移动物联网通信中的UFMC调制波形优化设计

Optimal Design of UFMC Modulation Waveform in Mobile Internet of Things Communication

  • 摘要: 移动物联网(Internet of Things, IoT)通信是6G的关键技术之一,面对多变的地面基站环境,无人机(Unmanned Aerial Vehicle, UAV)辅助通信被认为是物联网通信的重要组成部分,已受到广泛关注。通用滤波器多载波(Universal Filtered Multi-carrier, UFMC)作为一种新型非正交多载波调制技术,继承了正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)的优势,主要应用在短数据包突发通信场景中,被认为适用于下一代无线物联网通信。但是,在无人机的高速移动环境下,通信信号会遭受显著的多普勒频移影响,产生严重的载波间干扰(Inter Carrier Interference, ICI),导致UFMC系统性能的显著下降。为了缓解ICI问题,本文首先理论分析、推导了存在多普勒频移时UFMC系统的信干噪比(Signal to Interference plus Noise Ratio, SINR)。根据SINR分析,可见将UFMC波形滤波器通带波动优化调控的足够小以及加快过渡带衰减有利于提升系统抗ICI能力。因此,本文提出了基于波形滤波器优化设计的干扰抑制方法,构建了符合UFMC通信需求的波形滤波器最优化设计数学模型,该模型可以有效地调控波形滤波器的通带波动,通过遍历搜索可求解得到使系统误符号率(Symbol Error Rate, SER)相对最优的波形滤波器。在考虑多普勒频移的系统仿真中,SER对比结果表明:与采用传统波形滤波器的UFMC系统相比,本文根据约束最小最大(Constraint Minimax, CMM)准则遍历搜索设计的波形滤波器可以有效地抑制系统ICI从而改善SER。这为未来移动物联网通信系统的波形设计提供了参考。

     

    Abstract: ‍ ‍Mobile Internet of Things (IoT) communication is a key 6G technology. Because of the variety of terrestrial base station environments, unmanned aerial vehicle (UAV)-assisted communication is considered an important part of IoT communication, and has received widespread attention. Universal filtered multi-carrier (UFMC), as a new non-orthogonal multi-carrier modulation technology, inherits the advantages of orthogonal frequency division multiplexing and is mainly used in short packet burst communication scenarios. It is considered suitable for next-generation wireless IoT communications. However, in the high-speed moving environment of UAVs, communication signals suffer from a significant Doppler frequency shift, resulting in severe inter-carrier interference (ICI) and degradation in system performance. To alleviate the ICI problem, this study theoretically analyzed and derived the signal to interference plus noise ratio (SINR) of a UFMC system in the presence of Doppler frequency shift. This SINR analysis showed that the ICI resistance of the system could be improved by optimally regulating the passband fluctuation of the UFMC waveform filter, to facilitate its reduction, and by accelerating the transition band attenuation. A mathematical model was constructed for the optimal design of waveform filters to meet UFMC communication requirements, and an interference suppression method based on these optimal waveform filters was constructed. This model could effectively regulate the passband fluctuation of the waveform filter. Traversal search provided waveform filters that enabled a relatively optimal system error rate (SER). In a system simulation considering a Doppler frequency shift, the SER comparison results showed that the waveform filter designed according to the constraint minimax criterion could effectively suppress the system ICI and improve the SER compared with a UFMC system employing the traditional waveform filter. This provides a reference for the waveform design of a future mobile IoT communication system.

     

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