Vertical Handoff Decision Algorithms Research Articles

Vertical Handoff Decision Algorithm combined Improved Entropy Weighting with GRA for Heterogeneous Wireless Networks

Future network scenario will be a heterogeneous wireless network environment composed of multiple networks and multimode terminals (MMT). Seamless switching and optimal connectivity for MMT among different networks and different services become extremely important. Here, a vertical handoff algorithm combined an improved entropy weighting method based on grey relational analysis (GRA) is proposed. In which, the improved entropy weight method is used to obtain the objective weights of the network attributes, and GRA is done to rank the candidate networks in order to choose the best network. Through simulation and comparing the results with other vertical handoff decision algorithms, the number of handoffs and reversal phenomenon are reduced with the proposed algorithm, which shows a better performance.

Vertical Handoff with Predictive Received Signal Strength in Next Generation Wireless Network

Since the last few decades, tremendous innovations and inventions have been observed in every field, but especially in wireless network technology. The prevailing demand curves and trends in this particular area of communication show the importance of real-time multimedia applications over several networks with guaranteed quality of service (QoS). The Next Generation Wireless Network (NGWN) consists of heterogeneous wireless networks that will grant high data rate and bandwidth to mobile users. The primary aim of Next Generation Wireless Network (NGWN) is to conceal heterogeneities and to achieve convergence of diverse networks to provide seamless mobility. So that mobile user can move freely between networks without losing the connection or changing the setting at any moment. When the mobile user moves between different networks, there is a requirement to handover the channel, from one network to another by considering its services, features and user preferences. Channel handover between two different networks is done with the help of vertical handoff (VHO). In a heterogeneous environment, numerous technologies co-exist with their unique characteristics. Therefore, it is very difficult to design efficient handoff decision algorithm. The poorly designed handoff algorithm tends to increase the traffic load and, thereby tend to dramatic decrease in quality of service. A mobile node equipped with multiple network interfaces will be able to access heterogeneous wireless access network. But the availability of alternatives give rise to a problem of unnecessary handoff. To avoid this, we have proposed a decision algorithm based on predictive received signal strength, hysteresis margin and dwell time to select an optimum target network. The handoff policies are designed using received signal strength (RSS), available bandwidth, service cost, user preference, type of application and network condition to reduce the number of handoffs, decision delay, probability of handoff failure and probability of unnecessary handoff. We have also made a comparative analysis of various vertical handoff decision algorithms in this paper.

Survey on Evaluation Models of Vertical Handoff Decision Algorithms

Heterogeneous systems, Vertical Handoff calculations (VHAs) used to permit mobile terminals (MT) to keep up the system association when versatile hub switch starting with one remote system then onto the next one. The Vertical Handover Decision is NP-Hard issue, thus assessment of all VHA is imperative perspective while working with Vertical Handoff calculations. In this paper, we concentrated on different assessment models which were utilized by past analysts. We likewise concentrated on the different parameters which are imperative for execution examination of VHAs and represent the absence of a legitimate assessment model to look at the different Vertical Handoff Algorithms (VHAs) that have been proposed in the writing.

Signal Strength Ratio Based Vertical Handoff Decision Algorithms in Integrated Heterogeneous Networks

In this paper, we propose the signal strength ratio (SSR) based vertical handoff (VHO) algorithms and the averaged received signal strength (ARSS) based VHO algorithms for integrated networks of wireless local area network (WLAN) and 3G network. The performance of our proposed VHO algorithms with hysteresis and dwell timer approaches has been investigated for two different topologies of integrated heterogeneous network. Two different network topologies consider two different types of radio cell arrangement. A mobile terminal (MT) is moving within the coverage area of WLAN and 3G with constant velocity. The received signal strength at the MT of interest is measured at different sampling instant. The received signal strength with other additional parameters is used to determine the condition of VHO. We evaluate the decision delay, and the number of vertical handoffs between WLAN and 3G network using the proposed VHO algorithms. We compare the performance of our proposed VHO algorithms with existing RSS based VHO algorithm. Our proposed SSR and ARSS based VHO algorithms provide less decision delay as compared to existing RSS based VHO algorithm. Further, ARSS with dwell timer based VHO algorithm provides better performance than other VHO algorithms.

An Overview of Decision Techniques for Vertical Handoff Across Wireless Heterogeneous Networks

Future wireless communication networks popularly known as beyond third generation (B3G) or Fourth generation (4G) networks will likely consist of heterogeneous wireless networks which will be IP -Centric based.These networks will offer a wide range of high data multimedia services to mobile users. To achieve this, Vertical Handoff (VHO) is considered as the method of realization and it is defined as the process by which users will seamlessly roam amongst theseheterogeneous networks while communicating. To realize VHO, effective and efficient algorithms for accurate VHO decision are of utmost importance and hence form an area of current research focus. In this regards, several efforts have been made and it is th e specific objective of this paper to provide an overview of efforts made thus far while discussing related VHO concepts. Specifically, handoff types, handoff process and classification of vertical handoff, metrics required, and existing works are presente d. We seek to provide a concise background for not just VHO decision algorithms but also for understanding the basic concept of VHO. Mini-review Article

Markov-based vertical handoff decision algorithms in heterogeneous wireless networks

In this paper, we propose a received signal strength (RSS)-based single-attribute handoff decision algorithm at first, and investigate handoff decision model based on connection lifetime, which can keep mobile terminals (MTs) staying long enough in the preferred network. Since the preferred quality of service (QoS) parameters may be distinct among different MTs, we then formulate the vertical handoff decision problem as a Markov decision process, with the objectives of maximizing the expected total reward and minimizing average number of handoffs. A reward function is constructed to assess the QoS during each connection, and the G1 and entropy methods are applied in an iterative way, by which we can work out a stationary deterministic handoff decision policy. Numerical results demonstrate the superiority of our proposed schemes compared with other existing algorithms.

Design of Vertical Handoff Initiation and Decision Algorithm in Heterogeneous Wireless Networks

Vertical handoff decision (VHD) algorithms are essential components of the architecture of the forthcoming Fourth Generation (4G) heterogeneous wireless networks. These algorithms need to be designed to provide the required Quality of Service (QoS) to a wide range of applications while allowing seamless roaming among a multitude of access network technologies. This work mainly focuses on vertical handoff initiation and decision. The handoff initiation is critically important to keep the unnecessary handoffs and their failures at a low level. On the other hand, to maximize the end-user’s satisfaction levels, the decision to select the best network among other available candidates also plays an important role. The proposed algorithm provides a complete framework to perform vertical handoffs in a heterogeneous wireless network.

A Markov-Based Multi-Attribute Vertical Handoff Decision Algorithm

Many vertical handoff decision algorithms have not considered the impact of call dropping during the vertical handoff decision process. Besides, most of current multi-attribute vertical handoff algorithms cannot predict users’ specific circumstances dynamically. In this paper, we formulate the vertical handoff decision problem as a Markov decision process, with the objective of maximizing the expected total reward during the handoff procedure. A reward function is formulated to assess the service quality during each connection. The G1 and entropy methods are applied in an iterative way, by which we can work out a stationary deterministic policy. Numerical results demonstrate the superiority of our proposed algorithm compared with the existing methods.

Vertical Handover in Next Generation Wireless Networks

The next generation wireless networks will support the vertical handoff procedure in which users can keep the connections when they change from one access network to another. Although diffferent vertical handoff decision algorithms have been proposed in the literature recently. This paper presents an exhaustive state of the art survey about handover alogorithms in heterogeneous networks. With the advent of novel networks technologies, researchers have been working on how to implement and ensure that QoS is achieved in heterogeneous networks. We believe that there have been some improvements, but there is much to do. Additionally, the survey shows the great effort which has been undertaken by the research community in order to address the topic over these years. The blooming of ideas is plethoric and gives us a view about the tremendous scope covered by the subject.

Case study on handoff strategies for wireless overlay networks

One of the most challenging topics for next‐generation wireless networks is the process of vertical handoff since many of wireless technologies overlap each other and build a heterogeneous topology. Several parameters, pertaining to user/application requirements and network conditions, such as data rate, service cost, network latency, speed of mobile, and etc. must be considered in the handoff process of heterogeneous networks along with RSSI information. In this paper, adaptive fuzzy logic‐based vertical handoff decision‐making algorithms are presented for wireless overlay networks which consist of GSM/GPRS/Wi-Fi/UMTS/WiMAX technologies. The parameters data rate, monetary cost, speed of mobile and RSSI information are processed as inputs of the proposed fuzzy‐based systems. According to these parameters, an output value, which varies between 1 and 10, is produced. This output value is utilized to determine whether a handoff process is necessary or not and to select the best candidate access point in the vicinity. The results show that, compared to the traditional RSSI‐based algorithm significantly enhanced outcomes can be achieved for both user and network as a consequence of the proposed fuzzy‐based handoff systems. The simulation results are also compared with those of classical MADM (Multiple Attribute Decision Making) method, i.e. SAW (Simple Additive Weighting). According to the results obtained, the proposed vertical handoff decision algorithms are able to determine whether a handoff is necessary or not, properly, and select the best candidate access network considering the aforementioned parameters. Moreover, fuzzy‐based algorithm noticeably reduces the number of handoffs compared to SAW‐based algorithm.

Analytic Performability Model of Vertical Handoff in Wireless Networks

Problem statement: The next generation wireless systems should be designed to support heterogeneous traffic with seamless mobility. A single network alone cannot cope up with such heterogeneous requirements. Hence it is desirable to interoperate between diverse and complementary Radio Access Technologies (RATs). In such system, user will switch between different Radio Access Technologies (RATs) to satisfy the User/application requirement and this process is known as Vertical Handoff (VHO). The process of network switching had three phases, network discovery, handoff decision and execution. The decision phase played a crucial role in resource utilization and user/application Quality of Service (QoS) requirement. Hence it was essential to model and evaluate the handoff decision system along with VHO system model. Approach: The traditional performance models were optimistic models and would evaluate the system performance under ideal condition by ignoring failures and recovery in the system. The availability models were conservative models and would assess the availability/reliability of the system. The performabality models were combined models of performance and reliability. The performablity models were more realistic models of the system due to the simultaneous consideration of performance and reliability. Here the VHO process of a next generation wireless system was modeled and evaluated by an analytic performablity model and performance of decision system is evaluated through the sensitivity analysis of VHO decision parameter. Results: In VHO performance evaluation, the metrics of performance evaluation are handoff dropping probability and new call blocking probability. The dynamics of these metrics are depends on set of wireless network parameter such as Available Bandwidth (ABW), users, Bit Error Rate (BER) and network traffic. The ABW, BER and network traffic is also parameter for VHO decisions. The results of performance evaluation are used to develop a novel intelligent vertical handoff decision technique to achieve optimum tradeoff between set of handoff decision criteria. Finally, sensitivity analysis of system parameters on four traffic classes and two vertical handoff decision algorithms along with intelligent vertical handoff decision method were presented. Conclusion: The results of sensitivity analysis depicted that the VHO process in next generation wireless system needs intelligent criteria based technique at the decision making phase of VHO process.

Vertical Handoff Decision Algorithms for Providing Optimized Performance in Heterogeneous Wireless Networks

There are currently a large variety of wireless access networks, including the emerging vehicular ad hoc networks (VANETs). A large variety of applications utilizing these networks will demand features such as real-time, high-availability, and even instantaneous high-bandwidth in some cases. Therefore, it is imperative for network service providers to make the best possible use of the combined resources of available heterogeneous networks (wireless area networks (WLANs), Universal Mobile Telecommunications Systems, VANETs, Worldwide Interoperability for Microwave Access (WiMAX), etc.) for connection support. When connections need to migrate between heterogeneous networks for performance and high-availability reasons, seamless vertical handoff (VHO) is a necessary first step. In the near future, vehicular and other mobile applications will be expected to have seamless VHO between heterogeneous access networks. With regard to VHO performance, there is a critical need to develop algorithms for connection management and optimal resource allocation for seamless mobility. In this paper, we develop a VHO decision algorithm that enables a wireless access network to not only balance the overall load among all attachment points (e.g., base stations and access points) but also maximize the collective battery lifetime of mobile nodes (MNs). In addition, when ad hoc mode is applied to 3/4G wireless data networks, VANETs, and IEEE 802.11 WLANs for a more seamless integration of heterogeneous wireless networks, we devise a route-selection algorithm for forwarding data packets to the most appropriate attachment point to maximize collective battery lifetime and maintain load balancing. Results based on a detailed performance evaluation study are also presented here to demonstrate the efficacy of the proposed algorithms.

An MDP-Based Vertical Handoff Decision Algorithm for Heterogeneous Wireless Networks

The architecture for the Beyond 3rd Generation (B3G) or 4th Generation (4G) wireless networks aims at integrating various heterogeneous wireless access networks. One of the major design issues is the support of vertical handoff. Vertical handoff occurs when a mobile terminal switches from one network to another (e.g., from wireless local area network to code-division multiple-access 1x radio transmission technology). The objective of this paper is to determine the conditions under which vertical handoff should be performed. The problem is formulated as a Markov decision process with the objective of maximizing the total expected reward per connection. The network resources that are utilized by the connection are captured by a link reward function. A signaling cost is used to model the signaling and processing load incurred on the network when vertical handoff is performed. The value iteration algorithm is used to compute a stationary deterministic policy. For performance evaluation, voice and data applications are considered. The numerical results show that our proposed scheme performs better than other vertical handoff decision algorithms, namely, simple additive weighting, the technique for order preference by similarity to ideal solution, and Grey relational analysis.

Evaluation and Improvement of Vertical Handoff Algorithms in Heterogeneous Wireless Networks

Vertical handoff is the basic requirement for convergence of different access technologies and has received tremendous attention from the academia and industry. In recent years, many research works have focused on vertical handoff decision algorithms. However, the evaluation scenarios in different papers are quite different. Thus it is difficult to compare different algorithms in a fair way. This paper analyzes the general motion models of mobile nodes and identifies a set of novel performance evaluation models. Equipped with the models, this paper analyzes the performance of two types of decision algorithms: Hysteresis based algorithm and dwelling-timer based algorithm. Based on the above, a novel vertical handoff decision algorithm, self-adaptive vertical handoff algorithm (SAVA) is presented. Simulations show that SAVA can achieve better performance compared with the conventional methods.

Multiservice Vertical Handoff Decision Algorithms

Future wireless networks must be able to coordinate services within a diverse-network environment. One of the challenging problems for coordination is vertical handoff, which is the decision for a mobile node to handoff between different types of networks. While traditional handoff is based on received signal strength comparisons, vertical handoff must evaluate additional factors, such as monetary cost, offered services, network conditions, and user preferences. In this paper, several optimizations are proposed for the execution of vertical handoff decision algorithms, with the goal of maximizing the quality of service experienced by each user. First, the concept of policy-based handoffs is discussed. Then, a multiservice vertical handoff decision algorithm (MUSE-VDA) and cost function are introduced to judge target networks based on a variety of user- and network-valued metrics. Finally, a performance analysis demonstrates that significant gains in the ability to satisfy user requests for multiple simultaneous services and a more efficient use of resources can be achieved from the MUSE-VDA optimizations.