[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate the cost-effectiveness of Wi-Fi solution for vehicular Internet access. We define the cost-effectiveness as the cost saving by deploying and operating a low-cost Wi-Fi infrastructure instead of a costly benchmark cellular network. To characterize the service quality of Wi-Fi deployment, we also define the normalized service delay which is the service time to fulfill a data application via the Wi-Fi network normalized by that via the cellular network. To derive the service time, we analyze the average throughput capacity of a generic vehicle in the Wi-Fi network and the average downlink capacity in the cellular network. Especially, we propose deploying Wi-Fi access point at signalized intersection and study the fundamental influence of traffic signals (which yield an interrupted vehicle traffic) on Wi-Fi access. Then, we examine the tradeoff between cost-effectiveness and normalized service delay by identifying interplays between controllable (e.g., the density of Wi-Fi deployment and user's satisfaction) and uncontrollable parameters (e.g., vehicle traffic statistics). Our results are very useful for network operators to make strategic planning of Wi-Fi deployment for vehicular Internet Access.
[Show abstract][Hide abstract] ABSTRACT: The phenomenal growth of mobile data demand has brought about increasing scarcity in available radio spectrum. Meanwhile, mobile customers pay more attention to their own experience, especially in communication reliability and service continuity on the move. To address these issues, LTE-Unlicensed, or LTEU, is considered one of the latest groundbreaking innovations to provide high performance and seamless user experience under a unified radio technology by extending LTE to the readily available unlicensed spectrum. In this article, we offer a comprehensive overview of the LTEU technology from both operator and user perspectives, and examine its impact on the incumbent unlicensed systems. Specifically, we first introduce the implementation regulations, principles, and typical deployment scenarios of LTE-U. Potential benefits for both operators and users are then discussed. We further identify three key challenges in bringing LTE-U into reality together with related research directions. In particular, the most critical issue of LTE-U is coexistence with other unlicensed systems, such as widely deployed WiFi. The LTE/WiFi coexistence mechanisms are elaborated in time, frequency, and power aspects, respectively. Simulation results demonstrate that LTE-U can provide better user experience to LTE users while well protecting the incumbent WiFi users??? performance compared to two existing advanced technologies: cellular/WiFi interworking and licensed-only heterogeneous networks (Het-Nets).
[Show abstract][Hide abstract] ABSTRACT: An analytical model for studying the performance of the Delayed Acknowledgement (Dly-ACK) mechanism in IEEE 802.15.3 over wireless Rayleigh fading channel is developed. A three-state Markov chain is applied to approximate the correlated transmission errors. Explicit mathematical expressions for the goodput and efficiency of Dly-ACK are derived. It is found that the correlation between consecutive transmissions errors has significant impact on the goodput and efficiency of the Dly-ACK mechanism. The goodput tends to increase as the size of the Dly-ACK burst increases; however, the amount of increase depends on the underlying delay. Simulation results are given to validate the analytical results.
[Show abstract][Hide abstract] ABSTRACT: This article presents SOR, a vehicular social network to enable social communications and interactions among users on the road during their highway travels. Motivated by the limited connection to Internet contents and services, the essential goal of SOR is to encourage distributed users on the road to spontaneously contribute as the information producer, assembler, and distributer in order to provide timely and localized infotainments to each other through low-cost inter-vehicle communications. To be specific, SOR enables individual users to maintain a personal blog, similar to one on Facebook and Twitter, over which users can create and share personal content information to the public such as travel blogs with pictures and videos. By accessing each other???s SOR blogs and commenting on interesting topics, passengers can exchange messages and initiate social interactions. In the specific highway environment, SOR addresses two challenges in the context of vehicular social communications. First, vehicular social communications tend to be frequently interrupted by diverse vehicle mobility and intermittent intervehicle connections, which is annoying to users. To address this issue, SOR adopts a proactive mechanism by estimating the connection time between peer vehicles, and recommending vehicles with relatively long-lasting and stable intervehicle connections for social communications. Second, as users on the road are typically strangers to each other, they are reluctant to disclose personal information to others. This makes it challenging to identify users of shared interests and accordingly restricts the scale of users??? social interactions. To remedy that, SOR provides a secured solution to protect sensitive user information during social communications. Lastly, we use simulations to verify the performance of SOR.
[Show abstract][Hide abstract] ABSTRACT: Millimeter-wave communication is a promising technology for future 5G cellular networks to provide very high data rate (multi-gigabits-per-second) for mobile devices. Enabling D2D communications over directional mmWave networks is of critical importance to efficiently use the large bandwidth to increase network capacity. In this article, the propagation features of mmWave communication and the associated impacts on 5G cellular networks are discussed. We introduce an mmWave+4G system architecture with TDMA-based MAC structure as a candidate for 5G cellular networks. We propose an effective resource sharing scheme by allowing non-interfering D2D links to operate concurrently. We also discuss neighbor discovery for frequent handoffs in 5G cellular networks.
[Show abstract][Hide abstract] ABSTRACT: The supporting infrastructure and communications technologies for vehicular networking contexts are heterogeneous by nature. Large coverage access networks, such as 3G/4G, coexist with wireless local area networks and dedicated short-range communications. In such a scenario, we investigate the seamless provision of mobile Internet access and general IP services over the heterogeneous network, in particular for loosely coupling architectures. We propose a hybrid global mobility scheme that allows for the ongoing IP sessions to be transferred across dissimilar radio access networks that may belong to different administrative domains. In order to achieve the global mobility, our scheme combines host- and network-based mobility. The solution focuses on urban vehicular scenarios and enables seamless communications for in-vehicle networks, passengers with mobile devices, and users of public transportation commuting along the system. By means of analytical evaluations and simulations of realistic urban vehicular scenarios, we show that our hybrid scheme can achieve seamless IP communications for mobile Internet access over the heterogeneous vehicular network.
IEEE Transactions on Intelligent Transportation Systems 01/2015; DOI:10.1109/TITS.2015.2442251 · 2.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Since FCC's opening for white space (WS) utilization, database-assisted dynamic spectrum access (DSA) has become the de facto solution for the realization of dynamic spectrum sharing (DSS), due to its simplicity and compatibility with commercial off-the-shelf (COTS) devices. It is envisioned that such technology will strongly support the prosperous wireless multimedia networking (WMN) applications with satisfying QoS guarantees in the future. However, how to counter the time-frequency variant property when exploiting the WS spectrum for the provision of these services to secondary users (SUs) still remains a great challenge. In such context, a dynamic secondary access scheme for database-assisted spectrum sharing networks is proposed in this paper. In the beginning, the spectrum requirements of SUs for diverse services are modeled by considering the minimum required service data-rate and spectrum access duration. Afterwards, the spectrum demand evaluation and bidding policy are formulated based on the service classes of SUs. Furthermore, a double-phase (DP) spectrum allocation scheme, which consists of the initial resource allocation phase and resource allocation adjustment phase, is carefully designed for DSA. Finally, extensive simulations are conducted and the results demonstrate that our scheme can increase the spectrum trading revenue and adapt to varying service requirements.
Wireless Communication over ZigBee for Automotive Inclination Measurement. China Communications 01/2015; 12(1):66-77. DOI:10.1109/CC.2015.7084384 · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To satisfy the ever increasing wireless service demand, it is effective to form a converged network by utilizing interworking mechanisms, such that the resources of heterogeneous wireless networks can be allocated in a coordinated and efficient manner. Despite the potential advantages of a converged network, its performance needs further improvement, especially at cell edges and rural areas where only one network is available. In this article, we investigate how to leverage device-to-device, D2D, communication to further improve the performance of a converged network which consists of an LTE-A cellular network and IEEE 802.11n WLANs. Three main technical challenges that complicate resource allocation are identified: allocation of resources capturing diverse radio access technologies of the networks, selection of users' communication modes for multiple networks to maximize hop and reuse gains, and interference management. To address these challenges, we propose a resource allocation scheme that performs mode selection, allocation of WLAN resources, and allocation of LTE-A network resources in three different timescales. The resource allocation scheme is semi-distributedly implemented in the underlying converged D2D communication network, and the achievable performance improvements are demonstrated via simulation results.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we study the performance of mode selections in device-to-device (D2D) communications in terms of end-to-end average throughput, average delay, and dropping probability, considering dynamic data arrival with non-saturated buffers. We first introduce a general framework that includes three canonical routing modes, namely D2D mode, cellular mode, and hybrid mode, which can be combined with different resource allocation restrictions to represent the semi-static and dynamic selections of the three resource sharing modes. A queuing model is developed when the routing mode for every D2D connection is chosen, and an exact numerical analysis and an approximate decomposition and iteration approach are proposed. The performance measures are obtained from the decomposition approach and validated by means of simulation. We further introduce a mode selection scheme that adaptively chooses to semi-statically or dynamically select the resource sharing modes according to the estimated performance measures.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a novel base station (BS) coordination approach for intercell interference mitigation in the orthogonal frequency-division multiple access based cellular networks. Specifically, we first propose a new performance metric for evaluating end user's quality of experience (QoE), which jointly considers spectrum efficiency, user fairness, and service satisfaction. Interference graph is applied here to capture and analyze the interactions between BSs. Then, a QoE-oriented resource allocation problem is formulated among BSs as a local cooperation game, where BSs are encouraged to cooperate with their peer nodes in the adjacent cells in user scheduling and power allocation. The existence of the joint-strategy Nash equilibrium (NE) has been proved, in which no BS player would unilaterally change its own strategy in user scheduling or power allocation. Furthermore, the NE in the formulated game is proved to lead to the global optimality of the network utility. Accordingly, we design an iterative searching algorithm to obtain the global optimum (i.e., the best NE) with an arbitrarily high probability in a decentralized manner, in which only local information exchange is needed. Theoretical analysis and simulation results both validate the convergence and optimality of the proposed algorithm with fairness improvement.
[Show abstract][Hide abstract] ABSTRACT: Wireless Body Area Networks (WBANs), as a promising health-care system, can timely monitor human physiological parameters. Due to the limitation of communications, power, storage and computation in WBANs, a cloud assisted WBAN flourishes and provides more reliable, real-time, and intelligent health-care services for patients and mobile users. However, it is still critical to efficiently aggregate the different types of WBAN data to the cloud server. In addition, security and privacy concerns are also of paramount importance during the communications between WBAN and cloud. In this paper, we propose a priority based health data aggregation (PHDA) scheme with privacy preservation for cloud assisted WBANs to improve the aggregation efficiency among different types of health data. Specifically, we first explore social spots to help forward health data and enable users to select the optimal relay according to their social ties. According to different data priorities, the adjustable forwarding strategies can be selected to forward the user's health data to the cloud servers with the reasonable communication overheads. The security analysis demonstrates that the PHDA can achieve identity and data privacy preservation, and resist the forgery attacks. Finally, the performance evaluation shows that the PHDA achieves the desirable delivery ratio with reasonable communication costs and lower delay for the data in different priorities.
Information Sciences 11/2014; 284:130-141. DOI:10.1016/j.ins.2014.06.011 · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate the deficiency of uncontrolled asymmetrical transmission power over multiple channels in ad hoc environments. We further propose a novel distributed transmission power control protocol called the distributed power level (DPL) protocol for multi-channel ad hoc networks without requiring clock synchronization. Specifically, different transmission power levels are assigned to different channels, and nodes search for an idle channel on the basis of the received power so that the maximum allowable power of the preferred data channel is larger than or equal to the received power. If the most preferred channel of the least maximum power is busy, the nodes are able to select the next channel and so forth. As a result, interference is reduced over channels because the nodes that require higher transmission power are separated from interfering with the nodes that require lower transmission power. Two transmission power control modes are introduced for DPL: symmetrical and asymmetrical. For the symmetrical DPL protocol (mode), nodes transmit at the same power level assigned to the selected channel. On the other hand, for the asymmetrical DPL protocol, nodes are allowed to transmit at a lower or equal power level that is assigned to the selected channel. Extensive ns-2-based simulation results are presented to demonstrate that the proposed protocols can enhance the network throughput compared with the existing uncontrolled asymmetrical transmission power protocol. Copyright (C) 2012 John Wiley & Sons, Ltd.
Wireless Communications and Mobile Computing 10/2014; 14(14):1365-1381. DOI:10.1002/wcm.2266 · 1.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Energy saving is an important issue in Mobile Ad Hoc Networks (MANETs). Recent studies show that network coding can help reduce the energy consumption in MANETs by using less transmissions. However, apart from transmission cost, there are other sources of energy consumption, e.g., data encryption/decryption. In this paper, we study how to leverage network coding to reduce the energy consumed by data encryption in MANETs. It is interesting that network coding has a nice property of intrinsic security, based on which encryption can be done quite efficiently. To this end, we propose P-Coding, a lightweight encryption scheme to provide confidentiality for network-coded MANETs in an energy-efficient way. The basic idea of P-Coding is to let the source randomly permute the symbols of each packet (which is prefixed with its coding vector), before performing network coding operations. Without knowing the permutation, eavesdroppers cannot locate coding vectors for correct decoding, and thus cannot obtain any meaningful information. We demonstrate that due to its lightweight nature, P-Coding incurs minimal energy consumption compared to other encryption schemes.
IEEE Transactions on Parallel and Distributed Systems 09/2014; 25(9):2211-2221. DOI:10.1109/TPDS.2013.161 · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Smart grid has recently emerged as the next generation of power grid due to its distinguished features, such as distributed energy control, robust to load fluctuations, and close user-grid interactions. As a vital component of smart grid, demand response can maintain supply-demand balance and reduce users' electricity bills. Furthermore, it is also critical to preserve user privacy and cyber security in smart grid. In this paper, we propose an efficient privacy-preserving demand response (EPPDR) scheme which employs a homomorphic encryption to achieve privacy-preserving demand aggregation and efficient response. In addition, an adaptive key evolution technique is further investigated to ensure the users' session keys to be forward secure. Security analysis indicates that EPPDR can achieve privacy-preservation of electricity demand, forward secrecy of users' session keys, and evolution of users' private keys. In comparison with an existing scheme which also achieves forward secrecy, EPPDR has better efficiency in terms of computation and communication overheads and can adaptively control the key evolution to balance the trade-off between the communication efficiency and security level.
IEEE Transactions on Parallel and Distributed Systems 08/2014; 25(8):2053-2064. DOI:10.1109/TPDS.2013.124 · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In wireless data access applications, reduction of both the access latency and the wireless traffic volume is essential. In this paper, we propose a fast wireless data access scheme (FW-DAS) for wireless data access applications in which data objects are frequently updated and fast access to data objects is indispensable. In FW-DAS, different operation modes are defined depending on the data object popularity, and only popular data objects are proactively pushed to the access point/base station to minimize the access latency while mitigating the traffic load over the wireless link. An analytical model for the access latency is developed and an operation mode selection algorithm is introduced to reduce the access latency. Extensive simulation results show the effects of access-to-update ratio, data popularity, cache size, data object size, and wireless bandwidth. Analytical and simulation results demonstrate that FW-DAS can reduce the access latency with reasonable traffic load compared with poll-each-read (PER)/callback (CB) and their combinations.