ACK/NACK Signal Power Allocation in Wireless Uplink
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Solution Overview
Problem
In wireless communication systems using the enhanced uplink dedicated channel, existing technologies face challenges in efficiently transmitting and determining ACK/NACK signals, particularly due to high transmission power requirements and errors caused by weak link states and soft handover conditions, leading to increased packet transmission delay and potential loss of erroneous packets.
Innovation Solution
The method involves using phase shift key modulation for ACK/NACK signals transmitted by the serving network and amplitude shifting key modulation for signals from non-serving networks, with distinct transmission power settings for ACK and NACK signals to optimize power allocation and ensure reliable communication, especially during soft handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If very high transmission power is used to protect the ACK/NACK signal from interference, then the reliability of ACK/NACK reception is improved, but the power consumption and interference to other channels increases
Solution Approach 1:
The patent changes the modulation parameter from phase shift keying to amplitude shift keying for ACK/NACK transmission. This parameter change allows the system to achieve reliable reception at lower transmission power levels by utilizing amplitude variations that are more robust to phase noise and frequency offsets, thereby resolving the contradiction between reliability and power consumption
Solution Approach 2:
The patent introduces an amplitude-based intermediary representation for ACK/NACK signals. By encoding acknowledgment information in amplitude rather than phase, the system creates an intermediate signal form that is less susceptible to interference and requires lower transmission power to achieve the same reliability level
2Reliability
If the NACK signal transmission power is increased to ensure reliable reception in weak link states, then the reliability of NACK reception is improved, but the overall power allocation efficiency deteriorates
Solution Approach 1:
The patent applies local quality by using amplitude shift keying specifically for ACK/NACK signals while other channels can use different modulation schemes optimized for their requirements. This localized approach allows NACK signals to achieve high reliability in weak link states without forcing all transmissions to use high power, thereby maintaining overall power allocation efficiency
3Reliability
If the UE re-transmits packets upon receiving NACK signals, then the reliability of packet delivery is improved, but the packet transmission delay increases when errors occur
Solution Approach 1:
The patent enhances the feedback mechanism by ensuring more reliable NACK signal reception through amplitude shift keying. This improved feedback reliability reduces the probability of erroneous ACK reception that would prevent necessary re-transmissions, thereby achieving high packet delivery reliability without excessive delays from failed acknowledgment
Data Source
AI summary
Transmitting an acknowledgement/negative acknowledgement (ACK/NACK) signal in association with a packet transmitted on an uplink is disclosed. The method includes the steps of receiving a packet transmitted from a user equipment, decoding the packet, and determining whether the packet has been successfully decoded, transmitting an ACK signal or a NACK signal, based on the decoding result. Different transmission powers are allocated for the ACK signal and the NACK signal. Alternatively, the transmission power for the NACK signal selectively has an OFF level. The present invention optimizes the transmission powers for downlink ACK/NACK signals in accordance with the required reception quality of each of the ACK/NACK signals, and thus, enables the system to operate efficiently.