一种基于矩阵旋转的正交空时分组码

Tarokh等人(1999)运用正交设计理论证明了当发射天线数大于2时,不存在可以获得最大分集增益和最大传输速率的复正交空时分组码。而以牺牲正交性和部分分集增益为代价来获得更高传输速率的非正交空时分组码又会使误码性能降低。该文通过对非正交空时分组码信道相关矩阵采用矩阵旋转的方法,提出了一种可以获得最大传输速率、部分分集增益以及接收端线性解码的正交空时分组码。仿真结果表明,该方案与已有典型的空时分组码相比,具有较好的误码性能。     

Super-quasi-orthogonal space-time trellis codes for four transmit antennas

We introduce a new family of space-time trellis codes that extends the powerful characteristics of super-orthogonal space-time trellis codes to four transmit antennas. We consider a family of quasi-orthogonal space-time block codes as building blocks in our new trellis codes. These codes combine set partitioning and a super set of quasi-orthogonal space-time block codes in a systematic way to provide full diversity and improved coding gain. The result is a powerful code that provides full rate, full diversity, and high coding gain. It is also possible to maintain a tradeoff between coding gain and rate. Simulation results demonstrate the good performance of our new super-quasi-orthogonal space-time trellis codes.     

Novel full diversity space time codes

A novel full diversity space-time trellis code, referred to as an assembled space-time trellis code (ASTTC), is presented in this letter. For this scheme, space-time trellis coded signals are first linearly transformed, and then the transformed signals are coded by using the Alamouti space-time block code. A new design criterion is proposed. It is shown that the ASTTCs can achieve not only the full diversity order but also a significant coding gain determined by the minimum weighted code distance (MWCD). Based on this design criterion, a new 4-state code is derived by a systematic code search. Simulation results show that the new ASTTC is superior by about 1.7 dB to the TSC (TarokhSeshadri-Calderbank) code at the frame error rate (FER) of 1.0e-2 over quasi-static fading channels.     

Performance evaluation of super-orthogonal space-time trellis codes using a moment generating function-based approach

A new class of space-time codes called super-orthogonal trellis codes was introduced that combine set-partitioning with a super set of orthogonal space-time block codes in such a way as to provide full diversity with increased rate and improved coding gain over previous space-time trellis code (STTC) constructions. Here, we extend the moment generating function-based method, which was previously applied to analyzing the performance of space-time block orthogonal and trellis codes, to the above-mentioned super-orthogonal codes. It is shown that the maximum-likelihood metric and expressions for the pairwise error probability previously developed for the Alamouti (1998) space-time block code combined with multidimensional trellis-coded modulation can be readily extended to the super-orthogonal case. As such, the evaluation of the pairwise error probability for the latter can be performed in a similar manner to that previously described with the specific results depending on the particular trellis code design.     

Super-orthogonal space-time trellis codes

We introduce a new class of space-time codes called super-orthogonal space-time trellis codes. These codes combine set partitioning and a super set of orthogonal space-time block codes in a systematic way to provide full diversity and improved coding gain over earlier space-time trellis code constructions. We also study the optimality of our set partitioning and provide coding gain analysis. Codes operating at different rates, up to the highest theoretically possible rate, for different number of states can be designed by using our optimal set partitioning. Super-orthogonal space-time trellis codes can provide a tradeoff between rate and coding gain. Simulation results show more than 2-dB improvements over the codes presented in the literature while providing a systematic design methodology.     

一种新的准正交空时分组码的设计

根据正交设计理论,当发送天线数大于2时,不存在可以获得完全分集增益和全速率的复正交空时分组码.对空时分组码采用准正交设计,能够保证数据以全速率传输,但是会使其误码性能降低.文章在对准正交空时分组码(QOSTBC)结构研究的基础上,提出了一种全速率的四发射天线准正交空时分组码,并给出了基于最大似然译码方法.仿真结果表明,文章方案与已有典型的Jafarkhani准正交空时分组码相比,在高信噪比时有更好的误码性能.     

Closed-loop quasi-orthogonal STBCs and their performance in multipath fading environments and when combined with turbo codes

Quasi-orthogonal space-time block codes (QO-STBCs) achieve full code rate at the expense of loss in diversity gain. We propose two feedback methods for QO-STBCs to achieve full diversity and full code rate. In the first method, signals radiated from various antennas are rotated by phasors according to feedback from the receiver, whereas the second method is based upon antenna weighting/selection. For high to moderate feedback error rates, it is demonstrated that the proposed methods outperform the quantized transmit beamformer. The performance improvement is also investigated for these closed-loop methods when the transmitted signal is error control coded.     

一种全速率准正交空时分组码

空时分组码是发射分集中的一项新技术。通常的空时分组码采用正交设计，虽可以提供全分集增益，却不能保证全速率传输，造成发射端数据的积压。改进的空时分组码采用准正交设计，能够保证数据以全速率传输，但是其性能在低信噪比时优于正交空时分组码，在高信噪比时反而不如前者。提出一种改进的基于准正交设计的空时分组码。通过仿真表明，在不增加译码复杂度的情况下，其性能不论在低信噪比还是高信噪比时都优于正交设计的空时分组码，从而改善了系统性能。     

An optimal two transmit antenna space-time code and its stacked extensions

A space-time code is proposed that exhibits the highest coding gain among competing full-rate full transmit diversity space-time codes for the two transmit and receive antenna coherent quasi-static fading channel. The proposed code is derived from a layered architecture with real rotation of quadrature amplitude modulation (QAM) information symbols in two dimensions. The existing codes of similar architecture concentrate on application of complex full modulation diversity rotations or asymmetric real rotations. An analytic evaluation illustrates the significant improvement in coding gain achieved with the proposed code. Moreover, the coding gain of the proposed code is independent of its rate. This implies that the proposed code achieves the optimal diversity-multiplexing tradeoff curve for the two transmit antenna system. A stacked extension of the proposed code offers a reduced complexity capacity optimal alternative to the full diversity codes for larger number of transmit antennas. Performance enhancement in several scenarios is verified through simulations.     

无线光通信中的空时编码研究进展(三)

空时编码利用多天线阵列提供的并行信道传输信息,可以在保证通信质量的前提下进一步提高信息传输速率。介绍了笔者在正交空时码、空时网格码、酉空时码、差分空时码、混合空时码等方面的工作。采用类脉冲位置调制定义了负数、共轭、求补等运算,将编码矩阵转化为一个用脉冲位置表示的实数矩阵。分析了不同发射天线/接收天线数目、大气湍流强度与系统误码率之间的关系。讨论了差分空时码、酉空时码在不同大气湍流条件下的误码率特性;将分层空时码和空时分组码相结合,对复用增益和分集增益进行合理的折中,提出了一种适合于IM/DD式光通信的混合空时编码方案。     

可快速迭代解码的非相干空时编码

提出了一种基于满分集准正交空时分组码构造非酉非相干空时码的方法,该编码能够最大限度地利用信道的相关时间来提高码率.根据代数分集的定义,证明了所构造的编码可获得满代数分集.为了能够充分利用编码的准正交结构简化解码,选用了基于期望最大化的迭代算法对所构造的编码进行解码,该算法能够极大地减小最优解码器的复杂度.仿真结果表明,迭代解码算法可快速收敛且其能够很好地对解码复杂度和误码性能进行折衷.     

A high-rate orthogonal space-time block code

We present a space-time block code from complex orthogonal designs for 5 transmit antennas, which can send 10 information symbols in a block of 15 channel uses and hence have rate 2/3. Simulation results show that this orthogonal space-time block code with rate 2/3 for five transmit antennas can achieve diversity gain over those orthogonal space-time block codes with higher rates for less number of transmit antennas.     

大规模MU-MIMO系统下的预编码技术研究

在大规模MU-MIMO系统中提出一种预编码技术,即特征波束形成结合空时分组编码.在发射端,利用大规模MI-MO形成正交波束,将空时分组码分布在这些波束上进行传输.而在接收端,空时分组码根据传统的译码算法解码.此技术能够同时获得分集增益和波束形成增益,还可以大大降低接收端的复杂度.在多用户系统中,它的性能都优于其他传统的编码方式.仿真结果也验证了该方法的有效性.     

A quasi-orthogonal space-time block code

It has been shown that a complex orthogonal design that provides full diversity and full transmission rate for a space-time block code is not possible for more than two antennas. Previous attempts have been concentrated in generalizing orthogonal designs which provide space-time block codes with full diversity and a high transmission rate. We design rate one codes which are quasi-orthogonal and provide partial diversity. The decoder of the proposed codes works with pairs of transmitted symbols instead of single symbols     

无线通信系统中的MIMO空时编码技术

在无线通信系统中,对优质、高效宽带服务的要求不断增加。空时编码（STC）的目的是利用多输入多输出（MIMO）天线系统,提高传输质量,降低误码率,并获得较高的编码增益和分集增益,提高系统容量和频谱利用率。较详细地介绍了MIMO无线通信中的三种空时编码方案：分层空时码、空时格形码、空时分组码,对这三种方案进行了性能分析以及比较。     

Optimal space-time coding under iterative processing

In this paper, we deal with the design of a full-rate space-time block coding (STBC) scheme optimized for linear iterative decoding over fast fading multiple-input multiple-output (MIMO) channel. A general and simple coding scheme called diagonal threaded space-time (DTST) code is presented for an arbitrary number of transmit and receive antennas. Theoretical analysis shows that DTST code associated with linear iterative decoding tends towards full diversity performance while providing maximum MIMO multiplexing gain. Simulation results confirm the ability of DTST to outperform the state-of-the-art STBC and conventional spatial data multiplexing schemes under iterative processing.     

A single-symbol-decodable space-time block code with full rate and low peak-to-average power ratio

Three desirable properties of a four-antenna spacetime block code are full rate, full diversity, and single-symbol decodability. Previously reported space-time codes that achieve all three properties do so at the expense of the peak-to-average power ratio (PAPR). A fourth desirable property of a space-time block code is that its PAPR be the same as that of the underlying quadrature-amplitude modulation alphabet. In this letter we introduce space-time codes for three and four transmit antennas that achieve all four properties; these codes use a diversity technique based on constellation stretching. Numerical results for quasistatic Rayleigh-fading channels show that, despite their low PAPR, the proposed codes are comparable in SNR performance to the best-performing single-symbol decodable space-time codes for three and four transmit antennas.     

全速率满分集准正交空时分组码的设计

在未来的第四代移动通信中,基于多输入多输出（MIMO）天线系统的空时编码技术是改善无线通信性能,提高带限系统数据传输速率的一种理想选择,但由于正交空时分组编码不能保证满分集和数据全速率传输,提出了一种利用星座图旋转可获得全速率满分集传输的旋转准正交空时分组码的设计方法。仿真结果表明,这种方法在不增加译码复杂度的情况下,其误比特率无论在低信噪比还是在高信噪比条件下都要优于已有的准正交空时分组码。     

MIMO CDMA系统中一种新的循环空时分组编译码方法

该文提出了MIMO CDMA系统中一种新的空时分组编译码方法,称为循环空时分组码(Cyclic Space-Time Block Code,C-STBC),它是将输入信息进行分组循环编码,然后对循环编码后的码字通过不同的天线分别采用不同的扩频码扩频后发射出去。这种CDMA系统下的循环空时分组码对任意的发射天线数都能达到满编码速率和满分集度,且其译码与传统的空时分组码一样简单。仿真结果验证了这种循环空时分组码优于传统的空时分组码。     

一种基于MIMO空时分集的HARQ方法及其性能分析

通常,MIMO利用降低空时编码效率的方法,在复用增益与分集增益乘积一定的约束条件下,实现二者折衷;该文则从系统设计的角度,通过分析VBLAST,HARQ,STBC内在的联系,构造一种新型的混合重传方法,实现编码与HARQ二者平滑对接,在保持空时码满的复用增益前提条件下,以HARQ时延换取信噪比的提升,额外引入分集增益。同时,该文对信道相关性、重传时间与空间分集之间的重要关系作了系统深入的理论分析。仿真结果表明,所提方法对不同信道环境下的系统性能均有较大的提升。