Cell searching in a CDMA communications system

A method for a mobile station to decode an identifying code transmitted from a base station in a CDMA cellular communications system, comprising the steps of:

• receiving a plurality of consecutive symbols comprising said identifying code;
• determining whether said received plurality of consecutive symbols comprises a valid code word;
• and
• if said received plurality of consecutive symbols does not comprise a valid code word, cyclically shifting said received plurality of consecutive symbols by a predetermined amount, and returning to the determining step;
• if said received plurality of consecutive symbols comprises a valid code word, outputting a number of cyclical shifts made to obtain said valid code word and a message associated with said valid code word.

A method for a mobile station to decode an identifying code transmitted from a base station in a CDMA cellular communications system, comprising the steps of:

• collecting k times M consecutive symbols, said M consecutive symbols comprising said identifying code;
• calculating a combined likelihood value for said collected k times M consecutive symbols;
• for each of L code words and each of M cyclic shifts of said collected consecutive symbols, computing a correlation between said k times M collected consecutive symbols and all of M times L consecutive symbols obtained;
• and
• storing a code word and number of cyclical shifts made that produced a highest amount of correlation in the computing step.

A method for encoding an identifying code to be transmitted from a base station in a CDMA cellular communications system, comprising the steps of:

• computing a period for each of 2M words of length M to be encoded as said identifying code;
• excluding each of said 2M words that has a period less than M;
• for each of M cycles of a remainder of said 2M words, determining a representative word;
• and
• storing each said representative word.