Supeng Leng

An IEEE 802.11p-Based Multichannel MAC Scheme With Channel Coordination for Vehicular Ad Hoc Networks

In recent years, governments, standardization bodies, automobile manufacturers, and academia are working together to develop vehicular ad hoc network (VANET)-based communication technologies. VANETs apply multiple channels, i.e., control channel (CCH) and service channels (SCHs), to provide open public road safety services and the improve comfort and efficiency of driving. Based on the latest standard draft IEEE 802.11p and IEEE 1609.4, this paper proposes a variable CCH interval (VCI) multichannel medium access control (MAC) scheme, which can dynamically adjust the length ratio between CCH and SCHs. The scheme also introduces a multichannel coordination mechanism to provide contention-free access of SCHs. Markov modeling is conducted to optimize the intervals based on the traffic condition. Theoretical analysis and simulation results show that the proposed scheme is able to help IEEE 1609.4 MAC significantly enhance the saturated throughput of SCHs and reduce the transmission delay of service packets while maintaining the prioritized transmission of critical safety information on CCH.

Energy-Efficient Offloading for Mobile Edge Computing in 5G Heterogeneous Networks

Mobile edge computing (MEC) is a promising paradigm to provide cloud-computing capabilities in close proximity to mobile devices in fifth-generation (5G) networks. In this paper, we study energy-efficient computation offloading (EECO) mechanisms for MEC in 5G heterogeneous networks. We formulate an optimization problem to minimize the energy consumption of the offloading system, where the energy cost of both task computing and file transmission are taken into consideration. Incorporating the multi-access characteristics of the 5G heterogeneous network, we then design an EECO scheme, which jointly optimizes offloading and radio resource allocation to obtain the minimal energy consumption under the latency constraints. Numerical results demonstrate energy efficiency improvement of our proposed EECO scheme.

Performance Analysis of Connectivity Probability and Connectivity-Aware MAC Protocol Design for Platoon-Based VANETs

Vehicular ad hoc networks (VANETs) can provide safety and nonsafety applications to improve passenger safety and comfort. Grouping vehicles into platoons in VANETs can improve road safety and reduce fuel consumption. It is critical to design an efficient medium access control (MAC) protocol for platoon-based VANETs. Moreover, because of the space and time dynamics of moving vehicles, network connectivity is an important performance metric to indicate the quality of the network communications and the satisfaction of users. Unfortunately, network connectivity is often ignored in the design of existing MAC protocols for VANETs. In this paper, we study the connectivity characteristics and present a connectivity-aware MAC protocol for platoon-based VANETs. The connectivity probabilities are analyzed for vehicle-to-vehicle and vehicle-to-infrastructure communication scenarios in one- and two-way VANETs, respectively. A multipriority Markov model is presented to derive the relationship between connectivity probability and system throughput. Based on variable traffic status and network connectivity, a multichannel reservation scheme is adopted to dynamically adjust the length of the control channel interval and the service channel interval for the improvement of the system throughput. Analysis and simulation results show that the throughput increases with connectivity probability. However, with a further increase in connectivity probability, the throughput will decrease due to numerous channel contentions.

Architecture of Hybrid Mobile Social Networks for Efficient Content Delivery

Content delivery is one of the most important technologies used in Mobile Social Networks (MSNs). Smart devices could enable mobile users to create and use a rich set of services through available resources in the surrounding environment opportunistically. This paper presents the framework of distributed buffer storage aided hybrid Mobile Social Networks (MSN). Based on this, we propose a new scheme with distributed storage for efficient end-to-end content delivery in intermittently connected MSNs. Our proposed hybrid architecture is able to offer fast and reliable delivery services by distributing buffer storage located close to mobile users of the opportunistic MSN. Simulation experiments are conducted to evaluate the performance of the proposed method, which indicate that it is helpful to improve network performance in terms of content delivery ratio, throughput and end-to-end delays.

A novel k-hop Compound Metric Based Clustering scheme for ad hoc wireless networks

This paper presents a novel k-hop compound metric based clustering (KCMBC) scheme, which uses the host connectivity and host mobility jointly to select cluster-heads. KCMBC is a fast convergent and load balancing clustering approach that is able to offer significant improvement on scalability for large-scale ad hoc networks. On the other hand, since host mobility has been taken into account in terms of the average link expiration time, the clusters constructed by KCMBC are more stable than many other schemes. Simulation results show that the clusters created by using the KCMBC approach retain modest but more uniform cluster size, and cluster-head life-time can be increased by KCMBC up to 50%. Moreover, the control overheads for cluster formation using the KCMBC scheme are kept relatively low if compared to other clustering schemes.

Medium access control in vehicular ad hoc networks

The distinguishing properties of Vehicular Ad hoc wireless Networks (VANETs) strongly challenge the design of Medium Access Control (MAC) protocols, which are responsible for the medium access coordination among active vehicles, as well as the accommodation of both driving safety applications and non-safety applications. In this paper, we focus on a comprehensive survey of VANET MAC schemes by integrating various related issues and challenges. Our analysis not only deepens the understanding of MAC techniques in VANETs but also presents the key ideas and potential directions for future research in this area. In order to significantly improve the communication performance of VANETs, more research efforts on MAC techniques must be made for optimizing multichannel coordination and allocation approaches, enhancing the Quality of Service (QoS) capability, and combating the hidden terminal problem, broadcast storm problem and even ACK (acknowledgment) explosion problem. Copyright

A dynamic bandwidth allocation algorithm in mobile networks with big data of users and networks

Data collection has become easy due to the rapid development of both mobile devices and wireless networks. In each second, numerous data are generated by user devices and collected through wireless networks. These data, carrying user and network related information, are invaluable for network management. However, they were seldom employed to improve network performance in existing research work. In this article we propose a bandwidth allocation algorithm to increase the throughput of cellular network users by exploring user and network data collected from user devices. With the aid of these data, users can be categorized into clusters and share bandwidth to improve the resource utilization of the network. Simulation results indicate that the proposed scheme is able to rationally form clusters among mobile users and thus significantly increase the throughput and bandwidth efficiency of the network.

A Carrier Aggregation Based Resource Allocation Scheme for Pervasive Wireless Networks

The mixture of users with different bandwidth capability presents new challenges to optimize the transmission performance of the next generation wireless networks. This paper focuses on resource allocation for pervasive wireless networks with component carrier (CC) aggregation. Distinguished from many existing methods that decompose the resource optimization problem into two sequence steps, i.e., CC scheduling and resource block (RB) assignment on each carrier, we develop a novel joint CC and RB allocation algorithm to maximize network utility, namely Minimizing System Utility Loss (MSUL) algorithm. Numerical results indicate that MSUL is able to improve the system performance in terms of network utility, average throughput and fairness compared with the algorithms optimizing CCs and RBs allocation separately.

Data and Energy Integrated Communication Networks for Wireless Big Data

This paper describes a new type of communication network called data and energy integrated communication networks (DEINs), which integrates the traditionally separate two processes, i.e., wireless information transfer (WIT) and wireless energy transfer (WET), fulfilling co-transmission of data and energy. In particular, the energy transmission using radio frequency is for the purpose of energy harvesting (EH) rather than information decoding. One driving force of the advent of DEINs is wireless big data, which comes from wireless sensors that produce a large amount of small piece of data. These sensors are typically powered by battery that drains sooner or later and will have to be taken out and then replaced or recharged. EH has emerged as a technology to wirelessly charge batteries in a contactless way. Recent research work has attempted to combine WET with WIT, typically under the label of simultaneous wireless information and power transfer. Such work in the literature largely focuses on the communication side of the whole wireless networks with particular emphasis on power allocation. The DEIN communication network proposed in this paper regards the convergence of WIT and WET as a full system that considers not only the physical layer but also the higher layers, such as media access control and information routing. After describing the DEIN concept and its high-level architecture/protocol stack, this paper presents two use cases focusing on the lower layer and the higher layer of a DEIN network, respectively. The lower layer use case is about a fair resource allocation algorithm, whereas the high-layer section introduces an efficient data forwarding scheme in combination with EH. The two case studies aim to give a better explanation of the DEIN concept. Some future research directions and challenges are also pointed out.

Joint Scheduling and Beamforming Coordination in Cloud Radio Access Networks With QoS Guarantees

The cloud radio access network (C-RAN) is a promising architecture for future radio access networks (RANs) due to its advantages in cost efficiency, flexibility, and utilization efficiency. To fully reap these benefits, this paper focuses on joint optimization of user grouping, virtual base station (VBS) clustering, and transmit beamforming in C-RAN downlink networks for maximizing the system utility, subject to the diverse quality-of-service (QoS) requirements of users and the power constraints of distributed remote radio heads (RRHs). To tackle the high computational complexity in solving the nonconvex combinatorial optimization problem, a two-stage solution is proposed. Specifically, a dynamic user-centric scheduling algorithm is developed to form user groups and cluster RRHs into VBSs by exploiting the nonuniform distribution of users. Then, an iterative transmit beamformer optimization algorithm is devised to coordinate the transmit beamforming among the VBSs to mitigate the intracell and intercell interference, hence further enhancing the overall system utility. Evaluation results demonstrate that the proposed algorithm achieves significant performance gain over various reference algorithms in terms of system utility, system throughput, and energy efficiency.