L2 Mobility Cell Switching Reduces 5G Interruption Latency
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Solution Overview
Problem
Current 5G communication systems experience significant latency and interruption during serving cell changes, particularly when UE moves between cells, due to the need for complete Layer-2 and Layer-1 resets, which is inefficient and time-consuming.
Innovation Solution
A method involving a wireless device that receives RRC messages with configuration information for multiple cells, allowing it to monitor and switch between cells using MAC Control Elements, thereby enabling seamless communication and reducing interruption time through optimized cell reconfiguration and mobility management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete Layer-2 and Layer-1 resets are performed during serving cell change, then serving cell change can be executed, but interruption time and latency increase significantly
Solution Approach 1:
The patent segments the cell change process into two distinct types: L3 mobility (complete reset) and L2 mobility (partial reset). By dividing the mobility management into these segments, the system can select the appropriate reset level based on service requirements, thereby reducing unnecessary interruption time while maintaining reliability when needed.
Solution Approach 2:
The patent introduces dynamic mobility management where the UE can switch between L3 and L2 mobility modes based on service requirements. The network can configure the UE to use L2 mobility for services requiring low latency, dynamically adjusting the reset behavior to optimize both reliability and interruption time.
2Reliability
If complete Layer-2 and Layer-1 resets are performed during serving cell change, then serving cell change can be executed, but overhead and complexity increase
Solution Approach 1:
The patent segments mobility management into L3 and L2 modes with distinct procedures. L2 mobility uses MAC CE-based TCI state activation without full layer resets, simplifying the process compared to L3 mobility. This segmentation reduces overhead and complexity by providing a lighter-weight alternative for appropriate scenarios.
Solution Approach 2:
The patent changes the mobility management parameters by introducing L2 mobility as a new operational mode. This parameter change allows the system to transition from always performing complete resets to selectively applying partial resets, thereby reducing overhead and complexity while maintaining necessary reliability.
3Adaptability or versatility
If L3 mobility measurements and RRC signalling are used for serving cell change, then cell reconfiguration can be performed, but latency and interruption time increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple TCI state lists for different cells via RRC messaging before mobility is needed. When L2 mobility is triggered, the UE can immediately switch cells using pre-prepared configuration information and MAC CE commands, eliminating the latency of real-time RRC reconfiguration during cell change.
Solution Approach 2:
The patent substitutes the mechanical RRC signalling-based cell reconfiguration process with a faster MAC CE-based mechanism for L2 mobility. This replacement eliminates the overhead and latency of complete RRC reconfiguration procedures while maintaining cell reconfiguration capability, significantly reducing latency.
Data Source
AI summary
A method performed by a wireless device may comprise: receiving, from a base station, at least one Radio Resource Control (RRC) message, wherein the at least one RRC message comprises: first configuration information indicating a Transmission Configuration Index (TCI) state list of a first cell; and second configuration information indicating a TCI state list of a second cell; receiving, from the base station and via the second cell, a first Medium Access Control (MAC) Control Element (CE), wherein the first MAC CE comprises an identifier associated with the first configuration information and associated with a first TCI state identifier, and wherein the first TCI state identifier indicates a first TCI state of the TCI state list of the first cell; monitoring, based on the first MAC CE and based on the first TCI state, Physical Downlink Control Channel (PDCCH) associated with the first cell; receiving, from the base station and via the first cell, a second MAC CE, wherein the second MAC CE comprises an identifier associated with the second configuration information and associated with a second TCI state identifier, and wherein the second TCI state identifier indicates a second TCI state of the TCI state list of the second cell; and monitoring, based on the second MAC CE and based on the second TCI state, PDCCH associated with the second cell.