Uplink Power Control for Low Latency Wireless
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Solution Overview
Problem
In wireless communication systems, particularly in LTE networks, low-latency uplink power control is challenging due to the need for coordinated power management across different transmission time intervals (TTIs) to ensure reliable communication links without exceeding maximum transmit power thresholds, especially when combining low-latency and non-low-latency transmissions.
Innovation Solution
A method where user equipment (UE) determines separate uplink transmit power limitations for multiple TTI durations based on distinct power control parameters, applies adjustment factors or power backoffs, and uses demodulation reference signal (DMRS) windows for power control, allowing for coordinated power management across different TTI durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate power control parameters are used for different TTI durations, then power control accuracy is improved, but device complexity increases
Solution Approach 1:
The patent divides power control parameters into separate sets for different TTI durations (first TTI duration and second TTI duration). The UE determines first uplink power limitation for the first TTI duration based on first power control parameters, and second uplink power limitation for the second TTI duration based on second power control parameters. This segmentation allows accurate power control for each TTI type while managing complexity through structured separation.
Solution Approach 2:
The patent changes power control parameters based on TTI duration characteristics. Different power control parameters (Po, alpha, pathloss reference) are configured for different TTI durations to account for the different timing and power requirements. This parameter adaptation enables accurate power control without requiring completely separate control mechanisms.
2Reliability
If power control is coordinated across different TTI durations, then transmission reliability is improved, but latency increases
Solution Approach 1:
The patent applies power control adjustments in advance at the beginning of each TTI duration based on power headroom parameters calculated from previous transmissions. The UE determines power limitations and applies adjustment factors before actual data transmission, ensuring reliable power levels are set without waiting for real-time feedback during the TTI, thus avoiding latency.
Solution Approach 2:
The patent introduces power headroom parameters as an intermediary mechanism to coordinate power control across different TTI durations. The UE reports power headroom to the base station, which then provides TPC commands that mediate the power control adjustments. This intermediary approach enables coordinated power management without requiring direct real-time interaction between different TTI transmissions.
3Object-generated harmful factors
If maximum transmit power threshold is enforced, then interference is reduced, but transmission power flexibility decreases
Solution Approach 1:
The patent implements dynamic power control where the UE adjusts transmit power within the maximum threshold based on real-time power headroom conditions. The power limitation is determined dynamically as the minimum of configured maximum power and calculated power based on path loss, modulation, coding, and closed-loop adjustments. This dynamic approach reduces interference when power headroom is low while maintaining flexibility to use higher powers when conditions allow.
Solution Approach 2:
The patent uses feedback mechanisms where the UE reports power headroom parameters to the base station, which then provides TPC (Transmit Power Control) commands. This feedback loop enables the system to enforce maximum power thresholds to prevent interference while maintaining transmission flexibility through adaptive adjustments based on actual channel conditions and power availability.
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. A user equipment (UE) may determine separate uplink (UL) power limitations for multiple transmission time interval (TTI) durations based on distinct power control parameters. In some cases, an adjustment factor or a power backoff may be applied to communications using one TTI duration to ensure that total transmit power does not exceed a threshold. The UE and the serving base station may also identify one or more demodulation reference signal (DMRS) windows. UL data transmissions may be demodulated based on a DMRS sent during the same window. Transmit power control (TPC) commands may be applied at the beginning of each window. However, if an UL transmission is scheduled at the beginning of the window, the UE may wait until a DMRS transmission or until no more transmissions are scheduled for the window before applying the TPC adjustment.