Patent ID: 6084886
Filing Date: 2000-07-04
Classification: H04H,H04L,H04W

Abstract:
A method for facilitating an establishment of communications in a messaging system, the method comprising in K transmitters of each of M clusters including a first cluster and M-1 adjacent clusters, K and M being predetermined positive integers, the steps of:simulcasting a digital sync signal; andthereafter transmitting, in each of the M clusters, K fine tuning signals during K time slots, each time slot assigned to one of the transmitters, wherein each fine tuning signal comprises a pair of tones separated in frequency by a predetermined amount and having a beginning characterized by a relative phase of a predetermined value,the method further comprising in a portable subscriber unit the steps of:receiving the digital sync signal and the fine tuning signals;making a rough estimate of the beginning of the fine tuning signals from the digital sync signal and from knowledge of a predetermined arrangement of the time slots;computing for each of the time slots a 2M-point Fourier transform (FT), at frequencies corresponding to the pair of tones of each fine tuning signal, on a received signal comprising M fine tuning signals received during the time slot from a transmitter of the first cluster and from M-1 corresponding transmitters of adjacent clusters; andfine tuning the rough estimate through FT calculations corresponding to at least one of the fine tuning signals, thereby generating a fine estimate of the beginning of the at least one of the fine tuning signals.