基于速率约束的OFDM中继链路能效最优资源分配策略

该文研究解码转发(DF)模式的OFDM中继链路的能效最大化资源分配问题。与现有典型的固定速率最小化发射功率或无约束最大化能效算法不同,该文考虑电路功率消耗的前提下,将问题建模为以最大化系统能效为目标,同时考虑用户最小速率需求、源节点S和中继节点R各自总发射功率约束下的联合子载波配对和最优功率分配问题。证明了速率和功率联合约束条件下中继链路全局能效最优解的唯一性,在此基础上提出一种低复杂度联合最优资源分配策略。仿真结果表明,该文所提方案能够在最小速率和S/R节点最大发射功率约束下自适应分配功率资源,实现系统能效最优,并能够降低链路的中断概率。     

An effective suboptimal power loading scheme in OFDM-based cognitive radio systems

Orthogonal frequency division multiplexing (OFDM) is an attractive modulation candidate for Cognitive Radio (CR) networks. Effective and reliable subcarrier power allocation in OFDM-based Cognitive Radio (CR) networks is a challenging problem. This paper focuses on the power allocation for OFDM-based Cognitive Radio (CR) networks. Our objective is to maximize the total transmission rates of Secondary Users (SU) by adjusting the power of subcarrier while the interference introduced to the Primary User (PU) is within a certain range and the total power of subcarrier is not beyond the total power constraint. We investigate the optimal power allocation algorithm for OFDM-based Cognitive Radio (CR) based on convex optimization theory. Then, because of high complexity of the optimal power allocation algorithm, we propose an effective suboptimal power loading scheme. Theory analysis and simulation results show that the performance of the suboptimal power allocation algorithm is close to the performance of the optimal power allocation algorithm, while the complexity of the suboptimal power allocation algorithm is much lower.     

Resource Allocation of Limited Feedback in Clustered Wireless Mesh Networks

This paper focuses on resource allocation problem of limited feedback in OFDM-based clustered wireless mesh networks. Firstly, the channel quantization codebook is designed according to the equal probability quantizer and joint power, rate and channel quantization threshold codebook scheme (PRCQT) is proposed. Secondly, we deduce the subcarrier allocation criterion utilizing the Lagrange multiplier method. Finally, stochastic resource allocation scheme of limited feedback (SRALF) utilizing the stochastic optimization tools for OFDM-based clustered WMNs is proposed. Simulation results demonstrate SRALF+PRCQT scheme not only improves the network throughput, but also has advantage of limited feedback overhead.     

Multi-cell communications for OFDM-based asynchronous networks over multi-cell environments

This paper investigates a multi-cell communication technique for OFDM (Orthogonal Frequency Division Multiplexing)-based asynchronous networks without the use of a GPS (Global Positioning System). First, a downlink macro-diversity technique using bandwidth division allocation is presented, where each MS (Mobile Station) simultaneously receives control information from surrounding BSs (Base Stations) using an FFT (Fast Fourier Transform) module. Second, a hierarchical master-slave synchronization technique is introduced for plug & access network synchronization. Finally, an adaptive guard carrier allocation scheme is proposed to reduce the effect of MAI (Multiple Access Interference) for users receiving multiple transmission signals from surrounding BSs. In a simulation, the proposed technique is well designed to achieve SSDT (Site Selection Diversity Transmission) and adaptive synchronization for OFDM-based networks. It is particularly noteworthy that this adaptive sub-carrier allocation is very effective in reducing MAI for plug and access network synchronization.     

AGV激光导航中反射板布设研究北大核心CSCD

针对激光导航自动导引车(automatic guided vehicle,AGV)系统中反射板布局质量难以衡量的问题,本文提出了利用水平精度因子(horizontal dilution of precision,HDOP)来表征反射板在空间几何分布质量的方法。水平精度因子反映了定位系统中路标的几何布局与定位精度之间的关系,在相同的测距精度下,待定位置的HDOP值越小,该位置的定位精度就越高。通过定位仿真实验,分析了4种定位方案下HDOP值与定位误差的关系,结果表明,HDOP值较小的位置,AGV的定位精度也越高;在测试点位于反射板所围成的封闭区域内以及合理地增加反射板数目的情况下,测试点的HDOP值较小、定位误差小。基于此,可以通过合理布设反射板的位置、增加反射板的数量,来提高AGV的定位精度。     

基于OFDM认知无线电网络的最优路径算法

针对基于正交频分复用的分布式认知无线电网络,在考虑频谱移动特性的同时,为保证认知用户数据传输的可靠性,提出一种最优路径的基于OFDM认知无线电网络路由算法.该算法首先通过建立认知无线电网络的模型计算信道的期望传输时间和信道干扰,结合类似于按需路由的基本流程得到所有可能的路径.最后,根据最小累积期望传输时间和路径平均吞吐量的指标来选择最优路径.仿真的结果表明,OROCR算法可以明显地减少平均端到端时延,大大地提高平均端到端吞吐量.     

多播认知 OFDM 网络能量效率最大化资源分配算法

将认知无线电技术与正交频分复用(OFDM)相结合是解决目前频谱资源匮乏的首选方案之一。通过采用多播技术, 将对同一内容感兴趣的用户作为一个多播组,为系统提供多播业务,使得相同的无线网络资源能够服务更多的用户,有效地利用有限的频谱资源以及发射功率,有效缓解目前频谱资源紧缺现状,具有重要意义。通过对认知 OFDM 系统的单播多播等方面进行归纳分析,介绍了不同的资源分配方法,研究了基于能量效率最大化的认知 OFDM 系统多播资源分配问题,并分析了解决方法,仿真结果表明该算法的有效性。     

基于OFDM的协同认知网络跨层资源调度

协同通信与认知无线电是未来移动通信的重要技术。针对基于OFDM的无线协同认知网络中的资源分配问题,该文提出了一种有效的跨层资源调度方案。该调度方案在考虑对主用户所受干扰功率进行控制的前提下,以最大化认知用户超帧中总的传输速率为目标,在调度帧中对各传输帧两阶段的子载波进行最佳配对,并为配对子载波分配最优的发送功率。通过分步求解的方法,该调度方案形成的优化问题得到有效解决。仿真结果表明该资源调度方案使得认知用户传输速率有显著提升,方案的可行性与有效性得到了验证。     

Worst subcarrier avoiding water-filling subcarrier allocation scheme for OFDM-based CRN

Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.     

ELPMA: Efficient Localization Algorithm Based Path Planning for Mobile Anchor in Wireless Sensor Network

In operating and managing wireless sensor networks (WSNs) and their applications, the high accuracy of localization and the low operating costs are considered the substantial and key issues. The literature is rich in algorithms for localized WSN devices in hostile and unreachable outdoor environment. Majority of the literature considered mobile anchor as one of the solutions in locating sensor nodes. In this situation, the critical issue is the trajectory planning. All algorithms supposed that the mobile anchor should travel following the shortest path to determine the positions of sensor nodes with minimum localization error. A localization algorithm, which is called efficient localization algorithm based path planning for mobile anchors (ELPMA), is proposed. ELPMA is based on a one-mobile anchor moving in adjustable circular trajectory to scan the target area. It considers that the received signal strength indicator is the ranging function to determine the distance between mobile anchor and sensor nodes. ELPMA supposed the mobile anchor starts the motion from the center of the target area. The travelling paths are planned in advance by ELPMA based on the distance measurements between the mobile anchor and the sensor nodes. Simulation results demonstrate that ELPMA has better performance compared to other algorithms based on static path. This performance was evident in the localization accuracy and trajectory planning.     

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。     

Opportunistic power allocation strategies and fair subcarrier allocation in OFDM-based cognitive radio networks

In this paper we have studied the subcarrier and optimal power allocation strategy for OFDM-based cognitive radio (CR) networks. Firstly, in order to protect the primary user communication from the interference of the cognitive user transmissions in fading wireless channels, we design an opportunistic power control scheme to maximize the cognitive user capacity without degrading primary user’s QoS. The mathematical optimization problem is formulated as maximizing the capacity of the secondary users under the interference constraint at the primary receiver and the Lagrange method is applied to obtain the optimal solution. Secondly, in order to limit the outage probability within primary user’s tolerable range we analyze the outage probability of the primary user with respect to the interference power of the secondary user for imperfect CSI. Finally, in order to get the better tradeoff between fairness and system capacity in cognitive radio networks, we proposed an optimal algorithm of jointing subcarrier and power allocation scheme among multiple secondary users in OFDM-based cognitive radio networks. Simulation results demonstrate that our scheme can improve the capacity performance and efficiently guarantee the fairness of secondary users.     

认知无线电中基于OFDM的频谱分配方法研究

提出了一种基于OFDM的认知无线电系统设计,并从3个方面阐述了OFDM技术在认知无线电中是如何实现频谱资源分配的,研究表明OFDM技术进一步提高了认知无线电系统的频谱利用率。     

Adaptive Fair Subcarrier/Rate Allocation in Multirate OFDMA Networks: Radio Link Level Queuing Performance Analysis

This paper presents a semi-analytical methodology for radio link level performance analysis in a multirate "orthogonal frequency-division multiple-access" (OFDMA) network with adaptive fair rate allocation. Multirate transmission is assumed to be achieved through adaptive modulation, and fair rate allocation is based on the principle of generalized processor sharing to allocate the subcarriers adaptively among the users. The fair rate allocation problem is formulated as an optimization problem with the objective of maximizing system throughput while maintaining fairness (in terms of transmission rate) among the users. The "optimal" fair rate allocation is obtained by using the "Hungarian method." A heuristic-based approach, namely the "iterative approach," that is more implementation friendly is also presented. The throughput performance of the iterative fair rate allocation is observed to be as good as that of optimal fair rate allocation and is better than that of the static subcarrier allocation scheme. Also, the iterative fair allocation provides better fairness compared to that for each of the optimal and the static subcarrier allocation schemes. To this end, a queuing model is formulated to analyze radio link level performance measures such as packet dropping probability and packet transmission delay under the above rate allocation schemes. In this formulation, packet arrivals are modeled by the discrete Markov modulated Poisson process, which is flexible to model different types of traffic arrival patterns. The proposed framework for radio link level performance analysis of multirate OFDMA networks is validated by extensive simulations. Also, examples on the application of the proposed model for connection admission control and quality-of-service provisioning are illustrated     

An OFDM-TDMA/SA MAC Protocol with QoS Constraints for Broadband Wireless LANs

Orthogonal frequency division multiplexing (OFDM) is an important technique to support high speed transmission of broadband traffic in wireless networks, especially broadband wireless local area networks (LANs). Based on OFDM, a new multiple access scheme, called OFDM-TDMA with subcarrier allocation (OFDM-TDMA/SA), is proposed in this paper. It provides more flexibility in resource allocation than other multiple access schemes such as OFDM-TDMA, OFDM-frequency division multiple access (OFDM-FDMA), and orthogonal frequency division multiple access (OFDMA). With OFDM-TDMA/SA, a medium access control (MAC) is designed for broadband wireless LANs. It optimizes bit allocation in subcarriers so that maximum bits are transmitted in each OFDM symbol under a frequency selective fading environment. The OFDM-TDMA/SA MAC protocol also supports three classes of traffic such as guaranteed, controlled-load, and best effort services. Based on the optimum subcarrier bit-allocation algorithm and considering heterogeneous QoS constraints of multimedia traffic, a hierarchical scheduling scheme is proposed to determine the subcarriers and time slots in which a mobile terminal can transmit packets. In such a way, the OFDM-TDMA/SA MAC protocol significantly increases system throughput in a frequency selective fading environment and guarantees QoS of multimedia traffic. Computer simulation is carried out to evaluate the performance of the OFDM-TDMA/SA MAC protocol. Results show that the new MAC protocol outperforms other MAC protocols for OFDM-based wireless LANs. This work was supported by the State of Georgia Yamacraw Project (E21-105).     

Multi-cell uplink power allocation game for user minimum performance guarantee in OFDMA systems

The multi-cell uplink power allocation problem for orthogonal frequency division multiplexing access (OFDMA) cellular networks is investigated with the uplink transmission power allocation on each co-frequency subchannel being defined as a multi-cell non-cooperative power allocation game (MNPG). The principle of the design oftbe utility function is given and a novel utility function is proposed for MNPG. By using this utility function, the minimum signal to interference plus noise ratio (SINR) requirement of a user can be guaranteed. It can be shown that MNPG will converge to the Nash equilibrium and that this Nash equilibrium is unique. In considering the simulation results, the effect of the algorithm parameters on the system performance is discussed, and the convergence of the MNPG is verified. The performance of MNPG is compared with that of traditional power allocation schemes, the simulation results showing that the proposed algorithm increases the cell-edge user throughput greatly with only a small decrease in cell total throughput; this gives a good tradeoff between the throughput of cell-edge users and the system spectrum efficiency.     

A new Walrasian mechanism design for optimal pricing and resource allocation in heterogeneous wireless access networks

In this paper, we address joint spectrum allocation and pricing problem in heterogeneous wireless access networks. In contrast to traditional static spectrum allocation approach, we model the spectrum as a market commodity, dynamically arbitrated by a regulatory agent with the aim of maximizing the social welfare. This is of particular importance with the dominance of wireless technologies in access networks and the sharp increase in the number of overlapping wireless technologies and networks. We designed a novel Walrasian mechanism called economic resource allocation and pricing based on a three-stage game model capable of considering multiple networks and clients with individual attributes and preferences. In the first stage, competition among networks for spectrum allocation is handled where the regulatory evaluates the social welfare and takes corrective action. In the bottom two stages, the complex interactions between clients and networks result in bitrate allocations and service pricings. The equilibrium condition is analyzed using the Walrasian market model which is argued to be the Nash equilibrium of the proposed game. The system behavior is analyzed through extensive simulations. The results confirm the effectiveness of the proposed mechanisms in moving the system towards maximal social welfare.

     

基于加权协商对策论异构网络快速无线传输的速率分配算法

本文研究异构无线网络合作传输的速率分配问题.作为合作传输的理性参与者,异构网络可通过反复协商得到彼此都满意的最优分配方案,即协商对策.因此,本文在速率需求和可用带宽这两个约束条件下,考虑网络传输能力的异构性,用加权协商对策论对异构网络合作传输的速率分配进行了数学建模;以最小传输时间作为优化目标构造了效用函数,证明了该函数是一个凸函数,并利用拉格朗日乘数法推导出最优显式解;提出了一种在终端上可实现的速率分配算法,进行了性能仿真实验.本文算法特别适合于应急通信等快速传输场景.     

弹性光网络中基于自适应调制的碎片感知共享通路保护算法

为了提高弹性光网络(EON)的频谱利用率,提出一种基于自适应调制的碎片感知共享通路保护算法。该算法利用频谱块承载权重(SBBW)衡量不同频谱块接纳业务的能力,优先选择SBBW大的链路构成候选工作路径,并利用分配前、后SBBW差值最小的频谱块建立工作路径。然后选择可用频谱块和保护频谱块承载能力大的链路构成候选保护路径,建立保护路径时优先使用分配前、后SBBW差值最小的保护频谱块,建立失败时才选择分配前、后SBBW差值最小的可用频谱块。仿真结果表明:该算法可以降低带宽阻塞率、频谱碎片率和备用容量冗余。     

Novel DV-Hop localization algorithm for wireless sensor networks

Many improved DV-Hop localization algorithm have been proposed to enhance the localization accuracy of DV-Hop algorithm for wireless sensor networks. These proposed improvements of DV-Hop also have some drawbacks in terms of time and energy consumption. In this paper, we propose Novel DV-Hop localization algorithm that provides efficient localization with lesser communication cost without requiring additional hardware. The proposed algorithm completely eliminates communication from one of the steps by calculating hop-size at unknown nodes. It significantly reduces time and energy consumption, which is an important improvement over DV-Hop—based algorithms. The algorithm also uses improvement term to refine the hop-size of anchor nodes. Furthermore, unconstrained optimization is used to achieve better localization accuracy by minimizing the error terms (ranging error) in the estimated distance between anchor node and unknown node. Log-normal shadowing path loss model is used to simulate the algorithms in a more realistic environment. Simulation results show that the performance of our proposed algorithm is better when compared with DV-Hop algorithm and improved DV-Hop—based algorithms in all considered scenarios.