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Guest Editorial

Author(s): Antonios Argyriou | Joerg Widmer | Bob Li

Journal: Journal of Communications
ISSN 1796-2021

Volume: 4;
Issue: 11;
Start page: 827;
Date: 2009;
Original page

Keywords: Special Issue | Network Coding | Network Applications

In today's world there is an increasing need for networked services. This need is propelled by the rapid advances in both computing and communications technologies that enable many more new applications. Most of these networked services utilize a packet-switched backbone that is based on the Internet Protocol (IP). This backbone infrastructure has performed extremely well, except in scenarios where bandwidth, latency, and energy consumption requirements are more crucial. This is usually the case in wireless networks. This means that the classical functionalities of the OSI network protocol stack that fitted very well the requirements of the networks of the past, may not be sufficient in more demanding scenarios where bandwidth utilization, energy consumption, and latency are of extreme importance.Among all possible solutions that have been investigated throughput the years, information theory has recently provided us with a new tool called network coding which allows us to investigate novel ways for architecting communication systems. Network coding is challenging the existing paradigm and it proposes that nodes in a network also execute coding operations on packets besides simply routing them to the appropriate destination. It has been shown that with this technique it is theoretically possible to substantially improve throughput, latency, and energy consumption in different network configurations. The initial theoretical research works on network coding have been followed by numerous activities both on theoretical and also practical aspects. Therefore, it seems that network coding has the potential to be one of the most promising approaches for re-designing future networks and substantially improving performance. Nevertheless, research is still at its infancy and several issues have to be investigated more thoroughly.The aim of this special issue is to bring together the state-of-the-art research contributions that address theoretical and practical design issues of network coding, while it also targets its applications in different domains. In the following, we briefly review all papers included in this special issue. Capacity Scaling of Wireless Networks with Complex Field Network Coding. T. Wang and G. Giannakis investigate the capacity scaling of network coding with respect to the number of nodes in wireless multi-hop networks. While existing works focus on networks with n source-destination pairs, this paper deals with capacity scaling in any-to-any wireless links, where each node communicates with all other nodes. Complex field network coding (CFNC) is adopted at the physical layer to allow n nodes to exchange information with simultaneous transmissions from multiple sources. The authors show that as n increases, the hierarchical CFNC-based scheme that is developed can achieve asymptotically optimal quadratic capacity scaling in a dense network, where the area is fixed and the density of nodes increases. Capacity Enhancement in Hybrid Wireless Relay Network with Network Coding. In the next paper, H.-Y. Chao, C.-Y. Huang, F.-M. Tseng, and H.-Y. Wei, investigate hybrid wireless relay networks that integrate multihop ad hoc relays and infrastructure base stations to achieve better wireless network performance. They also investigate data forwarding strategies to determine if a packet should be transmitted through intra-cell ad hoc relay, and inter-cell ad hoc relay. A thorough performance evaluation under all these scenarios is presented.Cooperative Network Coding with Soft Information Relaying in Two-way Relay Cchannels. Y. Peng, M. Wu, H. Zhao, K. Zheng, W. Wang, and Y. il Kim focus on the design of network coding implemented at the physical layer, and they propose a soft-information-forwarding-based network coding scheme which combines soft network coding and distributed turbo coding scheme in two-way relay channels. They present a theoretical analysis and the simulations confirm that the proposed scheme achieves significant gain over conventional network coding in quasi-static fading channels.Multicast Communications with Reed Solomon/ Network Joint Coding in Wireless Multihop Network. T. Matsuda and T. Takine study a multicast system in wireless multihop networks that employs forward error correction (FEC) for combating packet erasures. In the proposed system, information packets from a source node are encoded by Reed -Solomon erasure (RSE) coding while at intermediate nodes on multicast paths, packets arriving from different links are encoded by linear network coding (LNC). A Linear Inter-Session Network Coding Scheme for Multicast. M. Yang and Y. Yang consider linear inter-session network coding for multicast communications. The basic idea is to divide the sessions into different groups and construct a linear network coding scheme for each group. The authors use two metrics to guide the group division: overlap ratio and overlap width. These two metrics measure the benefit that a system can achieve by inter-session network coding with different considerations.Flow Synchronization for Network Coding. T. Biermann, M. Draxler, and Holger Karl investigate the problem of synchronizing flows that traverse large-scale networks like the Internet and can potentially be network-coded. In this paper, the authors present a set of algorithms that synchronize arbitrary flows in wired and wireless scenarios for joint encoding later on. These algorithms are based on fragmentation and active queue management (AQM) techniques. To demonstrate the benefits of their approach, the authors develop an encoder and decoder for deterministic XOR-based network coding that uses this synchronization technique.Performance Evaluation of Network Coding: Effects of Topology and Network Traffic for Linear and XOR Coding. In this paper, B. Gajic, J. Riihijarvi and P. Mahonen analyze the performance of network coding by focusing on two specific network coding schemes: XOR and random linear network coding. The authors simulate different topologies and traffic patterns in order to provide better understanding of network coding behavior and its possible bottlenecks. As a part of their performance evaluation they consider also the computational complexity of coding and decoding operations which influence packet latency. In particular, they provide potential drawbacks and trade-offs of network coding when applied on specific topologies under specific circumstances by monitoring the differences in XOR and random linear network coding approaches.Network Coding based Dependable and Efficient Data Survival in Unattended Wireless Sensor Networks. W. Ren, Y. Re, and H. Zhang, consider the application of network coding in sensor networks that store locally large sets of data. Data storage in UWSNs should be dependable to defend random failure or node compromise, as well as its efficiency should be maintained. In this paper, the authors propose a dependable and efficient data survival scheme to maximize the data survival upon data retrieval. Their scheme makes use of computational secret sharing to achieve fault tolerance and compromise resilience, and takes advantages of network coding to further improve communication efficiency.Accelerating Network Coding on Many-core GPUs and Multi-core CPUs. In our final paper X. Chu and K. Zhao investigate the computational overhead introduced by the network coding operations. They claim that is not negligible and it can become the obstacle for practical deployment of network coding. In this paper, they exploit the computing power of commodity many-core Graphic Processing Units (GPUs) and multi-core CPUs to accelerate the network coding operations. They propose a set of parallel algorithms that maximize the parallelism of the encoding and decoding processes and fully utilize the power of GPUs.Networking today is being pushed in the background since it is used by many classical non-networked applications. It is projected that an increasing number of devices will need to be networked in the future, especially wirelessly. However, the existing communication paradigm in wired and wireless networks may be limited in the case of high demanding applications in terms of throughput or in terms of energy in wireless networks. We believe that new communication paradigms may emerge and a step towards this direction is the fundamental concept of network coding. Besides the first theoretical works we believe there is a strong need for investigating the applications of this concept in different networks and communication systems. With this in mind, we hope that this special issue can spark and stimulate the research both in theoretical and practical aspects of network coding.We would like to express our sincere thanks to the reviewers who provided the authors with critical, timely and highly constructive feedback. We also thank the staff at the JCM Academy Publisher for their efficiency in handling the manuscripts. Last but not least, our sincere thanks go to the Associate Editor-in-Chief of the JCM Journal of Communications, Dr. Haohong Wang, for his assistance with this special issue.
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