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

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 An improved transmit power control technique which is not affected by modulation type, is also described.

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  coupling 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 a maximum power level;  
 measuring, for a customer site not operating at the maximum power level, 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  coupled to the outdoor unit; and  
 an indoor unit connected  coupled 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 a maximum power level,  
 instruct the outdoor unit to measure, for a customer site not operating at the maximum power level, 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  coupling 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 a maximum power level, power of the received signal at the outdoor unit;  
 comparing the power of the received signal to a predetermined  nominal level; and  
 increasing a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined  nominal level or decreasing the receive path gain of the indoor unit if the power of the received signal is less than the predetermined  nominal 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 the maximum power level. 
     
     
       19. The method defined in  claim 18 , wherein determining if the customer site is operating at the maximum power level 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  coupling 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  nominal level;  
 requesting the customer site to decrease the transmit power if the power of the received signal is greater than the predetermined  nominal level or requesting the customer site to increase the transmit power if the power of the received signal is less than the predetermined  nominal level; and  
 providing a maximum power status  level to the base station to decide 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  coupled to the outdoor unit; and  
 an indoor unit connected  coupled 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 a maximum power level, power of the received signal at the outdoor unit,  
 compare the power of the received signal to a predetermined  nominal level, and  
 increase a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined  nominal level or decrease the receive path gain of the indoor unit if the power of the received signal is less than the predetermined  nominal 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  coupled 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  coupled 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  nominal transmit output level; and  
 a comparator configured to compare the predetermined  nominal 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  coupled 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  nominal transmit output level; and  
 a comparator configured to compare the predetermined  nominal 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  nominal transmit output level;  
 comparing the predetermined  nominal 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. 
     
     
       41. A wireless communications system, comprising:
   a communication hub configured to provide one or more communication services;        a base station coupled to said communication hub, wherein the base station includes:      an outdoor unit configured to wirelessly receive signals from one or more transceivers;        an indoor unit configured to receive the signals from the outdoor unit via one or more cables, wherein the indoor unit is configured to:        measure an average power received at the outdoor unit; and        increase a gain of the indoor unit in response to a determination that the average power exceeds a nominal power level, or decrease the gain in response to a determination that the average power does not exceed the nominal level.       
     
     
       42. The system of  claim 41 , further comprising a video server configured to provide a video service to at least one of the transceivers via the communication hub. 
     
     
       43. The system of  claim 41 , further comprising:
   one or more customer premises equipment  ( CPE )  coupled to corresponding ones of the one or more transceivers; and        a residential gateway coupled to one of the CPE.     
     
     
       44. The system of  claim 41 , wherein the communication hub further comprises at least one ATM switch configured to provide at least one ATM service. 
     
     
       45. The system of  claim 44 , wherein the at least one ATM service is a video service, a voice service, or a data service. 
     
     
       46. The system of  claim 41 , wherein the base station further comprises an antenna. 
     
     
       47. The system of  claim 41 , wherein the indoor unit is further configured to identify individual ones of the one or more transceivers that are not operating at a maximum power level. 
     
     
       48. A method, comprising:
   measuring, by a base station, an average power received at an outdoor unit of the base station; and        increasing, by the base station, a gain of an indoor unit of the base station in response to determining that the average power exceeds a nominal power level, or decreasing the gain of the indoor unit in response to determining that the average power does not exceed the nominal level.     
     
     
       49. The method of  claim 48 , further comprising initializing the gain to a predetermined value. 
     
     
       50. The method of  claim 55 , wherein said identifying one or more transceivers that are not operating at a maximum power level comprises performing an automatic level control process. 
     
     
       51. The method of  claim 48 , further comprising adjusting the gain using a variable voltage attenuator. 
     
     
       52. The method of  claim 48 , further comprising adjusting the gain using a delta step value selected from a range of  0 . 1  dB to  0 . 4  dB. 
     
     
       53. The method of  claim 48 , wherein said increasing a gain substantially compensates for losses in a cable that couples the indoor unit to the outdoor unit. 
     
     
       54. The method of  claim 48 , wherein said increasing or said decreasing comprises compensating for an un- calibrated gain condition of the base station.   
     
     
       55. The method of  claim 48 , further comprising identifying, by the base station, one or more customer sites of a wireless communication system that are not operating at a maximum power level. 
     
     
       56. A method, comprising:
   wirelessly receiving, by a base station, a signal from a transceiver;        measuring, by an indoor unit of the base station, a power level of the signal;        comparing the power level to a nominal power level;        transmitting to the transceiver a request for a decrease in the power level upon a determination that the power level is greater than the nominal level, or transmitting to the transceiver a request for an increase in the power level upon a determination that the power level is less than the nominal level.     
     
     
       57. The method of  claim 56 , wherein said transmitting a request for an increase in power level, or said transmitting a request for a decrease in power level, occurs upon an additional determination that the power level is less than a maximum power level. 
     
     
       58. The method of  claim 56 , further comprising repeating said measuring, said comparing, and said requesting upon receiving an acknowledgement of the request from the transceiver.