Group Delay Detection in Wideband Transceivers
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Solution Overview
Problem
Wideband communication systems, such as LTE-advanced, face challenges in detecting and calibrating group delay across multiple frequency subbands, which affects system performance and antenna gain due to frequency-selectivity, and existing interfaces like CPRI are inadequate for this purpose.
Innovation Solution
A transceiver system that splits available bandwidth into contiguous subcarriers, generates constant amplitude zero auto-correlation (CAZAC) calibration sequences, maps and superimposes them to form a CAZAC calibration signal, and uses FFT and IFFT operations to detect group delay by estimating the maximum amplitude value and corresponding time index in the time domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wideband communication systems use carrier aggregation to support 100 MHz bandwidth, then system bandwidth and data rates are improved, but frequency-selectivity and group delay variations increase
Solution Approach 1:
The patent segments the wideband system into multiple subbands (first subband and second subband) and performs separate calibration for each subband. This segmentation allows the system to handle frequency-selectivity and group delay variations on a per-subband basis, maintaining channel response consistency across the entire 100 MHz bandwidth despite the increased frequency variations.
2Reliability
If calibration is performed across the entire wideband RF chain, then overall system calibration is achieved, but measurement time and complexity increase
Solution Approach 1:
The calibration process is divided into separate subband calibrations rather than performing a single comprehensive wideband calibration. The system transmits calibration signals in the first subband, performs calibration, then transmits calibration signals in the second subband and performs calibration again. This segmented approach reduces the time and complexity of each individual calibration measurement while maintaining overall calibration accuracy across the full bandwidth.
Solution Approach 2:
The patent implements periodic calibration actions by transmitting calibration signals alternately in different subbands and performing calibration measurements at each period. This periodic approach allows the system to maintain accurate calibration across the wideband without requiring a single lengthy continuous measurement, thereby reducing overall calibration time while preserving accuracy.
3Adaptability or versatility
If existing CPRI interface is used for delay detection, then infrastructure compatibility is maintained, but group delay detection capability is insufficient
Solution Approach 1:
The patent introduces a new calibration interface that acts as an intermediary between the existing CPRI infrastructure and the required group delay detection functionality. This new interface extends the CPRI capabilities by adding specific calibration signal transmission and group delay measurement functions, allowing the system to maintain compatibility with existing CPRI infrastructure while achieving precise group delay detection across multiple subbands.
Data Source
AI summary
The exemplary embodiments of the present invention relate to a transmission part (500), to a receiver part (600), to a transceiver comprising the transmission and receiver parts, to a radio base station comprising the transceiver, to a method in the transmission part (500) and to a method in a receiver part (600). According to the embodiments of the present invention, the transmission part (500) is configured to generate calibration sequences; process the sequences to determine a resulting calibration signal prior to transmission to a receiver part for enabling the receiver part to detect group delay of the received resulting calibration signal for calibration of the transceiver and/or of the radio base station in a wideband communications system.