【摘要】 本文主要在认知系统下研究最优功率分配问题,其中主用户和非主用户共享同一频谱资源。在本系统中主用户基于多天线技术,而非主用户基于MIMO-OFDM技术。利用信道感知技术可以使非主用户首先监听主用户的传输信息,其次估计从主用户到非主用户的正交空间。不同于之前的关于MIMO认知系统中信道感知技术的研究,本文首次把OFDM技术引入MIMO认知系统中并在本系统中考虑非理想信道估计问题。然而由于信道估计误差,估计信道和实际信道之间有误差,使得从非主用户到主用户终端的干扰没有完全消除。然后本文提出了一种有效的算法,使得我们得到了在保证主用户Qo S下最大化非主用户吞吐量的最优的功率分配。仿真结果描述了非主用户的发射功率约束和主用户的干扰功率约束以及非主用户的吞吐量之间的影响。更多还原

【Abstract】 This paper is concerned with the optimal power allocation strategy in cognitive radio systems for a cognitive radio(CR) link under spectrum sharing with an existing primary radio(PR) link. The PR is equipped with multi antennas and the CR is in orthogonal frequency division multiplexing(OFDM) based multiple input multiple output(MIMO) cognitive radio systems. It is assumed that in channel learning scheme, CR transmitter first listens to PR transmission and then estimates the spaces that are orthogonal to the channels from PR. Unlike prior study on channel learning in MIMO based cognitive radio systems, this paper is first to bring the OFDM technology to MIMO based cognitive radio systems and consider the imperfect channel learning. Owning to the channel estimation errors, the interference from CR transmitter to PR terminals cannot be canceled completely. Moreover, an effective algorithm is proposed, and we get the optimal power allocation to maximize CR throughput in precondition of assuring PR Qo S. Simulation results show the relations among the CR transmit power constraint, the interference power constraint at PR and CR throughput.更多还原