Preamble Aggregation for 5G NR Initial Access Latency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The 5G new radio (NR) mobile communication systems face challenges in initial access latency due to the traditional random access procedure, which is not suitable for latency-sensitive services like ultra-reliable low-latency communication (URLLC), and the discovery of the best beam for transmission and reception is delayed, leading to inefficiencies in coverage and access probability.
Innovation Solution
A method involving preamble aggregation, where a wireless communication device transmits multiple copies of a preamble on different uplink random access channel occasions before a response time window expires, allowing for simultaneous monitoring of responses and reducing latency in discovering the best transmitting beam during the initial access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the traditional four-step random access procedure is used, then the system maintains compatibility with existing protocols, but the initial access latency becomes too large for latency-sensitive services
Solution Approach 1:
The patent applies preliminary action by transmitting multiple preamble copies in advance before the response time window expires. Instead of waiting for the traditional response window to determine success or failure, the UE proactively sends aggregated preambles early, enabling the network to detect and respond faster, thus reducing initial access latency while maintaining protocol compatibility
Solution Approach 2:
The patent implements skipping by allowing the UE to skip the traditional waiting period for the response time window. By transmitting multiple preamble copies before the window expires and monitoring for responses during this period, the procedure rushes through the initial access steps more quickly, reducing latency for URLLC services
2Ease of operation
If beam switching is delayed until PRACH retransmission after response window expiration, then the system follows traditional procedures, but the discovery of the best transmitting beam is delayed causing coverage inefficiency
Solution Approach 1:
The patent applies preliminary action by performing beam discovery in advance during the initial preamble aggregation transmission. The UE transmits preamble copies on different beams before the response time window expires, allowing the network to identify the best beam early in the procedure rather than waiting for retransmission, thus improving coverage efficiency
Solution Approach 2:
The patent introduces another dimension by utilizing multiple spatial beams simultaneously for preamble transmission. Instead of sequential single-beam transmission, the system transmits preambles across multiple beam dimensions in parallel, enabling faster beam discovery and improving coverage radius through spatial diversity
3Loss of time
If multiple preamble copies are transmitted on different RACH occasions before response window expiration, then the initial access latency is reduced and beam discovery is improved, but the complexity of the random access procedure increases
Solution Approach 1:
The patent applies universality by designing the preamble aggregation mechanism to serve multiple functions simultaneously: it reduces initial access latency, discovers the best transmitting beam, and improves coverage. This multi-functional approach consolidates several objectives into a single procedure, managing complexity while achieving multiple benefits
4Reliability
If the response time window is set to at least 10 ms to ensure reliable detection, then the system maintains detection reliability, but the latency for retransmission after window expiration becomes huge
Solution Approach 1:
The patent applies continuity of useful action by maintaining preamble transmission and response monitoring activities throughout the response time window rather than stopping after a single attempt. The UE continuously monitors for responses to aggregated preambles and can initiate further transmissions before window expiration, ensuring detection reliability while reducing retransmission latency through sustained activity
Data Source
AI summary
Methods, apparatus and systems are described for preamble aggregation in a random access procedure. In one embodiment, a method performed by a wireless communication device for preamble aggregation is disclosed. The method includes: transmitting, to a wireless communication node, a first message comprising a number of copies of a preamble for an access to the wireless communication node, wherein the number is an integer larger than one, and wherein the copies of the preamble are carried by different uplink random access channel (RACH) occasions respectively; and monitoring, within a response time window, for a second message comprising a response to the first message from the wireless communication node, wherein all of the copies of the preamble are transmitted before the response time window expires.