Full-Duplex RACH Beam Pair Configuration for 5G NR
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Solution Overview
Problem
Current communication systems face challenges in managing overlapping random access channel (RACH) occasions and mixed mode RACH retransmission configurations, particularly in 5G NR technology, which affects the efficiency and reliability of wireless communication.
Innovation Solution
The proposed solution involves configuring beam pairs for full-duplex (FD) RACH operations, allowing for simultaneous transmission and reception of RACH messages and DL information, and implementing mixed mode RACH retransmissions using time division multiplexing (TDM), frequency division multiplexing (FDM), or spatial division multiplexing (SDM) based on specific thresholds and signaling protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional half-duplex RACH procedures are used, then device complexity is reduced, but latency increases due to sequential transmission and reception
Solution Approach 1:
The system dynamically switches between half-duplex and full-duplex modes based on operational requirements. The UE can operate in full-duplex mode during initial access to minimize latency, then transition to half-duplex mode for normal operation, making the duplexing mode adjustable rather than fixed.
Solution Approach 2:
The RACH procedure is segmented into distinct phases: initial access using full-duplex capability for rapid connection establishment, followed by transition to half-duplex mode for data transmission. This segmentation allows the system to apply different operational modes to different functional requirements.
2Productivity
If RACH occasions are configured to overlap with DL information reception, then spectral efficiency improves, but interference increases
Solution Approach 1:
The system resolves the time-frequency conflict by introducing a spatial dimension through beamforming. Different beams are used for DL information reception and RACH transmission, allowing simultaneous operation in overlapping time-frequency resources while maintaining signal quality through spatial separation.
Solution Approach 2:
Different quality requirements are applied to different spatial directions. The system configures specific beam pairs with appropriate reference signals for each direction, allowing high-quality DL reception in one beam while enabling RACH transmission in another beam, thus satisfying local quality requirements in each spatial sector.
3Reliability
If beam pairs are configured for full-duplex operation, then communication reliability improves, but device complexity increases
Solution Approach 1:
The beam pair configuration is designed to serve multiple functions: the same beam pairs are used for both DL information reception and RACH transmission during full-duplex operation, as well as for half-duplex operation during normal data transmission. This multi-functionality reduces the need for separate beam configurations for different operational modes.
Solution Approach 2:
Beam pairs and their associated reference signals are pre-configured during initial access before full-duplex operation begins. This preliminary configuration establishes the spatial channels needed for reliable simultaneous transmission and reception, so that when full-duplex mode is activated, the beam structures are already in place and do not add operational complexity.
4Quantity of substance
If RACH and DL information use the same time-frequency resources, then resource utilization improves, but measurement precision deteriorates
Solution Approach 1:
Reference signals act as intermediaries that enable the system to simultaneously support RACH and DL information in the same time-frequency resources. The reference signals provide the spatial channel information needed for the base station to separate and accurately detect both the RACH preamble and DL data, thus maintaining measurement precision while achieving high resource utilization.
Data Source
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Figure 2A~2D
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AI summary
A UE may receive, from a base station/TRP, a configuration for a beam pair including an UL beam and a DL beam and transmit a RACH message via the UL beam while receiving DL information via the DL beam. The UE and/or the base station/TRP may be configured to operate in a FD mode. In aspects, the UE may transmit a RACH preamble based on a first mode of transmission. After a threshold time delay measured from the transmission of the RACH preamble, the UE may retransmit the RACH preamble based on a second mode of transmission. The second mode of transmission may be a same mode of transmission or a different mode of transmission from the first mode of transmission. Each mode of transmission may be based on one or more of TDM, FDM, or SDM.