Pseudo TTI for Autonomous HARQ Retransmissions
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Solution Overview
Problem
The existing synchronous HARQ protocol for E-DCH in HSUPA systems does not support autonomous retransmissions efficiently, leading to reduced data rates and increased latency due to fixed transmission time intervals and asynchronous feedback signaling challenges.
Innovation Solution
The introduction of a pseudo transmission time interval (TTI) that combines two consecutive conventional TTIs for data transmission and retransmission, allowing for flexible TTI lengths while maintaining synchronousity and current channel structure, enabling autonomous retransmissions without significant modifications to standards or ACK/NACK feedback signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fixed transmission time intervals are used in synchronous HARQ protocol, then system stability and synchronousity are maintained, but data rates are reduced and latency increases
Solution Approach 1:
The patent applies dynamics by making the TTI length adjustable rather than fixed. The system can dynamically select between conventional TTI length and extended pseudo TTI length based on channel conditions and service requirements, allowing the transmission system to adapt between stability (short TTI) and productivity (long TTI) as needed.
Solution Approach 2:
The patent changes the parameter of TTI length from a fixed value to a variable parameter. By introducing pseudo TTIs with extended length (multiple times the conventional TTI), the system can adjust the transmission time interval parameter to optimize both data rate and latency while maintaining synchronous operation through coordinated scheduling.
2Stability of the object's composition
If conventional TTI length is used, then synchronous HARQ operation is maintained, but coverage is limited
Solution Approach 1:
The patent merges multiple conventional TTIs into a single extended pseudo TTI for uplink transmission. By combining the resources and time slots of multiple consecutive TTIs into one pseudo TTI, the system achieves extended coverage while maintaining synchronous HARQ operation through coordinated scheduling and acknowledgment timing.
3Loss of time
If autonomous retransmissions are implemented, then latency is reduced, but feedback signaling complexity increases
Solution Approach 1:
The patent applies preliminary action by enabling the UE to autonomously perform retransmissions without waiting for explicit feedback in certain cases. The UE can determine based on pre-configured rules and channel conditions when to perform autonomous retransmissions, reducing latency while the network maintains simplified feedback signaling through coordinated acknowledgment timing.
4Area of stationary object
If extended TTI length is used, then coverage is enhanced, but system complexity increases
Solution Approach 1:
The patent achieves universality by making the system capable of operating with both conventional TTI length and extended pseudo TTI length using the same synchronous HARQ protocol framework. The system can selectively apply different TTI lengths based on service requirements, maintaining compatibility with existing protocols while providing extended coverage capabilities when needed.
Data Source
AI summary
A user equipment unit (30) and a base station node (28) which is configured for operation with a synchronous HARQ protocol and with capability of sending data on an E-DCH channel either (1) in a nominal mode in single transmission time intervals of a predetermined length, or (2) in an extended mode in a pseudo transmission time interval. The pseudo transmission time interval comprises a first transmission time interval in which the data is transmitted and a second transmission time interval in which the data is re-transmitted. The second transmission time interval is consecutive to the first transmission time interval, and the first transmission time interval and the second transmission time interval are each of the (same) predetermined length.