Sustav s jednim nosiocem i visestrukim pristupom po frekvenciji (Single Carrier – Frequency Division Multiple Access – SC-FDMA) je relativno nova

Although spatial modulation (SM) presents an attractive multiple-input–multiple-output (MIMO) technique, it increases peak-to-average power ratio (PAPR) on all transmit antennas when applied directly to single-carrier frequency-division multiple access (SC-FDMA). Therefore, we propose an SM modification, which is called low-PAPR SM (LPSM), to preserve the low PAPR level of SC-FDMA and to achieve the benefits of SM. In addition, as the optimal maximum-likelihood detection (MLD) receiver has a very high computational complexity when applied to SC-FDMA system, we observed suboptimal receivers for SC-FDMA with LPSM. In addition to low-complexity linear receivers, we proposed and analyzed two receivers: near-MLD and improved minimum mean square error (iMMSE) receivers. The near-MLD receiver achieves performance very near to MLD with significantly lower complexity, whereas the iMMSE receiver presents a tradeoff between MLD and linear receivers in terms of performance and complexity.

The paper presents Space-Frequency Block Coding (SFBC) as a transmit diversity technique in Single Carrier Frequency Division Multiple Access (SC-FDMA). SC-FDMA is known as a low Peak-to-Average Power Ratio (PAPR) modulation technique. SFBC requires changing the order of the samples in the frequency domain, which results in increase of the PAPR. Because of that, additional clipping and filtering is proposed to be performed after SFBC to preserve low PAPR level and to avoid the out-of-band radiation. This affects the performance, but still provides significant advantage to the existing techniques, as is shown using simulations

The paper presents the comparison of different low-complexity channel estimation and equalization techniques implemented in Single Carrier Frequency Division Multiple Access (SC-FDMA). Since SC-FDMA is Discrete Fourier Transform (DFT) precoded Orthogonal Frequency Division Multiplex (OFDM), many techniques developed for OFDM can be applied to SC-FDMA. Least Square (LS) and Linear Minimum Mean-Square Error (LMMSE) with different noise reduction and simplification techniques are analyzed and compared in the simulations. Additionally, novel noise reduction method using weighted mean of neighboring subchannels in frequency domain is proposed and compared in simulations.

The paper presents the performance of orthogonal frequency division multiplex (OFDM) and single-carrier frequency domain multiple access (SC-FDMA) in frequency selective channels. OFDM and SC-FDMA, techniques chosen for 3GPP Long-Term Evolution (LTE) downlink and uplink transmission, are compared. Both techniques use frequency domain equalization (FDE). Estimation obtained with zero-forcing (ZF) and minimum mean square error (MMSE) are simulated. Simulation outcomes show BER as a function of SNR in various frequency selective channels.