Cross-Scheduling Random Access Response Carrier Indication
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Solution Overview
Problem
Current LTE and LTE-Advanced systems do not support cross scheduling during the random access procedure, limiting network flexibility and requiring multiple timing advances for distributed network receivers, and UE cannot perform RACH on secondary cells or receive cross-carrier scheduling for UL resources.
Innovation Solution
The system performs a random access procedure where a downlink random access response from a network node to a user equipment includes an explicit indication of the component carrier or cell to which a timing advance applies, allowing the UE to operate synchronously on the indicated carrier, enabling cross scheduling during RACH procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cross scheduling is not supported during random access procedure, then the system maintains simplicity in random access handling, but network flexibility is limited and multiple timing advances are required for distributed network receivers
Solution Approach 1:
The patent segments the random access response by including a carrier indicator field that explicitly identifies which component carrier the timing advance applies to. This allows the random access procedure to be divided into carrier-specific segments, enabling cross-carrier scheduling while maintaining clear organization and avoiding overall procedure complexity.
Solution Approach 2:
The patent adds a new dimension to the random access response by introducing an explicit carrier indication field. This additional dimension allows the system to identify which component carrier the timing advance command applies to, enabling cross-carrier scheduling without complicating the existing random access structure.
2Adaptability or versatility
If UE performs random access on secondary cells without cross scheduling, then the random access procedure remains straightforward, but UE cannot receive cross-carrier scheduling for uplink resources
Solution Approach 1:
The patent applies preliminary action by including the carrier indicator field in the random access response before the UE needs to apply the timing advance. This advance identification of the target component carrier allows the UE to correctly apply the timing advance to the appropriate carrier and prepares the system for subsequent cross-carrier scheduling of uplink resources.
Solution Approach 2:
The carrier indicator field acts as an intermediary that bridges the random access procedure and cross-carrier scheduling. It provides the necessary information to link the timing advance command with the specific component carrier, enabling the UE to receive cross-carrier scheduling for uplink resources while maintaining clear timing advance applicability.
3Measurement precision
If multiple individual random access responses are sent for different cells, then each cell's timing advance can be precisely indicated, but PDCCH overhead increases
Solution Approach 1:
The patent merges multiple random access responses into a single PDCCH message by including a carrier indicator field that identifies which component carrier the timing advance applies to. This consolidation reduces the number of separate PDCCH messages needed while maintaining precise timing advance carrier identification through the explicit carrier indication.
Data Source
AI summary
In a random access procedure, a downlink random access response indicates at least a timing advance and an explicit indication identifying one component carrier or cell (CC/Cell) of a plurality of component carriers or cells, or a group of CCs/Cells, to which the timing advance applies. The eNB or UE then operate their radio on the indicated one CC/Cell synchronous with the timing advance. In various embodiments the random access response may also indicate an uplink resource granted to the user equipment, which lies on that same one or group of CCs/Cells. The explicit indication may be a single bit indicating a timing advance group; a CC/Cell/group index whose presence in the response is indicated by a flag bit; a CC/Cell/group index in the response is known from the response's format whether it includes such an index, where the format indication can be via a bit in the response itself or RRC signaling or implicit from the RACH and cross-carrier scheduling being configured.