Yuliang Tang

An enhanced GPSR routing protocol based on the buffer length of nodes for the congestion problem in VANETs

Vehicular ad hoc networks technology is an important part of intelligent transportation system which has wide developmental and applied prospect. The routing protocol is a key technology of vehicular ad hoc networks and largely determines the performance of the vehicle network communication system. Vehicular ad hoc networks (VANETs) makes great requests to routing protocol due to several reasons: firstly, vehicle nodes moving into tubular mobile states which are limited in road. Then, nodes moves fast, network topology changes frequently, the relationship among nodes becomes unstable. Aiming at the network congestion problem exists in commonly used GPSR routing protocols of current vehicular ad hoc networks, this paper proposed an improved project of GPSR routing protocol which controls network congestion based on the buffer of nodes. Performance simulation for relevant parameters is tested on platform NS2. From the results of the analysis, the enhanced GPSR protocol in vehicles environment has lower packet loss rate and less time delay than the traditional GPSR protocol.

A multi-channel cooperative clustering-based MAC protocol for VANETs

Vehicular ad-hoc networks (VANET) have attracted much attention from both academia and industry. However, it is very challenging to design an efficient MAC protocol to meet QoS demands of different applications in VANETs, because of the unreliable channel and node mobility. On the other hand, cooperative communication has been proved effective to mitigate wireless channel impairments and increase the reliability of communications. In this paper, a multi-channel cooperative clustering-based MAC protocol is presented to improve the reliability of transmission and provision QoS for different applications in VANETs. The performance of this scheme is verified through mathematical analysis and simulations.

A novel joint centralized scheduling and channel assignment scheme for IEEE 802.16 mesh networks

IEEE 802.16 standard defines a broadband wireless access network technology, which provides a mechanism for creating multi-hop wireless mesh network. As multiple-access interference is a major limiting factor for the IEEE 802.16 mesh network, multi-channel transmission can eliminate the interference and improve the performance of the network. The efficiency of the multi-channel transmission can be affected by the scheduling and channel-assignment scheme. To reap the full performance potential of the network, we propose a novel combined centralized scheduling and channel assignment algorithm for multi-channel single-transceiver IEEE 802.16 mesh network. The performance evaluation results show that the proposed scheme can improve the system performance in aspects of scheduling length and the BSs aggregate throughput in insufficient channels.

A novel cooperative MAC for broadcasting in clustering VANETs

In VANETS, a variety of services can be provided, including safety-related applications, traffic management and user infotainment services. Out of all these applications, safety-related applications are the most important ones and they mainly depend on the broadcast service. However, it is a challenging task to provide a reliable broadcast in VANETs, because of the mobility of vehicles and the unreliability of wireless channels. On the other hand, cooperative communication has been proved effective to mitigate wireless channel impairments and increase the reliability of communications. In this paper, a cooperative MAC for broadcasting is proposed in clustering VANETs. This MAC can improve the reliability of broadcasting. The performance of this MAC is verified through mathematical analysis and simulations.

Map-based multi-path routing protocol in VANETs

Due to vehicle movement and propagation loss of radio channel, providing a routing protocol for reliable multihop communication in VANETs is particularly challenging. In this paper, we present a map-based multi-path routing protocol for VANETs - MBMPR, which utilizes GPS, digital map and sensors in vehicle. With global road information, MBMPR finds an optimal forward path and an alternate path using Dijkstra algorithm, which improves the reliability of data transmission. Considering the load balance problem in junctions, a congestion detection mechanism is proposed. Aiming at the packet loss problem due to target vehicles mobility, MBMPR adopts recovery strategy using location-based services and target vehicle mobility prediction. The simulations demonstrate MBMPR has significant performances comparing with classical VANETs routing protocols.

A cross-layer handover management scheme for SIP-based VoWLAN

Session Initiation Protocol (SIP) has already been accepted as the multimedia control signaling standard in ubiquitous wireless network by IETF and 3GPP etc. However, the handover procedure with SIP suffers from undesirable delay for real-time multimedia applications in WLAN. Moreover, the existing handover management protocols are not sufficient to guarantee handover of VoIP session in WLAN. In this paper, a cross-layer handover management architecture (CHM-SIP) is developed to shorten the service interruption time when the mobile node frequently handovers between subnets of WLAN. Based on this architecture, the detailed design of a cross-layer handover management for Voice over WLAN (VoWLAN) based SIP is carried out, which uses mobiles speed and handover signaling delay information to enhance the handover performance. The theoretical analysis and simulation results show that CHM-SIP significantly enhances the VoWLAN handover performance.

A resource collaboration scheduling scheme in ultra-dense small cells

Ultra-dense network (UDN) is expected to be the main means of meeting the mobile traffic demands in 5G. Small cell is the main load of UDN to save energy and enhance coverage. However, the resource conflict become much more complicated than the conventional cellular system, because of the dense and random deployment and the dynamical switch of small cells, and the changeable users. Therefore, this paper proposes a resource collaboration scheduling scheme (RCS) in ultra-dense small cells. Simulation results show that proposed RCS scheme improves the network throughput and user satisfaction by dynamically allocating resources in ultra-dense small cells.

A novel algorithm of virtual resource allocation in heterogeneous radio access networks

The existing radio access network system is static and rigid which could not satisfy the communication requirements of the modern society - flexibility, mobility and intelligence. This paper studies the problems of virtualized resource allocation with multi-objective mapping in heterogeneous radio access network. First, a mathematical model of the multi-objective mapping for virtualized resources is established for heterogeneous radio access network. Next, the dynamic differential evolutionary algorithm is used to solve the multi-objective model. During the process, the weight values of objective function are adjusted by machines learning algorithm, so as to realize the result that the unilaterally value of multi-objective optimization is close to the value of solo-objective optimization. Finally, simulated experiment shows that the proposed algorithm has good fast convergence in different network load scenarios.

A new multipath AODV routing protocol for VANET based on expected link lifetime

In Vehicular Ad Hoc Networks (VANETs), the node mobility leads to network topology changed frequently. Due to the vehicle movement, the limited wireless resources and channel fading, the routing protocols in Mobile Ad Hoc Networks MANETs are not suitable for VANETs. In this paper we propose a new multipath route protocol based on Ad hoc On-Demand Distance Vector Routing (AODV) for adapting VANETs environment called Enhanced Multipath AODV (EMP-AODV). EMP-AODV use a node-disjoint multipath strategy to set up routing and choose routing to transmission based on a link expected link lifetime algorithm. The simulation results show that our proposed protocol reduces the end-to-end delay and packet loss ratio while improving the network throughput in VANETs.

Design and implementation of SIP B2BUA server

The SIP(Session Initiation Protocol) is the core control protocol of the Next Generation Networks(NGN), which is used for initiating, modifying and tearing down multimedia sessions on IP data network. Because the SIP server is the core facility of NGN, its realization is especially important. One way to realize the SIP server is the proxy server, which mainly provides routing service. Namely, it ensures that request message will be sent to place that is closest to target user. However, the proxy server just keeps the state during the SIP interaction instead of the state during call process, which causes that the proxy server is limited to be used in more wide range. Another way is the B2BUA server, which keeps the state during the whole call process. So, at first, the Resiprocate is introduced from the basic principle of the SIP protocol in this paper, and the B2BUA server is realized. Then, taking advantage of the advantage of the B2BUA server, the group call system based on the B2BUA server is realized. At last, this paper use the SIPp, a open software which is specially used to test the SIP system, to test and analysis the performance of the B2BUA server.