HARQ Buffer Management via Timer and Retransmission Counter
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Solution Overview
Problem
Hybrid Automatic Repeat ReQuest (HARQ) systems face issues such as 'twice-toggling' and 'buffer overflow' due to inadequate timing mechanisms, leading to incorrect soft combining and degraded performance in wireless communication networks.
Innovation Solution
Implementing a wait transmission timer (WAIT_TX_CNT) and retransmission counter (RE_TX_CNT) in the receiver, along with a novel Retransmission Interval (RI) value, to manage retransmissions and prevent buffer overflow by negotiating parameters like Predetermined Retransmission Delay (PRD) and Maximal Retransmission Count (MAX_RE_CNT) with the transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timer mechanism is used to manage retransmissions in HARQ systems, then the system can maintain retransmission timing, but it may cause buffer overflow and twice-toggling errors due to inadequate timing control
Solution Approach 1:
The patent segments the timing control into two distinct components: a timer (WAIT_TX_CNT) that tracks elapsed time since the last transmission, and a counter (RE_TX_CNT) that counts the number of retransmission attempts. This segmentation allows independent management of time-based and attempt-based control, preventing the buffer overflow and twice-toggling errors that occur with unified or inadequate timing mechanisms.
Solution Approach 2:
The patent implements preliminary actions by establishing maximum retransmission count (MAX_RE_CNT) and maximum time interval (MAX_INTVL) parameters before the HARQ process begins. These pre-negotiated parameters set upfront constraints that prevent buffer overflow by limiting both the number of retransmissions and the time window for retransmission attempts, thereby avoiding the need for complex runtime decisions.
2Measurement precision
If the receiver waits for retransmissions indefinitely, then data recovery accuracy improves, but system productivity decreases due to buffer overflow and resource wastage
Solution Approach 1:
The patent introduces dynamic control by having the receiver actively monitor both the elapsed time (via WAIT_TX_CNT timer) and the number of retransmission attempts (via RE_TX_CNT counter). The system dynamically adjusts its waiting behavior by comparing current timer and counter values against the pre-established MAX_INTVL and MAX_RE_CNT parameters, respectively. This dynamic monitoring enables the receiver to stop waiting and flush the buffer when either threshold is exceeded, preventing indefinite waiting and buffer overflow while maintaining decoding accuracy within reasonable limits.
Solution Approach 2:
The patent implements feedback mechanisms where the receiver continuously monitors the timer and counter states and compares them against the maximum thresholds. This feedback loop provides real-time information about the retransmission status, enabling the system to make informed decisions about whether to continue waiting for retransmissions or to abandon the current data packet and flush the buffer, thereby balancing decoding accuracy with system throughput.
3Reliability
If the receiver uses soft combining without proper timing control, then error correction capability improves, but buffer management fails leading to overflow and performance degradation
Solution Approach 1:
The patent applies preliminary action by pre-negotiating and establishing the maximum retransmission count (MAX_RE_CNT) and maximum time interval (MAX_INTVL) parameters before the HARQ process begins. These pre-set constraints create upfront boundaries for buffer usage, ensuring that the soft combining buffer does not overflow by limiting both the number of retransmission attempts and the time window for accumulating retransmissions.
Solution Approach 2:
The patent implements dynamic buffer management by continuously monitoring the elapsed time (via WAIT_TX_CNT) and retransmission count (via RE_TX_CNT) against the pre-established maximum thresholds. When either the timer exceeds MAX_INTVL or the counter exceeds MAX_RE_CNT, the system dynamically flushes the soft combining buffer, preventing overflow while allowing sufficient time and attempts for error correction through soft combining under normal operating conditions.
Data Source
AI summary
In a Hybrid Automatic Repeat ReQuest (HARQ) communication system, a receiver receives from a transmitter a HARQ sub-burst. A retransmission counter (RE_TX_CNT) in the receiver is incremented if either: (i) the receiver cannot decode the sub-burst, or (ii) no retransmission of the sub-burst is received within a Predetermined Retransmission Delay (PRD) interval. If RE_TX_CNT reaches a Maximal Retransmission Count (MAX_RE_CNT), then information for the sub-burst that was previously stored for HARQ purposes in a soft combining buffer in the receiver is flushed. Parameters that set the PRD interval and the MAX_RE_CNT value are pre-negotiated between the transmitter and the receiver. In another embodiment, if a novel timer in the receiver indicates that a first threshold time has elapsed after receipt of an undecodable HARQ transmission then buffered information is marked, whereas if the timer indicates that a second threshold time has elapsed then the marked information is flushed.