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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...
One of the phenomena that degrades the performance of multicarrier modulation (MCM) systems is the spectral nulls that multipath channel may have. As a result, the affected subcarrier signals may be severely degraded resulting in a loss of symbols. In this paper we have studied how to overcome this problem by taking advantage of spatial diversity along with the knowledge of channel state information...
In this paper, a blind method to detect and suppress narrow-band interference (NBI) for multi-band orthogonal frequency-division multiplexing (MB-OFDM) based ultrawideband (UWB) communications is proposed. The method utilizes mean-square-error (MSE) statistics in the frequency domain to detect subcarriers damaged by NBI. Approximating the MSE statistics by a decision-feedback (DF) scheme creates a...
In this paper, a new space-frequency combination technique is proposed for Alamouti coded Orthogonal Frequency Division Multiplexing (OFDM) in the context of cooperative communications. Since cooperative antennas are distributed, there may exist multiple carrier frequency offsets (MCFOs) which cause problems for conventional space-frequency decoding. The proposed algorithm, taking cues from existing...
Self-cancellation schemes have received a lot of attention due to their simple implementation and high efficiency to suppress intercarrier interference (ICI) in Orthogonal Frequency Division Multiplexing (OFDM) systems. Among those ICI self-cancellation methods, Symmetric Conjugate Symbol Repetition (SCSR) has been proven to have the best bit error ratio (BER) performance for phase noise suppression...
This paper presents a generalized analysis of Multiband OFDM (MB-OFDM) Ultra Wideband (UWB) communication in the presence of generic or non-specific interference sources. The interference sources are assumed to be distributed in a two-dimensional space according to a homogeneous Poisson field. An aggregate interference is formed by the asynchronous operation of these sources. To provide a generalized...
This paper presents a technique for maintaining good broadband transmission quality in the face of impulsive noise in OFDM-PLC systems. The proposed technique is based on adding one zero between two signal samples in order to estimate the noise power in every transmitted signal sample. Simulation results of complete PLC system highlight good improvement in BER and correction ability performances for...
We consider the uplink of a multi-cell orthogonal frequency division multiple access (OFDMA) system that employs multiple (M > 1) receive antennas and maximum ratio combining at the base station. We propose a model that captures the impact of intercell interference coordination on the modulation and coding scheme dependent bit error rate (BER) performance. We analyze this model in two steps. First,...
In this work an iterative time domain least squares (LS) based channel estimation method using superimposed training (ST) for a multi input multi output(MIMO) orthogonal frequency division multiplexing (OFDM) system over frequency selective fading channels is proposed. The estimate of the channel is generalized to provide scope for exploiting the coherence time and the coherence bandwidth for an improved...
In this paper, performance of OFDM digital communication systems have been analyzed over correlated Nakagami-m fading channel using maximal ratio combining (MRC) diversity at the receiver. We have studied statistical characteristics of inter-carrier-interference over correlated Nakagami-m fading channel and also presented signal to interference noise ratio (SINR) over correlated Nakagami-m fading...
Based on the principle of spread spectrum systems, this paper presents a hybrid automatic-repeat-request (HARQ) scheme with the mitigation of intercarrier interference (ICI) by orthogonally encoding transmitted signals on subcarriers for orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme not only increases the signal-to-noise ratio (SNR) but also reduces the ICI. Simulations...
In orthogonal frequency division multiplexing (OFDM) systems, time- and frequency-selective (or doubly-selective) fading leads to the loss of subcarrier orthogonality and the occurrence of inter-carrier interference (ICI), which increases an irreducible error floor in proportional to the normalized Doppler frequency offset. Channel estimation (CE) in rapidly time-varying multi-path scenarios is critical...
The previously proposed first-order perturbation-based algorithm and linear constrained least mean square (LMS) based algorithm for channel matrix singular value decomposition (SVD) in multiple - input multiple - output (MIMO) orthogonal frequency division multiplexing (OFDM) systems are evaluated and compared in this paper from orthogonality, signal to noise plus interference ratio (SINR) and bit...
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