Time-frequency-selective, i.e., time-variant multipath, fading in orthogonal frequency division multiplexing (OFDM) systems destroys subcarrier orthogonality, resulting in intercarrier interference (ICI). In general, the previously proposed estimation schemes to resolve this problem are only applicable to slowly time-variant channels or suffer from high complexity due to large-sized matrix inve...

The constraint to satisfy the need of increased bandwidth requirement for high speed applications with higher performance has been a motivation to work on Optical Orthogonal Frequency division multiplexing (OOFDM) technique with coherent detection. We implement the coherent optical OFDM (CO-OOFDM) technique and investigate the effect of the number of sub-carriers on performance over single mode...

Orthogonal frequency division multiplexing (OFDM) is one of the modulation scheme, used for high speed mobile communication. However, fast time varying multipath channels leads to loss of orthogonality of subcarriers and introduces inter carrier interference (ICI). In this study, MMSE equalizer is implemented to remove ICI. The information of Channel Impulse Response (CIR) required for equalize...

Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a promising technique against the multipath fading channel for wireless communications. However, OFDM faces the Peak-to-Average Power Ratio (PAPR) problem that is a major drawback of multicarrier transmission system which leads to power inefficiency in RF section of the transmitter. This paper present different PAPR reduction...

In this thesis, we develop an subcarrier transmission suboptimal power allocation algorithm and an underlay subcarrier transmission optimal power allocation algorithm for the orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems with different statistical interference constraints imposed by different primary users (PUs). Given the fact that the interference constr...

Mazo’s concept of Faster Than Nyquist signaling is extended to pulse trains that modulate adjacent subcarriers, in a manner similar to orthogonal frequency division multiplex (OFDM) transmission. Despite pulses that are faster than the Nyquist limit and subcarriers that significantly overlap, the transmission system achieves the isolated pulse error performance. Systems with at least twice the ...

Smart antennas increase capacity of wireless systems by allowing channel reuse by several users in the same cell through space division multiple access (SDMA). Orthogonal Frequency Division Multiplexing (OFDM) creates additional challenges in beam-forming when the beams that can be formed are limited due to transceiver unit limitations. We investigate the impact of smart antennas on channel all...

Generalized Frequency Division Multiplexing (GFDM) is one of the multi-carrier transmission techniques considered as an alternative to orthogonal frequency division multiplexing (OFDM) for 5G wireless communication systems. GFDM is a flexible multi-carrier scheme that spreads the data symbols in a time-frequency block. Compared to OFDM, in GFDM each subcarrier is additionally filtered with a ci...

For wireless transmission, the channel estimation is necessary to improve the performance of receiver. In the ultra-wideband (UWB) wireless systems, there are two practicable modulation schemes: orthogonal frequency-division multiplexing (OFDM) and single-carrier direct-sequence UWB (DS-UWB). The OFDM based scheme is an attractive mode because it can capture the multipath energy more efficientl...

High Peak to Average Power Ratio (PAPR) of the transmitted signal is a critical problem in multicarrier modulation systems (MCM) such as Orthogonal Frequency Division Multiplexing (OFDM), and Multi-Carrier Code Division Multiple Access (MC CDMA) systems, due to large number of subcarriers. High PAPR leads to reduced resolution, and battery life. It also deteriorates system performance. This pap...