超高速移动下5G随机接入技术研究

Research on 5G Random Access Technology in Ultra-high Speed

随着高铁速度的不断提升,以及无人机的逐渐发展,高达500 km/h的超高速移动通信受到广泛关注。超高速移动下通信由于距离较远、移动速度高,引发的多普勒效应和往返时延会严重影响系统的随机接入PRACH信号的检测能力。对超高速移动下的5G系统PRACH技术进行研究,分析了多普勒频移对随机接入检测性能的影响。传统采用三窗口联合算法对抗多普勒频率,而当速度达到超高速,频偏大于一个子载波间隔,将采用一种改进的5个检测窗口联合检测方法,并通过添加阈值的方式判决提升检测成功率。设计了一个自适应检测算法,依据2个RRU接收信号功率不同,自适应切换三窗口检测算法和改进后的五窗口检测算法,降低了计算复杂度、提高了抗噪性能。

With the continuous improvement of high-speed rail speed and the gradual development of UAV,ultra-high speed mobile communication up to 500km/h has attracted extensive attention.Due to the long distance and high moving speed of Mach class ultra-high speed communication,the Doppler effect and round-trip delay will seriously affect the detection ability of physical random access channel signal.PRACH technology of 5G system under ultra-high speed movement is studied,and the influence of Doppler frequency shift on random access detection performance is analyzed.Traditional three window joint algorithm is used to combat the Doppler frequency.When the speed reaches 600km/h and the frequency offset is greater than one subcarrier interval,an improved five detection window joint detection method will be adopted,and the detection success rate will be improved by adding a threshold.An adaptive detection algorithm is designed.According to different received signal power of the two RRU,the three window detection algorithm and the improved five window detection algorithm are switched adaptively,which reduces the computational complexity and improves anti-noise performance.