基于PPM调制的超宽带Rake接收机性能研究

室内环境中超宽带(UWB)信号经过密集多径传播会产生严重的时间弥散,采用Rake接收是提高UWB接收机性能的重要手段.在IEEE802.15.3a工作组推荐的信道模型基础上,采用脉冲位置调制(PPM)方式对超宽带信号在不同信道情况下不同Rake接收机的性能进行了系统的研究,可以在选择Rake接收机时,为综合考虑系统复杂度和性能改善的优化问题提供有价值的参考.     

60 GHz芯片间无线互连系统中的Rake接收性能

在60 GHz芯片间无线互连信道中存在着多径干扰问题,采用Rake接收是提高系统性能的重要手段。针对脉冲超宽带( IR-UWB)的芯片间无线互连系统,分析了多径信道下Rake接收机的误码性能。在IEEE 802.15.3 c信道模型基础上,对不同分支数以及不同合并方案下的选择Rake ( S-Rake)和部分Rake(P-Rake)接收机误码性能进行了研究。仿真结果表明采用支路数为2的P-Rake在数据速率为10 Gb/s时仍具有良好的抗多径性能,这为芯片间无线互连系统的Rake接收方案提供了技术参考。     

超宽带Rake接收机的性能分析

超宽带信号经多径信道传播会产生严重的时间弥散，采用Rake接收是提高超宽带接收机性能的重要手段。文中首先介绍了加性高斯白噪声信道模型和IEEE802．15．3a标准信道模型。通过比较分析几种典型调制的超宽带冲激无线电信号的最佳接收机，推广到Rake接收机的性能分析。重点分析并仿真了不同信道、不同调制方式、不同判决方式、不同合并方式、不同速率的情况下Rake接收机的性能。     

Hermite脉冲超宽带系统在多径信道的性能分析

研究了一种基于Hermite脉冲的超宽带系统在多径信道下的性能。考虑到定时抖动对Rake相关接收的影响,通过Hermite脉冲的相关函数可以计算Rake捕获的信号能量,进而得到接收机的输出信干比。在假设符号间干扰为高斯噪声下,得出系统在多径信道下的理论误比特性能。结果表明,符号间干扰能量对Rake接收机合并路径数目的变化并不敏感;增加合并路径数目可以提高系统的误比特性能;大的定时抖动范围会造成系统性能下降。     

超宽带信道仿真及分析

超宽带信道模型中多径分量的到达采用了两个泊松随机过程,各径幅度衰落服从对数正态分布,对模型的仿真和分析结果表明:超宽带信道中存在较多可分离的多径分量,通过Rake接收技术对这些多径分量有效的合并,能提高超宽带系统的性能,由于多径信号衰落的非递减性,采用选择Rake技术的性能优于部分Rake.     

超宽带接收机结构的优化设计

基于IEEE802.15.3a室内超宽带多径信道模型,采用二进制相移键控(BPSK)调制方式时,选用最大比合并(MRC)方式的Rake接收机的超宽带通信系统的性能进行了仿真,得出了最佳的合并叉指数目.     

基于平衡Gold码的TH-UWB系统性能分析

针对有码间干扰的跳时脉冲脉位调制超宽带(PPM-TH-UWB)通信系统,为了在不增加系统复杂度的前提下,提高系统抗码间干扰的性能,研究了基于平衡Gold码的Rake接收机的性能,并在IEEE 15.3a UWB信道下对采用平衡Gold码作为跳时序列的Rake接收机和采用传统伪随机序列的Rake接收机的误比特率进行计算机仿真比较,结果表明:采用平衡Gold码作为跳时序列,Rake接收机得到明显改善,而且码间干扰越严重,性能提升越显著。     

无线传感网低功耗Rake接收机VLSI设计与实现

针对近地无线信道变化多端的多径现象,该文提出了一种用于复杂信道环境下的低功耗无线传感网Rake接收机VLSI方案并在FPGA上实现。仿真和应用表明,该Rake接收机不仅具有良好的抗多径衰落性能,而且与常规Rake接收机相比,显著节省了VLSI资源并降低了功耗。     

基于TH-PPM-UWB多径信道下的Rake接收机性能分析

超宽带信号在无线信道中传播会产生严重的衰落和多径干扰等问题,而在抗多径干扰方面采用Rake接收机的方式是一种行之有效的手段.利用IEEE802.15.3a标准信道模型,采用TH-PPM调制方式对信道冲激响应的特性进行了分析,并对标准信道模型下的A-Rake,P-Rake和S-Rake三种接收机模型在不同的支路下的BER进行了对比分析.从仿真结果可以得出A-Rake为理想接收机性能最佳,相同支路下S-Rake接收机的性能要优于P-Rake接收机,但是随着支路数的增加两者的性能差距也越来越小.     

一种改进的基于二维扩频的WCDMA非Rake接收机

针对WCDMA发射的扩频信号,不同于传统的Rake接收算法,本文采用变换域处理技术,提出了一种充分利用多径能量的二维扩频接收技术。分析了这种充分利用多径能量的二维扩频接收机的算法复杂度。通过计算机仿真,比较了传统的Rake接收算法、充分利用多径能量的二维扩频接收算法的误码率性能。结果表明,在Rake接收机难以精确分辨信道中的每条多径的情况下,使用充分利用多径能量的二维扩频接收机具有更好的误码率性能。     

基于IEEE UWB标准信道模型的RAKE接收机性能分析

超宽带信号经多径信道传播会产生严重的时间弥散。采用RAKE接收是提高超宽带接收机性能的重要手段。介绍了Intel的UWB多径信道模型。对采用TH-PPM调制的超宽带系统在Intel多径信道模型下A-RAKE，S-RAKE和P-RAKE的误码率性能和对系统复杂性的要求进行了分析。在实际的RAKE接收机设计中，S-RAKE和P-RAKE的性能与支路数有关，S-RAKE要优于P-RAKE。S-RAKE和P-RAKE的性能随着支路的增加而减小。     

户内多径信道中 PRF 对 UWB 系统性能影响

首次研究分析脉冲重复频率(PRF)对密集多径衰减信道下采用 THSS 和 PPM 的 UWB 系统 BER 性能的影响。通过使用混合选择／最大比率结合分集接收机(H-S／MRC)并利用虚拟分支技术,首次推导出基于 PRF、选择并结合的多径成分数量 L 以及信道的多径扩频的 UWB 系统准确 BER 表达式,并对 BER 性能进行分析和仿真评估。结果表明：在密集多径衰减环境下,不仅仅脉冲波形和 L,而且 PRF 对 UWB 系统 BER 性能影响极大。当固定 L 和脉冲波形时,增大 PRF 将大大降低 UWB 系统 BER 性能。     

A novel correlation adaptive receiver structure for high speed transmissions in ultra wide band systems with realistic channel estimation

Impulse radio ultra wide band (UWB) communications require robust receivers; typically Rake receivers are required to capture a large number of resolvable paths, (even hundred of paths), so large number of correlators are needed; otherwise, adaptive receivers use complex filters and channel estimation algorithms. Therefore, traditional Impulse radio receivers demand non-practical implementation structures. In this paper we propose a novel correlation-adaptive receiver structure with low complexity for indoor high speed ultra wide band systems. This novel structure combines correlation characteristics from Rake receivers with recursive filters from adaptive receivers. The receiver includes a low complexity recursive channel estimation filter capable of estimating hundreds of channel impulse responses, and a single filter-correlation filter used for coherent bit demodulation. Furthermore, we derive by simulations the bit error rate for high density multipath environments for several impulse radio modulations like TH-PPM, DS-BPSK and TH-BPSK and we compare the performance of the proposed structure with typical Rake receivers.     

Low Complexity Rake Receivers in Ultra-Wideband Channels

One of the major issues for the design of ultra-wideband (UWB) receivers is the need to recover the signal energy dispersed over many multipath components, while keeping the receiver complexity low. To this aim we consider two schemes for reduced-complexity UWB Rake receivers, both of which combine a subset of the available resolved multipath components. The first method, called partial Rake (PRake), combines theirs/ arriving multipath components. The second is known as selective Rake (SRake) and combines the instantaneously strongest multipath components. We evaluate and compare the link performance of these Rake receivers in different UWB channels, whose models are based on extensive propagation measurements. We quantify the effect of the channel characteristics on the receiver performance, analyzing in particular the influence of small-scale fading statistics. We find that for dense channels the performance of the simpler PRake receiver is almost as good as that of the SRake receiver, even for a small number of fingers. In sparse channels, however, the SRake outperforms the PRake significantly. We also show that for a fixed transmitted energy there is an optimum transmission bandwidth     

水声多径信道中的标识延迟空时扩展发射分集

水声信道存在严重的传播时延和多径时延,该文提出了一种带有信道标识的延迟空时扩展(LDSTS)发射分集方案,通过信道探测、延时发射和Rake接收来消除传播时延和多径时延的影响,且顺序延时发射保证了方案的实用性。文中给出了采用频移键控和相移键控调制的LDSTS方案的信号模型、误码率分析和比特误码率的仿真。仿真表明,在多径水声信道中,LDSTS可以更好地实现完全发射分集。     

BER performance analysis of the discrete time and the continuous time Rake receivers for the UMTS downlink

The paper gives the bit error rate (BER) expressions of the continuous time and discrete time Rake receivers (CTR and DTR) for the UMTS downlink. The former receiver is the most used and consists in combining the output of correlators locked on the most significant paths. Since the conventional synchronization module of the CTR is hot able to distinguish close paths, a discrete time implementation of the Rake receiver which circumvents the problem of path delay estimation was proposed in previous papers. The DTR consists in a matched filter to the discrete time equivalent model of the global channel resulting from the convolution of the impulse response of the transmitter shaping filter and the multipath channel. Using the assumption of Gaussian noise on the receiver output, we derive the BER expressions of both the CTR and DTR. The obtained expressions are valid for any multipath channel and take simultaneously into account path gain estimation noise, the intersymbol interference and the multiuser interference which is a realistic scenario for the UMTS downlink. Based on this theoretical study, a power control policy is also formulated.     

一种改进的超宽带瑞克接收机

脉冲超宽带(IR-UWB)信号在密集多径环境中存在严重的时间弥散,会产生波形失真.针对BPSK调制的UWB通信系统,分析了在加性高斯白噪声(AWGN)密集多径衰落信道下,利用改进的Hermite基波合成波形作为模板的等增益合并部分RAKE(PRAKE)接收机的误码率性能.仿真结果表明了其有效性.