Adaptive Reference Signals for Phase Noise Compensation
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Solution Overview
Problem
Phase noise, specifically common phase error (CPE) and inter-carrier interference (ICI), pose significant challenges in orthogonal frequency division multiplexing (OFDM) communication systems, particularly at high carrier frequencies, leading to reduced spectrum efficiency and performance degradation, especially with the advent of Massive MIMO in 5G networks.
Innovation Solution
The method involves transmitting and receiving adaptive reference signals (RS) within the communication channel, with the amount and structure of these signals depending on the modulation and coding scheme used, to compensate for phase noise. These reference signals are mapped to specific radio resources, either contiguous or non-contiguous in frequency, to facilitate CPE and ICI correction, optimizing resource allocation based on the communication environment and receiver capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an oscillator that produces less phase noise is used, then phase noise is reduced, but the cost of producing transmitting devices increases
Solution Approach 1:
The patent extracts the phase noise compensation function from the oscillator hardware and implements it through software-based reference signal processing. By separating the phase noise mitigation function from the physical oscillator, the system achieves phase noise reduction without requiring expensive low-phase-noise oscillators, thus resolving the contradiction between phase noise performance and manufacturing cost
Solution Approach 2:
The patent introduces reference signals as an intermediary element between the transmitter and receiver to measure and compensate for phase noise effects. These reference signals serve as a mediator that enables the system to detect and correct phase noise without needing expensive hardware modifications, thereby achieving phase noise mitigation at low cost
2Object-affected harmful factors
If the OFDM sub-carrier spacing is increased and symbol time period is reduced, then phase noise is reduced, but spectrum efficiency decreases due to increased CP overhead
Solution Approach 1:
The patent changes the approach from modifying OFDM physical parameters (sub-carrier spacing, symbol time) to modifying the signal processing parameters through reference signal-based phase noise compensation. This allows the system to maintain standard OFDM configurations for spectral efficiency while achieving phase noise mitigation through adaptive reference signal processing and compensation algorithms
3Productivity
If the CP length is shortened, then spectrum efficiency is improved, but performance degrades due to delay spread in the radio channel
Solution Approach 1:
The patent implements feedback through reference signals that provide information about channel conditions and phase noise effects. The receiver uses these reference signals to measure the actual channel response and phase noise, then feeds this information back for compensation. This feedback mechanism enables the system to maintain short CP lengths for spectral efficiency while compensating for delay spread effects to preserve performance
4Object-affected harmful factors
If reference signals are transmitted to compensate for phase noise, then phase noise mitigation is achieved, but radio resources are consumed
Solution Approach 1:
The patent applies partial action by transmitting reference signals only when and where phase noise compensation is needed, rather than continuously across all resources. The reference signals are placed selectively in time-frequency resources based on the specific requirements for phase noise mitigation, consuming only the necessary amount of radio resources while achieving effective phase noise compensation
Data Source
AI summary
Described are methods for dealing with phase noise, e.g., common phase error and/or inter-carrier interference, in communication systems, and apparatuses for the same. A method can include at least: transmitting one or more reference signals (in-band signals within a channel); and mapping the reference signals to radio resources in the channel for transmission of the reference signals. An amount of the radio resources may depend on, e.g., information about a modulation and coding scheme used for transmission. An associated method can include at least: receiving one or more reference signals, and mapping the reference signals to radio resources in the channel for reception of the reference signals; receiving information about a modulation and coding scheme to be used, an amount of the radio resources depending on, e.g., information about the modulation and coding scheme used for reception; and using the reference signals to compensate for phase noise.