外文翻譯--mimo-ofdm軟件快速定義無線電系統(tǒng)的原型

1、外文文獻(xiàn)原文24中文 中文4840 4840字外文文獻(xiàn)原文： 外文文獻(xiàn)原文：Rapid MIMO-OFDM Software Defined RadioSystem PrototypingAmit Gupta, Antonio Forenza, and Robert W. Heath Jr.Wireless Networking and Communications GroupDepartment of Electrical and C

2、omputer Engineering, The University of Texas at Austin1 University Station C0803, Austin, TX 78712-0240 USAPhone: +1-512-232-2014, Fax: +1-512-471-6512{agupta, forenza, rheath}@ece.utexas.eduAbstract—Multiple input-multi

3、ple output (MIMO) is an attractive technology for future wireless systems. MIMO communication, enabled by the use of multiple transmit and multiple receive antennas, is known for its high spectral efficiency aswell as it

4、s robustness against fading and interference. Combining MIMO with orthogonal frequency division multiplexing (OFDM),it is possible to significantly reduce receiver complexity as OFDM greatly simplifies equalization at th

5、e receiver. MIMO-OFDM is currently being considered for a number of developing wireless standards; consequently, the study of MIMO-OFDM in realistic environments is of great importance. This paper describes an approach f

6、or prototyping a MIMO-OFDM system using a flexible software defined radio (SDR) system architecture in conjunction with commercially available hardware. An emphasis on software permits a focus on algorithm and system de

7、sign issues rather than implementation and hardware configuration. The penalty of this flexibility, however, is that the ease of use comes at the expense of overall throughput. To illustrate the benefits of the proposeda

8、rchitecture, applications to MIMO-OFDM system prototyping and preliminary MIMO channel measurements are presented. A detailed description of the hardware is provided along with downloadable software to reproduce the sy

9、stem. I. INTRODUCTIONMultiple-input multiple-output (MIMO) wireless systems use multiple transmit and multiple receive antennas to increase capacity and provide robustness to fading [1]. To obtain these benefits in broad

10、band channels with extensive frequency selectivity,MIMO communication links require complex space time equalizers. The complexity of MIMO systems can be reduced, however, through orthogonal frequency division multiplexin

11、g(OFDM). OFDM is an attractive digital modulation technique that permits greatly simplified equalization at the receiver. With OFDM, the modulated signal is effectively transmitted in parallel over N orthogonal frequency

12、 tones.This converts a wideband frequency selective channel into N narrowband flat fading channels. Currently OFDM is used in many wireless digital communication systems, such as the IEEE 802.11a/g [2], [3] standards for

13、 wireless local area networks(WLANs). MIMO-OFDM technology is in the process of being standardized by the IEEE Technical Group 802.11n[4] and 外文文獻(xiàn)原文26channel measurements in indoor environments. II. MIMO-OFDM IMPLEMENTAT

14、IONIn this section we review the MIMO-OFDM signal model and then describe our specific MIMO-OFDM system implementation.A. MIMO-OFDM Signal ModelIn a MIMO-OFDM system (see [8] and the references therein) MIMO space-time c

15、odes are combined with OFDM modulation at the transmitter while complicated space-time frequency processing is employed at the receiver. For simplicity of explanation, we consider spatial multiplexing as illustrated in F

16、ig. 1 though it will be apparent that other transmission techniques can be implemented in the proposed architecture.In a MIMO-OFDM system with MT transmit antennas and MR receive antennas, the sampled signal at the recei

17、ver (after the FFT and removing the cyclic prefix) of a spatial multiplexing MIMO system for OFDM symbol period n and tone k can be expressed by the following equation (assuming perfect linearity, timing, and synchroniza

18、tion.) [1](1) , , , , n k n k n k n k Y H S W ? ?The equalization in MIMO-OFDM systems may be enabled through different procedures such as zero-forcing equalizer,minimum mean-squared error equalizer, V-BLAST successive c

19、ancelling equalizer, sphere decoder, and maximum likelihood decoder (see [1] for an overview). In our prototype we currently implement the zero-forcing equalizer; the flexibility of the proposed architecture though allow

20、s us to prototype more sophisticated equalization strategies.B. System Implementation and SpecificationsThe first implementation features spatial multiplexing with two transmit and two receive antennas, as illustrated in

21、 Fig. 1.Other MIMO schemes are already available in the LabVIEW MIMO Toolkit [14], and we are planning to use this to implement other space-frequency codes in the future.The specifications of the system are listed in Tab

22、le I. In our MIMO-OFDM implementation, OFDM with 64 tones is employed over a 16MHz bandwidth. The cyclic prefix is 16 samples long. This corresponds to an OFDM symbol duration of 5μs, with a guard interval of 1μs and a d

23、ata portion of 4μs. We transmit our OFDM symbols in 200ms data packets.This 200ms was determined by our hardware as memory constraints at the receiver prevented longer acquisition periods. The system is equipped with an

24、adjustable carrier frequency. We chose to run our system at 2.4GHz, which is the carrier frequency used for WLANs [2], [3]. Various modulation schemes are possible (BPSK, QPSK, 16-QAM, 64-QAM) along with optional convolu

25、tional coding.Channel estimation is carried out by periodically transmitting an OFDM training symbol. The frequency at which training symbols are sent can be programmatically changed in the software and depends on the ex

26、pected variation of the channel. The estimation at the receiver is enabled by the pilot symbols, sent out over orthogonal tones across the transmit antennas. We then use a linear interpolation across the tones to estimat