LTE Uplink Synchronization via Negative Timing Offset
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Solution Overview
Problem
Current 3GPP LTE networks are limited by a maximum cell radius due to the maximum supported round trip delay of the random access procedure, preventing connections beyond this radius, which hinders coverage extension and compatibility with larger cell radius networks, especially for LTE-MTC and NB-IoT devices.
Innovation Solution
A method that synchronizes uplink communication between a UE and a cell by determining PRACH capabilities, applying a negative timing offset, and transmitting PRACH signals at specific power levels and times to position them within the cell's detection window, even beyond the standard maximum cell radius, using techniques like GPS and pathloss estimation to derive the necessary offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the UE transmits PRACH signals using standard timing alignment, then the signal falls within the eNodeB detection window for cells within maximum radius, but the signal falls outside the detection window for cells beyond maximum radius, preventing connection establishment
Solution Approach 1:
The UE performs preliminary timing offset calculations based on estimated distance (from GPS, A-GNSS, ECID, OTDOA, UTDOA, or pathloss estimates) before transmitting PRACH signals. This preliminary action positions the PRACH signal within the eNodeB detection window even for cells beyond maximum radius, enabling connection establishment where standard timing would fail
Solution Approach 2:
The invention changes the timing parameter of PRACH signal transmission by applying a negative timing offset. This parameter modification shifts the signal arrival time at the eNodeB to fall within the detection window, resolving the contradiction between extended cell radius and reliable signal detection
2Length of stationary object
If the UE applies coverage enhancement to increase maximum coupling loss by more than 15 dB, then the device can operate beyond 400 km range, but the existing RA procedure design prevents connection establishment due to position exceeding maximum RTD
Solution Approach 1:
The invention makes the PRACH transmission timing dynamic by calculating and applying a negative timing offset based on the UE's estimated distance from the cell. This dynamic adjustment allows the RA procedure to adapt to extended ranges beyond maximum RTD while maintaining compatibility with LTE standards, enabling MTC and NB-IoT devices to connect at ranges exceeding 400 km
Solution Approach 2:
The UE performs preliminary distance estimation and timing offset calculation before PRACH transmission. This preliminary action ensures that even with coverage enhancement capabilities, the signal is transmitted at the correct timing to be detected by the eNodeB, maintaining RA procedure compatibility while extending operational range
3Reliability
If the UE transmits multiple PRACH signals with different negative timing offsets, then the probability of successful detection by eNodeB increases, but the connection establishment time increases
Solution Approach 1:
The UE performs preliminary distance estimation using GPS, A-GNSS, ECID, OTDOA, UTDOA, or pathloss calculations before transmitting PRACH signals. This preliminary action allows the UE to calculate the appropriate negative timing offset in advance, enabling single-attempt successful detection and minimizing connection establishment time while maintaining high detection probability
Solution Approach 2:
The UE uses its own positioning capabilities (GPS, A-GNSS, ECID, OTDOA, UTDOA) and pathloss estimates to self-determine the timing offset without requiring multiple transmission attempts. This self-service approach reduces the need for repeated PRACH transmissions, thereby minimizing connection establishment time while ensuring reliable detection
Data Source
AI summary
A method of synchronizing uplink between a UE and a cell, the method comprising determining PRACH capabilities of the UE, determining a negative timing offset for use with the transmission of at least one PRACH signal, determining an order for utilizing the negative timing offset, transmitting from the UE, at least one PRACH signal from a group of N PRACH signals, each of the at least one PRACH signals having a predetermined power level and transmitted by the UE at a time based on the negative timing offset, the order, and the PRACH capabilities of the UE.