STC-MIMO-OFDM结合：瑞丽频率选择性衰落信道中的性能提升

4星 · 超过85%的资源需积分: 9 171 浏览量更新于2024-09-17 收藏 265KB PDF 举报

"本文探讨了在瑞丽频率选择性衰落信道中，OFDM(正交频分复用)与时空编码(MIMO)相结合的应用。通过利用旋转哈达玛矩阵或旋转离散傅立叶变换矩阵进行扩频，提出了一种新的STC-MIMO-BlockSpreadOFDM (STC-MIMO-BOFDM)系统。这种系统能够利用时间、频率、空间和调制的多维度分集，从而在频率选择性衰落信道中展现出比传统OFDM系统（无论是否采用STC）更优的误比特率性能。通过对阿拉莫图码的仿真验证了这一理论优势。" 正文：在现代无线通信系统中，OFDM因其对频率选择性衰落的抵抗能力而被广泛应用。然而，尽管OFDM本身具有良好的抗多径衰落特性，但在严重的瑞丽衰落信道下，其性能仍然受到限制。为了解决这个问题，研究者们提出了将OFDM与MIMO技术相结合的方法，以进一步提高系统的数据传输速率和可靠性。 STC（Space-Time Coding）是一种利用多个天线进行编码的技术，它可以在不增加带宽或发射功率的情况下提升无线通信系统的性能。MIMO（Multiple-Input Multiple-Output）系统通过使用多个发送和接收天线，能够实现空间分集和空间复用，从而显著提高信道容量和抗干扰能力。将STC应用于MIMO系统可以进一步增强这些优势。本文关注的是STC-MIMO-OFDM系统，特别是一种被称为STC-MIMO-BlockSpreadOFDM的新方法。这种方法的核心是使用单位ary扩频矩阵，比如旋转哈达玛矩阵或旋转离散傅立叶变换矩阵，来扩展OFDM系统的传输符号。这种扩频策略不仅增强了信号的频率域和时间域分集，还利用了MIMO系统的空间分集。 STC-MIMO-BOFDM系统在设计上考虑了四种不同维度的多样性：时间多样性，通过OFDM本身的子载波间隔和循环前缀来实现；频率多样性，由OFDM的子载波结构提供；空间多样性，由MIMO系统的多个天线提供；以及调制多样性，通过不同的调制方式（如QPSK、16QAM等）实现。这种多维度的多样性结合，使得系统在频率选择性瑞丽衰落信道中的性能大幅提升。通过模拟实验，研究者使用了著名的阿拉莫图码来验证STC-MIMO-BOFDM系统的性能。阿拉莫图码是一种高效的低密度奇偶校验码，能够提供良好的纠错性能。实验结果表明，与传统的OFDM系统相比，无论是采用STC还是不采用STC，STC-MIMO-BOFDM系统都能够在保持较低误比特率的同时，显著改善通信质量。 OFDM与MIMO的结合，特别是STC-MIMO-BOFDM系统，为频率选择性衰落信道下的无线通信提供了强大的解决方案。通过充分利用各种维度的多样性，这种技术有望在未来无线通信标准中发挥重要作用，提高通信系统的效率和可靠性。

STC-MIMO Block Spread OFDM in Frequency

Selective Rayleigh Fading Channels

Le Chung Tran, Xiaojing Huang, Eryk Dutkiewicz and Joe Chicharo

Wireless Technologies Laboratory (WTL)

Telecommunications & Information Technology Research Institute

Faculty of Informatics, University of Wollongong

Wollongong, NSW 2522, Australia

Email: {lct71,huang,eryk,chicharo}@uow.edu.au

Abstract— In this paper, we expand the idea of spreading the

transmitted symbols in OFDM systems by unitary spreading ma-

trices based on the rotated Hadamard or rotated Discrete Fourier

Transform (DFT) matrices proposed in the literature to apply

to Space-Time Coded Multiple-Input Multiple-Output OFDM

(STC-MIMO-OFDM) systems. We refer the resulting systems

to as STC-MIMO Block Spread OFDM (STC-MIMO-BOFDM)

systems. In the proposed systems, a multi-dimensional diversity,

including time, frequency, space and modulation diversities, can

be used, resulting in better bit error performance in frequency

selective Rayleigh fading channels compared to the conventional

OFDM systems with or without STCs. Simulations carried out

with the Alamouti code conﬁrm the advantage of the proposed

STC-MIMO-BOFDM systems.

I. INTRODUCTION

Orthogonal Frequency Division Multiplexing (OFDM) has

been intensively considered in the literature for transmitting

signals over frequency selective fading channels. The main

advantage of the OFDM technique compared to a single

carrier modulation is that it facilitates the use of high data

rates with a relatively low complexity receiver, which requires

only a Fast Fourier Transform (FFT) processor followed by

single tap equalizers across all subcarriers. OFDM systems

possess a diversity gain over single carrier systems since

the orthogonality of the subcarriers prohibits multipaths from

being combined across the channel at the symbol level.

The use of spreading matrices to mix the transmitted

symbols linearly across the subchannels has been considered

for single antenna wireless communications systems in the

literature, such as in [1], [2]. The main advantage of using

spreading matrices is that it allows us to achieve a diversity

over the frequency selective fading channels. The use of

unitary spreading matrices based on the rotated Hadamard or

rotated Discrete Fourier Transform (DFT) matrices to improve

the performance of single antenna OFDM systems was ﬁrstly

introduced by Bury et.al. [2] and further studied by McCloud

[3].

It is well known that the use of multiple transmit and/or

receive antennas can signiﬁcantly improve the capacity of

wireless communications systems. Such systems are called

Multiple Input Multiple Output (MIMO) systems. Space-Time

Codes (STCs) are the codes designed for the use in MIMO

systems. Space-Time Block Codes (STBCs) [4], [5], [6],

Space-Time Trellis Codes (STTCs) [7], Bell Lab Layered

Space-Time (BLAST) [8] are among various types of STCs.

The combination of MIMO systems using STCs with the

OFDM technique has received a fair amount of attention in

the literature, such as in [9], [10], [11], [12], [13]. However,

the combination of MIMO systems using STCs with the block

spread OFDM technique has not been considered yet. This

combination is expected to improve further the performance

of the whole system at the cost of slightly more complicated

transmitter and receiver structures.

In this paper, we expand the idea of Block Spread OFDM

(BOFDM) mentioned in [2], [3] to apply to the MIMO-OFDM

systems using STCs. We call the resultant technique STC-

MIMO-BOFDM to distinguish it from the normal MIMO-

OFDM without block spreading. It is noted that the term

“spreading” is inherited from [2] to express the modulation

alphabet expansion, rather than the bandwidth expansion as

the normal meaning of this term.

The novel contributions of this paper include 1) the ap-

plication of the block spreading technique to the conven-

tional STC-MIMO-OFDM systems to improve further the

error performance of the STC-MIMO-OFDM systems; 2) the

derivation of the more detailed Simple Maximum Likelihood

(SML) decoding method [14] for the proposed STC-MIMO-

BOFDM systems using the Alamouti code [4]; and 3) the

error performance comparison between the proposed STC-

MIMO-BOFDM systems and the conventional OFDM systems

(without STCs or block spreading), BOFDM systems (without

STCs) [3] and STC-MIMO-OFDM systems (without block

spreading) [14], [15].

The paper is organized as follows. In Section II, we derive

the baseband model of an STC-MIMO-BOFDM system. Sec-

tion III derives a detailed decoding algorithm, namely Simple

Maximum Likelihood (SML), which was originally derived in

[14], for a particular example of the Alamouti code. Simulation

results are given in Section IV, and the paper is concluded by

Section V.

下载后可阅读完整内容，剩余5页未读，立即下载

chengsiyuan121

粉丝: 0
资源: 3

STC-MIMO-OFDM结合：瑞丽频率选择性衰落信道中的性能提升

mimo.zip_MIMO-OFDM时域信道估计_mimo_mimo ofdm_选择性_选择性信道

频率选择性衰落信道中多用户 OFDM-DCSK 系统的功率分配

网格空时码在OFDM调制中的应用及构建频率选择性衰落信道研究

根据以下描述生成matlab代码：基于瑞利平坦衰落信道建立频率选择性衰落信道模型，输入功率时延谱和多普勒频率扩展，生成频率选择性衰落信道，并输入OFDM信号

基本 OFDM 码：对通过瑞利频率选择性衰落信道传输的 OFDM 信号进行理想的相干检测-matlab开发

EM的MIMO_OFDM.zip_MIMO-OFDM_mimo ofdm_mimo 信道估计_ofdm_信道估计 MIMO

SEFDM在频率选择性衰落信道上的信道均衡和数据检测

matlab调制解调 OFDM OTFS 16qam qpsk ldpc turbo在高斯白噪声，频率选择性衰落信道下的误比特

MIMO-OFDM.rar_MIMO-OFDM信道_MIMO信道_MIMO信道估计_OFDM信道_信道对比

最新资源