PRACH Power Control for Uplink Coverage in 5G
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Solution Overview
Problem
Next-generation wireless communication systems, such as 5G and 6G, face challenges in maintaining adequate uplink coverage due to increased path loss at higher carrier frequencies, particularly in NR Rel-15, where the 4-step RACH procedure struggles with short PRACH formats and power control mechanisms for multiple transmissions.
Innovation Solution
Implementing repetition level ramping and transmit power control mechanisms for multiple PRACH transmissions, allowing UE to adjust repetition levels and power allocation based on RSRP measurements and configured thresholds, enabling effective PRACH detection and improving coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple PRACH transmissions are implemented to improve uplink coverage in high-path-loss scenarios, then coverage reliability is improved, but transmit power control complexity increases
Solution Approach 1:
The patent implements dynamic transmit power control for multiple PRACH transmissions by adjusting the transmit power of each repetition based on whether previous transmissions were successfully received. The UE monitors for RAR responses and adjusts subsequent transmission powers accordingly, creating a dynamic power control mechanism that adapts to channel conditions and previous transmission outcomes.
Solution Approach 2:
The patent employs feedback mechanisms where the UE monitors for Random Access Responses (RAR) from the gNB after each PRACH transmission. Based on whether RAR is received or not, the UE adjusts the transmit power for subsequent PRACH repetitions. This feedback-driven approach allows the system to improve reliability by adapting power levels based on actual channel conditions and reception status.
2Reliability
If repetition level ramping is implemented for multiple PRACH transmissions, then detection reliability is improved, but power allocation complexity increases
Solution Approach 1:
The patent changes the power allocation parameter structure by introducing a power offset parameter that is applied selectively to PRACH repetitions. Instead of complex per-repetition power calculations, the system uses a simplified parameter-based approach where a power offset is configured and applied based on transmission index and RAR reception status, reducing power allocation complexity while maintaining detection reliability.
Solution Approach 2:
The patent applies different power allocation strategies to different PRACH repetitions based on their local context (transmission index, RAR reception status). Each repetition receives appropriate power levels tailored to its specific situation rather than using a uniform complex allocation scheme, simplifying the overall power management while improving detection reliability.
3Reliability
If multiple PRACH transmissions with power control are implemented, then initial access reliability is improved, but energy consumption increases
Solution Approach 1:
The patent implements partial power control where not all PRACH repetitions are transmitted at maximum power. Instead, the UE adjusts power levels based on whether RAR is received, transmitting at higher power only when necessary (when previous transmissions were not acknowledged). This partial action approach maintains initial access reliability while reducing overall energy consumption compared to always transmitting at maximum power.
Solution Approach 2:
The patent creates a dynamic power consumption profile where the UE adjusts transmit power based on real-time feedback from RAR reception. The power consumption is dynamic rather than static, allowing the UE to conserve energy when access is successful while ensuring reliability when transmissions need to be repeated, optimizing the balance between reliability and energy usage.
Data Source
AI summary
An apparatus and system are described for power control transmission for multiple physical random access channel (PRACH) transmissions. The systems include repetition level ramping for the PRACH transmissions, as well as power control mechanisms for PRACH transmissions that use identical transmission (Tx) beams and that use different Tx beams. The number of repetition attempts for a PRACH transmission increases when a random access response (RAR) is not received or does not pass contention resolution for a maximum number of attempts. A PRACH transmission within one or more transmission occasions is cancelled if the power exceeds a maximum power for PRACH transmissions.