An Iterative Receiver for Uplink of Coded MIMO DS-CDMA System Employing Layered Space-Time Transmission

We consider a coded multiple-input multiple-output (MIMO) DS-CDMA system using layered space-time transmission in multipath wireless channels, where space-time signals from multiple antennas of multiple users propagate through rich scattering multipath fading. We propose a receiver employing iterative joint detection and decoding with a reduced-complexity detector using linear minimum mean squared error filtering with a priori information and parallel soft-input soft-output (SISO) decoders. Computer simulation results show that the proposed receiver for multi-user MIMO transmission provides high-spectral efficiency and performance approaching to single-user bound. Furthermore, the reduced-complexity receiver outperforms an iterative soft decision-directed maximal ratio combining (DD-MRC) receiver, RAKE receiver as well as a conventional non-iterative receiver.     

Turbo码中交织器的综合性能分析与设计

在Turbo码理论中,交织器占有重要地位。论文分析了Turbo码的编译码方案,阐明了交织器在Turbo码设计中的重要作用,提出了几种交织器的设计实现方法,并在仿真的基础上对其性能进行了分析。     

MIMO-OFDM系统Turbo接收机中的限幅非线性失真迭代对消法

在多入多出的正交频分复用系统中,常采用Turbo接收以保证系统性能。在正交频分复用系统中,限幅技术是常见的峰值平均功率比抑制技术,但限幅带来的非线性失真会造成带内失真和带外辐射,从而恶化系统性能。本文提出可以利用Turho接收机的先验信息进行限幅非线性失真的迭代对消,从而在引入少量复杂度的基础上,对抗限幅带来的影响。仿真结果表明,引入限幅非线性失真迭代对消算法可以有效提高系统性能,限幅门限越低效果越明显。     

交织器最优化设计的理论分析基础及其工程仿真

交织器的设计作为Turbo码技术的关键性的核心环节,一直缺乏系统的理论设计和明确的优化准则.为此,本文首先探讨了交织器优化设计的理论基础和Turbo码性能卓越的深层原因,从码重分析(空间离散)和相关性分析(时间离散)两个方面建立交织器优化设计的数学模型,提出了单交织器设计的优化准则S₆函数.在此基础上,又提出了权位倒置交织器,经工程仿真证明性能良好,无论在理论分析方面还是在仿真数据上,其性能都明显优于3GPP标准中(3G TS 25.212 V3.3.0)的mother_-interleaver(文中称为标准交织).     

非线性等重码的一个上界

本文给出等重码的一个上界，并且举例说明这个上界是可以达到的，作为直接推论，我们推导出等重等距码的几个结果。     

Evolution of spectroscopic information over the last decade and its effect on line-by-line calculations for validation of radiation codes for climate models

Five HITRAN's editions (since 1992) and three radically new H₂O spectral databases have been tested for their usefulness in line-by-line benchmark calculations for radiation code validations. The longwave calculations for the mid-latitude summer (MLS) atmosphere with the different HITRAN's editions revealed a good convergence (maximal discrepancies since decreased to in our flux calculations with 1992-2002 and 1996-2002 HITRAN's editions, respectively). The shortwave calculations with different HITRAN's editions revealed a good agreement: discrepancies in downward fluxes absorbed by the MLS atmosphere are less than , i.e. 0.5% for the all HITRAN's editions since 1992. It has been determined that it is unreasonable to replace HITRAN by any new H₂O spectral database in benchmark calculations, although they contain essentially more spectral lines than HITRAN (up to ∼10 times). Moreover, it has been found that no new database could be useful for explaining the “anomalous absorption” problem. Two latest water vapor continuum models have been tested as well. It has been found out that these models are the main source of uncertainties in the present and previous calculations: discrepancies for the MLS atmosphere reached ∼3 and in the longwave and shortwave flux calculations, respectively.     

Turbo均衡仿真研究与应用

Turbo均衡利用Turbo码译码算法中提出的迭代思想,在均衡器和译码器之间反复迭代可靠性信息,提高了均衡译码的整体性能。通过仿真研究了基于线性MMSE检测的Turbo均衡算法和基于软值干扰抵消的Turbo均衡算法在实际系统中的性能,给出了仿真结果和结论。基于线性MMSE检测的Turbo均衡已经在实际的跳频通信系统中得到应用。     

MSK信号的Turbo同步

Turbo码的提出使系统的性能对同步参数变得极为敏感。文章利用Turbo同步的方法来对Turbo系统进行迭代参数估计,并用插值的方法来减少译码复杂度,最后针对MSK信号给出同步算法。仿真结果表明,在少量增加译码复杂度的情况下,Turbo同步能够使系统获得与严格同步近似的性能。     

TD-SCDMA中Turbo编码算法在ZSP500 DSP核上的实现

文章对TD-SCDMA系统中的Turbo编码器结构及编码算法进行了分析，给出了TD-SCDMA系统中Turbo算法在ZSP500 DSP核上的实现，并根据ZSP500 DSP核的特点对实现部分的进行了阐述。     

Turbo equalization of serially concatenated turbo codes using a predictive DFE-based receiver

This paper investigates the performance of various “turbo” receivers for serially concatenated turbo codes transmitted through intersymbol interference (ISI) channels. Both the inner and outer codes are assumed to be recursive systematic convolutional (RSC) codes. The optimum turbo receiver consists of an (inner) channel maximum a posteriori (MAP) decoder and a MAP decoder for the outer code. The channel MAP decoder operates on a “supertrellis” which incorporates the channel trellis and the trellis for the inner error-correcting code. This is referred to as the MAP receiver employing a SuperTrellis (STMAP). Since the complexity of the supertrellis in the STMAP receiver increases exponentially with the channel length, we propose a simpler but suboptimal receiver that employs the predictive decision feedback equalizer (PDFE). The key idea in this paper is to have the feedforward part of the PDFE outside the iterative loop and incorporate only the feedback part inside the loop. We refer to this receiver as the PDFE-STMAP. The complexity of the supertrellis in the PDFE-STMAP receiver depends on the inner code and the length of the feedback part. Investigations with Proakis B, Proakis C (both channels have spectral nulls with all zeros on the unit circle and hence cannot be converted to a minimum phase channel) and a minimum phase channel reveal that at most two feedback taps are sufficient to get the best performance. A reduced-state STMAP (RS-STMAP) receiver is also derived which employs a smaller supertrellis at the cost of performance.