Cross-TAG Scheduling for PDCCH-Ordered CFRA
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Solution Overview
Problem
Current wireless communication technologies, such as LTE and NR, face challenges in supporting cross-timing advance group scheduling and 2-step random access channel payload transmission for physical downlink control channel-ordered contention-free random access procedures, particularly in scenarios with different timing advance groups and limited DCI format capabilities.
Innovation Solution
The method involves a user equipment (UE) receiving downlink control information indicating a timing advance group and parameters for a random access message to be transmitted via a second cell, with the UE determining a timing advance value based on the indicated group and transmitting the message accordingly, enabling cross-TAG scheduling and 2-step random access procedures even when cells belong to different timing advance groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross-TAG scheduling is implemented for PDCCH-ordered CFRA, then network throughput and reliability are improved, but DCI format complexity increases
Solution Approach 1:
The DCI format is segmented into fixed fields and flexible fields. The fixed fields contain mandatory information for all CFRA procedures, while the flexible fields are selectively activated through a capability indication mechanism. This segmentation allows the system to maintain backward compatibility with legacy UEs while enabling enhanced cross-TAG scheduling functionality for capable UEs, thus improving reliability without universally increasing complexity.
Solution Approach 2:
The patent implements partial action by conditionally including certain DCI fields based on UE capability and network configuration. The flexible fields are only processed when the UE supports cross-TAG scheduling, allowing the system to achieve enhanced functionality where needed while maintaining simplicity elsewhere. This selective activation reduces the average complexity burden on the system.
2Loss of time
If 2-step RACH payload transmission is enabled, then latency is reduced, but processing requirements increase
Solution Approach 1:
The patent merges the random access preamble and payload transmission into a single uplink message (MsgA), eliminating the need for separate transmission steps. This consolidation reduces the number of processing cycles required and decreases access latency. The UE processes and transmits both components together, while the gNB receives and processes them as a unified structure with clearly defined relationships between the preamble and payload portions.
Solution Approach 2:
The UE performs preliminary processing of both the preamble and payload before transmission, preparing the complete MsgA structure in advance. The gNB is pre-configured with the expected MsgA structure, including the relationship between preamble indices and payload resources. This preliminary preparation eliminates the need for multiple sequential processing steps, thereby reducing latency without proportionally increasing processing complexity.
3Productivity
If carrier aggregation with different TAGs is supported, then network performance is improved, but timing synchronization complexity increases
Solution Approach 1:
The patent introduces the PDCCH-ordered CFRA mechanism as an intermediary to manage timing synchronization across multiple TAGs. The gNB uses this ordered random access procedure to explicitly configure and synchronize timing relationships between different TAGs. By controlling the timing through the PDCCH order and associated DCI fields, the system can coordinate multiple TAGs without requiring complex distributed synchronization protocols, thus improving network performance while managing synchronization complexity centrally.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, via a first cell, downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates a timing advance group of a second cell and one or more parameters associated with a random access message to be transmitted by the UE via the second cell, wherein the first cell and the second cell belong to different timing advance groups. The UE may transmit the random access message via the second cell according to the one or more parameters and a timing advance value determined based at least in part on the timing advance group of the second cell. Numerous other aspects are provided.