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 43 for “"DS-CDMA"”.
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Data Chunking in Quasi-synchronous DS-CDMA
<p>DS-CDMA is a popular multiple access technique used in many mobile networks to efficiently share channel resources between users in a cell. Synchronization between users maximizes the user capacity of these systems. However, it is difficult to perfectly synchronize users in the reverse link due …
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Partial DS-CDMA for mobile satellite data networks.
… direct sequence code division multiple access (DS-CDMA) is used, this need not to be the case, because the DS-CDMA system allows many packets to coexist in a given slot. Thus packets are correctly received with certain probability which depends on the simultaneous number of packets in the slot. …
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Optimization of Soft Interference Cancellation in DS-CDMA Receivers
Parallel interference cancellation for DS-CDMA has been shown to suffer from biased amplitude estimates if a matched-filter estimator is used. The bias magnitude is proportional to the number of interfering users. For heavy system loads, the bias has been shown to adversely effect the accuracy of …
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Multi-user detection for multi-rate DS/CDMA systems
… and range of services. Current and future demands for wireless communication services motivate the need for handling multi-media traffic types. In a multimedia communication system, users with different and even time-varying rates and quality of services (QoS) requirements, such as voice, image …
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Channel estimation and signal enhancement for DS-CDMA systems
… direct-sequence code-division multiple-access (DS-CDMA) systems. Using the Bayesian framework, various linear and simplified nonlinear multiuser detectors are proposed, and their performances are analyzed. The simplified non-linear Bayesian solutions can bridge the performance gap between …
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A channel-shortening multiuser detector for DS-CDMA systems
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.
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Efficient Interference Cancellation Techniques for Advanced DS-CDMA Receivers
… derived. Based on this approach, two real-time DSP implementations are devised, one fully coherent and one non-coherent. Multi-symbol differential detection is then explored as an alternative for improving the performance of the non-coherent approach. Additionally, dual-antenna diversity …
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Uplink Power Control and Soft Handoff Prioritization in Multimedia DS-CDMA
In the CDMA cellular networking system, power control is a very important issue because it is an interference limited system. In order to reduce the near-far problem and improve the battery life of mobile station, the transmit power of mobile stations must be controlled to limit interference. In …
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Optimum spreading bandwidth for DS-CDMA on time and frequency fading channels
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
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Hybrid Channel Coding for Error-Sensitive Class on DS-CDMA Air Interface
A DS-CDMA system with QPSK modulation and a RAKE receiver is modeled and simulated. A mathematical description of the DS-CDMA system is provided on uplink and downlink. For a multipath channel environment, modeling techniques for AWGN and Rayleigh fading are illustrated. Comparisons are made …
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Adaptive DS-CDMA multiuser detection for time variant frequency selective Rayleigh fading channel
… direct sequence Code Division Multiple Access (DS-CDMA) technology, will not be able to meet the growing demands for multimedia service due to low information exchanging rate. Its capacity is also limited by multiple accessed interference (MAI) signals. This work focuses on the development of …
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Performance of turbo multi-user detectors in space-time coded DS-CDMA systems
… the uplink capacity and the performance of a DS-CDMA system by combining MUD and turbo decoding. These two are combined following the turbo principle. Depending on the concatenation scheme used, we divide these receivers into the Partitioned Approach (PA) and the Iterative Approach (IA) …
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Performance of turbo coded DS-CDMA systems in correlated and uncorrelated satellite communication channels
This thesis aims at presenting the perfonnance of turbo codes in the correlated and uncorrelated satellite fading channel. Turbo codes are known to give very good perfonnance results in A WGN channels, especially for very large input message length codes or interleaver sizes. It can be shown that …
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High performance multi-carrier technologies with expanded applicability to CDMA systems (DS-CDMA and MC-CDMA)
Code division multiple access (CDMA) has been an important component in wireless communication systems since the early 1980’s. Now the frontrunner in the 3G cellular standard, CDMA techniques have come a long way since their inception. However, these systems are not without their limitations -- …
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Phase-locked loop, delay-locked loop, and linear decorrelating detector for asynchronous multirate DS-CDMA system
… investigated in wideband asynchronous multirate DS-CDMA system. Dynamic Partial Correlation (DPC) method is proposed to evaluate the autocorrelation and its power spectrum density (PSD) of the cross-correlated terms in the presence of multirate multiple access interference (MMAI) under additive …
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Reduced-complexity near-optimal Ant-Colony-aided multi-user detection for CDMA systems
… (ACO) assisted Multi-User Detectors (MUDs) are proposed and investigated. The exhaustive search complexity of the optimal detection algorithm may be deemed excessive for practical applications. For example, a Space-Time Block Coded (STBC) two transmit assisted K = 32-user system has to …
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Wireless ATM Networks Medium Access Control with Adaptive Parallel Multiple Substream CDMA Air-inteface
… direct-sequence code-division-multiple-access (DS-CDMA) air-interface method has, such as inherent robustness against multipath fading, better resilience against security infringement attempts, and greater overall capacity compared to the TDMA method as proven in the cellular telephone industry. …
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Blind Channel Estimation and Multiuser Detection for Multi-Rate CDMA Communications
… links to the individual users. Multi-rate DS/CDMA is a promising basis on which to support the variable bit rates on the individual wireless links. Currently, the study on channel estimation and multiuser detection for multi-rate DS/CDMA, which makes full use of the nature of multi-rate …
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Performance analysis of VSAT networks
… Direct sequence code division multiple access (DS-CDMA) is the simplest spread spectrum technique to use in a VSAT network, since a frequency synthesizer is not required for each terminal. This thesis examines DS-CDMA and SCPC Ku-band VSAT satellite systems for low-density (64 kbps or less) …
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