Handoff Scheme Research Articles

Completed analysis of cellular networks with PH-renewal arrival call

In this paper, we apply the PH-renewal process to model new call and handoff processes, and apply the matrix-analytic approach to explore the performance measures of the drop and block probabilities. We examine the bursty nature of handoff call drops by means of conditional statistics with respect to alternating block and non-block periods. Five related performance measures are derived from conditional statistics, including the long-term new call block and handoff call drop probabilities, and the three short-term measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. These performance measures greatly assist the priority reservation handoff mechanism in determining a proper threshold guard channel in the cell. Furthermore, we derive the handoff call drop probability from the short-term performance measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. The results presented in this paper can provide guidelines for designing adaptive algorithms to adjust the threshold in the guard channel reservation handoff scheme.

Stochastic Petri Nets Modeling Methods of Channel Allocation in Wireless Networks

To obtain realistic performance measures for wireless networks, one should consider changes in performance due to failure related behavior. In performability analysis, simultaneous consideration is given to both pure performance and performance with failure measures. SRN is an extension of stochastic Petri nets and provides compact modeling facilities for system analysis. In this paper, a new methodology to model and analyze performability based on stochastic reward nets (SRN) is presented. Composite performance and availability SRN models for wireless handoff schemes are developed and then these models are decomposed hierarchically. The SRN models can yield measures of interest such as blocking and dropping probabilities. These measures are expressed in terms of the expected values of reward rate functions for SRNs. Numerical results show the accuracy of the hierarchical model. The key contribution of this paper constitutes the Petri nets modeling techniques instead of complicate numerical analysis of Markov chains and easy way of performance analysis for channel allocation under SRN reward concepts.

A Proactive mobile‐initiated fast handoff scheme using the multihomed approach

AbstractMobile IP (MIP) defines a mobility management for mobile users to continuously access data when the currently attachment is changed to another network. However, when mobile node (MN) roams between network segments, the handoff latency results in packet losses and transmission delay. In this paper, we propose a multihomed fast handoff scheme (MFH‐MIP) to decrease the handoff cost. In the proposed MFH‐MIP scheme, each MN is implemeted with the link layer trigger and multihomed techniques. Based on the link layer trigger, MN can collect signal strengths of nearby access points (APs) and switch to a new link automatically when the old link becomes unsuitable to connect. Using the multihomed technique, MN can prepare for handoff using two (or more) interfaces, in which (i) one is connected with the old link to receive packets and (ii) the other one is used to access nearby APs and select the most suitable one as the new link, in parellel. In this way, MN can continuously transmit and receive packets during handoff. Based on the proposed method, MN can roam smoothly among different networks in the wireless environment. Copyright © 2008 John Wiley & Sons, Ltd.

Performance analysis of a dynamic handoff scheme in wireless networks with heterogeneous call arrival processes

The Guard Channel Scheme (GCS) and Handoff Queueing Scheme (HQS) are the popular and practical strategies to prioritize handoff calls in wireless cellular networks. A key issue of giving handoff calls the higher priority is how to achieve a tradeoff among the handoff call blocking probability, new call blocking probability and handoff delay. This paper extends GCS and HQS and presents an efficient handoff scheme that dynamically manages the channels reserved for handoff calls depending on the current status of the handoff queue. A three-dimensional Markov model is developed to analyze the performance of this scheme and investigate the desirable performance tradeoff. The Poisson process and Markov-Modulated-Poisson-Process (MMPP) are used to model the arrival processes of new and handoff calls, respectively. The accuracy of this model is evaluated through the extensive comparison of the analytical results to those obtained from discrete-event simulation experiments. Performance measures in terms of the mean number of calls in the system, aggregate response time, aggregate call blocking probability, handoff call blocking probability, new call blocking probability and handoff delay are evaluated. The analytical model is used to investigate the effects of the number of channels originally reserved for handoff calls, the number of dynamic channels, and the ratio of the rate of handover calls to the aggregate arrival rate on the system performance.

A Seamless Handoff Scheme with Access Point Load Balance for Real-Time Services Support in 802.11 Wireless LANs

IEEE 802.11 wirelesses LANs (WLANs) have been rapidly deployed in enterprises, public areas, and households. Voice-over-IP (VoIP) and similar applications are now commonly used in mobile devices over wireless networks. Recent works have improved the quality of service (QoS) offering higher data rates to support various kinds of real-time applications. However, besides the need for higher data rates, seamless handoff and load balancing among APs are key issues that must be addressed in order to continue supporting real-time services across wireless LANs and providing fair services to all users. In this paper, we introduce a novel access point (AP) with two transceivers that improves network efficiency by supporting seamless handoff and traffic load balancing in a wireless network. In our proposed scheme, the novel AP uses the second transceiver to scan and find neighboring STAs in the transmission range and then sends the results to neighboring APs, which compare and analyze whether or not the STA should perform a handoff. The initial results from our simulations show that the novel AP module is more effective than the conventional scheme and a related work in terms of providing a handoff process with low latency and sharing traffic load with neighbor APs.

DeuceScan: Deuce-Based Fast Handoff Scheme in IEEE 802.11 Wireless Networks

The IEEE 802.11 standard has enabled low-cost and effective wireless local area network (WLAN) services. It is widely believed that WLANs will become a major portion of the fourth-generation cellular system. The seamless handoff problem in WLANs is a very important design issue to support the new astounding and amazing applications in WLANs, particularly for a user in a mobile vehicle. The entire delay time of a handoff is divided into probe, authentication, and reassociation delay times. Because the probe delay occupies most of the handoff delay time, efforts have mainly focused on reducing the probe delay to develop faster handoff schemes. This paper presents a new fast handoff scheme (i.e., the DeuceScan scheme) to further reduce the probe delay for IEEE-802.11-based WLANs. The proposed scheme can be useful to improve wireless communication qualities on vehicles. A spatiotemporal approach is developed in this paper to utilize a spatiotemporal graph to provide spatiotemporal information for making accurate handoff decisions by correctly searching for the next access point. The DeuceScan scheme is a prescan approach that efficiently reduces the layer-2 handoff latency. Two factors of stable signal strength and variable signal strength are used in our developed DeuceScan scheme. Finally, simulation results illustrate the performance achievements of the DeuceScan scheme in reducing handoff delay time and packet loss rate and improving link quality.

Adaptive handoff scheme for heterogeneous IP wireless networks

Recent technological advances allow mobile devices to be equipped with multiple wireless interfaces. Moreover, the coexistence of diverse but complementary architectures and wireless access technologies is one of the major trends in 4G or next-generation wireless networks (4G/NGWN). In this context, the selection of an appropriate interface to ensure that a mobile node (MN) remains connected to the network is a challenging issue for seamless roaming. Furthermore, mobility management as well as the integration and interworking of existing wireless systems are a complex task due to their specific characteristics. This paper proposes an efficient handoff protocol, called Handoff Protocol for Integrated Networks (HPIN), which alleviates services disruption during handoff in 4G/NGWN. HPIN is based on a novel handoff decision function and carries out localized mobility, fast handoff and access networks discovery. Performance evaluation based on numerical results shows that the proposed protocol performs better than existing schemes.

Enhanced fast handoff scheme for heterogeneous wireless networks

Mobility management, integration and interworking of existing wireless systems are important factors to obtain seamless roaming and services continuity in next generation or 4G wireless networks (NGWN/4G). Although, several IPv6-based mobility protocols as well as interworking architectures have been proposed in the literature, they cannot guarantee seamless roaming, especially for real-time applications. Moreover, mobility management protocols are designed for specific needs, for example, the purpose of IPv6-based mobility schemes consists of managing users roaming while ignoring access network discovery. This paper proposes an efficient handoff protocol, called enhanced Handoff Protocol for Integrated Networks (eHPIN), which carries out localized mobility management, fast handoff, and access network discovery. It alleviates services disruption during roaming in heterogeneous IP-based wireless environments. Performance evaluation results show that eHPIN provides significant gain with respect to signaling traffic overhead cost, handoff latency, packet delivery cost, handoff failure and packet loss compared with existing IPv6-based mobility schemes.

An effective vertical handoff scheme based on service management for ubiquitous computing

When a ubiquitous computing environment is based on seamless connectivity, intelligent network management among heterogeneous network interfaces, called vertical handoff (VHO), is required. However, conventional VHO schemes are based only on network information, and do not address service management for seamless service execution. This paper thus proposes a middleware architecture supporting efficient seamless connectivity with service management. In this architecture, we define core modules to perform VHOs in accordance with the context of services and user intention, in addition to network information. We also define profiles that express the contexts associated with the VHO process and service management. With the proposed scheme, we show that the number of unnecessary VHOs and application failures is significantly reduced, leading to an enhancement of around 34% in data throughput. The approach also reduces application failures by 50% and the number of VHOs by 32%.

Reliable Integrated Architecture for Heterogeneous Mobile and Wireless Networks

The major trend in next-generation or 4G wireless networks (NGWN/4G) is the coexistence of diverse but complementary architectures and wireless access technologies. In this context, an appropriate integration and interworking of existing wireless networks are crucial to allow seamless roaming across those networks. Several integrated architectures have been proposed for 3G cellular networks and wireless local area networks (WLANs) by both third generation wireless initiatives, 3GPP and 3GPP2. However, the proposed architectures have several drawbacks, the most significant being the absence of quality of service (QoS) guarantees, seamless roaming and service continuity. This paper proposes a novel architecture, called Integrated InterSystem Architecture (IISA), which enables the integration and interworking of various wireless networks and hide their heterogeneities from one another. The IISA architecture aims provisioning of guaranteed seamless roaming and service continuity across different access networks. Performance evaluation shows that IISA together with the proposed handoff management scheme provide significant gains than existing interworking architectures and mobility management protocols.

Seamless Handover in WLAN and Cellular Networks through Intelligent Agents

With the increasing demand of the mobility of mobile users, seamless handover is a critical issue for heterogeneous network accesses. Improving the blocking probability of SIP calls resulting from the handoff delay is a key issue for achieving seamless handovers across WLAN and cellular networks. This paper presents an efficient scheme, based on intelligent agents, to support pre-authentication for seamless handover, where the intelligent agents are able to cooperate with each other adaptively. Besides, intelligent agents offer the applicability of key distribution with EAP-SIM based AAA protocols to enable fast authentication for inter-domain handovers. The paper proposes a number of possible changes to these solutions for inter-domain operation. In addition, simulation results show that the proposed intelligent-agent-based handoff scheme is capable of improving the performance of the existing handover in call blocking ratio, packet loss ratio and call interruption ratio, so as to reduce the signaling traffic in wireless networks.

A Novel Vertical Handoff Scheme Based on Mobility Speed in Integrated WLAN and UMTS Networks

This letter proposes a vertical handoff scheme for integrated WLAN and UMTS that use the mobile Internet Protocol (IP) to reduce the packet loss caused by the ping-pong effect for high mobility users. The simulation results show that the proposed scheme efficiently increases the throughput of high mobility users.

LOCATION-AIDED RESOURCE RESERVATION FOR HANDOFF BASED ON MOBILITY PREDICTION

In this paper, a location-aided resource reservation scheme for handoff based on mobility prediction is proposed for wireless cellular networks. We analyze the performance of the proposed scheme and propose a two-dimensional random walk model for simulation. Performance evaluation is done by computing several key performance criteria, i.e., prediction accuracy, average number of reservation per call, reservation efficiency, and reservation time overhead. The influences of threshold distance, average distance where the mobile station moves along a straight line, location error and sample time are investigated, and the effectiveness of mobility prediction is also evaluated. Performance comparison reveals that the proposed scheme performs better than a solely distance-based scheme without mobility prediction.

Impacts of mobility patterns on mobile IP handoff in wireless LANs

Mobile IP has been adopted to provide seamless services to mobile nodes. Currently, there are many mobile IP handoff schemes proposed at different layers of the network protocol stack. However, the handoff performance under different mobility patterns in terms of velocity and path has been largely ignored by the current research work. In this paper, we present our study of the mobility pattern's impact on the performance of mobile IP handoff by theoretical analysis as well as NS-2 simulations, where both deterministic and hybrid models for mobility patterns have been adopted. Our results show that the performance of mobile IP handoff schemes is directly impacted by the mobility patterns. Moreover, the cross-layer handoff schemes outperform other mobile IP handoff schemes under different mobility patterns. We conclude that the routing update delay is one of main performance bottlenecks in mobile IP handoff. So we propose a new solution to reduce the routing update delay by considering the behaviors at the lower layers such as the link layer. Furthermore, our study also presents a platform for efficient network design due to the fact that the routing update delay is tightly coupled with the deployment of access points.

Analysis of Cognitive Radio Spectrum Access with Optimal Channel Reservation

A Markov chain analysis for spectrum access in licensed bands for cognitive radios is presented and forced termination probability, blocking probability and traffic throughput are derived. In addition, a channel reservation scheme for cognitive radio spectrum handoff is proposed. This scheme allows the tradeoff between forced termination and blocking according to QoS requirements. Numerical results show that the proposed scheme can greatly reduce forced termination probability at a slight increase in blocking probability

Adaptive peer-to-peer streaming over hybrid wireless networks

In this paper, we propose a centralised Peer-to-Peer (P2P) streaming over hybrid wireless networks to mitigate the congestion at the Access Point (AP) in Wireless Local Area Networks (WLANs). In our proposed architecture, an adaptive receiver-driven mechanism is used to coordinate the streaming from multiple senders. We also propose a peer handoff scheme and an AP handoff scheme for video streaming over hybrid wireless networks. The simulation results show that (1) centralised P2P video streaming over a hybrid wireless network can achieve a much better quality compared to traditional WLAN deployment with heavy background traffic, (2) the adaptive receiver-driven mechanism can synchronise packet delivery from multiple senders, thus increasing streaming quality, (3) the peer handoff scheme enables the receiver to maintain a high aggregate throughput from multiple serving-peers and (4) the AP handoff scheme enables the receiver to roam freely through different cells, while maintaining continuous video streaming.

Hierarchical wireless mobile MPLS mechanism using foreign tracking agent based on M∕G∕1 with capacity c queueing model

Within the MultiProtocol Label Switching (MPLS) network, packets with the same forwarding equivalent class can easily be identified by their attached label value. The cross-layer topology associates with access protocol and IP mobility agents. The necessity of agent discovery is reduced and an approach to enhance handoff efficiency proposed. This efficient handoff scheme is performed by a foreign tracking agent (FTA) that plays a role as an administrator of a hierarchy that consists of some foreign agents (FAs) to localise the routing operation of forwarded packets. To analyse the performance of a hierarchical mobile MPLS network, the system is modelled as an M/G/1 system with capacity c, where c represents the number of FAs that can be administered for an FTA. The mean delay time of the FTA to process the forwarding of packets is analysed using M/M/1 with capacity c queueing model. The minimum number of FAs that can be administered for an FTA is derived to improve network performance by minimising mean delay time.

WiBro와 cdma2000 이동통신망간 적은 지연을 위한 L2 핸드오프 방안

최근 이동통신 기술의 발달과 다양한 네트워크의 중복, 사용자의 요구에 따라 기존의 cdma2000 네트워크와 WLAN의 연동과 같은 연구가 활발히 진행되고 있다. 또한, 이동환경에서 높은 전송률을 가진 WiBro 네트워크가 차세대 무선 접속망으로 부각되고 있으며, 이러한 WiBro-cdma2000 네트워크와의 연동은 기존의 WLAN-cdma2000 연동에 비해 높은 시너지 효과를 나타낼 것으로 예상된다. 이를 위해 본 논문에서는 WiBro-cdma2000 연동이 이루어질 경우 단말의 이동성 제공을 위해 패킷손실을 최소화한 L2 핸드오프 방안을 제시한다. 본 논문에서 제안한 L2 핸드오프 방안은 기존의 이동성 제공 방안이 L3 기반의 등록절차를 통한 방안이었음에 착안하여, L3 시그널링이 이루어지기 전, L2 연결설정과정에서 L2 메시지에 핸드오프 정보를 사용하여 패킷손실을 최소화하는 방안을 제시한다. 제안한 방안의 성능을 검증하기 위해 컴퓨터 시뮬레이션을 수행하였으며, 이를 통해 제안한 방안의 우수성을 검증하였다. Since various networks are deployed and the most of users request higher mobility, there are many researches about the interworking between widely deployed 3G network and rapidly boarded WLAN. On the other side, WiBro is focused on as a next generation network, because many people expect that WiBro gives satisfaction about the enough mobility and mass data transmission. So the study of the integration between WiBro and cdma2000 will show better effects than the present study of the integration between WLAN and cdma2000. The L2 handoff proposed in this paper takes advantages over the existing L3 handoff scheme because it does not require the L3 procedure for the mobility unlike the L3 handoff. Through extensive computer simulations, the efficiency of the proposed scheme has been validated.

On the design of mobility management scheme for 802.16-based network environment

In this paper, we investigate the characteristics of IEEE 802.16 and conclude that it is better to equip BS (base station) and SS (subscriber station) with Layer 3 functionality. Therefore, an 802.16 network can act as the backbone network of different subnets for better deployment. Based on the two IEEE Specifications, 802.16-2004 and 802.16e, we propose two kinds of paradigms of the 802.16 network technology for mobile networking. In the first paradigm, a novel concept called middle-domain mobility management in between macro- and micro-domain for 802.16-2004 is proposed. The management scheme of middle-domain is designed to accommodate different micro-mobility protocols in an 802.16-2004 network environment. Moreover, a mathematical analysis and simulation study are presented for performance evaluation. In the second paradigm, by comparing with traditional overlay networks (e.g. GPRS/WLAN), we have found that the characteristics for the 802.16e/802.11 overlay network are actually different from traditional overlay networks. To provide more efficient vertical handoff, a novel protocol called speed-based vertical handoff scheme (SVH) is proposed. A Simulation study has demonstrated that SVH can achieve a better performance than its WLAN-first counterpart in terms of less signaling and fewer packet losses.

Performance Optimizations for Deploying VoIP Services in Mesh Networks

In the recent past, there has been a tremendous increase in the popularity of VoIP services as a result of huge growth in broadband access. The same voice-over-Internet protocol (VoIP) service poses new challenges when deployed over a wireless mesh network, while enabling users to make voice calls using WiFi phones. Packet losses and delay due to interference in a multiple-hop mesh network with limited capacity can significantly degrade the end-to-end VoIP call quality. In this work, we discuss the basic requirements for efficient deployment of VoIP services over a mesh network. We present and evaluate practical optimizing techniques that can enhance the network capacity, maintain the VoIP quality and handle user mobility efficiently. Extensive experiments conducted on a real testbed and ns-2 provide insights into the performance issues and demonstrate the level of improvement that can be obtained by the proposed techniques. Specifically, we find that packet aggregation along with header compression can increase the number of supported VoIP calls in a multihop network by 2-3 times. The proposed fast path switching is highly effective in maintaining the VoIP quality. Our fast handoff scheme achieves almost negligible disruption during calls to roaming clients