On the use of TCH sequences for synchronization, channel and noise estimation

TCH sequences have been studied for code-spreading and channel coding, but its true essence if that of synchronization and channel estimation. This is due to their property of being (almost) orthogonal to all sequences obtained via circular shifts. This property is extremely useful for time-offset synchronization (there is a distinct ldquopeakrdquo only when both sequences are aligned), and for dispersive channel-estimation (since the multipath-taps are now orthogonal to each other). Alongside the use of the TCH sequences, a sequence of equal symbols is also employed for frequency-synchronization-essential for correcting the phase offset between estimates (especially for high offset values), and thus allowing for the posterior signal-processing.