5G Uplink Scheduling Across Multiple Downlink Slots
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Solution Overview
Problem
In 5G networks, the PDCCH channel faces challenges in efficiently scheduling a large number of UEs in both downlink (DL) and uplink (UL) directions, leading to increased resource allocation for control channels, which reduces spectral efficiency and requires additional symbols, thereby affecting DL throughput.
Innovation Solution
A scheduler is implemented that uses multiple time domain allocation values (e.g., K2) to spread scheduling across multiple DL slots for a given UL slot in TDD systems, optimizing PDCCH usage by allocating CCEs in a manner that reduces the need for extra symbols, thereby maximizing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If scheduling is concentrated in a single DL slot, then control channel allocation is simple, but spectral efficiency decreases and additional PDCCH symbols are required
Solution Approach 1:
The scheduling process is divided into multiple stages across different DL slots. The UL grant is scheduled in an early DL slot, while the corresponding PDSCH transmission occurs in a later DL slot. This segmentation allows control channel resources to be distributed over time, reducing the need for concentrated PDCCH symbols in a single slot and thereby improving spectral efficiency.
Solution Approach 2:
The patent introduces a time dimension to the scheduling process by utilizing multiple DL slots separated by a time gap (K2). Instead of scheduling all control information in one slot, the system spreads scheduling across the time dimension, allowing UEs to process UL grants with sufficient time while reducing instantaneous control channel resource requirements.
2Quantity of substance
If more PDCCH symbols are allocated, then more UEs can be scheduled, but DL throughput decreases due to reduced data resources
Solution Approach 1:
The scheduling of multiple UEs is segmented across different DL slots rather than concentrating all UE scheduling in a single slot. By distributing UL grants to different UEs across multiple slots with appropriate time gaps, the system can support a large number of UEs without requiring excessive PDCCH symbols in any single slot, thus preserving resources for PDSCH and maintaining DL throughput.
Solution Approach 2:
The system dynamically adjusts the time gap (K2) between UL grant and PUSCH transmission based on UE processing capabilities and traffic conditions. This dynamic adjustment allows flexible resource allocation, enabling the system to schedule more UEs when time gaps are optimized without permanently sacrificing DL throughput, as resources can be reallocated based on instantaneous network conditions.
3Measurement precision
If scheduling is done 6 TTI in advance, then UL scheduling accuracy improves, but control channel resource utilization becomes challenging
Solution Approach 1:
The UL grant is scheduled in advance in an early DL slot, giving the UE sufficient time to prepare for PUSCH transmission. This preliminary scheduling action improves UL scheduling accuracy by allowing proper timing alignment and buffer preparation. The system manages control channel resource utilization by distributing these early scheduling decisions across multiple DL slots, preventing resource exhaustion in any single slot.
Data Source
AI summary
In a first embodiment, a method is disclosed for providing uplink scheduling in a cellular radio base station, comprising: an uplink (UL) scheduler running 6 TTI in advance to thereby provide a list of all Radio Network Temporary Identifiers (RNTIs) to be scheduled on a given UL slot; allocating, at a PDCCH resource allocator, control channel elements (CCEs) for all downlink (DL) RNTIs first; allocating, at the PDCCH resource allocator, CCEs for at least one UL RNTI for a first DL slot; placing RNTIs not allocated in the first DL slot in a pending queue.