Uplink Closed-Loop Transmit Diversity Alignment
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Solution Overview
Problem
In cellular radio systems, the dynamic switching of uplink closed-loop transmit diversity (CLTD) modes during serving cell changes can result in mismatches between the UE and the new serving NodeB, leading to suboptimal transmit diversity performance due to unknown precoding weights and differing radio channel conditions.
Innovation Solution
The UE and NodeB are configured to align their UL CLTD modes and precoding vectors by setting them to predetermined default modes or vectors during serving cell changes, eliminating the need for explicit signaling and ensuring compatibility between the UE and the new serving NodeB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the NodeB dynamically switches CLTD modes during serving cell changes, then the transmit diversity performance can be optimized for current channel conditions, but the UE and new serving NodeB may operate with mismatched CLTD modes and unknown precoding weights
Solution Approach 1:
The UE stores the CLTD mode and precoding weights information in advance before serving cell changes occur. This preliminary storage ensures that when the UE connects to a new serving NodeB, the configuration information is already available, eliminating mismatches and ensuring continuous optimized transmit diversity performance without information loss during the handover process.
2Stability of the object's composition
If the UE stores CLTD mode information from the old serving cell, then the configuration can be maintained during handover, but the stored information may become outdated and incompatible with the new serving cell's channel conditions
Solution Approach 1:
The UE performs preliminary storage of CLTD mode information before handover, ensuring configuration stability is maintained. The stored information serves as a baseline that can be quickly restored after connecting to the new serving NodeB, providing both stability during the transition and adaptability once the new connection is established.
Solution Approach 2:
The system uses feedback mechanisms where the UE reports stored CLTD mode information to the new serving NodeB, which then determines whether to maintain the stored configuration or adjust it based on current channel conditions. This feedback loop ensures both stability of the configuration process and adaptability to new environmental conditions.
3Reliability
If explicit signaling is used to synchronize CLTD modes between UE and new serving NodeB, then configuration alignment can be ensured, but the signaling overhead and system complexity increase
Solution Approach 1:
The UE autonomously stores and manages its own CLTD mode information without requiring explicit signaling from the network for every handover event. This self-service approach allows the UE to independently maintain configuration alignment, reducing signaling overhead and system complexity while ensuring reliable configuration synchronization when needed.
Data Source
AI summary
Methods and devices are described whereby a User Equipment (UE) and a base station are configured to align the uplink (UL) closed-loop transmit diversity (CLTD) status of the UE and the base station during a serving cell change involving a new base station.