In-band Modem Higher-Layer Protocol Message Handling
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Solution Overview
Problem
Existing communication systems face challenges in efficiently transmitting higher layer protocol messages through speech codecs due to bandwidth limitations and coding inefficiencies, particularly when attempting to support multiple layer acknowledgments, which increase bandwidth requirements and reduce data transfer rates.
Innovation Solution
The system employs an in-band modem to reliably transmit and receive higher layer protocol messages by using unique synchronization sequences to distinguish between low and high layer acknowledgement messages, allowing for efficient message identification without additional identifier bits, thereby reducing bandwidth overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple layer acknowledgments are transmitted through speech codec, then reliability of data transfer is improved, but bandwidth requirements increase and data transfer rate decreases
Solution Approach 1:
The patent combines multiple acknowledgment messages (low layer and high layer) into a single speech packet transmission. The in-band modem multiplexes different layer acknowledgments within the same speech codec bandwidth, allowing simultaneous transmission of multiple acknowledgment types without requiring separate dedicated channels for each layer, thus maintaining data transfer rate while improving reliability through comprehensive acknowledgment coverage.
Solution Approach 2:
The speech codec is designed to handle multiple functions simultaneously - it carries both voice traffic and multiple types of acknowledgment messages (low layer and high layer) through the same channel. The in-band modem provides universal bandwidth utilization by allowing different protocol layers to share the speech codec infrastructure, eliminating the need for separate dedicated channels and maximizing the utility of available bandwidth.
2Measurement precision
If additional identifier bits are added to distinguish message types, then measurement precision of message identification is improved, but bandwidth overhead increases
Solution Approach 1:
The patent employs distinct synchronization sequences that act as unique identifiers for different message types (low layer acknowledgment versus high layer acknowledgment). Instead of adding identifier bits to the message content, the system uses different synchronization patterns - analogous to using different colors - to signal the type of message being transmitted. This approach maintains precise message identification while avoiding additional bandwidth overhead from explicit identifier fields.
Solution Approach 2:
The synchronization sequence serves as an intermediary element that carries message type information without being part of the actual data payload. Rather than embedding identifiers within the acknowledgment messages themselves (which would consume bandwidth), the system uses separate synchronization sequences as mediators to convey message type information, thereby preserving bandwidth for actual data transfer while maintaining accurate message identification.
Data Source
Figure 1A
Figure 1B
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AI summary
Detecting an acknowledgment signal sent from a destination terminal at a source terminal in an in-band communication system is disclosed. A message identifier is stored at the source terminal. After receiving at the source terminal the link layer acknowledgement with a compressed high layer acknowledgement message, the high layer acknowledgment message is regenerated from the retrieved message identifier and the received compressed high layer acknowledgement message.