Spectrum spread communication synchronization establishing apparatus using frequency offset and receiver with the same

A method of establishing synchronization in a spectrum spread communication system, comprising:

• (a) calculating correlation values from a received spectrum spread signal;
• (b) calculating power values as addition values of symbols corresponding to said correlation values and power addition values of said power values;
• (c) selecting larger ones of said power addition values to output together with timing data corresponding to said selected larger ones of said power addition values;
• (d) estimating frequency offsets from said power values and demodulation timing data to produce phase change quantities from the estimated frequency offsets;
• and
• (e) selecting path timings from said timing data based on said selected larger ones of said power addition values such that said demodulation timing data indicative of said path timings are produced,
• wherein the calculating step (b) further comprises correcting phases of either said symbols or said power values based on said phase change quantities produced in the estimating step (d).

A receiver in a spectrum spread communication system, comprising:

• m (m is an integer larger than 1) search sections, each of which calculates correlation values from a received spectrum spread signal, calculates power values as addition values of symbols corresponding to said correlation values while correcting phases of either said symbols or said power values based on phase change quantities, calculates power addition values of said power values, and selects larger ones of said power addition values to output together with timing data corresponding to said selected larger ones of said power addition values;
• a frequency offset estimating section which estimates frequency offsets from said power values for a corresponding one of said m search sections and demodulation timing data, and calculates said phase change quantities from the estimated frequency offsets to output to said corresponding search section;
• and
• a demodulation path selecting section which selects path timings from said timing data based on said selected larger power addition values for each of said m search sections and outputs said demodulation timing data indicative of said path timings to said frequency offset estimating section corresponding to said search section.

A receiver in a spectrum spread communication system, comprising:

• m (m is an integer larger than 1) search sections, each of which calculates correlation values from a received spectrum spread signal, calculates power values as addition values of symbols corresponding to said correlation values, calculates power addition values of said power values while correcting phases of said power values based on phase change quantities, and selects larger ones of said power addition values to output together with timing data corresponding to said selected larger ones of said power addition values;
• a frequency offset estimating section which estimates frequency offsets from said power values for a corresponding one of said m search sections and demodulation timing data, and calculates said phase change quantities from the estimated frequency offsets to output to said corresponding search section;
• and
• a demodulation path selecting section which selects path timings from said timing data based on said selected larger power addition values for each of said m search sections and outputs said demodulation timing data indicative of said path timings to said frequency offset estimating section corresponding to said search section.

A synchronization establishing apparatus in a spectrum spread communication system, comprising:

• a search section which calculates correlation values from a received spectrum spread signal, calculates power values as addition values of symbols corresponding to said correlation values and power addition values of said power values, and selects larger ones of said power addition values to output together with timing data corresponding to said selected larger power addition values;
• a frequency offset estimating section which estimates frequency offsets from said power values and demodulation timing data, and calculates said phase change quantities from the estimated frequency offsets to output to said search section;
• and
• a demodulation path selecting section which selects path timings from said timing data based on said selected larger ones of said power addition values and outputs said demodulation timing data indicative of said path timings to said frequency offset estimating sections,
• wherein during the calculation of said power values, said search section corrects phases of either said symbols or said power values based on said phase change quantities calculated by said frequency offset estimating section, and
• wherein said frequency offset estimating section performs frequency offset estimation by delay detection or by fast fourier transform (FFT) estimation.

A synchronization establishing apparatus in a spectrum spread communication system, comprising:

• a search section which calculates correlation values from a received spectrum spread signal, calculates power values as addition values of symbols corresponding to said correlation values and power addition values of said power values, and selects larger ones of said power addition values to output together with timing data corresponding to said selected larger ones of said power addition values;
• a frequency offset estimating section which estimates frequency offsets from said power values and demodulation timing data, and calculates phase change quantities from the estimated frequency offsets to output to said search section;
• and
• a demodulation path selecting section which selects path timings from said demodulation timing data based on said selected larger ones of said power addition values and outputs said demodulation timing data indicative of said path timings to said frequency offset estimating section,
• wherein during the calculation of said power values, said search section corrects phases of either said symbols or said power values based on said phase change quantities calculated by said frequency offset estimating section, and
• wherein said search section comprises:
• a synchronizing circuit which calculates said correlation values from said received spectrum spread signal, and calculates said power values as in-phase addition values of said symbols corresponding to said correlation values while correcting phases of either said symbols or said power values based on said phase change quantities;
• and
• a path search section which calculates said power addition values of said power values, and selects larger ones of said power addition values to output together with said timing data corresponding to said selected larger ones of said power addition values,
• wherein said synchronizing circuit comprises:
• a signal converting section which converts said received spectrum spread signal into a baseband signal;
• a sampling and holding circuit which samples and holds said baseband signal to output a sampling signal;
• a correlation unit which calculates said correlation values from said sampling signal;
• and
• a symbol integrating unit which receives said correlation values output by said correlation unit, and which inversely modulates said symbols with predetermined data and calculates said power values as said in-phase addition values of said symbols values while correcting phases of either said symbols or said power values based on said phase change quantities provided to said symbol integrating unit by said frequency offset estimating section.