CoMP Downlink Timing Alignment for Interference-Free Reception
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In coordinated multi-point transmission/reception (CoMP) scenarios, downlink signals from different cells are received at the user equipment (UE) at different times, leading to negative side effects such as lower throughput and coverage due to time misalignment, constructive to destructive interference, and inter-symbol interference.
Innovation Solution
The technology aligns downlink symbol timing boundaries dynamically to ensure that UE receives signals from multiple cells at the desired time, using techniques like UE positioning data, uplink sounding reference signals, and channel state information to adjust transmission times, and modifies scheduling to avoid interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple cells transmit downlink signals simultaneously in CoMP mode, then received power and coverage are improved, but time misalignment causes interference and reduces throughput
Solution Approach 1:
The network performs preliminary timing alignment by adjusting the downlink transmission timing of cooperating cells based on UE position information and propagation delay calculations before actual data transmission, ensuring signals arrive simultaneously at the UE
Solution Approach 2:
The system dynamically changes the transmission timing parameter of downlink signals from different cells, adjusting the time offset to compensate for propagation delays and ensure synchronized arrival at the UE receiver
2Power
If multiple cells transmit downlink signals simultaneously in CoMP mode, then received power and coverage are improved, but time misalignment causes interference and increases energy consumption
Solution Approach 1:
The network performs preliminary timing alignment by adjusting the downlink transmission timing of cooperating cells based on UE position information and propagation delay calculations before actual data transmission, ensuring signals arrive simultaneously at the UE
Solution Approach 2:
The system converts the potentially harmful effect of time misalignment into a benefit by using the timing adjustment mechanism to achieve constructive interference, where misaligned signals that would cause interference are instead deliberately synchronized to reinforce each other, improving received power while reducing the need for retransmissions and associated energy consumption
3Reliability
If downlink frame boundaries are adjusted for timing alignment, then reception quality is improved, but scheduling complexity increases
Solution Approach 1:
The timing alignment mechanism serves multiple functions simultaneously: it synchronizes downlink signals from different cells, enables accurate UE positioning, and facilitates coordinated scheduling across cells, reducing overall system complexity despite the adjustments required
Solution Approach 2:
The system uses feedback from UE position information and uplink timing measurements to continuously adjust downlink frame boundaries, creating a closed-loop control mechanism that maintains reception quality while automating the scheduling complexity management
Data Source
AI summary
The technologies described herein are directed towards aligning the downlink symbol timing boundaries of coordinated multi-point (CoMP) transmitting radio units, so that a user equipment receives transmitted signals from each cell at generally the same time. In a CoMP scenario, synchronized downlink transmissions from a connected cell and a cooperating cell are generally not received at the same time by a target user equipment because of different propagation distances from the transmitting radio units; such misalignment leads to performance degradation. By offsetting the downlink symbol timing boundaries relative to each other, a targeted user equipment receives symbols at the desired time boundary, resulting in constructive interference that improves and a cell's downlink throughput and/or coverage. Time alignment via offset symbol timing boundaries also eliminates inter-symbol interference. Modified scheduling can be used to ensure that downlink and uplink transmissions from the coordinated radio units do not interfere with one another.