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本文充分考虑了认知超宽带系统频谱构形的物理层实现难度,进而选择伪混沌脉冲位置调制(Pseudo-Chaotic Pulse Position Modulation,PCPPM)作为超宽带系统调制方式。分析了PCPPMUWB脉冲信号频谱特性,实验证明PCPPM-UWB脉冲信号的连续谱线部分具备类噪声特性可以与窄带系统共存,而离散谱线部分干扰强度大,无法与窄带系统共存。在此基础上提出了一种基于PCPPM的认知超宽带频谱构形方法,该方法通过改变PCPPM调制参数将离散谱线移出主用户频带范围,使主用户带宽内仅存在功率受限的连续谱部分,这样可以保证当主用户恢复传输时不会受到认知用户的强干扰,且认知用户也不会出现因切换频段而造成通信中断问题。
This paper fully considers the difficulty of realizing the physical layer of spectral configuration of cognitive ultra-wideband system, and chooses Pseudo-Chaotic Pulse Position Modulation (PCPPM) as ultra-wideband system modulation method. The spectral characteristics of the PCPPMUWB pulse signal are analyzed. The experiments show that the continuous spectral part of the PCPPM-UWB pulse signal has the noise-like characteristics coexisting with the narrowband system, while the discrete spectral line part has strong interference and can not coexist with the narrowband system. Based on this, a PCPPM-based cognitive ultra-wideband spectral configuration method is proposed, in which the discrete spectral lines are shifted out of the main user’s frequency range by changing the PCPPM modulation parameters, so that only the power limited continuous spectrum exists in the main user bandwidth This ensures that when the primary user resumes transmission, it will not be affected by the strong interference of the cognitive user and the cognitive user will not be interrupted by the frequency band switching.