Downlink Beam Identification via Random Access Preamble
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Solution Overview
Problem
In 5G wireless communication systems, the lack of TX/RX beam reciprocity at user equipment (UE) leads to inefficient random access procedures, resulting in delayed power ramp-up and increased signaling overhead, as UE cannot uniquely identify uplink TX beams for Msg1 transmissions, and base stations struggle to identify downlink TX beams for system information messages.
Innovation Solution
The method involves performing first beam sweeping for random access preamble transmission, determining beam order for second beam sweeping by selecting the same last transmission beam, and enabling base stations to identify downlink TX beams from received random access channel preambles or occasions, allowing for selective transmission of system information messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If beam sweeping is performed for random access preamble transmission, then the ability to transmit random access preambles is improved, but the time delay and signaling overhead increase due to lack of TX/RX beam reciprocity
Solution Approach 1:
The base station performs downlink beam sweeping to establish beam correspondence relationships before the random access procedure. The UE stores this beam correspondence information, allowing it to directly determine the appropriate uplink transmission beam without performing time-consuming beam sweeping during the random access procedure, thus reducing time delay while maintaining transmission capability
2Adaptability or versatility
If beam sweeping is performed to identify downlink transmission beam, then the base station's ability to transmit system information is improved, but the signaling overhead and interference increase
Solution Approach 1:
The UE provides feedback information about the downlink transmission beam through the random access procedure. The UE indicates the identified downlink beam in its random access message, allowing the base station to use this feedback to select the appropriate beam for transmitting system information, eliminating the need for extensive beam sweeping and reducing signaling overhead
Data Source
AI summary
A communication method and system for converging a fifth generation (5G) communication system for supporting higher data rates beyond a fourth generation (4G) system with a technology for internet of things (IoT) are provided. The communication method and system includes intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. In accordance with an aspect of the disclosure, a method and an apparatus for transmitting a random access preamble in a wireless communication system are provided. In accordance with another aspect of the disclosure, a method and an apparatus for requesting and transmitting system information are provided.