Performance enhancement of mSCTP for vertical handover across heterogeneous wireless networks

In the mobile Stream Control Transmission Protocol (mSCTP) for vertical handover, a mobile user may suffer from performance degradation due to the problems of packet reordering and retransmission timeout and due to the packet loss during handover. To solve these problems, we propose a new scheme of handover retransmission for mSCTP handover, in which the correspondent node retransmits the outstanding data packets to the mobile node over the new primary path. From simulation results, it is shown that the proposed scheme can avoid the packet reordering and retransmission timeout problems during handover. Moreover, we can see that the proposed scheme can significantly improve throughput of mSCTP handover, compared with the existing schemes. Copyright © 2009 John Wiley & Sons, Ltd.     

Improving TCP performance for vertical handover in heterogeneous wireless networks

The incorporation of wireless local area networks (WLANs) into existing cellular networks as supplementary access technologies has become an issue of great interest. However, vertical handover (VHO), which allows users to roam between a WLAN and a cellular network, causes an abrupt change in certain link characteristics such as the round trip time and data rate. Owing to such changes, reordering problem and premature timeout occur and trigger unnecessarily fast retransmission during VHO, causing throughput degradation. Thus, we propose a new transmission control protocol (TCP) mechanism, which resolves the reordering problem by suppressing unnecessary retransmission caused by spurious duplicate acknowledgments (dupacks) incurred because of the reordering problem, and prevents premature timeout by employing an adaptive retransmission timer. We analytically investigate the throughput of our proposed TCP scheme. The numerical and simulation results show that our proposed TCP performs better in terms of throughput than other schemes appearing in the literature. Copyright © 2009 John Wiley & Sons, Ltd.     

A fast handover protocol for 6LoWPAN wireless mobile sensor networks

Node localization is one of the most critical issues for wireless sensor networks, as many applications depend on the precise location of the sensor nodes. To attain precise location of nodes, an improved distance vector hop (IDV-Hop) algorithm using teaching learning based optimization (TLBO) has been proposed in this paper. In the proposed algorithm, hop sizes of the anchor nodes are modified by adding correction factor. The concept of collinearity is introduced to reduce location errors caused by anchor nodes which are collinear. For better positioning coverage, up-gradation of target nodes to assistant anchor nodes has been used in such a way that those target nodes are upgraded to assistant anchor nodes which have been localized in the first round of localization. For further improvement in localization accuracy, location of target nodes has been formulated as optimization problem and an efficient parameter free optimization technique viz. TLBO has been used. Simulation results show that the proposed algorithm is overall 47, 30 and 22% more accurate than DV-Hop, DV-Hop based on genetic algorithm (GADV-Hop) and IDV-Hop using particle swarm optimization algorithms respectively and achieves high positioning coverage with fast convergence.     

A QoE handover architecture for converged heterogeneous wireless networks

The convergence of real-time multimedia applications, the increasing coverage of heterogeneous wireless networks and the ever-growing popularity of mobile devices are leading to an era of mobile human-centric multimedia services. In this scenario, heterogeneous communications will co-exist and ensure that the end-user is always best connected. The rigorous networking demands of wireless multimedia systems, beyond quality-oriented control strategies, are necessary to guarantee the best user experience over time. Therefore, the Quality of Experience (QoE) support, especially for 2D or 3D videos in multi-operator environments, remains a significant challenge and is crucial for the success of multimedia systems. This paper proposes a QoE Handover Architecture for Converged Heterogeneous Wireless Networks, called QoEHand. QoEHand extends the Media Independent Handover (MIH)/IEEE 802.21 with QoE-awareness, seamless mobility and video adaptation by integrating a set of QoE-based decision-making modules into MIH, namely a video quality estimator, a dynamic class of service mapping and content adaptation schemes. The QoEHand video estimator, mapping and adaptation components operate by coordinating information about video characteristics, available wireless resources in IEEE 802.11e and IEEE 802.16e service classes, and QoE-aware human experience. The video quality estimator works without the need for any decoding, which saves time and minimises processing overheads. Simulations were carried out to show the benefits of QoEHand and its impact on user perception by using objective and subjective QoE metrics.     

A distributed location management strategy for next- generation IP-based wireless networks

1 Introduction Mobility management is a key technical aspect in mobile communication systems. The main purpose of mobility management is to enable mobile terminals or users to communicate with each other continuously while moving—— while minimizing data…     

Mobile flow-aware networks for mobility and QoS support in the IP-based wireless networks

As the volume of mobile traffic consisting of video, voice, and data is rapidly expanding, a challenge remains with the mobile transport network, which must deliver data traffic to mobile devices without degrading the service quality. Since every Internet service holds its own service quality requirements, the flow-aware traffic management in fine granularity has been widely investigated to guarantee Quality of Service (QoS) in the IP networks. However, the mobile flow-aware management has not been sufficiently developed yet because of the inherent constraints of flow routing in the mobile networks regarding flow-aware mobility and QoS support. In this paper, we propose a flow-aware mobility and QoS support scheme called mobile flow-aware network (MFAN) for IP-based wireless mobile networks. The proposed scheme consists of dynamic handoff mechanisms based on QoS requirements per flow to reduce the processing overhead of the flow router while ensuring QoS guarantee to mobile flows. The performance analyses of the proposed scheme demonstrate that MFAN successfully supports the mobile flow traffic delivery while satisfying the QoS requirement of flows in the wireless mobile IP networks.     

Seamless proactive handover across heterogeneous access networks

Dual-mode handsets and multimode terminals are generating demand for solutions that enable convergence and seamless handover across heterogeneous access networks. The IEEE 802.21 working group is creating a framework that defines a Media Independent Handover Function (MIHF), facilitates handover across heterogeneous access networks, and helps mobile users experience better performance during mobility events. In this paper, we describe this 802.21 framework and also summarize a Media-independent Pre-Authentication (MPA) mechanism currently under discussion within the IRTF that can further optimize handover performance. We discuss how the 802.21 framework and the MPA technique can be integrated to improve handover performance. Finally, we describe a test-bed implementation and validate experimental performance results of the combined mobility technique.     

A hybrid handover protocol for local area wireless ATM networks

While handovers of voice calls in a wide area mobile environment are well understood, handovers of multi-media traffic in a local area mobile environment is still in its early stage of investigation. Unlike the public wireless networks, handovers for multi-media Wireless LANs (WLANs) have special requirements. In this paper, the problems and challenges faced in a multi-media WLAN environment are outlined and a multi-tier wireless cell clustering architecture is introduced. Design issues for multi-media handovers are specified and a fast, continuous and efficient hybrid handover protocol is proposed. The protocol is scalable and supports source and destination mobile handovers in a mutually exclusive manner. Crossover switch (CX) discovery is also introduced to support fast inter-cluster handovers with consideration given to Mobile Quality of Service (M-QoS). The resulting wireless ATM LAN exhibits a distributed mobile location management, call admission control and handover management architecture. A prototype of the proposed handover protocol is implemented into a Cambridge Fairisle ATM switch and the results of handovers for a single Mobile Host (MH) with a single on-going connection are evaluated. It was found that implementing transport mobility for a wireless ATM environment is not practical as the cell re-routing function changes the traffic characteristics and is not scalable to increasing cell rate and to the number of mobile connections. The data-link layer mobility implementation however, is found to work well. The protocol provides symmetric data disruption to traffic flows in both directions and up to seventy-five intra-cluster handovers can be supported in a second. Throughout the experiment, cells arrive in sequence with no cell loss observed during the handover, up to the capacity limit of the ATM switch. Finally, zig-zag handovers and handovers for a single MH with multiple on-going unicast connections are performed in order to evaluate the robustness and performance of the protocol under different MHs' migration and communication environment.Parts of this paper appeared in the ACM First International Conference on Mobile Computing and Networking (MOBICOM'95), Berkeley, California, November 1995 as The Design & Implementation of A Hybrid Handover Protocol For Multi-Media Wireless LANs.C-K Toh is supported by a King's College Cambridge External Research Studentship and a Cambridge Commonwealth Trust Scholarship.     

Context-aware parallel handover optimization in heterogeneous wireless networks

Annals of Telecommunications - The key idea of this paper is to a use cross-layer triggering concept in order to control the vertical handover (VHO) in heterogeneous networks. Current mobility...     

A quality-of-service signaling architecture for seamless handover support in next generation,IP-based mobile networks

The coupling of signaling protocols for mobility management and resource reservation plays an important role to achieve Quality-of-Service (QoS) in wireless environments. When performing a handover, request and allocation of resources have to be done in the shortest possible time to avoid disruptions for the user service. Therefore, it is preferable to ensure resource availability in advance, which we call anticipated handover. This approach for providing seamless handovers in turn poses challenges for the overall design of the QoS architecture and its associated QoS signaling protocol. This article describes the design, implementation, and evaluation of a comprehensive QoS architecture and a suitable QoS signaling protocol. It discusses intrinsic problems of reservations in IP based networks such as session ownership as well as a number of protocol design issues regarding the integration of QoS signaling with other protocols, such as Mobile IP. In particular, we define an end-to-end QoS architecture and a mobility-aware reservation signaling protocol Mobility Aware Reservation Signaling Protocol (MARSP) that supports anticipated handover, thus enabling seamless services over heterogeneous wireless access networks. The presented architecture and protocol were implemented and evaluated by measurements. They show that anticipated handovers not only outperform hard handovers regarding handover latency, but that they also provide functional and robustness advantages. Authors Hillebrand and Prehofer changed their affiliation in the meantime, the work described in this paper was carried out during their employment at DoCoMo Communications Laboratories Europe.     

Mechanisms and hierarchical topology for fast handover in wireless IP networks

We propose a mechanism to perform fast handover in IP-based wireless networks for real-time applications such as Internet telephony and videoconferencing. Our proposal is designed to reestablish the communication session traffic flow quickly and to minimize the service disruption delay that occurs during mobile IP handover. In this scheme, we propose two different mechanisms to handle micromobility and inter-subdomain mobility, respectively. Micromobility handover handles movements within the same subdomain. Inter-subdomain handover supports handovers between two adjacent subdomains. The reason for having several subdomains is to deploy the network over a wider area to keep the mobile user in the same network for as long as possible. The novelty of the scheme is to retransmit the buffered packets during micromobility handover and to use multicasting to reestablish traffic flow during inter-subdomain movement. The entire scheme is performed within a hierarchical topology based on next-generation IP networks. We analyze both micromobility and inter-subdomain mobility handovers, and display simulation results for both voice and video over IP for micromobility handover.     

Dynamic segmentation of cellular networks for improved handover performance

One of the most important initial steps, inherent in the planning procedure of cellular networks, is their segmentation in operational parts that is performed at different levels corresponding to the hierarchy and topology of the network. The major goal of this procedure is the efficient deployment of the system and management of the distributed segmented parts while minimizing the signaling overhead in the network. As we show here, it can take place even during the operational phase of the network when certain shortcomings appear. In this work, we present an approach based on graph theory for the segmentation of cellular networks at the Base Station Controller (BSC) level that achieves a significant increase in the performance of the network. In particular, with the proposed method, both the handover attempts when a mobile station is moving to a cell belonging to a different BSC as well as the corresponding handover failure rate are decreased significantly, allowing for a continuous network upgrade. Copyright © 2007 John Wiley & Sons, Ltd.     

An intelligent agent-based scheme for vertical handover management across heterogeneous networks

Advances in technology have enabled a proliferation of mobile devices and a broad spectrum of novel and outbreaking solutions for new applications and services. The increasing demand for all time and everywhere services requires the network operators to integrate different kinds of wireless and cellular networks. To enable this integration, it is important that users can roam freely across networks. As different technologies are involved in the current infrastructure, the problem of vertical handover needs to be addressed. To cope with the problem of seamless connectivity, several solutions have been presented. But most of them either lack intelligence or are not adaptable for reducing the packet loss and delay involved in the handover procedure. An intelligent technique is needed in order to perform the service continuity in the heterogeneous environment. This paper presents a cooperative agent based approach for the vertical handover using a knowledge plane. We propose to introduce the agents in the mobile nodes and access points to collect the necessary information from the environment. Based on this information, agents take a handover decision. A selection function is also introduced in this work which helps in choosing a best network from the available ones for handover. Finally, the proposed approach is validated with the help of simulations.     

Analysis of secure handover for IEEE 802.1x-based wireless ad hoc networks

The handover procedure in secure communication wireless networks is an extremely time-consuming phase, and it represents a critical issue in relation to the time constraints required by certain real-time traffic applications. In particular, in the case of the IEEE 802.1X model, most of the time required for a handover is used for packet exchanges that are required for authentication protocols, such as Extensible Authentication Protocol Transport Layer Security (EAP-TLS), that require an eight-way handshake. Designing secure re-authentication protocols to reduce the number of packets required during a handover is an open issue that is gaining interest with the advent of a pervasive model of networking that requires realtime traffic and mobility. This article presents the 802.1X model and evaluates its application to ad hoc networks based on IEEE 802.11 i or IEEE 802.1 be standards, focusing on the problems that must be evaluated when designing handover procedures, and suggesting guidelines for securing handover procedures. It also presents a novel protocol to perform secure handovers that is respectful of the previous analysis and that has been implemented in a mesh environment.     

Lossless handover for wireless ATM

Handover is one of the key research topics for the emerging wireless ATM networks. This paper describes a handover mechanism for intra-switch handovers for wireless ATM. The handover procedure is simple enough to be implementable as a limited enhancement to ATM switch platforms for fixed network, yet provides low delay and lossless handover when used together with a suitable radio interface. The paper also reports on initial simulation result.     

A smart handover prediction system based on curve fitting model for Fast Mobile IPv6 in wireless networks

Seamless handover process is essential in order to provide efficient communication between mobile nodes in wireless local area networks. Despite the importance of a signal strength prediction model to provide seamless handovers, it is not embedded in standard mobility management protocols. In this article, we propose a smart handover prediction system based on curve fitting model to perform the handover (CHP) algorithm. The received signal strength indicator parameter, from scanning phase, is considered as an input to the CHP in order to provide a prediction technique for a mobile node to estimate the received signal strength value for the access points in the neighborhood and to select the best candidate access point from them in an intelligent way. We implemented the proposed approach and compared it with standard protocols and linear regression‐based handover prediction approach. Simulation results in complex wireless environments show that our CHP approach performs the best by predicting the received signal strength value with up to 800 ms in advance from real obtained value via scanning phase. Moreover, our CHP approach is the best in terms of layer 2 and overall handover latency, in comparison with standard protocols and linear regression approach, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Integrated management architecture for IP-based networks

IP telephony will bring about a dramatic change in the way IP services are planned, provisioned, managed, and billed. In order to build and retain a strong customer base for these new services, service providers need to meet, if not exceed, the customer expectations set by today's traditional voice services. Acceptance of IP telephony will depend on the quality and efficiency with which service providers offer, deliver, and manage IP services. Installation, configuration, and activation must be rapid and error-free. Furthermore, customers will want direct control over the reconfiguration of services and real-time visibility into the impact change has on their operating costs. Once the service is activated, customers will want the provider to guarantee service quality as defined by industry standards. Corporate customers in particular will need to be assured that the provider is proactively monitoring performance to avoid problems and providing them visibility into the performance data collected. This article discusses an integrated management support system for IP-based networks illustrating the functions needed to support the unique challenges of managing VoIP services. An example of a service management system is also described     

Analysis of UAV wireless network coverage and handover performance

For the characteristics of unmanned aerial vehicle (UAV),such as high mobility,adjustable height,and high probability of line-of-sight channels,which introduced multiple challenges to the design and deployment of current and future wireless network,and the networking performance of UAV was the focus and difficult issues in the industry,the network coverage and handoff performance of heterogeneous UAV wireless network was analyzed,which provided insights into UAV wireless networking.Specifically,considering the outdated channel state information introduced by the UAV’s mobility,analytical expressions of handover probability,handover error probability,and coverage probability for heterogeneous UAV wireless network were derived by utilizing the tools from stochastic geometry.In addition,the impacts of the UAV’s mobility,height,as well as the density of terrestrial base stations on the aforementioned performance metrics were investigated.It shows that the outdated channel state information caused handover error,which increases first and then decreases with the increase of UAV’s moving speed and density of base stations.Meanwhile,the impact of UAV’s flight height on coverage probability is more significant than that of moving speed.