Uplink Time Synchronization via Integrate and Dump Accumulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE OFDMA systems, maintaining uplink time synchronization is challenging due to noisy and unreliable Physical Uplink Shared Channel (PUSCH) measurements, especially when handling both high-speed and low-speed data services, and residual synchronization errors after MAC layer synchronization, which affects system performance and interference between users.
Innovation Solution
An eNodeB processor implements an Integrate & Dump state machine with advanced time stamp techniques and a weighting function to accumulate time errors, using a novel integration formula and interpolation for missing samples, allowing reliable time advance adjustments even in noisy environments and varying data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PUSCH measurements are used for timing error detection, then timing error can be measured, but the measurements are noisy and unreliable especially for low-speed data services
Solution Approach 1:
The patent combines timing error measurements from multiple PUSCH signals and multiple measurement instances into a single accumulated timing error value. By merging multiple noisy measurements together through accumulation and averaging, the system achieves more reliable and accurate timing error detection, especially for low-speed data services where PUSCH transmission is infrequent.
Solution Approach 2:
The patent performs preliminary timing error measurements and accumulations before making final timing adjustment decisions. The system continuously accumulates timing error values from multiple PUSCH measurements over time, preparing a reliable estimated timing error that can be used for accurate time advance adjustments, rather than reacting to individual noisy measurements.
2Reliability
If regular low pass filter is used to remove noise from PUSCH measurements, then noise is reduced, but it fails to support both low and high speed data services
Solution Approach 1:
The patent implements a dynamic measurement accumulation mechanism that adapts to varying data rates. For high-speed services with frequent PUSCH transmissions, the system accumulates measurements rapidly. For low-speed services with infrequent PUSCH transmissions, the system waits and accumulates over longer periods. This dynamic adaptation allows reliable timing error measurement across all service types, unlike static low pass filters.
Solution Approach 2:
The patent changes the accumulation parameters based on service type and traffic conditions. The system adjusts the number of measurements to accumulate, the time window for accumulation, and the weighting factors based on whether the service is high-speed or low-speed, ensuring optimal performance for each service type rather than using a fixed filtering approach.
3Measurement precision
If Cyclic Prefix correlation techniques are used for timing error estimation, then timing error can be estimated for OFDM signals, but these techniques cannot be applied to OFDMA systems with multiple users
Solution Approach 1:
The patent segments the multi-user OFDMA signal processing into individual user measurements. Instead of trying to estimate timing errors from the composite multi-user signal (which fails due to user interference), the system processes each user's PUSCH measurements separately, accumulates timing errors for each user independently, and applies user-specific timing adjustments. This segmentation approach makes the measurement technique applicable to multi-user OFDMA systems.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An apparatus and method for uplink time synchronization in a communication system includes a first step (602) of receiving uplink data from a user equipment (108). A next step (604) includes storing a time error of the uplink data along with a time stamp. A next step (620) includes integrating the time error to provide an accumulated time error. A next step (606, 626) includes dumping the accumulated time error upon the time stamps of the accumulated data meeting a timing condition. A next step (610) includes comparing the accumulated time error against a threshold. A next step (616) includes scheduling a time advance with the user equipment (108) if the accumulated time error exceeds the threshold.