共查询到20条相似文献,搜索用时 125 毫秒
1.
本文在设计多输入多输出系统时融合了分层空时结构和空时码的设计思想,在接收端联合采用了随机分层空时编码和分组线性星座预编码OFDM多载波发送方式;并在接收端采用了迭代接收机.仿真结果表明本文提出的方案能充分利用多输入多输出频率选择性信道提供的多径和空间分集度,同时保持了分层空时结构的高数据速率的特性. 相似文献
2.
3.
在第三代移动通信系统中,空时编码是抗多径衰落和提高系统容量的一种新技术,分层空时码(BLAST)被标准化为高速下行分组接入(HSDPA)的技术方案之一.本文对分层空时码的基本原理进行阐述,对其当前的发展进行分析,最后讨论了分层空时码在第三代通信系统中的应用,包括应用策略和技术方案等. 相似文献
4.
5.
6.
第三代移动通信中的空时编码技术 总被引:1,自引:0,他引:1
空时编码技术是一种有效提高无线通信系统容量的技术,在它的发展过程中产生了4种主要的技术方案:分层空时码(BLAST)、空时格码(STTC)、空时分组码(STBC)和酉空时码(USTC)。本文主要对这四种空时码的基本原理进行阐述,并对各种空时码类型的优缺点进行比较,最后讨论了空时码技术在第三代移动通信中的应用情况。 相似文献
7.
基于MIMO的垂直分层空时码检测算法 总被引:1,自引:0,他引:1
分层空时码(BLAST)是贝尔实验室提出的一种基于多入多出(MIMO)传输方式的空时码系统。本文着重研究了BLAST系统中一类垂直分层空时码的检测算法,依据信号模型,分析推导了基于迫零准则和最小均方误差准则的估计算法,并在此基础上采用了以上算法与判决反馈及最佳排序思想结合的方法,使系统的误码率性能得到了提高。最后通过仿真实验比较了各种算法的性能和特点,结果表明分层空时码用于无线通信具有极大优势。 相似文献
8.
9.
提出一种将贝尔实验室分层空时(BLAST)技术与RAKE接收机相结合的方案,介绍了该方案的算法原理,并与现有的频率选择性衰落信道下的BLAST方案进行了仿真对比.结果表明新方案在系统性能损失不大的情况下,极大地降低了系统复杂度. 相似文献
10.
11.
Huang H. Viswanathan H. Foschini G.J. 《Wireless Communications, IEEE Transactions on》2002,1(3):383-392
Providing wireless high-speed packet data services for Web browsing and streaming multimedia applications will be a key feature in future code-division multiple-access (CDMA) systems. We study down-link CDMA schemes for providing such services using multiple antennas at the transmitter and receiver. We propose a generalization of the point-to-point narrowband Bell Labs layered space-time (BLAST) system to a wideband multiple access system which simultaneously supports multiple users through code spreading. We discuss transmission options for achieving transmit diversity and spatial separation and introduce a generalization of the vertical BLAST detector for CDMA signals. Using link level simulations, we determine the bit-error rates versus signal-to-interference ratio of the various transmitter options. We then describe a novel technique for determining the system spectral efficiency (measured in bits per second per Hertz per cell sector) by incorporating the link level results with system level outage simulations. Using four antennas at the transmitter and eight antennas at each receiver, the system can support multiple receivers at 16 times the voice rate, resulting in a system spectral efficiency an order magnitude higher than a conventional single-antenna voice system 相似文献
12.
Howard Huang Harish Viswanathan Andrew Blanksby Mohamed A. Haleem 《The Journal of VLSI Signal Processing》2002,30(1-3):55-69
A High Data Rate (HDR) system has been proposed for providing downlink wireless packet service by using a channel-aware scheduling algorithm to transmit to users in a time-division multiplexed manner. In this paper, we propose using multiple antennas at the transmitter and/or at the receiver to improve performance of an HDR system. We consider the design tradeoffs between scheduling and multi-antenna transmission/detection strategies and investigate the average Shannon capacity throughput as a function of the number of antennas assuming ideal channel estimates and rate feedback. The highest capacities are achieved using multiple antennas at both the transmitter and receiver. For such systems, the best performance is achieved using a multi-input multi-output capacity-achieving transmission scheme such as BLAST (Bell Labs Layered Space-Time) in which the transmitted signal is coded in space and time, and the receive antennas are used to resolve the spatial interference. In the second part of the paper, we discuss practical transmitter and receiver architectures using BLAST for approaching the theoretical gains promised by the capacity analysis. Because the terminal receivers will be portable devices with limited computational and battery power, we perform a computational complexity analysis of the receiver and make high-level assessments on its feasibility. We conclude that the overall computational requirements are within the reach of current hardware technology. 相似文献
13.
14.
The Bell Labs layered space-time (BLAST) architecture is a simple and efficient multiantenna coding structure that can achieve high spectral efficiency. Many BLAST detectors require more receiver antennas than transmitter antennas. We propose two novel turbo-processing BLAST detectors that can operate in systems with fewer receiver antennas than transmitter antennas. Both detectors are based on the group-detection strategy. The first proposed detector, the reduced-dimension maximum a posteriori (RDMAP) detector uses a dynamically formed group for each bit decision, while the second proposed detector, the group maximum a posteriori (GMAP) uses a static grouping. For both detectors, a maximum a posteriori (MAP) decision is made using a group of transmitted symbols, and the remaining signal contribution is treated as interference. The interference is characterized as nonzero mean colored-noise source that is whitened before a decision is made. Both proposed detectors are generalizations of the MAP detector and the turbo-processing minimum mean-squared error (MMSE) detector in Sellathurai and Haykin, and Abe and Matsumoto. An uncoded bit-error rate analysis for an independent Rayleigh fading environment is also presented. Simulated results are presented which show that both the RDMAP and GMAP detectors have a performance improvement over the MMSE detector, especially in systems having an excess number of transmitter antennas. 相似文献
15.
In this paper, we propose a pre-Bell Laboratories layered space-time (BLAST)-decision-feedback equalization technique for the downlink of frequency-selective fading multiple-input multiple-output (MIMO) channels to combat multiple-access interference (MAI) and intersymbol interference (ISI). In our technique, we perform MIMO pre-equalization and prelayered space-time processing at the transmitter or base station, with a simplified receiver at the mobile station that requires only limited signal processing. An important application is in the downlink, so that a simplified mobile station can be constructed. An expression for the signal-to-noise ratio (SNR) and error probability based on the Gaussian approximation of the output noise term is derived. Performance is investigated by analysis and simulation results. In particular, it is demonstrated that the diversity order of this technique is higher than that of the MIMO orthogonal frequency-division multiplexing (OFDM) with vertical (V)-BLAST and MIMO OFDM with linear transmit preprocessing. It is also noticed that this technique performs better at high SNR values. 相似文献
16.
《Selected Areas in Communications, IEEE Journal on》2007,25(7):1284-1297
This paper presents power-efficient transmission schemes for the multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) block-fading channel under the assumption that the channel during each fading block is known perfectly at the receiver, but is unavailable at the transmitter. Based on the well-known vertical Bell Labs layered space-time (V-BLAST) architecture that employs independent encoding for each transmit antenna and successive decoding at the receiver, this paper presents a per-antenna-based power and rate feedback scheme, termed the "closed-loop" V- BLAST, for which the receiver jointly optimizes the power and rate assignments for all transmit antennas, and then returns them to the transmitter via a low-rate feedback channel. The power and rate optimization minimizes the total transmit power for support of an aggregate transmission rate during each fading block. Convex optimization techniques are used to design efficient algorithms for optimal power and rate allocation. The proposed algorithms are also modified to incorporate practical system constraints on feedback complexity and on modulation and coding. Furthermore, this paper shows that the per-antenna-based power and rate control can be readily modified to combine with the conventional linear MIMO transmit preceding technique as an efficient and capacity-approaching partial-channel-feedback scheme. Simulation results show that the closed-loop V-BLAST is able to approach closely the MIMO-OFDM channel capacity assuming availability of perfect channel knowledge at both the transmitter and the receiver. 相似文献
17.
In this letter, we study linear pre-equalization in conjunction with BLAST equalization. Linear pre-equalization is based on the assumption that the channel state information available at the transmitter is limited to the second order statistics of channel and noise (long term channel state information or LT-CSI). Through simulations, we compare different design criteria for the pre-equalizer and show the advantages of the considered structure with respect to BLAST. 相似文献
18.
Simeone O. Bar-Ness Y. Spagnolini U. 《Wireless Communications, IEEE Transactions on》2004,3(2):373-378
A transceiver structure for frequency-flat multiple-input multiple-output (MIMO) systems that comprises linear/nonlinear preequalization/equalization is optimized according to the minimum mean square error (MMSE) criterion under the assumption that only long-term channel state information (i.e., correlation matrices of fading channel and noise) is available at the transmitter. The structure generalizes different techniques known from the literature, such as BLAST, linear preequalization and equalization, and Tomlinson-Harashima precoding (THP). Simulations show that relevant benefits can be obtained by exploiting the long term channel state information at the transmitter in both dense multipath channels with relatively large correlation at the transmitter side and in sparse multipath channels. 相似文献
19.
Weidong Xiang Waters D. Pratt T.G. Barry J. Walkenhorst B. 《Communications Magazine, IEEE》2004,42(12):88-95
A three-transmitter three-receiver orthogonal frequency-division multiplexing Bell Laboratories layered space-time testbed is set up, which achieves a peak data rate of 281.25 Mb/s and a spectral efficiency of 14.4 b/Hz/s. The transmitter of the testbed consists of three signal generators transmitting three independent OFDM signals at 25 Msamples/s synchronously. Three synchronized receiving links are used, each of which includes an RF receiver, an analog-to-digital converter, a digital downconverter, and a PowerPC processor for baseband processing. The performance and complexity of three typical BLAST detection techniques (linear detection, ordered decision feedback detection, and partial decision detection) are evaluated and compared using the data from the experiments conducted in both line-of-sight and non-line-of-sight indoor environments. 相似文献
20.
《Vehicular Technology, IEEE Transactions on》1984,33(1):37-43
Transmitter diversity is a technique that is effective for mitigating signal transmission degradation caused by multipath fading which is one of the most serious problems in land mobile radio. A frequency-offset transmitter diversity is proposed for a land mobile radio system that employs minimum-shift keying (MSK) and two-bit differential detection. It is shown that high transmission efficiency can be obtained in comparison with the other frequency-offset transmitter diversity. In addition, the diversity effect on the bit error rate (BER) performance is equivalent to that of postdetection equal gain combining diversity. The BER performance improvement was confirmed by the experimental test results. 相似文献