Receiving method and apparatus for use in a spread-spectrum communication system

A receiving method for use in a code division multiple access (CDMA) communication system wherein a spread-spectrum signal containing information bits is transmitted within an environment tending to produce multipath components, the method comprising the steps of:

• receiving a spread-spectrum signal having multipath components;
• selecting one or more of such multipath components based on predetermined selection criteria;
• determining time delays between such selected multipath components;
• determining weighting factors for such selected multipath components;
• processing the spread-spectrum signal by operation thereon by time-delayed versions of a user-correlation signal to produce processed signal components, such time-delayed versions of the user-correlation signal being delayed according to the determined time delays of the selected multipath components;
• integrating each processed signal component during a predefined time period to produce corresponding integration results;
• multiplying each integration result by a corresponding determined weighting factor to produce weighted products;
• summing the weighted products from the predefined time period to produce a summed output;
• and
• decoding the summed output by quantizing such output and comparing such output to a predefined threshold value, thereby to extract the information bits from the summed output.

For use in receiving apparatus of a code division multiple access (CDMA) communication system which includes a rake receiver for presenting multipath components of a received spread-spectrum signal on plural diversity branches and a combiner for combining outputs of the diversity branches to produce a combined signal and a decoder for decoding the combined signal to extract coded information from the combined signal, the improvement comprising:

• an adaptive search engine which receives the spread-spectrum signal and a cell-correlation signal, the engine being coupled to the combiner to identify selected multipath components of the spread-spectrum signal for combination, the search engine including:
• a slope signal generator for generating successive time delay values;
• a variable time delay which receives time delay values from said slope signal generator to produce successive time-delayed versions of the cell-correlation signal;
• a processor arrangement which processes the spread-spectrum signal by operation thereon by said successive time-delayed versions of the cell-correlation signal to produce successive multipath correlation components;
• an integrator for integrating each successive multipath correlation component over a predefined interval of time to produce successive integration results;
• and
• a tracking engine for tracking a predefined number of maximal integration results produced by said integrator and determining corresponding weighting factors for use by the combiner.

For use in a communication system which employs a spread-spectrum signal having multipath components, a receiving apparatus comprising:

• a search engine which receives the spread-spectrum signal for operation thereon by a first quantity of time-delayed versions of a cell-correlation signal, said search engine being configured to select a second lesser, quantity of multipath components based on predetermined selection criteria and being configured to produce time delay signals representing the time delay between such selected multipath components and weighting factors for each selected multipath component;
• a combiner for weighing said selected multipath components using said weighting factors and combining such weighted multipath components in a predetermined manner to produce a combined signal;
• and
• a decoder operatively coupled with said combine to extract information from the combined signal.

A receiving apparatus for use in a code division multiple access (CDMA) communication system which receives a spread-spectrum signal having multipath components, the receiving apparatus comprising:

• an adaptive search engine which dynamically tracks the multipath components of the spread-spectrum signal for selecting multipath components with a maximal level of correlation between the multipath component and a cell-correlation signal, said search engine including a multiplier for multiplying the received signal by time-delayed versions of said cell-correlation signal to produce multipath correlation components, said search engine further including an integration arrangement for integrating each multipath correlation component over an information bit time interval;
• a diversity receiver including plural diversity branches, each of which receives a selected multipath component;
• a combiner for combining the diversity branches in a predetermined manner to produce a combined signal, thereby to increase diversity gain;
• and
• a decoder operatively coupled with said combiner to extract information.

A method for increasing diversity gain in a code division multiple access (CDMA) communication system, the method comprising the steps of:

• receiving a spread-spectrum signal having multipath components;
• determining a signal-to-noise power ratios of each multipath component by a sliding average approach;
• selecting one or more of the multipath components with maximal signal-to-noise power ratios as determined by said sliding average approach;
• combining the selected multipath components in such manner as to maximize diversity gain, thereby to produce a combined signal representing such selectively combined maximized-gain diversity components;
• and
• decoding the combined signal to extract information from the combined signal.