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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.
1

Linear Prediction Approach for Blind Multiuser Detection in Multicarrier CDMA Systems

Qin, Qin 15 October 2002 (has links)
No description available.
2

SPECTRALLY SHAPED GENERALIZED MULTITONE DIRECT SEQUENCE SPREAD SPECTRUM

Xiong, Wenhui 10 August 2007 (has links)
No description available.
3

Multicarrier Diversity in Random Access Networks

Ganesan, Ghurumuruhan 12 1900 (has links)
Random access schemes are primarily used for data transmission in the uplink of cellular networks. Every user in a random access network is programmed to follow a predetermined transmit control policy that is designed to achieve optimal network performance. This approach, however, is not very efficient in cellular networks where channel conditions vary from time to time. Employing a fixed transmission policy may not guarantee optimal performance. To alleviate this problem, recently, channel aware random access schemes have been proposed wherein information available at the physical (PHY) layer is utilized at the higher layers to maximize network throughput. Such a cross-layer approach naturally has its share of challenges and problems. The objective of the proposed research is to study the effect of multicarrier diversity on channel aware random access schemes. First, we describe two generic random access schemes - channel aware multicarrier random access (CAMCRA) and no selection random access (NS-RA) for multicarrier networks. The former is based on judicious carrier selection and exploits multicarrier diversity while the latter does not perform carrier selection. For illustration purposes, we consider the well-known Aloha protocol and study the effect of channel state imperfection on the overall network throughput. We show that networks employing the NS-RA scheme are extremely sensitive to channel measurement errors. More precisely, the asymptotic average throughput of the NS-RA scheme under uncertain channel conditions is zero. The CAMCRA scheme, however, is very robust to channel estimation errors and maintains the same order of throughput.
4

Multi-user detection for multi-carrier communication systems

Hijazi, Samer L. January 1900 (has links)
Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / Wireless broadband communications is a rapidly growing industry. New enabling technologies such as multi-carrier code division multiple access (MC-CDMA) are shaping the future of wireless systems. However, research efforts in improving MC-CDMA receiver performance have received limited attention and there is a need for innovative receiver designs for next generation MC-CDMA. In this thesis, we propose novel multi-user detection (MUD) schemes to enhance the performance of both synchronous and asynchronous MC-CDMA. First, we adapt the ant colony optimization (ACO) approach to solve the optimal MUD problem in MC-CDMA systems. Our simulations indicate that the ACO based MUD converges to the optimal BER performance in relatively few iterations providing more that 95% savings in computational complexity. Second, we propose a new MUD structure specifically for asynchronous MC-CDMA. Previously proposed MUDs for asynchronous MC-CDMA perform the detection for one user (desired user) at a time, mandating multiple runs of the algorithm to detect all users' symbols. In this thesis, for the first time we present a MUD structure that detects all users' symbols simultaneously in one run by extending the receiver's integration window to capture the energy scattered in two consecutive symbol durations. We derive the optimal, decorrelator and minimum mean square error (MMSE) MUD for the extended window case. Our simulations demonstrate that the proposed MUD structures not only perform similar to a MUD that detects one user at a time, but its computational complexity is significantly lower. Finally, we extend the MUD ideas to multicarrier implementation of single carrier systems. Specifically, we employ the novel MUD structure as a multi-symbol detection scheme in CI-CDMA and illustrate the resulting performance gain via simulations.
5

Wavelet Packet Based Multicarrier CDMA Wireless Communication Systems

Zhang, Hongbing 02 July 2004 (has links)
No description available.
6

Wavelet based MIMO-multicarrier system using forward error correction and beam forming

Asif, Rameez, Ali, N.T., Migdadi, Hassan S.O., Abd-Alhameed, Raed, Hussaini, Abubakar S., Ghazaany, Tahereh S., Naveed, S., Noras, James M., Excell, Peter S., Rodriguez, Jonathan January 2013 (has links)
No / Wavelet based multicarrier systems have attracted the attention of the researchers over the past few years to replace the conventional OFDM systems in the next generation communication systems. In this paper we have investigated the performance of such wavelet based systems using forward error correction with covolutional coding and interleaving in a Wavelet-SISO system and then in a Wavelet multicarrier modulation (WMCM) multiple input multiple output (MIMO) system using Convolutional coding and beamforming to reduce the source bit rate and overall system error and increase the data rate. Results show outstanding Bit Error Rate vs. Signal to Noise Ratio Performance. Other than better performance the proposed systems keep the computational burden off the receiver that has more cost and power constraints.
7

Performance Analysis of Complementary Code Based MIMO-CDMA Systems in Correlated Multi-Carrier Channels

Tsai, Tsung-chi 30 August 2005 (has links)
This thesis mainly focuses on the integration of Space-Time Block Coding (STBC) and Complementary Code based CDMA system. Our proposed integration systems have not only the merit of complementary code but also the extra advantage of diversity gain from STBC. Especially, when the different frequency channel gain has strong correlation, the complementary code will cancel most of interference.
8

A Filtered Multitone (FMT) Implementation with Custom Instructions on an Altera FPGA

Xin, Xin 10 June 2013 (has links)
There is a belief that radio frequencies  are running out. However, according to a report from the Federal Communications Commission (FCC) in 2002, a different story was told : At any given time and location, much of the prized spectrum lies idle. At the same time, FCC revealed the fact that, in many bands, spectrum access is a more significant problem than physical scarcity of spectrum, in large part due to legacy command-and-control regulation that limits the ability of potential spectrum users to obtain such access. Hence, as opposed to static spectrum access, dynamic spectrum access (DSA) was proposed to solve the predicament. One such DSA model propose the existence of Primary users (licensed users and Secondary users (unlicensed users). Multicarrier communication technology is adopted to enable the coexistence of PU and SU. Orthogonal Frequency Division Multiplexing (OFDM) technology has been popular for multicarrier communications. A disadvantage for OFDM in the Cognitive Radio environment is its large side lobes in the frequency domain, which is a result of single-symbol pulse duration. Filter Bank Multicarrier (FBMC) uses filters that have small side lobes to synthesize/analyze the sub-carriers so as to greatly alleviate the previous mentioned disadvantage. FMT is one FBMC technique.  Although many hardware implementations have been explored during last few decades on OFDM, few FMT hardware implementation results, especially Hardware/Software Co-design, have been presented. This paper presents a HW/SW Co-design implementation result of FMT transceiver on the Altera DE4 board. / Master of Science
9

Beamforming for MC-CDMA

Venkatasubramanian, Ramasamy 10 March 2003 (has links)
Orthogonal Frequency Division Multiplexing (OFDM) has recently gained a lot of attention and is a potential candidate for Fourth Generation (4G) wireless systems because it promises data rates up to 10Mbps. A variation of OFDM is Multi-Carrier CDMA (MC-CDMA) which is an OFDM technique where the individual data symbols are spread using a spreading code in the frequency domain. The spreading code associated with MC-CDMA provides multiple access technique as well as interference suppression. Often times in cellular and military environments the desired signal can be buried below interference. In such conditions, the processing gain associated with the spreading cannot provide the needed interference suppression. This research work investigates multi-antenna receivers for OFDM and MC-CDMA systems; specifically this works investigates adaptive antenna algorithms for MC-CDMA for very different channel conditions. Frequency domain beamforming is studied in this research predominantly through simulation. As an alternative a time domain beamforming is also studied. Time variations in the channel can disrupt the orthogonality between subcarriers. Minimum Mean Square Error (MMSE) detection coupled with MMSE beamforming is proposed for time varying channels. Semi-analytic results are derived to study the Bit Error Rate (BER) performance. These results show significant performance improvement in the presence of interference. Joint MMSE weights in space and frequency is also investigated and semi-analytic results are derived to study their BER performance. / Master of Science
10

Design and Analysis of Multicarrier Multicode Wavelet Packets Based CDMA Communication Systems with Multiuser Detection

Akho-Zahieh, Maryam Mahmoud 05 October 2006 (has links)
No description available.

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