Immune optimization algorithm for solving vertical handoff decision problem in heterogeneous wireless network

In heterogeneous wireless network environment, wireless local area network (WLAN) is usually deployed within the coverage of a cellular network to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. Vertical handoffs between the WLAN and the cellular network maybe occur frequently. As for the vertical handoff performance, there is a critical requirement for developing algorithms for connection management and optimal resource allocation for seamless mobility. In this paper, we develop a mathematical model for vertical handoff decision problem, and propose a multi-objective optimization immune algorithm-based vertical handoff decision scheme. The proposed scheme can enable a wireless access network not only to balance the overall load among all base stations and access points but also maximize the collective battery lifetime of mobile terminals. Results based on a detailed performance evaluation study are also presented here to demonstrate the efficacy of the proposed scheme.     

An End-To-End Approach for Transparent Mobility Across Heterogeneous Wireless Networks

With the advent of a myriad of wireless networking technologies, a mobile host today can potentially be equipped with multiple wireless interfaces that have access to different wireless networks. It is widely perceived that future generation wireless networks will exhibit a similar trend in supporting a large variety of heterogeneous wireless access technologies that a mobile host can choose from. In this paper, we consider such a multi-homed mobile host and propose an end-to-end solution that enables the seamless use of heterogeneous wireless access technologies. The unique features of the proposed solution include: (i) a purely end-to-end approach to handle host mobility that requires no support from the underlying network infrastructure, (ii) seamless vertical handoffs when the mobile host migrates from one access network to another, (iii) ability to support different congestion control schemes for a live connection traversing different interfaces, and (iv) effective bandwidth aggregation when the mobile host has simultaneous access to multiple networks. We present the design and details of the proposed approach, and evaluate its performance through simulations and real-life field experiments.     

Fast Handoff in SIP-Based Next Generation Mobile Networks

It is commonly held that next generation mobile systems will be developed on the Internet in combination with diverse access technologies, as the future network architecture will be the coming together of various overlapping wireless access networks. Integrating various wireless networks in future heterogeneous networking environments poses many difficulties, the most critical challenge of which is efficient support for seamless mobility. SIP is a promising nominee for managing mobility in heterogeneous networks as it provides mobility within the application layer and the characteristics of the lower layer protocols are invisible to it. However, the performance of SIP-based mobility management is downgraded, resulting from its adoption of TCP/UDP for signaling and its strict separation between the lower layers and the application layer of the protocol stack. In this paper, a SIP-based cross-layer design for fast handoffs is proposed to shorten the service interruption time when a mobile node crosses the overlapped area of a WLAN/3G cellular system. As will be shown by the simulation results, the SIP-based solution proposed in this paper effectively lessens the handoff delays caused by either the horizontal handoff or vertical handoff in future all-IP heterogeneous wireless networks.     

A Noncooperative Game-Theoretic Framework for Radio Resource Management in 4G Heterogeneous Wireless Access Networks

Fourth generation (4G) wireless networks will provide high-bandwidth connectivity with quality-of-service (QoS) support to mobile users in a seamless manner. In such a scenario, a mobile user will be able to connect to different wireless access networks such as a wireless metropolitan area network (WMAN), a cellular network, and a wireless local area network (WLAN) simultaneously. We present a game-theoretic framework for radio resource management (that is, bandwidth allocation and admission control) in such a heterogeneous wireless access environment. First, a noncooperative game is used to obtain the bandwidth allocations to a service area from the different access networks available in that service area (on a long-term basis). The Nash equilibrium for this game gives the optimal allocation which maximizes the utilities of all the connections in the network (that is, in all of the service areas). Second, based on the obtained bandwidth allocation, to prioritize vertical and horizontal handoff connections over new connections, a bargaining game is formulated to obtain the capacity reservation thresholds so that the connection-level QoS requirements can be satisfied for the different types of connections (on a long-term basis). Third, we formulate a noncooperative game to obtain the amount of bandwidth allocated to an arriving connection (in a service area) by the different access networks (on a short-term basis). Based on the allocated bandwidth and the capacity reservation thresholds, an admission control is used to limit the number of ongoing connections so that the QoS performances are maintained at the target level for the different types of connections.     

Vertical handoff in integrated CDMA and WLAN systems

Future wireless networks are expected to consist of different types of wireless networks such as code division multiple access (CDMA) networks and public wireless local area networks (WLANs). The integrated network will require vertical handoffs between different networks. In this letter, we propose vertical hard- and soft-handoff algorithms and evaluate their performance in commercial wireless networks.     

Multicasting with selective delivery: a SafetyNet for vertical handoffs

In the future, mobility support will require handling roaming in heterogeneous access networks. In order to enable seamless roaming it is necessary to minimize the impact of the vertical handoffs. Localized mobility management schemes such as Fast Handovers for Mobile IPv6 (FMIPv6) and Hierarchical Mobile IPv6 do not provide sufficient handoff performance, since they have been designed for horizontal handoffs. In this paper, we propose the SafetyNet protocol, which allows a Mobile Node to perform seamless vertical handoffs. Further, we propose the SafetyNet handoff timing algorithm, to enable a Mobile Node to delay or even completely avoid upward vertical handoffs. We implement the SafetyNet protocol and compare its performance with the FMIPv6 protocol in our wireless test bed and analyze the results. The experimental results indicate that the proposed SafetyNet protocol can provide an improvement of up to 95% for TCP performance in vertical handoffs, when compared with FMIPv6 and an improvement of 64% over FMIPv6 with bicasting. We use numerical analysis of the protocol to show that its over the air signaling and data transmission overhead is comparable to FMIPv6 and significantly smaller than that of FMIPv6 with bicasting.     

Pre-scan based fast handoff scheme for enterprise IEEE 802.11 networks

In IEEE 802.11 networks, many access points (APs) are required to cover a large area due to the limited coverage range of APs, and frequent handoffs may occur while a station (STA) is moving in an area covered by several APs. However, traditional handoff mechanisms employed at STAs introduce a few hundred milliseconds delay, which is far longer than what can be tolerated by some multimedia streams such as voice over Internet protocol (VoIP), it is a challenging issue for supporting seamless handoff service in IEEE 802.11 networks. In this paper, we propose a pre-scan based fast handoff scheme within an IEEE 802.11 enterprise wireless local area network (EWLAN) environment. The proposed scheme can help STA obtain the best alternative AP in advance after the pre-scan process, and when the handoff is actually triggered, STA can perform the authentication and reassociation process toward the alternative AP directly. Furthermore, we adopt Kalman filter to minimize the fluctuation of received signal strength (RSS), thus reducing the unnecessary pre-scan process and handoffs. We performed simulations to evaluate performance, and the simulation results show that the proposed scheme can effectively reduce the handoff delay.     

Vertical handoffs in wireless overlay networks

No single wireless network technology simultaneously provides a low latency, high bandwidth, wide area data service to a large number of mobile users. Wireless Overlay Networks - a hierarchical structure of room-size, building-size, and wide area data networks - solve the problem of providing network connectivity to a large number of mobile users in an efficient and scalable way. The specific topology of cells and the wide variety of network technologies that comprise wireless overlay networks present new problems that have not been encountered in previous cellular handoff systems. We have implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks. Our goal is to provide a user with the best possible connectivity for as long as possible with a minimum of disruption during handoff. Results of our initial implementation show that the handoff latency is bounded by the discovery time, the amount of time before the mobile host discovers that it has moved into or out of a new wireless overlay. This discovery time is measured in seconds: large enough to disrupt reliable transport protocols such as TCP and introduce significant disruptions in continuous multimedia transmission. To efficiently support applications that cannot tolerate these disruptions, we present enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these enhancements lead to a best-case handoff latency of approximately 170 ms with a 1.5% overhead in terms of network resources. For handoffs between building-size and wide-area data networks, the best-case handoff latency is approximately 800 ms with a similarly low overhead. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Simple Remedy for Idle Mode via Proxy MIP

While recent wireless networks begin to support mobile Internet protocol (MIP), even the latest wireless network technologies such as IEEE 802.16 wireless metropolitan area networks (WMANs), IEEE 802.11 wireless local area networks (WLANs), and high-speed downlink packet access (HSDPA) are limited in exploiting idle mode under mobile environments in which MIP is employed since they are designed without considering MIP combined with idle mode. In other words, an idle mobile station (MS) should perform MIP handoffs despite that it cannot receive anything while staying in idle mode, and hence, it incurs inexpedient operations. We propose a simple protocol, which makes idle mode integrated with MIP seamlessly by utilizing proxy MIP (PMIP). It processes MIP handoffs on behalf of idle MS, thus allowing idle MS to stay in idle mode consistently.     

Heterogeneous Wireless Networks: Configuration and Vertical Handoff Management

Vertical handoff is one of the most important issues for the next generation heterogeneous wireless networks. However, in many situations, unbeneficial vertical handoffs occur across intersystem heterogeneous networks cause network performance degradation. Therefore, we propose a novel configuration architecture that can be deployed in the next generation of wireless networks. Second, we propose a predictive and adaptive Vertical Handoff Decision Scheme that optimizes the handoff initiation time as well as selection of the most optimal network. The proposed vertical handoff decision algorithm considers the technology type as well as the Signal to Interference Ratio (SIR), the Mobile Station (MS) velocity, the user preferences, the applications requirements and the terminal capabilities as the most important factors to make vertical handoff decision. In order to minimize handoff costs, the proposed decision algorithm uses the dwell timer concept. The handoff costs are analyzed in terms of unnecessary and unbeneficial handoffs rate.The simulation results show that the reduction of unnecessary handoffs proposed in our vertical handoff decision scheme reduces the handoff blocking probability, the packets loss rate and the handoff overhead     

Class-based quality of service over air interfaces in 4G mobilenetworks

We present a framework for quality of service provisioning over the air interfaces in future wireless networks, including 3G enhancement and 4G mobile networks. The framework is based on the paradigm of service classes, wherein each class can exhibit a characteristic behavior in terms of resource allocation over the air interface. Using this QoS framework, future wireless network operators can define their own sets of service classes, choose the preferred way of implementing the QoS behavior of these classes, and offer class-based pricing schemes. The user application can choose the service class that best suits its expectations in terms of QoS and cost of access. A class-based bandwidth scheduling scheme is described as a mechanism to implement this QoS framework over CDMA air interfaces. This scheme incorporates the paradigm of service classes, in conjunction with fair resource allocation and air interface congestion resilience, while allocating air interface bandwidth to mobile users     

Adding network-layer intelligence to mobile receivers for solving spurious TCP timeout during vertical handoff

With the help of mobile IP/IPv6 and soft handoff, ongoing TCP sessions can remain active and handoff packet loss can be avoided. However, TCP still faces several performance degradation issues due to the disparities in bandwidth and propagation delay between different access networks. Particularly, during vertical handoffs, some undesirable phenomena may erroneously trigger TCP congestion-control actions and thus degrade TCP performance. In this article we tackle the spurious timeout problem frequently associated with handovers from fast to slow links. We propose three network-layer schemes: fast ACK, slow ACK, and ACK delaying. These schemes require only minor modifications to the network layer of mobile receivers and no change to the TCP protocol and the TCP sender. The simulation results show that these schemes can effectively improve TCP performance during soft vertical handoffs     

A novel software‐defined networking approach for vertical handoff in heterogeneous wireless networks

We propose a novel vertical handoff scheme with the support of the software‐defined networking technique for heterogeneous wireless networks. The proposed scheme solves two important issues in vertical handoff: network selection and handoff timing. In this paper, the network selection is formulated as a 0‐1 integer programming problem, which maximizes the sum of channel capacities that handoff users can obtain from their new access points. After the network selection process is finished, a user will wait for a time period. Only if the new access point is consistently more appropriate than the current access point during this time period, will the user transfer its inter‐network connection to the new access point. Our proposed scheme ensures that a user will transfer to the most appropriate access point at the most appropriate time. Comprehensive simulation has been conducted. It is shown that the proposed scheme reduces the number of vertical handoffs, maximizes the total throughput, and user served ratio significantly. Copyright © 2016 John Wiley & Sons, Ltd.     

A flow-based network monitoring framework for wireless mesh networks

As an extension of wireless ad hoc and sensor networks, wireless mesh networks recently were developed as a key solution to provide high-quality multimedia services and applications, such as voice, data, and video, over wireless personal area networks, wireless local area networks, and wireless metropolitan area networks. A WMN has a hybrid network infrastructure with a backbone and an access network and usually is operated in both ad hoc and infrastructure modes with self-configuration and self-organization capabilities. In this article, we review security challenges, attacks, and countermeasures in the physical, medium access control (MAC), and network layers of wireless mesh backbone and access networks. We then extend the concept of traffic flow from IP networks and define meshflow in wireless mesh networks. Based on this new concept, we propose a comprehensive framework to realize network monitoring, user and router profiling, application and service balancing, and security protection in wireless mesh backbone networks. Practical issues and design trade-offs for implementing the proposed framework in real systems also are discussed.     

A Seamless Handoff Mechanism for DHCP-Based IEEE 802.11 WLANs

IEEE 802.11 wireless networks have gained great popularity. However, handoff is always a critical issue in this area. In this paper, we propose a novel seamless handoff mechanism for IEEE 802.11 wireless networks which support IEEE 802.11i security standard. Our approach consists of a dynamic tunnel establishing procedure and a seamless handoff mechanism. Both intra- and inter-subnet handoff cases are considered in our seamless handoff approach. Our work focuses on handoffs in DHCP-based IP networks rather than mobile IP-supported networks, but the proposed scheme can be easily tailored to mobile IP-supported networks.     

Seamless Streaming Media for Heterogeneous Mobile Networks

As the mobile networking technologies evolve, people are able to access the Internet through heterogeneous wireless access networks, such as WLAN, GPRS, 3G and Beyond 3G networks. For the coverage, bandwidth and cost of these heterogeneous mobile access networks are quite different, a mobile host may hand over among them, and this is called vertical handoffs. One of the most important issues for heterogeneous mobile networks is that vertical handoffs may degrade the quality of the time-sensitive streaming media services, even interrupt them. To overcome the problem, in the paper a multicast-based redundant streaming architecture is proposed. The proposed architecture is implemented in the all-IPv6 heterogeneous mobile networks. Five experiments are performed to evaluate the performance of the proposed architecture. The experimental results and the analysis show that the proposed architecture is capable of providing seamless streaming services even if the vertical handoffs or the traffic congestion occurs. Moreover, it is found that the traffic overhead is only 1.0368% per vertical handoff for each mobile access network, and thus the feasibility of the proposed architecture is demonstrated.

5G mobile terminals with advanced QoS-based user-centric aggregation (AQUA) for heterogeneous wireless and mobile networks

In this paper we present an advanced QoS provisioning module with vertical multi-homing framework for future fifth generation (5G) mobile terminals with radio network aggregation capability and traffic load sharing in heterogeneous mobile and wireless environments. The proposed 5G mobile terminal framework is leading to high performance utility networks with high QoS provisioning for any given multimedia service, higher bandwidth utilization and multi-RAT capabilities. It is using vertical multi-homing and virtual QoS routing algorithms within the mobile terminal, that is able to handle simultaneously multiple radio network connections via multiple wireless and mobile network interfaces. Our 5G proposal is user-centric, targeted to always-on connectivity, maximal network utilization, maximal throughput, seamless handovers and performances improvement by using vertical multi-homing, as well as session continuity. The performance of our proposed mobile terminal framework for 5G is evaluated using simulations and analysis with multimedia traffic in heterogeneous mobile and wireless scenarios with coexistence of multiple radio access technologies, such as 3G, 4G as well as future 5G radio access networks.     

Proactive load balancing with admission control for heterogeneous overlay networks

The next generation wireless networks will be the coexistence of heterogeneous wireless technologies. Balancing the traffic load among different networks can effectively utilize the overall radio resources in the system. In this paper, we propose an efficient load balancing scheme for the heterogeneous overlay systems, which is applied in the call admission control process. If the available network(s) cannot provide enough resource for the request call without degrading the quality‐of‐service (QoS) obtained by the ongoing calls, the system will perform load balancing operations first by initiating vertical handoffs among networks in order to create more rooms for the request call. The load balancing algorithm is to minimize the variance between the network utilizations of the entire system, which can be formulated as a quadratic binary programming problem. Simulation results show that the proposed scheme can admit more calls into the system compared with the other three reference schemes and then improve the overall throughput. Meanwhile, the scheme can keep the networks working in effective states and provide a better QoS support for users. Copyright © 2011 John Wiley & Sons, Ltd.     

A Robust Seamless Handover Scheme for the Support of Multimedia Services in Heterogeneous Emerging Wireless Networks

With the rapid development of wireless technologies and numerous types of mobile devices, the need to support seamless multimedia services in Mobile and Ubiquitous Computing (MUC) is growing. To support the seamless handover, several mobility protocols such as Mobile IPv6 (MIPv6) (Johnson et al., Mobility Support in IPv6, IETF, RFC 3775, 2004) and fast handover for the MIPv6 (FMIPv6) (Koodli et al. Past handovers for mobile IPv6 (FMIPv6), IETF, RFC 4068, 2005) were developed. However, MIPv6 depreciates the Quality-of-Service (QoS) especially in multimedia service applications because of the long handover latency and packet loss problem. To solve these problems in the MIPv6, FMIPv6 is proposed in the Internet Engineering Task Force (IETF). However, FMIPv6 is not robust for the multimedia services in heterogeneous emerging wireless networks when the MN may move to another visited network in contrast with its anticipation. In MUC, the possibility of service failure is more increased because mobile users can frequently change the access networks according to their mobility in heterogeneous wireless access networks such as 3Generation (3G), Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMax) and Bluetooth co-existed. In this paper, we propose a robust seamless handover scheme for the multimedia services in heterogeneous emerging wireless networks. The proposed scheme reduces the handover latency and handover initiation time when handover may fail through the management of tentative Care-of Addresses (CoAs) that does not require Duplicate Address Detection (DAD). Through performance evaluation, we show that our scheme provides more robust handover mechanism than other scheme such as FMIPv6 for the multimedia services in heterogeneous emerging wireless networks.     

Improving handoff performance by utilizing ad hoc links in multi-hop cellular systems

Handoff performance is a critical issue for mobile users in wireless cellular networks, such as GSM networks, 3G networks, and next generation networks (NGNs). When ad hoc mode is introduced to cellular networks, multi-hop handoffs become inevitable, which brings in new challenging issues to network designers, such as how to reduce the call dropping rate, how to simplify the multi-hop handoff processes, and how to take more advantage of ad hoc mode for better resource management, and most of these issues have not been well addressed as yet. In this paper, we will address some of the issues and propose a scheme, Ad-hoc-Network–Embedded handoff Assisting Scheme (ANHOA), which utilizes the self-organizing feature of ad hoc networks to facilitate handoffs in cellular networks and provide an auxiliary way for mobile users to handoff across different cells. Moreover, we also propose a scheme enabling each BS to find the feasible minimum reservation for handoff calls based on the knowledge of adjacent cells’ traffic information. Due to the use of multi-hop connections, our scheme can apparently alleviate the reservation requirement and lower the call blocking rate while retaining higher spectrum efficiency. We further provide a framework for information exchange among adjacent cells, which can dynamically balance the load among cells. Through this study, we demonstrate how we can utilize ad hoc mode in cellular systems to significantly improve the handoff performance.