Ren-Hung Hwang

Multicast Routing Based on Genetic Algorithms

Due to the advent of many new multimedia applications in high speed networks, the issue of multicast routing has become more and more important. The multicast routing problem in computer networks is also known as the Steiner tree problem which has been shown to be NP-complete. In this paper, we propose a new multicast routing algorithm based on Genetic Algorithms. To apply this algorithm to real networks, we also propose several methods for reducing the computational complexity. Computer simulations were conducted on a random graph to evaluate the performance of the proposed algorithm. Our numerical results show that the proposed algorithm is able to find a better solution than the RSR algorithm, a very promising heuristic algorithm for the Steiner tree problem proposed by Rayward-Smith. Finally, since many multimedia applications require multiple Quality of Service (QOS) constraints, such as delay, jitter, and loss probability, we also address how to extend the proposed algorithm to obtain multiple constrained multicast trees.

MDP routing in ATM networks using virtual path concept

The virtual path (VP) concept has been proposed to simplify traffic control and resource management in future B-ISDN. In particular, call setup processing can be significantly reduced when resources are reserved on VPs. However, this advantage is offset by a decrease in statistical multiplexing gains of the networks. The focus of this paper is on how to improve bandwidth efficiency through adaptive routing when capacity is reserved on all VPs. The authors first examine two VP capacity reservation strategies. They then design and evaluate computationally feasible Markov decision process-based routing algorithms and show that the network blocking probability can be significantly reduced by MDP routing.<<ETX>>

SSIP: Split a SIP session over multiple devices

Recently, most of Voice over Internet applications are based on the Session Initiation Protocol (SIP). This paper addresses issues of allowing a user to continue to communicate with a remote party while changing terminals over multiple devices. Specifically, we propose an SIP extension header to improve the Call Transfer mechanism and hide the changing of the terminal from the remote party. We also propose a mechanism to solve the problem of the user needing to terminate all devices separately when a session is split over multiple devices. Finally, the proposed mechanisms are implemented using Sip-Communicator, an open source of SIP.

QoS routing granularity in MPLS networks

This study investigates how constraint-based routing decision granularity significantly affects the scalability and blocking performance of QoS routing in an MPLS network. Coarse granularity, such as per-destination, has lower storage and computational overheads but is only suitable for best effort traffic. On the other hand, fine granularity, such as per-flow, provides lower blocking probability for bandwidth requests, but requires a huge number of states and high computational cost. To achieve cost-effective scalability, this study proposes using hybrid granularity schemes. The overflowed cache of the per-pair/flow scheme adds a per-pair cache and a per-flow cache as the routing cache, and performs well in blocking probability. The per-pair/class scheme groups the flows into several paths using routing marks, thus allowing packets to be label-forwarded with a bounded cache.

Multicast routing with multiple QoS constraints in ATM network

Abstract Recently, more and more applications provide multiparty communication services, e.g., video conferencing, distance learning, etc. Therefore, the routing problem of multicast with multiple quality of service (QoS) constraints becomes more important. For example, in order to ensure smooth play back of audio and video data, a video conference requires guarantee on both end-to-end delay and loss probability. In this paper, we solve the multiple-constraint multicast problem by extending three single-constraint Steiner tree algorithms: (1) the constrained shortest path tree (CSPT), (2) the algorithm proposed by Kompella, Pasquale, and Polyzos (KPP), and (3) the bounded shortest multicast algorithm (BSMA). We also propose a novel multiple-constraint multicast routing algorithm based on genetic algorithms, called MCMGA. These four algorithms are evaluated via simulations on different sizes of random graphs. Our numerical results show that, in most cases, MCMGA yields solutions of the least cost. The costs of the solutions obtained by our extended BSMA are also very competitive.

Seamless session mobility scheme in heterogeneous wireless networks

The next generation wireless communication system will likely be heterogeneous networks, as various technologies can be integrated on heterogeneous networks. A mobile multiple-mode device can easily access the Internet through different wireless interfaces. The mobile multiple-mode device thus could switch to different access points to maintain the robustness of the connection when it can acquire more resources from other heterogeneous wireless networks. The mobile multiple-mode device therefore needs to face the handover problem in such environment. This work introduces Session Initiation Protocol (SIP)-based cross-layer scheme to support seamless handover scheme over heterogeneous networks. The proposed scheme consists of a battery lifetime-based handover policy and cross-layer fast handover scheme, called the SIP-based mobile stream control transmission protocol (SmSCTP). This work describes the major idea of the proposed scheme and infrastructure. The proposed scheme has been implemented in Linux system. The simulation and numerical results demonstrate that the proposed SmSCTP scheme yields better signaling cost, hand-off delay time, packet loss and delay jitter than SIP and mSCTP protocols. Copyright

Cross-layer design vehicle-aided handover scheme in VANETs

The requirement for in-vehicle passengers to access Internet multimedia services has risen recently. As a consequence, Vehicle Ad hoc NETwork (VANET) has gained much attention, and is regarded as a promising solution for providing in-vehicle Internet service through inter-vehicle and infrastructure communication. A new developed wireless network technique, termed WiMAX Mobile Multihop Relay (MMR), provides a good communication framework for a VANET formed from vehicles on high-speed freeways. Applying MMR WiMAX allows some public transportation vehicles to act as relay vehicles (RVs) to provide Internet access to passenger vehicles. However, the standard handover procedure of mobile or MMR WiMAX suffers long delay due to the lack of information about the next RV. This study presents a cross-layer fast handover scheme, called vehicular fast handover scheme (VFHS), where the physical layer information is shared with the MAC layer, to reduce the handover delay. The key idea of VFHS is to utilize oncoming side vehicles (OSVs) to accumulate physical and MAC layers information of passing through RVs and broadcast the information to vehicles that are temporarily disconnected, referred to as disconnected vehicles (DVs). A DV can thus perform a rapid handover when it enters the transmission range of one of approaching RVs. The effectiveness of VFHS is verified using ns2 simulations. Simulation results indicate that VFHS significantly decreases handover latency and packet loss. Copyright

P2P File Sharing System over MANET based on Swarm Intelligence: A Cross-Layer Design

The dynamic nature of MANET causes many challenges in designing robust and scalable P2P system. Although flooding-based techniques are shown to be robust in highly dynamic network, it leads to poor efficiency in terms of bandwidth usage and scalability. In this paper, we propose an efficient and scalable P2P file sharing system based on swarm intelligence for MANET, referred to as P2PSI. By applying the behavior of the real ant colonies, P2PSI owns the capability of adaptive learning and is able to cope with mobility problem without flooding. Moreover, we also present a cross-layer architecture for P2PSI to reduce the redundant message overhead and query latency. Performance of our cross-layer design P2PSI is compared with two existing cross-layer design service discovery protocols, namely, CLdsr and CLdsr through simulations. The simulation results show that our cross-layer design P2PSI achieves better performance in terms of control overhead, request success ratio, and path length.

LLR routing in homogeneous VP-based ATM networks

In ATM networks, a virtual path (VP) concept has been proposed to simplify traffic control and resource management. As a consequence, cell routing becomes more flexible and significant call setup processing can be reduced when resources are reserved on VPs. In this paper, we study the routing problem in homogeneous VP-based ATM networks in which VPs are used for traffic segregation such that all VCs in a VP have the same traffic characteristics and QOS requirement. Four adaptive routing algorithms based on the least loaded routing (LLR) concept are designed and evaluated. Our simulation results show that network blocking probability can be significantly reduced by LLR routing.

A buffer-aware HTTP live streaming approach for SDN-enabled 5G wireless networks

With increasing interest in the concept of 5G wireless networks and the popularization of mobile devices, users gradually watch videos through mobile devices in streaming mode rather than off-line mode. However, the latency and lags of mobile networks will reduce the quality of service. In HTTP live streaming services, when there are multiple sources for the same content stored in the streaming servers, the suited quality content is able to be selected for playing according to the networking bandwidth conditions between servers and user equipment, and the users can obtain appropriate streaming quality automatically. However, the selection policy is difficult to be approved between 5G wireless communication networks and SDNs. In this study a buffer-aware HTTP live streaming approach is proposed, which evaluates the weights of media segments to decide the transmitting priorities based on the current playing time and adjust the appropriate transmission path through the decision making network controller according to the utilization and stability of the routers and switches in SDN. Finally, the experimental results proved that the approach is able to correct the overall streaming source sequence with the buffer status to effectively upgrade overall streaming service quality, as well as maintain a certain level of streaming quality for SDN-enable 5G wireless networks.