Patent ID: 7231211

Claim:
A method of monitoring communications in a trunked communication system comprising the steps performed by a monitoring system of: setting both an appropriate data and sampling rate, wherein the sampling rate is set to a level which is higher than a maximum expected trunking control channel data rate; receiving a plurality of digital data messages on a control channel transmitted from at least one trunking radio system wherein each digital data message includes a preamble and a coded information frame; identifying the polarity of the incoming digital data messages; sampling the received digital message at the sample rate; identifying type and data rate of the trunking system, wherein the type and date rate are identified by comparing incoming samples to pre-calculated set of preamble patterns; calculating a plurality of parameters and values based on the data characteristics that allows a decoding element of the monitoring system to be suitably receive and reconstruct the coded information frame for the apposite radio system and at the appropriate data rate further comprising the steps of; calculating the required values and parameters of the bit phase compensation table; generating a subset of the preamble message; calculating the preamble test value that allows the correlator array to establish the type of radio system and speed at which the radio system is transmitting its digital message; computing the inverse preamble test value used for the data messages of those radio systems that are found inverted radio system; generating a plurality of correlator mask values that are calculated for each test value that the correlator array uses to select the data bits in the preamble to compared; determining an appropriate preamble alignment interval; selecting an appropriate set of parameters and values based upon the system type identified; and reconstructing the stream of digital messages by selecting samples from the sample data stream to produce an output data stream.