认知无线电中衰落信道下的能量检测信噪比墙

SNR wall for energy detection over fading channels in cognitive radio

分析得到了认知无线电中多径衰落信道下,由微小噪声不确定度引起的能量检测器的"信噪比墙".建立噪声存在不确定度下的鲁棒检测模型,将鲁棒检测概率对衰落的分布求统计平均,并对复杂的积分表达式进行合理的近似和变换得到检测概率的封闭表达式,然后将检测与虚警概率联立并消去检测门限得到了信噪比墙.分析和仿真结果表明衰落信道下的能量检测信噪比墙除了与噪声不确定度相关外,还随目标检测概率的提高显著上升.因此目标检测概率较高时,能量检测器有较高的信噪比墙,从而在接收信噪比较小的认知无线电环境下不再适用.

We have obtaiend the ＂SNR Wall＂, which is induced by noise uncertainty, of the energy detector over multipath fading channels in the cognitive radio. The robust detection model under noise uncertainty is built up. By finding the statistically averaged probability of robust detection over the fading distribution, the closed-form expression for detection probability is derived by making a proper approximation and transformation of the complex integral expression. Then, the SNR Wall is acquired by synthesizing the expressions for the detection and false alarm probability and eliminating the detection threshold. Analytical and simulation results show that the SNR Wall of energy detection over fading channels is related to the noise uncertainty, and increases dramatically with the rising of the target detection probability as well. Therefore, the SNR wall of the energy detector becomes very large when a high target probability of detection is required, and the energy detector is not applicable to the cognitive radio with a small received SNR.