Uplink Power Scaling Avoidance in UMTS UE
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Solution Overview
Problem
In UMTS networks, power scaling during uplink transmission can lead to unreliable decoding of HS-DPCCH data, resulting in sub-optimal radio resource usage and degraded data throughput, especially when HARQ ACK is decoded as DTX or NAK is decoded as ACK, causing duplicate data transmission and discarding of previous TTI data.
Innovation Solution
A method to avoid power scaling by configuring the UE to forgo building uplink data in upcoming frames when HARQ feedback information is present, and selectively boosting the transmit power of NACK messages to ensure reliable communication, thereby maintaining optimal radio resource utilization and data throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If power scaling is applied when total transmit power exceeds maximum allowed value, then the minimum sets of TFC/E-TFC data and HS-DPCCH transmission are supported, but the HS-DPCCH data decoding reliability deteriorates
Solution Approach 1:
The UE determines in advance whether uplink data should be forgone by checking if HARQ feedback information is present in the upcoming frame before power scaling is applied. This preliminary determination prevents the power scaling that would otherwise degrade HS-DPCCH decoding reliability, while still allowing the system to support minimum sets of TFC/E-TFC data through alternative power management.
Solution Approach 2:
The system dynamically adjusts the uplink data transmission decision based on the presence of HARQ feedback information. When HARQ feedback is detected, the UE dynamically forgoes uplink data in that frame to prioritize HS-DPCCH reliability. This dynamic adaptation allows the system to maintain reliability when needed while preserving adaptability for normal operation.
2Power
If power scaling is applied to support minimum sets of TFC/E-TFC data, then transmit power is reduced to maximum allowed value, but radio resource usage becomes sub-optimal
Solution Approach 1:
The system performs a preliminary check for HARQ feedback information before applying power scaling. This advance determination allows the UE to avoid power scaling in frames where uplink data would otherwise be transmitted, thereby maintaining optimal radio resource usage while still managing transmit power within acceptable limits.
Solution Approach 2:
The system uses HARQ feedback information as a trigger condition for forgoing uplink data. This feedback mechanism allows the UE to intelligently decide when to prioritize HS-DPCCH transmission over uplink data, optimizing radio resource usage based on actual channel conditions and network requirements.
3Power
If power scaling is applied during uplink transmission, then total transmit power is controlled, but data throughput is degraded
Solution Approach 1:
The UE determines in advance whether to forgo uplink data by detecting HARQ feedback information in the upcoming frame. This preliminary action prevents power scaling from being applied, thereby maintaining data throughput at optimal levels while still achieving transmit power control through selective data forgoing rather than uniform power reduction.
Solution Approach 2:
The system dynamically switches between normal uplink data transmission and forgoing uplink data based on the presence of HARQ feedback. This dynamic behavior allows the system to maintain high data throughput during normal operation while selectively reducing uplink data transmission only when necessary to protect HS-DPCCH reliability, thus achieving both power control and throughput optimization.
4Power
If HARQ ACK is decoded as DTX or NAK is decoded as ACK due to power scaling, then transmit power is reduced, but call retention deteriorates
Solution Approach 1:
The system performs advance detection of HARQ feedback information to determine whether uplink data should be forgone. This preliminary action prevents power scaling that would cause decoding errors, thereby maintaining call retention while still achieving transmit power reduction through selective data forgoing rather than blanket power reduction.
Solution Approach 2:
The system uses HARQ feedback information as a critical trigger for preventing power scaling. This feedback mechanism ensures that when HARQ feedback is present, the UE prioritizes reliable transmission by forgoing uplink data, thus preventing the decoding errors (ACK decoded as DTX or NAK decoded as ACK) that would degrade call retention.
Data Source
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AI summary
Methods and apparatus for avoiding power scaling and controlling transmit power in uplink data transmission are provided. If a user equipment (UE) would be transmit-power limited when transmitting data concurrently on an uplink high speed dedicated physical control channel (HS-DPCCH) and an uplink data channel, the UE may forgo building data for transmission on the uplink data channel to avoid power scaling. If the UE would be transmit-power limited when transmitting data concurrently on an HS-DPCCH and a dedicated physical control channel (DPCCH), the UE may reduce the transmission power of a portion of the data transmitted on the DPCCH to avoid power scaling. The UE may also boost transmission power of a negative acknowledge transmission above network-specified power level.