摘要
为了解决光载无线(radio-over-fiber,RoF)通信系统发射机光功率受限问题,同时提高信息传输的可靠性,结合低密度奇偶校验(low-density parity-check,LDPC)码与概率整形(probabilistic shaping,PS)技术,提出一种LDPC-PS-64QAM方案来优化RoF系统的传输特性.该方案采用标志取反法对64正交振幅调制(quadrature amplitude modulation,QAM)信号进行PS,同时采用第三代合作伙伴计划(3GPP)组织规定的LDPC码作为信道编码方案.仿真结果显示,在符号速率为10 Gbaud 时,对比均匀分布(uniform distribution,UD)与 PS 信号的误码率(bit error rate,BER),PS 信号比UD信号发射功率降低了 1.4 dB,采用LDPC码后,发射机的发射功率得到进一步降低;光纤长度为20 km时,在相同BER情况下,PS信号比UD信号光信噪比(optical signal-to-noise ratio,OS NR)降低了2.1 dB,抗噪性能更佳;改变光纤的传输长度,结果显示,LDPC-PS-64QAM系统具有更高的可靠性.
Abstract
In order to solve the optical power limitation problem of the transmitter of the radio-over-fiber(RoF)communication system and to improve the reliability of information transmission,a LDPC-PS-64QAM scheme is proposed by combining low-density parity-check(LDPC)codes and probabilistic shaping(PS)techniques to optimise the transmission characteristics of RoF systems.The scheme uses the sign reversal method to probabilistically shape the 64-quadrature amplitude modulation(QAM)signal,while the LDPC code specified by 3GPP is used as the channel coding scheme.The simulation results show that at a symbol rate of 10 Gbaud,the bit error rate(BER)of uniform distribution(UD)and PS signals are compared,and the transmitting power of PS signal is reduced by 1.4 dB compared with UD signal,and the transmitting power of the transmitter is further reduced by using LDPC code;at the fiber length of 20 km,the optical signal-to-noise ratio(OSNR)of PS signal is reduced by 2.1 dB compared with that of UD signal at the same BER,and it has a better noise resistance.The result shows that the LDPC-PS-64QAM system has higher reliability by changing the transmission length of the fiber.
NETL
NSTL
万方数据