Machine-Specific Synchronization Signal for MTC Devices
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Solution Overview
Problem
Low coverage machine type communication (MTC) devices in LTE networks face challenges with prolonged synchronization latency and power consumption due to the need for re-synchronization after extended sleep periods, as they lose synchronization with the cell and require lengthy averaging times to re-acquire timing and frequency alignment using existing CRS signals.
Innovation Solution
A machine-specific synchronization signal (mSYNC) with higher density in time and frequency is transmitted from base stations, featuring a longer periodicity to facilitate fast timing and frequency acquisition and tracking, allowing MTC devices to wake up just before scheduled mSYNC transmission and re-synchronize without lengthy averaging, thereby reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MTC devices use existing CRS signals for re-synchronization after extended sleep periods, then they can maintain compatibility with existing LTE infrastructure, but they experience prolonged synchronization latency and increased power consumption due to the need for lengthy averaging times
Solution Approach 1:
The patent segments the synchronization function by introducing a dedicated machine-type synchronization signal (MSync) separate from the existing cell-specific reference signals (CRS). This segmentation allows MTC devices to use MSync for fast re-synchronization without relying on the slower CRS-based methods, thereby reducing synchronization latency while maintaining accuracy.
Solution Approach 2:
The patent introduces MSync as an intermediary signal specifically designed for MTC devices. This intermediary signal acts as a bridge between the existing LTE infrastructure and MTC devices, enabling fast re-synchronization through higher time-frequency density without requiring changes to the core CRS-based synchronization mechanism.
2Reliability
If MTC devices use existing CRS signals for re-synchronization, then infrastructure compatibility is maintained, but power consumption increases due to extended averaging times required for reliable synchronization
Solution Approach 1:
By segmenting the synchronization function and introducing MSync, the patent enables MTC devices to achieve reliable synchronization faster, thereby reducing the time the device must remain active and consume power. The higher time-frequency density of MSync provides sufficient signal quality for reliable detection with shorter averaging times.
Solution Approach 2:
The MSync signal serves as an intermediary that reduces the energy burden on MTC devices by providing a more efficient re-synchronization mechanism. This intermediary signal allows devices to maintain synchronization reliability while minimizing the duration of active reception and processing, thus reducing overall power consumption.
3Reliability
If MTC devices wake up frequently to maintain synchronization, then synchronization accuracy is improved, but power consumption increases due to more frequent wake-up cycles
Solution Approach 1:
The patent employs periodic transmission of MSync signals with configurable periodicity. This periodic action allows MTC devices to wake up at predetermined intervals to receive synchronization updates, maintaining synchronization accuracy while optimizing power consumption by avoiding continuous monitoring. The network can adjust the periodicity based on device mobility and service requirements.
Solution Approach 2:
The MSync signal acts as an intermediary that enables efficient periodic synchronization. By providing a dedicated signal with higher time-frequency density, it allows devices to achieve accurate synchronization during brief wake-up periods, then return to sleep mode, thereby maintaining accuracy while minimizing energy consumption compared to continuous synchronization methods.
4Loss of time
If mSYNC is transmitted with higher time-frequency density, then fast re-synchronization is achieved, but signal overhead increases
Solution Approach 1:
The patent applies local quality by concentrating synchronization resources specifically for MTC devices through MSync, rather than uniformly distributing resources across all device types. The higher time-frequency density of MSync is localized to specific resource elements dedicated to MTC, providing fast re-synchronization capability where needed while minimizing overall overhead by not increasing density for all signals.
Solution Approach 2:
The patent uses partial action by implementing MSync with higher time-frequency density only in specific subframes and resource elements, rather than continuously across all time-frequency resources. This partial deployment achieves fast re-synchronization capability when needed while controlling overall overhead by limiting the extent of the enhanced signaling.
5Quantity of substance
If mSYNC is transmitted with longer periodicity, then overhead and inter-cell interference are reduced, but re-synchronization speed decreases
Solution Approach 1:
The patent employs parameter changes by making the MSync periodicity configurable rather than fixed. The network can adjust the periodicity parameter based on device mobility patterns, service requirements, and network conditions. This allows optimization of the trade-off between overhead reduction (longer periodicity) and re-synchronization speed (shorter periodicity) for different scenarios.
Solution Approach 2:
The patent introduces dynamics by allowing the MSync transmission parameters, including periodicity and time-frequency density, to be adapted based on device state and network conditions. MTC devices with different mobility characteristics or service requirements can receive appropriately configured MSync signals, enabling the system to dynamically balance overhead and re-synchronization speed.
Data Source
AI summary
A method of fast synchronization for low coverage machine type communication (MTC) devices is proposed. A machine-specific synchronization signal “mSYNC” with higher density in time and frequency is transmitted from each base station for fast timing and frequency acquisition and tracking. The mSYNC has a relatively longer periodicity (i.e., >>5 ms) to reduce overhead and inter-cell interference. The higher time-frequency density of mSYNC is designed to improve latency and power consumption by allowing the machine to wake up just before the scheduled mSYNC transmission time and to re-synchronize or track synchronization with the network without the need for long averaging time.