Performance Evaluation of Adaptive Continuous Wavelet Transform based Rake Receiver for UWB Systems

This paper proposes an adaptive continuous wavelet transform (ACWT) based Rake receiver to mitigate interference for high speed ultra wideband (UWB) transmission. The major parts of the receiver are least mean square (LMS) adaptive equalizer and N-selective maximum ratio combiner (MRC). The main advantage of using continuous wavelet rake receiver is that it utilizes the maximum bandwidth (7.5GHz) of the UWB transmitted signal, as announced by the Federal Communication Commission (FCC). In the proposed ACWT Rake receiver, the weights and the finger positions are updated depending upon the convergence error over a period in which training data is transmitted. Line of sight (LOS) channel model (CM1 from 0 to 4 meters) and the Non line of sight (NLOS) channel models (CM, CM3 and CM4) are the indoor channel models selected for investigating in this research . The performance of the proposed adaptive system   is evaluated by comparing with conventional rake and continuous wavelet transform (CWT) based rake. It showed an improved performance in all the different UWB channels (CM1 to CM4) for rake fingers of 2, 4 and 8. Simulations showed that for 8 rake fingers, the proposed adaptive CWT rake receiver has shown an SNR improvement of 2dB, 3dB, 10dB and 2dB respectively over CWT rake receiver in different UWB channels CM1, CM2, CM3 and CM4

Analyzing Code Tracking Algorithms for Galileo Open Service Signal

The ever-increasing public interest on location and positioning services has originated a demand for higher performance Global Navigation Satellite Systems (GNSSs). Galileo Open Service (OS) signal, part of the European contribution to future GNSS, was designed to respond to the above demand. In all GNSSs, the estimation with high accuracy of the Line-Of-Sight (LOS) delay is a prerequisite. The Delay Lock Loops (DLLs) and their enhanced variants (i.e., feed-back code tracking loops) are the structures of choice for the commercial GNSS receivers, but their performance in severe multipath scenarios is still rather limited. In addition, the new satellite positioning system proposals specify the use of a new modulation, the Binary Offset Carrier (BOC) modulation, which triggers a new challenge in the code tracking stage. Therefore, in order to meet this emerging challenge and to improve the accuracy of the delay estimation in severe multipath scenarios, this thesis analyzes feed-back as well as feed-forward code tracking algorithms and proposes a novel algorithm, namely Peak Tracking (PT), which is a combination of both feed-back and feed-forward structures and utilizes the advantages inherent in these structures. In this thesis, the code tracking algorithms are studied and analyzed for Sine BOC (SinBOC) modulated Galileo OS signal for various multipath profiles in Rayleigh fading channel model. The performance of the analyzed algorithms are measured in terms of various well-known criteria such as Root-Mean-Square-Error (RMSE), Mean-Time-to-Lose Lock (MTLL), delay error variance and Multipath Error Envelopes (MEEs). The simulation results show that the proposed PT algorithm outperforms all other analyzed algorithms in various multipath profiles in good Carrier-to-Noise-Ratios (CNRs). The simulation results are compared with the theoretical Cramer-Rao Bound (CRB) and the comparison shows that the delay error variance for PT algorithm approaches the theoretical limit with the increase in CNR. Therefore, the proposed algorithm can be considered as an excellent candidate for implementation in future Galileo receivers, especially when tracking accuracy is a concern. /Kir1

Adaptive PN code synchronisation in DS-CDMA systems

Spread Spectrum (SS) communication, initially designed for military applications, is now the basis for many of today's advanced communications systems such as Code Division Multiple Access (CDMA), Global Positioning System (GPS), Wireless Local Loop (WLL) , etc. For effective communication to take place in systems using SS modulation, the Pseudo-random Noise (PN) code used at the receiver to despread the received signal must be identical and be synchronised with the PN code that was used to spread the signal at the transmitter. Synchronisation is done in two steps: coarse synchronisation or acquisition, and fine synchronisation or tracking. Acquisition involves obtaining a coarse estimate of the phase shift between the transmitted PN code and that at the receiver so that the received PN code will be aligned or synchronised with the locally generated PN code. After acquisition, tracldng is now done which involves maintaining the alignment of the two PN codes. This thesis presents results of the research calTied out on a proposed adaptive PN code acquisition circuit designed to improve the synchronisation process in Direct Sequence CDMA (DS-CDMA) systems. The acquisition circuit is implemented using a Matched Filter (MF) for the correlation operation and the threshold setting device is an adaptive processor known as the Cell Averaging Constant False Alarm Rate (CA-CFAR) processor. It is a double dwell acquisition circuit where the second dwell is implemented by Post Detection Integration (PDI). Depending on the application, PDI can be used to mitigate the effect of frequency offset in non-coherent detectors and/or in the implementation of multiple dwell acquisition systems. Equations relating the performance measures - the probability of false alarm (Pra ), the probability of detection (P d) and the mean acquisition time (E {Tacq}) - of the circuit are deri ved. Monte Carlo simulation was used for the independent validation of the theoretical results obtained, and the strong agreement between these results shows the accuracy of the derived equations for the proposed circuit. Due to the combination of PDI and CA-CFAR processor in the implementation of the circuit, results obtained show that it can provide a good measure of robustness to frequency offset and noise power variations in mobile environment, consequently leading to improved acquisition time performance. The complete synchronisation circuit is realised by using this circuit in conjunction with a conventional code tracking circuit. Therefore, a study of a Non-coherent Delay-Locked Loop (NDLL) code tracking circuit is also calTied out.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Adaptive PN code synchronisation in DS-CDMA systems.

Spread Spectrum (SS) communication, initially designed for military applications, isnow the basis for many of today's advanced communications systems such as CodeDivision Multiple Access (CDMA), Global Positioning System (GPS), Wireless LocalLoop (WLL) , etc. For effective communication to take place in systems using SSmodulation, the Pseudo-random Noise (PN) code used at the receiver to despread thereceived signal must be identical and be synchronised with the PN code that was used tospread the signal at the transmitter. Synchronisation is done in two steps: coarsesynchronisation or acquisition, and fine synchronisation or tracking. Acquisitioninvolves obtaining a coarse estimate of the phase shift between the transmitted PN codeand that at the receiver so that the received PN code will be aligned or synchronisedwith the locally generated PN code. After acquisition, tracldng is now done whichinvolves maintaining the alignment of the two PN codes.This thesis presents results of the research calTied out on a proposed adaptive PN codeacquisition circuit designed to improve the synchronisation process in Direct SequenceCDMA (DS-CDMA) systems. The acquisition circuit is implemented using a MatchedFilter (MF) for the correlation operation and the threshold setting device is an adaptiveprocessor known as the Cell Averaging Constant False Alarm Rate (CA-CFAR)processor. It is a double dwell acquisition circuit where the second dwell isimplemented by Post Detection Integration (PDI). Depending on the application, PDIcan be used to mitigate the effect of frequency offset in non-coherent detectors and/or inthe implementation of multiple dwell acquisition systems. Equations relating theperformance measures - the probability of false alarm (Pra ), the probability of detection (P d) and the mean acquisition time (E {Tacq}) - of the circuit are deri ved. Monte Carlosimulation was used for the independent validation of the theoretical results obtained,and the strong agreement between these results shows the accuracy of the derivedequations for the proposed circuit. Due to the combination of PDI and CA-CFARprocessor in the implementation of the circuit, results obtained show that it can providea good measure of robustness to frequency offset and noise power variations in mobileenvironment, consequently leading to improved acquisition time performance. Thecomplete synchronisation circuit is realised by using this circuit in conjunction with aconventional code tracking circuit. Therefore, a study of a Non-coherent Delay-LockedLoop (NDLL) code tracking circuit is also calTied out