5G NR PDCCH Search Space Design for Flexible Scheduling
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Solution Overview
Problem
Existing wireless communication systems, particularly 5G NR, face challenges in achieving flexibility and efficiency in the design and implementation of Physical Downlink Control Channels (PDCCH) due to the need to support multiple scheduling entities and varying channel conditions, leading to conflicts and overhead issues.
Innovation Solution
The implementation of multiple common search spaces, control resource blocks (CRBs) with precoded reference signals and data elements, and fast control channel signaling for grant-free uplink, along with irregular resource block granting across slots or mini-slots, addresses these challenges by enhancing scheduling flexibility and reducing collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple common search spaces are implemented to support multiple scheduling entities, then scheduling flexibility and adaptability are improved, but device complexity and overhead increase
Solution Approach 1:
The control channel is divided into multiple common search spaces (CSS0, CSS1, CSS2, CSS3) with different aggregation levels and monitoring configurations. Each CSS is associated with specific scheduling entities and RNTI types, allowing the system to segment control information transmission across multiple organized spaces rather than using a single complex search space.
Solution Approach 2:
The patent introduces multiple dimensions for organizing search spaces including aggregation level (AL0, AL1, AL2, AL3), search space index (0-3), and RNTI type associations. This multi-dimensional organization allows scheduling flexibility to be improved without linearly increasing complexity, as the system can select specific combinations of dimensions rather than managing a flat complex structure.
2Reliability
If control resource blocks with precoded reference signals and data elements are used, then reliability and measurement precision are improved, but use of energy and processing complexity increase
Solution Approach 1:
Reference signals and data elements are combined within the same control resource blocks (CRBs) and precoded using the same precoding. This merging allows the UE to perform channel estimation and decode control information more efficiently by utilizing the reference signals embedded within the data-containing CRBs, reducing the need for separate processing operations.
Solution Approach 2:
The control resource blocks are designed to be self-sufficient by including both reference signals and data elements within the same CRB structure. The reference signals enable the UE to perform self-channel-estimation without requiring additional dedicated reference signal resources, allowing the control channel to serve its own channel estimation needs.
3Productivity
If fast control channel signaling is implemented for grant-free uplink, then productivity and response time are improved, but device complexity increases
Solution Approach 1:
The system pre-configures grant-free uplink resources and associated control channel monitoring parameters before actual uplink transmission is needed. UEs are pre-assigned specific CSS configurations and RNTI values that enable them to quickly monitor for grants without requiring complex real-time resource selection or negotiation, thus improving productivity while managing complexity through advance configuration.
4Adaptability or versatility
If irregular resource block granting across slots or mini-slots is used, then adaptability and scheduling flexibility are improved, but loss of time for resource allocation increases
Solution Approach 1:
The resource block granting scheme is made dynamic by allowing different CSS configurations to monitor different slot structures and resource block patterns. The system can adaptively assign UEs to monitor CSS0-CSS3 with different aggregation levels and time-domain configurations based on current traffic conditions, enabling flexible resource allocation without fixed rigid patterns that would waste time.
Data Source
AI summary
The present disclosure describes various aspects of the implementation and design of Physical Downlink Control Channel (PDCCH) in 5G new radio (NR) applications. Aspects include methods, apparatuses, and computer-readable medium for one or more of multiple PDCCH search spaces, control resource block (CRB), irregular multiple slots or mini-slots grants, or fast control channel signaling for grant-free uplink (UL). For example, different scheduling entities can each have one or two search spaces defined (e.g., common and/or user equipment (UE)-centric search spaces). Also, CRBs can be used as units for PDCCH transmission instead of resource element groups/control channel elements (REGs/CCEs). In addition, irregularities in time domain, frequency domain, or both can be introduced in the granting of resource blocks (RBs) over multiple slots or mini-slots. Moreover, signaling can be used to indicate to a UE configured for grant-free UL the portion of the pool of resources available for grant-free UL.