Vector network analyzer applique for adaptive communications in wireless networks

• US 7,155,171 B2
• Filed: 10/25/2002
• Issued: 12/26/2006
• Est. Priority Date: 12/12/2001
• Status: Expired due to Fees

• Current Assignee: Saraband Wireless Incorporated
• Original Assignee: Saraband Wireless Incorporated
• Inventors: Ebert, Paul Michael, Arnstein, Donald Stuart
• Primary Examiner(s): To, Doris H.
• Assistant Examiner(s): Yun, Eugene
• Application Number:
  US10/280,595
• Publication Number:
  US 20030153273A1
• Time in Patent Office: 1,523 Days
• Field of Search: 455/67.14, 455/67.16, 455/67.11, 455/71, 455/42, 455/23
• 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 system comprising:

a test signal injector which interlaces test signals with communications signals, wherein one or more of the test signals is a linear FM sweep;

a transmitter which transmits said interlaced test signals over a wireless communications path;

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

a signal processing circuit which uses one or more of said measurements to correct for effects of the propagation path on the communication signals;

wherein the test signal receiver comprises;

an adjustable signal generator which generates a facsimile of said test signals;

a down converter which uses said facsimile signal to heterodyne said received test signals to obtain a down converted signal; and

a logical processor capable of analyzing said down converted signal and providing a control signal to said adjustable facsimile signal generator to adjust one or more parameters of said adjustable facsimile signal generator, determining information regarding a number of revolutions about an origin point in a two-dimensional plane representing in-phase and quadrature samples of the down converted signal, and determine information regarding the time base offset between the test signal and the facsimile signal using the determined information regarding the number of revolutions.

2. The system of claim 1 wherein the test signal receiver comprises:

an adjustable signal generator which generates a facsimile of said test signals;

a downconverter which uses said facsimile signal to heterodyne said received test signals to obtain a down converted signal; and

a logical processor capable of analyzing said down converted signal and providing a control signal to said adjustable facsimile signal generator to adjust one or more parameters of said facsimile signal generator.

3. The system of claim 1, wherein the test signal injector is capable of setting and modifying one or more parameters of the test signals, the one or more parameters including one or more of a time duration of the test signals, a frequency occupancy of the test signals, a time separation between test signals, a rate of injection of the test signals, and a transmit power level of the test signals.

4. The system of claim 1, wherein the logical processor in analyzing said down converted signal is capable of:

determining a time base difference between the transmitted test signal and the facsimile test signal.

5. The system of claim 1, wherein the test signal injector is included in a test signal transmitter side of the system and wherein the test signal receiver is included in a test signal receiver side of the system, and wherein the test signal transmitter side and the test signal receiver side are separated by the communications propagation path;

wherein the signal processing circuit is included in the test signal receiver end and is configured to correct for effects of the propagation path on the received interlaced signals; and

wherein, in correcting for the effects, the signal processing circuit is configured to set a channel equalizer a for a communications data demodulator.

6. The system of claim 1, wherein the test signal injector is included in a test signal transmitter side of the system and wherein the test signal receiver is included in a test signal receiver side of the system, and wherein the test signal transmitter side and the test signal receiver side are separated by the communications propagation path;

wherein the signal processing circuit is included in the transmitter side and is configured to correct for effects of the propagation path on a signal received from the receiver side and transmitted over the communications propagation path; and

wherein, in correcting for the effects, the signal processing circuit is configured to set a channel equalizer for a communications data demodulator.

7. The system of claim 1, wherein the signal processing circuit is further configured to adaptively control queuing and segmentation of both forward-going and backward-going communications based on one or more of said measurements.

8. The system of claim 1, wherein the logical processor is further configured to effect an adjustment of the time base offset of the facsimile signal based on the determined information regarding the time base offset between the test signal and the facsimile signal.

9. The system of claim 1, wherein the logical processor is further configured to determine information regarding a frequency offset between the test signal and the facsimile signal using the determined number, and effect an adjustment in the frequency offset of the facsimile signal based on the determined frequency offset between the test signal and the facsimile signal.

10. The system of claim 1, wherein the logical processor is further configured to determine information regarding a time offset between the test signal and the facsimile signal using the determined number, and effect an adjustment of the start time of the facsimile signal based on the determined time offset between the test signal and the facsimile signal.

11. The system of claim 1, further comprising:

a network interface; and

wherein the communications signal carries information received via the network interface.

12. The system of claim 1, wherein the communications signal carries control information generated by the system.

13. A method comprising:

interlacing test signals with communications signals;

transmitting the interlaced test signals over a wireless communications path from a transmitter to a receiver;

receiving at the receiver said interlaced test signals;

generating a facsimile signal, wherein the facsimile signal is a facsimile of said test signal;

heterodyning said received test signal and said facsimile signal to obtain a down converted signal;

analyzing said down converted signal;

determining information regarding a number of revolutions about an origin point in a two-dimensional plane representing in-phase and quadrature samples of the down converted signal;

determining information regarding a time base offset between the test signal and the facsimile signal based on the determined information regarding the number of revolutions;

adjusting one or more parameters of the facsimile signal based on the analysis of the down converted signal;

determining information regarding characteristics of the propagation path using the received interlaced test signals; and

correcting for effects of the propagation path on the communication signals using the determined information.

14. The method of claim 13, further comprising:

adjusting a time base of the facsimile signal based on the determined information regarding the time base offset between the test signal and the facsimile signal.

15. The method of claim 13, further comprising:

determining information regarding a frequency offset between the test signal and the facsimile signal using the determined number; and

adjusting a frequency offset of the facsimile signal based on the determined frequency offset between the test signal and the facsimile signal.

16. The method of claim 13, further comprising:

determining information regarding a time offset between the test signal and the facsimile signal using the determined number; and

adjusting a the start time of the facsimile signal based on the determined time offset between the test signal and the facsimile signal.

17. The method of claim 13, wherein the communications signal carries information received via a network interface.

18. The method of claim 13, wherein the communications signal carries information regarding the effects of the propagation path.

19. The method of claim 13, wherein correcting for effects of the propagation path comprises setting a channel equalizer.

20. The method of claim 13, further comprising:

adaptively controlling queuing and segmentation of both forward-going and backward-going communications based on one or more of said measurements.

21. A system comprising:

means for interlacing test signals with communications signals;

means for transmitting the interlaced test signals over a wireless communications path from a transmitter to a receiver;

means for receiving at the receiver said interlaced test signals;

means for generating a facsimile signal, wherein the facsimile signal is a facsimile of said test signal;

means for heterodyning said received test signal and said facsimile signal to obtain a down converted signal;

means for analyzing said down converted signal;

means for determining information regarding a number of revolutions about an origin point in a two-dimensional plane representing in-phase and quadrature samples of the down converted signal;

means for determining information regarding a time base offset between the test signal and the facsimile signal based on the determined information regarding the number of revolutions;

means for adjusting one or more parameters of the facsimile signal based on the analysis of the down converted signal;

means for determining information regarding characteristics of the propagation path using the received interlaced test signals; and

means for correcting for effects of the propagation path on the communication signals using the determined information.