Uplink Beam Selection via Reference Signals in Massive MIMO
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Solution Overview
Problem
Current wireless communication technologies, particularly in the 5G mmWave spectrum, face challenges in achieving robust uplink beam selection due to the limitations of user equipment (UE) antennas and the assumption of reciprocity between downlink and uplink channels, which can lead to poor link budget and increased bit/block error rates.
Innovation Solution
A method and apparatus for enhancing uplink beam selection by triggering an enhanced uplink beam selection protocol based on quality of uplink signaling, using uplink beam reference signals (U-BRS) to select and notify the UE for improved beam usage, which can be deployed as a stand-alone or supplementary protocol to conventional reciprocity techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reciprocity techniques are used for uplink beam selection, then device complexity is reduced, but transmission reliability deteriorates due to poor link budget and increased bit/block error rates
Solution Approach 1:
The network triggers an enhanced uplink beam selection protocol by sending downlink signaling that initiates a preliminary beam selection process. The UE responds by transmitting uplink beam reference signals (U-BRS) on multiple pre-defined uplink beams before actual data transmission, allowing the network to evaluate and select the best beam in advance, thereby improving transmission reliability without requiring complex real-time decisions during data transmission.
Solution Approach 2:
Uplink beam reference signals (U-BRS) are introduced as intermediary signals that facilitate beam selection. These reference signals are transmitted on multiple candidate uplink beams and serve as a medium for the network to evaluate beam quality and make informed selection decisions, improving reliability by enabling accurate beam assessment without direct data transmission testing.
2Volume of moving object
If UE uses fewer antennas due to size restrictions, then device portability is improved, but beamforming capability deteriorates leading to poor uplink performance
Solution Approach 1:
Instead of relying on the UE's limited physical antennas to create multiple independent beams, the system uses a copying approach where the UE transmits reference signals on multiple virtual or logical beams formed by phase shifting and signal processing. The network evaluates these copied beam versions and selects the best one, allowing effective beamforming performance despite the UE's small antenna array.
3Reliability
If enhanced uplink beam selection protocol is implemented, then link budget is improved, but signaling overhead increases
Solution Approach 1:
The enhanced protocol implements partial beam selection by evaluating only a subset of possible beams or using pre-defined beam sets rather than exhaustively testing all possible beam combinations. The network triggers the protocol selectively based on conditions such as channel quality thresholds, applying the enhanced selection only when necessary rather than always, thereby improving link budget when needed while minimizing signaling overhead during normal operation.
Data Source
AI summary
A radio network sends downlink signaling to a user equipment (UE) that triggers an enhanced uplink beam selection protocol, based on quality of the UE's uplink signaling the network receives according to a basic uplink beam selection protocol. In response the UE transmits pre-defined signaling such as uplink beam references signals (U-BRS) with uplink beams according to the downlink signaling. The network measures and selects one or more of those uplink beams for the UE to use for sending uplink data, and notifies this selection to the UE. In various embodiments the basic uplink beam selection protocol is based on uplink-downlink reciprocity, the downlink triggering signaling is dynamic and further selects a subset of uplink beams, and multiple UEs can be triggered in common signaling where blind decoding by the UEs is enabled via a scrambling ID for this enhanced uplink beam selection protocol purpose.