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Cooperative networking schemes provide spatial diversity gain (named cooperative diversity gain) using the antennas of spatially distributed users. Consistent research has been focusing on cooperative networks using orthogonal frequency division multiplexing (OFDM) and single carrier with frequency domain-equalization (SC-FDE). Coherent detection and frequency-domain equalization (FDE) require accurate...
MIMO-OFDM is the promising technique in the future of wireless communications as it combines the properties of Multiple Input Multiple Output (MIMO) systems with those of Orthogonal Frequency Division Multiplexing (OFDM). However, it is very sensitive to frequency offsets which result in inter-carrier interference (ICI). Therefore, to precisely recover the transmitted data, frequency offset compensation...
Orthogonal Frequency Division Multiplexing (OFDM) is a transmission technique that allows simple multipath channel equalization schemes. On the other side it is sensitive to frequency offset at the local oscillator, phase noise and Doppler shift which may destroy the orthogonality among subcarriers causing Inter Carrier Interference (ICI). It is possible to represent this interference in the frequency...
Orthogonal Frequency Division Multiplexing (OFDM) is multiplexing technology of orthogonal multi-carrier, and the channel estimation model based on pilot in OFDM systems is analyzed; Now that, the channel estimation based on pilot needs interpolation, in order to reduce the complexity of the interpolation algorithm, the FFT channel estimation algorithm based on pilot is studied. Because of the direct...
It is well-known that the OFDM scheme has some tolerance for symbol/frame timing errors (i.e. valid starting position of FFT window). Such tolerance exist for SC-FDE. However, frame timing offset affects the receiver performance due to deviation in frequency domain channel estimation result when fractional channel estimation vector is applied in time domain. To achieve optimized receive performance...
In this paper, we propose the new channel estimation algorithm in frequency domain for orthogonal frequency division multiplexing (OFDM) system in fast fading channels. In this algorithm first we estimate channel response at pilot subcarriers then interpolate channel response at data subcarriers by Gaussian Radial basis function as an efficient nonlinear interpolator. At next step by filtering and...
In orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems, the sub-carriers, which span the spectrum used by licensed users (LUs), should be deactivated to avoid interference. The resulted OFDM system is called non-contiguous OFDM (NC-OFDM) system. For NC-OFDM systems, as no pilot symbols can be transmitted over these deactivated subcarriers, the conventional modified...
Orthogonal frequency division multiplexing (OFDM) is an attractive and effective technique for wireless communications. However, an OFDM signal has a large peak-to-average power ratio (PAPR), which will cause serious nonlinear distortion especially when the signal passes through a nonlinear system. Adaptive symbol selection scheme (ASSS) is used to reduce the unwanted PAPR by selecting the adaptive...
Orthogonal frequency division multiplexing (OFDM) is a transmission technique which is robust in multipath channels. It is though sensitive to frequency errors that may be caused by several factors such as frequency offset at the local oscillator, phase noise and mobility of the receiver. These errors may destroy orthogonality among subcarriers and introduce intercarrier interference (ICI) that may...
Channel estimation based on two-dimensional discrete- time Fourier transform interpolation (2D-DFTI) is suitable for orthogonal frequency division multiplexing (OFDM) systems because of its robustness to doubly-selective fading channels and high computational efficiency. However, its performance will degrade significantly for packet OFDM systems with virtual subcarriers due to the Gibbs phenomenon...
Multiple-input multiple- output (MIMO) and orthogonal frequency division multiplexing (OFDM) are two key techniques for broadband wireless mobile communications. In order to provide accurate channel state information (CSI) to support MIMO-OFDM transmission in doubly-selective fading channels, we propose the robust channel estimator based on two-dimensional enhanced discrete-time Fourier transform...
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