Short PDCCH Scheduling for Low-Latency LTE Resource Allocation
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Solution Overview
Problem
Current LTE systems face challenges in reducing latency and managing control overhead due to the fixed 1 ms Transmission Time Interval (TTI), which limits efficient data transmission and increases processing complexity.
Innovation Solution
Implementing shorter minimum TTIs (sTTIs) and optimizing sPDCCH operation by using multi-sTTI scheduling, hierarchical control information transmission, and reducing DCI bit fields, along with efficient resource allocation and DMRS-based channel estimation to minimize latency and control overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If 1 ms TTI is used for dynamic scheduling, then resource allocation is simplified, but latency is increased and productivity is reduced
Solution Approach 1:
The patent segments the 1 ms TTI into shorter time intervals (e.g., 2-symbol TTI, 1-symbol TTI) to enable faster scheduling and reduce latency. This segmentation allows multiple scheduling opportunities within a single subframe, improving responsiveness while maintaining manageable complexity through structured resource allocation.
2Reliability
If control region size is increased to accommodate more sPDCCH candidates, then reliability is improved, but resource availability for data transmission is reduced
Solution Approach 1:
The patent distributes sPDCCH candidates across multiple frequency resources (PRB pairs) and time symbols, transforming the control channel allocation from a single-dimension problem to a multi-dimensional resource allocation problem. This allows sufficient control coverage without excessively expanding the control region in any single dimension, preserving data transmission resources.
3Productivity
If DCI bit fields are reduced for short TTI scheduling, then overhead is reduced and productivity is improved, but information completeness may be compromised
Solution Approach 1:
The patent extracts and separates control information into different layers: essential scheduling parameters are conveyed through compact DCI formats for short TTI, while additional configuration parameters are transmitted through higher-layer signaling (RRC). This extraction allows the physical layer DCI to remain brief and efficient while ensuring complete control information is available through multiple channels.
4Adaptability or versatility
If sPDCCH monitoring candidates are increased to improve scheduling flexibility, then adaptability is improved, but device complexity and processing requirements increase
Solution Approach 1:
The patent implements a two-stage monitoring approach where UEs first monitor a reduced set of sPDCCH candidates in the initial symbols for urgent scheduling decisions, then optionally monitor additional candidates in later symbols for less time-critical allocations. This partial monitoring strategy provides sufficient scheduling flexibility for most scenarios while limiting the maximum processing burden on UEs.
Data Source
AI summary
A set of information can be transmitted via a physical downlink control channel (PDCCH). First information of the set of information can schedule at least one transmission on a physical downlink shared channel (PDSCH) and during at least one slot. Second information of the set of information can indicate at least one orthogonal frequency division multiplexing (OFDM) symbol during the at least one slot and a set of frequency resources associated with the at least one OFDM symbol. The at least one transmission can be transmitted on the PDSCH. The at least one transmission on the PDSCH can be rate-matched around the set of frequency resources.