多用户认知无线电系统中波束成形技术研究

Study on Beamforming in Multi-user Cognitive Radio Network

多入多出(multiple-input multiple-output,MIMO)技术给系统引入了可供共享与分配的空间资源,在时间和频率资源之外增加了空间自由度,可以更好地起到减少对主用户干扰并提高次用户容量的作用。在文中提出的系统模型中,主、次用户信道发射端均配备了多根天线,主用户接收端可以通过有限反馈信道将信道状态信息反馈给次用户发射端。在此基础上,设计次用户发射波束成形矢量,并给出了主、次用户中断率表达式。仿真表明,在该系统模型下,主、次用户中断率更小,次用户的中断率随着反馈比特数的增加不断趋近于一个固定值。

Multi-input multi-output （MIMO） technology provides the system with sharing space, increas- ing the degrees of freedom of space in addition to time and frequency, which can reduce interference to the primary user （PU） and improve the capacity of secondary user （ SU ）. In this paper, both of the primary base station （PBS） and the secondary base station （SBS） are equipped with multi-antennas. The PU re ceiver communicates to the SU transmitter the channel state information through the finite-rate feedback channel, so a cognitive beamfonning（CB） algorithm based on the limited feedback is proposed. The ex pressions of the outage probability are presented. From the simulation results, it can be seen that the out age probability of both links is lower. There exists an asymptotic value which the outage probability of SU approaches.