Advanced modulation techniques in massive mimo

Orthogonal frequency division multiplexing with cyclic prex (CP-OFDM) is the primary modulation format in the massive multiple-input multiple-output (MIMO) literature as well as most of the current wireless communication standards. This waveform, however, suers from a number of drawbacks. In particular, the high spectral leakage of the OFDM subcarriers, the overhead due to the CP duration, and the high peak-to-average power ratio (PAPR) are the three most important shortcomings of this waveform. In this dissertation, we study some alternative modulation formats to address the limitations of CP-OFDM, particularly in massive MIMO systems. Three dierent designs are considered to target the above drawbacks of OFDM individually. In the rst one, lter bank multicarrier (FBMC) is considered to relieve the spectral leakage problem of OFDM in massive MIMO systems. We show that in FBMC-based massive MIMO, when linear equalization methods such as MRC, ZF, and MMSE, are applied, the signal-to-interference-plus-noise ratio (SINR) does not necessarily improve as the number of BS antennas grows large and saturates at a certain deterministic level. This phenomenon results from the law of large numbers and is due to the correlation between the combiner taps and the channel coecients. In order to resolve the saturation problem, we develop an ecient equalization method to remove this correlation. In the second design, we study the possibility of removing the CP in OFDM to increase its spectral eciency. Again, we show that a similar saturation problem exists in OFDM without CP systems. In this part, we develop another equalization structure based on the time-reversal technique. We show that by utilizing the proposed method, higher spectral eciency can be achieved by removing the CP overhead in massive MIMO systems. Finally, we consider single-carrier (SC) transmission in massive MIMO, to reduce PAPR. A novel receiver design based on time-reversal combining and frequency-domain equalization is proposed for this system. We show that through the proposed receiver structure, the performance of SC transmission can be enhanced in moderate to high signal-to-noise ratio (SNR) regimes.