针对脉冲位置调制(PPM)和数字脉冲间隔调制(DPIM)等方法存在的问题,提出了一种新的双宽脉冲位置调制(DD-PPM)方式。在给出其符号结构的基础上,分析了带宽需求、传输容量和平均功率,推导出弱湍流信道下的误包率模型,并将其与开关键控调制(OOK),PPM和DPIM等典型调制方式进行了比较。理论分析和仿真结果表明,DD-PPM不仅比OOK具有更高的功率利用率和更好的差错性能,比PPM具有更高的带宽效率和传输容量,比DPIM具有相近甚至略好的差错性能,而且因符号长度固定,解调时不存在等待或缓存器溢出等问题,较DPIM更易工程实现。因而作为一种折中的调制方式,DD-PPM在无线光通信中有一定的应用场合。

A new modulation scheme called dual duration pulse position modulation (DD-PPM) is proposed for optical wireless communication system to overcome the short comings of pulse position modulation (PPM) and digital pulse interval modulation (DPIM). After introducing symbol structure, we study the bandwidth requirement, average transmission power and capacity. Meanwhile, the packet error rate in weak turbulence channel model is derived, and compared with on-off keying (OOK), PPM and DPIM. Theoretical and simulation results show that DD-PPM requires less average optical power and gives better bit error performance compared with OOK, and offers high bandwidth efficiency and transmission capacity compared with PPM for the given parameters. Because the symbol length is fixed in DD-PPM, there is no problems such as buffer overflow or waiting in modem, and it is more realizable than DPIM. Hence, DD-PPM is superior in optical wireless communication system.