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We consider the uplink of a DS-CDMA system and we assume that the base station is endowed with a linear antenna array. Transmission takes place over a multipath channel and the goal is to estimate the channel parameters and the directions... more
We consider the uplink of a DS-CDMA system and we assume that the base station is endowed with a linear antenna array. Transmission takes place over a multipath channel and the goal is to estimate the channel parameters and the directions of arrival of the signals from a user entering the network. Maximum likelihood estimation of all these parameters is not feasible as it involves a search over a multidimensional domain. Through suitable approximations we replace the above search by a sequence of mono-dimensional searches. This results in an estimation algorithm of reasonable complexity of third-generation cellular applications. The performance of the algorithm is assessed by simulation in a scenario inspired by the specification of the FDD component of the UMTS standard. It is found that the channel parameters and the directions of arrival can be estimated with accuracy close to the Cramer-Rao bound.
Research Interests: Sensor Arrays, Parameter estimation, Antenna arrays, Cramer Rao Lower Bound, Maximum Likelihood, and 8 moreMaximum Likelihood Estimation, Spread Spectrum Communication, Antenna Array, Code Division Multiple Access, Base station, Direction of arrival, maximum likelihood estimate, and Multipath channel
Research Interests: Distributed Computing, Synchronization, Algorithm, Parameter estimation, Simulation, and 15 moreSampling methods, Impulse Radio, Frequency, Shape, Implementation, Least Mean Square, Sampling Rate, Ultra Wideband, Analog to Digital Conversion, Electrical And Electronic Engineering, Time of Arrival, Impulse, Synchronisation, Multipath channel, and Ultra wide band
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This paper discusses a ranging algorithm appropriate for impulse radio ultra-wideband signals compliant with the IEEE 802.15.4a standard. Three steps are indicated to locate the so-called ranging marker in the received signal. The first... more
This paper discusses a ranging algorithm appropriate for impulse radio ultra-wideband signals compliant with the IEEE 802.15.4a standard. Three steps are indicated to locate the so-called ranging marker in the received signal. The first is to find the highest peaks in the channel responses to the transmitted pulses. The second consists in measuring the distance of each peak to the
Research Interests: Distributed Computing, Localization, Algorithm, Parameter estimation, Sampling methods, and 14 moreImpulse Radio, Physical Layer, Accuracy, Implementation, Sampling Rate, Precision, Radio Wave, Signal to Noise Ratio, Ultra Wideband, Pulse Modulation, Electrical And Electronic Engineering, Time measurement, Impulse, and Ultra wide band
ABSTRACT The time-division duplex (TDD) component of the universal mobile telecommunications system (UMTS) employs synchronous code-division multiple-access techniques with orthogonal spreading codes to provide protection against... more
ABSTRACT The time-division duplex (TDD) component of the universal mobile telecommunications system (UMTS) employs synchronous code-division multiple-access techniques with orthogonal spreading codes to provide protection against cochannel interference. In the presence of multipath propagation, however, the code orthogonality is lost and multiaccess interference is generated at the receiver. In such conditions, an estimate of the channel impulse response is required for reliable detection. In this paper, we propose and compare two pilot-assisted schemes for channel estimation in the downlink of the UMTS-TDD system. Both algorithms also provide estimates of the users' energies, which are needed to perform multiuser detection. Theoretical analysis and computer simulations are used to assess the channel estimation performance in terms of mean-squared errors and bit-error rate. It is shown that the accuracy of the proposed estimators attains the Cramer-Rao bound at intermediate/high signal-to-noise ratios.
Research Interests: Channel Estimation, Computer Simulation, Mean square error, Cramer Rao Lower Bound, Multiuser Detection, and 12 moreBit Error Rate, Theoretical Analysis, Maximum Likelihood Estimation, Signal to Noise Ratio, Time Division Multiplexing, Channel Impulse Response (CIR), Code Division Multiple Access, Electrical And Electronic Engineering, Universal Mobile Telecommunications System, Downlink, Multipath Propagation, and Time Division Duplex
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This paper investigates timing recovery for differential transmitted reference (DTR) ultra-wideband receivers. In DTR systems the symbol energy is distributed over several time slots (frames) and a single pulse is transmitted per frame.... more
This paper investigates timing recovery for differential transmitted reference (DTR) ultra-wideband receivers. In DTR systems the symbol energy is distributed over several time slots (frames) and a single pulse is transmitted per frame. The information is conveyed by differentially encoding the pulse polarities. Equal polarities correspond to a bit +1 while alternate polarities correspond to a bit -1. The detector
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This paper deals with channel estimation in the uplink of a direct-sequence code-division multiple-access system operating in a multipath environment. The parameters of interest are the delays and the complex attenuations incurred by the... more
This paper deals with channel estimation in the uplink of a direct-sequence code-division multiple-access system operating in a multipath environment. The parameters of interest are the delays and the complex attenuations incurred by the signal echoes along the propagation paths. We propose an iterative approach for estimating the channel parameters of a new user entering the system. The method is
Research Interests: Distributed Computing, Iterative Methods, Fading Channel, Optimization Problem, Channel Estimation, and 8 moreComputer Simulation, Cramer Rao Lower Bound, Spread Spectrum Communication, Code Division Multiple Access, Electrical And Electronic Engineering, Fading channels, Multiuser Interference (MUI), and Direct sequence
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Research Interests: Network Analysis, Modulation, Simulation, Computer Simulation, Phase Synchronization, and 10 morePulse Shaping, Minimum shift keying, Frequency Modulation, Indexation, Phase Modulation, Clock & Data Recovery, Electrical And Electronic Engineering, Monte Carlo Method, Viterbi Decoding, and Viterbi Decoder
This paper analyzes the performance of a decision-directed tracking system for the carrier reconstruction in SSB data transmission systems using no carrier or pilot tone. A formula is obtained which relates the phase-error variance to (1)... more
This paper analyzes the performance of a decision-directed tracking system for the carrier reconstruction in SSB data transmission systems using no carrier or pilot tone. A formula is obtained which relates the phase-error variance to (1) the noise level at the receiver input, (2) the channel characteristics, and (3) the relevant system parameters. It is found that the system performance compares very well with that of a conventional scheme where an attenuated carrier is transmitted.
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The authors investigate the tracking performance of two popular synchronization schemes used for clock and carrier recovery in trellis-code modulated signals. Clock extraction is accomplished by squaring and then filtering the incoming... more
The authors investigate the tracking performance of two popular synchronization schemes used for clock and carrier recovery in trellis-code modulated signals. Clock extraction is accomplished by squaring and then filtering the incoming signal with a narrow bandpass filter tuned to the nominal symbol rate. Phase recovery is achieved by means of a decision-directed loop wherein an error voltage, derived from the signal samples and the decoder decisions, is used to update the current estimate of the carrier phase. The standard of comparison is the performance of the same synchronizers when operating with uncoded signals. The main result is that good codes do not affect the tracking operation of the synchronizers. More generally, sufficient conditions are given for the tracking behavior to be code-independent
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This paper describes detection algorithms for coded and uncoded M-PSK signals transmitted over frequency-flat fading channels. Fading distortion is estimated with per-survivor methods using the outputs of two receive filters. The proposed... more
This paper describes detection algorithms for coded and uncoded M-PSK signals transmitted over frequency-flat fading channels. Fading distortion is estimated with per-survivor methods using the outputs of two receive filters. The proposed algorithms do not require information on the fading statistics and are dubbed blind algorithms. The error-rate performance is assessed by simulation for uncoded and trellis-coded PSK and is
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... For instance, g(t) could be approximated by an adaptive equalizer, Page 6. MU1 ANDMODESTINO: DPSK WITH CONVOLUTIONAL ENCODING 1079 while -&i) is an iid sequence of zero-mean Gaussian variates with common variance E{iF,Zi*} =... more
... For instance, g(t) could be approximated by an adaptive equalizer, Page 6. MU1 ANDMODESTINO: DPSK WITH CONVOLUTIONAL ENCODING 1079 while -&i) is an iid sequence of zero-mean Gaussian variates with common variance E{iF,Zi*} = E{aiai*} - E{ZZ*} = (1 - p)ua2. ...
Research Interests: Algorithms, Convergence, Synchronization, Stability, Parameter estimation, and 11 moreSampling methods, Mean square error, Mathematical Models, Convergence Rate, Root-Mean Square Error, Maximum Likelihood Estimation, Steady state, Mathematical Model, Electrical And Electronic Engineering, maximum likelihood estimate, and Phase control
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A general analysis is provided for the jitter performance of a delay clock regenerator as a function of various system parameters such as modulation format, channel filtering, signal-to-noise ratio, and line delay. The novelty with... more
A general analysis is provided for the jitter performance of a delay clock regenerator as a function of various system parameters such as modulation format, channel filtering, signal-to-noise ratio, and line delay. The novelty with respect to previous works on the same subject is that we find an expression for the jitter variance of the regenerated clock, while other studies
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Computer simulation is employed to assess jitter performance of a clock recovery circuit as a function of the characteristics of the rectifier being used. Several types of rectifiers are compared, some operating at baseband, others at... more
Computer simulation is employed to assess jitter performance of a clock recovery circuit as a function of the characteristics of the rectifier being used. Several types of rectifiers are compared, some operating at baseband, others at intermediate frequency (IF). It is shown that the best choice between them depends both on the modulation format and on the excess bandwidth factor
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Two signaling formats for ultrawide bandwidth indoor communications are compared in terms of bit error rate performance in the presence of multiple access interference. The channel exhibits multipath propagation and its impulse response... more
Two signaling formats for ultrawide bandwidth indoor communications are compared in terms of bit error rate performance in the presence of multiple access interference. The channel exhibits multipath propagation and its impulse response is either assumed known or is estimated with least squares methods. Computer simulations show that, even with perfect channel knowledge, time-hopping pulse-amplitude modulation is superior to time-hopping
Research Interests: Channel Estimation, Computer Simulation, Impulse response, Broadband Networks, Pulse Amplitude Modulation, and 11 moreBit Error Rate, BER, Multiple-access Interference, Performance Comparison, Transient Response, Bandwidth, Pulse Modulation, Least Square Method, Time Hopping, Least squares method, and Multipath Propagation
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