Uplink Sounding Channel Configuration for Massive MIMO Beamforming
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Solution Overview
Problem
In beamformed massive MIMO systems, the complexity of uplink channel sounding increases with the use of multiple beams, making it challenging to efficiently configure and manage uplink sounding channels, especially in millimeter wave frequencies where propagation loss is higher and antenna arrays require more precise beamforming.
Innovation Solution
A method is introduced where a base station configures an uplink sounding channel using OFDM symbols with varying subcarrier spacing and sampling frequencies, allowing for different transmit-receive beam pairs, and coordinates with neighboring base stations to optimize the configuration based on mobile speed, CQI reports, and RACH reception, enabling multiple sounding channels with varying periodicities and configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple beams are used for both mobile station and base station, then beamforming gain compensates for higher propagation loss in millimeter wave bands, but the complexity of uplink channel sounding increases
Solution Approach 1:
The patent segments the channel sounding process by introducing separate sounding reference signal (SRS) resources specifically for uplink beamforming, distinct from data transmission resources. This segmentation allows independent optimization of sounding procedures and reduces the complexity burden on the overall system by isolating the beam management functions.
Solution Approach 2:
The patent implements preliminary beam sweeping and sounding before actual data transmission. The base station performs downlink beam sweeping to identify suitable beam pairs, and the mobile station performs uplink beam sweeping to establish beamforming parameters. This preliminary action establishes the beam configuration in advance, simplifying subsequent channel sounding operations.
2Adaptability or versatility
If OFDM symbols with varying subcarrier spacing and sampling frequency are used for sounding, then different transmit-receive beam pairs can be scanned, but the configuration complexity increases
Solution Approach 1:
The patent introduces dynamic parameters for sounding reference signals, including variable subcarrier spacing, sampling frequency, and cyclic shifts. These dynamic parameters allow the system to adapt the sounding configuration to different beam pairs and channel conditions, enabling flexible scanning of transmit-receive beam pairs while maintaining manageable configuration complexity through parameterization.
Solution Approach 2:
The patent changes key parameters of the OFDM symbols used for sounding, including subcarrier spacing, sampling frequency, and cyclic shift values. By varying these parameters across different sounding instances, the system can scan multiple beam pairs and distinguish between different spatial channels, achieving versatile beam pair scanning capability.
3Measurement precision
If multiple sounding channels with different periodicities are configured, then channel quality assessment is enhanced, but the management and coordination overhead increases
Solution Approach 1:
The patent implements periodic sounding reference signal transmissions with different periodicities for different sounding channels. Fast periodic sounding captures rapid channel variations, while slower periodic sounding provides overall channel quality trends. This multi-periodic approach enhances measurement precision by capturing channel behavior at different time scales while organizing the complexity through structured periodic patterns.
Solution Approach 2:
The patent configures multiple sounding channels with different periodicities and resource allocations, using more sounding resources than strictly necessary for basic functionality. This excessive action provides redundant measurements and enhanced channel quality assessment capability, allowing the system to select and combine measurements from multiple channels to improve accuracy.
4Reliability
If inter-base station coordination is implemented for sounding configuration, then connection quality between mobile station and base station is improved, but the signaling overhead and processing load increase
Solution Approach 1:
The patent uses the mobile station as an intermediary in the coordination process between base stations. The mobile station reports channel quality measurements and beamforming performance back to its serving base station, which then coordinates with neighboring base stations based on this feedback. This intermediary approach improves connection quality through coordinated beam management while reducing direct signaling overhead between base stations.
Solution Approach 2:
The patent implements feedback mechanisms where mobile stations report channel quality indicators, reference signal received power, and beamforming performance metrics to base stations. Base stations use this feedback to adjust sounding configurations and coordinate with neighboring base stations, improving connection quality through data-driven decisions while managing coordination overhead through selective information exchange.
Data Source
AI summary
Base station (BS) and mobile station (MS) methods and apparatus are provided. The BS configures an uplink sounding channel made up of at least one OFDM symbol in an uplink slot. The BS signals to the MS use and location of different configurations of the uplink sounding channel via a system configuration broadcast message. The uplink sounding channel comprises OFDM symbols where one or more of a subcarrier spacing and a sampling frequency is different from that of OFDM symbol used for data transmission. Each OFDM symbol comprises a sounding reference symbol corresponding to at least one transmit beam and is received by at least one receive beam to form at least one transmit-receive beam pair. The at least one transmit-receive beam pair for UL-SRS in different OFDM symbols are different. The sounding channel configuration is based on information received from neighboring BSs via inter-BS coordination over a pre-defined interface.