Open-Loop Timing With Extended Cyclic Prefixes For IoT
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In cellular IoT communication, power-limited devices face significant power consumption due to closed-loop timing synchronization, which is not justified for infrequent small-data transmissions, and open-loop timing may lead to unsynchronized communications unless longer uplink cyclic prefixes are used.
Innovation Solution
Implementing open-loop timing with varying cyclic prefix lengths for uplink and downlink signals, where the uplink signal has a longer cyclic prefix to cover round trip delay, and using orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC-FDMA) for modulation, allowing devices to conserve power and maintain synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop timing synchronization is used, then communication synchronization is maintained, but power consumption increases significantly
Solution Approach 1:
The patent extracts and removes the closed-loop timing synchronization mechanism from the system. Instead of maintaining continuous timing advance commands between UE and base station, the system eliminates this interactive synchronization loop entirely, allowing power-limited devices to operate without this energy-consuming synchronization overhead while still achieving acceptable communication reliability through other means.
Solution Approach 2:
The system implements self-service timing where each device independently determines its transmission timing based on downlink signal reception time, without requiring continuous timing commands from the base station. The UE autonomously adjusts its uplink transmission timing based on the received downlink signal, eliminating the need for power-consuming closed-loop timing synchronization while maintaining basic synchronization.
2Use of energy by moving object
If open-loop timing is used, then power consumption is reduced, but communication synchronization deteriorates
Solution Approach 1:
The patent changes the cyclic prefix length parameter to compensate for the lack of closed-loop timing synchronization. By extending the cyclic prefix duration in the OFDMA/SC-FDMA signals, the system creates a larger timing tolerance window that accommodates open-loop timing variations, thereby maintaining communication reliability without requiring power-consuming synchronization loops.
3Reliability
If different cyclic prefix lengths are used for uplink and downlink, then synchronization is maintained in open-loop timing, but signal structure complexity increases
Solution Approach 1:
The patent applies different cyclic prefix lengths to different transmission directions (uplink vs. downlink) based on their specific requirements. The uplink uses extended cyclic prefixes to accommodate round-trip timing variations in open-loop operation, while the downlink uses standard cyclic prefixes. This localized differentiation solves the synchronization problem without requiring complex system-wide changes.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Methods, systems, and devices are described for wireless communication at a user equipment (UE). A UE may establish a connection with a cell based on an initial access procedure. The UE may also receive a downlink signal from the cell which includes a first cyclic prefix. The UE may transmit an uplink signal with a second cyclic prefix to the cell. The second cyclic prefix may have a different length than the first cyclic prefix.