Method and apparatus to determine the frequency and time slot position in a digital wireless communication session

A digital wireless communication method between a first unit and a second unit, wherein said first unit transmits a digitally encoded signal at a first frequency, and wherein said transmission is subject to deviation in frequency upon arrival at said second unit, said method comprising:

• receiving said digitally encoded signal by said second unit;
• sampling said digitally encoded signal by said second unit to produce a first sampled digital signal;
• supplying said first sampled digital signal to a plurality of first digital filter means simultaneously, with each of said first digital filter means being a match filter tuned to a frequency range different from one another, to produce a plurality of second sampled digital signals with each having an amplitude;
• selecting the second sampled digital signal having the largest amplitude and selecting the first digital filter means producing the selected second sampled digital signal;
• supplying said selected second sampled digital signal to a plurality of second digital filter means simultaneously, with each of said second digital filter means being a match filter tuned to a frequency range different from one another, to produce a plurality of third sampled digital signals with each having an amplitude;
• and
• selecting the third sampled digital signal having the largest amplitude and selecting the second digital filter means producing the selected third sampled digital signal.

A digital cellular communication system for communicating between a mobile unit and a first base station unit with each transmitting a digitally encoded signal at a frequency to the other, each of said units comprising:

• antenna means for receiving the digitally encoded signal transmitted by the other unit;
• means for sampling said digitally encoded signal to produce a first sampled digital signal;
• a plurality of first digital filter means for receiving said first sampled digital signal simultaneously, each of said first digital filter means being a match filter tuned to a frequency range different from one another for producing a plurality of second sampled digital signals with each having an amplitude;
• means for receiving said plurality of second sampled digital signals and for selecting the second sampled digital signal with the largest amplitude, and for selecting the first digital filter means producing said selected second sampled digital signal;
• a plurality of second digital filter means for receiving said selected second sampled digital signal simultaneously, each of said second digital filter means being a match filter tuned to frequency range different from one another for producing a plurality of third sampled digital signals with each having an amplitude;
• and
• means for receiving said plurality of third sampled digital signals and for selecting the third sampled digital signal with the largest amplitude and for selecting the second digital filter means producing said selected third sampled digital signal.