Staggercast Multicast Handover for Packet Loss Recovery
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Solution Overview
Problem
Existing video multicast/broadcast over IP-based wireless networks face significant packet loss during handovers, which current technologies, such as staggercasting, time-delayed data transmission, and cross-packet forward error correction, are unable to fully recover, leading to data loss and reduced system robustness.
Innovation Solution
Implementing a method called staggercasting, where data packets are repeatedly transmitted with a time shift, allowing mobile devices to switch to a delayed multicast group to recover lost packets, and optionally using lower bit rate or parity data generated by cross-packet forward error correction codes, ensuring seamless handover and backward compatibility with legacy devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data packets are transmitted during handover, then mobile devices can receive data, but packet loss occurs due to frequency switching
Solution Approach 1:
The system performs preliminary actions by transmitting duplicate data packets with time delays before handover occurs. The staggercasting mechanism pre-sends redundant packets that arrive at different times, ensuring that if packets are lost during handover, the delayed duplicates can compensate for the loss without requiring retransmission protocols.
Solution Approach 2:
The invention creates copies of data packets and transmits them through different channels (time-shifted streams). These duplicate packets serve as backups that can replace lost original packets during handover events, effectively using copying to mitigate packet loss without requiring complex error correction codes.
2Reliability
If staggercasting is implemented to recover lost packets, then system robustness improves, but bandwidth consumption increases
Solution Approach 1:
The system applies partial staggering by transmitting duplicate packets only for a limited time window during handover events, rather than continuously transmitting all packets with full redundancy. This partial action provides sufficient robustness during critical handover periods while minimizing bandwidth consumption during normal operation.
Solution Approach 2:
The invention dynamically changes transmission parameters by adjusting the time delay and redundancy level based on handover detection. During handover events, the system increases redundancy and applies staggercasting; during normal operation, it reduces or eliminates redundant transmissions, thereby adapting bandwidth usage to actual system needs.
3Reliability
If duplicate time-staggered streams are transmitted to tolerate signal loss, then robustness improves, but bandwidth usage increases
Solution Approach 1:
The system pre-transmits duplicate packets with time delays before handover occurs. These preliminary duplicate transmissions are scheduled in advance with specific time offsets, allowing the system to tolerate signal loss during handover without requiring excessive bandwidth during the critical handover period itself.
Solution Approach 2:
The staggercasting mechanism uses periodic time-delayed transmissions of duplicate packets. Instead of continuous redundant transmission, the system employs periodic duplicate packets at strategically chosen time intervals, providing robustness while minimizing overall bandwidth consumption through this rhythmic, scheduled approach.
4Loss of information
If FEC parity packets are sent with data packets to recover lost packets, then packet recovery capability improves, but bandwidth efficiency decreases when error bursts exceed FEC capability
Solution Approach 1:
The system pre-sends staggered duplicate packets before handover events occur, rather than relying on FEC parity packets that are sent alongside data. This preliminary action ensures that recovery packets are already in transit and can immediately compensate for losses without requiring additional bandwidth during the handover event itself.
Solution Approach 2:
Instead of using FEC parity packets that require mathematical decoding, the invention uses direct copies of original packets transmitted at different times. These copies can be directly substituted for lost packets without complex decoding operations, improving bandwidth efficiency while maintaining recovery capability for error bursts that exceed traditional FEC limits.
Data Source
AI summary
A method and apparatus are described for recovering from loss of an original data packet, including detecting data packet loss, joining a delayed multicast group, receiving a delayed data packet and using the delayed data packet to recover the original data packet that was lost. The delayed data packet is one of a copy of the original data packet, a copy of the original data packet encoded at a lower bit rate or a parity packet. Also described are a method and apparatus for staggercasting including encoding and compressing a first data sequence, packetizing the compressed encoded data sequence to form a data packet, multicasting the data packet to a first multicast group, encoding and compressing a second data sequence, packetizing the compressed encoded second data sequence to form a packet and multicasting the packet delayed by an offset time to a second multicast group.