| The recent developments in satellite communications have opened the door to provide high speed B-ISDN to millions of home and small business users. With ATM becoming the standard for future multimedia transmissions, many new satellite networks have been proposed or built to carry ATM transmission. This thesis concentrates on the studies of synchronization techniques suitable for use in home-based satellite modems for transmission on the return link from a terminal to a hub through a satellite repeater. Two new burst timing algorithms based on Gardner's zero-crossing tracker are developed for a Nyquist sampling, 40% roll-off coherent QPSK burst modem. Using a bank of interpolation filters, these algorithms can acquire a timing offset in just 8 preamble symbols. By computer simulations, their BER performance is shown to be very close to the theoretical limit on an AWGN channel for Eb/ No, as low as --3 dB. Two new phase acquisition algorithms are also discussed in this thesis that are suitable for burst transmission and capable of tracking a normalized frequency offset of foT s = 0.001 at Eb/N o as low as 0 dB for uncoded burst transmission. Both phase acquisition schemes work entirely on phasors and are very efficient for DSP implementation. Rate-1/2 convolutional codes are used to improve decoding performance. In this case, synchronization is possible for E b/No as low as 1.5 dB. Techniques of using the convolutional decoder to assist phase acquisition are investigated as well. |
