Intermodulation Interference Handling in Wireless Network Nodes
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Solution Overview
Problem
In wireless communication systems, intermodulation interference caused by nonlinear effects in radio frequency transmitters leads to reduced signal-to-noise ratio and coverage issues, particularly in multi-operator FDD RBS sites and carrier aggregation setups, where passive intermodulation products cannot be filtered out, resulting in decreased uplink sensitivity and potential dropped connections.
Innovation Solution
A method is introduced to reduce intermodulation interference by scheduling uplink transmission grants for a subset of stations within specific time intervals, limiting downlink transmissions during these intervals to minimize interference on the uplink carrier frequency band, while allowing normal transmissions outside these intervals, and adjusting timing to align with handover triggered RACH events, using a network node with a transceiver and transmission controller to manage these schedules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downlink transmissions are limited during specific time intervals to reduce intermodulation interference, then uplink signal quality is improved, but system productivity decreases due to reduced transmission opportunities
Solution Approach 1:
The patent implements periodic time intervals where downlink transmissions are limited to specific subframes (e.g., every 10th or 20th subframe) rather than continuously. This allows the system to periodically reduce intermodulation interference while maintaining normal operation during other time periods, thus balancing uplink signal quality improvement with system productivity maintenance.
Solution Approach 2:
The patent dynamically adjusts transmission scheduling based on detected interference conditions. The network node monitors for intermodulation products and adaptively applies transmission limitations only when and where needed, rather than using a static approach. This dynamic adaptation allows the system to optimize uplink signal quality while minimizing impact on overall system throughput.
2Reliability
If transmission limitations are applied frequently to maintain uplink sensitivity, then interference is reduced, but network performance deteriorates due to excessive transmission restrictions
Solution Approach 1:
The patent employs feedback mechanisms where the network node monitors uplink signal quality and interference levels continuously. Based on this feedback, the system determines when transmission limitations are actually needed and adjusts the scheduling accordingly. This feedback-driven approach ensures that transmission limitations are applied only when intermodulation interference is detected, maintaining uplink sensitivity without unnecessarily restricting network performance.
Solution Approach 2:
The patent changes operational parameters (transmission scheduling patterns, time interval durations, affected carrier selections) based on detected interference conditions. Rather than applying fixed transmission limitations, the system adjusts parameters dynamically - extending or shortening limitation periods, selecting different affected carriers, and modifying grant allocation patterns - to optimize both uplink sensitivity and network performance under varying conditions.
3Productivity
If normal downlink transmissions continue without limitation, then system capacity is maintained, but intermodulation interference increases and degrades uplink reception
Solution Approach 1:
The patent segments the transmission timeline into different types of subframes: normal subframes with full downlink transmissions, and limited subframes where downlink transmissions are restricted to reduce intermodulation. This segmentation allows the system to maintain high system capacity during normal subframes while periodically introducing limited subframes to mitigate interference, achieving a balance between productivity and harmful factor reduction.
Solution Approach 2:
The patent maintains continuous useful action by ensuring that uplink transmissions can occur without interruption during limited subframes, and by using cross-carrier scheduling to maintain downlink service continuity on unaffected carriers. The system continuously provides communication service while periodically adjusting transmission patterns to reduce intermodulation interference, rather than stopping transmissions entirely.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces intermodulation interference, maintaining system performance by limiting the number of occasions for reduced transmissions, thereby enhancing uplink signal quality and coverage, and minimizing the risk of dropped connections or reduced network satisfaction.
Implementation Method 1
The purpose of a transmitter in a digital wireless communication system is to convert a digital low-frequency baseband signal into an RF signal while preserving the modulation, and thereby the baseband information
Implementation Method 2
distortion products caused by nonlinearities in the transmitter may fall into the receive band and raise the over-all receiver noise figure
Implementation Method 3
external cavity filters may be used in radio base stations (RBS) to filter out unwanted components outside wanted transmission band
Implementation Method 4
passive intermodulation (PIM) products may be reflected back to or within the RBS site and fall into one of the operator's receive band
Data Source
AI summary
An approach of handling interference caused by inter-modulation in a network node for wireless communication capable of communication with a set of stations for wireless communication is disclosed. The stations are wireless transceiver devices and communication from the network node to any of the stations is considered to be downlink communication performed on a downlink carrier in a downlink carrier frequency band and communication from any of the stations is considered to be uplink communication performed on an uplink carrier in an uplink carrier frequency band. The method comprises, when an interference level indicates probable inter-modulation interference, scheduling uplink transmission grants for a plurality of stations of a subset of the stations within a time interval, such that scheduling outside the time interval is reduced. The uplink transmission grants are valid for the time interval, wherein the scheduling uplink transmission grants is performed by adapting a schedule for at least one station of the plurality of stations of the subset of the stations to fall within the time interval. The method further comprises transmitting the uplink transmission grant to the plurality of stations of the subset of stations, assigning limited transmissions on the downlink carrier frequency band at the time interval such that inter-modulation interference is reduced on the uplink carrier frequency band during the time interval, and assigning transmissions on the downlink carrier frequency band outside the time interval with less limitations than during the time interval. The approach comprises methods, network nodes, computer programs and network node sites.