Automated quality assessment system for cellular networks

• US 5,490,204 A
• Filed: 03/01/1994
• Issued: 02/06/1996
• Est. Priority Date: 03/01/1994
• Status: Expired due to Term

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Safco Corporation
• Inventors: Gulledge, Kenneth G.
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Grant, II, Jerome
• Application Number:
  US08/204,619
• Time in Patent Office: 707 Days
• Field of Search: 379/59, 379/34, 379/27, 379/29, 379/1, 379/22, 379/24, 379/416, 455/33.1, 455/67.1, 455/67.4, 455/54.2
• US Class Current: 455/423
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

An automated system that assesses the quality of service provided by a cellular radiotelephone system. The system uses apparatus located at a mobile station that remotely controls apparatus located at a fixed station. A cellular radiotelephone call is placed from the mobile station which is received at the fixed station. When the connection is established, commands are sent from the mobile station to the fixed station that configure and control the operation of the fixed station. Many calls between the mobile station and the fixed station are placed and received by the mobile station each under control of the mobile station. During each call, recordings are made of the progress of the call and the audio quality measurements obtained during the call from both the mobile and fixed stations perspectives. Audio quality measurements are made utilizing enhanced audio quality measurement techniques that allows simultaneous measurements of audio quality in both the uplink and downlink channels of a cellular radiotelephone call utilizing two test tones instead of the single test tone that is normally used. The results of a number of cellular radiotelephone calls are later combined to form a set of statistical indicators that effectively represent the quality of service provided by a cellular radiotelephone system. The system provides means for comparing the quality of service provided by competing cellular radiotelephone service providers and for comparing the quality of service provided by differing cellular radiotelephone technology types.

Claims

1. An automated system for assessing the quality of service determined by call progress monitoring and audio clarity measurements provided by a cellular radiotelephone system having a Mobile Telephone Switching Office (MTSO) connected to a Public Switched Telephone Network (PSTN) and uplink and downlink communication channels establishing communications between mobile and fixed stations in the radiotelephone system by transmitted audio modulated carrier signals, comprising a mobile station having a cellular radiotelephone controller and one or more cellular radiotelephones controlled by the controller, a fixed station connected to either the MTSO or PSTN that receives commands for configuration and control from the mobile station on an uplink channel, means included within the mobile station for automatically placing and receiving cellular radiotelephone calls to and from the fixed station, means included within the mobile station for remotely controlling and configuring the fixed station through an uplink channel, means included within the fixed station for automatically receiving telephone calls from the mobile station and upon direction from the mobile station placing a call to the mobile station, means for concurrently transmitting between the mobile station and the fixed station a first audio modulating tone on an uplink channel carrier signal and a different audio modulating tone on the downlink channel carrier signal, means included within the mobile station and the fixed station to measure simultaneously audio quality by measuring after demodulation the audio signal level, audio noise level and distortion of the audio signal received at each station for both the uplink and downlink channels of the cellular radiotelephone system by which the mobile and fixed stations communicate with one another, and means included within the mobile station and the fixed station for determining and recording the call progress of the downlink channel and the uplink channel utilized for communication for each cellular radiotelephone call.

2. The automated sustem for assessing the quality of service provided by a cellular radiotelephone system of claim 1 in which the control and configuration of the fixed station is reliably performed utilizing commands sent as a series of Dual-Tone Multi-Frequency (DTMF) digits sent between the mobile station and the fixed station that are acknowledged if correctly received or negatively acknowledged if received incorrectly by the fixed station using the uplink and downlink channels of the cellular radiotelephone system.

3. The automated system for assessing the quality of service provided by a cellular radiotelephone system of claim 2, comprising means for establishing a time and date reference for the mobile station, and means for recording data at the fixed station in the time and date reference of the mobile station.

4. The automated system for assessing the quality of service provided by a cellular radiotelephone system of claim 3, comprising means for combining the data recorded by the mobile station and the fixed station by comparing the date and time of the data recordings and inserting the data recorded at the fixed station into the data collected at the mobile station in appropriate time slots creating a comprehensive data recording representing the data collected at both the fixed and mobile stations.

5. The automated system for assessing the quality of service provided by a cellular radiotelephone system of claim 4, comprising means for creating statistical tables and graphs of the combined data recorded by the mobile station and the fixed station.

6. The automated system for assessing the quality of service provided by a cellular radiotelephone system of claim 1, comprising means for comparing the quality of service provided by differing cellular radiotelephone technology types by placing cellular radiotelephone calls in close time relationship on each of the differing cellular radiotelephone networks including analog to analog, analog to digital, or digital to digital utilizing a plurality of cellular radiotelephones contained within the same mobile unit

7. The automated system for assessing the quality of service provided by a cellular radiotelephone system of claim 1, comprising means for enhanced audio quality measurements which allows simultaneous measurements in both the forward and reverse channel paths of a cellular radiotelephone call.

8. A method for obtaining simultaneous measurements of audio quality relating to the audio signal level, audio noise level and audio distortion level of the audio signal after demodulation in both the voice uplink and downlink carrier signals of a cellular radiotelephone call between a mobile station and a fixed station which are placed in a communication link with one another by a supervisory audio tone, comprising the steps of:

concurrently transmitting a first test audio modulating tone on the uplink channel carrier signal and a different test audio modulating tone on the downlink channel carrier signal both of which audio modulating tones are at lower audio frequencies than the supervisory audio tone,

removing by filtering from both of the received audio signal tones any portion of the transmitted audio tone which is echoed back from each of the receiving stations to each of the transmitting stations, and

performing at each of the fixed and mobile stations independent simultaneous audio quality measurements which relate to audio signal level, audio noise level and audio distortion level of the audio test signal received at that station.

9. The method for obtaining simultaneous measurements of audio quality of claim 8 in which the independent audio quality measurements are performed by a SINAD measurement technique accomplished by the formula ##EQU2## where the terms signal, noise, and distortion all relate to audio signal levels after demodulation.

10. The method for obtaining simultaneous measurement of audio quality of claim 9 in which the independent audio quality measurements are performed by a C message weighted SINAD measurement technique.

11. The method for obtaining simultaneous measurements of audio quality of claim 8 in which the independent audio quality measurements are performed by a C weighted notched noise measurement technique.

12. The method of claim 8 including call progress monitoring, comprising the steps of:

(a) monitoring a cellular radiotelephone call between the fixed and mobile stations for service indication, and if no service indication is present the call progress is identified as a no service call, otherwise proceed to step (b);

(b) monitoring the cellular radiotelephone call for ROAM indication, and if ROAM indication is present then the call progress is identified as a ROAM call, otherwise proceed to step (c);

(c) placing a radiotelephone call and monitoring the cellular radiotelephone call for a voice channel assignment, and if a voice channel is not assigned to the attempted cellular radiotelephone call within a specified time call progress is identified as a blocked call, otherwise proceed to step (d);

(d) effecting audio quality measurements for a predefined time interval, and if during the audio quality measurement period the call is prematurely terminated then the call progress is identified as a dropped call, otherwise proceed to step (e); and

(e) terminating the cellular radiotelephone call, and if the noise measurements made during step (d) exceed a measurement threshold then the call progress is identified as a noisy call, and if during the call of step (d) SAT fades are observed the cell progress is identified as a call with SAT fades, and if during the call of step (d) excessive handoffs are observed the cell progress is identified as a call with excessive handoffs, and if during the call of step (d) strong signal strengths are observed on the adjacent channels the call progress is identified as a call with loud adjacent channels, otherwise the call progress is identified as a good call.