Detect-and-avoid method and architecture for ultra-wideband system
A method and system for detecting the presence of narrowband transmitters utilizing frequencies also utilized by wider band communication systems. In some embodiments an ultrawideband transceiver detects signals at specific frequencies within a spectrum of frequencies, and analyzes the signals to determine if the signals indicate transmissions by a narrowband transmitter in a narrowband communication system. In further embodiments transmission circuitry reduces signal components at frequencies occupied by the narrowband transmitters.
1. A method, implemented in a communications transceiver, of detecting communications by narrowband communications systems for avoidance of interference with the narrowband communication systems, comprising: receiving a signal in a receive path of the communications transceiver; correlating the received signal with a plurality of different signal patterns stored in a library; determining, based on the correlating, whether the received signal corresponding to a selected frequency has characteristics of a signal expected to be communicated by a narrowband transmission system; marking a center frequency for nulling transmissions corresponding to the selected frequency in response to the determining operation; and adjusting a center frequency for transmissions, via a transmit path of the communications transceiver, in response to the determining operation, such that the center frequency for transmission avoids the marked center frequency, wherein the correlating further comprises performing an autocorrelation of the received signal corresponding to the selected frequency and performing a cross-correlation of the received signal with the signal expected to be communicated by the narrowband transmission system.
2. The method of claim 1 , further comprising sampling and filtering the received signal corresponding to the selected frequency.
3. The method of claim 1 , further comprising changing the selected frequency over time.
4. The method of claim 3 , further comprising determining frequencies at which signals are received, and changing the selected frequency to the frequencies at which signals are received over time.
5. The method of claim 1 further comprising maintaining in the library a plurality of signal patterns, the signal patterns corresponding to expected processed signals of narrowband transmitters in a narrowband transmission system.
6. The method of claim 5 wherein determining whether a received signal corresponding to the selected frequency matches the signal expected to be communicated by the narrowband transmission system comprises:
processing the received signal; and
comparing the processed received signal to the plurality of signal patterns.
7. A transceiver for a communication system, comprising: downconversion circuitry for downcoverting a received signal to baseband; an analog to digital converter for converting the baseband signal to a digital signal; a Fast Fourier Transform block for transforming the digital signal to a frequency domain signal; receiver processing circuitry for processing the frequency domain signal to provide a data stream; a filter for filtering the digital signal outside a band of frequencies to provide a band filtered signal; a correlator for correlating the band filtered signal to a plurality of signal patterns stored in a library, wherein each signal pattern is characteristic of a signal in a narrowband communication system, the correlator configured to perform the correlating by cross-correlating the band filtered signal with a signal expected to be communicated by the narrowband transmission system and performing an autocorrelation of the band filtered signal corresponding to a selected frequency; an inverse Fast Fourier Transform block for transforming a signal for transmission to a time domain signal; a digital to analog converter for converting the time domain signal to an analog signal; upconversion circuitry for upconverting the analog signal to radio frequency; and circuitry for nulling transmissions corresponding to frequencies identified as in use by the narrowband communication system.
8. The transceiver of claim 7 further comprising a downsampler for reducing a number of bits of the band filtered signal.
9. The transceiver of claim 8 further comprising a phase shifter for shifting the digital signal in frequency by a center frequency of the band of frequencies, and wherein the filter is a symmetric Finite Impulse Response (FIR) filter.
10. The transceiver of claim 9 further comprising energy evaluation circuitry for determining energy levels at different frequencies of the frequency domain signal.
11. The transceiver of claim 10 further comprising a processor configured to select the center frequency for the band of frequencies based on outputs of the energy evaluation circuitry.
12. The transceiver of claim 7 wherein the pattern characteristic of a signal in a narrowband communication system is a pattern characteristic of a preamble sequence in a narrowband communication system.
13. The transceiver of claim 7 , wherein the pattern characteristic of a signal in a narrowband communication system comprises patterns formed by processing of expected received signals of a narrowband communication system.