Design of PN codes for optical wireless code-shift-keying with IM/DD

A pseudo-noise (PN) code used by code shift keying (CSK) for optical wireless communication with intensity-modulation and direct detection (IM/DD) are considered. Since CSK has the several PN codes, the data transmission rate and the bit error rate (BER) performance can improve by increasing the number of PN codes. However, the conventional optical PN codes are not suitable for optical CSK with IM/DD because the ratio of the number of PN codes and the code length of PN code, M/L is smaller than 1/√L. In this paper, a new PN code, which combines the generalized modified prime sequence code (GMPSC) with Hadamard code is proposed. The proposed PN code can achieve M/L = 1. Moreover, the symbol error rate performance is analyzed under the additive white Gaussian noise channel. It is found that CSK with the proposed PN code outperforms the conventional optical CSK system.