FSO Transmission Protocol Controller for Lossy Link Throughput
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Solution Overview
Problem
Free-space optical communication systems face challenges in maintaining reliable data transmission over lossy links due to atmospheric conditions like scintillation, which can cause network fades and reduce bandwidth, and existing protocols like TCP Reno incorrectly interpret these conditions as congestion, leading to reduced throughput.
Innovation Solution
Implementing a transmission protocol controller that encapsulates network packets using a reliable ordered delivery protocol with retransmission and an alternate congestion algorithm, such as TCP Westwood+, to optimize throughput over lossy links, and adding latency buffers to smooth throughput during network fades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TCP Reno protocol is used for data transmission over FSO link, then standard congestion control is provided, but throughput is reduced due to incorrect interpretation of atmospheric conditions as congestion
Solution Approach 1:
The patent modifies the congestion control parameters and algorithms from standard TCP Reno to TCP Westwood+, changing how congestion is detected and responded to. This parameter change allows the system to distinguish between atmospheric losses and actual network congestion, maintaining high throughput while preserving reliability over FSO links
Solution Approach 2:
The patent implements enhanced feedback mechanisms that provide detailed information about link conditions to the congestion control algorithm. This feedback enables TCP Westwood+ to differentiate between atmospheric scintillation effects and true congestion, allowing appropriate throughput maintenance while ensuring reliable delivery
2Reliability
If retransmission protocol is used to ensure ordered delivery, then data reliability is improved, but bandwidth is reduced due to retransmission overhead
Solution Approach 1:
The patent employs selective acknowledgment (SACK) options that allow the receiver to pre-identify which packets are missing and notify the sender in advance. This preliminary action enables more efficient retransmission by avoiding unnecessary retransmission of already received packets, thus preserving bandwidth while ensuring ordered delivery reliability
3Reliability
If standard congestion control algorithms are used, then congestion avoidance is provided, but throughput is reduced during network fades caused by atmospheric conditions
Solution Approach 1:
The patent changes the congestion control algorithm parameters from TCP Reno to TCP Westwood+, which uses different thresholds and response mechanisms. This parameter change enables the system to maintain higher throughput during atmospheric network fades by not over-reacting to temporary signal degradation that is not actual congestion
Solution Approach 2:
The patent implements dynamic adaptation of congestion control behavior based on link conditions. TCP Westwood+ dynamically adjusts its congestion window and slow start threshold based on measured throughput and loss patterns, allowing it to maintain optimal performance during atmospheric fades while still providing effective congestion control when needed
Data Source
AI summary
A free-space optical (FSO) transceiver can include a transmission protocol configured to encapsulate outgoing network packets in by employing a reliable ordered protocol that relies on retransmission of lost data to form outgoing encapsulated packets. The transmission protocol controller can be configured to employ a congestion algorithm that optimizes throughput over a lossy link. The FSO transceiver can also include a transmitter configured to provide an output optical signal corresponding to the outgoing encapsulated packets over an FSO link.