PDCP PDU Set Coding for Reliable Cell-Free Packet Delivery
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently processing PDU sets at the PDCP layer, particularly in cell-free networks, where ensuring reliable delivery of packets within a PDU set is crucial for real-time applications like extended reality and media services.
Innovation Solution
The implementation of a timer-based discard operation at the PDCP layer for uplink service data units (SDUs)/PDUs, which affects all PDUs of a same PDU set, along with the use of Reed-Solomon erasure coding for error correction, and adaptive packet coding rates, segmentation schemes, and routing policies to optimize PDU set processing in cell-free networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PDCP layer processing is used without timer-based discard operation, then packet delivery attempts continue indefinitely, but resource consumption increases and reliability does not improve
Solution Approach 1:
The patent applies preliminary action by implementing a timer-based discard operation that proactively discards PDUs before they can be retransmitted indefinitely. The timer is started when a PDU is received or generated, and if the PDU is not acknowledged within the timer period, it is automatically discarded. This prevents wasted retransmission resources while maintaining reliable delivery through forward error correction codes applied to PDU sets.
2Reliability
If forward error correction codes are applied to individual PDUs, then error correction capability is provided, but overhead and processing complexity increase significantly
Solution Approach 1:
The patent merges the error correction function from the PDCP layer with the PDU set handling mechanism. Instead of applying forward error correction codes to individual PDUs, the invention applies error correction codes to entire PDU sets, leveraging the existing PDU set structure for efficient error correction. This reduces processing complexity by operating at the PDU set level rather than individual PDU level, while maintaining robust error correction capability.
3Reliability
If PDU set processing is implemented without timer-based discard, then all PDUs are retained for potential retransmission, but buffer memory consumption increases
Solution Approach 1:
The timer-based discard operation performs preliminary action by establishing a time limit for PDU retention. When a PDU enters the buffer, a timer is started, and if the PDU is not successfully delivered or acknowledged before the timer expires, it is automatically discarded. This prevents indefinite buffer occupation while maintaining delivery assurance through the error correction mechanism applied to PDU sets, thus reducing buffer memory consumption.
4Productivity
If adaptive packet coding rates are used, then transmission efficiency is optimized for different channel conditions, but encoding/decoding complexity increases
Solution Approach 1:
The patent implements dynamics by making the packet coding rate adaptive to channel conditions. The system dynamically selects appropriate coding rates based on current channel quality indicators, allowing more robust coding for poor channels and more efficient coding for good channels. This adaptive approach optimizes transmission efficiency while the implementation leverages existing error correction frameworks to manage encoding complexity.
Data Source
AI summary
Packet data convergence protocol (PDCP) layer encoding and decoding procedures for use in cell-free networks are disclosed. A transmitter (e.g., a user equipment (UE) or a cluster of base stations that serves a UE) performs PDCP processing using a PDCP entity by: generating a concatenated service data unit (SDU) set by concatenating a plurality of SDUs for a protocol data unit (PDU) set; segmenting the concatenated SDU set into one or more systematic PDUs of the PDU set; performing an encoding with the one or more systematic PDUs to generate one or more redundant PDUs of the PDU set; and distributing the one or more systematic PDUs and the one or more redundant PDUs across one or more radio link control (RLC) entities for transmission. Complimentary processes performed by a PDCP entity of a receiver (e.g., a cluster of base stations or a UE) are also disclosed.