Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 63 for “"Spatial diversity"”.
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Spatial diversity in cellular networks
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.
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Iterative detection for overloaded OFDMA with spatial diversity
… where users are additionally multiplexed in the spatial domain to each frequency resource. To efficiently resolve non-orthogonally multiplexed users within the system, sophisticated multiple antenna receivers with multiuser detection methods are necessary. The focus of this thesis will be the …
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Effects of user and spatial diversity on high data rate wireless systems
… can support the best rate. In contrast, antenna diversity, where multiple antennas are deployed at the receiver or transmitter; has the effect of improving received signal fidelity by averaging the channel variation. In this thesis, we evaluate the joint effect of user diversity and antenna …
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Reciprocity-enhanced time-division multiplexed optical switching with spatial diversity for free-space optical communication links
… reciprocity to switch between multiple (N) spatially-diverse apertures to increase data transmission through a scintillating channel. Electromagnetic signals, specifically optical, propagating along either direction of the same path experience the same changes in signal strength …
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Performance analysis of collaborative hybrid-arq protocols over fading channels
… be efficiently mitigated with time, frequency or spatial diversity. To exploit spatial diversity, multiple-antenna technology has been thoroughly investigated and emerged as one of the most mature communications areas. However, the need for smaller user terminals, which results in insufficient …
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Channel Probing for an Indoor Wireless Communications Channel
… models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath …
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Transmit Diversity and its Application to Cooperative Networking
… antenna space-time coding techniques to achieve spatial diversity. We observe that when correlation between the antennas in a local antenna array becomes high due to space constraints in a terminal, current performance achieving strategies do not actually deliver good results. Moreover, most …
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Cooperative diversity in wireless networks : algorithms and architectures
… the greater benefits gained by exploiting spatial diversity in the channel. By contrast, classical network architectures only employ point-to-point transmission and thus forego these benefits. After summarizing a model for the wireless channel, we present various practical cooperative …
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Characterization of tropospheric scintillations on Earth-space paths in the Ku and Ka frequency bands using the results from the Virginia Tech OLYMPUS experiment
… the current CCIR predictive model. Sma11 scale spatial diversity is a potential means to counteract tropospheric scintillation fading; it can be cost effective because of the low cost of VSATs. The VA Tech experiment includes 12, 20, 30 GHz beacon receivers and colocated 20 and 30 GHz diversity …
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Communication Strategies for Single-User and Multiuser Slow Fading Channels
… communication systems with the advent of the diversity concept. Spatial diversity exploits the availability of multiple spatial paths between the transmitter and receiver by placing antenna arrays at either end. In addition to improving the reliability of communication by creating redundant …
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Development and performance evaluation of a multistatic radar system
… are of emerging interest as they can exploit spatial diversity, enabling improved performance and new applications. Their development is being fuelled by advances in enabling technologies in such fields as communications and Digital Signal Processing (DSP). Such systems differ from typical …
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Measurement System and Campaign for Characterizing the Theoretical Capacity and Cross-Correlation of Multiple-Input Multiple Output Indoor Wireless Channels
… power have historically motivated research in spatial diversity systems. Diversity techniques have been implemented in many current systems and have been shown to reduce the transmit power required to maintain acceptable system performance. Traditionally spatial diversity is based on the …
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Adaptive sampling of transient environmental phenomena with autonomous mobile platforms
… expense. As a result, the temporal detail and spatial diversity in the samples may fail to capture insightful structure of the phenomenon of interest. The development of in situ instrumentation allows for near real-time analysis of physical phenomenon through observational strategies (e.g., …
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Statistical modeling and simulation of mobile satellite propagation
… using the propagation simulator to simulate spatial diversity to combat vegetative fading are given.
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Incremental housing at the receding suburban fringe
… efficient housing while encouraging formal and spatial diversity in the urban experience.
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New hybrid automatic repeat request (HARQ) scheme for 4x4 MIMO system, based on the extended alamouti quasi-orthogonal space-time bloc coding (Q-STBC), in invariant and variant fading channel
… reducing the interference while exploiting the spatial diversity to introduce some gain in the signal power. The best transmission order is selected by the Determinant Criterion, which optimizes the SNR in each receiver antenna to minimize the Bit Error Rate (BER) and maximize the throughput. …
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The ecological and evolutionary drivers of spatial biodiversity patterns
… vary dramatically from place to place. These spatial patterns of biodiversity are the focus of biogeographical and macroecological research and offer us clues into the evolutionary processes shaping nature's variety. Finding general patterns and their underlying drivers, however, is not a …
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The ecological and evolutionary drivers of spatial biodiversity patterns
… vary dramatically from place to place. These spatial patterns of biodiversity are the focus of biogeographical and macroecological research and offer us clues into the evolutionary processes shaping nature's variety. Finding general patterns and their underlying drivers, however, is not a …
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ΠΡΟΔΕΛΤΑΙΚΕΣ ΑΠΟΘΕΣΕΙΣ. ΣΕΙΣΜΙΚΗ ΣΤΡΩΜΑΤΟΓΡΑΦΙΑ-ΙΖΗΜΑΤΟΛΟΓΙΑ-ΕΥΣΤΑΘΕΙΑ ΠΡΑΝΩΝ
… PROPERTIES DISPLAYED HIGH VERTICAL AND SPATIAL DIVERSITY WITHIN THE PRODELTA SEQUENCES. THIS IS DUE TO FLUCTUATIONS OF NEAR BOTTOM HYDRODYNAMIC CONDITIONS, VARIATION OF DEPOSITIONAL MECHANISMS (ESPECIALLY THE SEDIMENTATION RATES), TO VARIOUS MASS MOVEMENTS AND FINALLY TO POSSIBLE …
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Sistemas integrados de la navegación mediante redes locales inalámbricas
… angles, respectively.Both special modulation and spatial diversity techniques are needed to cancel the multipath effects mainly due to wave reflections as the wave is propagating through the indoor channel.A typical configuration for this kind of systems consists of a set of base stations, …
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