ITR: Space-Time Spreading and Coding

ITR：时空扩展和编码

• 批准号: 0082987
• 负责人: P. Vijay Kumar
• 金额: $ 47.47万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0082987&HistoricalAwards=false
• 关键词: ITR; Space; Time; Spreading; Coding; ITR; Space; Time; Spreading; Coding

PROJECT SUMMARYThe channel fading and co-channel interference present in a wireless radio propagation channel presents a harsh challenge to the radio design engineer. Diversity techniques commonly used to combat the channel include the use of interleaved coded modulation and multiple antennas at the receiver end. Lately there has been a great deal of interest in the use of multiple antennas at the transmitter end, i.e., in using transmit diversity. Researchers have shown that the capacity of multi-antenna systems significantly exceeds that of conventional single-antenna systems. Space-time codes attempt to realize the potential increase in capacity by distributing code symbols intelligently in space (across the different transmit antennas) and time. This topic has received a great deal of attention since the BLAST space-time system was proposed and demonstrated at Bell Labs. This is because, owing to the additional dimensionality obtain by exploiting space, a spectral efficiency of 40 bits per sec per Hz at realistic signal to noise ratios was demonstrated (i.e., 20 times the spectral efficiency achieved in current cellular systems). The importance of space-time methods in communication and information theory was recently recognized by the selection of the work by Tarokh, Seshadri and Calderbank for the 1999 IEEE Information Theory Paper Prize. The great majority of space-time coding research has been based on the following assumptions:Single-user link or time-division multiplexedComplex Gaussian channel gains (frequency at fading) from each transmit (Tx) antenna to each receive (Rx) antenna.Independent channels for each Tx-Rx antenna pair.Equal average energy in each Tx-Rx antenna channel.Time non-selective channels (quasi-static assumption)Based on these assumptions, effective design rules have been established by considering the probability of pairwise codeword error. These design rules aim to maximize the diversity and coding gains. The assumptions described above best represent a system with a dense, rich scattering environment sur-rounding the Tx and Rx antenna arrays and stationary or slowly moving receivers. This model is applicable, for example, to an indoor office environment. It may also be accurate for a pedestrian cellular user in a dense urban environment, depending on the base-station antenna location. However, space-time channel measurements and models suggest that in many cases of practical interest, the above assumption of independence of channel gains is not accurate. The lack of like-signal interference may also not be applicable to code-division multiple access (CDMA)systems since a well-utilized CDMA system is limited by such interference. Virtually all third-generation mobile radio standards are based on CDMA systems as are the most effective wireless LAN systems. In a CDMA system, the effects of signature sequence design must also be considered together with coding andmodulation.In this project, we have developed an expression for the pairwise error probability for a system model that is broadly applicable. Our model includes arbitrary correlation between Tx-Rx antenna channels, multiple CDMA users, and the potential for time variations in the channel gains. Based on this model we propose to develop design rules for space-time spreading and coding for CDMA systems. Our goal is to develop rules that are applicable to a variety of applications (i.e., mobile users and dense scattering, or fixed-point systemsout of the scatter) and/or which are robust to uncertainties in the channel model.We propose to generalize the methods of space-time coding so that the approach may be used in CDMA systems and/or systems without rich scattering environments. Research directions include rules for spacetime spreading and code design, investigation of receiver structures and channel estimation/tracking, code design for simplified decoding and modified design rules for non-Euclidean distance receivers. This study will be conducted under different channel model assumptions and presumed knowledge at the receiver and transmitter of channel knowledge.

项目总结无线无线电传播频道中存在的通道褪色和共沟通干扰对无线电设计工程师提出了严厉的挑战。通常用于对抗通道的多样性技术包括在接收器端使用交织的编码调制和多个天线。最近，在发射器端的多个天线（即使用传输多样性）中使用多个天线引起了极大的兴趣。 研究人员已经表明，多腹腔系统的能力大大超过了常规的单烷基系统的能力。时空代码试图通过在空间（跨不同的传输天线）和时间智能分配代码符号来实现能力的潜在增加。 自从贝尔实验室提出并证明了爆炸时空系统以来，这个主题引起了很多关注。这是因为，由于通过利用空间获得额外的维度，在现实信号与噪声比时，每秒钟40位的光谱效率（即，在当前细胞系统中达到的光谱效率是20倍）。最近，通过Tarokh，Seshadri和Calderbank选择的1999年IEEE信息信息论纸张奖的作品的选择最近认可了时空方法在通信和信息理论中的重要性。 大多数时空编码研究大多数是基于以下假设：从每个传输（TX）天线到每个接收（rx）天线的单用户链接或时间划分的多重复合元素高斯通道的增长（频率），每种tx-rx天线对tx-rx antenna平均频率ne quaS quans in quaS quase ne quas antenna ne ne ne thenna nimenta cannels in quas ne n.na thenna quantenna。假设）基于这些假设，通过考虑成对码字误差的概率来确定有效的设计规则。这些设计规则旨在最大程度地提高多样性和编码增长。 上面描述的假设最好代表一个具有密集，丰富的散射环境的系统，该系统将TX和RX天线阵列以及固定或缓慢移动的接收器进行调整。该模型适用于室内办公环境。根据基数天线位置，在密集的城市环境中，行人的蜂窝使用者也可能是准确的。但是，时空通道的测量和模型表明，在许多实践意义的情况下，上述对通道增益独立性的假设不是准确的。 由于利用良好的CDMA系统受到这种干扰的限制，因此缺乏类似的干扰也可能不适用于代码分区多访问（CDMA）系统。几乎所有第三代移动无线电标准都基于CDMA系统，以及最有效的无线LAN系统。在CDMA系统中，还必须将签名序列设计的效果与编码和模块一起考虑。在此项目中，我们为系统模型的成对误差概率开发了一种表达式，该模型广泛适用。我们的模型包括TX-RX天线通道，多个CDMA用户之间的任意相关性，以及通道增加的时间变化的潜力。基于此模型，我们建议为CDMA系统的时空扩展和编码制定设计规则。我们的目标是制定适用于各种应用程序的规则（即移动用户和密集的散射，或散布的固定点系统）和/或在频道模型中不确定性可靠的规则。我们建议在没有丰富散射环境的CDMA系统和/或系统中使用该方法，以推广该方法的方法。研究方向包括时空扩展和代码设计的规则，接收器结构的调查以及渠道估计/跟踪，用于简化解码的代码设计以及针对非欧巴文距离接收器的修改设计规则。这项研究将以不同的通道模型假设和渠道知识的接收器和发射器的假定知识进行。