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在深空激光通信中,脉冲位置调制(PPM)是一种常见的调制方式。而传统的多脉冲位置调制(MPPM)方式中每个信号块发送光脉冲的数目是固定的,随着深空探测技术的不断发展,对调制方式的要求也不断提高,需要对MPPM方式进行改进,因此,在MPPM方式基础上,提出了一种新的调制方案(n脉冲XPPM)以提高MPPM的误码率(SER)和带宽利用率。基于n脉冲XPPM的传输特性,推出其传输速率、所需功率和带宽以及SER的表达式,通过与传统的单脉冲位置调制(LPPM)和MPPM比较,得出在相同的平均功率情况下,n脉冲XPPM方法的SER比传统MPPM方法低得多,并且在传输速率以及所需带宽方面,n脉冲XPPM也优于其他两种PPM方式。室内仿真实验表明,在通信距离大约为4×1011 m的地球至火星深空通信系统中,采用n脉冲XPPM方式可以使系统的传输速率达到2.746 Mbit/s,带宽利用率也可达到85%左右。
In deep space laser communication, pulse position modulation (PPM) is a common modulation method. However, the number of optical pulses transmitted by each signal block in the conventional multi-pulse position modulation (MPPM) method is fixed. As the deep space exploration technology continues to evolve, the requirements on the modulation method are also increasing, and the MPPM method needs to be improved Therefore, based on the MPPM method, a new modulation scheme (n-pulse XPPM) is proposed to improve the bit error rate (SER) and bandwidth utilization of the MPPM. Based on the transmission characteristics of n-pulse XPPM, the expressions of transmission rate, required power and bandwidth, and SER are derived. Comparing with traditional single-pulse position modulation (LPPM) and MPPM, it is found that under the same average power, n The pulsating XPPM method has a much lower SER than the traditional MPPM method, and n-pulse XPPM is also superior to the other two PPM modes in terms of transfer rate and required bandwidth. The simulation results show that the system can achieve a transmission rate of 2.746 Mbit / s and a bandwidth utilization of about 85% using n-pulse XPPM in the earth-to-Mars deep space communication system with a communication distance of about 4 × 1011 m .