Using cross-layer metrics to improve the performance of end-to-end handover mechanisms

Network centric handover solutions for all IP wireless networks usually require modifications to network infrastructure which can stifle any potential rollout. This has led researchers to begin looking at alternative approaches. Endpoint centric handover solutions do not require network infrastructure modification, thereby alleviating a large barrier to deployment. Current endpoint centric solutions capable of meeting the delay requirements of Voice over Internet Protocol (VoIP) fail to consider the Quality of Service (QoS) that will be achieved after handoff. The main contribution of this paper is to demonstrate that QoS aware handover mechanisms which do not require network support are possible. This work proposes a Stream Control Transmission Protocol (SCTP) based handover solution for VoIP called Endpoint Centric Handover (ECHO). ECHO incorporates cross-layer metrics and the ITU-T E-Model for voice quality assessment to accurately estimate the QoS of candidate handover networks, thus facilitating a more intelligent handoff decision. An experimental testbed was developed to analyse the performance of the ECHO scheme. Results are presented showing both the accuracy of ECHO at estimating the QoS and that the addition of the QoS capabilities significantly improves the handover decisions that are made.     

Interoperability in Internet of Things: Taxonomies and Open Challenges

Mobile Networks and Applications - In the last few years, many smart objects found in the physical world are interconnected and communicate through the existing internet infrastructure which...     

Performance Analysis of Prefix Delegation-Based Route Optimization Schemes: Effects of Increasing the Number of Nodes

Prefix delegation-based schemes have been proposed to solve the route optimization problem in NEtwork MObility where multiple IP-enabled hosts move together as a mobile network. Differences in the route optimization for hosts at the cost of increased signaling will result in performance difference of the schemes depending on parameters, such as speed of the mobile network, its distance from the home network (the network to which mobile network usually belongs), and the number of hosts in the mobile network. Although the effects of the first two parameters on the performance of the schemes have been studied, effects of increasing the number of hosts have not been studied. Therefore, there is a need to evaluate performance when the number of hosts is increased. We perform the evaluation through ns-2 simulation. Results show that the performance superiority achieved by the hosts?? route optimization is only affected by the distance significantly only when the number of hosts is small. The results will help to decide when to use the route optimization for hosts depending on the values of the parameters.     

Survivability evaluation of SIGMA and mobile IP

Mobile IP has been developed by IETF to handle mobility of Internet hosts at the network layer. Mobile IP suffers from a number of drawbacks, including low survivability due to single-point failure of Home Agents. Recently, Seamless IP diversity based Generalized Mobility Architecture (SIGMA) was proposed to support low latency, low packet loss mobility of IP hosts. In this paper, we show that the location management scheme used in SIGMA enhances the survivability of the SIGMA-based mobile network. We develop an analytical model to evaluate and compare the survivability of SIGMA with that of Mobile IP. Numerical results show the improvement in system response time and service blocking probability of SIGMA over Mobile IP in the presence of hardware failures and Distributed Denial of Service (DDoS) attacks. The research reported in this paper was funded by NASA Grants NAG3-2922 and NNX06AE44G     

Exact algorithm for delay-constrained capacitated minimum spanning tree network

The delay-constrained capacitated minimum spanning tree (DC-CMST) problem of finding several broadcast trees from a source node is discussed. While the traditional CMST problem deals with only the traffic capacity constraint served by a port of the source node, and delay-constrained minimum spanning tree (DCMST) considers only the maximum end-end delay constraint, the DC-CMST problem deals with both the mean network delay and traffic capacity constraints. The DC-CMST problem consists of finding a set of minimum cost spanning trees to link end-nodes to a source node satisfying the traffic requirements at end-nodes and the required mean delay of the network. In the DC-CMST problem, the objective function is to minimise the total link cost. A dynamic programming-based three-phase algorithm that solves the DC-CMST problem is proposed. In the first phase, the algorithm generates feasible solutions to satisfy the traffic capacity constraint. It finds the CMSTs in the second phase, and allocates the optimal link capacities to satisfy the mean delay constraint in the third phase. Performance evaluation shows that the proposed algorithm has good efficiency for any network with less than 30 nodes and light traffic. The proposed algorithm can be applied to any network regardless of its configuration, and used for the topological design of local networks and for efficient routing algorithms capable of constructing least cost broadcast trees.     

Cross-layer speculative architecture for end systems and gateways in computer networks with lossy links

The throughput degradation of Transport Control Protocol (TCP)/Internet Protocol (IP) networks over lossy links due to the coexistence of congestion losses and link corruption losses is very similar to the degradation of processor performance (i.e., cycle per instruction) due to control hazards in computer design. First, two types of loss events in networks with lossy links are analogous to two possibilities of a branching result in computers (taken vs. not taken). Secondly, both problems result in performance degradations in their applications, i.e., penalties (in clock cycles) in a processor, and throughput degradation (in bits per second) in a TCP/IP network. This has motivated us to apply speculative techniques (i.e., speculating on the outcome of branch predictions), used to overcome control dependencies in a processor, for throughput improvements when lossy links are involved in TCP/IP connections. The objective of this paper is to propose a cross-layer network architecture to improve the network throughput over lossy links. The system consists of protocol-level speculation based algorithms at transport layer, and protocol enhancements at middleware and network layers that provide control and performance parameters to transport layer functions. Simulation results show that, compared with prior research, our proposed system is effective in improving network throughput over lossy links, capable of handling incorrect speculations, fair for other competing flows, backward compatible with legacy networks, and relatively easy to implement.     

Recent Advances in Communication and Internet Technology

Telecommunication Systems -     

SCTP: state of the art in research, products, and technical challenges

The stream control transmission protocol (STCP) is being standardized by the IEFT as a reliable transport protocol to transport SS7signaling messages over IP networks. Due to its attractive features such as multistreaming and multihoming, SCTP has received much attention from the network community, in terms of both research and development. This article introduces the main features of SCTP, and discusses the state of the art in SCTP research and development activities. We also provide a survey of the available products that use SCTP. Finally with a view to stimulating further research in this area, the challenges faced by the SCTP research community are identified.     

Computation availability of crossbar systems in a non-uniform traffic environment

Multiprocessor systems can provide higher performance, reliability, and availability than single processor systems. In order to properly assess the effectiveness of multiprocessor systems, measures that combine performance and reliability are needed. Most previous studies have considered the performance and reliability/availability separately. Only a limited number of studies have been carried out by considering the performance and reliability together in the presence of a uniform traffic in the network. Hot spots in a multiprocessor system result in a non uniform traffic in the network and results in a degradation in the performance of the network. The aim of this paper is to study the combined performance and reliability of a crossbar system in the presence of a hot spot in the system. Computation availability is taken as the criteria for measuring the combined performance and reliability. Markov chain models have been developed to compute the above measurement criteria.     

Comparison of physical and chemical properties of medium-grain rice cultivars grown in California and Arkansas

ABSTRACT:  The physical attributes, chemical composition, and physicochemical properties of 2 medium-grain rice cultivars from Arkansas (Bengal, Medark) and from California (M202, M204) were compared when grown in their respective locations and grown together in Arkansas to better understand the impacts of heredity and environment on medium-grain rice quality. Variations existed in grain dimensions, particularly length distribution, among cultivars and between crop years. When grown separately, the Arkansas cultivars tended to have higher protein and lipid contents but lower amylose contents than the California cultivars. M204 contained a significantly higher apparent amylose content (21.0%) compared with the other 3 cultivars (14.3% to 16.4%). The Arkansas rice cultivars exhibited higher pasting and gelatinization temperatures and produced harder gels and less sticky cooked rice. However, when the 4 cultivars were grown together in Arkansas, differences in protein and amylose contents, gelatinization and pasting properties, and cooked rice texture decreased. This study demonstrated that genetics, location, and crop year all contributed to variations in rice chemical and physical characteristics.