NOMA Power Control via Path Loss Estimation
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Solution Overview
Problem
Current wireless communication systems, particularly those using non-orthogonal multiple access (NOMA), face challenges in accurately determining transmit power for user equipment (UE) due to variations in downlink and uplink path loss values, leading to potential transmission failures and increased inter-cell interference.
Innovation Solution
The method involves determining downlink and uplink path loss values, using these values along with configuration information to set transmit power for data or control transmissions, and employing a grant-free transmission approach with a fallback to grant-based retransmissions when necessary, thereby improving power control reliability and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional power control methods are used in NOMA systems, then device complexity is reduced, but transmission reliability deteriorates due to inaccurate transmit power determination
Solution Approach 1:
The base station performs preliminary path loss estimation and determines appropriate transmit power values before the actual data transmission. The base station calculates path loss based on received signal strength indication (RSSI) measurements from uplink transmissions, then uses these pre-calculated path loss values to determine transmit power for subsequent downlink transmissions, avoiding the need for complex real-time power control negotiations
Solution Approach 2:
The patent introduces path loss estimation as an intermediary mechanism between the base station and user equipment for power control. Instead of direct complex power control signaling, the base station uses path loss values (derived from RSSI measurements) as an intermediate parameter to determine transmit power, simplifying the overall control mechanism while improving reliability
2Reliability
If transmit power is increased to overcome path loss variations, then transmission reliability improves, but inter-cell interference increases
Solution Approach 1:
The base station uses feedback from uplink transmissions (specifically RSSI measurements from user equipment) to estimate downlink path loss values. This feedback mechanism allows the base station to adapt transmit power to actual channel conditions, ensuring reliable transmission without excessive power increases that would cause inter-cell interference
Solution Approach 2:
The patent changes the parameter used for power control from fixed or conservatively estimated values to dynamically determined path loss values based on actual RSSI measurements. This parameter change enables precise transmit power setting that matches actual channel conditions, improving reliability while avoiding unnecessary power increases that would generate interference
3Object-generated harmful factors
If conservative power control settings are used, then inter-cell interference is reduced, but spectral efficiency deteriorates due to transmission failures
Solution Approach 1:
The base station performs preliminary path loss estimation and transmit power determination before data transmission, allowing it to set optimal power levels that maximize spectral efficiency without causing excessive interference. This pre-calculation based on actual RSSI measurements eliminates the need for conservative power settings that would reduce throughput
4Measurement precision
If path loss estimation accuracy is improved, then transmit power determination accuracy improves, but measurement precision requirements increase
Solution Approach 1:
The system uses self-service measurement where the user equipment's own uplink transmission signals are used for path loss estimation. The base station measures RSSI of the uplink signal transmitted by the UE, and uses this measurement to estimate the downlink path loss. This self-service approach leverages existing signals rather than requiring separate dedicated measurement signals, reducing measurement complexity while maintaining accuracy
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may determine at least one of a downlink path loss value or an uplink path loss value associated with a base station; receive system information, a semi-persistently configured grant via RRC or a dynamic uplink grant via DCI from the base station, wherein the RRC signaling or the dynamic uplink grant identifies a power control value associated with one user or a plurality of users associated with the base station; and determine a transmit power for a data or control transmission based at least in part on at least one of the downlink path loss value or the uplink path loss value and the power control value. Numerous other aspects are provided.