无线光通信中的定长数字脉冲间隔调制

针对脉冲位置调制(PPM)需要符号同步和数字脉冲间隔调制(DPIM)符号长度不固定所引起的问题,提出了一种新的定长数字脉冲间隔调制(FDPIM)。给出了相应的编码结构,并分析了平均功率效率和带宽需求。在弱湍流信道模型下推导了定长数字脉冲间隔调制的误包率,并与开关键控(OOK)、脉冲位置调制和数字脉冲间隔调制等调制方式进行了比较分析。结果表明,定长数字脉冲间隔调制的误包率劣于脉冲位置调制和数字脉冲间隔调制,但明显优于开关键控的误包率。虽然定长数字脉冲间隔调制的带宽要求较高,但不需要符号同步,相对于脉冲位置调制系统,实现的复杂性大大简化;相对于数字脉冲间隔调制,其符号长度固定,不会出现因符号时隙个数不固定所引起的调制器等待或缓冲器溢出问题。

A Novel Fixed Length Digital Pulse Interval Modulation for Optical Wireless Communications

A new fixed-length digital pulse interval modulation(FDPIM) is presented on the basis of pulse position modulation(PPM) which needs symbol synchronization and digital pulse interval modulation(DPIM) with unfixed symbol length.After introducing symbol structure,average transmit power and bandwidth efficiency are studied.Based on weak turbulence channel model,the packet error rate is derived,and compared with on-off keying(OOK),PPM and DPIM.Simulations show that error rate of FDPIM is bigger than PPM and DPIM,but obviously less than OOK.Moreover,FDPIM,which do not need symbol synchronization and has fixed symbol length,can simplify the receiver and solve modulator waiting or buffer overflow in comparison with PPM and DPIM respectively.Hence,FDPIM has some advantages in wireless optical communications system.