Method for estimating signal-to-noise ratio of digital carriers in AM compatible digital audio broadcasting system
A technology of signal-to-noise ratio and digital information, applied in the transmission system, orthogonal multiplexing system, communication between multiple stations, etc., can solve the problems of signal detection, digital broadcasting signal cannot be restored, etc.
Inactive Publication Date: 2002-07-10
IBIQUITY DIGITAL CORP
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Without this equalization, the severely distorted signal will be detected and the information of the digital broadcast signal will not be able to be recovered
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[0018] Hybrid In-Band On-Channel (IBOC) digital audio broadcasting systems allow simultaneous transmission of analog and digital encoded audio signals on the same channel. The transmitted signal contains a digital carrier extending approximately ±15 kHz from the AM carrier of the current analog AM signal with an audio bandwidth limited to approximately 5 kHz. In addition to carrying the digitally encoded audio signal, the digital carrier periodically carries data called a "training sequence". This broadcasting is accomplished by transmitting digital waveforms with the aid of multiple orthogonal frequency division modulated (OFDM) carriers, some of which are quadrature modulated with analog AM signals, in regions of the spectrum where standard AM broadcast signals occupy significant energy Inside. The remaining digital carriers are in-phase and quadrature modulated with analog AM signals, which are located in the same channel as the analog AM signals, but in spectral regions w...
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A method of estimating SNR for a plurality of carriers modulated with digital information, wherein the digital information includes data baud and training baud, comprising the steps of: receiving the plurality of carriers; determining a first SNR for the data baud; determining a second SNR for the training baud; comparing at least one of the first and second SNRs to predetermined selection criteria; and selecting one of the first and said second SNRs based on the comparison step. In the preferred embodiment, the carriers are processed to produce an equalizer output for each of the carriers, and the equalizer output is processed to produce a symbol decision for each of the carriers. The equalizer output is subtracted from the symbol decision when a data baud is received to produce a first difference value, and the first difference value is squared to produce a first signal to noise estimate. The equalizer output is also subtracted from predetermined training data when a training baud is received to produce a second difference value, and the second difference value is squared to produce a second signal to noise estimate. Apparatus that performs the above method is also included.
Description
Technical field: [0001] The present invention relates to radio broadcasting, and in particular to a method and apparatus for estimating the signal-to-noise ratio (SNR) of a digital carrier in an amplitude modulation (AM) compatible digital broadcasting system. Background technique: [0002] There has been increasing interest in the possibility of broadcasting digitally encoded audio signals to provide improved sound fidelity. Several approaches have been suggested for this. One is US Patent No. 5,588,022, which proposes a method for simultaneously broadcasting analog and digital signals on a standard AM broadcast channel. AM radio frequency signals for broadcasting have a first frequency spectrum. The AM radio frequency signal includes a first carrier modulated by an analog signal, while a plurality of digitally modulated carrier signals for broadcasting are located within a bandwidth encompassed by the first frequency spectrum. Each digitally modulated carrier signal is ...
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IPC IPC(8): H03M13/25H04B17/00H04J11/00
CPCH04B17/336H04B17/006H04B7/26
Inventor 唐·R·高德斯通马库斯·M·马舍恩
Owner IBIQUITY DIGITAL CORP