Uplink Timing Synchronization for Fixed M2M Terminals
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Solution Overview
Problem
Current LTE mechanisms for uplink timing synchronization in fixed-location M2M terminals require frequent random access procedures due to internal clock drift, leading to increased overhead and energy consumption, as they assume mobility and short uplink timing alignment periods.
Innovation Solution
A method where fixed-location M2M devices calculate uplink timing using downlink synchronization and a stored uplink timing adjustment value from a previous transmission, allowing reuse of the value even after periods of inactivity or internal clock drift, reducing the need for frequent synchronization updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTE mechanisms are used for uplink timing synchronization in fixed-location M2M terminals, then timing synchronization can be maintained, but overhead and energy consumption increase due to frequent random access procedures
Solution Approach 1:
The base station pre-calculates and stores uplink timing adjustment values for fixed-location M2M terminals based on their known positions. When a terminal needs to transmit, it retrieves the pre-calculated timing value without performing random access procedures, thereby maintaining synchronization reliability while eliminating frequent energy-consuming synchronization updates
Solution Approach 2:
The patent creates a copy of the uplink timing adjustment value from the base station's pre-calculated data and stores it locally at the M2M terminal. This local copy allows the terminal to autonomously apply timing adjustments without repeatedly accessing the base station, reducing overhead and energy consumption while maintaining accurate synchronization
2Measurement precision
If LTE mechanisms with short uplink timing alignment periods are used, then timing accuracy can be maintained for mobile UEs, but overhead increases due to frequent synchronization updates
Solution Approach 1:
The patent applies different synchronization strategies to different types of terminals: mobile UEs continue to use frequent random access procedures for timing updates, while fixed-location M2M terminals use pre-calculated timing values. This localized differentiation maintains timing accuracy for mobile devices while reducing overhead for fixed devices that do not require frequent updates
Solution Approach 2:
The system changes the timing alignment period parameter dynamically based on terminal mobility status. For fixed-location M2M terminals, the timing alignment period is effectively extended indefinitely using pre-calculated values, while mobile UEs maintain the standard shorter period. This parameter adaptation reduces overhead without compromising timing accuracy where needed
3Reliability
If random access procedures are performed frequently for uplink timing synchronization, then synchronization accuracy can be maintained, but device complexity and processing requirements increase
Solution Approach 1:
The patent extracts the timing calculation function from the M2M terminal and relocates it to the base station. The base station pre-calculates timing adjustment values based on terminal positions and stores them centrally. Terminals simply retrieve and apply these pre-calculated values, eliminating complex timing calculation requirements at the terminal while maintaining synchronization accuracy
Data Source
AI summary
A method for determining synchronization of uplink timing in a machine type communication (MTC) system comprising a machine type communication device (MTCD) and a network element is disclosed that takes advantage of the MTCD being at a fixed location relative to the network element. The method includes receiving at the MTCD an uplink timing adjustment value from the network element and storing the uplink timing adjustment value at the MTCD. The MTCD then uses the stored uplink timing adjustment value from a previous uplink transmission for synchronizing uplink timing for a subsequent uplink transmission from the MTCD to the network element even following a period of inactivity of the MTCD, or expiration of any existing maximum uplink timing alignment period permitted for use of the timing adjustment value by the MTCD, or MTCD clock drift.