Stateful Stop-and-Wait HARQ Protocol for Reliable Packet Delivery
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Solution Overview
Problem
The current LTE HARQ protocol in wireless communication systems fails to guarantee reliable delivery of upper layer packets due to channel impairments causing incorrect ACK/NACK interpretations, leading to lost data bits and increased latency, necessitating additional ARQ mechanisms in upper layers that introduce unnecessary overhead and delays.
Innovation Solution
A stateful stop-and-wait hybrid automatic repeat request protocol using state variables and incremental redundancy versions of frames, along with acknowledgment timers, to ensure reliable and in-sequence delivery of upper layer packets by accurately distinguishing between successful and unsuccessful frame decoding, thereby eliminating the need for secondary ARQ in upper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single-bit ACK/NACK is used in HARQ protocol, then spectral efficiency is improved, but reliability of packet delivery deteriorates due to incorrect interpretations caused by channel impairments
Solution Approach 1:
The patent introduces state variables as intermediary elements that mediate between the single-bit ACK/NACK signaling and the transmission decisions. These state variables track the decoding status and provide context interpretation, allowing the system to maintain spectral efficiency while improving reliability by preventing incorrect interpretations of ACK/NACK bits under channel impairments
Solution Approach 2:
The patent implements a feedback mechanism using state variables that maintain information about previous transmissions and decoding outcomes. This feedback loop allows the transmitter to make informed decisions based on the receiver's state, ensuring reliable packet delivery while maintaining the spectral efficiency benefits of single-bit signaling
2Reliability
If two-layer ARQ approach (MAC HARQ + RLC ARQ) is used, then reliability of upper layer packet delivery is improved, but signaling overhead and latency increase
Solution Approach 1:
The patent merges the functions of MAC HARQ and RLC ARQ into a unified stateful HARQ protocol at the MAC layer. By combining the reliability mechanisms of both layers into a single layer with enhanced state tracking, the patent eliminates the need for separate RLC ARQ processing, thereby reducing signaling overhead and latency while maintaining delivery reliability
Solution Approach 2:
The patent creates a universal HARQ protocol that performs both the error correction function of MAC HARQ and the reliability guarantee function of RLC ARQ. The stateful mechanism provides multi-functionality, handling both incremental redundancy and reliable in-sequence delivery within a single protocol framework, eliminating the need for separate upper layer ARQ mechanisms
3Speed
If transmitter moves on to next TB upon receiving ACK, then transmission speed is improved, but data loss occurs when ACK is incorrectly interpreted due to channel impairments
Solution Approach 1:
The patent applies preliminary action by maintaining state variables that track the expected ACK/NACK sequence before actual transmission decisions are made. The transmitter prepares by knowing what ACK pattern to expect based on previous NACKs and retransmissions, allowing it to verify received ACKs against expected patterns and prevent premature progression to next TB when channel impairments cause incorrect interpretations
Solution Approach 2:
The patent uses feedback through state variables that continuously monitor the transmission-reception-transmission cycle. The state machine provides feedback about the current transmission status and expected outcomes, allowing the transmitter to adjust its behavior based on the actual reception state, thereby preventing data loss while maintaining transmission speed
Data Source
AI summary
A method for transferring data in a communication system is implemented in a network device. In the method, the network device receives an IR version of a frame, a sequence number, and a revision number in a media access control (MAC) layer. The network device determines whether the received frame can be decoded and acknowledged based on the received sequence number and revision number. The network device sets state variables VS,R equal to 1−VS,R and VRV,R equal to −1 if the frame is decoded.