Initial Access Method Using Multi-Beam Diversity in NR Systems
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Solution Overview
Problem
In the Long Term Evolution (LTE) and New Radio (NR) mobile communications systems, the initial access process is hindered by channel instability in high-frequency environments, leading to prolonged beam synchronization times and poor stability of downlink synchronization and random access response (RAR) messages, especially due to single beamforming and fixed window reception, which affects system stability and user experience.
Innovation Solution
The method involves sending synchronization signals and RAR messages using multiple downlink beams across various timeslots and frequency domain resource locations, enhancing beam and frequency diversity, and providing information about the relationship between downlink beam indexes and uplink random access resources to improve initial access performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single beamforming is used for downlink synchronization signal transmission, then device complexity is reduced, but beam synchronization time increases and system stability deteriorates
Solution Approach 1:
The patent divides the single beamforming approach into multiple beamforming instances (first downlink beam and second downlink beam). Each beam is transmitted separately in different time slots, allowing the user equipment to perform beam sweeping and synchronization on each segment independently, thereby reducing overall synchronization time while maintaining manageable device complexity
Solution Approach 2:
The patent implements periodic transmission of synchronization signals through multiple beams at different time slots. The access network device periodically switches between first and second downlink beams to transmit synchronization signals, enabling the user equipment to perform periodic beam sweeping and achieve faster beam synchronization without overwhelming system complexity
2Device complexity
If single beamforming is used for downlink synchronization signal transmission, then device complexity is reduced, but system stability deteriorates
Solution Approach 1:
The patent segments the single beam transmission into multiple independent beam transmissions (first downlink beam and second downlink beam). This segmentation provides diversity gain - if one beam experiences fading or blockage, the other beam can still deliver the synchronization signal, thereby improving system stability without significantly increasing device complexity
Solution Approach 2:
The patent changes the transmission parameters by using different time slots for different beams and potentially different frequency domain resource locations. This parameter diversity ensures that not all beams are affected by the same channel conditions simultaneously, improving reliability while keeping the beamforming mechanism itself relatively simple
3Device complexity
If fixed window RAR message reception is used, then device complexity is reduced, but receiving stability deteriorates
Solution Approach 1:
The patent transforms the fixed window reception approach into a dynamic multi-window reception mechanism. The user equipment is configured with multiple reception windows (first reception window and second reception window) at different time slots, allowing flexible adaptation to varying channel conditions and beam synchronization timing, thereby improving receiving stability without excessive complexity
Solution Approach 2:
The patent divides the single fixed reception window into multiple segmented reception windows. Each window corresponds to specific time slots where RAR messages may be transmitted using different beams. This segmentation allows the user equipment to monitor multiple potential transmission opportunities, improving reception reliability while maintaining manageable complexity
4Reliability
If multiple downlink beams are used for synchronization signal transmission, then beam diversity gain is achieved improving stability, but device complexity increases
Solution Approach 1:
The patent segments the multiple beam transmission into a structured sequence using first and second downlink beams in different time slots. This segmentation organizes the complexity into manageable segments that can be processed sequentially by the user equipment through beam sweeping, achieving diversity gain while keeping beam management complexity tractable
Solution Approach 2:
The patent employs periodic beam switching between first and second downlink beams at regular time intervals. This periodic action creates a predictable pattern that simplifies beam management - the user equipment knows when to expect each beam and can perform systematic beam sweeping, achieving stability through regularity rather than complex adaptive beam management
5Reliability
If multiple reception windows are used for RAR message reception, then receiving stability is improved, but device complexity increases
Solution Approach 1:
The patent segments the RAR message reception into multiple distinct windows (first and second reception windows) associated with different time slots and beams. This segmentation allows the user equipment to focus on one window at a time in a systematic sequence, improving reception stability through multiple opportunities while keeping window management complexity organized and tractable
Solution Approach 2:
The patent implements periodic opening of multiple reception windows at predetermined time intervals. This periodic structure creates a rhythmic reception pattern that simplifies timing synchronization and window management - the user equipment can follow a regular schedule for opening and monitoring windows, achieving improved reliability without excessive management complexity
Data Source
AI summary
Embodiments of the present invention provide an initial access method and apparatus. The method includes: sending, by an access network device, a synchronization signal to user equipment by using at least two downlink beams, where the synchronization signal includes downlink beam indexes of the at least two downlink beams; receiving, by the access network device, a random access preamble sequence sent by the user equipment; and sending, by the access network device, a random access response RAR message to the user equipment by using at least two downlink beams, so that the user equipment completes initial access. In the initial access method provided in the embodiments of the present invention, a disadvantage of channel instability in a high-frequency transmission environment in a new radio system is overcome, to improve initial access performance in the NR system and further improve user experience for the system.