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1	Novel algorithms in wireless CDMA systems for estimation and kernel based equalization Vlachos, Dimitrios January 2012 (has links) A powerful technique is presented for joint blind channel estimation and carrier offset method for code- division multiple access (CDMA) communication systems. The new technique combines singular value decomposition (SVD) analysis with carrier offset parameter. Current blind methods sustain a high computational complexity as they require the computation of a large SVD twice, and they are sensitive to accurate knowledge of the noise subspace rank. The proposed method overcomes both problems by computing the SVD only once. Extensive simulations using MatLab demonstrate the robustness of the proposed scheme and its performance is comparable to other existing SVD techniques with significant lower computational as much as 70% cost because it does not require knowledge of the rank of the noise sub-space. Also a kernel based equalization for CDMA communication systems is proposed, designed and simulated using MatLab. The proposed method in CDMA systems overcomes all other methods. 621.3845
2	Advanced techniques to improve the performance of OFDM Wireless LAN Segkos, Michail 06 1900 (has links) Approved for public release; distribution is unlimited / OFDM systems have experienced increased attention in recent years and have found applications in a number of diverse areas including telephone-line based ADSL links, digital audio and video broadcasting systems, and wireless local area networks (WLAN). Orthogonal frequency-division multiplexing (OFDM) is a powerful technique for high data-rate transmission over fading channels. However, to deploy OFDM in a WLAN environment, precise frequency synchronization must be maintained and tricky frequency offsets must be handled. In this thesis, various techniques to improve the data throughput of OFDM WLAN are investigated. A simulation tool was developed in Matlab to evaluate the performance of the IEEE 802.11a physical layer. We proposed a rapid time and frequency synchronization algorithm using only the short training sequence of the IEEE 802.11a standard, thus reducing the training overhead to 50%. Particular attention was paid to channel coding, block interleaving and antenna diversity. Computer simulation showed that drastic improvement in error rate performance is achievable when these techniques are deployed. / Lieutenant, Hellenic Navy Wireless LANs Multiplexing OFDM WLAN IEEE 802.11a Exponential channel model Packet detection Frame synchronization Frequency synchronization Carrier offset Phase noise Pilot phase tracking Channel estimation Equalization Scrambling Convolutional coding Interleaving Maximal ratio combining Selection diversity Viterbi algorithm Soft decision decoding Puncturing

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Novel algorithms in wireless CDMA systems for estimation and kernel based equalization

Advanced techniques to improve the performance of OFDM Wireless LAN