity of error events with minimum distance. At a high SNR, this leads to an SNR penalty of at most ln2 (in linear scale), for long channel codes of various rates. Our analytical results match well with the simulated performance.

Distance Spectrum and Performance of Channel-Coded Physical-Layer Network Coding for Binary-Input Gaussian Two-Way Relay Channels

We investigate a channel-coded physical-layer network coding (CPNC) scheme for binary-input Gaussian two-way relay channels. In this scheme, the codewords of the two users are transmitted simultaneously. The relay computes and forwards a network-coded (NC) codeword without complete decoding of the two users' individual messages. We propose a new punctured codebook method to explicitly find the distance spectrum of the CPNC scheme. Based on that, we derive an asymptotically tight performance bound for the error probability. Our analysis shows that, compared to the single-user scenario, the CPNC scheme exhibits the same minimum Euclidean distance but an increased multiplicity of error events with minimum distance. At a high SNR, this leads to an SNR penalty of at most ln2 (in linear scale), for long channel codes of various rates. Our analytical results match well with the simulated performance.

Single Relay Selection for Bidirectional Cooperative Networks with Physical-Layer Network Coding

To serve the growing demand of the bidirectional information exchange, we propose a single relay selection (RS) scheme for physical-layer network coding (PNC) in a bidirectional cooperative network consisting of two sources and multiple relays. This RS scheme selects a single best relay by maximizing the bottleneck of the capacity region of both information flows in the bidirectional network. We show that the proposed RS rule minimizes the outage probability and that it can be used as a performance benchmark for any RS rules with PNC. We derive a closed-form exact expression of the outage probability for the proposed RS rule and show that it achieves full diversity gain. Finally, numerical results demonstrate the validity of our analysis.

Single Relay Selection for Bidirectional Cooperative Networks with Physical-Layer Network Coding

To serve the growing demand of the bidirectional information exchange, we propose a single relay selection (RS) scheme for physical-layer network coding (PNC) in a bidirectional cooperative network consisting of two sources and multiple relays. This RS scheme selects a single best relay by maximizing the bottleneck of the capacity region of both information flows in the bidirectional network. We show that the proposed RS rule minimizes the outage probability and that it can be used as a performance benchmark for any RS rules with PNC. We derive a closed-form exact expression of the outage probability for the proposed RS rule and show that it achieves full diversity gain. Finally, numerical results demonstrate the validity of our analysis.

A practical network coding and routing scheme based on maximum flow combination

Network coding is a novel field of information theory and coding theory. It is a breakthrough over the traditional store-and-forward routing methods by allowing coding of two or more packets together. From an information flow aspect, multiple flows could be overlapped in a routing scheme. Hence the theoretical upper bound of multicast capacity could be achieved by network coding. In this project, a complete routing and coding scheme is constructed to realize the maximum multicast transportation task. In order to implement the scheme, the paths of multiple max-flows are determined. Edges are divided into overlapped and normal type based on the merged max-flows. The transmitting data are represented using packets in a specific format. Multicast, forward and coding operations are defined to transmit data at the nodes. The nodes are classified according to the type of operation. A dynamic coding and routing algorithm is proposed to route packets gradually from source node to destinations in topological sorting order by the three operations on the path of merged max-flows. We show that the use of simple XOR operations can satisfy most of the network topologies. The running time of the algorithm presented here is less than 1 second for most of the benchmark and random datasets. Copyright © 2012 John Wiley & Sons, Ltd.

Single and Multi Coding Schemes for Efficient Wireless Sensor Networks

Wireless Sensor Networks (WSN) has become an appealing field of research because of its wide range of applications in different fields. In recent years, a significant amount of research has focused on improving network lifetime irrespective of the network throughput. This paper focuses on improving network throughput by using efficient coding techniques and different coding schemes without affecting the lifetime. It is shown that throughput increases with the increase of the BCH coding rate. Also, the use of multi coding is investigated. Different rates/codes are studied between sensor nodes and the network master (NM) and between the NM and the sink.

Cooperative network-coding system for wireless sensor networks

Describes a cooperative network coding system for wireless sensor networks. In this paper, we propose two practical power) and bandwidth)efficient systems based on amplify)and)forward (AF) and decode)and)forward (DF) schemes to address the problem of information exchange via a relay. The key idea is to channel encode each source’s message by using a high)performance non)binary turbo code based on Partial Unit Memory (PUM) codes to enhance the bit)error)rate performance, then reduce the energy consumption and increase spectrum efficiency by using network coding (NC) to combine individual nodes’ messages at the relay before forwarding to the destination. Two simple and low complexity physical layer NC schemes are proposed based on combinations of received source messages at the relay. We also present the theoretical limits and numerical analysis of the proposed schemes. Simulation results under Additive White Gaussian Noise, confirm that the proposed schemes achieve significant bandwidth savings and fewer transmissions over the benchmark systems which do not resort to NC. Theoretical limits for capacity and Signal to Noise Ratio behaviour for the proposed schemes are derived. The paper also proposes a cooperative strategy that is useful when insufficient combined messages are received at a node to recover the desired source messages, thus enabling the system to retrieve all packets with significantly fewer retransmission request messages.

Performance of network-coding-assisted scheduling schemes and their applications in uplink time division duplexing code division multiple access systems

Network coding can deliver multiple data streams simultaneously and make full use of broadcast nature of wireless channels. The authors propose two diversity-enabled network-coding (NC) schemes to optimise wireless uplink scheduling. The existing scheduling protocols normally have to allow the users with relatively low channel gains to transmit, and it can maintain fairness but reduce congregated throughput. The main idea of the proposed scheme is to always schedule users with the best channel condition, while the use of NC encourages the scheduled users to help others which have not been served previously. Delay and capacity performance for different network coded scheduling schemes are analysed. Round-robin and pure opportunistic scheduling are evaluated for performance comparison. In order to show the effectiveness of the proposed schemes, NC schedulers are applied to a time division duplexing code division multiple access wireless cellular networks. System-level simulation was carried out based on the third generation partnership project specifications. Per-sector average throughput and cumulative distribution function of user average throughput are adopted as the performance metrics. Analytical and simulation results show that the proposed NC schedulers can achieve a better tradeoff between fairness and throughput than those without NC.

Anti-Eavesdropping Space-Time Network Coding for Cooperative Communications

Due to the broadcast nature of wireless medium, wireless transmissions can be overheard by any undesired receivers with eavesdropping capability within source transmission range. A novel physical layer approach for secure wireless cooperative communications against eavesdropping is proposed in this paper. For an asynchronous cooperative communication network with a cluster of user nodes transmitting to a common destination, we propose an anti-eavesdropping space-time network coding (AE-STNC) scheme to prevent eavesdropping and overcome the problem of imperfect synchronization. In the proposed scheme, training symbols are first transmitted by the destination (D). Owing to channel reciprocity, each user node can obtain the channel state information (CSI) between itself and D, which is unavailable to the eavesdroppers. By exploiting such CSI, anti-eavesdropping encoding is designed for each user node to create high decoding error rate at the eavesdroppers and ensure successful decoding at D. Furthermore, the AE-STNC is designed to achieve full diversity at D. Power allocation subject to average power constraint is considered and the secure region against eavesdroppers is also investigated. Based on the proposed AE-STNC scheme, an anti-eavesdropping space-time-frequency coding (AE-STFNC) scheme is proposed for broadband asynchronous cooperative communications. Simulations are provided to verify the performance and security of the proposed transmission schemes.

Differential Space-Time Network Coding for Multi-Source Cooperative Communications

Due to the asynchronous nature of cooperative communications, simultaneous transmissions from two or more nodes are challenging in practice. The existing cooperative communications employing successive transmission from one user node to the other can avoid the synchronization problem but results in large transmission delay. In addition, channel estimation in multi-source cooperative communications is a challenging and costly task due to the amount of training, especially when the number of cooperative users is large. Considering these practical challenges in multi-source cooperative communications, this paper proposes a differential space-time network coding (DSTNC) scheme for narrowband multi-source cooperative communications to overcome the problems of imperfect synchronization and complex channel estimation without introducing large transmission delay. Each user in the network linearly combines the correctly decoded symbols via network coding and transmits its packet in time division multiple access (TDMA) mode. The pairwise error probability is analyzed and the design criteria of the DSTNC are derived to achieve full diversity. For broadband cooperative communications, distributed differential space-time-frequency network coding (DSTFNC), which is differentially encoded within each orthogonal frequency-division multiplexing (OFDM) block, is designed through mapping from the proposed DSTNC. When the statistical channel power-delay profile is known at the corresponding user node, each node can permutate its channel independently to improve the performance of the DSTFNC scheme. Simulation results are presented to verify the performance of the proposed schemes.

Short signature scheme for multi-source network coding

It has been proven that network coding can provide significant benefits to networks. However, network coding is very vulnerable to pollution attacks. In recent years, many schemes have been designed to defend against these attacks, but as far as we know almost all of them are inapplicable for multi-source network coding system. This paper proposed a novel homomorphic signature scheme based on bilinear pairings to stand against pollution attacks for multi-source network coding, which has a broader application background than single-source network coding. Our signatures are publicly verifiable and the public keys are independent of the files so that our scheme can be used to authenticate multiple files without having to update public keys. The signature length of our proposed scheme is as short as the shortest signatures of a single-source network coding. The verification speed of our scheme is faster than those signature schemes based on elliptic curves in the single-source network.

An Improved Analog Network Coding Scheme for Cooperative Communication Systems

An Improved Analog Network Coding Scheme for Cooperative Communication Systems

Joint channel‐network coding strategies for networks with low‐complexity relays

ABSTRACTWe investigate joint network and channel coding schemes for networks when relay nodes are not capable of performing channel coding operations. Rather, channel encoding is performed at the source node, whereas channel decoding is carried out only at the destination nodes. We examine three different decoding strategies: independent network‐then‐channel decoding, serial network and channel decoding, and joint network and channel decoding. Furthermore, we describe how to implement such joint network and channel decoding using iteratively decodable error correction codes. Using simple networks as a model, we derive achievable rate regions and use simulations to demonstrate the effectiveness of the three decoders. Copyright © 2011 John Wiley & Sons, Ltd.

무선 릴레이 시스템에서의 Complex Field Network Coding 기법 적용에 관한 연구

본 논문에서는 릴레이 기반 무선 통신 환경에서 기존의 CFNC (Complex Field Network Coding) 기법 적용 시 발생하는 문제점들을 개선하는 방안을 제시한다. CFNC 기법은 간단한 복소 덧셈 및 뺄셈 연산을 통해 상 하향 링크 신호 교환에 요구되는 시간 구간을 최소화함으로써 전송 효율을 극대화하는 장점을 가진다. 그러나, 기존의 CFNC 기법은 릴레이에서의 ML (Maximum Likelihood) 판정 과정에서 큰 폭의 성능 열화가 발생하는 단점이 있다. 또한, CFNC 기법 적용 시 릴레이의 수신 신호에 다중 주파수 오프셋이 발생함에 따라 릴레이의 미세 주파수 오프셋 추정 성능이 열화 되는 한편, 주파수 오프셋 보상 이후에도 잔류 주파수 오프셋으로 인한 성능 열화가 발생하는 문제점이 있다. 따라서 본 논문에서는 상향 링크의 송신 다이버시티를 이용함으로써 정확도를 개선 가능한 새로운 ML 판정 기법 및 다중 주파수 오프셋 환경에서 적용 가능한 새로운 미세 주파수 오프셋 추정, 보상 기법을 제안한다. 다양한 환경에서의 컴퓨터 모의실험을 통해 제안된 기법들이 CFNC 기법 적용 시 발생하는 문제점들을 효과적으로 개선 가능함을 입증한다. In this paper, a CFNC (Complex Field Network Coding) scheme is presented, which focuses on improving transmission efficiency by reducing time slots that are needed to exchange data frames. Conventional CFNC scheme has the advantage of minimizing the number of time slots required for information exchanges. However, there exists serious performance deterioration because the transmit signals are interfered with each other. Moreover, when CFNC scheme is applied, the estimation and compensation performance of fine frequency offset severely deteriorates due to the multiple frequency offsets in received signal of relay node. In order to overcome these critical problems, we propose an improved CFNC scheme with modified maximum likelihood decision method which uses uplink transmit diversity. Also, we propose an enhanced fine frequency offset estimation method and a corresponding compensation method to deal with the multiple frequency offsets. Corresponding simulation results verify that the proposed methods are able to effectively solve the problems of CFNC scheme.

Zero-forcing dirty paper coding aided physical-layer network coding for MIMO two-way relaying channels with multiple users

This article considers the two-way multiple-input multiple-output (MIMO) relaying channels with multiple users, in which multiple users are served simultaneously by the base station (BS) with the assistance of the relay. The transmission consists of only two phases, doubling the system throughout over traditional one-way half-duplex transmission. A zero-forcing dirty paper coding (ZFDPC) aided physical-layer network coding (PNC) scheme is proposed in this article and the achievable capacity of the ZFDPC aided PNC scheme is derived. Simulation results show that the proposed scheme outperforms the previous decode-and-forward (DF) and zero-forcing beamforming (ZFBF) aided PNC scheme due to more degrees of freedoms and the advantage of PNC. Moreover, we analyze the effect of the imperfect channel state information (CSI) from RS to users at BS side to show the robustness of the proposed ZFDPC aided PNC scheme.

Design and Outage Performance Analysis of Relay-Assisted Two-Way Wireless Communications

Two-way wireless communication has regained significant attention recently over relay channels and network coding techniques have been adopted to improve the spectral efficiency. In the literature, most works assumed knowledge of the channel state information at the transmitter (CSIT) and focused mainly on the three-step network coding (NetC) and two-step superposition coding (SupC) schemes. This work instead targets systems without CSIT and explores in detail the features and limitations of SupC and NetC under both the two-step and three-step frameworks. Equal-rate bi-directional traffic is considered and a comparative study of the schemes is provided. The maximum goodput and robustness to channel knowledge discrepancies are evaluated. Key results include theoretically derived outage regions and performance, and the analysis of the complementary role of NetC and SupC. Special features of the three-step framework and a simple yet efficient protocol, adaptive relay-assisted and direct transmission (ARDT), which smartly exploits the direct link in the absence of CSIT, will also be presented. Optimal power allocation at the relay is also derived for the three-step SupC scheme by exploiting the channel reciprocity (no CSIT required). A significant advantage of ARDT is demonstrated over the recently developed two-step SupC scheme. Numerical results together with extensive discussions are provided.

Network Coded LDPC Code Design for a Multi-Source Relaying System

We investigate LDPC code design for a multi-source single-relay system, with uniform phase-fading Gaussian channels. We specifically consider the asymmetric channels for multiple sources, where the channel condition for each source in the system is different. We focus on LDPC code design when network coding (NC) at the relay is utilized. For the asymmetric sources, we firstly introduce a binary field rate splitting theorem which is used to discover an appropriate NC scheme at the relay. This NC scheme is then used to determine the achievable rates of each source and the whole system. These steps assist us in the development of the main contribution of our work, namely, network coded multi-edge type LDPC (NCMET-LDPC) code design. Extrinsic mutual information transfer (EXIT) chart analysis is utilized to optimize the code profiles. Our results demonstrate two key points. (1) From the whole system point of view, our NCMET-LDPC codes achieve better error performance than that of LDPC codes designed for the system without NC. (2) As a consequence of the binary field rate-splitting theorem, our NCMET-LDPC codes also guarantee better error performance of each asymmetric source. The improvement in error performance is typically about 0.3 dB relative to a system without NC.

Utility-Based Joint Routing, Network Coding, and Power Control for Wireless Ad Hoc Networks

Energy saving and high delivery reliability are two essential metrics in wireless ad hoc networks. In this paper, we propose a joint power control and network coding (PCNC) scheme which regulates the transmission power to reduce the overall energy usage and uses network coding to improve reliability by reducing the number of packet retransmissions. To argue for PCNC scheme, we investigate both unicast and multicast routing scenarios. To evaluate routing optimality, we adopt expected utility as a metric, which integrates energy cost, reliability, and benefit value. Based on the expected utility, we explore the optimality in both unicast and multicast routing. For unicast routing, we propose an optimal algorithm. We show the NP-hardness of multicast routing problem, and also design a heuristic solution. Results from simulations demonstrate that PCNC improves the performance in terms of expected utility compared with existing techniques.

A source authentication scheme using network coding

In this paper, we explore the security merits of network coding and potential trade-offs with the widely accepted throughput benefits, especially in multicast scenarios. In particular, we propose a novel Source Authentication using Network Coding (SANC) scheme. Towards this objective, we propose a general framework for embedding the authentication information within the network coding Global Encoding Vector. First, we illustrate the proposed concept using a simple mapping function. Second, we present a detailed security analysis that reveals the security merits of the proposed scheme, contrasted against two baseline schemes. Finally, we present simulation results pertaining to the network coding performance.

Scattered Random Network Coding for Efficient Transmission in Multihop Wireless Networks

Packet error rate dramatically increases when transmissions go over multiple hops in wireless networks, leading to substantial throughput performance degradation. However, in real wireless channels, bit error probabilities vary across different bit positions in one modulation symbol, and corruption of the packet is largely due to the incurred errors on those “bad” bit positions. To improve the throughput performance in multihop wireless networks, in this paper, we propose a novel scattered random network coding (which is referred to as S-RNC) scheme, which further exploits the usefulness of random network coding and takes advantage of error position diversity. In S-RNC, the random-network-coded blocks are classified into different groups, and certain groups of blocks are selected as protected blocks. The sender and relays always scatter the bits of these protected coded blocks on “good” bit positions (with low error probability) and the rest on “bad” bit positions (with high error probability). Rather than sharing the same error rate across all blocks in the conventional transmission scheme, the error probabilities of protected blocks in S-RNC significantly decrease, even over multiple hops, which is helpful in achieving overall higher throughput, particularly under poor channel conditions. Corroborating our intuition, our extensive simulation results show that S-RNC substantially improves throughput performance in multihop mode of wireless networks.