Random Access Procedure Handling with Downlink Beam Synchronization
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Solution Overview
Problem
Existing methods for performing a random access procedure in LTE and LTE-Advanced systems fail when beamforming is operated, as they do not provide a mechanism for successful communication between user equipment and evolved Node-B.
Innovation Solution
A communication device that determines a random access sequence based on a synchronization signal transmitted via a downlink beam by a serving cell, transmits this sequence on a random access resource, and receives a random access response scheduled by downlink control information in a control resource.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If beamforming is operated by the eNB to improve communication performance, then data rate and coverage are improved, but the random access procedure fails because the UE cannot successfully perform RA with narrow beams
Solution Approach 1:
The patent segments the random access procedure into two independent parts: (1) beam selection for downlink communication, and (2) random access preamble transmission. The UE selects a beam based on downlink signal quality and uses that same beam for transmitting the random access preamble, thereby decoupling the beamforming function from the random access function and enabling both to work together successfully.
2Reliability
If narrow beams are used for communication, then coverage edge performance is improved, but the UE cannot receive signals in multiple beams simultaneously causing RA failure
Solution Approach 1:
The UE autonomously determines which beam to use for random access by measuring downlink signal quality in different beams and selecting the beam with the highest quality. This self-service approach allows the UE to adapt to the narrow beam configuration without requiring network coordination for each random access attempt, thereby maintaining ease of operation while benefiting from improved coverage edge performance.
Data Source
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AI summary
A communication device for handling a random access (RA) procedure comprises a storage device for storing instructions and a processing circuit coupled to the storage device. The processing circuit is configured to execute the instructions stored in the storage device. The instructions comprise determining a RA sequence according to a synchronization signal (SS) transmitted via a downlink (DL) beam by a serving cell; transmitting the RA sequence on a RA resource to the serving cell; and receiving a RA response (RAR) in response to the RA sequence from the serving cell, wherein the RAR is scheduled by a DL control information (DCI) in a control resource.