Optimal power allocation scheme under FSA constraint for OFDM based cognitive radio systems
Optimal power allocation scheme under FSA constraint for OFDM based cognitive radio systems
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基于 OFDM 的认知无线电系统 FSA 约束下的最优功率分配方案
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
B. Evans
中科院分区：
文献类型：
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作者：
Ahmed Sohail;P. Xiao;B. Evans
在文献中，研究人员评估了基于OFDMCR系统的零均值循环对称复高斯(ZMCSCG)约束下的最优功率分配算法。二次用户(SU)的容量最大化，同时保持引入主用户(PU)频带的干扰保持在可容忍范围内。然而，这种方法的缺点是信道容量随信噪比的增加而增加，这不适用于实际场景。因此，我们提出了一种在有限符号字母表约束下(即QPSK、8-PSK、16-QAM和-QAM等)的最优功率加载方案。以获得真实的系统性能，特别是在高信噪比区域下。随后，推导了互信息(MI)，并与信道容量进行了比较，结果表明，在低信噪比区域，它们是密切相关的。相反，MI在高信噪比区域饱和，该高信噪比区域指示实际系统的最大可实现数据速率。我们通过改变干扰门限来进一步评估信道容量和MI，我们的观察是由MI指示的可达SU数据速率的饱和值相应地改变，但总可达数据速率保持不变。另一方面，容量随着干扰门限的增加而增加。
In the literature, researchers have evaluated optimal power loading algorithms under the Zero Mean Circularly Symmetric Complex Gaussian (ZMCSCG) constraint in OFDM based CR systems. The capacity of the Secondary User (SU) is maximized while keeping the interference introduced to the Primary User (PU) band remains within tolerable range. However the drawback of such an approach is that channel capacity increases with increasing Signal to Noise Ratio (SNR), which is not applicable to a practical scenario. Therefore, we propose an optimal power loading scheme under the Finite Symbol Alphabet (FSA) constraint, (i.e., QPSK, 8-PSK, 16-QAM and 64-QAM, etc.) to achieve realistic system performance especially under the high SNR region. Subsequently, Mutual Information (MI) is derived and compared against channel capacity which reveals that in the low SNR region, they are closely related. Conversely, MI saturates in the high SNR region which indicates maximum achievable data rates for practical systems. We further evaluate channel capacity and MI by varying the interference threshold and our observation is that the saturation value of the achievable SU data rate indicated by MI changes accordingly, but total achievable data rate remains constant. On the other hand, capacity increases with increasing interference threshold.