Apparatus and method for monitoring a trunked radio communications system

• US 7,231,211 B2
• Filed: 07/24/2002
• Issued: 06/12/2007
• Est. Priority Date: 07/24/2002
• Status: Expired due to Fees

• Current Assignee: Signal Intelligence, Inc.
• Original Assignee: Signal Intelligence, Inc.
• Inventors: Dunham, Sam
• Primary Examiner(s): Anderson; Matthew
• Assistant Examiner(s): Aminzay; Shaima Q.
• Application Number:
  US10/205,422
• Publication Number:
  US 20040018832A1
• Time in Patent Office: 1,784 Days
• Field of Search: 455/426.1, 455/520, 455/553.1, 455/518, 370/327, 370/340, 379/12, 379/112, 379/97, 379/232, 379/235, 379/236, 379/249, 379/246, 379/26, 379/1
• US Class Current: 455/426.1
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

The present invention provides a method and apparatus for monitoring a trunked radio communications system by using some type of radio scanning receiver that is not designed for that purpose. In addition, the invention provides a method for automatically determining the polarity of the received control channel data. Further, the invention provides a method for automatically determining the type of trunked radio communications system. In addition the invention provides a method for automatically determining the channels in a trunked radio system and a method for automatically determining the bit rate of transmitted digital signals over a control channel of a trunked radio communications system.

Claims

1. 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.

2. The method as recited in claim 1, wherein if the polarity of the data stream of an incoming digital data message is negative, inverting the polarity of that data stream to be positive.

3. The method as recited in claim 1, includes the step of searching a selected frequency band to discover a logical channel to frequency associations.

4. The method as recited in claim 1, wherein the selected sample rate must be high enough so as to generate a bit phase compensator table can be built that encompasses all required incoming bits.

5. The method as recited in claim 1, wherein the plurality of parameters and values are stored in at least one lookup table.

6. The method as recited in claim 1, wherein the codes that specify the talk group and channel assignment are extracted from the reconstructed coded information frame.

7. The method as recited in claim 6, wherein the talk group and channel assignment codes are compared to an array of stored, predefined codes.

8. The method as recited in claim 7, wherein if the codes match tuning the frequency tuned radio receiver of the monitoring system to the appropriate working voice channel and monitoring the resultant radio communications traffic.

9. A system for monitoring analog voice communications traffic in a truncked radio communications system, including:

a computational device with input and output devices and a sound card, said computational device capable of reading stored executable code;

said stored executable code including;

a code segment instructing devices of the monitoring system to be configured to set both an appropriate data and sampling rate, wherein the sampling rate is set to a level at which is higher than the data rate;

a code segment instructing said computational device to receive 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;

a code segment for identifying the polarity of the incoming digital data messages;

a code segment instructing said computational device to sample the received digital message at the sample rate;

a calculating code segment instructing said computational device to calculate a plurality of parameters and values based on the data characteristics that allows a decoding element of the monitoring system to be suitably received and reconstruct the coded information frame for the apposite radio system and at the appropriate data rate, said calculating code segment including;

instructions for calculating the required values and parameters of the bit phase compensation table;

instructions for generating a subset of the preamble message;

instructions for 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;

instructions for computing the inverse preamble test value used for the data messages of those radio systems that are found inverted radio system,

instructions for 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;

instructions for determining an appropriate preamble alignment interval;

instructions for selecting an appropriate set of parameters and values based upon the system type identified;

instructions for reconstructing the stream of digital messages by selecting samples from the sample data stream to produce an output data stream.

10. The system recited in claim 9, wherein said code includes instructions if the polarity of the data stream of an incoming digital data message is negative, inverting the polarity of that data stream to be positive.

11. The system as recited in claim 9, wherein said code includes instructions searching a selected frequency band to discover a logical channel to frequency associations.

12. The system as recited in claim 11, where said code includes instructions to select a sample rate high enough so as to generate a bit phase compensator table built to encompass all required incoming bits.

13. The system as recited in claim 9, wherein said code includes instructions to store the plurality of parameters and values in at least one lookup table.

14. The system as recited in claim 9, wherein said code includes instructions for extracting the codes that specify the talk group and channel assignment from the reconstructed coded information frame.

15. The system as recited in claim 9, wherein said code includes for comparing the talk group and channel assignment codes to an array of stored, predefined codes.

16. The system as recited in claim 15, wherein said code includes instructions for configuring to tune the frequency tuned radio receiver of the monitoring system to the appropriate working voice channel and monitoring the resultant radio communications traffic, if the codes match.

17. The system as recited in claim 9, wherein said sampling rate is linearly related to a sampling rate of said sound card.

18. A system for monitoring communications in a trunked communication system comprising of:

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to set both an appropriate data and sampling rate, wherein the sampling rate is set higher than the data rate is a linear function of a sampling rate of a sound card;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to receive 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;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to identify the polarity of the incoming digital data messages;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to sample the received digital message at the sample rate;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to calculate 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;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to calculate the required values and parameters of the bit phase compensation table;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to generate a subset of the preamble message;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to calculate 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;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to compute the inverse preamble test value used for the data messages of those radio systems that are found inverted radio system;

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to generate 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; and

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to determine an appropriate preamble alignment interval; and

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to select an appropriate set of parameters and values based upon the system type identified; and

circuitry of a monitoring system configured to a computer readable program code devices of the monitoring system configured to reconstruct the stream of digital messages by selecting samples from the sample data stream to produce an output data stream.

19. The apparatus as recited in claim 18, wherein if the polarity of the data stream of an incoming digital data message is negative, inverting the polarity of that data stream to be positive.

20. The apparatus as recited in claim 18, includes the step of searching a selected frequency band to discover a logical channel to frequency associations.

21. The apparatus as recited in claim 18, wherein the circuitry of the monitoring system sets the selected sample rate high enough so as to generate a bit phase compensator table can be built that encompasses all required incoming bits.

22. The apparatus as recited in claim 18, wherein the circuitry of the monitoring system stores the plurality of parameters and values in at least one lookup table.

23. The apparatus as recited in claim 18, wherein the circuitry of the monitoring system extracts the codes that specify the talk group and channel assignment from the reconstructed coded information frame.

24. The apparatus as recited in claim 23, wherein the circuitry of the monitoring system compares the talk group and channel assignment codes to an array of stored, predefined codes.

25. The apparatus as recited in claim 24, wherein the circuitry of the monitoring system tunes the frequency tuned radio receiver of the monitoring system to the appropriate working voice channel and monitoring the resultant radio communications traffic, if the codes match.