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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A MAC Protocol for Multihop RP-CDMA Ad Hoc Wireless Networks

Mortimer, Richard T Unknown Date
No description available.
32

Indoor infrared wireless PPM systems

Chan, Hsun-Hung January 1998 (has links)
No description available.
33

Signalverarbeitungskonzepte für Mobilfunksysteme der dritten Generation gezeigt am Beispiel eines JD-CDMA-Mobilfunksystems /

Weber, Tobias. Unknown Date (has links)
Universiẗat, Diss., 1999--Kaiserslautern.
34

Adaptive antennas for mobile radio systems using time division CDMA and joint detection

Papathanassiou, Apostolos. Unknown Date (has links)
University, Diss., 2000--Kaiserslautern.
35

Contributions to the application of adaptive antennas and CDMA code pooling in the TD-CDMA downlink

Lu, Yang. Unknown Date (has links) (PDF)
University, Diss., 2002--Kaiserslautern.
36

Gemeinsame Empfangssignalverarbeitung in CDMA-Mobilfunksystemen mit infiniter oder quasi-infiniter Datenübertragung

Meurer, Michael. January 2003 (has links) (PDF)
Universiẗat, Diss., 2003--Kaiserslautern.
37

Utilization of correlation matrices in adaptive array processors for time slotted CDMA uplinks

Weckerle, Martin. January 2002 (has links) (PDF)
University, Diss., 2002--Kaiserslautern.
38

Multiuser detection and channel estimation for DS-CDMA systems

Lampe, Alexander. Unknown Date (has links) (PDF)
Nürnberg, University, Diss., 2003--Erlangen. / Erscheinungsjahr an der Haupttitelstelle: 2002.
39

Hybrid overlay/underlay cognitive radio networks with MC-CDMA

Jasbi, Fahimeh Jafarali January 2014 (has links)
There has been a growing demand for wireless communication services in the past few years. Recent reports reveal that the demand will not only increase in the number of subscribers but also in more diverse applications such as Machine-to-Machine (M2M) communications and the Internet of Things. With such demand for capacity increase, there is a necessity to shift from today’s Static Frequency Allocation (SFA) to Dynamic Spectrum Access (DSA). The change will make efficient use of spectrum by utilizing the unused parts in different times, frequencies and spaces. With this regard, cognitive radio (CR) is a powerful potential candidate for the spectrum scarcity problem. This work addresses the two main current discussions in Cognitive Radio Networks (CRN), spectral efficiency and interference mitigation problem. There are two main spectrum sharing techniques in CRN, overlay and underlay, which have been thoroughly investigated in the literature. Unlike the relative works which separate the use of overlay and underlay, this works considers the joint overlay and underlay as a hybrid system to enhance the spectral efficiency and Bit Error Rate (BER) performance in CRNs. MC-CDMA is proposed for underlay transmission for two main advantages. Firstly, for low power spectral density due to spreading. Secondly, for its capability to mitigate high interference. Two hybrid MC-CDMA schemes are proposed in this work. The first scheme spreads the underlay signal through the whole bandwidth to mitigate PU interference and benefit from the frequency diversity. To maximize data rate, overlay utilizes the available bands while keeping orthogonality with underlay using Orthogonal Variable Spreading Factor (OVSF) codes. To further increase capacity, an overload MC-CDMA system is proposed. In this scheme, overlay utilizes the full signal dimension, while underlay overloads the system. Two layered spreading is applied to differentiate overlay and underlay users. In order to detect the underlay signal, the overlay signal is detected first and is cancelled from the received signal. The underlay data is then detected from this modified signal. The framework is then extended to a multi-user underlay scenario. A code allocation algorithm is proposed in order to achieve low cross-correlation between the overlay and underlay users. The results show that the proposed overload system maintains good performance even in high PU interference level. Furthermore, the proposed hybrid capacities are optimized and compared with the two available hybrid systems in the literature. The proposed overload system showed to increase capacity significantly, both in AWGN and fading environment, in compared with the existing methods.
40

Fixed-Point Implementation of a Multistage Receiver

Cameron, Rick A. 13 January 1997 (has links)
This dissertation provides a study of synchronization and quantization issues in implementing a multistage receiver in fixed-point Digital Signal Processing (DSP) hardware. Current multistage receiver analysis has neglected the effects of synchronization and quantization; however, these effects can degrade system performance and therefore decrease overall system capacity. The first objective is to analyze and simulate various effects of synchronization in a multistage system. These effects include the effect of unsynchronized users on the bit error rate (BER) of synchronized users, and determining whether interference cancellation can be used to improve the synchronization time. This information is used to determine whether synchronization will limit overall system capacity. Both analytical and simulation techniques are presented. The second objective is to study the effects of quantization on the performance of the multistage receiver. A DSP implementation of a practical receiver will require a DSP chip with a fewer number of bits than the computer chips typically used in simulation of receiver performance. Therefore, the DSP implementation performs poorer than the simulation results predict. In addition, a fixed-point implementation is often favored over a floating-point implementation, due to the high processing requirements necessitated by the high chip rate. This further degrades performance because of the limited dynamic range available with fixed-point arithmetic. The performance of the receiver using a fixed-point implementation is analyzed and simulated. We also relate these topics to other important issues in the hardware implementation of multistage receivers, including the effects of frequency offsets at the receiver and developing a multiuser air protocol interface (API). This dissertation represents a contribution to the ongoing hardware development effort in multistage receivers at Virginia Tech. / Ph. D.

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