Network coding with link layer cooperation in wireless mesh networks

Practical wireless network coding (e.g., COPE) is a promising technique that can enhance the throughput of wireless networks. However, such a technique also bears a serious security drawback: it breaks the current privacy-preserving protocols (e.g., Onion Routing), since their operations conflict each other. As user privacy in wireless networks is highly valued nowadays, a new privacy-preserving scheme that can function with wireless network coding becomes indispensable. To address such a challenge, we apply the idea of cooperative networking and design a novel anonymity scheme named ANOC, which can function in network-coding-based wireless mesh networks. ANOC is built upon the classic Onion Routing protocol, and resolves its conflict with network coding by introducing efficient cooperation among relay nodes. Using ANOC, we can perform network coding to achieve a higher throughput, while still preserving user privacy in wireless mesh networks. We formally show how ANOC achieves the property of relationship anonymity, and conduct extensive experiments via nsclick to demonstrates its feasibility and efficiency when integrated with network coding.

Recent studies show that network coding can provide significant benefits to network protocols, such as increased throughput, reduced network congestion, higher reliability, and lower power consumption. The core principle of network coding is that intermediate nodes actively mix input packets to produce output packets. This mixing subjects network coding systems to a severe security threat, known as a \emph{pollution attack}, where attacker nodes inject corrupted packets into the network. Corrupted packets propagate in an epidemic manner, depleting network resources and significantly decreasing throughput. Pollution attacks are particularly dangerous in wireless networks, where attackers can easily inject packets or compromise devices due to the increased network vulnerability.In this paper, we address pollution attacks against network coding systems in wireless mesh networks. We demonstrate that previous solutions to the problem are impractical in wireless networks, incurring an unacceptably high degradation of throughput. We propose a lightweight scheme, DART, that uses time-based authentication in combination with random linear transformations to defend against pollution attacks. We further improve system performance and propose EDART, which enhances DART with an optimistic forwarding scheme. A detailed security analysis shows that the probability of a polluted packet passing our verification procedure is very low. Performance results using the well-known MORE protocol and realistic link quality measurements from the Roofnet experimental testbed show that our schemes improve system performance over 20 times compared to previous solutions.

A recent approach--COPE, presented by Katti et al. (Proc. ACM SIGCOMM 2006, pp. 243-254)--for improving the throughput of unicast traffic in wireless multihop networks exploits the broadcast nature of the wireless medium through opportunistic network coding. In this paper, we analyze throughput improvements obtained by COPE-type network coding in wireless networks from a theoretical perspective. We make two key contributions. First, we obtain a theoretical formulation for computing the throughput of network coding on any wireless network topology and any pattern of concurrent unicast traffic sessions. Second, we advocate that routing be made aware of network coding opportunities rather than, as in COPE, being oblivious to it. More importantly, our model considers the tradeoff between routing flows close to each other for utilizing coding opportunities and away from each other for avoiding wireless interference. Our theoretical formulation provides a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput. We handle scheduling of broadcast transmissions subject to wireless transmit/receive diversity and link interference in our optimization framework. Using our formulations, we compare the performance of traditional unicast routing and network coding with coding-oblivious and coding-aware routing on a variety of mesh network topologies, including some derived from contemporary mesh network testbeds. Our evaluations show that a route selection strategy that is aware of network coding opportunities leads to higher end-to-end throughput when compared to coding-oblivious routing strategies.

A Wireless Mesh Network (WMN) is a multi-hop network that gains the benefits of low deployment cost, fast access speed, expanded service coverage and large network capacity. However, the multi-hop communication in WMNs limits the throughput capacity due to increased number of packet transmissions. As a result, network coding is a recently emerged paradigm that can enhance the throughput capacity (i.e. network throughput) by minimizing the quantity of network workload and at the same time it ensures the data transfer among all the users. Further, with network coding the transmission effectiveness of a node can be improved by encoding (combining) several packets collectively and verifies whether the coding strategies is satisfied or not. Subsequently, if the coding strategies are satisfied then it transmits only the resultant encoded packet to the desired destination. In other words, network coding can improve the network throughput in WMNs by minimizing the transmission counts needed to transfer several packets to the destination. It should be noted that, while employing network coding in WMNs there are several challenges that should be compensated such as (i) identifying packets that can be combined (encoded) collectively and (ii) integrating the coding strategies in routing protocols. In this paper, we proposed a new mesh routing protocol that integrates network-coding called as Network Coding Aware Routing (Net-CART) protocol. Therefore, to enjoy the whole benefit of network coding a Net-CART protocol uses the innovative routing metric called Code-Aware and Load-Aware Routing Metric. Additionally, to identify numerous ‘coding structures’ and to support number of ‘packet encodings’ an improved set of coding strategies known as Enhanced Universal Coding Strategies is also proposed. The proposed Net-CART protocol comprising an improved set of coding strategies and a new routing-metric considers both the coding-opportunities and “network workload”. The simulation study carried out in wide forms of network configurations showed that Net-CART gives more fairness performances than other protocols.

The IEEE 802.16 standard (WiMAX) specifies a MeSH mode which permits the deployment of Wireless Mesh Networks (WMNs) supporting carrier‐grade QoS. The network operator for such planned WMNs is interested in maximizing the traffic admitted in the WMN and simultaneously supporting QoS. Recently network coding has emerged as a promising technique for increasing the throughput in WMNs. This paper proposes CORE, which addresses the problem of jointly optimizing the routing, scheduling, and bandwidth savings via network coding. Prior solutions are either not applicable in the 802.16 MeSH mode or computationally too costly to be of practical use in the WMN under realistic scenarios. CORE's heuristics, in contrast, are able to compute solutions for the above problem within a operator definable maximum computational cost, thereby enabling the computation and near real‐time deployment of the computed solutions. We analyze the performance of CORE's heuristics via a thorough simulation study covering the typical usage scenarios for WMNs. The results presented demonstrate that CORE is able to increase the number of flows admitted considerably and with minimal computational costs. We also see that CORE successfully increases the number of network coding sessions which can be established in the WMN. Further, the results provide insights into limiting factors for the gains which can be obtained in different typical usage scenarios for WMNs. Copyright © 2010 John Wiley & Sons, Ltd.

This paper studies the interplay between network coding and spatial reuse in wireless mesh networks. We present a method that attempts to maximize the system performance by exploiting effectively (and not greedily) coding opportunities through appropriate routing and achieving efficient spectrum reuse through opportunistic link scheduling. We show that judiciously selecting coding structures requires proper transmission power allocation to better manage cumulative interference in the network, and thus yield better spectrum spatial reuse and effective multi-hop system throughput. We present an optimization model for this complex design problem, which relies on the enumeration of all possible schedules and decompose it into subproblems which we can solve more efficiently. Our numerical results indicate that optimal joint coding and scheduling with proper power allocation yields a performance enhancement of more than 10% over that with maximal power transmission and more than 45% enhancement over a coding oblivious design model. Our results also revealed that network coding has only marginal benefits (~6%) in a dense network and that in such networks managing interference through proper power allocation yields very good performance.

Wireless Mesh Networks (WMNs) provide a novel network architecture to extend broadband network coverage with low costs. Additionally, we see an increased interest in supporting demanding multimedia applications in next-generation wireless mesh networks. Provision of Quality of Service (QoS) in wireless mesh networks requires end-to-end support for routing packets via a suitable multihop route to the destination. However, in wireless mesh networks, if the medium access control layer does not support mechanisms for QoS support at a per-link level, all efforts for providing end-to-end QoS are futile. Hence, we see a trend towards standards for wireless mesh networks which support QoS at the Medium Access Control (MAC) level on a per-link basis.

Network coding has recently been applied to wireless networks and has achieved some initial success. Researches in wireless network coding have been mostly focusing on utilizing the broadcast nature of the wireless networks. In this paper, we propose a novel network coding framework for wireless relay networks that also takes into consideration the fading and error prone nature of the wireless networks. First, we extend the traditional network coding in lossless networks which operates on 0-1 bits, to a new framework which defines network coding on the posterior probability of each bit. This new framework allows an imperfect decode-recode process at a relay node and avoids possible error propagation when a hard decision is made at the relay node. It implicitly integrates decode-and-forward and estimate-and-forward strategies for wireless network coding to address the technical issues of channel fading and transmission errors. The proposed approach is validated through both theoretical analysis and extensive simulations. Both analysis and simulation confirm that this new framework is able to achieve significant gain over traditional network coding. This new framework also enables the introduction of adaptive scheme into network coding. We demonstrate a basic adaptation scheme and present some preliminary experimental results. The proposed adaptive scheme will lay down an essential foundation in this emerging field of wireless network coding in order to address issues related to link heterogeneity.

A wireless mesh network is a mesh network implemented over a wireless network system such as wireless LANs. Wireless Mesh Networks(WMNs) are promising for numerous applications such as broadband home networking, enterprise networking, transportation systems, health and medical systems, security surveillance systems, etc. Therefore, it has received considerable attention from both industrial and academic researchers. This dissertation explores schemes for resource management and optimization in WMNs by means of network routing and network coding. In this dissertation, we propose three optimization schemes. (1) First, a triple-tier optimization scheme is proposed for load balancing objective. The first tier mechanism achieves long-term routing optimization, and the second tier mechanism, using the optimization results obtained from the first tier mechanism, performs the short-term adaptation to deal with the impact of dynamic channel conditions. A greedy sub-channel allocation algorithm is developed as the third tier optimization scheme to further reduce the congestion level in the network. We conduct thorough theoretical analysis to show the correctness of our design and give the properties of our scheme. (2) Then, a Relay-Aided Network Coding scheme called RANC is proposed to improve the performance gain of network coding by exploiting the physical layer multi-rate capability in WMNs. We conduct rigorous analysis to find the design principles and study the tradeoff in the performance gain of RANC. Based on the analytical results, we provide a practical solution by decomposing the original design problem into two sub-problems, flow partition problem and scheduling problem. (3) Lastly, a joint optimization scheme of the routing in the network layer and network coding-aware scheduling in the MAC layer is introduced. We formulate the network optimization problem and exploit the structure of the problem via dual decomposition. We find that the original problem is composed of two problems, routing problem in the network layer and scheduling problem in the MAC layer. These two sub-problems are coupled through the link capacities. We solve the routing problem by two different adaptive routing algorithms. We then provide a distributed coding-aware scheduling algorithm. According to corresponding experiment results, the proposed schemes can significantly improve network performance.

To protect user privacy in wireless mesh networks (WMNs), it is important to address two major challenges, namely: flow untraceability and movement untraceability, which prevent malicious attackers from deducing the flow paths and the movement tracks of mobile devices. For these two privacy requirements, most existing approaches rely on encrypting the whole packet, appending random padding, and applying random delay for each message at every intermediate node, resulting in significant computational and communication overheads. Recently, linear network coding (LNC) has been introduced as an alternative but the global encoding vectors (GEVs) of coded messages have to be encrypted so as to conceal the relationships between the incoming and outgoing messages. In this paper, we aim to explore the potential of LNC to ensure the flow untraceability and movement untraceability. Specifically, we first determine the necessary and sufficient condition, with which the two privacy requirements can be achieved without encrypting either GEVs or message contents. We then design a deterministic untraceable LNC (ULNC) scheme to provide flow untraceability and movement untraceability when the sufficient and necessary condition is satisfied. Finally, we discuss the effectiveness of the proposed ULNC scheme against traffic analysis attacks in WMNs.

Recently, it has been proven that retransmission based on Network Coding (NC) can greatly improve the performance of wireless networks with broadcast erasure channels. However, network coding also introduces additional delay at the both sending and receiving sides, resulting in the decline of the Quality of user Experience (QoE). In this paper, we consider the users' waiting time and the decoding delay as the performance metrics and then propose MixCode, a NC-based loss recovery method, to improve the delay performance in heterogeneous wireless networks. MixCode incorporates Opportunistic Network Coding (ONC) with Random Linear Network Coding (RLNC), where a NC packet can be decoded by simply XORing operation at some destinations, but by Gaussian elimination at other destinations. Simulation results show that our proposed algorithm can efficiently reduce both the waiting time and the decoding delay in comparison with the existing NC-based schemes.

Resource allocation and admission control algorithm based on non-cooperation game in wireless mesh networks

Wireless Mesh Networks (WMNs) integrate the advantages of WLANs and mobile Ad Hoc networks, which have become the key techniques of next-generation wireless networks in the context of emergency recovery. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with instant deployment, self-healing, self-organization and self-configuration features. These capabilities make WMNs a promising technology for incident and emergency communication. An incident area network (IAN) needs a reliable and lively routing path during disaster recovery and emergency response operations when infrastructure-based communications and power resources have been destroyed and no routes are available. Power aware routing plays a significant role in WMNs, in order to provide continuous efficient emergency services. The existing power aware routing algorithms used in wireless networks cannot fully fit the characteristics of WMNs, to be used for emergency recovery. This paper proposes a power aware routing algorithm (PARA) for WMNs, which selects optimal paths to send packets, mainly based on the power level of next node along the path. This algorithm was implemented and tested in a proven simulator. The analytic results show that the proposed power node-type aware routing algorithm metric can clearly improve the network performance by reducing the network overheads and maintaining a high delivery ratio with low latency.

Network coding technology is always employed to improve the throughput of Wireless mesh networks (WMNs). However, traditional routing protocols based on network coding can only passively wait for coding opportunity, and the routing process is oblivious to coding operation. Taking into account the high throughput requirement in WMNs, a novel Coding awareness routing protocol with maximum benefit (CARMB) is proposed in this paper. The CARMB could actively create potential coding opportunities in the process of path establishment, which attempts to choose an appreciated route with more coding benefits among available path candidates. Simulations through NS-2 demonstrate that the CARMB performs better than traditional schemes in enhancing average end-to-end throughput and increasing coding opportunities as well as reducing average end-to-end delay. In particular, average end-to-end throughput and coding gain could be improved by 11% and 17% respectively compared with previous approaches.

Scalable video applications have been gaining popularity during last years. Providing high quality video over wireless networks towards heterogeneous receivers is a challenging task due to erratic and time-varying nature of a wireless channel. Compressed video bit-streams, such as Scalable Video Coding (SVC), are very vulnerable to channel disturbances when transmitted over error-prone wireless channels. Transmission errors not only corrupt the current frame, but also propagate to next frames along motions prediction path. In this paper we propose a novel scheme for transmission of SVC-based streams over Wireless Mesh Network (WMN) with Unequal Error Protection (UEP) based on Appropriate Path Selection (APS) and Network Coding (NC). The scheme tries to select appropriate paths based on Grey Relational Analysis (GRA) for different SVC layers. It chooses the best path for most important layer, base layer, and less stable paths for enhancement layers. Some nearby nodes along the transmission path are selected for recoding their received packets and store them in buffers for some period of time. The nearby nodes coded packets can be transmit to receivers for recovering the lost packets.