A High Energy Efficient Scheme with Selecting Sub-carriers Modulation in OFDM System

With the tremendous growth in wireless networks market, unprecedented energy consumption and emissions of carbon dioxide (CO2) is a growing concern for both operators and governments. OFDM technology has been adopted by many standards organizations due to its high spectrum efficiency, but induces poor energy efficiency of power amplifier (PA). A new scheme named Selecting Sub-Carriers Modulation (SSCM) to lower the input power of PA is given in this paper. SSCM divides the information bits into two parts of bits according to modulation mode: the first part of bits selects some sub-carriers of OFDM to transmit nothing, another part of bits is transmitted by the remainder sub-carriers. Sub-carriers transmitting nothing do not need energy, and fewer number of sub-carriers transmitting modulation symbols can improve PA's efficiency because of the lower peak-to-average power ratio (PAPR). Analysis results show SSCM with different modulation modes can lower input power of PA with different proportion compared with traditional OFDM. Theoretical analysis and simulation results of the reliability of SSCM are given and match closely. In multi-path channel, SSCM with BPSK has the same performance as BPSK in traditional OFDM, while SSCM with QPSK performs worse than QPSK in traditional OFDM.