Immune optimization algorithm for solving joint call admission control problem in next-generation wireless network

The integration of radio access networks with different radio access technologies (RATs) is one of the remarkable characteristics of the next-generation wireless networks (NGWNs). In NGWN, the users with multi-network interface terminals should be able to select independently radio access network to obtain the best service. Therefore, joint call admission control (JCAC) schemes are required to select the most appropriate radio access network (RAN) for incoming calls. We propose an immune algorithm-based JCAC (IA-JCAC) scheme with users centric in order to enhance user's satisfaction. However, JCAC algorithms with users centric can lead to highly unbalanced traffic load among the available RANs in NGWN because users act independently, and most of them may prefer to be connected through a particular RAN. Highly unbalanced traffic load in NGWN will result in high overall call blocking/dropping probability and poor radio result utilization. To solve this problem, we employ dynamic pricing for balancing traffic load among available RANs in heterogeneous wireless networks where users' preferences are considered in decision-making on RAT selection. The proposed IA-based JCAC scheme is compared with another scheme that does not use the dynamic pricing on the performance. The simulation result shows the effectiveness of the proposed IA-JCAC scheme is improved significantly.     

Integer linear programming optimization of joint RRM policies for heterogeneous wireless systems

Wireless systems will be characterized by the coexistence of heterogeneous Radio Access Technologies (RATs) with different, but also complementary, performance and technical characteristics. These heterogeneous wireless networks will provide network operators the possibility to efficiently and coordinately use the heterogeneous radio resources, for which novel Joint Radio Resource Management (JRRM) policies need to be designed. In this context, this work proposes and evaluates a JRRM policy that simultaneously determines for each user an adequate combination of RAT and number of radio resources within such RAT to guarantee the user/service QoS requirements, and efficiently distribute the radio resources considering a user fairness approach aimed at maximizing the system capacity. To this aim, the JRRM algorithm, which takes into account the discrete nature of radio resources, is based on integer linear programming optimization mechanisms.     

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.     

Cross-layer radio resource management in integrated WWAN and WLAN networks

This paper proposes a mobility adaptive network selection scheme in the context of wireless wide area network (WWAN) and wireless local area network (WLAN) radio access technologies (RATs) that supports both real-time (RT) and non-real-time (NRT) service classes. Physical layer information based call admission control (CAC) is considered for the two RATs to enforce service specific QoS requirements. The effectiveness of the cross-protocol-layer information for radio resource management (RRM) in integrated WWAN and WLAN networks is assessed analytically for individual service classes in a multi-service environment using the theory of Markov chains. The impact of non-uniform user and mobility distributions due to the existence of hotspot in the macro-cell area and the effect of network selection parameter measurement errors on the RRM performance are also evaluated. Numerical results show that the proposed network selection scheme minimizes the rate of unnecessary vertical handoffs, thereby providing stable communication without degrading the call blocking probability and call outage probability performance metrics.     

Dynamic RAT selection for multiple calls in heterogeneous wireless networks using group decision-making technique

Existing radio access technology (RAT)-selection algorithms for heterogeneous wireless networks (HWNs) do not consider the problem of RAT selection for a group of calls from a multimode terminal (MT). Multimode terminals (MTs) for next generation wireless networks have the capability to support two or more classes of calls simultaneously. When a new call is initiated on an MT already having an ongoing call in an HWN, the current RAT may no longer be suitable for the two calls (incoming call and the existing call). Thus, a new RAT may be more suitable for the two calls. The problem of RAT selection for two or more calls from an MT in an HWN is a group decision problem. This paper addresses the problem of RAT selection for a group of calls from an MT in an HWN by using the modified TOPSIS group decision-making technique. The paper proposes a dynamic RAT-selection algorithm that selects the most suitable RAT for a single call or group of calls from an MT in an HWN. The algorithm considers users’ preferences for individual RATs, which vary with each class of calls, in making RAT selection decisions in an HWN. A user’s preference for each of the available RATs is specified by weights assigned by the user to RAT selection criteria for different classes of calls. Based on the assigned weights, the proposed algorithm aggregates individual calls’ weights specified by the user to make a RAT-selection decision for a group of calls. In order to reduce the frequency of vertical handover, the proposed algorithm uses RAT preference margin in making RAT selection decisions. RAT preference margin is a measure of the degree to which the newly preferred RAT is better than the current RAT. Performance of the proposed algorithm is evaluated through numerical simulations. Results are given to show the effectiveness of the proposed RAT-selection algorithm.     

面向用户的异构网接入选择算法

无线通信网络的发展趋势之一是将各种不同无线接入技术进行融合。多接入选择作为无线资源管理中的关键技术是目前异构网融合的研究热点之一。从用户的利益出发,充分考虑预接入网络的费用、QoS和稳定性;假定不同的网络运营商之间是彼此竞争的,即没有达成统一的协议,提出了一种结合目标代价函数与层次分析法的动态多接入选择算法。通过对影响因素进行分析和二次判断,建立了网络选择决策模型,仿真结果验证了该算法的正确性与有效性。     

Network Selection Decisions for Multiple Calls Based on Consensus Level

Next generation multimode terminals have the capability to support different classes of calls simultaneously as well as the ability to connect to two or more radio access technologies (RATs), at the same time, in a heterogeneous wireless network. For a mobile terminal having multiple classes of simultaneous handoff calls (such as file download and video sessions), RAT selection decisions can be made independently for individual calls in the group or jointly for the entire group of calls. Both independent and group RAT selection decisions for multiple calls have advantages and disadvantages. Existing RAT selection algorithms have focused on RAT selection decisions for single calls. Therefore, this paper investigates independent call and group call RAT selection decisions for multiple calls in heterogeneous wireless networks, and proposes a scheme that makes RAT selection decisions for multiple calls based on a consensus level among the multiple calls to be admitted. When this consensus level is among multiple calls to be admitted into a particular RAT and is equal to or above a certain threshold value, a group decision is used. Otherwise, independent decisions are made. The performance of the proposed RAT selection scheme is evaluated in a three service three RAT heterogeneous network, supporting multihomed terminals. Simulation results are given to show the effectiveness of the proposed scheme.     

Modeling and analysis of nano-sized GMRs based on Co,NiFe and Ni materials

Magnetic simulation method is introduced to analyze giant magnetoresistances(GMRs)in nanoscale for nano-sized biosensors.A spin valve model with special gridding corresponding to the exchange interaction length is proposed to study the influence of easy axes,exchange coefcients,pinning fields and feature widths on magnetization reversals and hysteresis characteristics of nano-sized GMRs with diferent pinned layer and free layer materials of Co,NiFe and Ni.The switching field is found to be almost linear with the pinning field and decrease with the absolute exchange coefcients and the feature widths for the nano-sized GMRs.The increase rate of each depends on the spin valve stacks.Further investigations into variations of the magnetization distribution reveal that the initial magnetization distribution and the magnetization reversal mode depend greatly on easy axes and materials The dependence on easy axes based mainly on the magnetocrystalline anisotropy is illustrated in detail.     

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.     

无线多媒体网络中一种基于测量网络状态的动态呼叫接纳控制算法

提出了一种无线多媒体网络中基于测量网络状态的动态呼叫接纳控制算法.它区分了实时和非实时业务,在网络带宽资源不足时可通过降低非实时业务带宽确保实时业务呼叫连接的可靠性;还可根据当前网络状况调整预留带宽大小,使小区实时业务切换呼叫掉线率低于设定的门限值.大量仿真结果显示该算法具有低实时业务切换呼叫掉线率和与固定预留方案相当的带宽利用率,而只以略高的新呼叫阻塞率为代价,适合各种不同概率发生时实际应用的情况.     

A hybrid intelligent model for network selection in the industrial Internet of Things

Industrial Internet of Things (IIoT) plays an important role in increasing productivity and efficiency in heterogeneous wireless networks. However, different domains such as industrial wireless scenarios, small cell domains and vehicular ad hoc networks (VANET) require an efficient machine learning/intelligent algorithm to process the vertical handover decision that can maintain mobile terminals (MTs) in the preferable networks for a sufficient duration of time. The preferred quality of service parameters can be differentiated from all the other MTs. Hence, in this paper, the problem with the vertical handoff (VHO) decision is articulated as the process of the Markov decision aimed to maximize the anticipated total rewards as well as to minimize the handoffs’ average count. A rewards function is designed to evaluate the QoS at the point of when the connections take place, as that is where the policy decision for a stationary deterministic handoff can be established. The proposed hybrid model merges the biogeography-based optimization (BBO) with the Markov decision process (MDP). The MDP is utilized to establish the radio access technology (RAT) selection’s probability that behaves as an input to the BBO process. Therefore, the BBO determines the best RAT using the described multi-point algorithm in the heterogeneous network. The numerical findings display the superiority of this paper’s proposed schemes in comparison with other available algorithms. The findings shown that the MDP-BBO algorithm is able to outperform other algorithms in terms of number of handoffs, bandwidth availability, and decision delays. Our algorithm displayed better expected total rewards as well as a reduced average account of handoffs compared to current approaches. Simulation results obtained from Monte-Carlo experiments prove validity of the proposed model.     

On signaling performance bounds of location management in Next Generation Wireless Networks

Next Generation Wireless Networks (NGWN) are proposed to achieve the goal of ubiquitous broadband networking by utilizing multiple wireless access subnetworks serving overlapping areas. Location management schemes play a very important role in NGWN since mobile users roam in coverage areas of these subnetworks simultaneously. The performance of location management schemes directly affect the overall performance of NGWN at large. In this paper, signaling performance bounds achievable by a location management scheme in the wireless portion of NGWN are presented. Assuming complete knowledge about user mobility, call arrival patterns, detailed maps of subnetworks coverage areas, and other NGWN parameters, equations for signaling performance achievable by an idealized location management scheme over the wireless interface has been derived. The performance bounds presented in this paper serve as an upper bound for the performance of any other location management scheme designed for NGWN. These bounds are intended to serve as a benchmark to determine how well a proposed location management scheme operates in NGWN and will help to determine how much room for improvement exists.     

Bandwidth aggregation in heterogeneous wireless networks: A survey of current approaches and issues

Future wireless networks are envisaged to consist of a variety of integrated and jointly managed radio access technologies (RATs). This is motivated by the complementary features of the individual RATs. When in the overlapping coverage of the integrated RATs, a multimode terminal can use them simultaneously, thus aggregating bandwidth to enhance performance of high-bandwidth applications. However, there are challenges that must be addressed to achieve efficient bandwidth aggregation. Packet reordering is the most dominant challenge. Packet reordering can lead to excessive delays that can affect real-time applications; it can also affect throughput of TCP applications adversely. To circumvent the reordering problem and other challenges associated with simultaneous use of the terminal's multiple interfaces, bandwidth aggregation solutions are developed. This paper reviews existing bandwidth aggregation solutions in heterogeneous wireless networks. Challenges and several open research issues in the design of bandwidth aggregation approaches are also outlined. To the best of our knowledge, this is the first comprehensive review of existing bandwidth aggregation techniques in heterogeneous wireless networks. This paper, therefore, provides important lessons and information from current bandwidth aggregation solutions, which can be used to guide the development of more efficient bandwidth aggregation approaches.     

多节点共享保障时隙分配策略

在现代工业无线网络中,IEEE 802.15.4标准以其独特的低功耗、低成本特点被广泛应用。IEEE 802.15.4可以提供最低0.006%的占空比,最大限度降低功耗,同时提供的保障时隙GTS机制为节点提供了实时服务保障。然而,在为大规模节点提供保障时,IEEE 802.15.4提供的GTS机制缺乏灵活性,只能为有限节点提供实时保障服务。本文针对这一问题提出一种多节点共享保障时隙分配策略,允许多个数据流在满足延迟需求前提下,共享同一个GTS减少带宽浪费。分析表明,多节点共享的保障时隙分配策略与普通分配方法相比,可有效提高带宽利用率。     

Optimal delay estimation using complete bipartite graph method for VoIP over WLAN environments

Voice over wireless LAN (WLAN) is widely applied in modern Internet networks. In real-time wireless environments, the primary cause of an impaired speech quality is transmission delays. In wireless communications, the parameters employed for quality of service (QoS) estimations include the delay, the throughput, the blocking rate and the link cost. These parameters are significantly dependent on the type of topology pattern adopted. This study focuses primarily on the delay guarantee and optimal delay aspects of wireless communications. A tradeoff exists between the link number and the delay guarantee. A greater number of links is beneficial in reducing transmission delays, but leads to an increased cost. Conversely, a lower number of links reduces the system cost, but increases the delay. This study employs graph theory to determine the node topology pattern which minimizes the delay for voice over IP (VoIP) transmission in WLAN environments. The topology is optimized both for a variable link delay and a constant link delay. The optimization method presented in this study can be widely applied to the link topology design for multiparty conferencing in modern wireless networks.     

Quality of Service Support for Multimedia Applications in Third Generation Mobile Networks Using Adaptive Scheduling

Third generation mobile network will support services such as video-telephony, video-conferencing and other multimedia applications. Therefore, this network must provide quality of service (QoS) to these applications consistent with that offered by fixed networks. However, this is a very challenging task due to the instability of the wireless channel and the diverse quality of service requirements dictated by different multimedia applications. In this paper we introduce a resource allocation algorithm for the wireless downlink that takes into account the wireless channel characteristics, the QoS required by the applications as well as a pricing value function. Our solution is based on an adaptive scheduling algorithm originally developed for scheduling real-time processes during transient surges. This algorithm tends to maximize the wireless network operator profit while satisfying the customers' quality requests.     

异构分层无线网络中基于业务QoS保证的切换策略研究

针对异构分层无线网络提出了一种保证业务QoS的切换策略。该策略在层间呼叫双向溢出基础上,为实时业务切换设置了保护信道,为非实时业务切换设置了缓冲队列。为了进一步降低实时业务切换的掉线率,还使用了信道侵占技术,原理是实时业务切换呼叫可以侵占数据业务正在使用的信道资源。仿真结果表明,提出的切换方法能够显著降低各类切换业务的掉线率,同时整个异构分层系统的信道利用率也略有提高。     

A scheduling discipline and admission control policy for xunet 2

Xunet 2 is a collaborative research program with a goal of understanding the fundamental issues in the performance of ATM networks. These networks are expected to carry a mixture of constant bit-rate traffic, variable bit-rate traffic and computer traffic spanning a wide range of performance requirements. This paper describes these service requirements and matches them with performance guarantees that can be provided by the scheduling discipline supported by an experimental ATM switch. The scheduler supports per-virtual-circuit queueing and several priorities of round robin service in order to segregate real-time and non-real-time traffic and provide fair sharing for bursty computer traffic. Detailed simulations show that real-time traffic can be efficiently integrated with non-real-time traffic using appropriate call admission policies and enhancements to traditional round robin scheduling. While the present study focuses on providing quality of service guarantees in the Xunet 2 network, the design of the scheduler and the call admission policies are relevant to ATM networks in general. On leave of: Indian Institute of Technology, Delhi, India     

Scheduling on-demand data broadcast in mixed-type request environments

In many on-demand broadcast environments, there can be a mix of requests, in which some of the requests have real-time constraints, while other requests have no time constraints associated with them. We refer to such environments as mixed-type environments. Existing strategies for on-demand data in broadcast systems typically only consider how to minimize the wait time of the requests, while scheduling strategies for real-time requests typically only consider how to minimize the number of deadlines missed. How to satisfy both of these constraints is a challenging problem whose solution can benefit many applications. In this paper, we present an on-demand broadcast cost model that is more general than existing broadcast cost models because it considers both response time and number of deadlines missed. An analysis of the system is presented as a Markov decision process to ascertain the feasibility of an optimal policy. We propose two scheduling strategies for mixed-type broadcast systems that are based on our cost model: maximum paid cost first and maximum value gained first. The simulation results show that both of our strategies always achieve the best result, when compared to existing broadcast strategies, for varying request arrival rates, real-time to non-real-time request ratios, missed deadline weight values, wait-time bounds on the non-real-time requests, and varying broadcast rates.     

Design and evaluation of flow handoff signalling for multihomed mobile nodes in wireless overlay networks

With the increasing deployment of wireless overlay networks, a mobile node with a range of network interfaces can be connected to multiple heterogeneous or homogeneous access networks simultaneously. Such host multihoming technology can be exploited to distribute (or hand off) application flows among the most appropriate interfaces and access networks dynamically to achieve end-to-end seamless, robust and even quality-of-service-aware communications for mobile users. It is essential that an efficient and effective flow handoff signalling scheme be in place. Nevertheless, little prior work has addressed this problem sufficiently in a systematic way and little performance evaluation is readily available. We propose a set of signalling procedures for a comprehensive, flexible yet standard-oriented flow handoff solution. Two candidate schemes are designed by extending and optimising related IETF work based on Mobile IPv6 or Network Mobility (NEMO). Theoretical analyses are performed and numerical results are then presented with a focus on signalling loads to compare the two proposals and to demonstrate that the designs can largely meet the requirements on desired signalling performance. Preliminary implementations and experimental results are also reported to validate the concepts of the designs, investigate the flow handoff signalling delays and verify the effectiveness of the policy-based flow handoff support for typical real-time and non-real-time applications.