System and method for reuse of communications spectrum for fixed and mobile applications with efficient method to mitigate interference

Abstract

A communications system network that enables secondary use of spectrum on a non-interference basis is disclosed. Each secondary transceiver measures the background spectrum. The system uses a modulation method to measure the background signals that eliminates self-generated interference and also identifies the secondary signal to all primary users via on/off amplitude modulation, allowing easy resolution of interference claims. The system uses high-processing gain probe waveforms that enable propagation measurements to be made with minimal interference to the primary users. The system measures background signals and identifies the types of nearby receivers and modifies the local frequency assignments to minimize interference caused by a secondary system due to non-linear mixing interference and interference caused by out-of-band transmitted signals (phase noise, harmonics, and spurs). The system infers a secondary node's elevation and mobility (thus, its probability to cause interference) by analysis of the amplitude of background signals. Elevated or mobile nodes are given more conservative frequency assignments that stationary nodes.

What is claimed is:  
     
       1. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller sharing a radio frequency channel with existing primary users with minimal interference to the primary users comprising the steps of:
 each secondary transceiver and secondary base station measuring the primary signal level in the channel,   each secondary transceiver communicating the signal level to the central controller, and   the central controller determining which channels each node may potentially use by comparing the primary signal level to a threshold value,   wherein a portion of the secondary transceivers and secondary base stations in a region distant from where the channel is being used sequentially transmit a short duration probe signal with a certain power level (P_probe),   the secondary transceivers and secondary base stations within a primary region where the channel is being used measure the probe signal amplitude value (P_received) and send these values to the central controller, and   the central controller determines the maximum power level for each secondary transceivers and secondary base stations in the distant region by the formula: P_transmission (dBm)=P_probe (dBm)−P_received (dBm)+constant, with the value of the constant depending on the maximum interference level allowed in the primary region plus a safety margin, and   the above steps are repeated at regular intervals.   
     
     
       2. The method according to  claim 1 , further comprising the step of:
 using high processing gain probe waveforms such as, but not limited to, direct sequence waveforms, single or multiple continuous wave (CW) tones.   
     
     
       3. The method of  claim 2 , wherein the high processing gain probe waveform is either multiple CW waveforms or combinations of narrowband waveforms, each with energy in a frequency zone within the NTSC six MHz channel width and minimal energy at other frequencies in the channel, the frequency zone being in the lower and upper guard bands, between the video carrier and the color-subcarrier, or between the color-subcarrier and the sound carrier. 
     
     
       4. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller sharing a radio frequency channel with existing primary users with minimal interference to the primary users comprising the steps of:
 each secondary transceiver and secondary base station measuring the primary signal level in the channel,   each secondary transceiver communicating the signal level to the central controller,   the central controller determining which channels each node may potentially use by comparing the primary signal level to a threshold value,   wherein a modulation scheme where each secondary transceiver and secondary base station transmits and receives data for a certain time period, then simultaneously halts transmissions, making measurements of the background signals for a time period, and then either transmitting or receiving probe signals.   
     
     
       5. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller sharing a radio frequency channel with existing primary users with minimal interference to the primary users comprising the steps of:
 each secondary transceiver and secondary base station measuring the primary signal level in the channel,   each secondary transceiver communicating the signal level to the central controller,   the central controller determining which channels each node may potentially use by comparing the primary signal level to a threshold value,   wherein proximate primary receivers are identified to each secondary transceivers and secondary base stations by having each secondary transceiver and secondary base station measure the strength of all strong signals within a certain range of the spectrum, and   those signals with a power level above a threshold value declare that these are proximate nodes, and   determine the proximate radio's receive frequency using well-known standards information, and   restricting the secondary transceiver's or secondary base station's transmit frequency list from harmonically related values, adjacent channel values, or image related values compared to the primary signal.   
     
     
       6. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller sharing a radio frequency channel with existing primary users with minimal interference to the primary users comprising the steps of:
 each secondary transceiver and secondary base station measuring the primary signal level in the channel,   each secondary transceiver communicating the signal level to the central controller, and   the central controller determining which channels each node may potentially use by comparing the primary signal level to a threshold value,   wherein proximate primary receive only radios are identified to each secondary transceivers and secondary base stations by having each secondary transceivers and secondary base stations measure the strength of the primary receiver's local oscillator leakage, and   and those signals above a threshold value declare that these is a proximate receive-only node, and   determine the proximate receiver's frequency using well-known standards information, and   restricting the secondary transceivers or secondary base station's transmit frequency list from harmonically related values, adjacent channel values, or image related values compared to the primary signal.   
     
     
       7. A method for a network of secondary communication devices to share the analog TV spectrum consisting of the steps of,
 each secondary transceivers and secondary base stations measuring the strength of the background TV signal strength, and   if the primary TV signal strength is greater than a certain level above the noise level but less than another higher level, then   the secondary system will use a waveform with energy between 1.5 MHz above the channel start frequency and 4.5 MHz above the channel start frequency to avoid interference caused by the analog video and sound carriers.   
     
     
       8. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller to identify which device is causing Interference to a primary user comprising of the steps of, 
       a method to unambiguously marking the secondary system's signal when received by the primary receiver such as, but not limited to, amplitude modulating the secondary signal, and
 provide a method for the affected primary user to communicate with the secondary system's central controller and communicate the primary receiver's location and the channel frequency, and 
 the central controller determine the closest secondary transceiver or secondary base station to the primary node and the likely frequencies being transmitted that might cause the interference, and 
 command the secondary transceiver or secondary base station to transmit data, and 
 sequentially reducing the power of the closet secondary transceiver or base station until the primary user reports that the problem is resolved, and 
 if the interference to the primary receiver continues, determine the next closest secondary transceiver or secondary base station to the primary node and repeating the previous step until the secondary node causing the Interference is located. 
 
     
     
       9. A method for a network of secondary communication devices consisting of transceivers, base stations and a central controller sharing a radio frequency channel with existing primary users with minimal interference to the primary users comprising the steps of:
 each secondary transceiver and secondary base station measuring the primary signal level in the channel,   each secondary transceiver communicating the signal level to the central controller, and   the central controller determining which channels each node may potentially use by comparing the primary signal level to a threshold value,   wherein each secondary transceivers arid secondary base stations measures the strength of multiple signals from several other stationary transmitters and by analysis of these signal level amplitudes and if there is significant co-channel interference determines if the secondary transceiver or secondary base station is moving or elevated, and   
       if the secondary transceiver or secondary base station is moving or elevated, then the node will use more conservative spectrum assignments that include one or more of the following: reducing the node's maximum transmitted power, Increasing the repetition rate of the node's probing and primary signal level measurements, and use of another channel. 
     
     
       10. A method for communicating among a plurality of transceivers, the method comprising:
 transmitting data from at least one of the plurality of transceivers to at least another of the plurality of transceivers during a first time period;   each of the plurality of transceivers entering a receive-only mode to receive signals during a second time period; and   synchronizing the second time period among all of the plurality of transceivers.   
     
     
       11. The method of claim 10, wherein the step of each of the plurality of transceivers entering the receive-only mode during the second time period comprises:
 each of the plurality of transceivers entering a receive-only mode on each of a plurality of channels, wherein the period during which each of the transceivers is in a receive-only mode for each of the plurality of channels is offset in time from the period during which each of the transceivers is in a receive-only mode for each of the other plurality of channels.   
     
     
       12. The method of claim 10, further comprising the step of, during the second time period, making measurements of background signals in a communication channel used by the plurality of transceivers. 
     
     
       13. The method of claim 10, further comprising the step of, during the second time period, making measurements of background signals in a communication channel not used by the plurality of transceivers. 
     
     
       14. The method of claim 10, further comprising the step of detecting a signal that indicates a proximate transmitter or a proximate transceiver. 
     
     
       15. The method of claim 14, further comprising the step of restricting transmission by at least one of the plurality of transceivers on a channel associated with the proximate transmitter. 
     
     
       16. The method of claim 15, wherein the step of restricting transmission by at least one of the plurality of transceivers comprises reducing the at least one transceiver's maximum transmitted power. 
     
     
       17. The method of claim 14, wherein the proximate transmitter is a primary transmitter and each of the plurality of transceivers is a secondary node. 
     
     
       18. The method of claim 14, wherein the proximate transmitter signal is identified by a power level above a threshold level. 
     
     
       19. The method of claim 14, further comprising restricting transmission by at least one of the plurality of transceivers on a channel associated with the proximate transmitter. 
     
     
       20. The method of claim 10, further comprising the step of each of the plurality of transceivers transmitting, receiving, or both transmitting and receiving data during the first time period. 
     
     
       21. The method of claim 10, wherein the step of synchronizing the second time period comprises simultaneously halting transmissions among the plurality of transceivers during the second time period. 
     
     
       22. The method of claim 10, further comprising the step of making measurements of background signals during the second time period. 
     
     
       23. The method of claim 10, further comprising the step of detecting a proximate receive-only node. 
     
     
       24. The method of claim 23, wherein the proximate receive-only node is a primary node and each of the plurality of transceivers is a secondary node. 
     
     
       25. The method of claim 23, wherein detecting the proximate receive-only node comprises detecting a proximate receive-only node's oscillator leakage. 
     
     
       26. A method of accessing channels in a wireless communication system, the method comprising:
 configuring a transceiver to transmit and/or receive data during an operation interval;   configuring the transceiver for a measurement interval, the measurement interval being synchronized with a plurality of additional transceivers and during which the transceiver and each of the plurality of additional transceivers halts transmitting; and   configuring the transceiver to transmit or receive a non-data probe waveform during a probe interval.   
     
     
       27. The method of claim 26, wherein the operation interval spans approximately 89-90 percent of operating time of the transceiver. 
     
     
       28. The method of claim 26, wherein the measurement interval spans not more than approximately 1 percent of operating time of the transceiver. 
     
     
       29. The method of claim 26, wherein the probe interval spans approximately 10 percent of operating time of the transceiver. 
     
     
       30. A system comprising a plurality of transceivers, each transceiver configured to transmit data to at least one other transceiver of the plurality of transceivers during a first time period;
 enter a receive-only mode to receive signals during a second time period; and   synchronize the second time period with each of the other of the plurality of transceivers.   
     
     
       31. The system of claim 30, wherein each of the plurality of transceivers is configured to enter a receive-only mode on each of a plurality of channels, wherein the period during which each of the transceivers is in a receive-only mode for each of the plurality of channels is offset in time from the period during which each of the transceivers is in a receive-only mode for each of the other plurality of channels. 
     
     
       32. The system of claim 30, wherein at least one of the plurality of transceivers is configured to make measurements, during the second time period, of background signals in a communication channel used by the plurality of transceivers. 
     
     
       33. The system of claim 30, wherein at least one of the plurality transceivers is configured to make measurements, during the second time period, of background signals in a communication channel not used by the plurality of transceivers. 
     
     
       34. The system of claim 30, at least one of the plurality of transceivers configured to detect a signal that indicates a proximate transmitter or a proximate transceiver. 
     
     
       35. The system of claim 34, wherein at least one of the plurality of transceivers is restricted from transmitting on a channel associated with the proximate transmitter. 
     
     
       36. The system of claim 35, wherein the restricted one of the plurality of transceivers has a reduced maximum transmitted power. 
     
     
       37. The system of claim 35, wherein the proximate transmitter is a primary transmitter and each of the plurality of transceivers is a secondary node. 
     
     
       38. The system of claim 35, wherein the proximate transmitter signal is identified by a power level above a threshold level. 
     
     
       39. The system of claim 35, wherein at least one of the plurality of transceivers is restricted from transmitting on a channel associated with the proximate transmitter. 
     
     
       40. The system of claim 30, wherein each of the plurality of transceivers is configured to transmit, to receive, or both transmit and receive data during the first time period. 
     
     
       41. The system of claim 30, wherein the plurality of transceivers are configured to synchronize the second time period by simultaneously halting transmissions during the second time period. 
     
     
       42. The system of claim 30, wherein at least one of the plurality of transceivers is configured to make measurements of background signals during the second time period. 
     
     
       43. The system of claim 30, wherein at least one of the plurality of transceivers is configured to detect a proximate receive-only node. 
     
     
       44. The system of claim 43, wherein the proximate receive-only node is a primary node and each of the plurality of transceivers is a secondary node. 
     
     
       45. The system of claim 43, wherein at least one of the plurality of transceivers is configured to detect the proximate receive-only node by detecting the proximate receive-only node's oscillator leakage. 
     
     
       46. A transceiver device comprising:
 a communication module; and   a processor in communication with the communication module and configured to control operation of the communication module;   the device configured to:
 transmit data to at least one transceiver of a plurality of transceivers during a first time period; 
 enter a receive-only mode to receive signals during a second time period; and 
 synchronize the second time period with each of the other of the plurality of transceivers. 
   
     
     
       47. The device of claim 54, wherein the device is restricted from transmitting on a channel associated with the proximate transmitter. 
     
     
       48. The device of claim 55, wherein the device has a reduced maximum transmitted power. 
     
     
       49. The device of claim 55, wherein the proximate transmitter is a primary transmitter and each of the plurality of transceivers is a secondary node. 
     
     
       50. The device of claim 55, wherein the proximate transmitter signal is identified by a power level above a threshold level. 
     
     
       51. The device of claim 55, wherein the device is restricted from transmitting on a channel associated with the proximate transmitter. 
     
     
       52. The device of claim 47, wherein the device has a reduced maximum transmitted power. 
     
     
       53. The device of claim 47, wherein the proximate transmitter is a primary transmitter and each of the plurality of transceivers is a secondary node. 
     
     
       54. The device of claim 47, wherein the proximate transmitter signal is identified by a power level about a threshold level. 
     
     
       55. The device of claim 54, wherein the device is restricted from transmitting on a channel associated with the proximate transmitter. 
     
     
       56. The device of claim 46, wherein the device is configured to transmit, to receive, or both transmit and receive data during the first time period. 
     
     
       57. The device of claim 46, further configured to synchronize the second time period by simultaneously halting transmissions during the second time period. 
     
     
       58. The device of claim 46, further configured to make measurements of background signals during the second time period. 
     
     
       59. The device of claim 46, further configured to detect a proximate receive-only node. 
     
     
       60. The device of claim 59, wherein the proximate receive-only node is a primary node and each of the plurality of transceivers is a secondary node. 
     
     
       61. The device of claim 59, further configured to detect the proximate receive-only node by detecting the proximate receive-only node's oscillator leakage. 
     
     
       62. The device of claim 59, wherein the communication module comprises a programmable modem, a tuner, or a combination thereof. 
     
     
       63. A method of accessing channels in a wireless communication system, the method comprising:
 configuring a transceiver to transmit and/or receive data during an operation interval;   configuring the transceiver for a measurement interval, the measurement interval being synchronized with a plurality of additional transceivers and during which the transceiver and each of the plurality of additional transceivers halts transmitting; and   configuring the transceiver to transmit or receive a non-data probe waveform during a probe interval.   
     
     
       64. The method of claim 63, wherein the operation interval spans approximately 89-90 percent of operating time of the transceiver. 
     
     
       65. The method of claim 63, wherein the measurement interval spans not more than approximately 1 percent of operating time of the transceiver. 
     
     
       66. The method of claim 63, wherein the probe interval spans approximately 10 percent of operating time of the transceiver. 
     
     
       67. A transceiver device comprising;
 a communication module; and   a processor in communication with the communication module;   the processor configured to perform a method comprising:   configuring the communication module to transmit and/or receive data during an operation interval;
 configuring the transceiver for a measurement interval, the measurement interval being synchronized with a plurality of additional transceivers and during which the transceiver and each of the plurality of additional transceivers halts transmitting; and 
 configuring the transceiver to transmit or receive a non-data probe waveform during a probe interval. 
   
     
     
       68. The device of claim 67, wherein the operation interval spans approximately 89-90 percent of operating time of the device. 
     
     
       69. The device of claim 67, wherein the measurement interval spans not more than approximately 1 percent of operating time of the device. 
     
     
       70. The device of claim 67, wherein the probe interval spans approximately 10 percent of operating time of the device. 
     
     
       71. The device of claim 67, wherein the communication module comprises a programmable modem, a tuner, or a combination thereof. 
     
     
       72. A system comprising a plurality of transceivers, at least one transceiver comprising a processor configured to perform a method comprising:
 configuring the at least one transceiver to transmit and/or receive data during an operation interval;   configuring the at least one transceiver for a measurement interval, the measurement interval being synchronized with a plurality of additional transceivers and during which the transceiver and each of the plurality of additional transceivers halts transmitting; and   configuring the at least one transceiver to transmit or receive a non-data probe waveform during a probe interval.   
     
     
       73. The system of claim 72, wherein the operation interval spans approximately 89-90 percent of operating time of the transceiver. 
     
     
       74. The system of claim 72, wherein the measurement interval spans not more than approximately 1 percent of operating time of the transceiver. 
     
     
       75. The system of claim 72, wherein the probe interval spans approximately 10 percent of operating time of the transceiver.