Decoding delay in network coded multipath transmissions

2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013

In this paper we consider the use of inter-packet encoding at the source node to improve the delay performance of data block transmissions in a multipath communication scenario. First we propose a formal derivation to obtain the coding ratio and the per-path packet allocation that minimizes the data block delay. Then we validate this model through an experimental campaign carried out in a testbed in close-to-real conditions. The proposed encoding scheme is also compared with fixed multiplexing criteria previously proposed in the literature for multipath communications scenarios. Our evaluation shows the benefits of the inter-packet encoding specially when packets travelling through the paths experience unbalanced service rates and heavy tail delays. Minimum Transfer Delay (ms)

2010 Information Theory and Applications Workshop, ITA 2010 - Conference Proceedings, 2010

Understanding the delay behavior of network coding with a fixed number of receivers, small field sizes and a limited number of encoded symbols is a key step towards its applicability in real-time communication systems with stringent delay constraints. Previous results are typically asymptotic in nature and focus mainly on the average delay performance. Seeking to characterize the complete delay distribution of random linear network coding, we present a brute-force methodology that is feasible for up to four receivers, limited field and generation sizes. The key idea is to fix the pattern of packet erasures and to try out all possible encodings for various system and channel parameters. Our findings, which are valid for both decoding delay and ordered-delivery delay, can be used to optimize network coding protocols with respect not only to their average but also to their worst-case performance.

Here, we characterize the throughput of a broad cast network with receivers using rate less codes with block size. We characterize the system throughput asymptotically. Specifically, we explicitly show how the throughput behaves for different values of the coding block size as a function. We are able to provide a lower bound on the maximum achievable throughput. Using simulations, we show the tightness of the bound with respect to system parameters and find that its performance is significantly better than the previously known lower bounds. The packets are not decidable if any deviation is occurred.

2009 Information Theory and Applications Workshop, 2009

In networks with large latency, feedback about received packets may lag considerably the transmission of the original packets, limiting the feedback's usefulness. Moreover, time duplex constraints may entail that receiving feedback may be costly. In this work, we consider tailoring feedback and coding jointly in such settings to reduce the expected delay for successful in order reception of packets. We find that, in certain applications, judicious choices provide results that are close to those that would be obtained with a full-duplex system.

IEEE Transactions on Communications, 2000

Intra-session network coding has been shown to offer significant gains in terms of achievable throughput and delay in settings where one source multicasts data to several clients. In this paper, we consider a more general scenario where multiple sources transmit data to sets of clients and study the benefits of inter-session network coding, when network nodes have the opportunity to combine packets from different sources. In particular, we propose a novel framework for optimal rate allocation in inter-session network coding systems. We formulate the problem as the minimization of the average decoding delay in the client population and solve it with a gradient-based stochastic algorithm. Our optimized inter-session network coding solution is evaluated in different network topologies and compared with basic intra-session network coding solutions. Our results show the benefits of proper coding decisions and effective rate allocation for lowering the decoding delay when the network is used by concurrent multicast sessions.

MILCOM 2007 - IEEE Military Communications Conference, 2007

This paper investigates the interaction between network coding and link-layer transmission rate diversity in multihop wireless networks. By appropriately mixing data packets at intermediate nodes, network coding allows a single multicast flow to achieve higher throughput to a set of receivers. Broadcast applications can also exploit link-layer rate diversity, whereby individual nodes can transmit at faster rates at the expense of corresponding smaller coverage area. We first demonstrate how combining rate-diversity with network coding can provide a larger capacity for data dissemination of a single multicast flow, and how consideration of rate diversity is critical for maximizing system throughput. We also study the impact of both network coding and rate diversity on the dissemination latency for a class of quasi real-time applications, where the freshness of disseminated data is important. Our results provide evidence that network coding may lead to a latency-vs-throughput tradeoff in wireless environments, and that it is thus necessary to adapt the degree of network coding to ensure conformance to both throughput and latency objectives. There is an increasing interest in understanding the potential performance gains accruing from the use of network coding in multi-hop wireless environments. In particular, many military battlefield scenarios exhibit two characteristics that appear to motivate the use of network coding: a) the reliance on bandwidth-constrained, ad-hoc wireless links (e.g. using MANETs formed by vehicle-mounted radios in urban insurgencies) and b) the need to disseminate information (e.g., maps, mission commands) to multiple recipients. The initial results on the power of network coding NC, such as the original demonstration in [1] of how in-network mixing of packets by intermediate nodes helps to achieve a communication capacity that is not achievable solely through routing, were obtained for the case of a lossless, wireline network. More recently, several groups have investigated the potential performance gains realized by network coding for both

IEEE/ACM Transactions on Networking

In this paper, we introduce construction techniques for network coding in bidirectional networks with arbitrary transmission delays. These coding schemes reduce the number of transmissions and achieve the optimal rate region in the corresponding broadcast model for both multiple unicast and multicast cases with up to three users, under the equal rate constraint. The coding schemes are presented in two phases; first, coding schemes for line, star and line-star topologies with arbitrary transmission delays are provided and second, any general topology with multiple bidirectional unicast and multicast sessions is shown to be decomposable into these canonical topologies to reduce the number of transmissions. As a result, the coding schemes developed for the line, star, and line-star topologies serve as building blocks for the construction of more general coding schemes for all networks. The proposed schemes are proved to be real time in the sense that they achieve the minimum decoding delay. With a negligible size header, these coding schemes are shown to be applicable to unsynchronized networks, i.e., networks with arbitrary transmission delays. Finally, we demonstrate the applicability of these schemes by extensive simulations. The implementation of such coding schemes on a wireless network with arbitrary transmission delays can improve performance and power efficiency.

2008 5th IEEE International Conference on Mobile Ad Hoc and Sensor Systems, 2008

Network coding is a highly efficient data dissemination mechanism for wireless networks. Since network coded information can only be recovered after delivering a sufficient number of coded packets, the resulting decoding delay can become problematic for delay-sensitive applications such as real-time media streaming. Motivated by this observation, we consider several algorithms that minimize the decoding delay and analyze their performance by means of simulation. The algorithms differ both in the required information about the state of the neighbors' buffers and in the way this knowledge is used to decide which packets to combine through coding operations. Our results show that a greedy algorithm, whose encodings maximize the number of nodes at which a coded packet is immediately decodable significantly outperforms existing network coding protocols.

2014

Network coding is a technique that proposes a different approach for the protocol design in data communication networks. Thus, the nodes in the network are allowed not only to store and forward data packets, but also to process and mix different packets in a single coded packet. By using this technique, the throughput and robustness of the network can be significantly improved. However, the transmission delay of network coding is still not well understood. In real-time communication systems with stringent delay constraints, understanding the transmission delay distribution is at the core of implementing network coding in practical scenarios. Moreover, the benefits of network coding for broadcast scenarios have been proven, but the use of this technique in data gathering applications is limited. Unlike broadcast applications, where the main objective is to minimize the transmission delay, in data gathering applications the challenge is to reduce the data collection time, called the c...

2015

Over the past decade, network coding (NC) has emerged as a new paradigm for data communications and has attracted much popularity and research interest in information and coding theory, networking, wireless communications and data storage. Random linear NC (RLNC) is a subclass of NC that has shown to be suitable for a wide range of applications thanks to its desirable properties, namely throughput-optimality, simple encoder design and efficient operation with minimum feedback requirements. However, for delay-sensitive applications, the mentioned advantages come with two main issues that may restrict RLNC usage in practice. First is the trade-off between the delay and throughput performances of RLNC, which can adversely affect the throughput-optimality of RLNC and hence the overall performance of RLNC. Second is the usage of feedback, where even if feedback is kept at minimum it can still incur large amount of delay and thus degrade the RLNC performance, if not optimized properly. In...