RACH Beamforming Feedback for mmW Link Reliability
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Solution Overview
Problem
In millimeter wave (mmW) communications and other beamformed communications, there is a need to improve the link between user equipment and base stations during the random access channel (RACH) procedure by enabling feedback of control information, particularly to overcome link attenuation and ensure reliable beamforming.
Innovation Solution
A method where user equipment receives a beam-formed message from a base station during the RACH procedure, determines beam information, and transmits this information back to the base station, allowing for improved beamforming adjustments and link reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamforming is used to overcome link attenuation in mmW communications, then link reliability is improved, but the complexity of the RACH procedure increases due to the need for accurate beamforming and feedback mechanisms
Solution Approach 1:
The patent applies preliminary action by performing beamforming adjustments and beam information feedback during the RACH procedure itself, rather than requiring separate preliminary beam training phases. The user equipment determines beam information from the beam-formed message and feeds it back in the third message, establishing accurate beamforming early in the connection establishment process.
Solution Approach 2:
The patent implements feedback by having the user equipment determine beam information based on the received beam-formed message and transmit this information back to the base station in the third message. This feedback loop enables the base station to adjust beamforming parameters accurately, improving link reliability while managing procedure complexity through efficient information exchange.
2Measurement precision
If beam information feedback is enabled during the RACH procedure, then beamforming accuracy is improved, but the amount of control information that needs to be transmitted increases
Solution Approach 1:
The patent applies multi-functionality by using the existing third message in the RACH procedure to serve dual purposes: maintaining uplink synchronization and transmitting beam information feedback. This approach enables accurate beamforming without requiring additional dedicated feedback messages, thereby avoiding increased control information overhead.
Solution Approach 2:
The patent merges the beam information feedback function with the existing RACH third message transmission. Instead of creating a separate feedback channel or message, the beam information is combined with the uplink synchronization message, efficiently utilizing existing communication resources and avoiding additional overhead.
3Reliability
If the RACH procedure includes beam information feedback, then link quality is improved, but the time required for the RACH procedure increases
Solution Approach 1:
The patent performs beam information determination and feedback during the initial RACH procedure rather than requiring subsequent separate beam training or adjustment phases. By establishing accurate beamforming early through the third message, the system avoids delays that would occur if beam adjustments were made after connection establishment.
Solution Approach 2:
The patent uses the existing RACH message structure to carry both synchronization and beam feedback functions simultaneously. This multi-functional approach ensures that beam information is exchanged without extending the basic RACH timing, as the feedback is embedded within the standard four-message sequence.
Data Source
AI summary
In a mmW network, a UE and a base station may establish a link using a RACH procedure. A base station may transmit, in a beamformed signal, a message to a UE during a RACH procedure. The message to the UE may include a value indicating a request for beam information. The base station may receive a message from the UE during the RACH procedure that includes a beam information report comprising the beam information.