Uplink Synchronization in Unlicensed Spectrum via Autonomous Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in 3GPP LTE, performing uplink synchronization in unlicensed spectrum without a synchronization signal is a challenge, as existing methods rely on paired downlink spectrum or synchronization signals, which are not always available.
Innovation Solution
A method and apparatus for a user equipment (UE) to configure at least one uplink carrier in an uplink-only spectrum and perform uplink synchronization, allowing for synchronization without relying on paired downlink spectrum or synchronization signals, by using internal frequency tracking and configuring UL-only carriers with separate reference carriers for synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If paired downlink spectrum or synchronization signals are used for uplink synchronization, then synchronization accuracy is improved, but spectrum availability and flexibility are reduced
Solution Approach 1:
The patent extracts the synchronization function from the downlink spectrum and implements it independently in the uplink spectrum. The UE performs autonomous synchronization by measuring uplink channel conditions and adjusting transmit timing without relying on downlink synchronization signals, thereby enabling UL-only spectrum operation while maintaining synchronization capability
Solution Approach 2:
Instead of using downlink signals to synchronize uplink transmissions (traditional approach), the patent inverts the approach by using uplink channel measurements and autonomous timing adjustment to achieve synchronization. The UE determines uplink timing based on uplink reference signals and timing advance commands rather than downlink synchronization signals
2Productivity
If unlicensed spectrum is used to increase capacity, then system capacity is improved, but channel acquisition complexity and collision handling requirements increase
Solution Approach 1:
The patent applies preliminary action by performing uplink synchronization and channel acquisition before actual data transmission in unlicensed spectrum. The UE autonomously acquires uplink timing and frequency synchronization in advance, and implements listen-before-talk procedures to check channel availability before transmitting, thereby simplifying subsequent channel access and reducing collision probability
Solution Approach 2:
The UE performs self-service by autonomously acquiring uplink synchronization without network assistance in UL-only spectrum. The device independently measures channel conditions, determines timing advance, and adjusts transmit timing without requiring downlink synchronization signals or paired spectrum, thereby reducing channel acquisition complexity for unlicensed band operation
3Adaptability or versatility
If UL-only spectrum configuration is implemented, then spectrum flexibility is improved, but synchronization capability deteriorates without downlink pairing
Solution Approach 1:
The patent introduces timing advance commands as an intermediary mechanism to maintain synchronization in UL-only spectrum. The network provides timing advance commands to the UE based on uplink reception timing measurements, which the UE uses to adjust its transmit timing. This intermediary mechanism enables reliable synchronization without requiring downlink synchronization signals or paired spectrum
Data Source
AI summary
A method and apparatus for performing an uplink (UL) synchronization in a wireless communication system is provided. A user equipment (UE) configures at least one UL carrier in an UL-only spectrum, and performs UL synchronization on the at least one UL carrier. The UL synchronization on the at least one UL carrier may be performed by various methods.