Title page for ETD etd-01242007-111109

Type of Document Master's Thesis
Author Chitnis, Chetan Neginhal
Author's Email Address cchitn1@lsu.edu
URN etd-01242007-111109
Title Differential Space Time Modulation and Demodulation for Time Varying Multiple Input Multiple Output Channels
Degree Master of Science in Electrical Engineering (M.S.E.E.)
Department Electrical & Computer Engineering
Advisory Committee
Advisor Name Title
Xue-Bin Liang Committee Chair
Hsiao-Chun Wu Committee Member
Subhash C Kak Committee Member
  • transmitter diversity
  • unitary scheme
  • alamouti scheme
  • differential modulation
  • wireless communication
  • mimo
  • jake's model
  • parametric codes
  • space time block codes
  • orthogonal space time block codes
  • non-coherent modulation
  • time varying channels
Date of Defense 2006-11-14
Availability unrestricted
Over the last decade there has been considerable interest in wireless communication using multiple transmit and receive antennas. Several literatures exists that show that these multiple link support very high data rates with low error probabilities when the channel state information is available at the receiver. However when multiple antennas are employed or when the mobile environments change rapidly, it is not always possible to have apriori knowledge of the channel state matrices which calls for Differential Space-Time modulation techniques.

Differential modulation is used in conjunction with Unitary Space-Time codes to evaluate their performance over time varying channels. Jakes model for frequency flat fading processes in mobile radio systems is incorporated with the differential modulation scheme to model a time-varying space-time Rayleigh fading multiple input multiple output (MIMO) radio channel. Parametric unitary codes that are known to have the largest possible diversity product for a 16-signal constellation and a 4-signal constellation with both optimal diversity sum and diversity product is used to evaluate the Block Error Rates for 2 and 5 receiver antennas that are moving at different velocities.

A fast differential demodulation for Alamouti codes is derived based on prior work by Liang and Xia and is tested using our simulations.

MATLAB R2006b V 7.1 is used to simulate the performance of M=2, N=2 and M=2 N=5 antennas over a time varying channel for velocities of 0, 50, 75, 100 and 125 kmph. We also show that the fast demodulation algorithm is almost twice as fast and also perform within 1dB of existing differential demodulation schemes.

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