LTE Random Access Message 3 C-RNTI Field Removal
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Solution Overview
Problem
In the LTE wireless communications system, the random access procedure faces issues such as radio link failure, handover, and tracking area update, leading to potential C-RNTI invalidation, power wastage due to delayed response messages, and increased interference and overhead, especially in contention-based scenarios, where UEs may receive unintended responses and experience contention resolution delays.
Innovation Solution
The proposed method involves outputting message 3 without a specific field indicating C-RNTI status, starting a timer for message 3, and using mechanisms to detect and manage T-CRNTI adoption and retransmissions, ensuring accurate contention resolution and resource allocation, including setting message 4 to include authentication and ciphering requests during network attach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated preamble is assigned by network to specific UE, then contention between UEs is eliminated, but device complexity and overhead increase due to additional signaling required for preamble assignment and management
Solution Approach 1:
The patent extracts the contention resolution function from the preamble assignment process itself. Instead of relying on dedicated preambles assigned by the network, the invention allows UEs to use randomly selected preambles and resolves contention through the message 3 transmission phase, where the network can identify the UE and assign resources without requiring complex dedicated preamble management.
Solution Approach 2:
The UE performs self-identification through message 3 transmission containing its identity information. The network uses this self-provided information to resolve contention and assign uplink resources, eliminating the need for the network to pre-assign dedicated preambles to each UE.
2Device complexity
If random access preamble is randomly selected by UE, then device complexity is reduced, but collision probability increases leading to retransmissions and power wastage
Solution Approach 1:
The patent introduces a preliminary contention resolution phase through message 3 transmission. Before final resource allocation, the network receives the UE's identity information and can prepare appropriate uplink grants, reducing the need for repeated random access attempts and associated power consumption.
Solution Approach 2:
The network provides feedback through message 4 (contention resolution message) containing uplink resource allocation information. This feedback mechanism allows the UE to transition from random access to scheduled transmission efficiently, minimizing retransmissions and power wastage.
3Measurement precision
If RACH transmission opportunity is assigned by network, then timing alignment is improved, but loss of time increases due to waiting for network assignment
Solution Approach 1:
The network performs preliminary timing alignment measurements by detecting the UE's random access preamble and calculating the timing offset. This preliminary action allows the network to prepare accurate timing alignment commands in the random access response, enabling the UE to achieve precise timing alignment without requiring multiple access attempts or waiting for additional assignment messages.
4Productivity
If multiple UEs transmit RACH signals simultaneously, then system throughput is improved, but collision probability increases causing timing offset and access failure
Solution Approach 1:
The patent introduces message 3 as an intermediary transmission phase. UEs transmit their identity information in message 3 after the random access preamble, allowing the network to mediate the contention resolution process. This intermediary step enables the network to manage multiple simultaneous access attempts efficiently, maintaining high system throughput while ensuring reliable access through controlled resource allocation.
Data Source
AI summary
A method for handling a random access procedure in a user equipment, called UE hereinafter, of a wireless communications system includes outputting a message 3 as a scheduled transmission not including a specific field indicating whether the UE has a cell Radio Network Temporary Identifier, called C-RNTI hereinafter, or not during the random access procedure.