Joint optimal pilot placement and power allocation with space frequency code design and adaptive modulation for video transmission over MIMO-OFDM systems
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Over the past decade, MIMO-OFDM systems have been at the fore front of wireless communication and 4G standards, particularly for high data rate transmission in wireless LANs with frequency selective fading channels. This has caused considerable interest in the development of such systems with improved Bit Error Rate (BER) performances and data rates. Smarter channel estimation techniques at the receiver, which are the basis for the above desired performance metrics have been investigated using optimal pilot symbol placements which result in minimum Mean squared Error (MSE) of channel estimation and improved BER performances. In this thesis, we develop a new pilot-tone placement algorithm for MIMO-OFDM systems which has its roots from a previous pilot-tone placement study. The two pilot placement schemes are optimal in the sense that they result in minimum MSE of the estimated channel data along with superior BER values. Using this newly proposed algorithm, we propose an adaptive pilot placement scheme which facilitates for increased data rates at high SNR values at the cost of negligible degradation in BER performance and superior BER performances at low SNR conditions. Using a heuristic algorithm, an optimal power allocation scheme is developed for the above system which maximizes the system performance by optimally distributing available power between data and pilot symbols. Also, we show in our system the use of an adaptive modulation scheme with a target BER constraint. We show, through the experimental results the effectiveness of such a system in that various optimization parameters can be tuned in order to achieve better data rates or BER performance as the need be. We have developed the results for a 2 × 2 MIMO-OFDM system with arbitrary bit stream as input data but they can be extended to MIMO systems with any number of transmit and receive antennas. Results are also shown for multimedia data (H.264/AVC) by deriving the Packet Loss rate (PLR) from the BER values gathered from the above system setup.