Wireless Random Access Contention Resolution via C-RNTI Feedback
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Solution Overview
Problem
In contention-based random access procedures in wireless communication systems, user equipment (UE) may incorrectly determine the success of contention resolution due to unintentional control signals, leading to service delays and interference with other UEs.
Innovation Solution
A method where the contention resolution timer is stopped and the random access procedure is considered successful only upon receipt of a physical downlink control channel (PDCCH) transmission specifically addressed to the UE's cell-radio network temporary identity (C-RNTI) containing an uplink grant, preventing incorrect contention resolution and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timer is used for contention resolution in the random access procedure, then the UE can determine whether contention is successful, but the UE may incorrectly determine success when unintentional control signals are received before the timer expires
Solution Approach 1:
The patent introduces a feedback mechanism where the base station explicitly sends a contention resolution message containing the UE's identity (C-RNTI) to confirm successful contention resolution. The UE monitors for this specific feedback message during the timer period, and only stops the timer and declares success when the matching feedback is received. This resolves the ambiguity of receiving unrelated control signals by requiring positive confirmation from the base station.
Solution Approach 2:
The patent uses the base station as an intermediary to mediate the contention resolution process. Instead of the UE autonomously determining success based on timer expiration and generic signal reception, the base station acts as a mediator by sending a dedicated contention resolution message that explicitly confirms which UE has successfully resolved contention. This intermediary verification eliminates false positives from unintentional control signals.
2Productivity
If the UE determines contention success based on receiving any control signal before timer expiration, then the procedure completes quickly, but service delays occur due to incorrect determination
Solution Approach 1:
The patent prepares the UE in advance by configuring it with its C-RNTI identity before the random access procedure begins. The UE is pre-instructed to look for a contention resolution message containing this specific identity. This preliminary preparation enables the UE to quickly identify the correct confirmation signal among multiple control signals, maintaining fast procedure completion while ensuring accurate contention resolution determination.
3Adaptability or versatility
If contention-based random access is used to allow multiple UEs to access the network, then service availability increases, but collision between UEs occurs when they use the same preamble
Solution Approach 1:
The patent employs feedback-based contention resolution where the base station monitors random access preambles and sends individualized contention resolution messages to each UE that successfully transmitted a preamble. The message contains the UE's C-RNTI to uniquely identify the successful UE. This feedback mechanism allows multiple UEs to attempt access simultaneously (maintaining flexibility) while enabling the base station to resolve collisions by explicitly confirming which UE succeeded, preventing interference from unsuccessful UEs.
Data Source
AI summary
A method of performing contention resolution associated with a random access procedure includes transmitting, by the mobile communication terminal, a random access preamble; receiving, by the mobile communication terminal, a random access response; transmitting, by the mobile communication terminal, an uplink message and starting a contention resolution timer once the uplink message is transmitted; and receiving, by the mobile communication terminal, a physical downlink control channel (PDCCH), wherein the mobile communication terminal considers whether a contention resolution is successful or not by using either a cell radio network temporary identity (C-RNTI) on the PDCCH or a UE Contention Resolution Identity on a downlink shared channel (DL-SCH) associated with the PDCCH, wherein the mobile communication terminal considers the contention resolution successful and stops the contention resolution timer when the C-RNTI on the PDCCH matches the uplink message, and when the UE Contention Resolution Identity on the DL-SCH matches the uplink message.