Dynamic H-ARQ Process Management for Wireless Data Transmission
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Solution Overview
Problem
3rd generation cellular systems face challenges in achieving low transmission latency and efficient use of physical resources for data transfer due to limitations in adaptive modulation and coding (AM&C) and hybrid-automatic repeat request (H-ARQ) schemes, particularly in handling retransmissions and resource allocation.
Innovation Solution
The system dynamically adjusts data transmission parameters such as modulation and coding scheme (MCS) and transport block set (TBS) size, and assigns and releases an H-ARQ process based on feedback, allowing for efficient retransmissions and resource management through an enhanced uplink (EU) dedicated channel, with features like Chase Combining (CC) and incremental redundancy (IR) for error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a more robust MCS is used for retransmission, then error protection is improved, but physical resource consumption increases
Solution Approach 1:
The patent implements dynamic MCS selection for retransmissions based on channel conditions and transmission history. Instead of using a fixed robust MCS for all retransmissions, the system adaptively adjusts the MCS level to match current channel quality, thereby maintaining error protection while optimizing resource usage. This is achieved through feedback mechanisms that monitor transmission success and channel state, allowing the MCS to be dynamically adjusted upward when conditions improve or downward when resources are constrained.
Solution Approach 2:
The system changes the MCS parameter dynamically based on transmission outcomes and channel conditions. For retransmissions, the MCS is adjusted according to the number of previous transmission attempts, channel quality indicators, and resource availability. This parameter adaptation allows the system to transition from conservative robust MCS in poor conditions to more efficient MCS when channel quality improves, resolving the contradiction between reliability and resource consumption.
2Reliability
If H-ARQ processes are maintained for all retransmissions, then transmission reliability is improved, but system complexity increases
Solution Approach 1:
The patent implements a mechanism to discard H-ARQ processes when maximum retransmission attempts are reached without successful delivery. Instead of indefinitely maintaining H-ARQ processes for all data, the system recovers resources by releasing processes that have exhausted their retransmission budget. This discarding and recovering approach maintains reliability for transmissions that can be successfully delivered while reducing system complexity by eliminating stale or hopeless transmission states.
Solution Approach 2:
The system applies H-ARQ processes partially - not to all possible transmissions indefinitely, but only to a limited number of retransmission attempts. By setting a maximum retransmission count, the system performs H-ARQ actions partially rather than excessively, thereby maintaining reliability within practical limits while avoiding the complexity of unlimited process maintenance. This partial application of H-ARQ resolves the contradiction by balancing reliability needs against system complexity constraints.
3Productivity
If dynamic parameter adjustment is implemented, then data transfer efficiency is improved, but control complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the system monitors transmission outcomes, channel conditions, and resource usage to dynamically adjust parameters such as MCS and TBS size. The feedback loop includes receiving acknowledgments (ACK/NACK) from the receiver, evaluating channel quality indicators, and using this information to adaptively select optimal transmission parameters for subsequent transmissions. This feedback-driven approach improves data transfer efficiency while keeping control complexity manageable through rule-based decision logic.
Solution Approach 2:
The system performs preliminary actions by pre-defining parameter adjustment rules and thresholds before actual transmissions occur. Lookup tables, pre-calculated MCS mappings, and predetermined adjustment strategies are established in advance, allowing the system to quickly adapt parameters during transmission without complex real-time calculations. This preliminary preparation reduces control complexity while maintaining the benefits of dynamic parameter adjustment for improving data transfer efficiency.
Data Source
AI summary
In a wireless communication system including a wireless transmit/receive unit (WTRU) which transfers data to a Node-B, data transmission parameters such as modulation and coding scheme (MCS) and transport block set (TBS) size are dynamically adjusted on a transmission time interval (TTI) basis, and hybrid-automatic repeat request (H-ARQ) processes used to control the transfer of data between the WTRU and the Node-B are initiated and released, as required. The WTRU transmits and retransmits data to the Node-B through an enhanced uplink (EU) dedicated channel (E-DCH) in accordance with data feedback information received from the Node-B. The WTRU queues data for transmission, and determines a transmission status of the data. The transmission status is set to one of “new transmission,”“successful transmission,”“retransmission” and “restarted transmission.” For each TTI, the WTRU initiates an EU transmission to the Node-B which identifies the assigned H-ARQ process, TBS size and MCS.