Optical Wireless MAC Cycle Alignment via Out-of-Band Synchronization
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Solution Overview
Problem
In optical wireless networks, adjacent coordinators lack direct communication, leading to unsynchronized MAC cycles that cause interference with network devices in overlapping coverage areas, despite having aligned time slot durations.
Innovation Solution
A network device in the overlapping area derives timing information from downlink communication and sends it via an out-of-band channel to align MAC cycles of adjacent coordinators, using a line-of-sight optical channel for interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If coordinators use independent MAC cycles without direct communication, then device complexity is reduced, but synchronization accuracy deteriorates causing interference
Solution Approach 1:
A network device located in the overlapping coverage area acts as an intermediary to collect timing information from multiple coordinators and relay it back to them. This mediator enables synchronization between coordinators that cannot directly communicate, resolving the contradiction by maintaining simple coordinator structures while achieving accurate synchronization through the intermediary network device.
2Device complexity
If coordinators are synchronized using existing infrastructure routers/switches, then device complexity is reduced, but reliability deteriorates due to protocol support limitations
Solution Approach 1:
The network device performs self-service by autonomously collecting timing information from coordinators, deriving timing offsets, and relaying synchronization data without requiring external protocol support from routers or switches. This eliminates dependency on infrastructure that may not support synchronization protocols, thereby improving reliability while maintaining simple system structure.
3Object-affected harmful factors
If MAC cycles are aligned across adjacent coordinators, then interference is reduced, but loss of time increases due to synchronization overhead
Solution Approach 1:
The network device performs preliminary action by continuously monitoring and collecting timing information from coordinators in advance, maintaining a pool of timing data that can be quickly relayed when needed. This preliminary collection reduces the time required for actual synchronization operations, thereby minimizing synchronization overhead while effectively preventing interference.
Data Source
AI summary
In an optical wireless communication, OWC, network (100), time division multiple access, TDMA, is commonly used for interference suppression among multiple network devices (D1-Dn) associated to a single coordinator, or among adjacent coordinators (C1-Cn). However, an offset of MAC cycles among two adjacent coordinators (C1-C2) may still result in interference to a network device (D1) located in the overlapping area of the coverage areas of these two adjacent coordinators (C1-Cn). This invention is directed to various methods, apparatus, systems, computer program and computer-readable media for providing a mechanism to make use of an out-of-band channel to send a signal from a network device (D1) to the two adjacent coordinators (C1-C2), for assisting the alignment of MAC cycles among the two adjacent coordinators (C1-C2), and the out-of-band channel has a line-of-sight character, and is out-of-band as compared to the OWC network (100).