The Orthogonal Frequency Division Multiplexing (OFDM) has widely been used in broadband wireless communication due to its ability to efficiently utilize the spectrum with multicarrier communication. In this paper BER expression for π/4 DQPSK modulation has been derived from FrFT based OFDM system in the presence of carrier frequency offset (CFO) under frequency selective Rayleigh fading channel...

1.1 Preliminary Orthogonal frequency-division multiplexing (OFDM) communication techniques have recently received significant research attention because of their ability to maintain effective transmission and highly efficient bandwidth utilization in the presence of various channel impairments, such as severely frequency-selective channel fades caused by long multipath delay spreads and impulsi...

This thesis investigates three possible methods to increase the performance of digital communication systems, with focus on wireless systems, by accounting for some of the channel effects that may occur. The modulation scheme plays an important role in the impact of different channel effects on system performance and this work considers both a single-carrier system and orthogonal frequency-divi...

This paper investigates a design and performance of 4parallel MB-OFDM UWB receiver. The performance of the proposed MB-OFDM UWB receiver using a 4-parallel synchronization structure is degraded by 0.25 dB compared with that of a receiver using a 1-parallel synchronization structure in the maximum frequency/sampling clock offset tolerance in an AWGN channel. Considering other impairments, includ...

We propose an adaptive channel estimation (CE) method for zero-guard-interval (ZGI) coherent optical (CO)-OFDM systems, and demonstrate its performance in a single channel 28 Gbaud polarization-division multiplexed ZGI CO-OFDM experiment with only 1% OFDM processing overhead. We systematically investigate its robustness against various transmission impairments including residual chromatic dispe...

Abmac-OrIhqonal Frequency Division Multiplexing (OFDM) modulatlon, adopted by the L%@tal Video Broadcasting (DVB-T) standard, has been remgniml for its good performance for high data rate wireless communications. Therelore, the study ofthe robust transmission of multimedia data over OFDM system bas attracted e d d v e research interests. In the past, channel eslimation, which is an important as...

Polynomial cancellation coding (PCC) is a very effective technique that reduces the sensitivity of orthogonal frequency division multiplexing (OFDM) to frequency errors at the cost of reduced spectral efficiency. This paper investigates the effect of PCC on the fading characteristics of multipath channels and on the error performance OFDM in a two-path fading channels. Channel coding is employe...

Multiple-input multiple-output orthogonal frequency division multiplexing systems (MIMO-OFDM) has became a promising candidate for high performance 4G broadband wireless communications. However, like OFDM, one main disadvantage of MIMO-OFDM is that the signals transmitted on different antennas may exhibit a prohibitively large peakto-average power ratio (PAPR). In this paper, the influence of g...

MIMO-OFDM is considered as a fast growing technology now days. OFDM is a multi carrier modulation technique in which the carriers are Orthogonal to each others as a result of which it provides high bandwidth efficiency and multiple carriers share the data among themselves. During the research equalizer is always a matter of strategies. When a signal is transmitted over a radio channel, it is su...

Medium access control (MAC) protocols in a cognitive radio network (CRN) are required to increase spectral efficiency and achieve high data rate for secondary users (SUs). Many MAC protocols use a single control channel with a bottleneck problem. In this paper, we propose a multichannel MAC protocol using dicontiguous orthogonal frequency division multiplexing (D-OFDM) in a CRN. Since D-OFDM te...