Utility-based RAT selection optimization in heterogeneous wireless networks

Recent technological advances in wireless networks will enable the realization of an integrated heterogeneous wireless environment consisting of multiple Radio Access Technologies (RATs) within a network provider. One of the most important benefits is that this will allow providers to balance their traffic among their subsystems without compromising on QoS issues. In this paper we focus on the Network Selection problem to allocate terminals to the most appropriate RATs by jointly examining both users’ and providers’ preferences. We introduce three utility-based optimization functions based on the type of application that users request. We then formulate the terminal assignment problem as an optimization problem, which is recognized as NP-hard. We examine both offline and online selection and develop an optimal Branch and Bound (BB) algorithm, a Greedy heuristic, as well as three Strip Packing variations. BB behaves efficiently in both offline and online environments reducing the search procedure, while the proposed heuristics produce results close to the values we get from BB but with very low computational cost.     

异构网络中的网络选择问题

在异构网络中,网络选择的结果应是由主观因素和客观因素,即用户喜好和网络客观属性,两者综合得出的。而在有限方案多目标决策的综合评价方法中,层次分析法具有主观性强的特点,理想值近似排序法的特点则真实、直观、可靠。针对这两种方法的各自特点,在网络选择中,对用户喜好方面采用层次分析法,对网络客观状况采用理想值近似排序法,并提出了一种用户喜好与网络状况协同决策的网络选择算法。仿真结果表明,在不考虑负载的情况下,提出的算法能有效地选择出适合于移动终端当前业务的网络。     

Dynamic spectrum access and network selection in heterogeneous cognitive wireless networks

In this paper, we propose a cross-layer architectural framework for network and channel selection in a heterogeneous cognitive wireless network (HCWN). Existing research on heterogeneous wireless networks primarily focuses on network selection among available networks, while research on cognitive networks mainly focus on improvising efficient sensing and spectrum sharing algorithms. In this paper, we introduce a novel probabilistic model for channel classification based on its adjacent channels’ occupancy within the spectrum of an operating network. Further, we utilize a Analytic Hierarchical Process for categorizing user applications, followed by prioritizing them based on performance metrics. Finally, a modified Hungarian algorithm is implemented for channel and network selection among secondary users. The effectiveness of our approach is evaluated for different scenarios of HCWN. Simulation results show that our approach provides a 60% and 64% improvement in blocking probability over greedy and first-come-first-serve (FCFS) algorithms, respectively. Additionally, our proposed algorithm results in 22% enhancement in spectrum utilization and 50% increase in throughput over greedy and FCFS schemes.     

Access point selection in heterogeneous wireless networks using belief propagation

The next generation wireless network will be composed by various heterogenous wireless access networks,such as cellular network,worldwide interoperability for microwave access(WiMAX),wireless local area network(WLAN),etc.Different access networks cooperatively provide high-bandwidth connectivity with bandwidth guarantees.This paper proposes a utility-based access point selection scheme,which selects an accessible point for each user,such that the bandwidth requirement of each user is satisfied,and also the defined utility function is maximized.Due to the NP-complete nature of the problem,the existing proposals apply the greedy method to find a solution.We find that belief propagation is an efficient tool to solve this problem,and thus,we derive the same optimization objective in a new way,and then draw a factor graph representation which describes our combinatorial optimization problem.Afterwards,we develop the belief propagation algorithm,and show that our algorithm converges.Finally,we conduct numerical experiments to evaluate the convergency and accuracy of the belief propagation in load balancing problem.     

Connectivity opportunity selection in heterogeneous wireless multi-hop networks

This paper addresses the problem of selecting the best connectivity alternative for the user in a generic Heterogeneous Wireless Multi-hop Network (HWMN), integrating distinct wireless technologies and multi-mode cooperating stations. We propose a Connectivity opportunity Selection Algorithm (CSA) that uses network state information and mobility profile information to select the best connectivity based on the applications’ requirements. We provide a simulation-based performance evaluation of the CSA and compare it with a greedy network selection scheme. Furthermore, we propose an extended reference model that allows the integration of the concept of connectivity opportunity and our proposed CSA with the framework being defined by the upcoming IEEE 802.21 standard for Media Independent Handover services.     

A MIH-based approach for best network selection in heterogeneous wireless networks

In the next generation wireless networks, different technologies belonging to one or more operators should be integrated to form a heterogeneous environment based on an IP core network infrastructure. This ensures user mobility and service continuity by maintaining connections when switching between various technologies and it introduces new resources and possibilities for applications. In this context, an automatic interface selection based on instantaneous and practical constraints and user preferences (Quality of Service (QoS) parameters, available resources, security, power consumption, etc.) is therefore required. The different network selection and handover schemes proposed in the literature can be classified into three approaches according to who is responsible for making the handover decision: the terminal, the network or by a cooperation between both of them. However, these approaches keep presenting some drawbacks; namely the problem of resources management and network load balancing whenever the selection is controlled by the mobile terminal (MT) and the problem of scalability and unknown operator's management policy whenever the selection is rather controlled by the network.In this article, first we propose a MIH based approach for handover initiation and preparation for heterogeneous wireless network. The proposed framework is based on the principals of IEEE 802.21 for context information gathering and optimized handover decision making. Second, we propose a new architecture and new network selection scheme that explicitly take into account the current resource usage and the user preferences. Furthermore, our solution ensures the selection of the most suitable network for each flow while taking into consideration its expectations in terms of QoS. A feasibility study of implementing a new architecture on a single MT is evaluated by using typical scenarios and using various algorithms. Thanks to the introduced function entities and modules in the proposed architecture, network utilization balancing and user and application expectations, which are successfully assured without operator intervention. Performance analysis shows that the proposed algorithm best meets the common quality requirements.     

多无线传感器网络互联技术研究

针对现有基于P2P的无线传感器网络互联技术存在的不足,提出了一种基于P2P的三层无线传感器网络互联技术。该技术采用P2P技术实现多无线传感器网络互联系统所需的伸缩性、鲁棒性、容错能力和自组织性;通过在系统中引入超级端,提高了传感数据的复用率,降低了通信复杂度,减少进出传感器网络的消息量,使得无线传感器网络的生命周期得以延长。     

Investigation on MDP-based radio access technology selection in heterogeneous wireless networks

The new generation of wireless networks is characterized by heterogeneity i.e. the coexistence of two or more radio access technologies (RAT) in the same geographical area. While this coexistence of RATs offers various advantages, it also imposes many challenges for the network operator, whose aim is to maximize the generated revenue while satisfying the customers’ increasing demands. One important mechanism in heterogeneous wireless networks (HWN) is the RAT selection. It is normally triggered when a new call arrives, and provides the decision on whether the call can be admitted or not, and by which RAT it has to be served. Different approaches can be used to tackle the problem of RAT selection in HWNs. In this paper, we study Markov Decision Process (MDP)-based RAT selection in a cellular/WLAN heterogeneous network where the maximization of the revenue is considered as objective. An optimal RAT selection policy is therefore derived. The performance of the optimal scheme is evaluated in comparison with two other policies, namely Cellular-First policy and Load Balancing policy.     

一种面向业务类别的区分权值异质无线网络选择算法

在以满足业务服务质量（QoS）需求为目标的异质无线网络选择问题中,针对不同类别的业务在QoS需求上的差异,利用层次分析法对3GPP定义的四类业务进行了QoS参数相对重要性分析,设定了每类业务的QoS参数权值,然后基于理想值近似性排序算法,提出了一种面向业务类别的区分权值异质网络选择算法。仿真结果表明,区分权值算法相比平均权值算法而言,前者在满足业务QoS需求的同时,能够更合理地选择目标网络,有效地平衡候选网络负载。     

使用部署知识的异构传感器网络有效成簇算法

成簇算法是传感器网络中减少能量消耗的一种关键技术,它能够增强网络的扩展性和延长网络的生存时间。异构传感网络在能量节约方面的性能更好。提出一种适应异构无线传感器网络的分布式能量有效的成簇方案DEECUDK。该方案首先利用部署知识部署节点,使能量在整个监测区域分布比较均匀,然后以节点的剩余能量与传感半径之内的节点的剩余覆盖能量为主参数,其相邻节点个数为辅参数来选举簇头节点。较高初始能量、剩余能量和相邻节点数多的节点比其他节点拥有更多的机会成为簇头节点,并引入活动节点判别式,不需要增加任何开销来减少簇内冗余数据量,从而使网络能量均匀消耗,延长网络的生存时间。通过模拟实验结果,与现有的异构传感网络成簇算法相比,新的算法在网络生存时间与网络吞吐量方面有着更好的性能。     

A utility-based fuzzy TOPSIS method for energy efficient network selection in heterogeneous wireless networks

Mobile terminals in 4G heterogeneous wireless networks continuously undergo horizontal and vertical handovers. In order for a mobile terminal to be connected to a network in the best possible way in terms of QoS performance and energy consumption, access network selection as the main decision within the handover process is obviously crucial. This paper presents a novel method that takes into account user preferences, network conditions, QoS and energy consumption requirements in order to select the optimal network which achieves the best balance between performance and energy consumption. The proposed network selection method incorporates the use of parameterized utility functions in order to model diverse QoS elasticities of different applications, and adopts different energy consumption metrics for real-time and non-real-time applications. User preferences are easily configured for different application and situation contexts through the use of linguistic assessments and their representation as triangular fuzzy numbers. The aggregation of multiple criteria for the calculation of the overall rating of the networks is performed through the use of the Fuzzy Set Representation TOPSIS method that resolves the issue of inconsistency related to conflicting decision criteria and is modified through the use of the employed utility functions for the elimination of the ranking abnormality problem. Finally, simulations are conducted in order to demonstrate how the proposed method would work and confirm its suitability and effectiveness.     

Green framework for future heterogeneous wireless networks

Energy-efficient communication has sparked tremendous interest in recent years as one of the main design goals of future wireless Heterogeneous Networks (HetNets). This has resulted in paradigm shift of current operation from data oriented to energy-efficient oriented networks. In this paper, we propose a framework for green communications in wireless HetNets. This framework is cognitive in holistic sense and aims at improving energy efficiency of the whole system, not just one isolated part of the network. In particular, we propose a cyclic approach, named as energy-cognitive cycle, which extends the classic cognitive cycle and enables dynamic selection of different available strategies for reducing the energy consumption in the network while satisfying the quality of service constraints.     

Social-connectivity-aware vertical handover for heterogeneous wireless networks

Vertical handover mechanism for a WLAN-cellular heterogeneous network could be made efficient with the use of context aware admission control strategy. Existing admission control methods aim to provide satisfactory quality of service, but rely solely on the availability of wireless resources in the target network. We propose that the admission control in WLAN should make use of social connectivity context of users in its coverage area to classify local and global traffic. In this paper, we introduce a novel Social-Connectivity-aware Vertical Handover (SCVH) scheme, which performs admission control using connectivity graph data from the online social networking services. A higher importance of visiting node for users resident in WLAN, advocates a higher priority for granting admission. We employ graph-theoretic concept of centrality to calculate the social importance of potential handing-over nodes. By giving handover precedence to higher-centrality nodes, we achieve an optimal allocation of wireless resources in addition to improved quality of service. The proposed handover strategy offers an additional advantage of reducing global social network traffic.     

Price war in heterogeneous wireless networks

Wireless users have the opportunity to choose between heterogeneous access modes, such as 3G, WiFi or WiMAX for instance, which operate with different distance ranges. Due to the increasing commercial interest in access networks, those technologies are often managed by competing providers. The goal of this paper is to study the price war occurring in the case of two providers, with one provider operating in a sub-area of the other. A typical example is that of a WiFi operator against a WiMAX one, WiFi being operated in the smaller area. Using a simple model, we discuss how, for fixed prices, (elastic) demand is split among providers, and then characterize the Nash equilibria for the price war. We derive the conditions on provider capacities and coverage areas under which providers share demand on the common area. A striking additional result is that among the Nash equilibria, the one for which providers set the largest price corresponds to the case when the competitive environment does not bring any loss in terms of social welfare with respect to the socially optimal situation: at equilibrium, the overall utility of the system is maximized. The price of stability is one.     

Autonomous and adaptive resource allocation among multiple nodes and multiple applications in heterogeneous wireless networks

In the forthcoming future, various means of wireless communication, such as cellular, Wi-Fi, WiMAX, and DSRC, will be available to mobile users and applications. With the development of wireless communication and mobile devices, more and more users and applications will be accommodated in mobile environment. Since mobile users and applications compete for the limited wireless resources whose communication quality dynamically change, we need an adaptive mechanism for mobile users and applications to share the available network resources while satisfying each application?s QoS requirements. In this paper, we propose an adaptive resource allocation mechanism where each node autonomously determines wireless network resources to assign to each of networked applications running on it. For this purpose, we adopt an attractor composition model, which is based on an autonomous and adaptive behavior of biological systems. Through numerical analysis, we confirmed that our mechanism could adaptively and stably allocate wireless network resources to applications, while considering their QoS requirements and fairly sharing network resources with other nodes. It also is shown that our mechanism superiors to a mechanism where a node determines resource allocation by solving an optimization problem.     

A simulation model for localization of pervasive objects using heterogeneous wireless networks

Position represents a relevant attribute needed by many applications, whose contexts are characterized by pervasiveness of the objects/things in the considered scenarios. In order to infer positions of pervasive objects, which are neither equipped with any location-sensing technologies, nor are unable to locate themselves, it is needed to support them with an appropriate infrastructure, which allows to determine their position in a manner that is transparent to applications. In this work, we aim at extending the positioning service using an agent-based approach, in order to discover and localize different kinds of objects, exploiting cheap and embedded technologies. We describe the design and the implementation of a layered architecture, that supports the localization of devices, and simple pervasive and ubiquitous objects. A simulation tool has been develop to evaluate the proposed solution in different application scenarios of every-day life.     

合作伙伴选择的多准则群决策算法

针对合作伙伴选择问题,提出一种基于群体理想解的TOPSIS求解算法.求出对每个决策者而言各合作伙伴与其群体理想解的相对贴近度.基于备选合作伙伴集的群体理想解和负理想解,计算决策群体对各备选合作伙伴的最终排序.最后以一个供应商选择算例表明该方法的实用性.     

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.