One of the major problems in OFDMbased multiple access schemes is uplink synchronization. In this paper, we propose an algorithm for the blind estimation of multi-user OFDM synchronization parameters. Our method assumes that all users employ the same pulse shaping filter and uses secondorder statistics only. The proposed approach provides high-resolution estimates in the sense of being able to ...

OFDM is defined as a form of multi-carrier modulation where the carrier spacing is carefully selected so that each sub carrier is orthogonal to the other sub carriers. As the sub carriers are orthogonal, the spectrum of each carrier has a null at the center frequency of each of the other carriers in the system. Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique to perfor...

We consider the problem of degradation in performance multi-carrier multi-user massive MIMO systems when channel induced Doppler spread is high. Recently, Orthogonal Time Frequency Space (OTFS) modulation has been shown to be robust spread. In OTFS based systems, information symbols are embedded delay-Doppler (DD) domain where they jointly modulated generate time-domain transmit signal. Due mul...

Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM), confirmed as an efficient technique, has been applied in optical wireless communications (OWCs) to improve the transmission rate. However, disadvantage of high peak-to-average power ratio (PAPR) also brings into OWC systems, especially for multi-user communications, resulting low efficiency. This paper prop...

Orthogonal frequency division multiplexing (OFDM) is a special case of multicarrier transmission and frequency division multiplexing, where a single data stream is transmitted over several lower rate subcarriers, placed orthogonal to each other. Today it is becoming the chosen modulation technique for wireless communications. It can provide large data rates with optimum bit error rate and enoug...