RLC MAC PDU Pre-construction for 5G Layer Processing Latency
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Solution Overview
Problem
The current LTE protocol architecture faces challenges in reducing processing latency and overhead due to real-time processing requirements for segmentation, concatenation, and multiplexing, which limits the efficiency of layer processing, especially in high-data-rate scenarios like those targeted by 5G mobile communication systems.
Innovation Solution
Moving the concatenation/segmentation functionality from the RLC layer to the MAC entity allows for pre-construction of RLC and MAC PDUs before receiving an UL grant, reducing processing time and overhead by enabling pre-processing of data, and using common sequence numbers to reduce header overhead across layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If segmentation and concatenation are performed in real-time at the RLC layer after receiving UL grant, then processing accuracy is maintained, but processing latency increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by performing segmentation and concatenation operations before the UL grant is received. The RLC layer pre-processes data by segmenting PDCP PDUs into RLC PDUs and concatenating them into MAC SDUs in advance, so that when the UL grant arrives, the MAC layer can immediately perform multiplexing without waiting for segmentation/concatenation to complete. This reduces processing latency and improves productivity by eliminating the sequential dependency where segmentation/concatenation must complete before multiplexing can begin.
2Loss of information
If separate sequence numbers are used at PDCP and RLC layers, then layer-specific tracking is enabled, but header overhead increases
Solution Approach 1:
The patent applies universality by making the RLC sequence number serve multiple functions across different layers. The RLC sequence number is not only used for RLC layer ordering and reassembly but also serves as the PDCP sequence number for PDCP layer ordering and reassembly. This multi-functional approach eliminates the need for separate sequence number fields at PDCP and RLC layers, reducing header overhead while maintaining the ability to track and order data at both layers through the same sequence number mechanism.
Data Source
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AI summary
The present disclosure relates to layer processing at a receiver and a transmitter in a communication system. The layer processing includes at least processing on a first, a second and a third layer. At the transmitter side, the third layer receives a packet, adds its header and forwards the packet to the second layer. The second layer performs segmentation and provides segmented data to the first layer, which maps the segmented data onto physical resources. The segmentation is based on the allocated resources. Retransmissions may take place on the third layer and thus, the third layer may re-segment the packet according to the received feedback for particular segments and provide the re-segmented data to the lower layers. Alternatively, the feedback information is provided to the second layer which then performs the segmentation by taking it into account. Correspondingly, the receiver performs re-ordering and re-assembly at the third layer for which it receives also control information from the second layer.