Beam Selection in Wireless Random Access via RACH Mapping
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in random access procedures using beamformed signals, particularly in identifying and establishing optimal transmission beams for reliable and efficient network access with minimal delay and signaling overhead.
Innovation Solution
The implementation of a method where user equipment (UE) selects transmission beams from a first set for initial access, with corresponding random access channel (RACH) resources, and receives configuration information to also use an additional transmission beam mapped to the same RACH resource, allowing for efficient beam refinement and reduced overhead during connection establishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamformed signals are used for transmission, then path losses are mitigated and transmission reliability is improved, but the complexity of random access procedures increases due to beam identification and selection requirements
Solution Approach 1:
The base station performs beam sweeping and transmits synchronization signal blocks (SSBs) in advance across multiple beams before the random access procedure. This preliminary action allows the UE to identify the preferred beam beforehand, so that when the random access preamble is transmitted, the base station already knows which beam to use for subsequent communication, thereby reducing procedure complexity while maintaining reliability
Solution Approach 2:
The patent introduces RACH resource partitions as an intermediary mechanism that links UE-selected beams to base station transmission beams. By mapping specific RACH resources to specific beams, the system creates an indirect connection that simplifies beam identification during random access, reducing the complexity of direct beam selection while maintaining the reliability benefits of beamforming
2Measurement precision
If RACH resources are partitioned for different beams, then beam identification accuracy is improved, but signaling overhead increases due to additional configuration information
Solution Approach 1:
The patent applies local quality by making RACH resources beam-specific through partitioning. Each beam is associated with specific time-frequency resources, allowing the base station to identify the preferred beam by detecting which RACH resources the UE uses. This localized mapping improves beam identification accuracy while minimizing signaling overhead by using the existing RACH structure rather than adding new signaling messages
3Reliability
If beam sweep procedures are implemented, then coverage and reliability are improved, but access delay increases due to multiple beam transmissions
Solution Approach 1:
The base station performs beam sweeping and transmits SSBs in advance across multiple beams before the actual random access procedure begins. This preliminary beam training allows the UE to identify the preferred beam beforehand, so that when the random access preamble is transmitted on the selected beam, no additional beam refinement is needed, thereby maintaining reliability while minimizing access delay
Solution Approach 2:
The patent segments the random access procedure into distinct phases: initial beam identification through SSB monitoring, followed by random access preamble transmission on the selected beam. This segmentation allows the beam selection to be completed in advance, separating the time-consuming beam sweep from the actual access procedure, thereby reducing overall access delay while maintaining reliable connection establishment
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that provide for selection of different sets of transmission beams by a user equipment (UE) for establishing beamformed communications with a base station. Each transmission beam of a first set of transmission beams may have corresponding uplink random access channel (RACH) resources. A UE may monitor for transmission beams from a base station and select a first transmission beam of the first set for communications with the base station. As part of a connection establishment, the base station may provide configuration information that indicates a second set of transmission beams that includes each transmission beam of the first set of transmission beams and at least an additional transmission beam. In some cases, the additional transmission beam may be mapped to a first RACH resource that also corresponds to a first transmission beam of the first set of transmission beams.