We propose a novel modulation and de-modulation method to reduce the complexity of transmitter and receiver which is named multilevel differential pulse amplitude modulation (MD-PAM). The proposed modulation scheme transmits different PAM signals with same amplitude and unit time delay using different multiple LED chips. Optical signals from each LED chips are superposed during through the optical wireless channel and directly detected at the single optical receiver. Received signal is demodulated using signal power difference which is changed by light intensity. As a result, we experimentally confirmed that 100-Mbit/s transmission was possible using two LED chips which have 25MHz modulation bandwidth, respectively.