Efficient network coding-based end-to-end reliable multicast in multi-hop wireless networks

This paper studies joint scheduling and network coding in wireless multicast networks with independent sources. Designing a network coding solution for wireless networks involves scheduling interference-free transmissions and optimizing a performance measure for the predetermined scheduling sets, followed by constructing network codes for the specific solution. In such a design process, the results of prior steps need to provide enough information to the subsequent steps. In this paper, we formulate a linear optimization problem whose results can be used to design a coding solution. We build our work on previous works and present statistics that show the importance of incorporating unequal timeshares in designing network codes. In particular, our statistics show a throughput improvement of about 35% in maximum flow problems and energy savings between 13% and 30%, depending on the network size, in minimum energy problems. We also present the requirements of code construction algorithms for wireless networks that capture the broadcast property of these networks and can design proper codes when timeshares are unequal. In particular, the adaptation of a centralized network coding scheme for wireless networks is discussed. Overall, the work reported here provides a three-step solution to derive network codes that optimize a performance criterion of interest while also solving the scheduling problem in multihop wireless networks.

This paper addresses the Quality of Service (QoS) degradation problem of wireless relay node failures in multihop Worldwide interoperable Microwave Access (WiMAX) and Long Term Evolution (LTE) networks. In general, node protection in a communication network increases the reliability of the traffic flow from source to destination. For wireless networks, implementing the traditional 1+1 protection scheme increases the capital cost, as resources cannot be fully utilized. On the other hand, the design and implementation of the 1:N protection scheme in wireless networks for greater value of N (> 2) is very difficult, due to wireless network coverage and the physical layer design. To overcome the above drawbacks, a technique based on network coding is proposed for node protection in multihop wireless networks. In multihop wireless networks, few research efforts are concentrated on node protection schemes using network coding. Moreover, to best of our knowledge, no reports have been published on measuring the QoS performance for node protection in 4G wireless networks using network coding. In this paper, we first describe the node protection scheme using XOR network coding for multihop 4G wireless networks. Then, we measure the QoS performance, such as packet delivery ratio (PDR), latency and jitter, for different scenarios. The scenarios include a failure of a single relay node and failures of two relay nodes with and without our protection scheme and user's mobility. The simulation results show that the QoS performance with protection against a single relay node failure and failures of two relay nodes are very close to that of no failure scenario, while the network reliability increases due to the protection mechanism. Also, we report a decoding problem in multihop wireless networks using XOR network coding.

In this paper, we investigate the problem of network coding and media scheduling in wireless multihop networks. Unique characteristics of the wireless media, such as omnidirectional transmissions and destructive interference, as well as having one transceiver per wireless node, imply new code design constraints for wireless networks. Here, we formulate a linear program to solve the joint scheduling and network coding problem. Using our formulation, we demonstrate that for a large percentage of randomly generated wireless networks, the optimal scheduling time shares are unequal. All the existing network code design algorithms are based on equal scheduling time shares or the considered joint optimization problems do not have sufficient information for scheduling flows during unequal time shares. Therefore, we provide these statistics to emphasize the importance of enabling the code design algorithms to include unequal time shares. Our simulations further show that the network throughput can be significantly improved if the network code is properly designed to incorporate unequal time shares.

Cyber-Physical System (CPS) is envisioned to tightly integrate the cyber-world of computation, communication, and control with the physical world. CPS is typically designed as a networked system of interacting sensors, actuators, and embedded computing devices to monitor and control the physical world. Thus, one of the essential building blocks of such a system is a highly efficient networking infrastructure. In this paper, we aims to develop an efficient wireless networking technology which can be utilized in CPS. More specifically, we develop a cross-layer optimization model based on the Network Utility Maximization (NUM) framework and its distributed solution for wireless multihop multicast networks exploiting multi-user diversity. It is known that the capacity of a wireless network can be increased by exploiting different channel conditions at different users, i.e., multi-user diversity; however, it is yet to be determined how much performance gain can be achieved by exploiting multi-user diversity in wireless multihop multicast networks. To address this problem, we extend the NUM framework and derive a new optimization problem including the benefits of multi-user diversity for multicasting scenarios in wireless multihop networks under a probabilistic media access control (MAC). In our problem, multi-user diversity is achieved via opportunistic scheduling. Then, we propose a distributed approximation algorithm for the problem. Our numerical results confirm that the benefit of multi-user diversity is prominent in a wireless multihop network with multicast flows.

Network coding (NC) is an efficient way to decline the retransmission and provides a reliable connection in the wireless multicast network. However, in the NC schemes based on XOR, if one coded packet is lost, the transmitter must retransmit the same one until all the receivers correctly receive it. This strategy falls into the routine of ARQ (Automatic Repeat Request), which has already been proved with low bandwith efficiency. Accordingly, in this paper we proposed a dynamic linear combining retransmission(DLCR) strategy and fixed linear combining retransmission (FLCR) strategy based on the random network coding to improve the bandwidth efficiency in wireless multicast network. The key idea of the proposed schemes is to form the coded packet dynamically according to the real-time network status during the retransmission. Besides, we also analyzed the proposed schemes and get the corresponding theory analysis results. The simulations show that our schemes can well improve the efficiency of transmission.

Traditional fixed pricing mode limits the accepted number of users and traffic flows in networks. This results in low profits for operators. By applying appropriate pricing strategies, wireless radio resources can be utilized more adequately, and promising improvement of operation profits can be achieved. In this paper, a dynamic pricing strategy for delay tolerant service aggregation multicast in wireless networks is proposed. With this strategy, client behaviors are well adjusted by differentiation of prices, and the congestions in peak-traffic periods can be well relieved, leading to increments of operators' profits. Simulation results show that our proposed dynamic pricing scheme outperforms existing pricing schemes, with regard to service rejection rate and operation profits.

Achieving optimal transmission throughput in data networks is known as a fundamental but hard problem. The situation is exacerbated in multi-hop wireless networks due to the interference among local wireless transmissions. In this paper, we propose a general modeling and solution framework for the throughput optimization problem in wireless networks. In our framework, data routing, wireless medium contention and network coding are jointly considered to achieve the optimal network performance. The primal-dual solution method in the framework represents a cross-layer optimization approach. It decomposes the original problem into data routing sub-problems at the network layer, and power allocation sub-problems at the physical layer. Various effective solutions are discussed for each sub-problem, verifying that our framework may handle the throughput optimization problem in an efficient and distributed fashion for a broad range of wireless network scenarios.

The increasing use of multi-hop wireless networks and the growing demand of bandwidth-intensive multimedia applications are the driving force to explore innovative techniques that can enhance the capacity of multi-hop wireless networks. The commonly used omni-directional antennas limit the spatial reusability of the wireless channel and hence reduce the available capacity of wireless networks. On the contrary, bandforming antennas, that enable directional transmissions and receptions, can overcome the aforementioned limitation. With the recent advances in signed processing and antenna technologies, smart beamforming antennas have become feasible in compact sizes and suitable prices and hence pertinent to multi-hop wireless networks. However, lack of appropriate control over the antenna beamforming may deteriorate the overall performance even below the level achieved by omni-directional antennas. Moreover, beamforming antennas introduce unprecedented challenges including deafness and directional hidden terminal problems. Hence, it is important to design efficient mechanisms for both Medium Access Control (MAC) and routing to deal with these challenges that hinder the full exploitation of spatial reusability offered by smart beamforming antennas. In this dissertation, we develop an analytical framework for modeling directional contention-based MAC protocols, which is, up to our knowledge, the first model to include deafness in the analysis. We show that deafness can severely limit the network capacity. Based on the insights gained from our analysis of the limitations of the existing solutions, we propose a novel opportunistic directional MAC protocol for multi-hop wireless networks with beamforming antennas. The proposed MAC protocol employs a new backoff mechanism that aims at minimizing the unnecessary idle waiting time, which is a key factor in leveraging the spatial reuse. Through extensive simulations, we demonstrate that the proposed MAC protocol enhances the performance in terms of throughput, delay, packet delivery ratio and fairness. We have also addressed the question about the theoretical capacity gain achieved by beamforming antennas. We derive a generic interference model that can accommodate any antenna radiation pattern and show that the capacity gain is significant even when realistic antenna radiation patterns are used. Since smart beamforming antennas can significantly spare the network resources, they can be utilized to provide Quality of Service (QoS) guarantees. We study the bandwidth-guaranteed routing problem in contention-based multi-hop wireless networks with beamforming antennas. We first present an analysis for the wireless links interdependencies in a contention-based environment in the presence of beamforming, which helps in our formulation of the QoS routing problem as a mixed-integer non-linear optimization problem. We then propose a routing and admission control algorithm for its solution. Our simulation results demonstrate the accuracy of our analysis and the ability of our proposed algorithm to find bandwidth-guaranteed routes. In summary, the analysis and design approaches, adopted in this dissertation, enhance the throughput of multi-hop wireless networks by grasping the transmission opportunities offered by smart beamforming antennas while dealing with the beamforming-related challenges at the MAC and network layers, which otherwise limit the spatial reusability of the wireless channel.

Network Coding (NC) has been a solution scheme for data exchange in communications that amalgamate data packets, especially in multi-hop wireless networks. Existing studies demonstrated the use of NC in wireless networks by evaluating its key advantages. The store-code-forward approach of network coding at relay nodes brings out the most relevant benefits in the performance metrics, such as power, throughput, and goodput in communication. COPE is a fundamental protocol, which exploits link diversity and the broadcast nature of a wireless medium using the XOR criteria for data packet amalgamation. COPE is unsuccessful in the exploration of maximum compatibility packets through which opportunistic routing can be maximized. Hence, to identify maximum compatibility packets at relay nodes, the paper presents the uses of Artificial Bee Colony (ABC) optimization algorithm integrated with shortest path planning technique for optimal routing. The authors have successfully demonstrated the validation of Routing-aware Heuristic-based Opportunistic Network Coding (RHONC) mechanism in the multi-hop wireless network. The paper evaluates the proposed mechanism, and enhances throughput gain, goodput gain, and reduced energy consumption against COPE.

In this paper, we consider a wireless multicast network with multiple sources, relays, and destinations. We adopt a multi-hop decode-and-forward relay protocol such that two canonical subnetworks are relevant, namely broadcast channel with receiver side information (BC-RSI) and orthogonal multiple access channel with correlated sources and receiver side information (MAC-CS-RSI). A joint network and channel coding (JNCC) strategy is proposed by exploiting ARQ, RSI, and correlated sources. The proposed JNCC strategy does not require the knowledge of RSI nor any transmit channel state information, such that each transmitter simply performs retransmissions until the intended receivers have accumulated enough mutual information to successfully decode all desired messages. This successful decoding is then conveyed from the receivers to the respective transmitters via an acknowledgement message. To measure the performance of the proposed JNCC strategy with ARQ, we derive closed-form expressions of network throughput by applying the renewal-reward theorem. Analytical results show that the proposed JNCC strategy outperforms, in terms of network throughput, the conventional separate network and channel coding strategy with random linear network coding.

Network coding is a technology with great potentiality in improving wireless multi-hop network throughput. And some routings combined with network coding have been proposed for wireless multi-hop network. In the routings combined with network coding, network coding condition is used to find network coding opportunities, which is very important to the performance improving of routings combined with network coding. However, the network coding conditions defined by existing routings combined with network coding unilaterally focus on the growth of network coding opportunities, which results in the increasing of cost and delay in routing discovery. Moreover, the more flows participating network coding, the higher probability of decoding failure, which degrade the network coding gain. In this paper, low complexity network coding condition (LCNC) is proposed. LCNC only detects two-flows network coding opportunity, and ensures the destination make successful decoding. In addition, the actual network coding gain is designed through analysis of link quality. Network coding opportunity will be ignored in case the actual network coding gain is negative. Based on LCNC, a low complexity network coding aware routing (LNCR) is designed aiming wireless multi-hop network. Simulation results demonstrate that LNCR obtain a balance between network coding gain and routing discovery cost, and can obtain higher network throughput when the network load is high compared with the classical network coding aware routings.

Privacy threat is one of the critical issues in multi-hop wireless networks, where attacks such as traffic analysis and flow tracing can be easily launched by a malicious adversary due to the open wireless medium. Network coding has the potential to thwart these attacks since the coding/mixing operation is encouraged at intermediate nodes. However, the simple deployment of network coding cannot achieve the goal once enough packets are collected by the adversaries. On the other hand, the coding/mixing nature precludes the feasibility of employing the existing privacy-preserving techniques, such as Onion Routing. In this paper, we propose a novel network coding based privacy-preserving scheme against traffic analysis in multi-hop wireless networks. With homomorphic encryption on Global Encoding Vectors (GEVs), the proposed scheme offers two significant privacy-preserving features, packet flow untraceability and message content confidentiality, for efficiently thwarting the traffic analysis attacks. Moreover, the proposed scheme keeps the random coding feature, and each sink can recover the source packets by inverting the GEVs with a very high probability. Theoretical analysis and simulative evaluation demonstrate the validity and efficiency of the proposed scheme.

In this letter, we consider a wireless network where the transmitter, such as a base station, multicasts hard-deadline-constrained prioritized data to users over fading channels. We propose a new cross-layer transmission scheme that involves simultaneous smart antenna beamforming at physical layer and random network coding at network layer to maximize the overall network throughput. In this joint design, beamforming is used for dynamic transmitting power allocation to achieve power gain; while the random network coding is adopted to achieve coding gain. The simulation results show the effectiveness of the proposed algorithm.

Network coding is an effective idea to boost the capacity of wireless networks, and a variety of studies have explored its advantages in different scenarios. However, there is not much analytical study on throughput and end-to-end delay of network coding in multi-hop wireless networks considering the specifications of IEEE 802.11 Distributed Coordination Function. In this paper, we utilize queuing theory to propose an analytical framework for bidirectional unicast flows in multi-hop wireless mesh networks. We study the throughput and end-to-end delay of inter-flow network coding under the IEEE 802.11 standard with CSMA/CA random access and exponential back-off time considering clock freezing and virtual carrier sensing, and formulate several parameters such as the probability of successful transmission in terms of bit error rate and collision probability, waiting time of packets at nodes, and retransmission mechanism. Our model uses a multi-class queuing network with stable queues, where coded packets have a non-preemptive higher priority over native packets, and forwarding of native packets is not delayed if no coding opportunities are available. Finally, we use computer simulations to verify the accuracy of our analytical model.

This chapter provides some examples that demonstrate the usefulness of network coding in wireless networks. It discusses the use of network coding for end-to-end multicasting. The chapter examines how to practically apply network coding for multicasting in multihop wireless networks. It shows that for wireless networks there are many ways to provision the network resource and uses various optimization formulations to determine an efficient resource allocation. The chapter explains how network coding can be used as a generic technology that improves the link layer efficiency by exploiting the broadcast nature of the wireless medium. It also discusses some physical layer techniques that are based on the mixing and demixing of signals. The chapter provides an overview of the theory and practice of network coding in wireless networks. It also shows how to obtain convex optimization formulations for network coding-based multicasting in wireless networks. The chapter describes the core components of random linear mixing-based multicasting protocols.