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Time varying channel breaks the orthogonality between the subcarriers of Orthogonal Frequency Domain Multiplexing (OFDM). This introduces Intercarrier Interference (ICI). One of the ways to mitigate ICI is to first estimate the channel and then equalize it. In this paper we propose to estimate the channel using Discrete Proplate Spheroidal Sequences (DPS) using pilot carriers interleaved with data...
OFDM based wireless system provides high spectral efficiency but they are very sensitive to Doppler shift. High mobility causes the channel to be fast fading channel. The rapid variation of the channel can induce inter carrier interference (ICI). ICI due to carrier frequency offset can be mitigated by accurate frequency synchronization but ICI due to fast fading channel is more difficult to handle...
In fast moving environment, the inter-carrier interference (ICI) due to Doppler spread will degrade the performance of OFDM system severely. Using Jakes' model for the Doppler power spectrum and linear model for time-varying channel during an OFDM symbol interval, the analytical closed- form expression of ICI power, signal-to-interference ratio (SIR) and signal-to-interference-plus-noise ratio (SINR)...
In high-mobility OFDM systems, Doppler distortions cause inter-carrier interference (ICI) that may degrade the system performance severely. Although thoroughly studied, hardly any approaches for ICI estimation and compensation exist that maintain the OFDM-specific subcarrier-wise signal processing and thus provide a solution with reasonable demands on complexity. For a multi-antenna receiver, this...
Doubly-selective channel estimator for orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper. Based on the generalized complex exponential basis expansion model (GCE-BEM), we describe the time-variant channel with time-invariant coefficients over multiple OFDM blocks. The time variation of channel destroys the orthogonality between subcarriers. The resulting channel matrix...
Orthogonal Frequency Division Multiplexing (OFDM) is receiving increased interest for use in underwater acoustic communication systems. It is well-known that OFDM decomposes linear time-invariant channels into a set of parallel (non-interfering) channels via a Fourier basis. However, underwater acoustic communication channels can suffer from significant Doppler effects; for time-varying channels,...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H) which is required to operate under high mobility conditions resulting in significant Inter-Carrier Interference (ICI). Under these conditions, the conventional one-tap per subcarrier channel estimation and equalization is suboptimal since it does not account for ICI...
This paper addresses adaptive channel estimation for time-varying mobile wireless channels with nonstationary statistics. We presents a reduced complexity adaptive channel estimator based on a set membership filtering approach known as the Optimal Bounding Ellipsoid (OBE) algorithm. To exploit time and frequency domain correlation properties of the channel in an efficient low-complexity way, we allow...
Effects of improved channel estimation are studied for a proposed IEEE 802.11n OFDM MIMO system. Three channel estimation methods are considered: maximum likelihood (ML), time-domain truncation (TDT) and model-based (MB). TDT and MB are particularly useful when the channel delay spread is short. For an MMSE receiver, MB shows a 1-2.5 dB improvement over ML on the packet error rate performance for...
In this paper we consider the coexistence issue between OFDM-based WLANs of the 802.11a family and time-hopping ultra wideband (TH-UWB) systems. A general analytical expression is provided for the bit error rate (BER) of the OFDM transceiver operating in the presence of UWB interference and the interferences caused by the multipath propagation phenomenon on the 802.11a OFDM signal, comprising intersymbol...
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