MIMO Receiver Time-Delay Cancellation for Wideband Interference
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Solution Overview
Problem
Next-generation wireless communication systems with wideband modulated signals face challenges in spatial interference cancellation, particularly in dense small-cell networks, where existing phase-shift methods result in imperfect interference cancellation and increased dynamic range requirements for ADCs, leading to power and area inefficiencies.
Innovation Solution
A true time-delay technique is employed for spatial interference cancellation in MIMO receivers, which time-aligns desired and undesired signals and uses a cancellation matrix to remove interference, reducing power consumption and area requirements while being scalable with bandwidth, process, and supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-shift method is used for interference cancellation, then interference cancellation is achieved at a single frequency, but interference leakage occurs and cancellation becomes imperfect for wideband modulated signals
Solution Approach 1:
The patent changes the fundamental parameter from phase-shift (frequency-dependent) to true time-delay (frequency-independent). By using time-domain delay elements instead of phase-shifters, the system achieves interference cancellation that is independent of frequency, thereby resolving the contradiction between cancellation precision and bandwidth adaptability for wideband modulated signals.
2Measurement precision
If phase-shift method is used for interference cancellation, then single frequency cancellation is achieved, but dynamic range requirements for baseband and ADC increase significantly
Solution Approach 1:
The patent changes the cancellation parameter from phase-shift to true time-delay, which fundamentally alters how interference is cancelled. Time-delay based cancellation achieves frequency-independent suppression, preventing the accumulation of interference leakage across the bandwidth that would otherwise require increased dynamic range in the baseband and ADC.
3Measurement precision
If phase-shift method is used for interference cancellation, then single frequency null is generated, but higher area and power are required for implementation
Solution Approach 1:
The patent replaces the RF phase-shifter mechanism with a baseband time-delay mechanism. This substitution moves the interference cancellation function from the RF domain to the baseband domain, where time-delay can be implemented more efficiently using digital signal processing, thereby reducing the area and power requirements.
4Measurement precision
If phase-shift method is used for interference cancellation, then single frequency cancellation is achieved, but passive device mismatches occur
Solution Approach 1:
The patent replaces passive RF phase-shifters with active baseband time-delay elements. This substitution eliminates the passive device mismatches that occur in RF phase-shifters because the time-delay implementation is done in the digital baseband domain where precision can be maintained through digital processing rather than being limited by passive component tolerances.
Data Source
AI summary
A discrete-time delay (TD) technique in a baseband receiver array is disclosed for canceling wide modulated bandwidth spatial interference and reducing the Analog-to-Digital Conversion (ADC) dynamic range requirements. In particular, the discrete-time delay (TD) technique first aligns the interference using non-uniform sampled phases followed by uniform cancellation using a cancellation matrix, such as, for example, a Truncated Hadamard Transform implemented with antipodal binary coefficients.