基于离散小波变换的O-OFDM-DIM

光正交频分复用索引调制技术具有良好的误码性能,但其传输速率不够理想。因此,利用离散小波变换并结合差分脉冲位置调制的思想,提出了一种基于离散小波变换的光正交频分复用差分索引调制(O-OFDM-DIM)。通过小波变换和移除每个子载波块末端的静默子载波实现传输速率的大幅提升;利用小波变换的正交性和子载波分配算法有效抵御大气湍流效应。详细介绍了所提方案的映射原理,推导了其理论误比特率,并与现有的非对称限幅光正交频分复用索引调制(ACO-OFDM-IM)方案进行了对比。结果表明,在大信噪比时,所提方案能获得比ACO-OFDM-IM更高的传输速率和更好的误码性能,而且前者的传输速率提高了近3倍。在误比特率为1×10^-4的强湍流条件下,其信噪比改善了约2dB。

O-OFDM-DIM Based on Discrete Wavelet Transform

Optical orthogonal frequency division multiplexing with index modulation technology performs well in terms of bit error rate performance but with low transmission rate. Therefore, employing discrete wavelet transform and combining the idea of differential pulse position modulation, an optical orthogonal frequency division multiplexing with differential index modulation (O-OFDM-DIM) based on discrete wavelet transform is proposed. The transmission rate is greatly improved by using wavelet transform and removing the silent subcarriers at the end of each subcarrier block. The orthogonality of wavelet transform and the subcarrier allocation algorithm are used to eliminate the impact of channel turbulence. The modulation mapping principle of the proposed scheme is introduced in detail, its theoretical bit error rate expression is derived. In addition, its performance is compared with the existing asymmetrically clipped optical orthogonal frequency division multiplexing with index modulation (ACO-OFDM-IM) scheme. The simulation results show that the proposed scheme achieves a higher transmission rate and lower bit error rate than ACO-OFDM-IM. In particular, the transmission rate of the proposed is nearly three times that of its baseline scheme at a high signal-to-noise ratio, and the signal-to-noise ratio is improved by about 2dB under a strong turbulence channel when the bit error is 1×10^-4.