Architecture, design, and numerical simulation of a code/pulse-position-swapping (CPPS) direct translating receiver

Code/pulse-position-swapping (CPPS) is a communications scheme that substitutes pulse-position-modulation (PPM) symbols with optical-code-division-access (O-CDMA) codes. CPPS retains the multiple bits per symbol communication of M-ary PPM and the asynchronous multiple access of O-CDMA. Additionally, CPPS has the advantages of granular communications, common electrical bandwidth for all users independent of data rates, compatibility with free-space or guided (fiber and waveguide) communication links, and compatibility with intensity modulation/direct detection. The transmitted symbols (codes) of CPPS are translated from a deserialized bit stream that has been divided into words of length log2M. Thus the receivers associate the detected symbol with the original bit sequence by means of an electronically implemented look-up-table (LUT). This paper describes the architecture and design of a direct translating receiver based on map-coding, which uses optical processing to output the transmitted bit sequence without the need for a LUT. Analyses and computations characterize the receiver concept in terms of bit errors (mistranslations).