Frame/slot synchronization for U.S. digital cellular TDMA radio telephone system

Apparatus for applying frame/slot synchronization to a Time Division Multiple Access (TDMA) signal, comprising:

• a) means for receiving the TDMA signal;
• b) means for acquiring a temporal position of a reference feature associated with a desired time slot, the desired time slot being one time slot of a plurality of time slots that comprise a frame, the acquiring means also verifying that the acquired temporal position corresponds to the desired time slot, the acquiring means including means for estimating a temporal position of the reference feature in a subsequent frame and means for sampling the subsequent frame at the estimated temporal position to determine if the reference feature is present;
• and
• c) means for estimating, over a plurality of received frames, synchronization to the temporal position of the reference feature of the desired time slot, the estimating means including a means for locating N.sub.1 correlation peaks in succession at predetermined correlation peak locations, N.sub.1 being a desired number of found peaks;
• and
• d) means for adjusting the estimated temporal slot position for each frame.

A method for applying frame/slot synchronization to a Time Division Multiple Access (TDMA) RF signal for a digital cellular radio telephone system, comprising the steps of:

• a) receiving the TDMA RF signal;
• and
• b) demodulating the TDMA RF signal by the steps of
• 1. acquiring a temporal position of a predetermined synchronizing bit sequence associated with a desired time slot by determining a normalized cross-correlation T(n) between the predetermined bit sequence and a received bit sequence by comparing a value of the normalized cross-correlation T(n) to a threshold value, being in the range of 0.4 to 0.8, to ascertain that the predetermined bit sequence of the desired time slot has been located if the value of the determined normalized cross-correlation T(n) exceeds the threshold value, the desired time slot being one of a plurality of time slots that comprise a frame;
• 2. verifying that the acquired temporal position corresponds to the desired time slot by repetitively estimating a temporal position of the bit sequence in a subsequently received frame;
• and
• 3. sampling the subsequently received frame at the estimated temporal position to obtain the normalized cross-correlation T(n) between the predetermined bit sequence and the received bit sequence to determine if the predetermined synchronizing bit sequence is present.