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A simplified approach to multi-carrier modulation.

机译:一种简化的多载波调制方法。

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摘要

There is a significant demand for a decrease in the size, weight and power (SWaP) associated with wireless systems. In recent years, multiple-input, multiple-output (MIMO) wireless systems have received considerable attention due to the high data rates they provide. Orthogonal frequency division multiplexing (OFDM), a digital multi-carrier modulation technique, is well suited to be used in MIMO systems as it provides the ability to operate in frequency-selective channel environments. When OFDM is combined with the capacity increase provided by MIMO systems, the result is a very successful communication system. In this research, a reduced-complexity MIMO OFDM system is advanced. The proposed system is multiplier-less and thus requires a simpler digital hardware implementation. As a result, the chip area, power consumption and cost associated with the MIMO OFDM system can be significantly reduced.The reduction in complexity is obtained via modification to conventional Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) algorithms necessary to implement OFDM multi-carrier modulation. System computational complexity is reduced by quantizing what are known as "twiddle factors" in traditional FFT algorithms such as the Radix-2 and Radix-4. The quantization allows for all multiplications to be done with a value of one, negative one, zero or a power of two. Ensuring that all multiplications are performed with any of the aforementioned values results in a transform where all multiplications are considered trivial. Replacing standard multiplications with trivial multiplications significantly reduces system computational complexity. As an example, the complexity associated with the implementation of the rounded FFT as compared to a conventional Radix-4 FFT is reduced by 47% when numerical values are represented with 16 bits. Depending on the application, different quantization levels can be utilized in order to obtain the necessary performance characteristics. As the number of quantization levels grows, the system capability increasingly approaches the performance of a system that uses the conventional transforms. When applied to MIMO OFDM systems, the computational savings are significant as the combination of the IFFT and FFT algorithms are implemented for every spatial stream (i.e. antenna). As such, the simplified approach provides a system that is a lower-cost, practical alternative to the MIMO OFDM systems used today.
机译:迫切需要减小与无线系统相关的尺寸,重量和功率(SWaP)。近年来,多输入多输出(MIMO)无线系统由于其提供的高数据速率而备受关注。正交频分复用(OFDM)是一种数字多载波调制技术,非常适合在MIMO系统中使用,因为它提供了在频率选择性信道环境中运行的能力。当OFDM与MIMO系统提供的容量增加相结合时,其结果就是非常成功的通信系统。在这项研究中,提出了一种降低复杂度的MIMO OFDM系统。所提出的系统是无乘法器的,因此需要更简单的数字硬件实现。结果,与MIMO OFDM系统相关的芯片面积,功耗和成本可以大大降低。通过修改传统的快速傅里叶变换(FFT)和快速傅里叶逆变换(IFFT)算法,可以降低复杂度实现OFDM多载波调制。通过量化传统FFT算法(例如Radix-2和Radix-4)中所谓的“旋转因子”,降低了系统计算复杂度。量化允许所有乘法以值1,负1,零或2的幂进行。确保使用任何上述值执行所有乘法都会导致转换,其中所有乘法都被认为是微不足道的。用普通乘法代替标准乘法可以显着降低系统计算复杂度。例如,当数值用16位表示时,与传统的Radix-4 FFT相比,与舍入FFT的实现相关的复杂性降低了47%。根据应用,可以利用不同的量化水平以获得必要的性能特征。随着量化级数量的增加,系统能力越来越接近使用常规变换的系统的性能。当将其应用于MIMO OFDM系统时,由于为每个空间流(即天线)实现了IFFT和FFT算法的组合,因此可节省大量计算量。这样,简化的方法提供了一种系统,该系统是当今使用的MIMO OFDM系统的低成本,实用替代方案。

著录项

  • 作者

    Marcum, Andrew C.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 M.S.E.
  • 年度 2010
  • 页码 98 p.
  • 总页数 98
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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