A location-based mobility tracking scheme for PCS networks

This paper introduces a location-based locating strategy for Personal Communication Services (PCS) systems. In the proposed scheme, location updates are based on the value of a movement counter. The update of the movement counter is based on information on the locations visited by a mobile terminal (MT) since the last location update. In particular, the cell identifiers and the corresponding movement counter values are maintained in the MT for a part of the visited cells since the last location update. When the MT enters a cell whose identifier is not stored in the MT, the movement counter increases by one. If the movement counter reaches the update threshold, a location update is triggered; otherwise, the cell identifier and the corresponding movement counter value are stored in the MT. When the MT enters a cell whose identifier is in the MT, the movement counter is assigned with the counter value kept in the MT for this cell, and all cells with greater counter values in the MT are removed. The proposed scheme allows the dynamic selection of the update threshold according to each user's calling and mobility patterns. Analytical and simulation models have been developed to compare the proposed scheme with both the movement-based scheme and the distance-based scheme. Results demonstrate that when the call-to-mobility ratio (CMR) is low, the proposed scheme can achieve a significant cost reduction compared to the movement-based scheme. For example, when the CMR is 0.01, a savings of around 25% in the optimal total cost per call arrival is achieved with the proposed scheme. Moreover, the proposed scheme is easier to implement than the distance-based scheme.     

Adaptive channel assignment scheme for wireless networks

In this paper, an adaptive channel assignment scheme is proposed to ensure the quality of services for the wireless networks. The proposed scheme divides the channels into two categories, the guard channels and the shared channels. The number of guard channels is estimated by the Markovian model in order to keep the handoff calls higher priority. The remaining channels, called shared channels, can be used by both new calls and handoff calls. The proposed scheme based on incoming rates of handoff and new calls allocates channels for guard and shared channels. In addition, this approach is able to provide quality of service guarantee in terms of handoff dropping rate. From the simulation, the proposed scheme significantly improves the dropping rate and the blocking rate in comparison with the existing methods.     

A preemptive channel allocation scheme for multimedia traffic in mobile wireless networks

This paper presents a channel allocation model with both partial and full preemptive capabilities for multimedia traffic in mobile wireless networks. The different types of multimedia traffic in transmitting through next-generation networks possess different characteristics and demand an adequate channel allocation scheme to fulfill individual Quality of Service (QoS) requirements. In the proposed model, multimedia traffic is classified into three classes corresponding to different priority levels in a decreasing order. To effectively reduce the dropping probability, a higher-priority handoff call is allowed to fully or partially preempt any lower-priority ongoing calls when the channel capacity becomes insufficient. In addition, to prevent from possible starvation of the lowest-priority traffic, a portion of system channels are purposely reserved. Performance measures, including the dropping probability of handoff calls, the call-interruption probability that an ongoing call is forced to termination due to full preemption, and the bandwidth reduction ratio due to partial preemption, are investigated through an analytical model built with 4-D Markov chains. The numerical results demonstrate the effectiveness of our model.     

Performance modeling of the LEACH protocol for mobile wireless sensor networks

In many wireless sensor network applications, nodes are mobile, while many protocols proposed for these networks assume a static network. Thus, it is important to evaluate if a traditional protocol designed for a static network can tolerate different levels of mobility. This paper provides an analytic model to investigate the effect of mobility on a well-known cluster-based protocol, LEACH. The model evaluates data loss after construction of the clusters due to node mobility, which can be used to estimate a proper update interval to balance the energy and data loss ratio. Thus, the results can help the network designer to adjust the topology update interval given a value of acceptable data loss threshold. A practical approach to increase the mobility tolerance of the protocol is applying a buffer zone to the transmission ranges of the nodes. The model is extended in order to consider the effect of buffer zone. To validate the analytic evaluations, extensive simulations are conducted and correctness of the evaluations is tightly verified.     

IEEE802.16中基于自适应信道预留的呼叫接入策略

呼叫接入控制（CAC）在宽带无线接入（BWA）服务质量（QoS）中起着非常重要的作用。对无线城域网中IEEE802.16复杂的QoS定义,该文提出了一种在IEEE802.16中基于自适应资源预留的呼叫接入控制策略（AR-CAC）。该策略根据UGS负载和信道利用率为其自适应预留信道,同时考虑了IEEE802.16业务的带宽特性。仿真结果表明,该策略在硬切换呼叫切换失败概率不变的情况下降低了高优先级服务的呼叫阻塞率,同时增大了系统的吞吐量。     

QoS-aware radio resource management scheme for CDMA cellular networks based on dynamic interference guard margin (IGM)

Efficient radio resource management (RRM) for CDMA-based cellular communication systems using the interference guard margin (IGM) scheme is investigated in this work. Two important concepts, i.e., the guard channel (GC) and the load curve (LC), are integrated to derive IGM. The resulting call admission control (CAC) scheme gives preferential treatment to higher priority handoff calls by pre-reserving a certain amount of resource in terms of IGM. A radio resource estimation (RRE) function is implemented in each base station (BS) to assist RRM module to adjust the level of IGM dynamically. RRE in each BS estimates the amount of IGM by considering traffic load in its current cell as well as traffic conditions in neighboring cells. A service model is adopted to support quality of service (QoS) demand of multiple services, which includes mobile terminal’s data rate, different levels of priorities, mobility and rate adaptivity characteristics. Simulations are conducted by OPNET to study performance of the proposed IGM scheme in terms of a defined cost function, new call blocking probability, handoff dropping probability and system utilization, under different traffic conditions.     

Predictive channel reservation for handoff prioritization in wireless cellular networks

In wireless cellular networks, a roaming mobile station (MS) is expected to move from one cell to another. In order to ensure that ongoing calls are not dropped while the owner mobile stations roam among cells, handoff calls may be admitted with a higher priority than newly generated calls. Predictive channel reservation (or pre-reservation) schemes allow the reservation of a channel for an ongoing call in an adjacent cell before its owner MS moves into that cell, so that the call is sustained when the MS moves into the adjacent cell. Pre-reservations are made when the MS is within some distance of the new cell boundary. This distance determines the area in which the MS can make channel reservations. In this paper, we study the effect of the pre-reservation area size on handoff performance in wireless cellular networks. Our studies show that if the reserved channels are strictly mapped to the MSs that made the corresponding reservations, as we increase the pre-reservation area size, the system performance (in terms of the probability that the handoff calls are dropped) improves initially. However, beyond a certain point, the performance begins to degrade due to a large number of false reservations. The optimal pre-reservation area size is closely related to the traffic load of the network and the MSs’ mobility pattern (moving speed). We provide an analytical formulation that furthers understanding with regard to the perceived behavior in one-dimensional networks (in which all cells are along a line).With the objective of improving handoff performance and alleviating this sensitivity to the area size, we propose an adaptive channel pre-reservation scheme. Unlike prior pre-reservation methods, the key idea in our scheme is to send a channel pre-reservation request for a possible handoff call to a neighboring cell not only based on the position and orientation of the owner MS, but also as per its speed towards the target cell. The newly proposed scheme uses GPS measurements to determine when channel pre-reservation requests are to be made. Simulation results show that the adaptive channel pre-reservation scheme performs better in all typical scenarios than a previously proposed popular pre-reservation method that does not take mobility into account.     

A novel re-authentication scheme based on tickets in wireless local area networks

Fast re-authentication schemes during handover of a mobile station are essential to seamless services for real-time multimedia applications in wireless local area networks. Although much research has been done to reduce re-authentication latency, the schemes developed so far either suffer from heavy burden problems or degrade the security level. In this paper, a novel ticket-based approach is proposed for re-authentication during handover. The mobile station receives handover tickets from the authentication server as a proof of authorization, and it presents the corresponding ticket when associating with a new access point. Our scheme reduces re-authentication delay to the delay of 2-way handshake between a mobile station and an access point. Furthermore, this scheme imposes less burden over the entities compared with other proactive key pre-distribution schemes, while satisfying 802.11i security requirements.     

Provably secure and efficient authentication techniques for the global mobility network

Recently, several authentication techniques have been developed for the global mobility network (GLOMONET), which provides mobile users with global roaming services. Due to the hardware limitations, the mobile user cannot support the heavy encryption and decryption. This investigation adjusts the entity in the roaming scenario that selects the session key to be used to different types of authentication schemes in GLOMONET and presents two provably secure and efficient authentication protocols for roaming services. One protocol is based on synchronized clocks, while the other uses random numbers. Compared to related approaches, the proposed authentication protocols not only reduce the number of transmissions, but also diminish the computational cost involved in encryption and decryption. Thus, they are more suitable for GLOMONET.     

Mobility management for m-commerce requests in wireless cellular networks

Increasing number of sophisticated services provided by the current wireless communication systems have caused a significant transition from E-commerce to M-commerce. Enterprises have provided considerable new opportunities to promote their businesses accessible from small mobile devices such as personal digital assistant (PDA) or mobiles phones. These facilities are envisioned as the most convenient way of using M-commerce. Using such services from mobile phones or PDAs equipped with GSM/GPRS involve effective mobility management mechanisms in cellular networks—a popular architecture for wireless networks. Success of such systems will largely depend on the reliable connection for the roaming users. Consequently, Quality of Service (QoS) provision is one of the most challenging issues in the heterogeneous wireless network-based m-commerce systems. Such m-commerce systems enable users to roam between different wireless networks operators and geographical areas while providing interactive broadband services and seamless connectivity. This paper presents an analytical framework to model scarce channels in any cell for maximizing channel utilization and efficient handling of handover requests. Typical numerical experiments are presented to validate the analytical solution against simulation to study the effect of bursty traffic upon the performance of the cell in any cellular networks.     

Dynamically adaptive networks for integrating optimal pressure management and self-cleaning controls

This paper investigates the problem of integrating optimal pressure management and self-cleaning controls in dynamically adaptive water distribution networks. We review existing single-objective valve placement and control problems for minimizing average zone pressure (AZP) and maximizing self-cleaning capacity (SCC). Since AZP and SCC are conflicting objectives, we formulate a bi-objective design-for-control problem where locations and operational settings of pressure control and automatic flushing valves are jointly optimized. We approximate Pareto fronts using the weighted sum scalarization method, which uses a previously developed convex heuristic to solve the sequence of parametrized single-objective problems. The resulting Pareto fronts suggest that significant improvements in SCC can be achieved for minimal trade-offs in AZP performance. Moreover, we demonstrate that a hierarchical design strategy is capable of yielding good quality solutions to both objectives. This hierarchical design considers pressure control valves first placed for the primary AZP objective, followed by automatic flushing valves placed to augment SCC conditions. In addition, we investigate an adaptive control scheme for dynamically transitioning between AZP and SCC controls. We demonstrate these control challenges on case networks with both interconnected and branched topology.     

On-demand channel reservation scheme for common traffic in wireless mesh networks

Wireless mesh networks (WMNs) have recently gained momentum as a new broadband internet access technology to provide internet traffic. These networks have unique characteristics that make them different from ad hoc networks. These differences are as follows. First, WMNs are composed of static mesh routers that are equipped with multiple radio interfaces and turn each interface into a non-overlapping channel. These additional interfaces can create multiple concurrent links between adjacent nodes. Second, most of the traffic in WMNs is directed towards the gateway. Third, both local traffic and internet traffic are relayed by the mesh router to indeed destination. The Multi-Radio Ad hoc On-Demand Distance Vector (AODV-MR) developed to support multi-radio and does not take into account above-mentioned WMNs characteristics. In this paper, we propose an on-demand channel reservation scheme to reserve some of mesh router radio interfaces to support the gateway traffic while the remaining interfaces can be used to support the local traffic. Our scheme establishes high throughput paths for the traffic destined at the gateway, reduces the intra-flow and inter-flow interferences as well as to support full duplex node transmission.The scheme allows the gateway to assign a list of channels for each received gateway routing discovery message. Simulation results show that our proposed scheme significantly improves the performance of multi-radio multi-channel wireless mesh networks.     

A power- and coverage-aware clustering scheme for wireless sensor networks

A common and critical operation for wireless sensor networks is data gathering. The efficient clustering of a sensor network that can save energy and improve coverage efficiency is an important requirement for many upper layer network functions. This study concentrates on how to form clusters with high uniformity while prolonging the network lifetime. A novel clustering scheme named power- and coverage- aware clustering (PCC) is proposed, which can adaptively select cluster heads according to a hybrid of the nodes' residual energy and loyalty degree. Additionally, the PCC scheme is independent of node distribution or density, and it is free of node hardware limitations, such as self-locating capability and time synchronization. Experiment results show that the scheme performs well in terms of cluster size (and its standard deviation), number of nodes alive over time, total energy consumption, etc.     

Performance analysis of Virtual Mobility Domain scheme vs. IPv6 mobility protocols

The population of mobile users seeking connectivity to the Internet has been growing over the years, spurred by the capabilities of handsets and the increasing rich Internet content and services. Mobility management to enable efficient Internet access for users on the move is thus gaining significance. IETF has standardized several protocols such as Mobile IPv6, Hierarchical Mobile IPv6, and Proxy Mobile IPv6 to provide mobility management on the IP network. With future Internet design initiatives gaining momentum, it is important that these initiatives consider mobility management as an integral part of the design. In this article, we introduce the concept of Virtual Mobility Domain and describe the main features and key strengths of Virtual Mobility Domain that are designed to provide mobility management in a newly proposed tiered Internet architecture. Instead of IP addressing, the proposed Virtual Mobility Domain uses a tiered-addressing scheme to identify a mobile node with a single address regardless of its location. The tiered addressing provides a dynamic address length which brings less signaling overhead and scalable management. We also propose a collaborative network-based mobility management mechanism to provide low-latency handoffs and less processing-overhead on the mobile node compared to the IPv6-based protocols. The proposed mobility scheme unifies inter and intra-domain mobility management by introducing common anchor cloud concept which provides a distributed management and seamless mobility experience. We present comparative qualitative and quantitative performance analysis of Virtual Mobility Domain and aforementioned IPv6-based mobility protocols for Intra-AS roaming support. We examine handoff latency and signaling overhead performance of each protocol based on numerical results retrieved from analytical models and OPNET modeler based simulations. The results from a comparative performance study show the potential for more efficient mobility management under the proposed Internet architecture.     

An analytical study of central and in-network data processing for wireless sensor networks

This paper compares the performance of centralized and in-network data processing for wireless sensor networks (WSNs) under various deployment conditions on the real sensor hardware Sun SPOT from Sun Microsystems. We define several criteria to measure the quality of responses in WSN applications. Guided by an extensive experimental study, we discuss in detail the performance impacts of different deployment factors on algorithms that implement both centralized and in-network computing. Finally, performance guidelines are given to algorithm designers for WSN applications.     

Distributed clustering algorithms for data-gathering in wireless mobile sensor networks

One critical issue in wireless sensor networks is how to gather sensed information in an energy-efficient way since the energy is a scarce resource in a sensor node. Cluster-based architecture is an effective architecture for data-gathering in wireless sensor networks. However, in a mobile environment, the dynamic topology poses the challenge to design an energy-efficient data-gathering protocol. In this paper, we consider the cluster-based architecture and provide distributed clustering algorithms for mobile sensor nodes which minimize the energy dissipation for data-gathering in a wireless mobile sensor network. There are two steps in the clustering algorithm: cluster-head election step and cluster formation step. We first propose two distributed algorithms for cluster-head election. Then, by considering the impact of node mobility, we provide a mechanism to have a sensor node select a proper cluster-head to join for cluster formation. Our clustering algorithms will achieve the following three objectives: (1) there is at least one cluster-head elected, (2) the number of cluster-heads generated is uniform, and (3) all the generated clusters have the same cluster size. Last, we validate our algorithms through an extensive experimental analysis with Random Walk Mobility (RWM) model, Random Direction Mobility (RDM) model, and a Simple Mobility (SM) model as well as present our findings.     

能量自适应的无线传感器网络分簇路由协议

为有效解决无线传感器网络中的"热区"问题,提出了一种能量自适应的非均匀分簇路由协议.协议采取非均匀的分簇结构,使靠近基站的簇范围减小到合理的范围,即在靠近基站的区域内,每个簇由较少的无线传感器节点构成,这些节点的主要工作是负责转发其它簇的信息,从而有效减少其能量消耗速率.同时,协议在通信路由的过程中还综合考虑了簇头与中转节点的距离以及中转节点的能量消耗率.实验结果表明,该协议有效解决了"热区"问题,并且延长了无线传感器网络的生命周期.     

Protocols for mobility management in heterogeneous multi-hop wireless networks

Substantial works have recently been reported on the mobility management in single-hop wireless networks (e.g. cellular networks and WLAN hotspots), while there has been an increased interest in multi-hop communications. This has made mobility management in heterogeneous multi-hop wireless networks (HMWNs) really interesting so that both single-hop and multi-hop communication paradigms can be integrated. One of the main research challenges for 4G wireless systems is the identification of a mobility management technique that could integrate different wireless technologies such as WLANs, WMANs and WWANs, operating in infrastructure (single-hop) and infrastructureless (ad hoc or multi-hop) modes. In this article we envision a futuristic HMWN where heterogeneous networks, operating in single-hop and multi-hop modes are integrated to provide increased capacity and enhanced coverage for the users. We summarize various existing mobility management solutions and discuss why these schemes are not adequate for HMWNs, as well as highlighting our view of mobility management issues in HMWNs.