Real-Valued Passband Signal Processing in Distributed Antenna Systems
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Solution Overview
Problem
Current distributed antenna systems (DAS) face processing delays due to the need to schedule and serialize both real and imaginary components of digital baseband signals, which limits their flexibility and efficiency, especially when dealing with a wide range of signal bandwidths.
Innovation Solution
The system employs a passband representation, where signals are processed as purely real-valued digital passband signals, reducing processing delay by 50% by adapting the sample rate to the actual bandwidth of each channel and using decimation or resampling to reduce the amount of digital data, thereby mitigating the processing burden on schedulers and serializers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If digital baseband signals are processed by scheduling and serializing both real and imaginary components, then complete signal information is preserved, but processing delay increases
Solution Approach 1:
The patent changes the signal representation parameters from complex baseband (with real and imaginary components) to real-valued passband signals. This parameter transformation allows the signal to be processed as a single real-valued stream rather than two separate components, reducing processing delay while preserving signal information through the passband representation that maintains the spectral characteristics of the original signal.
2Quantity of substance
If high sample rates are used to cover the entire input signal band, then signal bandwidth is adequately represented, but the amount of digital data increases
Solution Approach 1:
The patent applies local quality by adapting the sample rate to the actual bandwidth requirements of each specific channel rather than using a uniform high sample rate for all channels. Each channel is processed with a sample rate matched to its bandwidth needs, reducing the total amount of digital data while maintaining adequate signal bandwidth representation for each individual channel.
3Measurement precision
If the ADC sample rate exceeds twice the total bandwidth to avoid aliasing, then signal reconstruction accuracy is improved, but the processing burden on schedulers and serializers increases
Solution Approach 1:
The patent changes the fundamental parameter of signal representation from complex baseband to real-valued passband, which allows for lower sample rates that still satisfy the Nyquist criterion for the actual signal bandwidth. This parameter change reduces the ADC sample rate requirement and consequently reduces the processing burden on schedulers and serializers while maintaining signal reconstruction accuracy.
Data Source
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AI summary
The invention relates to the implementation of an active distributed antenna system (DAS) transporting digital passband data. In a first aspect of the invention, a method is provided of transporting digital data in a DAS (100). The method comprises receiving (S101) data from at least one data source (101-104), processing (S102) the received data, and providing (S103) the processed data as digital real -valued passband data for further transport within the DAS (100).