在紫外光散射通信系统中,脉冲展宽和噪声会对信号产生严重影响。为降低系统误码率、提高通信距离,加入了低密度奇偶校验码(LDPC)进行码元纠错。对比了开关键控(OOK)和二进制相移键控(BPSK)副载波强度调制的性能,仿真分析了BPSK副载波强度调制下不同编码效率、不同译码方式的LDPC码对非直视(NLOS)紫外光通信系统误码率的影响。结果表明:BPSK副载波强度调制的性能优于OOK调制,编码效率越小的LDPC码的纠错能力越强,置信传播算法和对数似然比置信传播算法译码性能几乎一致,均优于最小和算法。在小角度、短距离时,非直视紫外光通信系统误码率更小,当误码率为6.5×10 ^-6时,LDPC(672,168)码与未编码序列相比,通信距离提高约一倍。

In ultraviolet (UV) scattering communication systems, pulse broadening and noise considerably affect the signal. To reduce system bit error rate and increase communication distance, it is necessary to add low-density parity check code (LDPC) to implement symbol error correction. The performance of on-off keying (OOK) modulation and binary phase-shift keying (BPSK) for subcarrier intensity modulation is compared. Further, the influence of LDPC codes with different coding efficiencies and decoding methods under BPSK subcarrier intensity modulation on the bit error rate of a non-line-of-sight (NLOS) ultraviolet communication system is simulated and analyzed. Results indicate that BPSK subcarrier intensity modulation performs better than OOK modulation. LDPC codes with low coding efficiency values exhibit strong error correction ability. The performances of belief propagation (BP) algorithms and log-likelihood ratio belief propagation (LLR BP) algorithms are virtually the same, and both are better than min-sum algorithms. When the bit error rate is 6.5 × 10 -6, the communication distance of the LDPC (672,168) coded sequence is approximately doubled, compared with the uncoded sequence.