为了研究无线光通信中数字脉冲调制与信道编码的联合编码调制问题, 在给出调制时域结构的基础上, 采用理论推导和数值仿真相结合的方法, 分析了基于二进制线性分组码的开关键控、数字脉冲位置调制和数字脉冲间隔调制系统的差错性能, 得出了信道编码纠错能力与调制阶数的结合关系。结果表明, 采用开关键控调制的系统, 其汉明距离与欧式距离等价, 故不存在调制与信道编码参量匹配问题; 脉冲位置调制系统在纠错个数大于调制阶数时, 可取得较明显的编码调制增益, 当纠错个数能被调制阶数整除时, 编码和调制达到匹配; 由于数字脉冲间隔调制的符号时隙不固定, 存在错误传播现象, 不宜与差错编码联合使用。所得结果可为无线光通信链路的设计提供参考。

For the sake of studying coded modulations between digital pulse modulation(DPM) and channel error coding in optical wireless communication, after introducing time domain structure of DPM, the error performances of on-off keying(OOK), pulse position modulation (PPM) and digital pulse interval modulation(DPIM) systems were analyzed with binary linear block code. Afterward computer simulations were conducted and the relationship between error correction ability of channel code and modulation level of DPM was obtained. Numerical results show that there is no matching issue for an OOK system using binary linear block code because its bijection between Hamming distance and Euclidean distance. For a PPM system, much better coding and modulation gain can be acquired if error correction number of binary linear block code is bigger than modulation level M. Especially, when error correction number is divided exactly by M, the coding gain and coding cost can get to balance. Moreover, channel code is not fit for DPIM since its variable symbol slots which cause error propagation. The conclusions can be used to help design of optical wireless link.