Supplementary Uplink RACH Configuration for 5G Link Budget
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G New Radio (NR) and LTE, face challenges in establishing efficient uplink connections due to link budget limitations and propagation losses, especially with high-frequency bands, which affect channel quality and require supplementary uplink channels to compensate for these issues.
Innovation Solution
The implementation of supplementary uplink (SUL) random access channel (RACH) procedures, where user equipment (UE) uses low-frequency bands in addition to or instead of high-frequency bands for uplink communication, with RACH configuration parameters broadcasted in the remaining minimum system information (RMSI) to select the appropriate base station for SUL, enhancing channel quality and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-frequency bands are used for uplink communication, then spectral efficiency is improved, but propagation losses increase and channel quality deteriorates
Solution Approach 1:
The patent changes the frequency parameter by introducing supplementary uplink (SUL) carriers at low frequencies (e.g., sub-6 GHz) alongside high-frequency carriers. This allows the system to dynamically switch or aggregate between different frequency parameters, maintaining spectral efficiency benefits while compensating for propagation losses through the lower-frequency SUL carriers that experience less path loss and better penetration.
2Reliability
If supplementary uplink carriers are added to compensate for propagation losses, then channel quality improves, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by enabling user equipment to operate on both high-frequency and low-frequency carriers within the same system framework. The SUL carriers serve multiple purposes: compensating for propagation losses, providing fallback options, and enabling seamless transitions between frequency bands. This universal approach allows a single device design to handle diverse channel conditions without requiring fundamentally different hardware architectures.
Solution Approach 2:
The system dynamically selects between SUL and non-SUL carriers based on real-time channel conditions, UE capability, and network configuration. The dynamic switching mechanism allows the system to adapt to varying propagation conditions, activating SUL only when needed (e.g., at cell edges or in poor channel conditions) while defaulting to conventional high-frequency carriers when conditions are favorable, thereby managing complexity through intelligent adaptation rather than permanent structural changes.
3Productivity
If RACH configuration parameters are broadcasted in RMSI for SUL carrier selection, then access efficiency is improved, but information overhead increases
Solution Approach 1:
The patent applies local quality by providing differentiated RACH configuration information specifically for SUL carriers within the RMSI broadcast. Rather than broadcasting complete RACH configurations for all possible carriers, the system selectively includes SUL-specific parameters (such as SUL-RACH-ConfigCommon) only where needed - i.e., when SUL carriers are configured and relevant for particular UEs or geographic areas. This localized information provision improves access efficiency for SUL operations while minimizing overall broadcast overhead by avoiding redundant information transmission.
Data Source
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AI summary
Certain aspects of the present disclosure provide techniques for ordering a plurality of potential base stations to serve a user equipment on a supplemental uplink and providing random access channel (RACH) configuration parameters for each of the plurality of potential base stations to the user equipment. Certain aspects provide a method for wireless communication. The method generally includes communicating, by a user equipment (UE), with a first base station (BS) on a downlink on a first frequency band. The method further includes receiving, by the UE from the first BS, a list comprising RACH configuration parameters for each of a plurality of BSs. The method further includes selecting a second BS from the plurality of BSs based on an ordering of the plurality of BSs in the list and performing a RACH procedure with the second BS.