Uplink ACK/NACK Codebook Sizing During Carrier Activation
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Solution Overview
Problem
Existing UL ACK/NAK feedback mechanisms in LTE-Advanced systems face challenges during timing uncertainty periods related to component carrier re-configuration, activation, or de-activation, leading to ambiguity in ACK/NAK codebook size and increased probability of higher layer errors due to misalignment between eNB and UE.
Innovation Solution
The proposed solution involves an apparatus and method that detect the signaling format used for ACK/NAK messages on the uplink control channel, deciding the codebook size based on the detected format, and applying it for reliable feedback, including using PUCCH channel selection or joint coding, to ensure accurate ACK/NAK signaling even during component carrier re-configuration or activation/de-activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If component carrier re-configuration, activation, or de-activation is performed, then system adaptability and bandwidth flexibility are improved, but timing uncertainty and ACK/NAK feedback reliability deteriorate
Solution Approach 1:
The invention applies preliminary action by having the UE transmit an ACK/NAK message in the uplink subframe immediately before the re-configuration, activation, or de-activation takes effect. This timing allows the eNB to receive feedback about downlink transmissions before the component carrier configuration changes, ensuring reliable ACK/NAK delivery without being affected by the timing uncertainty that occurs during re-configuration periods.
2Device complexity
If existing UL ACK/NAK feedback mechanisms are used during re-configuration period, then device complexity remains low, but error probability increases due to codebook size ambiguity
Solution Approach 1:
The invention resolves the codebook size ambiguity problem by transmitting ACK/NAK feedback in the uplink subframe immediately preceding the re-configuration, activation, or de-activation. At this timing, the component carrier configuration is still stable and both UE and eNB agree on the codebook size, eliminating the ambiguity that would otherwise occur during the re-configuration period while maintaining simple feedback mechanisms.
3Stability of the object's composition
If ACK/NAK feedback is delayed until after re-configuration, then timing alignment is improved, but feedback latency increases
Solution Approach 1:
The invention optimizes the balance between timing alignment and feedback latency by transmitting ACK/NAK in the uplink subframe immediately before re-configuration, activation, or de-activation. This timing ensures that the configuration is stable and agreed upon by both UE and eNB, providing timing alignment, while minimizing the delay since the feedback is sent as soon as possible after the downlink transmission, thus reducing feedback latency compared to waiting until after re-configuration completes.
Data Source
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AI summary
An apparatus and a method is described, by which a component carrier configuration, re-configuration, activation or de-activation is performed. In particular, a signaling format used for acknowledgment/negative acknowledgement messages on an uplink control channel is detected, and a codebook size of the acknowledgment/negative acknowledgement messages is decided based on the detected signaling format.