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Pilot symbol assisted modulation (PSAM) orthogonal frequency division multiplexing (OFDM) has proven to be a popular technique for high-speed communication through multipath fading channels. In this paper we examine PSAM pilot design optimization in OFDM systems that employ edge null subcarriers for spectral shaping. Specifically, we show that the commonly used even pilot spacing design is suboptimal...
The structural properties of multi-path channels such as directions of arrival and departure are estimated from multidimensional channel sounder data by application of high-resolution parameter estimation methods. However, the influence to the accuracy and reliability of the results due to antenna calibration errors and mismatch of the data model which is used by the parameter estimator are often...
Multipath signal propagation is the defining characteristic of terrestrial wireless channels. Virtually all existing statistical models for wireless channels are implicitly based on the assumption of rich multipath, which can be traced back to the seminal works of Bello and Kennedy on the wide-sense stationary uncorrelated scattering model, and more recently to the i.i.d. model for multi-antenna channels...
In this paper, we present a comparative study of the performance of the joint time of arrival/direction of arrival (TOA/DOA) estimation techniques - estimation of signal parameters via rotational invariance technique (ESPRIT), joint angle and delay estimation (JADE) and space-alternating generalised expectation maximisation (SAGE) - in the context of a strong multipaths model. We focus on a number...
A maximum likelihood (ML) estimator is developed for determining time delays in multipath acoustic channel in the presence of uncorrelated noise. The performance of the ML estimator is compared with a generalized autocorrelation estimator (GAE) and Cramer-Rao lower bound (CRLB) for resolvable multipath, via computer simulation. Simulation results show that the performance of the ML estimator is superior...
OFDM is a promising high-speed data transmission platform, and wireless OFDM LAN/MAN has rapidly developed since some OFDM network technologies were standardized. In this paper, the wireless OFDM LAN/MAN topological structures are described, and a novel symbol time error and channel estimation algorithm for the wireless OFDM LAN/MAN based on the PSD estimation is presented. The results of simulation...
Channel estimation is vital for implementing schemes such as coherent detection and adaptive bit loading, which make OFDM an attractive PHY layer technology for vehicular wireless communications. However, knowledge of the exact time of arrival (TOA) information of the multi-path components of the vehicular wireless channel is required to achieve efficient channel estimation. Super-resolution algorithms...
Sparse multi-path channels (MPC) are often encountered in several wireless communications. Exploiting the sparse property of MPC, several estimation methods have been proposed in recent years. Unlike the previous methods based on either dense MPC or sparse MPC models, we propose a novel MPC estimation method based on a generalized hybrid MPC model. The existed least squares (LS) and sparse component...
Orthogonal frequency division multiplexing based on offset quadrature amplitude modulation (OFDM-OQAM) over wideband frequency selective multipath channels suffers from inter-symbol interference (ISI) and inter-carrier interference (ICI) that degrade its performance. Channel estimation and equalization are needed to combat these interferences. In this paper a novel channel estimator for passband OFDM-OQAM...
Training-based channel estimation involves probing of the channel in time, frequency, and space by the transmitter with known signals, and estimation of channel parameters from the output signals at the receiver. Traditional training-based methods, often comprising of maximum likelihood estimators, are known to be optimal under the assumption of rich multipath channels. Numerous measurement campaigns...
This contribution deals with the Turbo-like noncoherent data-aided (e.g., no blind) synchronization of Ultra-Wideband Impulse-Radio (UWB-IR) terminals operating over broadband channels affected by multipath fading with ??a priori?? unknown number of paths. The synchronizer we develop achieves the data-aided joint estimate of the number of paths and their arrival times without requiring any a priori...
The on-line Bayesian Cramer-Rao (BCRB) lower bound for the dynamic estimation of a time-varying multi-path Rayleigh channel in 4-QAM OFDM system is considered. In case of negligible channel variation within one symbol and delay related information, true BCRB for data-aided (DA) context, and two closed-form expressions for non-data aided (NDA) context are derived.
We develop a novel channel estimation technique for uplink multicarrier code division multiple access (MC-CDMA) systems in this paper. First, the pilot strategy to effectively shift multiple channels into non-overlapped regions is employed. Second, the proposed scheme estimates the channel parameters including the number of channel taps and multipath time delays via Hannan-Quinn (HQ) criterion. Third,...
To investigate the blind symbol rate estimation of any linear base-band digital modulation scheme with square root raised cosine filter, an algorithm based on cyclic correlation and Haar wavelet transform estimator is proposed. First we use FFT to estimate the bandwidth roughly. Then we set the sampling frequency and range scale of wavelet transform according to bandwidth. Using the signals filtered...
In this paper, an optimal signal-to-noise ratio (SNR) which is independent from correlation-interval and mobile speed is analyzed, which is on the basis of the channel auto-correlation Doppler shift estimation algorithm. And then an optimized SNR tracking (OSNRT) algorithm on the basis of Rake receiver under multi-path fading channel is proposed. The improved algorithm calculated Doppler shift by...
A novel timing offset estimator for orthogonal frequency division multiplexing (OFDM) systems is proposed. The estimator is a modification to Schmidl method by a kind of new preamble. The performance of the estimator is presented in terms of mean and variance by simulation in multipath fading channel. The results show that the proposed estimator has smaller variance than Schmidl and Minn's estimators,...
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...
In this paper, a parametric channel estimation algorithm applicable to uplinks of orthogonal frequency division multiple access (OFDMA) systems whose subcarriers are pseudo-randomly allocated is proposed. By exploiting pilot hopping, estimation of signal parameters via rotational invariance technique (ESPRIT) is employed to estimate the path delays of the sparse multipath fading channel. From the...
Coherent data communication over doubly-selective channels requires that the channel response be known at the receiver. Training-based schemes, which involve probing of the channel with known signaling waveforms and processing of the corresponding channel output to estimate the channel parameters, are commonly employed to learn the channel response in practice. Conventional training-based methods,...
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...
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