Synchronization Signal Block Beam Index Indication for Initial Access
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Solution Overview
Problem
High frequency band communication systems, such as those operating in the THz band, face challenges with excessive path loss, atmospheric absorption, and high rain attenuation, which necessitate highly directional beamforming, leading to increased complexity in beam acquisition mechanisms due to a large number of beams and significant carrier frequency offset.
Innovation Solution
The design of a downlink signal/channel for initial access that includes a synchronization signal block (SSB) with a primary synchronization signal (PSS) and secondary synchronization signal (SSS) transmitted using different beams, where the beam index is indicated through the signal or channel, allowing for efficient beam switching and multi-stage beam search, and the signals are multiplexed in the time or frequency domain to accommodate beam switching time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly directional beamforming is used to overcome high path loss and atmospheric absorption, then coverage and signal strength are improved, but beam acquisition complexity increases due to a large number of beams
Solution Approach 1:
The beam acquisition process is segmented into two stages: first, a first synchronization signal is transmitted using a first beam to enable initial detection; second, a second synchronization signal is transmitted using a second beam to provide refined beam information. This segmentation divides the complex beam acquisition into manageable steps, reducing overall complexity while maintaining coverage.
Solution Approach 2:
The first synchronization signal is transmitted in advance using a first beam to establish initial synchronization and provide preliminary beam information. This preliminary action prepares the receiver for subsequent beam refinement, reducing the complexity of the overall beam acquisition process by pre-establishing basic connectivity.
2Productivity
If multiple synchronization signals are transmitted using different beams, then beam acquisition efficiency is improved, but transmission time increases due to beam switching requirements
Solution Approach 1:
The first and second synchronization signals are transmitted in a periodic manner using different beams. The first synchronization signal is transmitted at a first time using a first beam, and the second synchronization signal is transmitted at a second time using a second beam. This periodic transmission structure allows the system to efficiently acquire beam information while managing beam switching time through regular intervals.
3Measurement precision
If beam index indication is implemented for each synchronization signal, then beam identification accuracy is improved, but signal overhead increases
Solution Approach 1:
Different quality levels of beam identification are applied to different synchronization signals. The first synchronization signal carries beam index information for the first beam, providing local beam identification. The second synchronization signal carries beam index information for the second beam, providing refined local beam identification. This local quality approach ensures accurate beam identification at each stage without requiring full beam information to be transmitted in every signal.
Data Source
AI summary
A synchronization signal block (SSB) including a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH) is transmitted using first and second beams. One or more symbols adjoining the first and second synchronization signals are configured to accommodate a beam switching time. At least one signal indicates a beam index for the first beam transmitting the first synchronization signal, and the beam index for the second beam transmitting the second synchronization signal is either signaled or determined based on a predetermined relationship between a resource for the first synchronization signal and a resource for the second synchronization signal. The beam indices may comprise first and second numbers of bits and/or may be jointly encoded. The beam indices may be indicated by one of the PSS, the SSS, the PBCH, a demodulation reference signal (DMRS), or a synchronization or reference signal designated for that purpose.