Directional Channel Access for mmWave Unlicensed Initial Access
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Solution Overview
Problem
Existing channel access methods in unlicensed spectrum, particularly in the 57 GHz to 71 GHz band, face challenges in ensuring robust and efficient initial access due to interference and high path loss, especially in mmWave frequencies, where directional communication is necessary but current LBT procedures can lead to increased latency and failure in channel access.
Innovation Solution
A method and system for initial channel access that incorporates directional sensing and communication, allowing UEs to perform LBT in multiple spatial directions, using directional LBT procedures for MSG1, MSG2, MSG3, and MSG4 transmissions, and enabling dynamic LBT configuration based on traffic and regulatory requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If directional LBT procedures are implemented in multiple spatial directions, then robustness and beam selection are improved, but device complexity and processing overhead increase
Solution Approach 1:
The channel access procedure is segmented into multiple directional LBT operations, where each spatial direction is handled independently with its own LBT check. This allows the system to divide the complex multi-directional channel access into manageable segments, improving reliability through comprehensive coverage while maintaining organized complexity management.
Solution Approach 2:
The LBT procedure is made dynamic by adaptively selecting which directions to monitor and access based on channel conditions, beam measurements, and spatial relationships. The system dynamically adjusts the number and orientation of LBT directions rather than uniformly checking all possible directions, thereby improving robustness while controlling complexity.
2Reliability
If LBT is performed in multiple spatial directions, then channel access reliability is improved, but initial access latency increases
Solution Approach 1:
Beam measurements and spatial channel assessments are performed preliminarily before the actual LBT procedure. This preliminary action identifies the most promising spatial directions in advance, allowing the LBT to focus only on those directions rather than exhaustively checking all directions, thus improving success rate while reducing latency.
Solution Approach 2:
The system performs LBT on a selective subset of spatial directions rather than all possible directions. By performing partial action (only on necessary directions identified through preliminary beam measurements), the system achieves sufficient channel access reliability without the excessive time cost of comprehensive multi-directional LBT.
3Adaptability or versatility
If directional sensing and communication are used, then connectivity and spatial diversity are improved, but processing requirements and energy consumption increase
Solution Approach 1:
Directional sensing and communication resources are concentrated on specific spatial directions that are most relevant for channel access, rather than uniformly processing all directions. The system applies high-quality directional processing locally to identified target directions while reducing or eliminating processing in other directions, thereby improving spatial connectivity while managing energy consumption.
Data Source
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AI summary
A method for operating a user equipment (UE) in a wireless communications system includes the UE decoding a master information block (MIB) or a system information block (SIB) or both a MIB and a SIB received from a base station, determining that discovery burst transmission window (DBTW) is enabled, in accordance with at least the decoded MIB or SIB, decoding DBTW parameters, and executing a random access channel (RACH) procedure in accordance with the decoded DBTW parameters.