System and method for CDMA channel estimation

In a code division multiple access (CDMA) communication system having a plurality of base stations asynchronously transmitting to a plurality of mobile stations, the communications from a base station to a mobile station being formatted in a plurality of coded channels including a broadcast channel message propagating along at least one transmission path, with a corresponding path delay, the broadcast channel message including predetermined time multiplexed reference and special timing symbols, wherein each base station transmits at least one traffic channel message, unique to each mobile station, each traffic channel message including time multiplexed data symbols, a method for each mobile station to receive base station communications comprising the steps of:

• a) despreading at least one broadcast channel special timing symbol;
• b) identifying a transmission path in response to each broadcast channel special timing symbol despread in Step a);
• c) despreading the broadcast channel reference symbols for each transmission path identified in Step b);
• and
• d) in response to the broadcast channel reference symbols despread in Step c), identifying at least one base station from which transmissions are being received, whereby the codes and timing for each communicating base station are derived by the mobile station;
• e) in response to broadcast channel timing determined in Step a) and the base station identification made in Step d), despreading the broadcast and traffic channel messages for each transmission path identified in Step b);
• f) in response to the broadcast channel reference symbols despread in Step e), demodulating the broadcast channel reference symbols;
• g) in response to Step f), interpolating weights and phase shifts, to demodulate the traffic channel data symbols;
• and
• h) for each base station identified in Step d), combining the traffic channel data symbols demodulated from each transmission path identified in Step b), with the weights and phase shifts interpolated in Step g), whereby the signal to noise ratio of a base station transmission is improved.

In a code division multiple access (CDMA) communication network having a plurality of base stations asynchronously transmitting information including coded communications to a plurality of mobile stations, the coded communications from a base station to a mobile station being formatted in a plurality of channels including a broadcast channel message and at least one traffic channel message, with each broadcast and traffic channel message propagated along at least one transmission path, with a corresponding path delay, the broadcast channel message including predetermined time multiplexed reference symbols and a special timing symbol, the traffic channels message including time multiplexed data symbols, wherein each base station is assigned a unique long code, and the base stations transmit broadcast channel reference symbols spread with their long code, a mobile station receiver to accept base station communications comprising:

• at least a first filter matched to despread the broadcast channel special timing symbol, said first matched filter having an input to accept the broadcast channel special timing symbol received for each transmission path from a communicating base station, and a first output to provide the despread special timing symbol for each transmission path, whereby multiplex timing information for the broadcast channel is provided;
• a timing and code management circuit having a first input operatively connected to said first matched filter output to accept despread special timing symbols for each transmission path, said timing and code management circuit having a first output to provide the despread special timing symbol for each transmission path, and a second output to provide channel multiplex timing information and base station identification for each transmission path;
• a traffic channel RAKE receiver having a plurality of fingers, each finger having an input operatively connected to said timing and code management circuit second output, each said finger using the broadcast channel multiplex timing and base station identification information provided by said timing and code management circuit to despread the traffic channel data symbols for each transmission path, whereby the timing and coding needed to despread the traffic channel results from despreading the broadcast channel;
• a searcher unit having a first input to accept the broadcast channel reference symbols for each transmission path, a second input operatively connected to said timing and code management circuit first output to accept the despread broadcast channel special timing symbol for each transmission path, said searcher unit identifying the long code for the broadcast channel received on each transmission path, said searcher unit having an output to provide the long code of the broadcast channel for each transmission path, whereby the base station is identified;
• and
• in which said timing and code management circuit includes a second input operatively connected to said searcher unit output to accept the identified broadcast channel long code for each transmission path, and in which said second output provides broadcast channel long codes, as well as channel timing information, for each transmission path.

In a code division multiple access (CDMA) communication system having a plurality of base stations asynchronously communicating to a plurality of mobile stations, the communications from a base station to a mobile station being formatted in a plurality of coded channels including a broadcast channel message and a traffic channel message propagating along at least one transmission path, with a corresponding path delay, the broadcast channel message including predetermined time multiplexed reference and special timing symbols, and the traffic channel message including time multiplexed data symbols, a method for each mobile station to synchronize communications from at least two base stations comprising the steps of:

• a) despreading at least one broadcast channel special timing symbol from each base station;
• b) establishing the broadcast channel multiplex timing for a transmission path, in response to each broadcast channel special timing symbol despread in Step a);
• c) despreading the broadcast channel reference symbols for each transmission path identified in Step b);
• d) in response to the broadcast channel reference symbols despread in Step c), identifying at least two base stations from which transmissions are being received;
• e) demodulating the broadcast channel reference symbols for each transmission path identified in Step b);
• f) in response to the broadcast channel reference symbols demodulated in Step e), refining the broadcast channel multiplex timing established in Step b);
• g) comparing the broadcast channel timing, refined in Step e) from at least two base stations;
• and
• h) in response to the comparison made in Step g), transmitting a request to one of the at least two base stations to adjust its transmission of the traffic channel, whereby the delay between the transmissions of traffic channels by different base stations is minimized.