Vehicular ad-hoc networks (VANETs) have been widely studied in intelligent transportation. Content delivery is an important topic that attracts many researchers. Due to vehicles that may have intermittent connections and uncertain routes, it is difficult to select an appropriate node. In this paper, we analyze the movement pattern of vehicles from real taxis’ trajectories and propose a framework for delivery prediction, which aims to select appropriate nodes. First, we propose the framework which consists of a contact clique model, a social clique model, and a prediction model based on Markov chains, to characterize the movement pattern of vehicles. Second, we capture dynamic movement patterns by dividing the time requirement into equal length slots and construct clique sequences. Based on the fact that the sociality of nodes has strong temporal correlations, we utilize the prediction model to derive future cliques and evaluate two kinds of delivery performance in the future. Finally, we design a content delivery algorithm with dynamic movement pattern (DMP) to select the appropriate node. In our experiment, DMP performs better than that of other methods in terms of overhead, average hops. Also, as the number of nodes increases, our algorithm keeps small fluctuations in node sociality.

In most existing wireless networks, end users obtain data content from the wired network, typically, the Internet. In this manner, virtually all of their traffic must go through a few access points, which implies that the capacity of wireless network is limited by the aggregated transmission data rate of these access points. To fully exploit the capability of wireless network, we envision that future wireless networks shall be able to provide data content within themselves. In this paper, we address the behavior of such networks from a theoretical perspective. Specifically, we consider that multicast is used for distributed content delivery, and we investigate the asymptotic upper bound of the throughput capacity for distributed content delivery in large-scale wireless ad hoc networks (DCD-WANET). Our analysis shows how the upper bound of throughput capacity is affected by the geometric size of the network, the number of data items, the popularity of the data content, and the number of storage nodes that contain those data items. In particular, our theoretical results show that, if the number of storage nodes exceed a critical threshold, the upper bound grows with the number of storage nodes, according to a power-law where the scaling exponent depends on the popularity of data items. We also provide the data item placement strategy to achieve the upper bound of throughput capacity for DCD-WANET.

In this paper, we investigate the throughput capacity of large-scale wireless networks, in which three network-assisted coding schemes are considered: (1) multi-point-to-point coding (MPPC); (2) MPPC based network coding (NC); and (3) MPPC based physical-layer network coding (PLNC). This study is based on the generalized physical model, in which the transmission rate depends on the signal to noise and interference ratio (SINR). Such a model has not been used to analyze the behaviors of large-scale wireless networks with the aforementioned coding schemes. To understand the capacity gains of these schemes, we develop constructive lower bounds for one-dimensional (1D) and two-dimensional (2D) networks with size factor w, in which we construct novel wireless highway systems. This study shows that, compared to point-to-point coding (PPC), MPPC can improve the scaling law of network capacity when w exceeds a certain scale. In addition, this study reveals that MPPC based NC and PLNC can improve the capacity by constant factors. Specifically, NC can always obtain a gain of 2 in both 1D and 2D networks. On the other hand, the gain of PLNC can be larger than 2 in 1D networks, and can be up to 2 in 2D networks, depending on w, transmission power, noise, and path-loss of propagation.

Due to the broadcast nature of wireless channels, the two-way system can be eavesdropped on when a confidential message is transmitted, which is one of the motivations of this paper. While most of existing work focuses on the discussion of secrecy rate with information theoretical approach, this paper discusses the probability of successful detection for the system experiencing exponential path loss. By investigating the symbol-error-rate at the legitimate nodes and eavesdropper, we find the optimal power allocation among the two-way communication systems. We also investigate the impact factor on the secrecy capacity including the location of eavesdropper, path loss exponent, and decoding strategies.

In the past few years, the capacity of multicast traffic in large-scale random wireless networks has attracted considerable attention because of the fundamental importance of network capacity and the multicast applications. However, there are still significant gaps between the upper bounds and the constructive lower bounds. In this paper, we develop a novel percolation highway system with which the constructive lower bounds can arbitrarily approach the upper bounds.

Physical-layer network coding (PLNC) is a novel wireless communication technology, in which multiple transmitters can send signals on the same channel to the same receiver at the same time. Our previous studies have revealed that PLNC can substantially improve the throughput performance of the whole network. In this paper, we address the security performance of PLNC. In particular, we investigate the symbol error performance of a potential eavesdropper in the PLNC system. Extensive simulation studies show that PLNC can provide security means against passive eavesdroppers.

In this paper, we address the topology control issue for future wireless mesh networks (WMNs). In particular, we propose a novel topology control scheme that attempts to maximize the overall throughput in the network with random unicast traffic demands. The main idea of the scheme is to establish multiple semi-permanent wireless highways, each of which can convey the traffic for nodes along the highways. To evaluate the performance of the proposed scheme, we conduct theoretical analysis, which demonstrates that viable solutions for highways do exist with high probability. The theoretical analysis also proves the optimality. Within the new topology control framework, we demonstrate that advanced technologies, including network coding and physical- layer network coding (PLNC), can be applied to substantially improve the throughput capacity of the network.

In this paper, we focus on the problem of effectively supporting a large number of small group multicasts in optical burst switched (OBS) networks. We first propose a multicast scheme for small group multicast in OBS networks. To reduce burst loss due to potential burst contentions, a deflection routing scheme for multicast is proposed. We then develop an analytical model to evaluate the performance of the multicast scheme and the deflection routing scheme. To the best of our knowledge, this is the first analytical model proposed for the problem of multicast with deflection routing. The model is very general in the sense that it can handle unicast traffic, multicast traffic, and the mixture of unicast and multicast traffic, with or without deflection routing. The analytical model is verified through simulations. Numerical results show that the analytical model is accurate, and that, under low or medium network load, deflection routing for multicasting can significantly reduce burst loss while slightly increasing burst delay.

In this paper, we study the design of future wireless ad hoc networks. Particularly, we consider that the future wireless ad hoc networks shall be able to efficiently provide connectivity and support a variety of quality of service requirements, such as bandwidth and delay requirements. To address these issues, we propose a novel framework for the design of future wireless ad hoc networks. The key idea of this framework is to establish an overlay hypernetwork, which consists of multiple hyperchannels, each of which can provide connectivity for multiple nodes in the hyperchannel. By comparison, a typical tunnel in existing overlay network schemes can only provide connectivity for two end nodes. Within the framework, we also develop advanced network coding design that can further improve the performance of the network in terms of throughput and delay.

In recent years, grid computing applications are becoming more and more important to the scientific and business communities. For many grid applications that require the exchange of a huge amount of data, optical networks are the nature choices because they can provide tremendous bandwidth. In our previous study, we have shown that anycast routing scheme can efficiently support many emerging high-performance grid applications in OBS networks. In this paper, we first design a label-based control framework for anycast routing in all-optical networks. We then develop an analytical model to evaluate the performance of the proposed anycast scheme. Extensive simulation and numerical results show that our analysis is rather accurate. Moreover, both simulation and analysis demonstrate that the anycast scheme can significantly improve the performance of grid applications, in terms of both loss and delay performance.

In this paper, we focus on the problem of effectively supporting a large number of small group multicasts in optical burst switched (OBS) networks. We first propose a multicast scheme for small group multicast in OBS networks. To reduce burst loss due to potential burst contentions, a deflection routing scheme for multicast is proposed. We then develop a generic analytical model to evaluate the performance of the multicast scheme and the deflection routing scheme. To the best of our knowledge, this is the first analytical model proposed for the problem of multicast with deflection routing. The analytical model is verified through simulations. Numerical results show that the analytical model is accurate and that deflection routing can significantly reduce burst loss probability while slightly increasing burst delay.

Packet contention is a major issue in asynchronous optical packet switching networks. Optical buffering, which is implemented by fiber delay lines (FDLs), is fundamental to many optical switch implementations for resolving contention. Most existing optical buffering implementations are output-based and require a huge amount of FDLs as well as larger switch sizes, which impose extra cost on the overall system. In this paper, we consider a shared optical buffering architecture which can reduce the buffer size at a switch. We propose an analytical model to evaluate the packet loss probability and the average delay For shared buffers at a single switch. We then compare the performance of output buffers to shared buffers under different granularities of FDLs. We observe that, by choosing an appropriate granularity, the shared buffering scheme can significantly reduce packet loss with much smaller switch sizes and fewer FDLs than the output buffering architecture. The accuracy of the analytical model is also confirmed by extensive simulation.

Packet contention is a major issue in asynchronous optical packet and burst switching networks. Optical buffering, which is implemented by fiber delay lines (FDLs), is fundamental to many optical switch implementations for resolving contention. Most existing optical buffering implementations are output-based and require a huge amount of FDLs as well as larger switch sizes, which impose extra cost on the overall system. In this paper, we consider shared optical buffering which can reduce the buffer size at a switch. Since no previous study is available to analyze the performance of asynchronous architectures with shared buffers, we propose an analytical model to evaluate the packet loss probability and the average delay for shared buffers at a single switch. We then compare the performance of output buffers to shared buffers under different granularities of FDLs. We observe that, by choosing an appropriate granularity, the shared buffering scheme can significantly reduce packet loss with much smaller switch sizes and fewer FDLs than the output buffering architecture. The accuracy of the analytical model is also confirmed by extensive simulation.

In this paper, we provide a new analytical model for evaluating the blocking performance of dynamic lightpath establishment in multifiber wavelength-routed networks. By adopting the simple link-independent model together with the wavelength correlation assumptions, we manage to achieve a good balance between analytical accuracy and computational complexity. Extensive numerical results show that the proposed model can quickly produce accurate analytical results under different traffic loads and in different networks.

In this paper, we propose a framework for providing differentiated contention resolution in photonic packet-switched networks by exploiting recirculation buffering and deflection routing. We develop an analytical model to evaluate the packet loss probability and the end-to-end delay for different buffering and deflection routing schemes, and we investigate the effectiveness of the control schemes in providing differentiated loss and delay. The accuracy of the analytical model is confirmed by simulation.

We address the problem of efficient circuit switching in wide area optical networks. The solution provided is based on finding optimal routes for lightpaths and the new concept of semilightpaths. A lightpath is a fully optical transmission path, while a semilightpath is a transmission path constructed by chaining together several lightpaths, using wavelength conversion at their junctions. A fast and practical algorithm is presented to optimally route lightpaths and semilightpaths taking into account both the cost of using the wavelengths on links and the cost of wavelength conversion. We prove that the running time of the algorithm is the best possible in the wide class of algorithms allowing linear algebraic operations on weights. This class encompasses all known related practical methods. Additionally, our method works for any physical realization of wavelength conversion, independently whether it is done via optoelectronic conversion or in a fully optical way.

The virtual path (VP) concept is known to be a powerful transport mechanism for ATM networks. This paper deals with the optimization of the virtual paths system from a bandwidth utilization perspective. While previous research on VP management has basically assumed that bandwidth in ATM networks is unlimited, emerging technologies and applications are changing this premise. In many networks, such as wireless, bandwidth is always at a premium. In wired networks, with increasing user access speeds, less than a dozen of broadband connections can saturate even a Gigabit link. We present an efficient algorithm that finds a system of VP routes for a given set of VP terminators and VP capacity demands. This solution is motivated by the need to minimize the load, or reduce congestion, generated by the VP's on individual links. A nontrivial performance guarantee is proven for the quality of the proposed solution and numerical results show that the proposed solution carries the potential for a near optimal allocation of VPs.>