PRACH Sub-beam Feedback for mmWave Initial Access
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In Long Term Evolution (LTE) and 5G New Radio communication technologies, millimeter wave (mmWave) frequency bands face significant challenges with free-space pathloss and atmospheric absorption, leading to reduced coverage and increased susceptibility to signal degradation during initial access procedures, particularly for broadcast transmissions and random access channel messages.
Innovation Solution
The implementation of systems and methods where a base station transmits Remaining Minimum System Information (RMSI) Downlink Control Information (DCI) indicating the time and frequency resources for a Channel State Indicator-Reference Signal (CSI-RS), allowing wireless devices to select a sub-beam associated with a synchronization signal block (SSB) based on received power, and send this selection in a Physical Random Access Channel (PRACH) message, enabling enhanced beamformed communications for initial access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If millimeter wave frequency bands are used to provide high bandwidth communication links, then communication bandwidth is improved, but signal coverage and reliability deteriorate due to free-space pathloss and atmospheric absorption
Solution Approach 1:
The patent segments the broad beam into multiple sub-beams, allowing the system to divide the coverage area into smaller directional sectors. This segmentation enables more focused signal transmission in each sub-beam direction, compensating for the high pathloss characteristics of mmWave frequencies and improving reliable coverage in specific directions.
Solution Approach 2:
The patent introduces spatial dimensionality by transitioning from omnidirectional or broad beam transmission to multi-directional sub-beam transmission. By adding the angular/directional dimension to signal transmission, the system can target specific geographic areas with enhanced signal strength, overcoming the inherent coverage limitations of mmWave frequencies.
2Adaptability or versatility
If broadcast transmissions are used for initial access procedures, then system information can be transmitted to multiple devices, but signal degradation increases due to atmospheric absorption and pathloss
Solution Approach 1:
The broadcast transmission is segmented into multiple directional sub-beams, each targeting a specific sector. This allows the system to maintain omnidirectional coverage capability while reducing signal degradation in each specific direction by concentrating power into focused sub-beams rather than spreading it uniformly in all directions.
Solution Approach 2:
The system dynamically selects and transmits sub-beams based on current channel conditions and device locations. This dynamic adaptation allows the broadcast transmission to optimize signal strength in real-time, compensating for atmospheric absorption and pathloss by adjusting which sub-beams are active and their transmission parameters.
3Device complexity
If conventional initial access procedures are used in mmWave conditions, then standard communication protocols are maintained, but coverage and reliability fail in challenging propagation conditions
Solution Approach 1:
The patent segments the random access channel (RACH) procedure into beam-specific sub-procedures, where devices can indicate their selected sub-beam in the RACH message. This segmentation allows the system to maintain protocol compatibility while adding beam-specific optimization that improves access reliability in mmWave conditions.
Solution Approach 2:
The patent implements feedback mechanisms where wireless devices report their selected sub-beam information back to the base station in the RACH message. This feedback enables the base station to adjust subsequent transmissions to match the device's optimal reception direction, significantly improving access reliability while maintaining protocol compatibility through structured message exchanges.
Data Source
AI summary
In embodiments of systems and methods for managing communication between a wireless device and a base station, a base station may transmit Remaining Minimum System Information (RMSI) Downlink Control Information (DCI) indicating time and frequency resources for RMSI. A wireless device may receive a Channel State Indicator-Reference Signal (CSI-RS) based on the time and frequency resources for RMSI and may select a sub-beam of a beam associated with a synchronization signal block (SSB). The wireless device may send to the base station an indication of the selected sub-beam associated with the SSB in a Physical Random Access Channel (PRACH) message. The base station and the wireless device each may then perform an initial access procedure using the selected sub-beam to enable the wireless device to establish a communication link with the base station.