Authors:
Ray Kirk, Tim Crockett, Jonathan Nobrega, Jennifer Yen
Abstract:
This disclosure proposes a method for improving reliability in isochronous data transmission by transmitting redundant data streams that are intentionally time-shifted relative to one another. By leveraging redundancy and controlled delay, missing or corrupted data in one stream can be reconstructed from a corresponding segment in another stream without requiring retransmission. This approach avoids the latency, jitter, and unbounded buffering typically associated with conventional error-recovery protocols, enabling robust delivery of time-sensitive data such as audio, video, and sensor streams.
Background:
Isochronous data streams deliver data at a constant rate and are typically consumed at the same rate they are generated. Examples include audio playback, video streaming, and real-time sensor data.
Traditional error recovery methods, such as TCP retransmission, ensure data integrity but introduce variable delays due to packet reordering and retransmission. These delays result in jitter or buffering requirements that are unacceptable for real-time applications. Specifically:
- TCP requires buffering until missing packets arrive, introducing latency.
- Packet loss results in playback interruptions or stalls in time-sensitive systems.
- Buffering alone cannot recover data that was never received.
- Real-world environments (e.g., wireless or satellite links) introduce temporary outages that lead to unavoidable data loss.
Thus, there is a need for a recovery mechanism that preserves continuity of playback without introducing retransmission delays or requiring large buffers.
Description:
The invention introduces redundant transmission of identical data streams with a controlled time offset between them.
Core Mechanism
- A primary stream and one or more redundant streams are transmitted.
- Each redundant stream is delayed by a fixed time interval relative to the preceding stream.
- The delay interval is chosen to exceed the expected duration of typical transmission interruptions.
Receiver Operation
- The receiver processes the delayed stream as the primary playback source.
- Earlier (leading) streams are buffered.
- If data is missing in the delayed stream, the receiver substitutes the corresponding data from the buffered leading stream.
- Sequence numbers or timestamps ensure proper alignment and reconstruction.
Example: Satellite Audio
When a receiver temporarily loses signal (e.g., passing under a bridge), data may be lost in one stream. However, because another copy of the same data was transmitted earlier or later, the missing segment can be reconstructed seamlessly.
Example: UDP-Based Sensor Data
- Data is transmitted over UDP(User Datagram Protocol), which may lose or reorder packets.
- A redundant stream is transmitted on a separate port or channel with a fixed delay.
- The receiver uses sequence numbers to detect missing packets in the delayed stream.
- Missing packets are filled in using buffered data from the leading stream.
Trade-offs
- Introduces a fixed latency equal to the stream delay interval.
- Increases bandwidth usage due to redundant transmission.
- Provides deterministic recovery for outages shorter than the delay interval.
Scales with additional streams, though latency and bandwidth requirements increase accordingly.
Usages:
This invention applies to any system requiring reliable real-time data delivery:
- Satellite and terrestrial radio broadcasting
- Real-time audio streaming (VoIP, conferencing)
- Video streaming and surveillance systems
- Autonomous vehicle sensor networks
- Industrial control systems
- Medical monitoring systems
- Telemetry and remote sensing applications
Claims:
- A method for transmitting isochronous data comprising:
- generating a primary data stream;
- generating at least one redundant data stream containing identical data;
- introducing a fixed time delay between the primary and redundant streams;
- transmitting the streams over one or more communication channels.
- The method of claim 1 wherein the receiver:
- buffers at least one stream;
- detects missing or corrupted data in another stream;
- substitutes missing data using buffered data from the redundant stream.
- The method of claim 1 wherein the delay interval exceeds a predefined expected communication interruption duration.
- The method of claim 1 wherein sequence numbers or timestamps are used to align corresponding data segments across streams.
- The method of claim 1 wherein streams are transmitted over independent channels or network ports to reduce correlated loss.
- The method of claim 1 wherein additional redundant streams are used to increase fault tolerance at the cost of increased latency and bandwidth.
- A system implementing the method comprised of:
- a transmitter configured to generate and delay redundant streams;
- a receiver configured to buffer, align, detect errors, and reconstruct missing data.
Enabling Technology:
The invention can be implemented using existing and emerging technologies:
- Networking Protocols: UDP/IP, RTP, QUIC (without retransmission reliance)
- Timing and Synchronization: NTP, PTP (Precision Time Protocol)
- Buffer Management Systems: Circular buffers, low-latency memory structures
- Hardware Support: FPGA/ASIC-based stream duplication and buffering
- Sequence Tagging: Packet headers with timestamps or sequence IDs
- Error Detection: Checksums, CRC validation for packet integrity
TGCS Reference 4537
