NC-OFDM认知无线电波形、导频与标签设计

Non-contiguous OFDM(NC-OFDM) based cognitive radio(CR) technology is one of research hotspots of the current cognitive radio. However, the existing contiguous OFDM technology can not be directly applied to NC-OPDM based cognitive radio system. The project is focused on the research in NC-OFDM sidelobe suppression,PAPR,signature and pilot design. The main contents and innovations include the following:(1)propose a partially windowed non-orthogonal active interference cancellation (AIC) sidelobe suppression method to solve the problem of out-of-band radiation of NC-OFDM, the sidelobe can be suppressed to -80dB deep and caused ICI is less than -50dB;(2)different with traditional sidelobe suppression and PAPR independent design, we combine carrier sidelobe suppression with PAPR suppression and design optimal interference cancellation waveform in order to suppress carrier sidelobe, peak to average ratio and improve the efficiency of the transmitter power amplifier. (3)propose an optimal design scheme of pilot and signature for NC-OFDM based on the knowledge of spectrum holes available,with the characteristic of less channel estimation error, high accurate signature detection,low spectrum cost and computation complexity,and so on. The research work and results will promote the application of CR system in the future.

基于非连续载波OFDM (NC-OFDM)的认知无线电技术是当前认知无线电的研究热点之一。现有的连续载波OFDM系统技术不能直接应用于NC-OFDM认知无线电系统。本项目针对NC-OFDM 旁瓣抑制、PAPR、标签、导频设计开展研究，主要内容与创新点包括：（1）提出基于部分加窗与非正交干扰抵消相结合的NC-OFDM载波旁瓣抑制方法，旁瓣抑制深度达到-80dB，所引入的ICI不超过-50dB，谱效和能效均优于现有方法；（2）与传统的旁瓣抑制和PAPR抑制独立设计不同，本项目拟将载波旁瓣抑制与PAPR抑制相结合，优化设计干扰抵消波形，达到同时抑制载波旁瓣和峰均比、提高发射机功放效率的目的；（3）根据可用空闲频谱资源信息，提出适合NC-OFDM的导频与标签最优设计方案，具有信道估计误差小，标签检测准确度高，频谱开销与计算量小等特点。本项目的研究成果为推动NC-OFDM认知无线电的应用打下基础。

基于非连续载波正交频分复用 (NC- OFDM）的调制技术是当前认知无线电的研究热点之一。NC-OFDM调制存在的最大问题是信号频谱旁瓣过大, 会干扰附近的主用户, 同时还存在峰均功率比过大问题. 本项目主要针对前一问题展开了研究. 主要内容与创新点包括：(1)提出了一种基于加窗与非正交干扰抵消相结合的NC- OFDM载波旁瓣抑制方法，旁瓣抑制深度达到-80dB，降低了次用户对主用户的干扰；(2)提出了一种优化干扰抵消基函数的方案, 在不加窗的条件降低次用户对主用户的干扰, 提高了频谱效率; (3) 提出了一种针对OFDM前缀优化设计的方案, 充分利用OFDM循环前缀时间自由度, 降低次用户对主用户的干扰; (4) 提出了一种适合低信噪比条件的自适应编码调制技术, 能更有效的运用在信噪比较低的认知无线电场景中; (5) 采用软件无线电平台, 设计并验证了NC-OFDM系统方案, 并在该平台上实验NC-OFDM系统的频谱旁瓣抑制. 项目的研究成果将会推动NC-OFDM认知无线电的应用, 并提高无线频谱资源的利用效率。