Frame synchronization using soft decisions in a universal mobile telephone system receiver

A method for use in a universal mobile telephone system (UMTS) receiver, comprising:

• receiving a signal representing a secondary synchronization channel (SSCH) transmitted from a UMTS transmitter, the SSCH conveying a sequence of S SSCH symbols over S time slots, the sequence associated with a scrambling code group associated with the UMTS transmitter, wherein the scrambling code group is taken from a set of 64 scrambling code groups;
• storing data representative of probabilities that each one of K SSCH symbols were received in each one of the S thie slots, where K>I;
• determining metric values from the stored data, each metric value representing a probability that a particular cyclic shift of a particular one of the 64 scrambling code groups was received;
• identifying the highest metric value;
• and
• determining from the highest metric value (a) the associated scrambling code group as the scrambling code group of the UMTS transmitter and (b) a time slot offset from the associated cyclic shift for use in acquiring frame synchronization with respect to the S time slots.

Universal Mobile Telephone System (UMTS) equipment comprising:

• a front end for receiving a wireless signal representing a secondary synchronization channel (SSCH) transmitted from a UMTS transmitter and for providing a stream of samples therefrom, the SSCH conveying a sequence of S SSCH symbols over S time slots, the sequence associated with a scrambling code group associated with the UMTS transmitter, wherein the scrambling code group is taken from a set of 64 scrambling code groups;
• a memory for storing data representative of probabilities that each one of K SSCH symbols were received in each one of the S time slots, where K>I;
• and
• a processor for (a) determining metric values from the stored data, each metric value representing a probability that a particular cyclic shift of a particular one of the 64 scrambling code groups was received;
• (b) identifying the highest metric value;
• and (c) determining from the highest metric value (1) the associated scramnbling code group as the scrambling code group of the UMTS transmitter and (2) a time slot offset from the associated cyclic shift for use in acquiring frame synchronization with respect to the S time slots.

Apparatus for use in a wireless receiver, the apparatus comprising:

• a front end for receiving a wireless signal representing a sequence of frames, and for providing a stream of samples therefrom, each frame conveying a sequence of symbols over a number of time slots, the sequence a priori being associated with a source of the wireless signal;
• a memory for storing a table of metric values, each row of the table being associated with one of M sequences of synchronization symbols, M>I, and each column of the table being associated with a cyclic shift of the M sequences;
• and
• a processor for (a) identifying the highest metric value stored in the table of metric values, (b) determining from the identified highest metric value (1) one of the M sequences of synchronization symbols as an estimate of the received sequence of symbols and (2) the associated cyclic shift for use in acquiring frame synchronization with respect to the received wireless signal.