Wireless Network Time of Flight Interference Detection and Sub-Frame Adjustment

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Solution Overview

Problem

In wireless communication networks, time of flight interference occurs when distant base stations sharing frequencies cause interference due to delayed signal propagation, leading to potential interference during uplink and downlink sub-frames, especially in large networks where frequency reuse is necessary.

Innovation Solution

A method is implemented to identify and reduce time of flight interference by detecting interference, determining nearby base stations operating on the same frequency, and adjusting sub-frame durations based on calculated criteria to minimize interference, either by shortening the downlink sub-frame of the interference source or the uplink sub-frame of the interference destination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If base stations share common frequencies to increase network capacity, then network productivity is improved, but time of flight interference occurs causing signal quality degradation

Engineering Contradiction:

Improvenetwork capacityVSAvoidtime of flight interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of time of flight interference by monitoring uplink sub-frames for interference patterns. When interference is detected, the gateway proactively identifies potential source base stations and calculates time of flight parameters before the interference severely impacts communication, allowing preventive adjustment of sub-frame configurations

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts sub-frame parameters (duration, timing) based on calculated time of flight criteria. When interference is detected, the gateway modifies the configuration of downlink or uplink sub-frames for affected base stations, changing temporal parameters to prevent overlap and eliminate interference while maintaining frequency reuse

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If base stations are separated by large distances to avoid interference, then interference is reduced, but network coverage area and deployment flexibility are limited

Engineering Contradiction:

ImproveinterferenceVSAvoidnetwork coverage

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The system transitions from spatial separation (distance-based interference avoidance) to temporal separation (time-based interference avoidance). By adjusting sub-frame timing and duration in the time dimension, base stations can be placed closer in space while avoiding interference through coordinated time scheduling, enabling denser network deployment

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Object-affected harmful factors

If sub-frame durations are adjusted to reduce time of flight interference, then interference is minimized, but communication capacity may be impacted

Engineering Contradiction:

ImproveinterferenceVSAvoidcommunication capacity

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The system applies selective sub-frame adjustments only to affected base stations experiencing time of flight interference, rather than uniformly adjusting all base stations. The gateway identifies specific source and destination base stations involved in interference and modifies only their configurations, preserving full capacity for unaffected base stations

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system dynamically adjusts sub-frame configurations based on real-time interference conditions. When interference is detected, the gateway modifies sub-frame parameters for affected base stations; when interference subsides, normal configurations are restored. This dynamic adaptation maintains optimal capacity while eliminating interference only when necessary

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8068786B2Method for reducing time of flight interference in a wireless communication network

Publication Date: 2011.11.29 CLEARWIRE COMMUNICATIONS LLC

AI summary

A method for identifying time of flight interference in a wireless communication network is provided. The method includes detecting interference during a first uplink sub-frame at an interference destination base station, and transmitting a time of flight interference source detection request to a gateway, where the time of flight interference source detection request comprises a time of flight interference period. The method also includes determining one or more base stations in the vicinity of the interference destination base station, where the one or more base stations in the vicinity of the interference destination base station operate at a same frequency as the interference destination base station. The method further includes instructing the one or more base stations in the vicinity of the interference destination base station to re-transmit a preamble at least once in a downlink sub-frame, decoding a first preamble of a first interference source base station at the interference destination base station during a second uplink sub-frame, and identifying the first interference source base station based on the first preamble.