Multilevel Pulse-Position Modulation Based on Balanced Incomplete Block Designs
In this paper, two new modulation schemes using multilevel Pulse-Position Modulation (PPM) for application in unipolar optical wireless systems are presented. Balanced Incomplete Block Designs (BIBD) are used for constructing the symbol alphabets. Each symbol is obtained by combining multiple code-words of a BIBD code. In one scheme the symbols have equal energies, and therefore, no threshold is needed to make a decision on the received signal. The other modulation has better performance yet higher complexity. Since cyclic BIBDs are used for constructing the symbols, the transmitters and receivers have simple structures, and can be implemented using shift registers.