论文标题
改进了光学无线OFDM的接收器：信息理论观点
Improved Receivers for Optical Wireless OFDM: An Information Theoretic Perspective
论文作者
论文摘要
我们考虑提高不对称的光学正交频施加多路复用（ACO-OFDM）和相关光学OFDM方案的性能，这是强度调制的光学无线通信中OFDM的变化。与大多数有关改进接收器的特定设计的研究不同，本文研究了所有可能接收器的信息理论限制。对于独立且分布的复杂高斯输入，我们获得了ACO-OFDM的信息率的精确表征，并改善了所有SNR的接收器。事实证明，改进的接收器的高SNR增益渐近地实现了每个通道使用的1/4位，在电气SNR中相当于3 dB或光学SNR中的1.5 dB；随着SNR的降低，改进的接收器的最大可实现的SNR增益单调降低至非零低SNR限制，对应于36.3％的信息率增长率。对于实际使用的星座，我们得出了改进接收器的增益的上限。数值结果表明，通过组合现有改进的接收器和编码调制，可以在光学SNR中以1 dB的位置接近上限。我们还表明，我们的信息理论分析可以扩展到FLIP-OFDM和PAM-DMT。我们的结果表明，对于被考虑的方案，改善的接收器可能会在低到中度SNR处显着降低通向容量的差距。
We consider performance enhancement of asymmetrically-clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and related optical OFDM schemes, which are variations of OFDM in intensity-modulated optical wireless communications. Unlike most existing studies on specific designs of improved receivers, this paper investigates information theoretic limits of all possible receivers. For independent and identically distributed complex Gaussian inputs, we obtain an exact characterization of information rate of ACO-OFDM with improved receivers for all SNRs. It is proved that the high-SNR gain of improved receivers asymptotically achieve 1/4 bits per channel use, which is equivalent to 3 dB in electrical SNR or 1.5 dB in optical SNR; as the SNR decreases, the maximum achievable SNR gain of improved receivers decreases monotonically to a non-zero low-SNR limit, corresponding to an information rate gain of 36.3%. For practically used constellations, we derive an upper bound on the gain of improved receivers. Numerical results demonstrate that the upper bound can be approached to within 1 dB in optical SNR by combining existing improved receivers and coded modulation. We also show that our information theoretic analyses can be extended to Flip-OFDM and PAM-DMT. Our results imply that, for the considered schemes, improved receivers may reduce the gap to channel capacity significantly at low-to-moderate SNR.
