Hungarian algorithm for subcarrier assignment problem using GPU and CUDA

General purpose graphics processing units (GPGPUs) have gained much popularity in scientific computing to speedup computational intensive workloads. Resource allocation in terms of power and subcarriers assignment, in current wireless standards, is one of the challenging problems due to its high computational complexity requirement. The Hungarian algorithm (HA), which has been extensively applied to linear assignment problems (LAPs), has been seen to provide encouraging result in resource allocation for wireless communication systems. This paper presents a compute unified device architecture (CUDA) implementation of the HA on graphics processing unit (GPU) for this problem. HA has been implemented on a parallel architecture to solve the subcarrier assignment problem and maximize spectral efficiency. The proposed implementation is achieved by using the “Kuhn‐Munkres” algorithm with effective modifications, in order to fully exploit the capabilities of modern GPU devices. A cost matrix for maximum assignment has been defined leading to a low complexity matrix compression along with highly optimized CUDA reduction and parallel alternating path search process. All these optimizations lead to an efficient implementation with superior performance when compared with existing parallel implementations.     

Generalized OSTBC‐based subcarrier intensity‐modulated MIMO optical wireless communication system

In this paper, we analyze an optical wireless communication (OWC) system having a source and a destination node, equipped with multiple transmit and receive apertures, respectively. We utilize generalized orthogonal space‐time block codes (OSTBCs) of any arbitrary order and subcarrier intensity modulation scheme for data transmission over gamma–gamma (GG) fading optical links using M ‐ary phase‐shift keying (PSK) constellation. A symbol‐wise decoding is utilized, and the closed‐form expression of the approximate average symbol error rate (SER) of multi‐aperture‐based OWC system is obtained for the generalized OSTBC and an arbitrary M ‐PSK constellation. Using the derived SER expression, we analytically evaluate the diversity order and the coding gain of the OWC system with GG atmospheric turbulence. It has been shown by the numerical results that the maximum possible diversity is achieved by using the symbol‐wise maximum likelihood decoding in the destination. Copyright © 2016 John Wiley & Sons, Ltd.     

联合子载波抑制与配对的双向DF-PLNC OFDM中继

子载波抑制(SS)技术已被证明能够显著提高正交频分复用(OFDM)系统的误码率性能,因此引起了学术界的广泛关注。在双向OFDM中继网络(TWRN)中,由于两个源节点与中继之间的链路具有独立性,直接应用子载波抑制技术会造成两条链路的活跃子载波具有非对称性,从而导致大量子载波在中继节点无法实现网络编码。提出了一种联合子载波抑制与子载波配对(SP)的双向译码转发(DF)-物理层网络编码(PLNC)OFDM中继系统。该方法对中继两端链路的非对称活跃子载波进行配对,在配对的子载波上发送物理层网络编码信息。仿真结果表明,该方法显著改善了误码率性能,消除了原有的误码平台并且提高了系统的吞吐量性能。     

Broadband access using subcarrier multiplexing and asymmetric digital subscriber lines

A broadband access system using subcarrier multiplexing on optical fibre and asymmetric digital subscriber lines (ADSL) or very high‐speed digital subscriber lines (VDSL) on unshielded twisted‐pair is proposed to provide broadband access. In this hybrid‐fibre/twisted‐pair (HFTP) system, the digital multiplexing/demultiplexing process is moved back to the central office by using subcarrier multiplexing for fibre transmission. Instead of installing in remote node, ADSL/VDSL transceivers are installed at the central office to greatly reduce the remote node complexity. The local node simply down‐converts the subcarrier multiplexed ADSL/VDSL signal to the baseband, suitable to send directly into the twisted‐pair. The reduction of complexity could result in a lower initial installation cost, especially for a low service penetration rate. Copyright © 2000 John Wiley & Sons, Ltd.     

Power distribution methods for MIMO‐OFDM systems and field experimentations

In this paper, we propose several power allocation schemes for multi‐input multi‐output (MIMO) orthogonal frequency division multiplexing (OFDM) transmission based on the minimization of an approximated bit error rate (BER) expression, and we evaluate the different solutions via field trial experimentations. The methods illustrated in this paper, serve to allocate power among the different transmit antennas and the different subcarriers which compose the MIMO OFDM transmitted signal. Several solutions are available to perform power allocation. Frequency domain power allocation, spatial domain power allocation and combined spatial and frequency power allocation are evaluated. We first review and describe the analytical solution for each power allocation scheme and then evaluate the complexity in terms of both computational operations and BER performances. Simulation results show the performance in term of BER and link the advantage of each possibility of power distribution with the associated complexity. Copyright © 2009 John Wiley & Sons, Ltd.     

自适应偏振模色散补偿中控制信号的研究

文章比较了两种在自适应偏振模色散（PMD）补偿设备中控制信号的控制方法,即前馈（Feed Forward）检测控制和反馈（Feedback）检测控制;分析比较了各种可用作控制的信号,包括偏振度（DOP）、信号频率分量、眼开代价、两正交主极态（PSP）上光信号分量间的相位差和副载波信号等。     

子载波个数对非对称限幅光正交频分复用误码率的影响

误码率(BER)是非对称限幅光正交频分复用(ACO-OFDM)的一项重要性能指标,子载波个数是影响这一性能指标的重要因素。通过理论推导及仿真证明的方法,分析了子载波个数对光域单边带ACO-OFDM信号在单模光纤中传输时系统误码率的影响。结果表明,在总传输速率一定时,改变子载波个数从128个到16384个,所需要的总带宽改变不超过0.775%。并在此基础上,通过实验证明了不同的传输速率下ACO-OFDM系统均存在使系统误码率最低的最优子载波个数,实验结果表明该最优子载波个数随传输速率的增加而增加。     

面向2G/3G/4G/WLAN融合接入应用的光载无线分布式天线系统

文章认为满足2G/3G/4G/WLAN四网融合业务的多样性、多业务等级、高品质要求,需要建设能够实现宽带接入的光载无线分布式天线网络。为了实现低成本、高性能、多业务融合接入的光载无线(ROF)分布式天线网络,文章基于商用的千兆以太网光器件,设计了低成本、宽带的光收发模块;利用光损耗和受激布里渊散射(SBS)效应对链路传输性能的影响,基于激光器线宽展宽技术,抑制了受激布里渊散射效应;采用副载波复用技术,实现了点到点的多业务混合传输;采用粗波分复用技术,实现了点到多点的多业务分布式传输。     

基于碰撞概率约束的认知系统子信道分配算法

针对如何在保护主用户的同时最大化有效吞吐量的子信道分配问题,考虑由于主用户的重新到来而造成的主次用户碰撞,给出一种基于子信道碰撞概率约束的子信道分配算法。算法通过约束子信道碰撞概率来保护主用户,依据碰撞概率约束估计各子信道可容忍最大传输时长,随后认知用户根据请求业务时长选择合适的子信道接入。仿真结果表明,与不考虑子信道碰撞概率约束的算法相比,该分配算法很好地保护了主用户,且在信道条件较好时,能取得更好的有效吞吐量性能。     

具有时延QoS保证的OFDM中继系统子载波配对与功率分配算法

 本文研究具有直接通信链路的OFDM解码转发(Decode-and-Forward,DF)中继系统的子载波配对与功率分配算法,目标是在满足业务时延QoS要求的前提下最大化系统容量.利用有效容量模型,首先把OFDM DF中继系统的子载波配对与功率分配问题形成为混合整数规划问题,然后把其转化为连续松弛凸规划问题,利用凸优化方法得到原问题的最优解,从而提出了一种联合最优的子载波配对与功率分配迭代算法.理论推导结果和仿真结果表明,最优子载波配对与功率分配不仅取决于子载波的信道增益,还取决于业务的时延QoS要求.与已有算法相比,本文算法获得的有效容量最大.