Wireless Microphone Pilot Tone Detection in TV White Space
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Solution Overview
Problem
Current technologies fail to reliably detect wireless microphone systems operating in TV Band channels at the stringent -114 dBm sensing threshold, posing challenges in protecting primary users like digital television broadcasters and wireless microphones from interference.
Innovation Solution
Broadcasting a pilot tone within the frequency band designated for the ATSC pilot in TV Band channels, allowing TV Band devices to detect the presence of wireless microphones, thereby determining channel occupancy and ensuring protection from interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex receiver/detector capable of detecting spread spectrum beacon signals is equipped in every TV Band device, then wireless microphone detection capability is improved, but device cost increases
Solution Approach 1:
The patent extracts only the essential detection function needed for wireless microphone protection by detecting the ATSC pilot signal, eliminating the need for complex spread spectrum beacon detection capabilities while maintaining effective channel occupancy detection
Solution Approach 2:
The patent uses the existing ATSC pilot signal structure as a detection marker for wireless microphone presence, copying the pilot detection methodology from DTV systems to wireless microphone detection, thereby simplifying the receiver design while maintaining detection effectiveness
2Reliability
If the sensing threshold is set to -114 dBm to meet FCC requirements, then protection reliability is improved, but detection capability deteriorates due to signal weakness
Solution Approach 1:
The patent uses the ATSC pilot signal as an intermediary marker that provides a reliable detection reference point, allowing TV Band devices to accurately detect wireless microphone presence even at the stringent -114 dBm sensing threshold by focusing detection energy on the pilot signal component
3Ease of operation
If ATSC pilot detection is used to determine channel occupancy, then detection simplicity is improved, but wireless microphone-specific detection deteriorates
Solution Approach 1:
The patent makes the ATSC pilot detection mechanism universal by using it to serve dual purposes: detecting both DTV channel occupancy and wireless microphone presence, thereby simplifying the detection process while maintaining reliability for wireless microphone protection through database cross-referencing
Data Source
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AI summary
A method of determining whether a TV band channel is available for use by a TV band device a corresponding device, the method comprising: tuning to a TV band channel; detecting a pilot tone within the TV band channel to obtain a radio frequency signal, wherein the pilot tone is a single tone modulated by a modulating sequence {b} = {+M, -M, +M, -M, +M, -M, +M ...} with a predetermined signal period assigned such that a bandwidth of the modulated pilot tone is maintained within a narrowband centered on the location of an Advanced Television Systems Committee (ATSC) pilot for a DTV broadcast; down-converting the radio frequency signal received on the TV band channel to yield a down-converted signal; performing a predetermined number of Fast Fourier Transforms (FFTs) on the down-converted signal and accumulating an energy of respective bins associated with the respective FFTs; selecting a predetermined number of FFT bins centered at a mandated location of an Advanced Television Systems Committee (ATSC) pilot in the TV Band channel; and analyzing the selected FFT bins to determine if an energy spike is present in any one of the selected FFT bins.