Abu S. Reaz

A Survey of User Behavior in VoD Service and Bandwidth-Saving Multicast Streaming Schemes

As broadband networks using Fiber-to-the-x (FTTx) technologies are being increasingly deployed in access networks, video service, especially VoD (Video-on-Demand), is becoming more attractive to deploy. To provide efficient VoD service, a cost-effective service model is very important and a lot of research has been conducted over the past decade. This paper reviews the existing literature on this topic, focusing on the user behavior in VoD services and bandwidth-saving multicast streaming schemes, which are the most important aspects of VoD service. First, we review the user behavior in VoD such as video popularity, daily access pattern, and interactive VCR (Videocassette Recorder) properties from recent data. Each video titles rental frequency, i.e., video popularity, follows the Zipf distribution, and this popularity can change with time or by service providers recommendation of videos. This overall request frequency for each video constitutes a specific pattern throughout the day and has a similar pattern every day. Second, we review the bandwidth-saving streaming schemes such as broadcasting, batching, patching, and merging, which use multicast streaming technologies and user buffer memory. We review the mechanism of each multicast streaming technology and compare their differences. We also review the recent trends on multicast streaming technologies, which is summarized as hybrid architecture which combines several multicast streaming technologies to obtain better performance. Next, we review how these multicast streaming technologies implement interactive VCR functions. We classify the VCR interactivity into discontinuous and continuous VCR actions and examine the principles for VCR support in multicast streaming schemes: caching some video data for discontinuous VCR support and allocating contingency channels for continuous VCR support. We review mechanisms of VCR support for different multicast streaming schemes. Through this survey, we provide an in-depth understanding of VoD service deployment.

CaDAR: An Efficient Routing Algorithm for a Wireless–Optical Broadband Access Network (WOBAN)

A wireless-optical broadband access network (WOBAN) is a combination of wireless and optical network segments to optimize the cost and performance of an access network. A WOBANs optical backhaul enables it to support high capacity, while its wireless front end [also called a wireless mesh network (WMN)] enables its users to have untethered access. Wireless nodes collect traffic from end users and carry them to the optical part of a WOBAN, possibly using multiple hops, but the traffic also experiences delay at each wireless node. The finite radio capacity at each wireless node limits the capacity on each outgoing link from a wireless node of a WOBAN. Thus, delay and capacity limitation in the WMN of a WOBAN are major constraints. We design a capacity- and delay-aware routing scheme, called CaDAR, to minimize the delay and increase the throughput in the WMN of a WOBAN. Our analysis shows that CaDAR is an efficient routing scheme for WOBAN that can support much higher load and has lower system delay than other approaches (IEEE Network, vol. 22, no. 3, p. 20, 2008) because of better load-balanced routing.

Survey and classification of transport layer mobility management schemes

Mobility of Internet hosts allows computing nodes to move between subnets. Mobility can be handled at different layers of the protocol stack, with network and transport layer mobility being the most widely studied. Transport layer mobility can overcome many of the limitations of network layer schemes like mobile IP. Various approaches have been proposed to implement mobility in the transport layer. In this paper, we discuss a number of transport layer mobility schemes, classify them according to their approach, and compare them based on a number of evaluation criteria

Signalling cost analysis of SINEMO: seamless end-to-end network mobility

IETF has proposed Mobile IPv6-based Network Mobility (NEMO) basic support protocol (BSP) to support network mobility. NEMO BSP inherits all the drawbacks of Mobile IPv6, such as inefficient routing path, single point of failure, high handover latency and packet loss, and high packet overhead. To address these drawbacks, we proposed an IP diversity-based network mobility management scheme called Seamless IP-diversity based NEtwork MObility (SINEMO). In this paper, we develop an analytical model to analyze and compare the signalling costs of SINEMO and and NEMO BSP. Our analysis shows that SINEMO reduces the signalling cost by a factor of two when compared to NEMO BSP.

CaDAR: An Efficient Routing Algorithm for Wireless-Optical Broadband Access Network

Hybrid wireless-optical broadband access network (WOBAN) is a combination of wireless and optical networks to optimize the cost and performance of an access network. Wireless nodes collect traffic from end users and carry them to the optical part of a WOBAN using multiple hops, accumulating delay at each wireless node. Moreover, the radio capacity on each wireless link limits the capacity on each outgoing link from the node in a single-radio wireless mesh network (WMN) of a WOBAN. Thus, delay and capacity limitation in the WMN of a WOBAN is a major bottleneck. We design a capacity and delay aware routing scheme, CaDAR, to minimize the delay and increase network support in the WMN of a WOBAN. Our analysis shows that CaDAR is an efficient routing scheme for a single-radio WMN for a WOBAN that can support much higher load and has lower system delay than other approaches because of better load balanced routing.

Link Scheduling and Power Control in Wireless Mesh Networks with Directional Antennas

Directional antennas are very attractive in wireless mesh networks (WMN). We study the problem of link scheduling and power control in a time-division multiple access (TDMA) WMN where the nodes use directional antennas. This is a cross- layer design problem spanning the physical and the link layers. Link scheduling in WMNs requires careful modeling of interference. Interference models used for omni-directional antennas cannot be used for directional antennas. We develop a generalized interference model applicable to directional antennas. Then, we use this model to formulate the link scheduling and power control problem as a Mixed Integer Linear Program. We also propose a heuristic algorithm to solve the problem efficiently.

Channel, capacity, and flow assignment in wireless mesh networks

We study the problem of channel capacity, and flow assignment (CCFA) in multi-channel wireless mesh networks (WMNs). CCFA involves the joint assignment of channels, distribution of wireless capacity, and determination of link flows to enhance the effectiveness of WMNs. We first study the capacity assignment (CA) problem in WMNs (WMN-CA) which involves the distribution of wireless capacity, given the topology and the flows (i.e., traffic demands and routing). Unlike wired networks, the capacities of different wireless links in a WMN have to be carved out of the capacities of wireless nodes. Since the wireless medium is shared by various wireless nodes, interference between different wireless links constrains the distribution of the wireless capacity available at individual nodes. We formulate WMN-CA as a convex non-linear optimization problem (NLP). We also present efficient heuristics to solve the problem and compare their relative performance. We then propose a linear programming (LP) based iterative algorithm for CCFA. We define a new metric, called network utility, which takes both throughput and average packet delay into account and includes a parameter that can be used to emphasize one over the other. Our approach has two separate phases - (1) channel assignment and (2) multi-channel capacity and flow assignment. The two phases of the iterative CCFA algorithm are performed repeatedly to improve the network utility which allows for a tradeoff between delay and throughput that can be achieved in a WMN.

Hybrid Wireless-Optical Broadband Access Network (WOBAN): Capacity Enhancement for Wireless Access

Noting that the optical part of a hybrid wireless- optical broadband access network (WOBAN) has high capacity, we need to enhance the capacity for wireless access using a low-cost solution. Our prior work developed a solution where each wireless node was equipped with a single radio. Deploying multiple radios, say two, at each node will improve the performance of wireless access, but this will also increase the cost of the solution. However, deploying multiple radios at only a few nodes, especially those that are overloaded with traffic, can lead to a less-costly solution, possibly without sacrificing performance. Hence, we study how to optimally place a limited number of additional radios at the wireless nodes to save the overall network cost. We formulate this problem as an Integer Linear Program (ILP) and solve it using a standard solver such as CPLEX. As expected, by deploying multiple radios at bottleneck wireless nodes, we can obtain almost the same performance as a WOBAN with multi-radios at all nodes.

Performance of DNS as location manager for wireless systems in IP networks

Domain name system (DNS) can be deployed in the network as a location manager (LM) for mobility management. The suitability of domain name system (DNS) as an LM can be measured by how successfully it can serve to locate a mobile host. In this paper, we developed an analytical model to measure the performance of DNS as LM for mobility management techniques with IP diversity support based on success rate which takes into account the radius of the subnet, the residence time of MH in that subnet, latency in the network and the overlapping distance of two neighboring subnets. Our analysis shows that for a reasonable overlapping distance, DNS can serve as an LM with very high success rate even under some high network latency.

Optimal Capacity Allocation in Wireless Mesh Networks

We address the problem of ldquocapacity allocationrdquo in wireless mesh networks (WMNs). In the ldquocapacity allocationrdquo problem, the network topology (namely the desired wireless links) and routing are given. The problem then is to assign capacities to different links (which are carved out of the radio capacity of a wireless node) in such a way that the average network delay is minimized. This classic problem has been solved by Kleinrock for wired networks subject to a cost constraint. The problem of capacity allocation in wireless networks is different because of the following reasons: i) the capacity of a wireless radio is limited by the physical-layer technology; ii) wireless channel is a shared medium; and iii) the overall capacity of the wireless network is limited by interference. These unique features of a wireless network necessitates a cross-layer approach, involving the physical and the network layers, to solve this problem as opposed to a traditional network planning problem. We use queuing theory along with wireless interference modeling to present a cross-layer solution to this problem.