Initial synchronization method and receiver for DS-CDMA inter base station asynchronous cellular system

A receiver for a DS-CDMA inter base station asynchronous cellular system, which uses plurality of synthesized spread code sequences, each synthesized spread code sequence being synthesized from one of different long codes corresponding to a cell and one of a plurality of short codes corresponding to communication channels, wherein a specific short code common to each of the cells is assigned to a control channel, comprising:

• (1) a spread code generating means which outputs segments of the synthesized spread code sequences by synthesizing a different long code and the specific short code, each segment being taken from a portion of a respective one of the synthesized spread code sequences, starting from a first position in a first of the synthesized spread code sequences from where a first segment is taken, and in successive synthesized spread code sequences, starting from a position in each successive synthesized spread code sequence which is shifted by a predetermined shifting amount from where a preceding segment was taken from a preceding one of the synthesized spread code sequences, the predetermined shifting amount being less than a length of each segment;
• (2) a matched filter which finds a correlation between the segment being output by the spread code generating means and a received signal;
• (3) a long code synchronization timing determination means which determines a long code synchronization timing transmitted from a corresponding base station, based on a correlation between the specific short code and the received signal;
• and
• (4) a long code identification means which:
• (a) loads the first segment to the matched filter from the spread code generating means based on the long code synchronization timing;
• (b) sequentially supplies successive ones of the segments every time a length of the received signal substantially equal to the shifting amount is newly input to the matched filter;
• and
• (c) identifies the long code transmitted from the corresponding base station based on the magnitude of electric power in an output signal of the matched filter.

A mobile station for a DS-CDMA inter base station asynchronous cellular system which uses a plurality of synthesized spread code sequences, each synthesized spread code sequence being synthesized from (a) a long code corresponding to a cell and (b) one of a plurality of short codes corresponding to communications channels, wherein a specific short code common to each of the cells is assigned to a control channel, the mobile station comprising:

• (1) a receiver for receiving a high frequency signal carrying a synthesized spread code sequence and providing an output signal carrying the synthesized spread code sequence at an intermediate frequency;
• (2) a demodulator for demodulating the output signal from the receiver and providing a baseband signal corresponding to the synthesized spread code sequence;
• (3) a spread code generator for outputting segments of synthesized spread code sequences, each synthesized spread code sequence being synthesized from a different long code corresponding to a respective one of the cells and the specific short code, each segment being taken from a portion of a respective one of the synthesized spread code sequences, starting from a first position in a first of the synthesized spread code sequences from where a first segment is taken, and in successive synthesized spread code sequences, starting from a position in each successive synthesized spread code sequence which is shifted by a predetermined shifting amount from where a preceding segment was taken from a preceding one of the synthesized spread code sequences, the predetermined shifting amount being less than a length of each segment;
• (4) a matched filter for finding a correlation between the segments being output by the spread code generator and the baseband signal;
• (5) a long code synchronization timing determiner for determining a long code synchronization timing transmitted from a corresponding base station, based on a correlation between the specific short code and the baseband signal;
• and
• (6) a long code identificater for:
• (a) loading the first segment to the matched filter from the spread code generator based on the long code synchronization timing;
• (b) sequentially loading and replacing successive ones of the segments every time a length of the baseband signal substantially equal to the shifting amount is newly input to the matched filter;
• and
• (c) identifying the long code transmitted from the corresponding base station based on the magnitude of electric power in an output signal from the matched filter.