基于层次分析法的WLAN/蜂窝网络切换判决算法

针对WLAN/蜂窝异构网络的特点,提出了基于层次分析法的网络切换判决算法。算法综合考虑了网络状态及用户业务特征,分别采用SAW法和TOPSIS法对网络组合权向量进行了计算,仿真表明基于层次分析法的TOPSIS法与SAW法相比,更适合时延敏感业务的网络切换判决。     

异构无线网络的自适应垂直切换判决算法

在未来的异构环境中,网络间的垂直切换将对QoS保证产生重要影响。针对移动终端在异构网络间切换不理想的问题,提出了一种自适应的垂直切换判决算法。采用基于用户多应用的代价函数对接入网络进行评估与选择,综合考虑移动终端当前的电池电量,判断当前业务是否需要进行网络切换,使移动终端能自适应地进行切换判决。仿真结果表明,该算法可以有效地延长移动终端的工作时间,减少乒乓效应,提高系统的切换性能,改善业务的QoS。     

一种LTE与WLAN间垂直切换新算法

为提高用户在异构网络中的服务质量(QoS),减少切换产生的乒乓效应,文中提出了一种LTE和WLAN网络垂直切换新算法。该算法考虑了衰落对接收信号强度(RSS)的影响,基于RSS选出目标网络,根据用户移动速度并结合代价函数选出最佳网络,代价函数中采用了层次分析法来确定时延、资费和用户偏好等参数的权重。仿真结果表明,文中所提的垂直切换算法有效降低了“乒乓效应”,并提高了通信网络的服务质量。     

异构无线网络中基于权重平衡的接入选择算法

下一代异构无线网络中,用户业务需求将会更加多样化。针对目前网络接入算法在确定判决属性权重时存在片面性问题,文章提出了一种基于权重平衡的接入选择算法,首先利用改进的层次分析法获取判决属性的主观权重,同时通过熵值法获取属性的客观权重,然后对主客观权重进行平衡处理,最后将得到的综合权重通过简单加权法对各网络进行综合评价以及确定目标接入网络。仿真结果表明,该算法能在满足用户业务需求的基础上,准确地接入最优网络,同时减小“乒乓效应”带来的影响,提高了网络的性能。     

基于模糊层次—熵权法的自适应垂直切换算法

针对当前异构网络中,采用多决策属性的垂直切换算法难以动态调整网络属性的权重值,从而无法满足用户服务质量(QoS)的需求问题,文章以接入最优的异构无线网络和保障用户QoS为目标,提出基于模糊层次—熵权法的自适应垂直切换算法.首先,根据用户对网络属性的不同要求,采用主观模糊层次赋权与客观熵权法结合的方式构建网络属性优化模型...     

异构无线网络中基于模糊逻辑的分级垂直切换算法

在异构无线网络中,针对综合考虑网络端和用户端参数的垂直切换算法,参数权重难以确定,同时基于模糊逻辑的垂直切换算法存在复杂度高的问题,该文提出一种基于模糊逻辑的分级垂直切换算法。首先,将接收信号强度(RSS)、带宽、时延输入到1级模糊逻辑系统,结合规则自适应匹配,推理出QoS模糊值,并通过QoS模糊值对网络进行初步筛选得到候选网络集;然后通过触发机制触发2级模糊逻辑系统,并将候选网络的QoS模糊值、网络负载率、用户接入费用输入2级模糊逻辑系统,同时结合规则自适应匹配,得到输出判决值,从而选择最佳接入网络。最后,实验结果表明,该算法能保证网络性能的同时,降低系统的时间开销。     

基于用户偏好的异构网络选择算法研究

针对当前大多数网络选择算法没有充分考虑用户基于业务的网络偏好这一问题,提出了一种基于用户偏好的异构网络选择算法。该算法充分考虑业务需求、用户偏好及网络性能差异,通过层次分析法和距离分析法分别计算用户对各候选网络的主观和客观偏好权重,根据用户策略动态确定综合权重,并由此结合各属性权重计算网络性能,选出最优网络。仿真结果表明该算法可以准确选择接入网络,并当用户在网络边缘做兵乓运动时有效减少切换次数。     

一种多属性决策的异构网络选择算法

针对异构网络融合环境下的网络选择不能仅依靠物理信号强度的特点,利用多属性决策理论提出了一种异构网络选择算法。该算法考虑业务要求、用户喜好以及网络差异,通过层次分析法和熵值法确定网络属性的权重,并由此计算可得网络性能,选出最优网络。仿真结果表明,此算法可以准确选择接入网络,并当用户在网络边缘做兵乓运动时有效减小切换次数,降低丢包率。     

车辆异构网络中预测垂直切换算法

在车辆异构网络中,针对垂直切换决策时刻之后网络状态的动态变化,提高切换性能问题,提出一种基于马尔可夫过程的预测垂直切换(M-VHO)算法。算法考虑了切换决策后网络状态的动态变化对车辆终端服务质量(QoS)的影响。其基本思路是:在需要垂直切换时,利用马尔可夫过程的转移概率预测未来网络状态的变化;另外,采用模糊逻辑方法确定评价属性参数权重;最后,比较切换决策、切换执行和切换之后时刻的总收益来优化选择最佳切换网络。仿真结果证明,该算法在确保较高负载均衡的情况下,可有效改进车辆终端的平均阻塞率及丢包率,降低乒乓效应,确保了车辆终端的QoS。     

无线异构网络的垂直切换算法研究

以通用移动通信系统(UMTS)与无线局域网(WLAN)融合为例,研究无线异构网络的垂直切换算法。由于垂直切换算法应考虑因素的复杂性以及不同网络性能的各异性,有必要对现有算法作出归纳总结比较,并据此提出新的垂直切换算法。该算法以代价函数为基础,将稳定周期与切换目标网络和当前服务网络的效用函数联系起来,实现移动节点自适应的切换判决。提出的算法能有效减少不必要的切换,增强异构网络的适应性。     

Multi-Dimensional Adaptive SINR Based Vertical Handoff for Heterogeneous Wireless Networks

Vertical handoff in next generation heterogeneous wireless networks is a multi-dimensional issue. In this article we propose a multi-dimensional adaptive SINR based vertical handoff algorithm (MASVH) which uses the combined effects of SINR, user required bandwidth, user traffic cost and utilization from participating access networks to make handoff decisions for multi-attribute QoS consideration. Simulation results confirm that the new MASVH algorithm improves the system performance in terms of higher throughput and lower dropping probability, as well as reduces the user traffic cost for accessing the integrated wireless networks.     

Vertical handoff decision in 4G wireless networks using multi attribute decision making approach

Multi-interface terminal in heterogeneous wireless networks will have network access from diverse access technologies. Multiple attribute for decision making including user preference will increase the complexity of handoff process. Various approaches have been proposed to solve the complexity problem of handoff decision. In this paper, multi attribute decision making algorithms Analytic Hierarchy Process (AHP) method, Simple Additive Weighting (SAW), Total Order Preference by Similarity to the Ideal Solution (TOPSIS), and Grey Relational Analysis (GRA) methods have been proposed for handoff decision in a WiMAX–WLAN environment to facilitate user with better quality of service. AHP has been used for calculation of weights of decision parameters. Numerical results show that SAW, TOPSIS and GRA provide almost similar performance. SAW is very simple to implement but probability of error is less in GRA because values of decision attribute are directly used for ranking of alternatives. TOPSIS is sensitive to the attribute with high score.     

Research on vertical handoff decision based on service history information and SINR for heterogeneous wireless networks

In this letter, we propose a SH (Service History) and SINR (Signal to Interference plus Noise Ratio) based PROMETHEE (SHS-PROMETHEE) vertical handoff (VHO) decision algorithm. An attribute matrix is constructed considering the SH information and the SINR in the source network and the equivalent SINR in the target network and so on. Handoff decision meeting multi-attribute QoS requirement is made according to the traffic features. The weight relation of decision elements is determined with LS method. Finally decision is made using PROMETHEE algorithm based on the attribute matrix and weight vector. The simulation results have shown that the SHS-PROMETHEE algorithm can reduce unnecessary handoffs and provide satisfactory vertical handoff performance.     

无线异构网络中带有动态权值的新型垂直切换算法

In order to enhance the quality of vertical handoff in an overlay wireless network, multiple attributes are taken into account when optimizing the vertical handoff decision including user-based and network-based QoS factors. In this paper, we develop a novel vertical handoff algorithm in an integrated 3G cellular and Wireless LAN networks. The proposed algorithm can adjust the weight of each QoS attribute dynamically as the networks change, trace the network condition and choose the optimal access point at transient regions. Simulation results show that this algorithm is able to provide accurate handoff decision, resulting in small unnecessary handoff numbers, good performance of throughput and handoff delay in heterogeneous environments.     

A genetic algorithm approach for multi-attribute vertical handover decision making in wireless networks

Mobile terminals can typically connect to multiple wireless networks which offer varying levels of suitability for different classes of service. Due to the changing dynamics of network attributes and mobile users’ traffic needs, vertical handovers across heterogeneous networks become highly desirable. Multiple attribute decision making (MADM) techniques offer an efficient approach for ranking competing networks and selecting the best one according to specific quality of service parameters. In this paper, a genetic algorithm (GA) is applied to optimize network attributes’ weighting by emphasizing ranking differences among candidate networks, thereby aiding correct decision making by reducing unnecessary handovers and ranking abnormalities. The performance of the proposed GA-based vertical handover is investigated with typical MADM techniques including Simple Additive Weighting (SAW) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The results show that the proposed GA-based weight determination approach reduces the abnormality observed in the conventional SAW and TOPSIS techniques substantially. The results of this paper will help ensuring the application of MADM methods to more dynamic and challenging decision making problems encountered in wireless network.     

基于模糊逻辑的多终端协同的垂直切换决策算法

针对异构网下多终端协同的垂直切换决策问题,提出一种基于模糊逻辑和层次分析法的垂直切换决策算法,它分为2部分:切换时机的判断和虚拟终端的构建.首先采用模糊逻辑判断切换的时机,然后采用层次分析算法与简单加权求和结合的方法选择虚拟终端的最优构成方式.仿真结果表明,算法能够降低切换次数和不必要切换率,并且能够充分体现应用需求和用户偏好.     

A new handoff management system for heterogeneous wireless access networks

In heterogeneous wireless access networks, each mobile terminal may frequently need to change its base station (BS); this change is called a ‘handoff’. BSs have static parameters, which are related to their radio access technologies (RATs); however, they also contain dynamic parameters such as load and signal quality. Therefore, the problem of handoff decision includes two subproblems of RAT selection and BS selection. In this paper, first a ‘heterogeneous handoff management system’ for gathering all different required parameters is proposed. Second, a RAT Selection algorithm based on analytic hierarchy process and a BS Selection algorithm based on data envelopment analysis are designed. Finally, by means of ‘weight restriction’ technique, we develop a method for studying the impact of RAT Selection parameters on the performance of the network. Simulation results indicate that RAT Selection parameters have significant impact on the bandwidth utilization, energy consumption and the whole satisfaction of the users in heterogeneous wireless access networks.Copyright © 2012 John Wiley & Sons, Ltd.     

A constrained MDP-based vertical handoff decision algorithm for 4G heterogeneous wireless networks

The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This paper focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user’s velocity and location information are also considered when making handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user’s velocity, user’s budget, traffic type, signaling cost, and monetary access cost.     

基于认知自选择决策树的垂直切换方法研究

在异构无线网络环境下高速移动的终端用户需要随时随地接入网络,然而,在垂直切换过程中,由于终端用户对网络选择的偏好不同以及切换之后网络连接时间和状态难以得到保障,无法满足用户的切换需求。因此,提出了一种支持终端用户高速移动的基于认知自选择决策树的垂直切换方法。该方法首先根据网络属性和终端运动趋势建立相应的切换概率分布,然后根据用户偏好选择相应的决策树进行决策,最后通过对切换后终端的业务类型和运动状态进行反馈分析,提出了反馈认知决策方法。仿真结果表明,所提的方法不仅能够保证高速移动终端在异构无线网络下的切换质量,而且减少了不必要的切换,保证了网络的及时更新。     

Air interface switching and performance analysis for fast vertical handoff in cellular network and WLAN interworking

The integration of wireless local area network (WLAN) hotspot and the 3G cellular networks is imminently the future mode of public access networks. One of the key elements for the successful integration is vertical handoff between the two heterogeneous networks. Service disruption may occur during the vertical handoff because of the IP layer handoff activities, such as registration, binding update, routing table update, etc. In this paper, the network interface switching and registration process are proposed for the integrated WLAN/cellular network. Two types of fast vertical handoff protocols based on bicasting and non‐bicasting supporting real‐time traffic, such as voice over IP, are modeled. The performance of a bicasting based handoff scheme is analyzed and compared with that of fast handoff without bicasting. Numerical results and the simulation are given to show that packet loss rate can be reduced by the bicasting during handoff scheme without increasing bandwidth on both wireless interfaces. Copyright © 2006 John Wiley & Sons, Ltd.