Space-time Block Codes Based on Quasi-Orthogonal Designs

A new space-time block codes based on quasi-orthogonal designs are put forward. First the channel model is formulated. Then the connection between orthogonal /quasi-orthogonal designs and space-time block codes is explored. Finally we make simulations for the transmission of 4 bits/s/Hz and 6 bits/s/Hz using eight transmit antennas using the rate 3/4 quasi-orthogonal space-time block code and the rate 1/2 full-diversity orthogonal space-time block code. Simulation results show that full transmission rate is more important for very low signal noise ratio (SNR) and high bit error probability (BEP), while full diversity is more important for very high SNR and low BEP.

Linear Dispersion Orthogonal Space-Time Block Codes

A new architecture of space-time codes as a combination of orthogonal space-time block codes （OSTBC） and linear dispersion codes （LDC） is proposed in order to improve the bit error rate（BER） performance of OSTBC.The scheme proposed is named linear dispersion orthogonal space-time block codes （LDOSTBC）.In LDOSTBC scheme,firstly,the data is coded into LDC codewords.Then,the coded LDC substreams are coded into OSTBC codewords again.The decoding algorithm of LDOSTBC combines linear decoding of OSTBC and ML decoding or suboptimum detection algorithms of LDC.Compared with OSTBC scheme when the rate of LDC is MtR,the performance of LDOSTBC scheme can be improved without decreasing the data rate,where Mt is the number of transmit antennas and R is the spectral efficiency of the modulation constellation.If some rate penalty is allowed,when the rate of LDC is less than MtR the performance of LDOSTBC can be improved further.

A New Generalized Complex Orthogonal Space-Time Block Codes

Recent research challenges in the wireless communication include the usage of diversity and efficient coding to improve data transmission quality and spectral efficiency. Space diversity uses multiple transmitting and/or receiving antennas to create independent fading channels without penalty in bandwidth efficiency. Space-time block coding is an encoding scheme for communication over Rayleigh fading channels using multiple transmitting antennas. Space-time block codes from complex orthogonal designs exist only for two transmitting antennas. This paper generalizes a new complex orthogonal space-time block code for four transmitting antennas, whose decoding complexity is very low. Simulations show that the generalized complex orthogonal space-time block code has low bit error rate, full rate and possibly large diversity.

Analysis of Rate One Quasi-Orthogonal Space-Time Block Coding over Rayleigh Fading Channel

Full-rate is very important in any data transmission coding. For transmitting data at low bit rate than full-rate code, higher modulation scheme is required. But it is impossible to design full rate orthogonal designs with complex constellation for more than two transmit antennas. Only Alamouti code provides full-rate for two transmit antennas. In this paper, Bit Error Rate (BER) is calculated for Quasi-Orthogonal Space-time Block Coding (QOSTBC). Here we work with Rayleigh fading channel. We consider the codes which decodes pairs of symbols instead of simple separate decoding like Orthogonal Space-Time Block Coding. In Quasi-Orthogonal Space-time Block Code full-rate is achieved but full-diversity is sacrificed. Diversity is the most important techniques for providing reliable communication over fading channels. One of the diversity techniques that uses multiple transmit and/or receive antennas is space diversity. Multiple antenna technique provides a space diversity to struggle with the fading without necessarily sacrificing bandwidth resources, so the excellent solutions of removing the fading of the channel for broadband wireless communications is using space diversity. Then, with the constellation rotation of the symbol, rotated version of Quasi-Orthogonal Space-Time Block Code is generated. It provides full diversity. We simulate BER for QOSTBC, rotated QOSTBC, orthogonal STBC and for uncoded system. The simulation result shows that QOSTBC and rotated QOSTBC perform better than other systems. It shows that QOSTBC provides a full transmission rate but that rotated QOSTBC provides the full rate with the full diversity.

EXACT ERROR PROBABILITY OF ORTHOGONAL SPACE-TIME BLOCK CODES OVER FLAT FADING CHANNELS

Space time block coding is a modulation scheme recently discovered for the transmit an- tenna diversity to combat the effects of wireless fading channels. Using the equivalent Single-Input Single-Output (SISO) model, this paper presents closed-form expressions for the exact Symbol Error Rate (SER) and Bit Error Rate (BER) of Orthogonal Space-Time Block Codes (OSTBCs) with M-ary Phase-Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) over flat un- correlated Nakagami-m and Ricean fading channels.

Low complexity suboptimal decode algorithms for quasi- orthogonal space time block codes

Due to the high complexity of the pairwise decoding algorithm and the poor performance of zero forcing（ ZF） /minimum mean square error（ MMSE） decoding algorithm, two low-complexity suboptimal decoding algorithms, called pairwisequasi-ZF and pairwise-quasi-MMSE decoders, are proposed. First,two transmit signals are detected by the quasi-ZF or the quasiMMSE algorithm at the receiver. Then, the two detected signals as the decoding results are substituted into the two pairwise decoding algorithm expressions to detect the other two transmit signals. The bit error rate（ BER） performance of the proposed algorithms is compared with that of the current known decoding algorithms.Also, the number of calculations of ZF, MMSE, quasi-ZF and quasi-MMSE algorithms is compared with each other. Simulation results showthat the BER performance of the proposed algorithms is substantially improved in comparison to the quasi-ZF and quasiMMSE algorithms. The BER performance of the pairwise-quasiZF（ pairwise-quasi-MMSE） decoder is equivalent to the pairwiseZF（ pairwise-MMSE） decoder, while the computational complexity is significantly reduced.

OPTIMAL ANTENNA SUBSET SELECTION AND BLIND DETECTION APPROACH APPLIED TO ORTHOGONAL SPACE-TIME BLOCK CODING

An approach combining optimal antenna subset selection with blind detection scheme for Orthogonal Space-Time Block Coding (OSTBC) is proposed in this paper. The optimal antenna sub- set selection is taken into account at transmitter and/or receiver sides, which chooses the optimal an- tennas to increase the diversity order of OSTBC and improve further its performance. In order to en- hance the robustness of the detection used in the conventional OSTBC scheme, a blind detection scheme based on Independent Component Analysis (ICA) is exploited which can directly extract transmitted signals without channel estimation. Performance analysis shows that the proposed ap- proach can achieve the full diversity and the flexibility of system design by using the antenna selec-tion and the ICA based blind detection schemes.

Switching Between Antenna Subset Selection and Quasi-Orthogonal Space-Time Block Code in Presence of Correlation

We address the problem of adaptive modulation and coding scheme(AMCS) for a multi-input multioutput(MIMO) system in presence of time-varying transmitting correlation.Antenna subset selection and quasiorthogonal space-time block code(QOSTBC) have different error performances with different signal-to-noise ratios(SNRs) and in different spatial correlation scenarios.The error performance can be improved by selecting an appropriate transmission scheme to adapt to various channel conditions.The maximum distance criterion is the simplest and very effective algorithm for the antenna subset selection without needs of complex calculation and channel state information at transmitter(CSIT).The minimum error performance criteria and the simplified linear decision strategy are developed for constant transmission rate traffic to select the optimal transmission scheme.It can dramatically decrease algorithm complexity for obtaining error probability according to the known quantities comparing with using instant CSIT.Simulation results show that,remarkable performances including low SNR and weak spatial correlation at the expense of simple calculation and almost no bandwidth loss by adopting AMCS can be achieved.The proposed AMCS improves robustness of slowly varying spatial correlated channels.

Prove the Minimal Delay of Complex Orthogonal Space-Time Block Code by Hadamard Matrix

The complex orthogonal designs with maximal rates and minimal delays is an open problem for space-time block code. Maximal rate can effectively transmit symbols to the lonest distance in the space dimension ; and minimal delay is the least decoding delay in the time dimension. Many authors have observed that regarding the complex orthogonal designs for space-time block codes with the antennas n = 4k （ k ∈ N ）, its minimal delay is the same as that for n - 4k -1. However none was able to prove it. In this paper, we use the characteristics of Hadamard matrix to prove this property to fulfill this vacancy.

Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

Orthogonal space-time block codes （OSTBCs） are an efficient mean in order to exploit the diversity offered by the wireless multiple-input multiple-output （MIMO） channel. This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out （MISO） Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise, and derives exact expressions of the ergodic capacity and outage probability （capacity distribution） for such OSTBCs. Some numerical examples are given to illustrate the effect of co-channel interference on the ergodic and outage capacity of OSTBCs.

A CODE DESIGN CRITERIA FOR NOT FULLY CONNECTED CHANNEL

There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not the optimal. Based on the derivation of PEP expression for codes transmitted on parallel block fading channels, criteria of codes design for not fully connected channels are proposed and are compared with Tarokh's criteria for fully connected channel. New codes for such channels are provided by systematical and exhaustive search. Simulation results show that these codes offer better performance on parallel FDM channels than other known codes.

FOLMS-AMDCNet:an automatic recognition scheme for multiple-antenna OFDM systems

The existing recognition algorithms of space-time block code(STBC)for multi-antenna(MA)orthogonal frequencydivision multiplexing(OFDM)systems use feature extraction and hypothesis testing to identify the signal types in a complex communication environment.However,owing to the restrictions on the prior information and channel conditions,these existing algorithms cannot perform well under strong interference and noncooperative communication conditions.To overcome these defects,this study introduces deep learning into the STBCOFDM signal recognition field and proposes a recognition method based on the fourth-order lag moment spectrum(FOLMS)and attention-guided multi-scale dilated convolution network(AMDCNet).The fourth-order lag moment vectors of the received signals are calculated,and vectors are stitched to form two-dimensional FOLMS,which is used as the input of the deep learning-based model.Then,the multi-scale dilated convolution is used to extract the details of images at different scales,and a convolutional block attention module(CBAM)is introduced to construct the attention-guided multi-scale dilated convolution module(AMDCM)to make the network be more focused on the target area and obtian the multi-scale guided features.Finally,the concatenate fusion,residual block and fully-connected layers are applied to acquire the STBC-OFDM signal types.Simulation experiments show that the average recognition probability of the proposed method at−12 dB is higher than 98%.Compared with the existing algorithms,the recognition performance of the proposed method is significantly improved and has good adaptability to environments with strong disturbances.In addition,the proposed deep learning-based model can directly identify the pre-processed FOLMS samples without a priori information on channel and noise,which is more suitable for non-cooperative communication systems than the existing algorithms.

一种基于准正交空时码的低复杂度MIMO差分检测方法

针对可实现全速率传输的准正交空时码,提出了一种低复杂度的准正交MIMO差分检测方法.该方法在发射端对数据比特进行联合星座映射,构造准正交空时码进行差分编码;接收端采用最大似然准则对两组星座符号对(symbol pair)并行差分检测.本文提出的星座集合及联合星座映射方法简化了接收端检测算法,降低了检测计算复杂度.

旋转星座下匙孔信道的四元素准正交空时分组码研究

提出了一种基于匙孔信道的旋转四元素准正交空时分组码(QQOSTBC-CR,Constellation Rotation QuaternionQuasi-Orthogonal Space Time Block Code),该码可以通过极化天线进行发射和接收,设计出发射天线数为8的QOSTPBC-CR,并对N=8的情况进行成对译码,最后与匙孔信道下传统旋转准正交空时分组码(QOSTBC-CR,Constellation Rotation Quasi-OrthogonalSpace Time Block Code)、准正交空时分组码(QOSTBC,Quasi-Orthogonal Space Time Block Code)以及瑞利信道下QQOSTBC-CR进行了仿真比较。结果表明:对4个发射天线的情况,当BER=10^(-3)时,BPSK和QPSK调制下本文所提QQOSTBC-CR分别比QOSTBC-CR有4.5dB和7dB的增益,分别比瑞利信道下QQOSTBC-CR有-4dB和-3dB的增益。

基于预编码的全码率准正交空时分组码

针对传统八天线全码率准正交空时分组码解码复杂度高的问题,该文提出了两种基于预编码的传输方案。利用四天线正交码扩展得到新的八天线准正交码,结合两个反馈相位信息构成的预编码矩阵,使信道矩阵正交化,消除码间串扰,实现码元独立最大似然解码。发送端采用交织技术,进一步提高了性能,实现了双码元联合最大似然解码。和获得满分集增益的星座图旋转方案不同,预编码方案最大程度上减少了码间串扰,提高准正交码的性能。仿真结果表明,基于预编码的两种准正交码性能好于星座旋转准正交码,而且降低了解码复杂度。

基于四元素准正交设计的空时分组码

提出了一种基于四元素准正交设计的空时分组码,该种码满足准正交设计关系,可以通过极化天线进行满码率发射和接收.首先建立了信道模型,然后设计出发射天线数为4的四元素准正交空时分组码,采用快速最大似然译码算法进行译码,最后将其与天线数为4的传统准正交设计空时分组码分别进行了性能仿真.结果表明,所设计的四元素准正交设计空时分组码在不增加发射天线和接收天线的情况下,可以降低系统误码率,提高系统性能.分别采用BPSK,QPSK和8PSK,当SNR=10dB时,新码的误码率比准正交码分别降低0.5-1个数量级,而在SNR=15dB时,则分别降低约2个数量级.

旋转星座下极化准正交空时分组码及性能分析

设计了发射天线数分别为8和6、码率为3/4的极化准正交空时分组码,对星座图进行最佳角度旋转,接收机采用成对译码算法,并对未旋转—极化、旋转—极化、未旋转—传统、旋转—传统这4种准正交空时分组码进行了仿真比较。结果表明,在相同条件下,当采用双极化天线时,星座图旋转对系统误码率性能改善不明显;当采用单极化天线时,旋转对系统误码率性能改善明显。

基于随机旋转的准正交空时分组码研究

为了提高准正交空时分组码的性能,该文提出基于随机旋转的准正交空时分组码(Random-rotationQO-STBC)的发射分集方法。这种方法对每个输入信息符号序列进行随机旋转,使准正交空时分组码的符号间干扰(ISI)随机化。仿真结果表明,在4×1MIMOQPSK调制系统中,采用最大似然检测方法,当误码率为10-5时,新的发射方案比传统的两种准正交空时分组码误码性能有约4dB的增益;当误码率低于10-4时,RR-J码相比于ST-LCP码,仍表现出0.5–1dB增益;当SNR高于16dB时,RR-J与CFR具有几乎相同的误码性能。文章讨论了实际系统中随机旋转矩阵数受限情况下性能的损失,仿真结果显示当可用随机旋转矩阵数大于16时,对系统性能的影响可以忽略。

适于匙孔信道的准正交极化空时分组码及性能分析

构建了一种适于匙孔信道的满码率极化准正交空时分组码以改善其误比特率性能,采用快速最大似然译码算法进行译码,并与匙孔信道的传统准正交空时分组码、单中继瑞利信道和单中继匙孔信道的极化准正交空时分组码分别进行误比特率的仿真和比较.结果表明:在相同SNR条件下,本文构建的分组码比传统准正交分组码具有更低的误比特率;与两种单中继极化准正交空时分组码相比,在SNR较高情况下本文分组码具有更好的性能.

一种新的QO-GLSFTBC-OFDM技术

提出了一种可以使QOSTBC(Quasi-Orthogonal Space-Time Block Code)获得满分集增益的QO-GLSFTBC-OFDM(Group Layered Space-Frequency-Time Block Coded Orthogonal Frequency Division Multiplexing)技术,与基于星座图旋转的改进QOSTBC方法相比,本文提出的方法不扩大每个发射天线发送符号的星座图.从理论分析的结果可以看出,本文所提出的方法在保持QOSTBC满速率优点的前提下,可以同时获得满空间分集增益;而且编码和译码的过程都是基于线性处理的,计算简单.计算机仿真结果也证明了该方法的有效性.