System and method of automatically calibrating the gain for a distributed wireless communication system

• US 6,704,579 B2
• Filed: 02/15/2001
• Issued: 03/09/2004
• Est. Priority Date: 02/15/2001
• Status: Expired

• Current Assignee: Mind Fusion, LLC (Ascend Innovation Management, LLC)
• Original Assignee: Ensemble Communications
• Inventors: Gilbert, Sheldon L., Woodhead, David, Gazelle, David, Spinar, Brian
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): Trinh, Tan
• Application Number:
  US09/789,940
• Publication Number:
  US 20020119797A1
• Time in Patent Office: 1,118 Days
• Field of Search: 455/3.01, 455/426.2, 455/69, 455/522, 455/561, 370/335, 370/342
• US Class Current: 455/522
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/362 Aspects of the step size
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

A system and method providing a wireless broadband connection between base stations and customer sites. The system includes indoor units, within the base stations and customer sites, that communicate across cables to outdoor units. The indoor units link to routers, switches and other devices and services. The outdoor units transmit and receive wireless data and send it to the indoor units. The indoor units control the functioning of the outdoor units by transmitting digital messages along the interface cables. The outdoor units report various detector values to the indoor units, which allows the indoor units to tune and adjust several functions within the outdoor units. Several embodiments for automatically calibrating the receive path gain in the base stations to compensate for the base station cable between the indoor unit and outdoor unit are described. In addition, an improved transmit power control technique which is not affected by modulation type, is also described.

Claims

1. A method of automatically calibrating the gain of an indoor unit of a base station having an outdoor unit and a broadband cable connecting the indoor unit and outdoor unit in a wireless communication system having customer sites, the method comprising:

determining which customer sites are not operating at maximum power;

measuring, for a customer site not operating at maximum power, average received power at the outdoor unit;

comparing the average received power to a nominal level; and

increasing the gain of the indoor unit if the average received power is greater than the nominal level or decreasing the gain of the indoor unit if the average received power is less than the nominal level.

2. The method defined in claim 1, additionally comprising initializing the indoor unit gain to a predetermined maximum value.

3. The method defined in claim 1, wherein the indoor unit gain is adjusted by a variable voltage attenuator.

4. The method defined in claim 3, wherein the indoor unit gain is adjusted using a delta step value selected from a range of 0.1 dB to 0.4 dB.

5. The method defined in claim 1, wherein determining includes performing an automatic level control process.

6. The method defined in claim 1, wherein adjusting the indoor unit gain compensates for losses in the cable.

7. The method defined in claim 1, wherein the acts of determining, measuring, comparing and increasing or decreasing preclude the need to calibrate the gain before installation of the base station.

8. A base station, configured to automatically calibrate a receive path gain, for use in a wireless communication system having customer sites, the base station comprising:

an outdoor unit configured to receive signals from the customer sites, wherein the signals include power readings from the customer sites;

a broadband cable connected to the outdoor unit; and

an indoor unit connected to the broadband cable and configured to receive message data from the outdoor unit through the broadband cable, wherein the indoor unit includes a processor configured to;

determine which customer sites are not operating at maximum power,

instruct the outdoor unit to measure, for a customer site not operating at maximum power, average received power at the outdoor unit,

compare the average received power to a nominal level, and

increase the gain of the indoor unit if the average received power is greater than the nominal level or decrease the gain of the indoor unit if the average received power is less than the nominal level.

9. The base station defined in claim 8, wherein the indoor unit additionally comprises a variable voltage attenuator configured to adjust the gain of the indoor unit.

10. The base station defined in claim 8, wherein the processor initializes the indoor unit gain to a predetermined maximum value.

11. The base station defined in claim 8, wherein the message data from the outdoor unit includes data indicative of average received power at the outdoor unit.

12. A method of automatically calibrating a receive path gain of a base station having an indoor unit, an outdoor unit and a broadband cable connecting the indoor unit and the outdoor unit in a wireless communication system having one or more customer sites, the method comprising:

wirelessly receiving signals from one or more customer sites;

measuring, for a customer site not operating at maximum power, power of the received signal at the outdoor unit;

comparing the power of the received signal to a predetermined level; and

increasing a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined level or decreasing the receive path gain of the indoor unit if the power of the received signal is less than the predetermined level.

13. The method defined in claim 12, wherein one of the customer sites is initially transmitting the signal.

14. The method defined in claim 12, additionally comprising:

waiting for another transmitted signal from the customer site or another customer site; and

repeating the measuring, comparing, and increasing or decreasing.

15. The method defined in claim 12, additionally comprising initializing the receive path gain of the indoor unit to a predetermined maximum value.

16. The method defined in claim 15, wherein the predetermined maximum value corresponds to a longest possible cable length.

17. The method defined in claim 12, wherein the receive path gain of the indoor unit is adjusted by a variable voltage attenuator.

18. The method defined in claim 12, additionally comprising determining if a customer site is operating at maximum power.

19. The method defined in claim 18, wherein determining if the customer site is operating at maximum power includes performing an automatic level control process.

20. The method defined in claim 12, wherein adjusting the receive path gain of the indoor unit or the outdoor unit compensates for losses in the cable.

21. A method of automatically controlling the transmit power of a customer site by a base station having an indoor unit, an outdoor unit and a broadband cable connecting the indoor unit and the outdoor unit in a wireless communication system so as to automatically compensate for losses due to the cable, the method comprising:

wirelessly receiving a signal from a customer site that has started to transmit the signal;

measuring power of the received signal at the indoor unit;

comparing the power of the received signal to a predetermined level;

requesting the customer site to decrease the transmit power if the power of the received signal is greater than the predetermined level or requesting the customer site to increase the transmit power if the power of the received signal is less than the predetermined level; and

providing a maximum power status to the base station if the customer site is operating at maximum power so as to control automatic compensation for losses due to the base station cable.

22. The method defined in claim 21, additionally comprising waiting for the customer site to acknowledge the request to either decrease the transmit power or increase the transmit power.

23. A base station configured to automatically calibrate a receive path gain in a wireless communication system having customer sites, the base station comprising:

an outdoor unit wirelessly receiving signals from the customer sites, wherein the signals include power levels of one or more of the customer sites;

a broadband cable connected to the outdoor unit; and

an indoor unit connected to the broadband cable and receiving message data from the outdoor unit through the broadband cable, wherein the indoor unit includes a processor configured to;

measure, for a customer site not operating at maximum power, power of the received signal at the outdoor unit,

compare the power of the received signal to a predetermined level, and

increase a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined level or decrease the receive path gain of the indoor unit if the power of the received signal is less than the predetermined level.

24. The base station defined in claim 23, wherein one of the customer sites has started to transmit signals.

25. The base station defined in claim 23, wherein the processor is additionally configured to:

wait for another signal from the customer site or another customer site, and

repeat the measure, compare, and increase or decrease.

26. The base station defined in claim 23, wherein the indoor unit additionally comprises a variable voltage attenuator configured to adjust the receive path gain of the indoor unit.

27. The base station defined in claim 23, wherein the processor initializes the indoor unit receive path gain to a predetermined maximum value.

28. The base station defined in claim 23, wherein the message data from the outdoor unit includes data indicative of the power of the received signal at the outdoor unit.

29. A base station for maintaining transmit peak power at a constant level regardless of modulation type for use in a wireless communication system, the base station comprising:

an indoor unit having a modem configured to provide an output and to use multiple modulation types within a single time division duplexing frame;

an outdoor unit connected to the indoor unit and having a transmit system configured to upconvert the output of the modem, the outdoor unit comprising;

a wideband detector configured to monitor a transmit system output signal;

a sample and hold circuit connected to the wideband detector, the sample and hold circuit having a gate input;

a delay circuit receiving a transmit/receive control signal and providing an output to the gate input of the sample and hold circuit;

a transmit level adjust circuit configured to provide a predetermined transmit output level; and

a comparator configured to compare the predetermined transmit output level with the output of the sample and hold circuit so as to generate an error signal to maintain transmit peak power at a constant level.

30. The subsystem defined in claim 29, additionally comprising;

a loop integrator receiving the error signal; and

a voltage controlled attenuator receiving the output of the loop integrator and maintaining transmit peak power at the constant level, the attenuator being in the transmit signal path.

31. The subsystem defined in claim 29, wherein the bandwidth of the detector is selected from the range of 2 MHz to 10 MHz.

32. The subsystem defined in claim 29, wherein the modulation type is QPSK, QAM16 or QAM64.

33. The subsystem defined in claim 29, wherein the delay circuit provides approximately two microseconds delay.

34. The subsystem defined in claim 29, wherein the sample and hold circuit measures the amplitude of the transmit output signal during a QPSK preamble so as to maintain the transmit peak power at a constant level.

35. A subsystem for maintaining transmit peak power at a constant level regardless of modulation type in an outdoor unit of a wireless communication system, the subsystem comprising:

a wideband detector configured to monitor a transmit output signal;

a sample and hold circuit connected to the wideband detector, the sample and hold circuit having a gate input;

a delay circuit providing an output, indicative of a time in the transmit output signal when a known modulation type occurs, to the gate input of the sample and hold circuit;

a transmit level adjust circuit configured to provide a predetermined transmit output level; and

a comparator configured to compare the predetermined transmit output level with the output of the sample and hold circuit so as to generate an error signal used to maintain transmit peak power at a constant level.

36. The subsystem defined in claim 35, additionally comprising;

a loop integrator receiving the error signal; and

a voltage controlled attenuator receiving the output of the loop integrator and maintaining transmit peak power at the constant level, the attenuator being in the transmit signal path.

37. A method of maintaining transmit peak power at a constant level regardless of modulation type in an outdoor unit of a time division duplexing wireless communication system, the method comprising:

providing a control signal at a predetermined time delay after a transition from a receive mode to a transmit mode;

measuring the amplitude of a transmit output signal based on the delayed control signal;

providing a predetermined transmit output level;

comparing the predetermined transmit output level with the amplitude of the transmit output signal; and

generating a signal representative of the comparing so as to maintain transmit peak power at a constant level.

38. The method defined in claim 37, additionally comprising controlling an attenuator by the signal representative of the comparing to maintain transmit peak power at the constant level, the attenuator being in the transmit signal path.

39. The method defined in claim 37, wherein the delayed control signal enables measuring the amplitude of the transmit output signal during a QPSK preamble of a data burst.

40. The method defined in claim 37, wherein the predetermined time delay is approximately two microseconds.