DESIGN AND ANALYSIS OF A CONSTANT ENVELOPE-MULTICARRIER MODULATION SCHEME FOR MULTI-USER SYSTEM BASED ON MMWAVE MIMO FOR 5G COMMUNICATION SYSTEM

Abstract

The Orthogonal Frequency Division Multiplexing (OFDM) used in 4G has been suggested for application in 5G with modification to avoid high signal amplitude fluctuations which causes the problem of peak-to-average power ratio (PAPR). The presence of high PAPR influences OFDM sensitivity to nonlinear distortion caused by the transmitter’s power amplifier (PA). In the absence of power back-off, which is the reduced output power when the input power is decreased, the system experiences spectral broadening, intermodulation distortion and performance degradation. The efficiency of PA is reduced with increase in back- off, therefore, this is a particular problem for mobile battery device due to limit in its power resources. A new mitigation technique for PAPR is the use of constant envelope multicarrier. The Constant Envelope Orthogonal Frequency Division Multiplexing (CE-OFDM) scheme reduces PAPR to 0 dB in which the signal is transmitted with saturating amplifiers without amplitude distortion and spectral regrowth. The CE-OFDM has only been investigated in single input single output (SISO) scheme, with transmission in millimeter wave (mmWave) frequencies (E-band frequencies) 71-76GHz and 81-86GHz channels to provide enough bandwidth that can overcome the growing demands of communication. However, SISO systems have limited capacity and throughput. To mitigate against this for 5G application, Multiple Input Multiple Output (MIMO) is required. The recent new type of MIMO introduced by Sugiura et al. called Space Time Shift Keying (STSK) is capable of achieving high diversity-multiplexing tradeoff (DMT) as compared to other types MIMO. In this work, the STSK CE-OFDM in mmWave transmission has been designed. The transmission performance analysis was done by comparing the Bit-Error-Rate (BER) against Signal-to-Noise-Ratio (SNR) in a dense urban environment for small cell backhaul technology in the absence of phase noise effects. The simulation analysis was carried out with respect to line of sight (LOS) for Uplink transmission in 73GHz mmWave channel, with 2×2 antenna system and STSK configuration being adapted from previous work. The results show that STSK CE-OFDM in mmWave channel experiences a decrease in BER as the modulation index (MI) increases. In addition, the STSK CE-OFDM outperforms the STSK OFDM when a non-linear power amplifier is adopted. Generally, the designed STSK CE-OFDM system is recommended for uplink communication due its ability of consuming low power since it has 0 dB PAPR. The application of this system to uplink communication will increase the battery life and minimize the communication cost to the end user.