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Orthogonal frequency division multiplexing (OFDM) has been used widely in many communication systems. However, the major drawback of OFDM is the high peak-to-average-power ratio (PAPR) which results in the bit error rate (BER) performance degradation in nonlinear environments. In this paper, we introduce a new phase weighting method to reduce the nonlinear distortion of OFDM signals in the nonlinear...
In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) transmission scheme and demonstrate its reduced peak-to-average power ratio (PAR). The proposed ISS-OFDM signal is realized by two steps. The first step is to modulate the data symbol by complex exponential spreading and the second is to use an interleaving technique to spread the signal spectrum...
OFDM (Orthogonal frequency division multiplexing) is one of the key techniques for 4th generation high data rate communications system. However OFDM suffers from high peak-to-average power ratio (PAPR) which substantially degrades the efficiency of a linear power amplifier. A new nonlinear companding transform using hyperbolic tangent sigmoid transfer function is proposed for PAPR reduction in this...
Multiuser detection is a field that deals with the detection of multiple users whose received signals are interfering to one another. Orthogonal frequency division multiplexing (OFDM) is increasingly becoming popular in advanced broadband wireless communication systems due to the advantages of its ability to mitigating inter-symbol interference (ISI) effects in frequency-selective fading channels...
A method for time synchronization is proposed for OFDM based WLAN systems. The proposed method has a comparable performance as an existing approach, but requires less computation. The first half of the long-symbol guard interval needs to be zero padded for the development of the new method.
In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals and selects replica with the smallest Euclidean...
This paper presents the results of dynamic channel capacity measurements for a multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system in two populated indoor environments with and without line-of-sight (LoS). The experiment used 4 sending and 4 receiving antennas and 114 sub-carriers at 5 GHz as per draft IEEE 802.11n. MIMO-OFDM channel capacity is analysed both...
In this paper we consider the use of M-QAM hierarchical constellations (quadrature amplitude modulation) combined with implicit pilots for the transmission of multicast and broadcast services in OFDM (orthogonal frequency division multiplexing) systems. This method of pilot transmission allows coherent detection at the receiver while avoiding the spectral degradation associated with the usual pilot...
In recent years, high-speed and high-quality mobile communications have been demanded. Wavelet packet modulation (WPM) has been proposed as one of the multicarrier transmission methods and applied to the mobile communications. The WPM has an advantage of equalizing performance compared with OFDM (orthogonal frequency division multiplexing) when a frequency domain equalizer (FDE) is applied because...
Block transmission in wireless communications systems is very sensitive to Carrier Frequency Offset (CFO). In order to reduce the number of pilot symbols used in the estimation of rapidly-varying CFO it was proposed to use a truncated Taylor's series to predict the CFO, where the derivatives up to order d -1 of the series terms are recursively estimated with a d-order Kalman filter (KF). We propose...
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