Quality measurement method and apparatus for wireless communicaion networks

• US 5,987,320 A
• Filed: 07/17/1997
• Issued: 11/16/1999
• Est. Priority Date: 07/17/1997
• Status: Expired due to Term

• Current Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Llc Lcc
• Inventors: Bobick, David A.
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): Craver, Charles R
• Application Number:
  US08/895,874
• Time in Patent Office: 852 Days
• Field of Search: 455/423, 455/33.1, 455/67.1-67.3, 455/54.2, 455/424, 455/425, 455/501, 455/63, 455/67.4, 381/48, 379/59, 375/224, 704/831, 395/2.37, 370/241-249, 370/336
• US Class Current: 455/423
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

An quality testing apparatus and method for providing an objective and real-time evaluation of voice quality in a wireless communication system. The system under evaluation would include a receiving and transmitting apparatus at both ends of the system. To evaluate voice quality, one apparatus transmits a TDM base band voice test signal to a receiving apparatus. The configuration of the transmitted TDM base band voice test signal permits the receiving end to synchronize a test sentence, contained within the TDM test signal, with a corresponding reference sentence stored at the receiving apparatus. After synchronization, the receiving apparatus uses a model of human hearing to objectively compare the two sentences, and based on the result, outputs an AQS ranking. In addition to voice quality, the apparatus measures SINAD, noise, distortion, and signal level of transmitted test tones and maintains a log of call progress statistics.

Claims

1. A quality testing apparatus comprising:

a transceiver circuit, wherein the transceiver circuit receives voice test signals and audio test tone signals from a mobile test terminal, and wherein the transceiver circuit transmits voice test signals and audio test tone signals to the mobile test terminal;

a voice signal generating unit, connected to the transceiver, wherein the voice signal generating unit generates a time division multiplexed (TDM) base band signal, wherein the TDM signal includes at least one test sentence and at least one synchronization pulse, and wherein the at least one synchronization pulse identifies a time slot containing the at least one, test sentence;

a voice quality measuring unit connected to the transceiver, wherein the voice quality measuring unit objectively determines the quality of a received voice test signal by comparing the received voice signal with a series of reference sentences and ranking the comparison against a predetermined set of parameters;

a test tone generating unit, connected to the transceiver, wherein the test tone generating unit generates an audio test tone signal;

a signal quality measuring unit connected to the transceiver, wherein the signal quality measuring unit measures the signal quality of the audio test tone signal received from the mobile test terminal;

a communication exchange register connected to the voice quality measuring unit and the voice signal generating unit; and

a control processor coupled to the communication exchange register, wherein the control processor transmits either a tone generation command signal or a voice generation command signal when the apparatus operates in a generation mode, and wherein the control processor transmits a test tone measurement command signal when the apparatus operates in a measurement mode.

2. The apparatus of claim 1, wherein the transceiver circuit further includes

an analog to digital converter (ADC) connected to the voice quality measuring unit and the signal quality measuring unit, wherein the ADC converts the received voice test signal to a first digital signal, and wherein the ADC converts the received audio test tone signal to a second digital signal;

and

a digital to analog converter (DAC) connected to the test tone generating unit and the voice signal generating unit, wherein the DAC converts the audio test tone to a first analog signal, and wherein the DAC converts the TDM signal to a second analog signal.

3. The apparatus in claim 2, wherein the ADC samples the received voice signal to ensure real-time calculations, and wherein the voice quality measuring unit further includes

a synchronization circuit connected to the ADC, wherein the synchronization circuit synchronizes the first digital signal with one sentence in the series of reference sentences;

a first filter bank connected to the synchronization circuit, wherein the first filter bank filters the synchronized digital signal;

a subtractor section, coupled to the first filter bank and a second filter bank, wherein the second filter bank is identical to the first filter bank, wherein the second filter bank filters the synchronized reference sentence, and wherein the subtractor outputs a difference signal by subtracting an output of the first filter bank from an output of the second filter bank; and

a comparator section connected to the subtractor section, wherein the comparator compares the difference signal with a set of predefined parameters and outputs a ranking based on the comparison result.

4. The apparatus in claim 3, wherein the synchronization circuit includes

a clock circuit;

a phase lock loop circuit connected to the clock circuit for capturing a time slot of the digital signal;

a frame detector unit, coupled to the clock circuit and the phase lock loop circuit, wherein the frame detector unit identifies the test sentence in the captured time slot by identifying the synchronization pulse contained in the time slot; and

a frame number setup unit, connected to the frame detector unit, for selecting a time frame, wherein the time frame selected contains at least one reference sentence and the synchronization pulse corresponding to the synchronization pulse in the captured time slot.

5. The apparatus in claim 4, wherein the voice quality measuring unit further includes a memory, wherein the memory stores a set of predefined Aural Quality Score (AQS) parameters, and wherein the comparator section compares the difference signal with the set of AQS parameters to determine an AQS ranking.

6. The apparatus of claim 1, further including

a call progress unit connected to the communication exchange register, wherein the call progress unit collects call process statistics of the wireless system;

and

a communication port connected to the communication exchange register, wherein the communication port connects the apparatus to an external data collection device.

7. The apparatus in claim 6, wherein the external data collection device is a computer terminal and display.

8. The apparatus in claim 1, wherein the signal quality measuring unit continually measures a test tone signal level, a test tone noise level, and SINAD of the received test tone signal.

9. A method for testing the voice audio quality of a wireless communication network, the method comprising:

transmitting a test signal from a mobile testing terminal, wherein the test signal is a TDM audio signal including a series of time slots, wherein at least one time slot contains a test sentence and an identifying synchronization pulse;

receiving, at a quality testing apparatus, an analog signal, wherein the analog signal corresponds to the transmitted test signal plus an RF distortion signal;

converting the received analog signal to a digital signal by sampling the analog signal for real-time evaluation;

synchronizing the digital signal with a corresponding reference signal using the identifying synchronization pulse received with the digital signal;

filtering the test signal with a first critical-band IIR filter bank;

subtracting the filtered test signal from the synchronized reference signal to produce a difference signal;

comparing the difference signal with a set of predefined parameters to objectively determine a quality ranking score; and

outputting the quality ranking score.

10. The method of claim 9, wherein the step of transmitting further includes

generating the TDM audio signal;

converting the TDM audio signal to an RF signal; and

transmitting the RF signal over a wireless transmission medium.

11. The method of claim 10, wherein the step of synchronizing the digital signal further includes

capturing the at least one time slot containing the test sentence and the synchronization pulse;

identifying the test sentence contained in the captured by determining the synchronization pulse contained in the captured time slot; and

selecting a reference sentence within the reference signal corresponding to the identified test sentence by matching the synchronization pulse contained in the captured time slot with a reference synchronization pulse identifying the reference sentence.

12. The method of claim 11, wherein the quality testing apparatus includes a set of input filters and a control processor, and wherein the step of receiving includes the step of

filtering the analog signal with a high-pass IIR filter.

13. The method of claim 12, wherein the quality testing apparatus includes an analog to digital converter (ADC), and wherein the step of converting further includes

sampling the filtered analog signal at a rate of 8 KHz or above to produce this digital signal.

14. The method of claim 13, wherein the first critical-band filter bank contains at least 32 critical band elliptical IIR filters, and wherein the step of filtering further includes the steps of

outputting a filtered signal from each of the 32 filters;

computing a first power signal of each filtered signal by integrating each filtered signal over a sampling time; and

normalizing the first power signal to form a power vector.

15. The method of claim 14, wherein the synchronized reference signal is processed by a second filter bank that is identical to the first filter bank, and wherein the step of subtracting includes the steps of

subtracting the power vector from the a second power vector determined from the synchronized reference sentence to form a first order difference signal;

computing a spectral slope vector of the first order difference signal;

squaring the magnitude of the spectral slope vector to form a magnitude squared signal; and

integrating the magnitude squared signal over a predetermined interval to produce an average signal.

16. The method in claim 15, wherein the quality testing apparatus stores a set of AQS parameters, and wherein the step of comparing includes the steps of

mapping the average signal against the set of AQS parameters;

and

objectively determining an AQS ranking based on the mapping.

17. A wireless communication system comprising:

a land-line quality testing unit configured to test the total quality of the wireless communication system by measuring an audio quality of a received time division multiplexed (TDM) base band voice test signal and an audio test tone signal, wherein land-line quality testing unit includes a control processor configured to transmit a measurement command signal when the land-line unit operates in a measurement mode;

a modem connected to the land-line quality testing unit, wherein the land-line quality testing unit generates TDM base band voice test signals and audio test tone signals, and wherein the modem transmits the signals to a mobile switching station, and wherein the mobile switching station is coupled to a base station controller;

a mobile quality testing unit connected to a wireless mobile telephone test terminal for receiving the TDM base band voice test signal and the audio test tone signals transmitted by the modem, wherein the telephone test terminal is coupled to the base station controller, and wherein the base station controller receives the TDM base band voice test signal and the audio test tone signals from the mobile switching station; and

wherein the mobile quality testing unit also transmits TDM base band voice test signals and audio test tone signals to the land-line quality testing unit via the modem.

18. The system of claim 17, further including

a first data collection device, wherein the first data collection device is a computer terminal connected to the land-line quality testing unit.

19. The system of claim 17, further including

a second data collection device, wherein the second data collection device is a computer terminal connected to the mobile quality testing unit.

20. The system of claim 17, wherein the land-line quality testing unit includes

means for receiving an RF signal, wherein the RF signal corresponds to either the TDM base band voice test signal or an audio test tone signal;

means for converting the received RF signal to a digital signal, wherein the digital signal corresponds to either the TDM base band voice test signal or the audio test tone signal;

means for objectively determining the audio quality of the digital signal by comparing the digital signal to a series of phonetically balanced sentences and ranking the comparison against a predetermined set of parameters, and wherein the digital signal corresponds to the TDM base band voice test signal;

means for measuring the signal quality of the digital signal, wherein the digital signal corresponds to the audio test tone signal; and

means for collecting call process statistics of the wireless system and providing the statistics for real-time evaluation.

21. The system of claim 20, wherein the land-line quality testing unit operates in a measurement mode, and wherein the land-line quality testing unit further includes

a communication exchange register connected to the means for objectively determining the audio quality, the means for measuring the signal quality, the means for collecting and the control processor;

and

a communication port connected to the communication exchange register and coupling the land-line quality testing unit to the external data collection device.

22. The system of claim 20, wherein means for measuring the signal quality continually measures a test tone signal level, a test tone noise level, and a SINAD value of the digital signal.

23. The system of claim 20, wherein means for converting samples the received RF signal to ensure a real-time calculation, and wherein the means for objectively determining audio voice quality further includes

means, connected to the means for converting, for selecting one reference sentence in the series of reference sentences that corresponds to a test sentence in the digital signal;

means, connected to the means for selecting, for filtering the digital signal;

means for subtracting the filtered digital signal from the selected reference sentence and continually outputting a difference signal; and

means for comparing the difference signal with a set of predefined parameters and outputting a ranking based on the difference signal.

24. The system of claim 23, wherein the means for selecting includes

means for generating a continuous clock signal;

means, connected to the means for generating, for capturing a time slot of the digital signal;

means for identifying the test sentence contained in the time slot by identifying the synchronization pulse contained in the captured time slot; and

means for selecting a time frame, wherein the time frame selected contains a synchronization pulse corresponding to the synchronization pulse of the captured time slot.

25. The system of claim 21, wherein the means for objectively determining further includes

means for storing a predefined set of Aural Quality Score (AQS) parameters;

means for comparing the difference signal with the set of AQS parameters to determine an AQS ranking.

26. The system of claim 20, wherein the land-line quality testing unit further includes

means for generating the audio test tone signal;

means for generating the TDM base band voice test signal, wherein the TDM signal includes at least one reference sentence and at least one synchronization pulse for identifying a time slot containing the reference sentence;

means for converting the generated audio test tone signal and the generated TDM base band voice test signal to analog representations; and

means for transmitting the analog representations over an RF medium.

27. The system of claim 26, wherein the land-line quality testing unit operates in a generate mode, wherein the control processor transmits a generate command signal, and wherein the communication exchange register is connected to the means for generating the TDM base band signal and the means for generating the audio test tone signal.

28. The system of claim 17, wherein the land-line quality testing unit and the mobile quality testing unit are equivalent devices.

29. A method for testing the voice audio quality of a wireless communication network, the method comprising:

transmitting a test signal from a mobile testing terminal;

receiving, at a quality testing apparatus, an analog signal, wherein the analog signal corresponds to the transmitted test signal plus an RF distortion signal;

converting the received analog signal to a digital signal by sampling the analog signal for real-time evaluation;

synchronizing the digital signal with a corresponding reference signal using an identifying synchronization pulse received with the digital signal;

filtering the test signal with a first critical-band IIR filter bank;

subtracting the filtered test signal from the synchronized reference signal to produce a difference signal;

comparing the difference signal with a set of predefined parameters to objectively determine a quality ranking score; and

outputting the quality ranking score.