Constant Bit Rate Video Streaming via Multi-Stream Packet Management
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Solution Overview
Problem
Current WiFi standards, such as IEEE 802.11a, are not suited for video on demand in IFE systems due to non-constant bit rates and high error rates caused by 'microfading' phenomena, leading to delayed and error-prone video streaming on aircraft.
Innovation Solution
A method to stabilize the bit rate by using a combination of a main stream, a retransmission stream, and an advance stream, where packets are resent only after a certain time and if previously received packets are missing, ensuring a constant data rate for clients, and utilizing a negative acknowledgement mechanism to manage packet loss without impacting lower network layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If WiFi standards (IEEE 802.11a/b/g/n) are used for video on demand in IFE systems, then wireless communication and cabin configurability are improved, but bit rate stability and error rate deteriorate due to microfading phenomena
Solution Approach 1:
The data stream is segmented into three distinct streams: main stream (sent at constant rate D), advance stream (sent ahead of time), and retransmission stream (sent upon request). This segmentation allows the system to handle packet loss independently for each stream type, maintaining overall bit rate stability while enabling wireless communication
Solution Approach 2:
The advance stream sends data packets ahead of time before they are needed for playback. This preliminary action creates a buffer of pre-received packets, allowing the client to withstand temporary transmission failures without disrupting the constant bit rate requirement for video playback
2Reliability
If retransmission of lost packets is implemented, then error rate is reduced, but bit rate variability and delays increase
Solution Approach 1:
Different quality requirements are applied to different parts of the data stream. The main stream maintains strict constant rate D for immediate playback, while the retransmission stream handles lost packets with flexible timing. This local differentiation ensures that error correction does not disrupt the overall bit rate stability
Solution Approach 2:
The system uses a simple acknowledgment mechanism where the client requests retransmission of specific lost packets. Rather than implementing complex forward error correction or continuous retransmission protocols, the system uses lightweight, on-demand retransmission requests that minimize impact on overall transmission efficiency
3Manufacturing precision
If constant bit rate is maintained for video playback, then playback quality is improved, but ability to handle packet loss and retransmission deteriorates
Solution Approach 1:
The system dynamically adjusts the distribution of data across three streams based on real-time conditions. The main stream maintains constant rate D, while the advance and retransmission streams dynamically allocate remaining bandwidth. This dynamic allocation allows the system to adapt to packet loss conditions while maintaining constant overall bit rate for playback
Data Source
AI summary
A method is provided for sending data packets from a server to a client. A stream of data packets from the server to the client is composed of a main stream P, a retransmission stream R, and an advance stream A. P and A are fixed when R is zero. A is zero and the sum of P and R are fixed when R is not zero or when the client has accumulated data beyond a given threshold. A packet sent by the server but not received by the client is sent again to the client a given time after it was first sent. A packet sent by the server but not received by the client is sent again to the client only if the latter has already previously received a given number of packets sent by the server.