Sam Reisenfeld

A new algorithm for the estimation of the frequency of a complex exponential in additive Gaussian noise

The letter presents a new algorithm for the precise estimation of the frequency of a complex exponential signal in additive, complex, white Gaussian noise. The discrete Fourier transform (DFT)-based algorithm performs a frequency interpolation on the results of an N point complex fast Fourier transform. For large N and large signal to noise ratio, the frequency estimation error variance obtained is 0.063 dB above the Cramer-Rao bound. The algorithm has low computational complexity and is well suited for real time digital signal processing applications, including communications, radar and sonar.

Bayesian Tracking in Cooperative Localization for Cognitive Radio Networks

In this paper we consider cooperative localization and tracking of primary users (PU) in a cognitive radio network using Bayesian techniques. We use particle filtering methods to track the location of a PU in the network using cooperative localization techniques and present some results for noisy measurements. The cognitive radio (CR) nodes estimate the information related to the geographical position of the PU based on existing location identification and localization techniques and forward the noisy information to a cognitive radio base station (CRB), which then fuses the information to estimate the position of the PU in the network in order to perform a radio scene analysis. We propose a particle filtering approach that is suitable for tracking Gaussian and non-Gaussian noisy signals at the CRB to estimate the position of a PU, two importance-functions relative to the particle filtering algorithm are also presented. Simulations are performed on the proposed tracking algorithm and the results are presented in terms of the mean squared error of the positional estimates.

Frequency jitter of a digital phase-locked loop and comparison with a modified CRB

The steady state (SS) noise performance of a digital phase locked loop (DPLL) is of very much interest, while tracking carrier signals. In the literature the SS performance is very well examined in terms of the SS phase jitter, however the SS frequency jitter of a DPLL is unexamined up to now. In this paper we analyse the SS performance of a DPLL in terms of the frequency jitter. We derive a linearised expression for the SS frequency jitter of a DPLL, and verify it by simulations.

Detect and Avoid for UWB-WiMedia: Performance bounds of signal sensing

Detect and avoid (DAA) is a simple cognitive radio technique for the coexistence of a primary user and secondary users sharing the same spectrum. Critical to DAA implementation is a detection system which must provide both rapid and accurate decisions on the presence/absence of primary user transmission. In this work, performance results for both energy sensing and waveform sensing are presented in the context of UWB (ultra-wideband) WiMedia and WiMAX coexistence. These results provide upper and lower bounds on the decision error rate performance of sensing systems as a function of SNR (signal-to-noise ratio) and the number of samples used in the sensing decision. The bounds represent benchmarks on the performances of practical detection systems and give insight into the trade-off between sensing performance and processing time.

Performance analysis of a correlator based maximum likelihood frequency estimator

In this paper we discuss the performance of a correlator based frequency estimator (CE). The estimator is statistically analysed for single-tone frequency estimation for an additive white Gaussian noise (AWGN) channel. The CE is a maximum likelihood estimator (ML) S. M. Kay (1993) which theoretically achieves the Cramer-Rao lower bound (CRB) S. M. Kay (1993) if properly implemented. Frequency estimates on the received single-tone signal are made by correlating the received signal with a locally generated signal by varying the frequency, and maximizing the energy at the output of the correlator. The statistical distribution of the frequency estimates, made by the CE is studied; we consider four different cases as discussed in the paper for the distribution, whilst providing simulation results to verify the analysis.

Phase detector models and their performances for IF/baseband frequency recovery for complex envelope based DSP implemented PLL

This paper discusses four phase detector (PD) models that could be used in DSP implemented phase locked loops (PLL) for frequency recovery at intermediate frequency (IF) or at baseband. The PD models, which are nonlinear functions in general, can be easily implemented in DSP. The steady state and the acquisition performances of the PD models are discussed and compared with each other, and the noise statistics are explored by means of computer experiments and numerical analysis.

Performance analysis of a Digital Phase-Locked Loop with a Hyperbolic Nonlinearity

The treatment of phase locked loops (PLL) has been heavily looked into over the past several decades on its performances and analysis, and is a very old topic. However the usage of it has never been reduced with the rapid evolvement of various open loop and closed loop systems. In this paper we analyse the performance of an arctan based digital phase locked loop (DPLL) with a hyperbolic nonlinearity for single-tone carrier tracking. We purposely introduce the nonlinearity for improved performance of the closed loop system. We look at the acquisition performance of the DPLL by considering the phase plane portrait and the lock-in range of the loop. The steady state (SS) performance of the loop is analysed by considering the open loop SS statistical distribution of the phase noise

DSP based symbol timing estimation techniques

This paper presents three symbol timing estimation techniques, using DSP (digital signal processing) methods. The techniques are easily implemented on digital signal processors or FPGAs (field programmable gate arrays). Two feedforward techniques and one feedback technique are presented. The relative performances of the techniques are compared, and the advantages and the disadvantages of the techniques are discussed as well.

Frequency tracking and acquisition with a four-quadrant arctan phase detector based digital phase locked loop

This paper discusses the performance of tracking and acquiring a single frequency sinusoid with a four-quadrant phase detector (PD) based digital phase locked loop (DPLL). Under tracking we analyse the open loop steady state phase error distribution of the DPLL at the output of the PD and the output phase noise. Acquisition is treated as a complete linear process under noise free conditions and the performance degradation is studied using computer experiments.

Energy efficient cooperative HAP-terrestrial communication systems

In this paper we study the energy efficiency of hybrid high altitude platform (HAP) and terrestrial communication systems in the uplink. The applications of HAPs in the recent years have gained significant interest especially for telecommunications. A cooperative relay based communication strategy on the ground with a single source-relay pair is considered for the hybrid HAP-terrestrial system. We show that cooperation on ground between the terrestrial terminals could improve the energy efficiency in the uplink depending on the temporal behavior of the channels. Thus by having cognitive context aware capabilities in the ground terminals one could exploit the spatial domain to improve the energy efficiency. The energy efficiency can be further improved by means of proper power allocation between the terrestrial source and relay nodes. We consider the decode and forward based cooperative system for our study with a constraint on the overall bit error probability to achieve a predefined quality of service. Results show that considerable gain in the energy can be attained by exploiting the spatial domain by means of cooperation.