广义加权分数傅里叶变换两分量组合抗衰落技术

Double-component combined anti-fading technique based on GWFRFT

摘要:

为了在不改变载波体制的情况下,提升传统单载波（Single Carrier,SC）和多载波系统（Multi-Carrier,MC）的抗衰落能力,本文利用广义混合载波（Generalized Hybrid Carrier,GHC）系统在信号设计方面的高灵活性,提出基于广义加权分数傅里叶变换（Generalized Weighted Fractional Fourier Transform, GWFRFT）的两分量组合抗衰落方案.针对SC系统,所提两分量方案包含时域和时域反转两个分量,可以有效提升系统抗时间选择性衰落的能力；针对MC系统,所提两分量方案由频域和频域反转两个分量组成,能够有效提升系统抗频率选择性衰落的能力.为了充分挖掘两分量组合信号的潜力,本文对这种信号形式获得性能优势的机理进行了分析.分析结果表明,两分量之间的功率分配和同一符号在两分量中所经历衰落的独立性是影响两分量信号性能的关键因素.鉴于此,本文提出两分量等功率设计和半码块反转方案,进一步优化了两分量组合信号的性能.在此基础上,本文给出两分量组合信号生成方法,并分析其实现复杂度和频谱特性.仿真结果表明,两分量组合方案可以在不占用额外时间和频谱资源的前提下,实现对传统SC和MC系统抗衰落性能的有效提升,而基于分量等功率分配和半码块反转的优化可以进一步增强这种性能提升的效果.

Abstract:

To improve the anti-fading ability of the classical single carrier system (SC) and multi-carrier system (MC) without changing the carrier scheme, a double-component combination anti-fading scheme based on generalized weighted fractional Fourier transform (GWFRFT) is proposed in this paper, taking the advantage of the high flexibility of the generalized hybrid carrier (GHC) system. As for the SC system, the proposed double-component scheme contains time domain component and time domain reverse component, which enhances the ability to resist time-selective fading; while as for the MC system, the scheme contains frequency domain component and frequency domain reverse component, which possesses higher anti-frequency-selective fading ability. To fully dig out the potential of double-component combined signal form, mechanism of the characteristic advantage is analyzed. Results show that the power allocation between two components and the fading independence of the same symbol in the two components are the key factors affecting the performance of the double-component combination signal. In view of this, equal power allocation scheme and half-block inversion scheme are proposed to further optimize the performance of the double-component combination signal. In that case, generation method of double-component combined signal is proposed and the implementation complexity as well as spectral characteristics are also analyzed. Simulation results illustrate the improvement on anti-fading ability of proposed scheme without occupying extra time and frequency resources, compared with that of classic single-carrier and multi-carrier system. In addition, equal power allocation scheme and half-block inversion scheme enable a further improvement on the anti-fading ability.