Vector network analyzer applique for adaptive communications in wireless networks

• US 20030153273A1
• Filed: 10/25/2002
• Published: 08/14/2003
• Est. Priority Date: 12/12/2001
• Status: Active Grant

• Current Assignee: Saraband Wireless Incorporated
• Original Assignee: Saraband Wireless Incorporated
• Inventors: Ebert, Paul Michael, Arnstein, Donald Stuart
• Granted Patent: US 7,155,171 B2
• Time in Patent Office: Days
• US Class Current: 455/67.14
• CPC Class Codes: H04B 17/15 Performance testing
• CPC Class Codes: H04B 17/20 of receivers
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/244 test sequence generators
• CPC Class Codes: H04L 25/022 of frequency response

Abstract

A test signal generator at a transmitter station and a facsimile generator at a receiver station go through an acquisition and tracking process which aligns the two signals so that a logical processor can compute the frequency transfer function of the entire propagation path for use in an adaptive, concurrently sent communication signal. The frequency transfer function is conveyed back to the transmit end via a control channel permitting an adaptivity function at the transmit end to influence subsequent selection of communication parameters, among which are typically transmitted data rate, selection of modulation, selection of forward error correcting coding, and selection of frequency band for transmission. The same measurement is conveyed to an adaptivity function at the receive end for use in the communications receiver to select demodulator variables such as gain control, and equalization of amplitude and phase, versus frequency. The adaptivity function also permits interspersing of reverse-direction communications over the same frequency bands in a time-share mode between forward-direction and reverse-direction communication with the measurement signals having to be transmitted in only one direction. An alternate embodiment invention of this type is described which is additionally useful for mobile communications channels. Another variation embodiment is described for pure propagation measurements only, absent conveyance of end-user information.

Claims

1. A vector network analyzer which measures amplitude and phase-shift versus frequency of a radio propagation link typical of licensed-band or unlicensed-band wireless communications, said analyzer being used in an applique mode appended to a wireless radio frequency communications link, and comprising:

a test signal injector which interlaces radio frequency testing signals with communications signals,

a test signal receiver which receives said interlaced test signals and forms measurements of the amplitude versus frequency and phase-shift versus frequency characteristics of the propagation path,

a measurements conveyance part which sends extracts of said measurement to operational control points.

2. A vector network analyzer described in claim 1 that has a test signal receiver part consisting of:

an adjustable signal generator which generates a facsimile of said transmitted RF testing signal and which has adjustable parameters;

start time, frequency offset, and time base,

a downconverter at said receiving end which uses said adjustable facsimile signal as the heterodyning signal, a plurality of analog-to-digital converters which samples in-phase and quadrature components of said downconverted signal for analysis in a logical processor, for which a personal computer is one example,

a controller from said logical processor to said adjustable facsimile signal generator which changes the time offset, frequency offset or time base parameters of said facsimile signal generator.

3. An injector of radio frequency test signals along with its associated facsimile generator at said receiving end in claim 1 for which:

the time duration of the injected and facsimile test signals is settable,

the frequency occupancy of the injected and facsimile test signals is settable,

the time separation between one injected test signal and the next injected test signal is settable,

the time separation between one facsimile test signal and the next facsimile test signal is also settable to be either the same or different from said time separation of said injected test signal time separation,

the rate of injection of test signals and rate of generation of facsimile signals are both settable,

the transmit power level of the test signal is settable independent of the transmit power level of the communications,

settability parameters are entered into the test signal generator and facsimile generator either before the start of use, or are changed at some intermediate time during subsequent use.

4. A test signal receiver logical processor of claim 2 which operates on the analog-to-digital sampled in-phase and quadrature heterodyned signal to perform operations of the following type:

estimation operations whose outcome is an estimate of the frequency difference between the transmitted test signal and the facsimile test signal,

estimation operations whose outcome is an estimate of the time shift between the transmitted test signal and the facsimile test signal,

estimation operations whose outcome is an estimate of the time base difference between the transmitted test signal and the facsimile test signal.

6. A measurements conveyance part in claim 1 which sends extracts of the measurement in numerical form produced by said logical processor to an adaptivity function at the receiving end of the link that carries out one or more of the following operations with the numerical data files so obtained:

a recording operation that makes said numerical data available in a data base that relates said recorded numerical files to the parameters that were used by the test signal generator and the facsimile generator up to and including the time when the extracted numerical files were obtained from the logical processor,

a control operation on the communications data demodulator at the test signal receiving end of the link, said operation comprising the setting of a channel equalizer,

a control operation on the communications data demodulator at the receiving end of the link, said operation comprising the setting of gain control,

a data multiplexing operation in which said extracted numerical files are multiplexed with an end-user'"'"'s network interface data for transport across the radio frequency propagation path ultimately to a data demodulator at the transmitting end of the link where said multiplexed data is demultiplexed into a plurality of data streams, one of which contains the extracted numerical files, which is conveyed to a second adaptivity function, this additional adaptivity function being at the transmit end of the link,

a control operation on the data encoder at the receiving end of the link, said encoder taking multiplexed data streams comprising said user'"'"'s network interface data with said extracted numerical files, said control operation typically involving the queuing of data and segmentation of data for subsequent modulation, up-conversion and radio frequency transmission,

a control operation on the data modulator at the receiving end of the link, said modulator function typically consisting of mapping of encoded data into channel waveforms for subsequent up-conversion and radio frequency transmission, said control operation involving but not limited to selection of modulation alphabet, symbol duration, and mapping rules.

7. A measurements conveyance part in claim 1 which has a second adaptivity function at the transmitting end of the link which receives said demultiplexed numerical file information and which carries out one or more of the following distributive operations with the numerical data files so obtained, these all occuring at the transmitting end of the link:

a recording operation that makes the numerical data available in a data base that relates said recorded numerical files to the parameters that were used by the test signal generator and the facsimile generator up to and including the time when the extracted numerical files were obtained from the logical processor,

a control operation on the data demodulator at the transmitting end of the link, said operation comprising the setting of a channel equalizer,

a control operation on the data demodulator at the transmitting end of the link, said operation comprising the setting of gain control,

a data multiplexing operation in which said settability parameters are multiplexed with an end-user'"'"'s network interface data for transport over the radio frequency link ultimately to a data demodulator at the receiving end where said multiplexed data is demultiplexed into a plurality of data streams, one of which contains the settability parameters to be used by the facsimile signal generator,

a control operation on the data encoder at the transmitting end of the link, said encoder taking multiplexed data streams comprising said user'"'"'s network interface data with said settability parameters, said control operation typically involving the queuing of data and segmentation of data for subsequent modulation, up-conversion and radio frequency transmission,

a control operation on the data modulator at the transmitting end of the link, said modulator function typically consisting of mapping of encoded data into channel waveforms for subsequent up-conversion and radio frequency transmission, said control operation involving but not limited to selection of modulation alphabet, symbol duration, and mapping rules.

8. A measurements conveyance part in claim 1 which contains radio frequency devices for accessing a band of frequencies, said devices enabling the time sharing of the band of frequencies between transmissions of said test signals interlaced with communications on the one hand with conveyance of said multiplexed numerical files representing channel measurements with end-user network interface data on the other hand, said accessing devices comprising:

radio frequency toggle switches at both ends of the link which operate in a time synchronized fashion,

wireless radio frequency antennas with appropriate pass-band filters and stop-band filters needed if necessary for purposes of eliminating or reducing interference into and from adjacent bands,

high power amplifiers and low noise amplifiers.

10. A preferred embodiment of the invention of claim 1 in which injected radio frequency test signal and associated facsimile signal are composite collections of upward-going linear FM sweeps and downward-going linear FM sweeps.

24. A vector network analyzer of claim 1 used as an applique to a communications link wherein the propagation characteristics are typical of unlicensed band, licensed band, and additionally mobile communication bands of operation.

25. The vector network analyzer of claim 24 suitable for mobile propagation channels, which also has said settability of the rate of occurrence parameter permitting said vector network analyzer to adjust the speed of interlacing of test signals to enable it to characterize propagation conditions in a mobile channel, such channels generally changing at a more rapid pace than non-mobile channels.

5. Said logical processor making a plurality of adjustments to said facsimile signal generator, which processing steps are divisible into two categories:

an acquisition processing category in which the facsimile signal generator'"'"'s time base settability parameter and start time settability parameter are adjusted,

a tracking processing category in which both start time and frequency offset settability parameters are varied.

9. Interpretive means for adaptively controlling queuing and segmentation of both forward-going and backward-going communications based in part on measurement data in numerical files produced in said logical processor.

11. Said logical processor for said preferred embodiment test signals which performs the following operations:

finding an estimate of said heterodyne signal'"'"'s center frequency,

finding an estimate of said heterodyne signal'"'"'s start time,

finding an estimate of said heterodyne signal'"'"'s center frequency rate of advancement or retardation.

12. A test signal receiver logical processor which operates on the analog-to-digital sampled in-phase and quadrature heterodyned signal when the test signals are chosen to be of the preferred embodiment type, upward-going linear FM sweeps and downward going linear FM sweeps, said particular operations being further illustrated by a preferred embodiment set of processing steps:

counting revolutions of the vector representing samples of said in-phase and quadrature numbers, the revolutions being taken about an origin point in a two-dimensional plane representing in-phase and quadrature samples, said revolution count being an approximation to the frequency offset of the heterodyned signal,

separating revolution counts according to whether they took place during a particular up-going FM sweep or down-going FM sweep,

separating the aforementioned revolution counts according to the sequence in which the files were recorded by said analog-to-digital converter.

13. An alternative embodiment vector network analyzer which finds amplitude and phase-shift versus frequency of a radio propagation link typical of licensed-band or unlicensed-band wireless communications, said analyzer comprising:

a test signal injector which interlaces radio frequency testing signals with control signals,

a test signal receiver which receives said interlaced test signals and forms measurements of the amplitude versus frequency and phase-shift versus frequency characteristics of the propagation path,

a conveyance part which sends control signals and extracts of the measurements in the form of numerical files to operational control points.

14. A vector network analyzer described in claim 13 that has a test signal receiver part consisting of:

an adjustable signal generator which generates a facsimile of said transmitted RF testing signal and which has adjustable parameters;

start time, frequency offset, and time base,

a downconverter at said receiving end which uses said adjustable facsimile signal as the heterodyning signal,

a plurality of analog-to-digital converters which samples in-phase and quadrature components of said downconverted signal for analysis in a logical processor, for which a personal computer is one example,

a controller from said logical processor to said adjustable facsimile signal generator which changes the time offset, frequency offset or time base parameters of said facsimile signal generator.

15. An injector of radio frequency test signals along with its associated facsimile generator at said receiving end in claim 13 for which:

the time duration of the injected and facsimile test signals is settable,

the frequency occupancy of the injected and facsimile test signals is settable,

the time separation between one injected test signal and the next injected test signal is settable,

the time separation between one facsimile test signal and the next facsimile test signal is also settable to be either the same or different from said time separation of said injected test signal time separation,

the rate of injection of test signals and rate of generation of facsimile signals are both settable,

the transmit power of the test signal is settable,

settability parameters are entered into the test signal generator and facsimile generator either before the start of use, or are changed at some intermediate time during subsequent use.

16. A test signal receiver logical processor of claim 14 which operates on the analog-to-digital sampled in-phase and quadrature heterodyned signal to perform operations of the following type:

estimation operations whose outcome is an estimate of the frequency difference between the transmitted test signal and the facsimile test signal,

estimation operations whose outcome is an estimate of the time shift between the transmitted test signal and the facsimile test signal,

estimation operations whose outcome is an estimate of the time base difference between the transmitted test signal and the facsimile test signal.

17. Said logical processor of claim 14 making a plurality of adjustments to said facsimile signal generator, which processing steps are divisible into two categories:

an acquisition processing category in which the facsimile signal generator'"'"'s time base settability parameter and start time settability parameter are adjusted,

a tracking processing category in which both start time and frequency offset settability parameters are varied.

18. A measurements conveyance part in claim 13 which sends extracts of the measurement in numerical form produced by said logical processor of claim 14 to an adaptivity function at the receiving end of the link that carries out one or more of the following operations with the numerical data files so obtained:

a recording operation that makes said numerical data available in a data base that relates said recorded numerical files to the parameters that were used by the test signal generator and the facsimile generator up to and including the time when the extracted numerical files were obtained from the logical processor,

a control operation on the data demodulator at the receiving end of the link, said operation comprising the setting of a channel equalizer,

a control operation on the data demodulator at the receiving end of the link, said operation comprising the setting of gain control,

a data conveyance operation in which said extracted numerical files are conveyed over the radio frequency channel ultimately to a second adaptivity function at the transmitting end of the link,

a control operation on the data encoder at the receiving end of the link involving the queuing of numerical file data of channel measurements, and segmentation of said numerical data for subsequent modulation, up-conversion and radio frequency transmission,

a control operation on the data modulator at the receiving end of the link, said modulator function typically consisting of mapping of encoded data into channel waveforms for subsequent up-conversion and radio frequency transmission, said control operation involving but not limited to selection of modulation alphabet, symbol duration, and mapping rules.

19. A measurements conveyance part in claim 13 which has a second adaptivity function at the transmitting end which receives said numerical file information of channel measurements, which carries out one or more of the following distributive operations with the numerical data files so obtained, these all occuring at the transmitting end of the link:

a recording operation that makes the numerical data available in a data base that relates said recorded numerical files to the parameters that were used by the test signal generator and the facsimile generator up to and including the time when the extracted numerical files were obtained from the logical processor,

a control operation on the demodulator at the transmitting end of the link which receives numerical files of channel measurements, said operation comprising the setting of a channel equalizer,

a control operation on the demodulator at the transmitting end of the link which receives numerical files of channel measurements, said operation comprising the setting of gain control,

an operation in which said settability parameters of claim 15 are queued for transport over the radio frequency link ultimately to a data demodulator at the receiving end where said settability parameters are conveyed to the facsimile signal generator,

a control operation on the data encoder at the transmitting end of the link, said encoder taking data streams comprising settability parameters, said control operation typically involving the queuing of data and segmentation of data for subsequent modulation, up-conversion and radio frequency transmission,

a control operation on the data modulator at the transmitting end of the link, said modulator function typically consisting of mapping of encoded data into channel waveforms for subsequent up-conversion and radio frequency transmission, said control operation involving but not limited to selection of modulation alphabet, symbol duration, and mapping rules.

20. A measurements conveyance part in claim 13 which contains radio frequency devices for accessing a band of frequencies, said devices enabling the time sharing of the band of frequencies between transmissions of said test signals interlaced with settability control signals on the one hand with conveyance of said numerical files representing channel measurements on the other hand, said accessing devices comprising,

radio frequency toggle switches at both ends of the link which operate in a time synchronized fashion,

wireless radio frequency antennas with appropriate pass-band filters and stop-band filters needed if necessary for purposes of eliminating or reducing interference into and from adjacent bands, high power amplifiers and low noise amplifiers.

21. A preferred embodiment of claim 13 in which injected radio frequency test signal and associated facsimile signal are composite collections of upward-going linear FM sweeps and downward-going linear FM sweeps.

22. Said logical processor for said preferred embodiment test signals in claim 21 which performs the following operations:

finding an estimate of said heterodyne signal'"'"'s center frequency,

finding an estimate of said heterodyne signal'"'"'s start time,

finding an estimate of said heterodyne signal'"'"'s center frequency rate of advancement or retardation.

23. A test signal receiver logical processor for the preferred embodiment of claim 21 which operates on the analog-to-digital sampled in-phase and quadrature heterodyned signal when the test signals are chosen to be combinations of upward-going linear FM sweeps and downward going linear FM sweeps, said particular operations being further illustrated by a preferred embodiment set of processing steps:

counting revolutions of the vector representing samples of said in-phase and quadrature numbers, the revolutions being taken about an origin point in a two-dimensional plane representing in-phase and quadrature samples, said revolution count being an approximation to the frequency offset of the heterodyned signal,

separating revolution counts according to whether they took place during a particular up-going FM sweep or down-going FM sweep,

separating the aforementioned revolution counts according to the sequence in which the files were recorded by said analog-to-digital converter.