基于时空码和数联网技术的新型“可信数据空间”体系构想

梳理回顾欧盟“国际数据空间”和我国“可信数据空间”的发展由来,针对当前“可信数据空间”存在的制度和技术层面的瓶颈问题,引入一个新的“时空码+数联网”底层技术框架,在此基础上较为系统地提出新型“可信数据空间”的概念内涵、系统架构、功能视图以及有特色的融合底座等体系化设计。其主要创新体现在可信体系与实现路径、技术框架与系统架构、平台定位与生态培育等层面。并建议以新型“可信数据空间”作为我国数据流通基础设施建设的关键技术路线,协同开展技术攻关,加快试点验证示范。

基于自适应时空码书的粒子滤波多目标跟踪

提出一种基于自适应时空码书检测模型的粒子滤波多目标跟踪算法。使用时空码书模型进行前景背景分割,检测出前景目标,在该模型上加入目标自适应过程。将自适应时空码书检测的结果作为粒子滤波跟踪算法的初始目标状态,通过关联算法和粒子滤波实现多目标跟踪。自适应时空码书模型能明显降低对前景目标的误检率,抑制噪声干扰。实验结果表明,该算法能够在有干扰的复杂背景下实现对运动多目标的快速捕获,并有效提高跟踪的可靠性和精度。

一种新的快衰落信道下的差分Unitary时空编码调制方法

该文提出了一种新的基于循环对角群码的差分Unitary时空编码调制方法,这种新方法通过改变发送符号的顺序来降低快衰落信道时变对解码造成的影响,从而提高在快衰落信道下的性能。这种性能的提高是以处理时延和额外能量开销的增加为代价的,在实际应用中需要在这两者之间寻求平衡,处理时延越大,额外的能量开销就越小,反之亦然。与传统的差分Unitary时空编码调制方法比较,理论分析和matlab做的Monte Carlo仿真结果表明, 在快衰落信道下,提出的差分Unitary时空编码调制方法可获得明显的性能增益,能够显著降低系统的成对差错概率和误比特率。

Scalable transcoding for video transmission over space-time OFDM systems

A new scheme combining a scalable transcoder with space time block codes （STBC） for an orthogonal frequency division multiplexing （OFDM） system is proposed for robust video transmission in dispersive fading channels. The target application for such a scalable transcoder is to provide successful access to the pre-encoded high quality video MPEG-2 from mobile wireless terminals. In the scalable transcoder, besides outputting the MPEG-4 fine granular scalability （FGS） bitstream, both the size of video frames and the bit rate are reduced. And an array processing algorithm of layer interference suppression is used at the receiver which makes the system structure provide different levels of protection to different layers. Furthermore, by considering the important level of scalable bitstream, the different bitstreams can be given different level protection by the system structure and channel coding. With the proposed system, the concurrent large diversity gain characteristic of STBC and alleviation of the frequency-selective fading effect of OFDM can be achieved. The simulation results show that the proposed schemes integrating scalable transcoding can provide a basic quality of video transmission and outperform the conventional single layer transcoding transmitted under the random and bursty error channel conditions.

多天线的发送分集系统中多用户分集的研究

研究了如何通过选择发送天线和天线组合来提高整个多用户多天线系统的性能。本文分别讨论了STOBC、选择式发送分集、相位加权等各种发送信号结构下系统的调度性能。和其它发送信号结构相比,STOBC对于调度性能有着很大危害。信道反馈信息越多,调度性能就越好。不同的发送天线选择和组合策略得到不同的性能。本文讨论了三种选择策略:max-max, max-sum和max-min。max-max的调度性能优于其它两种策略。因此,发送信号的结构和选择策略都严重影响着多用户分集。

Performance analysis of space-time transmit diversity techniques for multi-antenna WCDMA systems

Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.

Design of super-orthogonal space-time trellis codes based on trace criterion

A design of super-orthogonal space-time trellis codes （SOSTTCs） based on the trace criterion （TC） is proposed for improving the design of SOSTTCs. The shortcomings of the rank and determinant criteria based design and the advantages of the TC-based design are analyzed. The optimization principle of four factors is presented, which includes the space-time block coding （STBC） scheme, set partitioning, trellis structure, and the assignment of signal subsets and STBC schemes in the trellis. According to this principle, systematical and handcrafted design steps are given in detail. By constellation expansion, the code performance can be further improved. The code design results are given, and the new codes outperform others in the simulation.

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.

Spatial channel pairing-based maximum ratio combining algorithm for cooperative relay networks

To improve the reliable performance of information transmission in cooperative relay networks, the scheme of the max-rate spatial channel pairing （SCP） based on maximum ratio combining （MRC） is proposed. The scheme includes three steps： channel phase cancellation, MRC, and SCP. Eventually, the solution of the scheme is modeled as convex optimization. The objective function of the optimization problem is to maximize the transmission rate and the optimization variable is the strategy of pairing between the uplink spatial sub-channels of each user and the corresponding downlink spatial ones. The theorem of the arrangement inequalities is adopted to obtain the approximate closed-form solution of the optimal pairing for this convex optimization. Simulation results demonstrate that compared to the existing distributed space-time block coding and coherent combined schemes without SCP, the proposed max-rate SCP plus MRC algorithm achieves appreciable improvements in symbol error rate in medium and high signal-to-noise ratio regimes. The achievable performance gain is due to the use of maxrate SCP.

Performance of STBC-MC-CDMA system based on complex wavelet packet and turbo coding

On the basis of analyzing the principle of the space-time coding technique and the multi-carrier code division multiple access （MC-CDMA） technique, adopting the turbo codes as channel coding and the optimized complex wavelet packet as multi-carrier modulation, a novel space-time block coded the MC-CDMA system based on complex wavelet packet and turbo coding is proposed, and the system bit error rate （BER） performance in the Rayleigh fading channel is investigated. The system can make full use of space-time block codes＇ transmit diversity and turbo codes＇ good ability against fading channel to improve the BER performance significantly, and it can also avoid the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix （CP） by utilizing superior characteristics of the optimized complex wavelet packet. Simulation results show that the proposed space-time block coded MC-CDMA system based on the complex wavelet packet performs better than the conventional space-time block coded MC-CDMA （STBC-MC-CDMA） system, and slightly outperforms the STBC-MC-CDMA with CP. Moreover, the application of the space-time block coding technique concatenated with turbo codes strengthens the system ability to combat various interferences in fading channel further.

Method of combining space-time block coding with adaptive beamforming

A method of space-time block coding （STBC） system based on adaptive beamforming of cyclostationarity signal algorithm is proposed.The method uses cyclostationarity of signals to achieve adaptive beamforming,then constructs a pair of low correlated transmit beams based on beamform estimation of multiple component signals of uplink.Using these two selected transmit beams,signals encoded by STBC are transmitted to achieve diversity gain and beamforming gain at the same time,and increase the signal to noise ratio （SNR） of downlink.With simple computation and fast convergence performance,the proposed scheme is applicable for time division multiple access （TDMA） wireless communication operated in a complex interference environment.Simulation results show that the proposed scheme has better performance than conventional STBC,and can obtain a gain of about 5 dB when the bit error ratio （BER） is 10-4.

Performance Comparison of Space-Time Trellis Codes and Space-Time Transmit Diversity under the Same Bandwidth Efficiency

Space time coding can provide high data rate and performance gain for wireless communication system. Performance comparison of space time trellis codes and space time transmit diversity is carried out under the same bandwidth efficiency in this paper. We also propose some optimum low rate space time trellis codes in quasi static Rayleigh fading chan￣nel. Performance analysis and simulation show that the low rate space time trellis codes outperform space time transmit diversity at the same bandwidth efficiency, and are more suitable for the power limited wireless communication system which has no strict requirement on bandwidth efficiency.

An improved linear dispersion codes transmission scheme based on OSIC detection

Linear dispersion codes (LDCs) were originally designed based on maximum likelihood detection. They do not have good performance when using ordered successive interference cancellation (OSIC) detection. In this paper,we propose a new improved linear dispersion codes transmission scheme to combat performance loss of original LDCs when using OSIC detection. We introduce an interleaver to each data substream transmitted over different antennas after LDCs encoder. Furthermore,a new computer search criterion for a linear transformation matrix is also proposed. New search criterion is to minimize the symbol error rate based on OSIC detection. Computer simulations show that the performance of proposed LDCs transmission scheme is better than the original LDCs.

AN IMPROVED SOVA-BASED DECODING SCHEME FOR TURBO-STCM

Parallel concatenated spa ce time trellis code modulation, called Turbo STCM, can efficiently increase the coding gains of the space time codes. However, the complexity of the iterat iv e decoding restricts its application. This paper introduces a lower complex deco ding algorithm based on soft output Viterbi algorithm (SOVA) for Turbo STCM. S imulational results show that the new SOVA algorithm for the Turbo STCM outperf orms the original space time trellis code (STTC) by 4~6 dB. At the same time, compared with the Max Log MAP (maximum a posteriori) algorithm, the new scheme requires a lower complexity and approaches the performance of Turbo STCM decod ing w ith Max Log MAP.

A VERTICAL LAYERED SPACE-TIME CODE AND ITS CLOSED-FORM BLIND SYMBOL DETECTION

Vertical layered space-time codes have demonstrated the enormous potential to accommodate rapid flow data. Thus far, vertical layered space-time codes assumed that perfect estimates of current channel fading conditions are available at the receiver. However, increasing the number of transmit antennas increases the required training interval and reduces the available time in which data may be transmitted before the fading coefficients change. In this paper, a vertical layered space-time code is proposed. By applying the subspace method to the layered space-time code, the symbols can be detected without training symbols and channel estimates at the transmitter or the receiver. Monte Carlo simulations show that performance can approach that of the detection method with the knowledge of the channel.

LDPC based time-frequency double differential space-time coding for multi-antenna OFDM systems

Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differential space-time (DDST) coding is of special interest because it is applicable to continuous fast time-varying channels. However, it is less effective in fre- quency-selective fading channels. This paper’s authors derived a novel time-frequency double differential space-time (TF-DDST) coding scheme for multi-antenna orthogonal frequency division multiplexing (OFDM) systems in a time-varying fre- quency-selective fading environment, where double differential space-time coding is introduced into both time domain and fre- quency domain. Our proposed TF-DDST-OFDM system has a low-complexity non-coherent decoding scheme and is robust for time- and frequency-selective Rayleigh fading. In this paper, we also propose the use of state-of-the-art low-density parity-check (LDPC) code in serial concatenation with our TF-DDST scheme as a channel code. Simulations revealed that the LDPC based TF-DDST OFDM system has low decoding complexity and relatively better performance.

LINEAR-DISPERSION DIVISION MULTIPLE-ACCESS FOR MIMO SYSTEMS

Comprehensive study on novel Linear-Dispersion Division Multiple-Access(LDDMA) for multi-user uplink Multiple-Input Multiple-Output(MIMO)systems is proposed.In the new multi-plexing scheme,each user’s information symbol is dispersed by a User-Specific Matrix(USM)both inspace and time domain and linearly combined at base-station side.And a simple random search al-gorithm,based on capacity maximization criteria,is developed to generate a bank of USMs.Simulationresults are presented to demonstrate the advantages of LDDMA.When the Bit Error Rate(BER)reaches 10–3,the performance gains are 3dB and 5dB,compared with Time-Division Linear DispersionCodes(TD-LDC)and BLAST,respectively.

A Cryptographic Scheme Based on Spatiotemporal Chaos of Coupled Map Lattices

We propose a cryptographic scheme based on spatiotemporal chaos of coupled map lattices （CIVIL） ,which is based on one-time pad. The structure of the cryptosystem determines that the progress in decryption implies the progress in exploring the dynamical behavior of spatiotemporal chaos in CML. A part of the initial condition of CML is used as a secret key, and the recovery of the secret key by exhaustive search is impossible due to the sensitivity to the initial condition in spatiotemporal chaos system. Specially the software implementation of the scheme is easy.

Space-time spreading and space-time coding for correlated frequency-selective channel in the presence of interference

The space-time spreading （SIS）, superimposed training sequences and space-time coding （STC） are adopted to obtain a closed-form of average error probability upper bound and maximum likelihood esti- mation expression for multiple input and multiple output （MIMO） correlated frequency-selective channel in the presence of interference （colored interference）. Moreover, the correlation at both ends of the wire- less link that can be incorporated equivalently into correlation at the transmit end is derived. Finally, the mean square error （MSE） of the maximum likelihood estimate is also derived.

A HIGH RESOLUTION WIDE SWATH SAR METHOD BASED ON INTRA-PULSE NULL STEERING AND MIMO

High Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) often suffers from low Signal-to-Noise Ratio (SNR) due to small transmitting antenna, especially in phased array antenna systems. Digital Beam Forming (DBF) based on Single Input and Multiple Output (SIMO) achieves receiving array gain at the cost of increasing data rate. This letter proposes a new HRWS SAR method, which employs intra-pulse null steering to get receiving gain in elevation and decrease the data rate, and Multiple Input and Multiple Output (MIMO) using Space-Time Block Coding (STBC) in azimuth to get transmitting gain and receiving array gain simultaneously. The feasibility is verified by deduction and simulations.