Link quality analyzer
First Claim
1. A line quality analyzer for measuring the quality of communication links in a communications system comprising:
- means for transmitting information over a selected communication link;
means for generating a plurality of signal tones and coupling those tones for transmission by said means for transmitting over said communication link;
means for receiving said plurality of transmitted tones and any noise on said communication link to obtain a received signal;
means for time domain sampling said received signal to obtain a set of N blocks of digitized samples with each block having M samples, where M and N are integers;
Fast Fourier Transform means for transforming the blocks of M digitized samples from the time domain to the frequency domain; and
measuring means for detecting the frequency spreads for each of the plurality of transmitted tones and for detecting the multipath time delay spreads represented by received envelopes of at least each tone pair contained within the plurality of transmitted tones to obtain link quality parameters representing the quality of said communication link.
2 Assignments
0 Petitions
Accused Products
Abstract
A link quality analyzer measures the link quality between a calling station and a called station by continuously transmitting a plurality of signal tones. The called station receives the plurality of transmitting tones and sample them. A power spectrum is obtained of the received tones. From the statistics of the power spectrum the parameters of signal-to-noise ratio, multipath delay spread, Doppler frequency spread, frequency offset statistics, frequency-amplitude correlation, average amplitude response versus frequency, signal fading statistics, harmonic and intermodulation distortions, RMS-to-mean signal ratio, noise profile, and various noise statistics are determined. The power spectrum of the plurality of tones is measured through the use of digital sampling techniques and digital fast Fourier transform techniques that are implemented through microprocessor-level technology.
56 Citations
21 Claims
-
1. A line quality analyzer for measuring the quality of communication links in a communications system comprising:
-
means for transmitting information over a selected communication link; means for generating a plurality of signal tones and coupling those tones for transmission by said means for transmitting over said communication link; means for receiving said plurality of transmitted tones and any noise on said communication link to obtain a received signal; means for time domain sampling said received signal to obtain a set of N blocks of digitized samples with each block having M samples, where M and N are integers; Fast Fourier Transform means for transforming the blocks of M digitized samples from the time domain to the frequency domain; and measuring means for detecting the frequency spreads for each of the plurality of transmitted tones and for detecting the multipath time delay spreads represented by received envelopes of at least each tone pair contained within the plurality of transmitted tones to obtain link quality parameters representing the quality of said communication link. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A link quality analyzer for measuring the quality of communication links between a transmitting station and a receiving station comprising:
-
line quality analyzer signal generator means for transmitting a plurality of signal tones over a communication link; receiver means for receiving the plurality of transmitted tones and link noise to obtain a received signal; sampling means for time domain sampling the received signal to obtain a set of N blocks of digitized samples with each block having M samples; Fast Fourier Transform means for transforming the blocks of M digitized samples from the time domain to the frequency domain; and means for measuring the transformed signals to obtain link quality parameters for the N blocks of M samples where M and N are positive integers, said means for measuring comprising; indexing means for indexing the transformed signals according to frequency to obtain a power spectrum of the plurality of signal tones and link noise in sets of sample time, frequency offset measuring means for measuring the frequency offset of each of the plurality of tones from the power spectrum, accumulator means for accumulating the power spectrum of subsequent reception of the plurality of tones and link noise to obtain an accumulated spectrum, storage means for storing each power spectrum of each set of plurality of tones and link noise as well as the frequency offset, and post acquisition measuring means for measuring link quality parameters representing the quality of said communication link from the accumulated spectra, each tone power spectrum, and the frequency offset, said post acquisition measuring means further including; average frequency offset measuring means for obtaining an average frequency offset for each tone, RMS frequency offset value detector means for detecting an RMS frequency offset value for each tone, correlator means for obtaining amplitude correlation coefficients for each of the plurality of transmitted tones from the N blocks of M samples, frequency spread detector means for detecting frequency spreads for each of the plurality of transmitted tones from the N blocks of M samples, envelope detector means for detecting received envelopes for each tone of the plurality of transmitted tones, multipath time delay spread detector means for detecting multipath delay spreads as indicated by the received envelopes of each tone pair contained within the plurality of transmitted tones, multipath time delay spread detector means for detecting multipath time delay spread as indicated by the received envelopes of each of the tone triplets contained within the plurality of transmitted tones, harmonic measuring means for detecting the second and third harmonics for each of the plurality of transmitted tones, and intermodulation distortion measuring means for measuring intermodulation products due to pairs of the plurality of transmitted tones.
-
-
11. A method for measuring the quality of communication links in a communications system comprising:
-
transmitting information over a selected communication link; generating a plurality of signal tones and coupling those tones for transmission over said communication link; receiving said plurality of transmitted tones and any noise on said communication link to obtain a received signal; time domain sampling said received signal to obtain a set of N blocks of digitized samples with each block having M samples, where M and N are integers; transforming the blocks of M digitized samples from the time domain to the frequency domain by Fast Fourier Transform; and detecting the frequency spreads for each of the plurality of transmitted tones and detecting the multipath time delay spreads represented by received envelopes of at least each tone pair contained within the plurality of transmitted tones to obtain link quality parameters representing the quality of said communication link. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A method of measuring the quality of communication links between a transmitting station and a receiving station comprising:
-
transmitting a plurality of signal tones over a communication link; receiving the plurality of transmitted tones and link noise to obtain a received signal; time domain sampling said received signal to obtain a set of N blocks of digitized samples with each block having M samples; transforming the blocks of M digitized samples from the time domain to the frequency domain; and measuring the transformer signals to obtain link quality parameters representing the quality of said communication link for N blocks of M samples where M and N are positive integers, said measuring step including; indexing the transformed signals according to frequency to obtain a power spectrum of the plurality of signal tones and link noise in sets of sample time, measuring the frequency offset of each of the plurality of tones from the power spectrum, accumulating the power spectrum of subsequent reception of the plurality of tones and link noise to obtain an accumulated spectrum, storing each power spectrum of each set of plurality of tones and link noise as well as the frequency offset, and measuring link quality parameters from the accumulated spectra, each tone power spectrum and the frequency offset, said step of measuring the link quality parameters further including; obtaining an average frequency offset for each tone, obtaining an RMS frequency offset value for each tone, obtaining amplitude correlation coefficients for each of the plurality of transmitted tones from the M blocks of N samples, detecting frequency spreads for each of the plurality of transmitted tones from the N blocks of M samples, detecting received envelopes of each tone of the plurality of transmitted tones, detecting multipath time delay spreads as indicated by the received envelopes of each tone pair contained within the plurality of transmitted tones, detecting multipath time delay spread as indicated by the received envelopes of each of the tone triplets contained within the plurality of transmitted tones, detecting the second and third harmonics for each of the plurality of transmitted tones, and measuring intermodulation products due to pairs of members of the plurality of transmitted tones.
-
-
21. A communications system for measuring the quality of communication links and selecting a communication channel based on measured quality comprising:
-
means for transmitting information over a selected communication link; means for generating a plurality of signal tones and coupling those tones for transmission by said means for transmitting over said selected communication link; means for receiving said plurality of transmitted tones and any noise on said selected communication link to obtain a received signal; means for time domain sampling said received signal to obtain a set of N blocks of digitized samples with each block having M samples, where M and N are integers; Fast Fourier Transform means for transforming the N blocks of M digitized samples from the time domain to the frequency domain; means responsive to the N blocks of M samples for detecting the frequency spreads for each of the plurality of transmitted tones and for detecting multipath time delay spreads represented by received envelopes of at least tone pairs contained within the plurality of transmitted tones to obtain link quality parameters representing the quality of said communication link; means for selectively changing the communication link over which said signal tones are transmitted to determine the link quality parameters of multiple communication links; and means responsive to a predetermined link quality represented by said parameters detected on each of said selected communication links for selecting a communication link having said predetermined link quality as a communication channel.
-
Specification