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在认知无线网络中,主用户与认知用户要求在频率选择性衰落信道下与它们各自相应的接收机进行同时通信.主用户与认知用户之间的干扰必须尽可能消除以实现两者的频谱共享.本文提出了认知正交频分复用(OFDM)中采用Vandermonde预编码的预编码多址接入(PDMA)策略,它有效利用认知信道的频率选择性构成频率波束成型器.在主用户干扰受限和最优功率分配策略下,采用Vandermonde预编码可使认知用户达到高比特传输率.理论推导过程均采用数值计算与仿真得到证明.数值计算与仿真结果表明,最优输入功率分配策略可使认知用户对主用户不产生干扰的前提下获得可达比特传输率(ABR).同时,数值仿真验证了理论推导过程.在认知无线网络中,采用Vandermonde预编码器构成PDMA,认知用户接收机信噪比与主用户目标速率均可以显著影响认知用户的可达比特率.
In cognitive wireless networks, primary and cognitive users are required to communicate simultaneously with their respective receivers under frequency selective fading channels.The interference between the primary and cognitive users must be minimized to achieve both This paper presents a precoding multiple access (PDMA) strategy using Vandermonde precoding in cognitive orthogonal frequency division multiplexing (OFDM), which effectively utilizes the frequency selective cognitive channel to construct a frequency beamformer In the main user interference limited and optimal power allocation strategy, the use of Vandermonde precoding enables cognitive users to achieve high bit-rate transmission.The theoretical derivation process is verified by numerical computation and simulation.Numerical calculations and simulation results show that the most Optimal input power allocation strategy can make the cognitive user achieve the highest bit rate (ABR) without any interference to the main user.At the same time, the numerical simulation verifies the theoretical derivation process.In the cognitive wireless network, Vandermonde precoding Constitute PDMA, cognitive user receiver signal to noise ratio and the main user target rate can significantly affect the cognitive user’s reachable bit rate.