6 research outputs found

    Novel self-decorrelation and fractional self-decorrelation pre-processing techniques to enhance the output SINR of single-user-type DS-CDMA detectors in blind space-time RAKE receivers.

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    Cheung Shun Keung.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 80-83).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- The Problem --- p.1Chapter 1.2 --- Overview of CDMA --- p.2Chapter 1.3 --- Problems Encountered in Direct-Sequence (DS)CDMA --- p.3Chapter 1.3.1 --- Multipath Fading Scenario in DS-CDMA Cellular Mo- bile Communication --- p.3Chapter 1.3.2 --- Near-Far Problem --- p.4Chapter 1.4 --- Delimitation and Significance of the Thesis --- p.5Chapter 1.5 --- Summary --- p.7Chapter 1.6 --- Scope of the Thesis --- p.8Chapter 2 --- Literature Review of Blind Space-Time Processing in a wire- less CDMA Receiver --- p.9Chapter 2.1 --- General Background Information --- p.9Chapter 2.1.1 --- Time Model of K-User Chip-Synchronous CDMA --- p.9Chapter 2.1.2 --- Dispersive Channel Modelling --- p.10Chapter 2.1.3 --- Combination of K-user CDMA Time Model with the Slow Frequency-Selective Fading Channel Model to form a completed Chip-Synchronous CDMA Time Model --- p.13Chapter 2.1.4 --- Spatial Channel Model with Antenna Array [9] --- p.15Chapter 2.1.5 --- Joint Space-Time Channel Model in Chip-Synchronous CDMA --- p.19Chapter 2.1.6 --- Challenges to Blind Space-Time Processing in a base- station CDMA Receiver --- p.23Chapter 2.2 --- Literature Review of Single-User-Type Detectors used in Blind Space-Time DS-CDMA RAKE Receivers --- p.25Chapter 2.2.1 --- A Common Problem among the Signal Processing Schemes --- p.28Chapter 3 --- "Novel ""Self-Decorrelation"" Technique" --- p.29Chapter 3.1 --- "Problem with ""Blind"" Space-Time RAKE Processing Using Single- User-Type Detectors" --- p.29Chapter 3.2 --- "Review of Zoltowski & Ramos[10,11,12] Maximum-SINR Single- User-Type CDMA Blind RAKE Receiver Schemes" --- p.31Chapter 3.2.1 --- Space-Time Data Model --- p.31Chapter 3.2.2 --- The Blind Element-Space-Only (ESO) RAKE Receiver with Self-Decorrelation Pre-processing Applied --- p.32Chapter 3.3 --- Physical Meaning of Self-Decorrelation Pre-processing --- p.35Chapter 3.4 --- Simulation Results --- p.38Chapter 4 --- """Fractional Self-Decorrelation"" Pre-processing" --- p.45Chapter 4.1 --- The Blind Maximum-SINR RAKE Receivers in Chen et. al.[l] and Wong et. al.[2] --- p.45Chapter 4.2 --- Fractional Self-Decorrelation Pre-processing --- p.47Chapter 4.3 --- The Blind Element-Space-Only (ESO) RAKE Receiver with Fractional Self-Decorrelation Pre-processing Applied --- p.50Chapter 4.4 --- Physical Meaning of Fractional Self-Decorrelation Pre-processing --- p.54Chapter 4.5 --- Simulation Results --- p.55Chapter 5 --- Complexity Analysis and Schematics of Proposed Techniques --- p.64Chapter 5.1 --- Computational Complexity --- p.64Chapter 5.1.1 --- Self-Decorrelation Applied in Element-Space-Only (ESO) RAKE Receiver --- p.64Chapter 5.1.2 --- Fractional Self-Decorrelation Applied in Element-Space- Only (ESO) RAKE Receiver --- p.67Chapter 5.2 --- Schematics of the Two Proposed Techniques --- p.69Chapter 6 --- Summary and Conclusion --- p.74Chapter 6.1 --- Summary of the Thesis --- p.74Chapter 6.1.1 --- The Self-Decorrelation Pre-processing Technique --- p.75Chapter 6.1.2 --- The Fractional Self-Decorrelation Pre-processing Tech- nique --- p.76Chapter 6.2 --- Conclusion --- p.78Chapter 6.3 --- Future Work --- p.78Bibliography --- p.80Chapter A --- Generalized Eigenvalue Problem --- p.84Chapter A.1 --- Standard Eigenvalue Problem --- p.84Chapter A.2 --- Generalized Eigenvalue Problem --- p.8

    Bearing estimation techniques for improved performance spread spectrum receivers

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    The main topic of this thesis is the use of bearing estimation techniques combined with multiple antenna elements for spread spectrum receivers. The motivation behind this work is twofold: firstly, this type of receiver structure may offer the ability to locate the position of a mobile radio in an urban environment. Secondly, these algorithms permit the application of space division multiple access (SDMA) to cellular mobile radio, which can offer large system capacity increases. The structure of these receivers may naturally be divided into two parts: signal detection and spatial filtering blocks. The signal detection problem involves locating the bearings of the multipath components which arise from the transmission of the desired user’s signal. There are a number of approaches to this problem, but here the MUSIC algorithm will be adopted. This algorithm requires an initial estimate of the number of signals impinging on the receiver, a task which can be performed by model order determination techniques. A major deficiency of MUSIC is its inability to resolve the highly–correlated and coherent multipath signals which frequently occur in a spread spectrum system. One of the simplest ways to overcome this problem is to employ spatial smoothing techniques, which trade the size of the antenna array for the ability to resolve coherent signals. The minimum description length (MDL) is one method for determining the signal model order and it can easily be extended to calculating the required degree of spatial smoothing. In this thesis, an approach to analysing the probability of correct model order determination for the MDL with spatial smoothing is presented. The performance of MUSIC, combined with spatial smoothing, is also of great significance. Two smoothing algorithms, spatial smoothing and forward–backward spatial smoothing, are analysed to compare their performance. If SDMA techniques are to be deployed in cellular systems, it is important to first estimate the performance improvements available from applying antenna array spatial filters. Initially, an additive white Gaussian noise channel is used for estimating the capacity of a perfect power–controlled code division multiple access system with SDMA techniques. Results suggest that the mean interference levels are almost halved as the antenna array size doubles, permitting large capacity increases. More realistic multipath models for urban cellular radio channels are also considered. If the transmitter gives rise to a number of point source multipath components, the bearing estimation receiver is able to capture the signal energy of each multipath. However, when a multipath component has significant angular spread, bearing estimation receivers need to combine separate directional components, at an increased cost in complexity, to obtain similar results to a matched filter. Finally, a source location algorithm for urban environments is presented, based on bearing estimation of multipath components. This algorithm requires accurate knowledge of the positions of the major multipath reflectors present in the environment. With this knowledge it is possible to determine the position of a transmitting mobile unit. Simulation results suggest that the algorithm is very sensitive to angular separation of the multipath components used for the source location technique

    Wireless Positioning Applications in Multipath Environments

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    Funklokalisierung in der Umgebung mit der Mehrwegeausbreitung In den vergangenen Jahren wurde zunehmend Forschung im Bereich drahtlose Sensornetzwerk (engl. „Wireless Sensor Network“) betrieben. Lokalisierung im Innenraum ist ein vielversprechendes Forschungsthema, das in den Literaturen vielfĂ€ltig diskutiert wird. Jedoch berĂŒcksichtigen die meisten Arbeiten einen wichtigen Faktor nicht, nĂ€mlich die Mehrwegeausbreitung, welche die Genauigkeit der Lokalisierung beeinflusst. Diese Arbeit bezieht sich auf Lokalisierungsanwendungen in UWB (Ultra-Breitband-Technologie)- und WLAN (drahtloses lokales Netzwerk)- Systemen im Fall von Mehrwegeausbreitung. Zur Steigerung der Robustheit der Lokalisierungsanwendungen bei Mehrwegeausbreitung wurden neuartige Lokalisierungsalgorithmen, die auf der Auswertung der Ankunftszeit (engl. „Time of Arrival“, ToA), der empfangenen SignalstĂ€rke (engl. „Received Signal Strength“, RSS) und dem Einfallswinkel (engl. „Angle of Arrival“, AoA) basieren, vorgestellt und untersucht. Bei Mehrwegeausbreitung ist die Fragen den direkten Pfad zu lösen, da der direkte Pfad (engl. „Direct Path“, DP) schwĂ€cher als anderer Pfad sein kann. In dieser Arbeit werden daher neuartige Algorithmen zur Flankendetektion der empfangenen Signale fĂŒr UWB Systeme entwickelt, um die Positionsbestimmung zu verbessern: Es gibt die kooperative Flankendetektion (engl. „Joint Leading Edge Detection“, JLED), die erweiterte maximalwahrscheinlichkeitbasierte KanalschĂ€tzung (engl. „Improved Maximum Likelihood Channel Estimation“, IMLCE) und die Flankendetektion mit untervektorraumbasiertem Verfahren (engl. „Subspace based Approaches“, SbA). Bei der kooperativen Flankendetektion werden zwei Kriterien herangezogen nĂ€mlich die minimale FlĂ€che und das minimale mittlere Quadrat des SchĂ€tzfehlers (engl. „Minimum Mean Squared Error“, MMSE). Weiterhin wird ein monopulsbasierter KanalschĂ€tzer (engl. „Monopulse based Channel Estimator“, MCE) entwickelt, um die möglicherweise falsche Kombinationen der Flanken (engl. „Leading Edge Combination“, LEC) auszuschließen. Zudem wird in der Arbeit der erweiterte MLCE vorgestellt, der aus einem groben und einem genauen SchĂ€tzungsschritt besteht. Bei dem neuartigen untervektorraumbasierten Verfahren werden ein statischer und ein Schwundkanal untersucht. Im ersten Fall wird die Kombination der RĂŒckwĂ€rtssuchalgorithmus mit untervektorraumbasierten Verfahren untersucht. Zudem wird im zweiten Fall ein untervektorraumbasierte Verfahren im Frequenzbereich vorgestellt. FĂŒr die RSS-basierte Lokalisierung wird ein Fingerabdruckverfahren (engl. „Fingerprint Approach“) und ein neuartiger EntfernungsschĂ€tzer basierend auf der Kanalenergie entwickelt und implementiert. Schließlich wird in der Arbeit ein Lokalisierungssystem mit WinkelschĂ€tzern inklusive einer entsprechenden Kalibrierung auf einer 802.11a/g Hardwareplattform vorgestellt. Dazu wird ein neuartiger TrĂ€gerschĂ€tzer und KanalschĂ€tzer entwickelt.In the past several years there has been more growing research on Wireless Sensor Network (WSN). The indoor localization is a promising research topic, which is discussed variously in some literatures. However, the most work does not consider an important factor, i.e. the multi-path propagation, which affects the accuracy of the indoor localization. This work dealt with the indoor localization applied in UWB (Ultra Wide Band) and WLAN (Wireless Local Area Network) systems in the case of multi-path propagation. To improve the robustness of the applications of localization in the case of multi-path propagation, novel localization algorithms based on the evaluation of the Time of Arrival (ToA), the Received Signal Strength (RSS) and the Angle of Arrival (AoA) were proposed and investigated. In the ToA based localization systems, the detection of shortest signal propagation time plays a critical role. In the case of multi-path propagation, the Direct Path (DP) needs to be resolved because the DP may be weaker than Multi Path Components (MPC). Thus the novel algorithms for leading edge detection were developed in this work in order to improve the accuracy of localization, namely Joint Leading Edge Detection (JLED), Improved Maximum Likelihood Channel Estimation (IMLCE) and the leading edge detection with Subspace based Approaches (SbA). Two criteria were proposed and referenced for the JLED, namely Minimum Area (MA) and Minimum Mean Squared Error (MMSE). Furthermore, a monocycle-based channel estimator was developed to mitigate the fake LECs (Leading Edge Combination). The estimation error of JLED was theoretically analyzed and simulated for evaluation of the estimator. IMLCE consists of a coarse and a fine estimation step. The coarse position of the first correlation peak shall be found with the Search Back Algorithms (SBA), which is followed by MLCE-algorithms. The novel SbA was investigated in a static and a fading channel. In the former case, the iterative algorithm, which combines SbA with SBA, was investigated. In the latter case, the FD-SbA (Frequency Domain - SbA) was proposed, which requires to calculate the covariance matrix in the FD. For the RSS based localization, fingerprint approach and the novel channel energy based distance estimator were investigated and developed in this dissertation. Finally, a localization system using AoA estimation and the initial calibration was presented on an 802.11a/g hardware platform. A novel Carrier Frequency Offset (CFO) estimator and channel estimator were investigated and developed. The measurement campaigns were made for one, two and four fixed stations, respectivel

    Abstracts on Radio Direction Finding (1899 - 1995)

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    The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

    Optimisation of wireless communication system by exploitation of channel diversity

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    Communication systems are susceptible to degradation in performance because of interference received through their side lobes. The interference may be deliberate electronic counter measure (ECM), Accidental RF Interference (RFI) or natural noise. The growth of interference communication systems have given rise to different algorithms, Adaptive array techniques offer a possible solution to this problem of interference received through side lobes because of their automatic null steering in both spatial and frequency domains. Key requirement for space-time architecture is to use robust adaptive algorithms to ensure reliable operation of the smart antenna. Space division multiple access (SDMA) involves the use of adaptive nulling to allow two or more users (mobiles) in the same cell to share same frequency and time slot. One beam is formed for each user with nulls in the direction of other users. Different approaches have been used to identify the interferer from desired user. Thus a basic model for determining the angle of arrival of incoming signals, an appropriate antenna beam forming and adaptive algorithms are used for array processing. There is an insatiable demand for capacity in wireless data networks and cellular radio communication systems. However the RF environment that these systems operate in is harsh and severely limits the capacity of traditional digital wireless networks. With normal wireless systems this limits the data rate in cellular radio environments to approximately 200 kbps whereas much higher data rates in excess of 25Mbps are required. A common wireless channel problem is that of frequency selective multi-path fading. To combat this problem, new types of wireless interface are being developed which utilise space, time and frequency diversity to provide increasing resilience to the channel imperfections. At any instant in time, the channel conditions may be such that one or more of these diversity methods may offer a superior performance to the other diversity methods. The overall aim of the research is to develop new systems that use a novel combination of smart antenna MIMO techniques and an advanced communication system based on advanced system configuration that could be exploited by IEEE 802.20 user specification approach for broadband wireless networking. The new system combines the Multi-input Multi-output communication system with frequency diversity in the form of an OFDM modulator. The benefits of each approach are examined under similar channel conditions and results presented.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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