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Method and system for detecting in-band jammers in a spread spectrum wireless base station
| Details |
Inventors: Hamdy, Walid; Mathe, Lennart; Sutton, Todd;
Assignee: Qualcomm Inc. (San Diego, CA)
Primary Examiner: Le; Thanh Cong
Assistant Examiner:
Attorney, Agent or Firm: Wadsworth; Philip, Yafuso; Byron
A method and apparatus for use in a wireless communication base station which provides real-time, continuous detection of in-band jammers with negligible impact on base station cost. In addition to providing jammer detection, the use of the invention to provide improved hardware and system diagnostic capabilities is presented. The jammer detection apparatus utilizes automatic gain control techniques, digital sampling, and digital signal processing to identify anomalous frequency components in the received power spectral density curve. Also described are the use of complex sampling, the complex fast Fourier transform (FFT), and Hanning windows to improve jammer detection capabilities. A method of estimating the location of in-band jammers is described using the computed received power spectral density curves of multiple base stations. |
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DETAILED DESCRIPTION The present invention encompasses a method and apparatus for providing real-time, constant detection of in-band jammers with negligible impact on base station cost.
Such real-time spectrum analysis is particularly advantageous for use in wideband wireless systems such as CDMA, in which all subscribers use the same transmit frequency band.
In addition to providing jammer detection, the present invention enables added hardware and system diagnostic capabilities.
With the advent of advanced technologies like CDMA, increasing amounts of processing power are being designed into modern wireless base stations.
While older AMPS base stations could be designed with perhaps a single microprocessor and racks of analog equipment, modern CDMA base stations are being designed with thirty or more microprocessors, including powerful processors with clock speeds in excess of 60 MHz.
The present invention capitalizes on the realization that a modern wireless base station may have a surplus of processing power sufficient for performing complicated signal analysis.
The base station is designed so that a digital sample stream used in demodulating subscriber station signals is also made available to an existing processor for digital signal processing.
Possible options for producing the necessary digital samples include using just the real-input-data FFT using only data in the I or in the Q branch and performing a complex-input-data FFT using both data in the I and Q branches.
A real-input-data FFT has the benefit that it requires less data and processing per FFT, since if having real data, one can perform "two FFT's almost for the cost of one" with some tricks.
The other option has the benefit that it allows inspection of the "whole spectrum", from F.
sub.
0 -Fs/2 to F.
sub.
0 +Fs/2, where F.
sub.
0 is the CDMA center frequency and Fs is the (baseband) sample rate.
The important question is now: In terms of jammer detection sensitivity, is option A or B better? Call the jammer power Pj, and thermal+user power for P
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Telecommunications 
