多类型异构无线网络连通性研究

从渗流角度研究大规模单类型用户和多类型用户的自组织异构网络的连通性问题。首先,从布尔模型的角度出发,对于单类型用户,以圆盘模型分析簇分布时满足渗流的条件;对于多类型用户节点,根据泊松分布的认知无线电模型,从理论上给出具有多类型次用户节点的网络连通性的必要条件。其中,多类型次用户节点之间通信链路的存在与否不仅取决于它们之间的距离,也跟周围邻居用户节点的类型和收发行为有关。然后,从随机连接角度,引入乘积规则决定先连接哪两个用户,从而推迟或加速渗流发生。仿真有效地验证了渗流理论的实用性,可作为对认知无线电网络部署的指导。     

异构无线网络中基于覆盖概率的动态频谱分配算法

该文研究异构无线网络下行链路动态频谱分配(DSA)问题。首先考虑用户分布对下行链路干扰分析的影响及不同业务用户的信干比(SIR)要求,利用用户分布密度函数将小区内用户的SIR性能转化为小区基站的覆盖性能,在阴影衰落信道条件下,提出基于覆盖概率的干扰控制模型;基于该干扰控制模型,以网络效益最大化为目标,将DSA建模为非线性约束组合优化问题,进而结合贪婪思想设计了基于覆盖概率的DSA(CP-DSA)算法。仿真结果表明,CP-DSA算法能够提高网络效益,有效控制基站之间的干扰,满足用户的SIR要求。     

交互式异构无线网络垂直切换的中间件架构

异构无线网络研究的关键之一在于按照用户的应用要求,在不同网络之间实现垂直切换。文章面向多模移动终端提出交互式垂直切换中间件架构,描述了架构的功能组成体系,阐明了在多模移动终端上交互式简单快速地设置垂直切换所需参数或权重的界面。给出了按层次分析法AHP进行垂直切换的中间件实现流程的一个例子。     

认知异构网络中基于克隆选择算法的动态频谱分配

建立了认知异构无线网络的系统模型。基于该模型,以网络效益最大化为目标,考虑接入网的频谱需求,接入网之间的干扰和对应异构网络不同接入技术的多粒度重叠信道之间的干扰约束条件,将频谱资源分配建模为非线性约束0-1整数规划问题,进而提出基于克隆选择的认知异构网络中动态频谱分配算法,并在该算法中设计了一种新的能够同时考虑接入网频谱需求和多粒度信道频谱资源的抗体整数编码方式。仿真结果表明,所提算法相比于贪婪分配算法,增加了网络效益,提高了频谱使用效率。     

认知无线网络中的频谱切换技术

针对频谱切换的研究现状,文章介绍了频谱切换的场景、分类以及对认知无线网络物理层、媒体接入控制层（MAC）的需求,总结了频谱切换技术的最新研究进展,对目前的各种方案进行了比较分析,并提出了未来面临的挑战及研究方向。     

异构网络频谱共享在低频段重耕中的应用研究

LTE下载速率对大带宽的迫切需求、GSM网络退网的长尾效应以及传统的频谱静态分配方式,导致了900 MHz频谱资源的供需矛盾。本文研究了基于异构网络动态频谱共享的方案及在低频段重耕的应用及效果,实践表明方案在保证FDD LTE与GSM网络质量的情况下,利用频谱共享带来的错峰增益,提高了频谱利用率,并具备一定的可实施性。     

异构无线网络中基于人工神经网络的自适应垂直切换算法

针对当前基于人工神经网络的垂直切换算法(ANN-VHO),存在业务自适应性差和计算复杂度高的问题,该文提出一种基于人工神经网络的自适应垂直切换算法。首先,根据终端获取到的接收信号强度(RSS),采用阈值判断的方法,遴选出候选网络集;其次,根据该文划分的不同业务类型,对参数进行自适应选择和归一化;再次,把选择的参数输入人工神经网络,判决出候选网络集中最佳的接入网络。最后,实验结果表明,该算法能根据用户的业务类型合理地选择切换网络,降低切换阻塞率,同时降低算法的时间复杂度。     

认知无线网络频谱分配模型分析

无线频谱资源供需日益紧张,认知无线电技术将空闲授权频谱资源二次利用,从而提高频谱资源的利用率,认知网络被认为是未来无线网络的发展趋势。文章首先简述认知无线网络的基本特征,着重阐述认知无线网络的频谱分配模型:博弈论模型、拍卖竞价模型、图论着色模型以及干扰温度模型,对比各个模型适用场景和特点,指出合理的模型选择可以有效提高频谱利用率。     

基于干扰效率多蜂窝异构无线网络最优基站选择及功率分配算法

针对多蜂窝多用户异构无线网络干扰管理和效率提升问题,该文研究了基于干扰效率最大的下行链路基站(BS)-用户匹配和功率分配问题。首先,考虑宏用户和微蜂窝用户的服务质量,将问题建模为多变量混合整数非线性规划问题。其次将原问题分解为基站选择和功率分配两个子问题。针对基站选择问题,利用凸优化问题获得最优基站选择策略;针对功率分配问题,利用二次变换法和Dinkelbach辅助变量法,将功率分配问题转换为凸优化问题求解。仿真结果表明,与现有算法对比,该算法具有较好的干扰效率和干扰控制性能。

     

基于合作博弈的多信道认知无线网络中的频谱共享算法简

采用合作博弈对多信道认知无线网络中的频谱共享问题进行了建模分析,提出了次用户在各信道上的信干噪比乘积作为合作博弈的效用函数。次用户在各信道上保证对主用户的干扰小于一定门限的要求下,通过最大化各自效用函数的乘积来进行功率分配。由于最大化次用户效用函数的乘积问题是非凸的,通过变量替换将其转化为了一个等价的凸优化问题,利用该凸优化问题的对偶分解,提出了一种次用户间的频谱共享算法。仿真结果表明,所提算法在次用户和速率与公平性之间进行了有效折中。     

Spectrum resource allocation method of maximizing transmission rate in cognitive heterogeneous wireless networks

Aiming at the problem that it is difficult to allocate spectrum resources to secondary users efficiently in cognitive heterogeneous wireless networks with heterogeneous spectrum attributes,dynamic channel conditions and diverse service requirements,a spectrum resource allocation strategy with maximum transmission rate was proposed.Firstly,the strategy aimed at maximizing the total transmission rate,and constrained the limited spectrum resources and user service requirements to construct a non-linear multi-constrained spectrum resource allocation 0-1 planning model.Then a polynomial time complexity simplification method was designed.According to idle spectrum information,channel conditions,business requirements and allocation decision history information,and the benefit matrix was constructed and modified to achieve constraint simplification,and the execution efficiency was improved by improving the coefficient matrix transformation strategy of the traditional Hungarian algorithm.Finally,the performance of the method was compared and analyzed by experiments.Experimental results show that the proposed method has higher transmission rate and execution efficiency.     

Dynamic spectrum allocation in heterogeneous wireless networks under interference constraints across the cell coverage

In order to improve spectrum utilization, dynamic spectrum allocation (DSA) schemes with interference management have been widely investigated, and a special interest is in the current heterogeneous wireless network (HWN) environment. In the previous work, the approach that guarantees quality of service for the cell‐boundary user is extensively used in the DSA scheme. However, such approach gives a pessimistic result. In this paper, we design a DSA scheme for the HWN system, which adopts relatively accurate interference constraints. First, considering that users may randomly locate over the cell, we propose interference constraints across the cell coverage, in which the interference experienced at a point is controlled below the level suffered when using fixed spectrum allocation in only a single network, and the proportion of the cell area where interference is controlled reaches the required area coverage probability. Then under the interference constraints, we formulate the downlink DSA scheme as a combinatorial optimization problem. As the problem is NP‐hard, to reduce the computational complexity, we propose two greedy heuristic algorithms for its solution. Simulation results show that the DSA scheme could improve the total spectrum utility for operators and increase the satisfaction rate of spectrum demands for base stations. Copyright © 2013 John Wiley & Sons, Ltd.     

End-to-end utility-based resource allocation for multi-RAT nodes in heterogeneous cognitive wireless networks

This paper studies the problem of effective resource allocation for multi-radio access technologies (Multi-RAT) nodes in heterogeneous cognitive wireless networks (HCWNs). End-to-end utility, which is defined as the delay of end-to-end communication, is taken into account in this paper. In the scenario of HCWNs, it is assumed that the cognitive radio nodes have the ability of Multi-RAT and can communicate with each other through different paths simultaneously by splitting the arrival packets. In this paper, the problem is formulated as the optimization of split ratio and power allocation of the source cognitive radio node to minimize the delay of end-to-end communication, and a low complexity step-by-step iterative algorithm is proposed. Numerical results show good performance of the proposed algorithm over two other conventional algorithms.     

认知无线多跳网中保证信干噪比的频谱分配算法

为解决无线多跳网络在固定频谱分配方式下所固有的信道冲突等问题,利用认知无线电的动态频谱分配技术,提出了一种适用于次用户组成的无线多跳网络的、underlay方式下的全分布式频谱分配算法。该算法将频谱分配问题建模成静态非合作博弈,证明了纳什均衡点的存在,并给出了一种求解纳什均衡点的迭代算法。大量仿真实验证明,该算法能实现信道与功率的联合分配,在满足主用户干扰功率限制的同时,保证次用户接收信干噪比要求。     

异构无线网络垂直切换技术综述

垂直切换是多网融合的基础,是实现异构网络互通、支持不同接入方式无缝衔接的核心技术,目前正在受到业界的重点关注,并成为学术界研究的热点问题。随着无线移动通信技术向接入多元化、网络一体化和应用综合化的方向发展,各种蜂窝移动接入、宽带无线接入和固定接入将共同接入基于IP的统一核心网络,通过网络间的垂直切换,支持用户的移动性和移动过程中业务的连续性。首先给出了垂直切换的定义和基本概念,介绍了垂直切换的分类和基本流程,随后详细论述垂直切换的切换判决和切换执行2个环节。针对切换判决,总结了现有判决算法,重点评述各代表算法工作原理并剖析论其特点和存在的不足。针对切换执行,详述了现有垂直切换执行机制的工作原理和适用场景,并分析其优缺点。最后,对未来垂直切换技术的研究方向进行了展望。     

动态关断资源栅格的异构无线网络基站节能算法

针对现有的基于载频/时隙关断的基站节能算法没有考虑异构网络之间的协同或者只考虑单一的业务与实际网络情况不相适应的问题,在异构网络环境下提出了动态关断资源栅格(RG,resource grid)的基站节能新算法——DRGSM(dynamic resource grid shut mode)算法。该算法根据网络的即时负载,当有业务接入时,动态打开RG以满足业务的QoS要求;当RG闲置时,即将其关断以实现节能。仿真结果表明,所提算法较现有的基于载频/时隙关断的基站节能算法,明显地降低了能耗,提高了节能百分比。     

Resource allocation for heterogeneous services in multiuser cognitive radio networks

This paper considers a downlink cognitive radio network consisting of one cognitive base station and multiple secondary users (SUs) that shares spectrum with a primary network. Unlike most of previous studies that focus on the SUs that carry only one type of service, in this paper, the SUs that carry heterogeneous services are considered. Specifically, the SUs are classified by service types, that is, the SUs that carry nonreal‐time services and the SUs that carry real‐time services. The QoS of the nonreal‐time SUs is guaranteed by the minimum mean rate constraint, whereas the QoS of the real‐time SUs is guaranteed by the minimum instantaneous rate constraint. Under this setup, a joint subchannel, rate, and power allocation scheme based on dual optimization method is proposed to minimize the mean transmit power consumption of the cognitive base station. The complexity of the proposed scheme is linear in the number of subchannels and the number of SUs. Extensive simulation results are provided to validate the proposed resource allocation scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

一种新的无线异构网络的自适应垂直切换算法

针对当前无线异构网络融合技术中的垂直切换机制,提出了一种以平均接收信号强度为评价指标,并由此指标判断可能的运动趋势的自适应垂直切换算法。仿真结果表明:相比于传统的固定门限的平均接收信号强度垂直切换算法,提出的方法能较好地预测并提前触发该发生的切换,改善切换性能。     

Managing connection costs in heterogeneous wireless networks

Common Radio Resource Management techniques have shown great promise in both enhancing network operation and user satisfication. Such gains are achieved through the joint management of the individual access technologies in a Heterogeneous Wireless Network. The objective of this work is to expand on the existing body of work to accommodate heterogeneity not just at the traditional access‐network level but to other connectivity modes such as dynamic spectrum access. Such modes affect operator profitability in both the long and short terms. Specifically, we explore the design of a cost‐management model that adapts to the short‐term variability in connectivity costs. We also display the operational aspects and effectiveness of this functionality through both simulation and an analytical model. Copyright © 2012 John Wiley & Sons, Ltd.     

Energy-balance node-selection algorithm for heterogeneous wireless sensor networks

To solve the problem of unbalanced loads and the short network lifetime of heterogeneous wireless sensor networks, this paper proposes a node-selection algorithm based on energy balance and dynamic adjustment. The spacing and energy of the nodes are calculated according to the proximity to the network nodes and the characteristics of the link structure. The direction factor and the energy-adjustment factor are introduced to optimize the node-selection probability in order to realize the dynamic selection of network nodes. On this basis, the target path is selected by the relevance of the nodes, and nodes with insufficient energy values are excluded in real time by the establishment of the node-selection mechanism, which guarantees the normal operation of the network and a balanced energy consumption. Simulation results show that this algorithm can effectively extend the network lifetime, and it has better stability, higher accuracy, and an enhanced data-receiving rate in sufficient time.