CoMP Downlink Radio-Frame Offsets for Constructive Interference
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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 signal power and coverage are increased, but time misalignment causes destructive interference and reduces throughput
Solution Approach 1:
The network equipment performs preliminary timing adjustment by modifying the downlink frame boundary of the cooperating cell based on calculated time offset values before transmission. This preliminary action ensures that signals from multiple cells arrive at the UE in sync, preventing destructive interference and maintaining high throughput while achieving signal power enhancement through cooperative transmission
2Reliability
If downlink frame boundary is adjusted for time alignment, then signal reception quality is improved, but scheduling complexity and interference management difficulty increase
Solution Approach 1:
The system implements feedback mechanisms where the network equipment calculates time offset values based on UE positioning data, uplink sounding reference signals, and channel state information. This feedback loop enables dynamic timing adjustment that adapts to changing channel conditions, maintaining high reception quality while the network coordinator manages scheduling complexity centrally rather than at each transmitting cell
Solution Approach 2:
The network equipment acts as an intermediary that coordinates between multiple transmitting cells and the UE. It calculates the appropriate time offset values and frame boundary adjustments, then communicates these adjustments to the cooperating cells. This intermediary approach centralizes the complexity of timing management, simplifying the operation of individual cells while achieving precise time alignment at the UE
3Productivity
If dynamic timing alignment is implemented, then constructive interference is achieved and throughput increases, but processing requirements and power consumption increase
Solution Approach 1:
The system applies partial timing adjustment only to the cooperating cell's downlink frame boundary, rather than reconfiguring all cells. By adjusting only the necessary portion (the time offset value for the cooperating cell) and maintaining normal operation for the connected cell, the system achieves constructive interference and throughput improvement while minimizing additional processing requirements and power consumption
Data Source
AI summary
The technology described herein is 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.