Turbo码综合性能分析与Turbo编码调制

对 Ｔｕｒｂｏ码的 ＲＳＣ分量码、交织器、调制方式、信道以及迭代译码算法进行了综合研究与性能分析，并给出了一种基于逐比特ＭＡＰ算法的Ｔｕｒｂｏ编码与多元调制相结合的编码调制方式。仿真结果表明，该方案将Ｔｕｒｂｏ码的高编码增益与多元调制的高频谱利用率有效地结合在一起，是一种功率和频谱高效的编码调制方式，比传统的ＴＣＭ方式有更好的性能。     

正交多载波码分多址系统性能分析

基于多载波并行传输的码分多址技术（ＭＣ－ＣＤＭＡ）是第三代数字移动系统研究中的一个热门课题。将信道纠错编码（卷积码和Ｔｕｒｂｏ码）技术与ＭＣ－ＣＤＭＡ系统相结合,充分利用了纠错编码（特别是Ｔｕｒｂｏ码）在低信噪比时的优异性能,大大提高了系统的纠错能力。分析了系统在不同信道中的误码性能,并给出了相应的计算机模拟结果。     

Turbo码在移动通信系统中的应用

Ｔｕｒｂｏ码是在１９９３年的国际通信会议（ＩＣＣ’９３）上由法国学者Ｃ．Ｂｅｒｒｏｕ等人率先提出的一种新型信道编码方案。Ｔｕｒｂｏ码很好地应用了香农信道编码定理中的随机性编译码条件,从而获得了接近香农理论极限的译码性能。由于其很强的抗衰落、抗干扰能力,Ｔｕｒｂｏ码在ＩＮＭＡＲＳＡＴ－ｐｈｏｎｅＭ４系统,ＣＤＭＡ多用户检测和第三代移动通信系统ＩＭＴ－２０００中得到了广泛的应用。但Ｔｕｒｂｏ码也存在着     

Turbo码和高频谱利用率调制技术

本文论述了Ｔｕｒｂｏ码的基本原理和译码器结构。介绍一种联合Ｔｕｒｂｏ码调制方案，并将之与格状编码调制方案进行比较。     

Turbo Codes在INMARSAT移动卫星通信系统中的应用

本文介绍了的是ＩＮＭＡＲＳＡＴ最新推出的增强型ｍｉｎｎｉ－Ｍ系统－ＩＮＭＡＲＳＡＴ－ｐｈｏｎｅＭ４中用以实现“压缩频带的高速数据（ＨＳＤ）传输”的核心技术Ｔｕｒｂｏ Ｃｏｄｅｅｓ的具体应用方案。着重阐述Ｔｕｒｂｏ Ｃｏｄｅｓ与多电平调制结合方式,信道状态信息提取,编译码器的性能和实现上有待解决的关键问题。     

P－TCM在卫星移动通信信道上的性能

实用化网格编码调制（Ｐ－ＴＣＭ）方案能够利用同一芯片实现不同码率的网格码之编译码过程，其性能在加性高斯白噪声信道上与ＵｎｇｅｒｂｏｅｃｋＴＣＭ码相比差别不大。本文针对编码率为２／３的６４状态Ｐ－ＴＣＭ码，从理论上计算了在相干检测和差分检测两种情况下，该码在Ｒｉｃｉａｎ信道上和轻微遮挡的Ｒｉｃｉａｎ信道上的误比特率上、下限或渐进曲线，并且给出了相应的计算机仿真结果。结果表明，当误比特率为１０－３时，该码在上述信道上约有３．４ｄＢ～５．２ｄＢ的编码增益。     

采用MT—TCM的跳频／扩频多址系统的性能研究

本文采用不降低扩频处理增益的多音网格编码调制（ＭＴ－ＴＣＭ）及改进的交织ＭＴ－ＴＣＭ方案来提高跳频／扩频多址系统的性能，对于给定的总跳频带宽，跳束和符号速率，考虑加性白高斯噪声，部分带宽干扰与多有户干扰的综合影响，推导出估计比特错误率的计算公式。给出数值与模拟结果，并与采用卷积编码的跳频／扩频多址系统的性能作了比较。     

P—TCM在卫星移动通信信道上的性能

实用化网格编码调制方案能够利用同一芯片实现不同码率的网格码之编译码过程，其性能在加性斯白噪声信道上与Ｕｎｇｅｒｂｏｅｃｋ ＴＣＭ码玎比差别不大。本文针对编码率为２／３的６４状态－ＰＴＣＭ码，从理论上计算了在相干检测和差分检测两种情况下，该码在Ｒｉｃｉａｎ信道上和轻微遮挡的Ｒｉｃｉａｎ信道上的误比特率上，下限或渐进曲线，并且给出了相应的计算机仿真结果。     

市区多径衰落信道中的TCM DS／SSMA系统性能分析

本文将网络编码调制（ＴＣＭ）应用于市区多径衰落信道下的直接序列扩频多址（ＤＳ／ＳＳＭＡ）系统中，应用ＤＳ条件下市区多径衰落信道的等效模型，提出了一种采用理论分析和数值模拟相结合分析ＴＣＭＤＳ／ＳＳＭＡ系统在该信道下性能的新方法，并将传统的Ｕｎｇｅｒｂｏｅｃｋ型ＴＣＭ才本文所构成的若干种低码率ＴＣＭＤＳ／ＳＳＭＡ系统的性能进行了比较。     

TCM正交序列扩频多址通信系统性能分析

将纠错技术与扩频相结合，是进一步提高扩频多址通信系统性能的重要手段之一。本文研究了在正交码扩频通信系统中，应用ＴＣＭ（网格编码调制）的原理，通过对信号集的扩展和分割，使发送信号序列间的最小欧氏距离得以增加，性能分析和计算机模拟表明，在存在加性高斯白噪声和多址干扰的信道环境中，扩频通信系统的性能得到了显著的提高。     

Performance of 4- and 8-state TCM schemes with asymmetric 8-PSK infading channels

For Rayleigh fading channels, Ricean fading channels with a small parameter and shadowed Rician channels with the code design criteria are to maximize the effective length as well as the minimum product distance of the code. In this paper, we use two different asymmetric 8-PSK signal sets in 4-state and 8-state rate 2/3 trellis-coded modulation (TCM) schemes and show performance gain over TCM schemes with symmetric 8-PSK constellations. The performance gain is due to an increase in the minimum product distance compared to that of the best known TCM schemes of comparable states using symmetric 8-PSK signal sets while the effective length remains same. Simulation is performed over the Rayleigh, Ricean, and shadowed Rician fading channels to demonstrate the performance gain of the asymmetric 8-PSK TCM schemes over the symmetric 8-PSK TCM     

Combination of BCM and TCM with 90°, 180°, and 270°phase rotational invariance

Two systematic schemes to combine block-coded modulation (BCM) and trellis-coded modulation (TCM) are proposed. In the first scheme, the signal points which are used in TCM should be partitioned by the proper BCM systems constructed by a multilevel construction method. The asymptotic coding gain will be 6.02-3.01/n dB, where n is the length of the BCM systems. Since the average transmission power can be reduced by using a denser signal lattice, the main idea of the second scheme is to construct the TCM system based on the signal points of a denser lattice formed by a proper BCM system. Hence, we can get a higher coding gain which is a combination of both the distance gain of TCM and the density gain of BCM. Theoretically, the net coding gain of this proposed scheme can reach 5.27 dB in the case of an 8-D constellation and 7.15 dB in the case of a 16-D constellation. For practical implementation, the phase ambiguity problems for both schemes are considered and solved by a differential encoder/decoder     

基于非编码信息匹配的自适应Turbo TCM编码调制方案

本文提出了一种通过调整非编码信息量,并与信号映射相结合来改变编码、调制模式的自适应Turbo TCM编码调制方案,称之为基于非编码信息匹配的自适应Turbo TCM编码调制方案.由于将Turbo码和TCM编码调制技术相结合得到的Turbo TCM编码调制方案的带宽效率高,所以,在慢时变无线衰落信道中,自适应Turbo TCM编码调制的平均频谱效率也将很高.给出了该方案的工作原理、设计方法,并通过蒙特卡洛(Monte Carlo)仿真研究了该方案的性能.与现有编码调制方案相比,该方案具有频谱效率高、易于设计和实现的优点.     

Hybrid ARQ schemes employing coded modulation and sequencecombining

In this paper, we propose and analyze two hybrid automatic-repeat-request (ARQ) schemes employing bandwidth efficient coded modulation and coded sequence combining. In the first scheme, a trellis-coded modulation (TCM) is used to control channel noise; while in the second scheme a concatenated coded modulation is employed. The concatenated coded modulation is formed by cascading a Reed-Solomon (RS) outer code and a block coded modulation (BCM) inner code. In both schemes, the coded modulation decoder, by performing sequence combining and soft-decision maximum likelihood decoding, makes full use of the information available in all received sequences corresponding to a given information message. It is shown, by means of analysis as well as computer simulations, that both schemes are capable of providing high throughput efficiencies over a wide range of signal-to-noise ratios. The schemes are suitable for large file transfers over satellite communication links where high throughput and high reliability are required     

Block versus trellis: an introduction to coded modulation

Coded modulation has had a very significant impact on the communications scene in the decade or so since its introduction, finding practical applications from voice-band modems for telephone lines to deep-space communications. The paper introduces the principles of coded modulation and describes the two main schemes: block coded modulation (BCM) and trellis coded modulation (TCM). In particular it considers the argument between the proponents of BCM and TCM, and points out some pitfalls in the use of performance measures such as asymptotic coding gain for these schemes. It concludes that in terms of performance versus decoder complexity the schemes seem to be quite close, and the choice of the system designer may be determined by other factors     

Novel Trellis‐Coded Spatial Modulation over Generalized Rician Fading Channels

In this paper, a novel trellis‐coded spatial modulation (TCSM) design method is presented and analyzed. Inspired by the key idea of trellis‐coded modulation (TCM), the detailed analysis is firstly provided on the unequal error protection performance of spatial modulation constellation. Subsequently, the Ungerboeck set partitioning rule is proposed and applied to develop a general method to design the novel TCSM schemes. Different from the conventional TCSM approaches, the novel one based on the Ungerboeck set partitioning rule has similar properties as the classic TCM, which has simple but effective code design criteria. Moreover, the novel designed schemes are robust and adaptive to the generalized Rician fading channels, which outperform the traditional TCSM ones. For examples, the novel 4‐, 8‐, and 16‐state TCSM schemes are constructed by employing different transmit antennas and different modulation schemes in different channel conditions. Simulation results clearly demonstrate the advantages of the novel TCSM schemes over the conventional ones.     

Error probability for digital transmission over nonlinear channelswith application to TCM

The computation of upper and lower bounds to error probability in digital transmission over nonlinear channels with a finite memory is considered. By using orthogonal Volterra series, the authors derive a canonical representation for discrete nonlinear systems, based on a linear convolutional code and a memoryless mapper. This representation shows that finite-memory, discrete nonlinear systems can be analyzed in much the same way as TCM (trellis-coded modulation) schemes. In particular, TCM over nonlinear channels can be analyzed. A technique is derived that expresses an upper bound to error probability based on the computation of the transfer of a state diagram with N branches, and whose branch labels are matrices rather than scalars. Some examples of its application are given. In particular, error bounds are derived for nonlinear TCM schemes and for TCM schemes operating on nonlinear channels     

Joint source-coding, channel-coding and modulation schemes for AWGN and Rayleigh fading channels

Joint source-coding, channel-coding and modulation schemes based on variable length codes, inphase-quadrature phase interleaved trellis coded modulation (TCM) and turbo TCM (TTCM) schemes are proposed. A significant coding gain and a lower error floor are achieved without bandwidth expansion.     

Adaptive bit-interleaved coded modulation

Adaptive coded modulation is a powerful method for achieving a high spectral efficiency over fading channels. Previously proposed adaptive schemes have employed set-partitioned trellis-coded modulation (TCM) and have adapted the number of uncoded bits on a given symbol based on the corresponding channel estimate. However, these adaptive TCM schemes do not perform well in systems where channel estimates are unreliable, since uncoded bits are not protected from unexpected finding. In this paper, adaptive bit-interleaved coded modulation (BICM) is introduced. Adaptive BICM schemes remove the need for parallel branches in the trellis-even when adapting the constellation size, thus making these schemes robust to errors made in the estimation of the current channel fading value. This motivates the design of adaptive BICM schemes, which will lead to adaptive systems that can support users with higher mobility than those considered in previous work. In such systems, numerical results demonstrate that the proposed schemes achieve a moderate bandwidth efficiency gain over previously proposed adaptive schemes and conventional (nonadaptive) schemes of similar complexity     

The effects of time-delay spread on unequalized TCM in a portableradio environment

This paper studies the effects of time-delay spread on trellis-coded modulation (TCM) in portable radio channels, where equalization is not employed to mitigate frequency-selective fading. The average irreducible bit error rate (BER) of three different TCM schemes are analytically formulated first and then numerically evaluated by simulation. The results for a delay spread lower than 0.2 of the symbol period indicate that the performance of TCM schemes with interleaving/deinterleaving is much better than that of QPSK, and better TCM schemes for flat fading also give better performance under low delay spread. Analytical results indicate that a good TCM scheme in frequency-selective fading channels should have both a large Euclidean distance and a high degree of built-in time diversity. If higher time-delay spread is encountered, TCM does not have advantages over QPSK. We also compare TCM performance with and without diversity. It is found that diversity greatly improves the performance under low delay spread, while the diversity gain quickly diminishes as the RMS delay spread approaches 0.2 of the symbol period