Timing Advance Estimation in Cellular Random Access
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Solution Overview
Problem
The existing Delay Estimation based Random Access (DERA) procedure is inadequate for systems with unpredictable processing delays and is not applicable to slotted communication systems like New Radio (NR), Narrowband Internet of Things (NB-IoT), LTE for Machines (LTE-M), and LTE, as it assumes a fixed and immediate response from the Base Station (BS).
Innovation Solution
The proposed solution involves the Base Station adding an 'added time delay' (TF) value to the Random Access Response (RAR), allowing the User Equipment (UE) to accurately estimate the timing advance (TA) independently, and comparing this with the UE's calculated reference time to determine if the RAR is intended for it, thereby enabling efficient contention resolution and collision detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the UE assumes a fixed processing time at the BS and immediate response, then the propagation delay estimation is simplified, but the accuracy of timing advance estimation deteriorates in systems with unpredictable processing delays
Solution Approach 1:
The BS includes the actual processing time (TF) in the RAR message as feedback to the UE. This allows the UE to receive direct information about the BS processing delay, enabling accurate timing advance estimation without complex assumptions about fixed processing times.
Solution Approach 2:
The patent changes the parameter being measured from just propagation delay to total delay (propagation delay + processing time). By measuring the total round-trip time and subtracting the known processing time TF, the UE can accurately determine the propagation delay even in systems with variable processing delays.
2Loss of time
If the BS replies instantly upon completion of processing, then the response time is minimized, but the UE cannot accurately determine if the RAR is intended for it in highly loaded systems
Solution Approach 1:
The BS performs preliminary action by including the processing time TF in the RAR before the UE can potentially send a third message. This allows the UE to immediately have all the information needed to verify the RAR is intended for it, enabling early collision detection.
Solution Approach 2:
The BS provides feedback about its processing time TF in the RAR message, allowing the UE to verify whether the RAR is intended for it by comparing the received timing information with its own calculations. This feedback mechanism enables reliable collision detection without extending the response time.
3Productivity
If the UE proceeds with transmission without early collision detection, then the transmission can be completed, but battery power is wasted in unsuccessful random access attempts
Solution Approach 1:
The UE performs preliminary verification of the RAR's intended recipient status by comparing timing information before proceeding to send the third message. This preliminary action allows the UE to detect collisions early and avoid unnecessary transmissions, saving battery power.
Solution Approach 2:
The UE uses feedback information from the RAR (specifically the processing time TF) to determine whether the RAR is intended for it. By verifying the timing advance estimation using the feedback TF value, the UE can quickly identify unsuccessful random access attempts and back off, avoiding wasted energy on futile transmissions.
Data Source
AI summary
A method implemented in a User Equipment, UE, for a cellular communication system includes transmitting a Random Access (RA) preamble and receiving a Random Access Response (RAR) from a base station (BS) containing a timing advance value, TA, indicative of a radio signal propagation delay between the UE and the BS and information indicative of an added time delay, TF, between reception of the RA preamble by the BS and transmission of the RAR by the BS.