OFDM系统中一种改进的抗频偏加窗法

该文提出了正交频分复用系统中一种改进的抗频偏接收端加窗的方法,接收端在去除发送端附加的循环前缀后重新进行循环扩展,然后进行奈奎斯特加窗, 并且窗函数不再限于具体的函数形式,是经过优化的数值解。数值计算结果表明,最优窗的抗频偏性能远好于其他窗函数。     

基于非合作博弈论的多小区OFDMA系统动态资源分配算法研究

该文采用非合作博弈论的方法研究了多小区OFDMA系统中的动态资源分配问题,首先将各基站的发射功率平均分配给各子载波,然后由所有小区在每个子载波上独立地进行资源分配博弈,给出了用户调度与功率分配联合博弈框架。为了进一步简化,将用户调度和资源分配分开完成,通过将信道增益引入到定价函数中,提出了一种新的定价机制,建立了用户确定时的非合作功率分配博弈模型,分析了其纳什均衡的存在性和唯一性,并设计了具体的博弈算法。仿真结果表明,所提算法在保证吞吐量性能的同时,进一步提升了系统的公平性。     

Iterative channel estimation and pilot design rules for high‐mobility comb‐pilot OFDM system

With wireless communications in high‐mobility environment becoming popular, this poses a big challenge for communication systems based on the comb‐pilot OFDM, such as IEEE 802.11p, since it has not the enough pilots to estimate the time‐ and frequency‐selective channel accurately. In this paper, several comb‐pilot schemes and three comb‐pilot design rules are proposed to meet the Nyquist criterion for sampling the vehicle‐to‐vehicle (V2V) channel and the requirements of second‐order statistic of V2V channel. Based on the proposed pilot schemes, an iterative channel estimation method from the CE‐BEM model is proposed, together with three ICI cancellation methods. After thorough simulation, the effectiveness of the comb‐pilot design rules, the proposed channel estimation method, and intercarrier interference (ICI) cancellation methods is verified. Compared with other channel estimation methods, the proposed method performs better. The simulation results also reveal that the channel order L+1 has a great impact on the performance of the comb‐pilot OFDM system.     

移动环境下WiMAX的载波间干扰分析

WiMAX系统是基于OFDM技术的,其对于载波频率偏移十分敏感,而多普勒效应会导致频率弥散,带来载波间干扰ICI（Inter Carrier Interference）。本文首先分析了单载波的频率偏移而带来的在其他载波上的功率泄漏,进而分析在不同的多普勒频移下,载波间干扰对性能的影响,即多普勒频移带来的载波间干扰造成的功率抬升对接收信号的影响。     

频率偏移和同步误差对OFDMA系统性能的影响

文章对频率偏移、系统同步性对OFDMA系统误码率等的影响进行了研究。由于多普勒现象产生了频率偏移，系统同步误差产生了OFDM码间干扰，消除OFDMA系统频率偏移及确保良好的同步性对于确保用户间的正交性有着重要意义。通过对OFDMA系统的分析和计算，得出了二者对系统性能影响的全面分析。     

SuperReceiver Design for Superchannel Coherent Optical Systems

In this paper, we propose a novel super-receiver architecture for Nyquist-wavelength-division-multiplexing (WDM) superchannel optical coherent systems. As opposed to a conventional coherent receiver, where each subchannel is demodulated independently, the proposed super-receiver jointly detects and demodulates multiple subchannels simultaneously. By taking advantage of information from side channels that use joint DSP to cancel interchannel interference (ICI), the proposed super-receiver performs much better than a conventional receiver. This architecture also has the potential to compensate for cross-channel impairments caused by linear and nonlinear effects. We examine the proposed architecture through experiment and simulation. OSNR is improved by more than 5 dB after 1280 km fiber transmission with narrow channel spacing.     

A novel adaptive algorithm of CPE correction for OFDM systems

On the basis of the analysis of the effect of PHase Noise (PHN) and Common Phase Error (CPE) on Orthogonal Frequency Division Multiplexing (OFDM) systems, a cost function is constructed. By the cost function and the idea of Least-Mean-Square (LMS) adaptive algorithm, the adaptive algorithm for the correction of CPE is presented. The simulations have been performed to investigate the performance for tracking PHN and estimating CPE, the results show that the algorithm performs soundly.     

Kalman filter‐based channel estimation and ICI suppression for high‐mobility OFDM systems

The use of orthogonal frequency division multiplexing (OFDM) in frequency‐selective fading environments has been well explored. However, OFDM is more prone to time‐selective fading compared with single‐carrier systems. Rapid time variations destroy the subcarrier orthogonality and introduce inter‐carrier interference (ICI). Besides this, obtaining reliable channel estimates for receiver equalization is a non‐trivial task in rapidly fading systems. Our work addresses the problem of channel estimation and ICI suppression by viewing the system as a state‐space model. The Kalman filter is employed to estimate the channel; this is followed by a time‐domain ICI mitigation filter that maximizes the signal‐to‐interference plus noise ratio (SINR) at the receiver. This method is seen to provide good estimation performance apart from significant SINR gain with low training overhead. Suitable bounds on the performance of the system are described; bit error rate (BER) performance over a time‐invariant Rayleigh fading channel serves as the lower bound, whereas BER performance over a doubly selective system with ICI as the dominant impairment provides the upper bound. Copyright © 2008 John Wiley & Sons, Ltd.     

ICI自消除机制下的OFDM信道估计

在正交频分复用(OFDM)系统中,相干解调比差分解调有3 dB的增益,所以一般采用相干解调.为获得准确的信道信息,就需采用基于导频辅助(PSA)的信道估计方法.而在移动多径信道中,时变性致使子载波之间不再严格正交,从而造成子载波间干扰(ICI),影响信道估计性能.对此文中提出了1种基于ICI自消除的新型OFDM信道估计...