Optical Wireless Time Slot Allocation for Interference Asymmetry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical wireless communication systems, such as Li-Fi, face interference asymmetry between uplinks and downlinks, leading to sub-optimal resource allocation and increased interference due to asymmetrical coverage areas and radiation patterns.
Innovation Solution
A method for allocating time slots in optical wireless systems, where each terminal determines its coverage and reception information to optimize the quality of uplink and downlink connections, with a network controller managing available time ranges to minimize interference by allocating and deallocating time slots based on access point and terminal associations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the same time slot allocation strategy is used for both uplink and downlink, then the system operation is simplified, but interference is increased due to asymmetrical coverage areas and radiation patterns
Solution Approach 1:
The patent applies asymmetry by implementing different time slot allocation strategies for uplink and downlink directions. The network controller separately manages uplink and downlink time slots, allowing asymmetric resource allocation that matches the asymmetric interference patterns caused by different coverage areas and radiation patterns of access points and terminals.
Solution Approach 2:
The patent segments the time slot allocation process into separate uplink and downlink management. The network controller divides the available time resources into distinct uplink time slots and downlink time slots, enabling independent optimization for each direction based on their specific interference characteristics.
2Object-affected harmful factors
If frequency reuse pattern is adopted to reduce interference, then interference between peripheral cells is reduced, but spectral efficiency is decreased due to sub-band usage
Solution Approach 1:
The patent uses periodic time slot allocation where different time slots are assigned to different access points in a systematic pattern. This periodic structure allows frequency reuse across time, maintaining spectral efficiency while reducing interference through temporal separation of transmissions from adjacent cells.
Solution Approach 2:
The patent transitions from spatial frequency separation to temporal frequency reuse. Instead of using different frequency bands in space (frequency reuse pattern), the system reuses the same frequency resources in different time slots, adding a temporal dimension to resource allocation and improving spectral efficiency while managing interference.
3Object-affected harmful factors
If time domain separation is used to serve spatially separated users, then interference is eliminated, but a large number of optical sources must be deployed
Solution Approach 1:
The patent makes each optical source (access point) universal by enabling it to serve multiple terminals in different time slots. Instead of requiring dedicated optical sources for each user or cell region, a single access point can dynamically allocate time slots to multiple terminals, reducing the total number of optical sources needed while maintaining interference-free communication.
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 interference by optimizing time slot allocation based on the quality of connections, ensuring maximum quality for both uplinks and downlinks, thereby enhancing the overall performance of optical wireless communication systems.
Implementation Method 1
Each access is equipped with a modem coupled to a LED light source emitting in the visible range, the modem modulating the source power supply current so as to modulate the intensity of the light emitted
Implementation Method 2
This optical receiver receives the light signal, converts it into an electrical signal, demodulates it and recovers the transmitted data
Implementation Method 3
the dongle or the terminal itself is also equipped with an infrared diode, the data to be transmitted on the uplink being used to modulate the infrared signal
Implementation Method 4
The infrared signal is received by a photodiode mounted on the access point, and is then demodulated to transmit the data through the principal network
Data Source
AI summary
A method of allocating transmission time slots in an optical wireless system. Resources are allocated taking account of asymmetry of interference diagrams on uplink and downlink and adopting reuse of transmission intervals for each channel, in areas in which there is no interference. In some embodiments, the allocation method allows for relaying between access points through the network to take account of the fact that the access point providing the best uplink (or downlink) can be distinct from the access point associated with the terminal.