In-band Modem Pulse-Position Modulation for Speech Codec Data
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Solution Overview
Problem
Existing speech codecs are inefficient in transmitting non-speech data due to coding inefficiencies, particularly when dealing with signals that do not exhibit periodic or noise-like characteristics, leading to severe distortion and limited data rate capabilities.
Innovation Solution
The use of an in-band modem to transmit non-speech information through a speech codec by converting data into noise-like signals and employing synchronization signals to ensure reliable detection, utilizing techniques such as pulse-position modulation and pseudorandom noise sequences to improve encoding and decoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If speech codecs use analysis by synthesis techniques with limited parameters to model speech signals, then speech coding efficiency is improved, but the ability to encode non-speech signals is degraded
Solution Approach 1:
The patent transforms the encoding approach by changing the nature of the input signal parameters. Instead of directly encoding non-speech signals with speech-optimized parameters, the system modulates data onto audio tones that mimic speech signal characteristics, allowing the speech codec to process them effectively. This parameter transformation enables the speech codec to handle non-speech data while maintaining its speech optimization.
Solution Approach 2:
The patent introduces audio tones as an intermediary between the data to be transmitted and the speech codec. These tones serve as a bridge, converting digital data into a form that resembles speech signals, which the speech codec can then encode efficiently. The tones act as a mediator that translates non-speech information into speech-compatible format.
2Loss of energy
If vocoders use limited parameters to model speech signals, then transmission bandwidth is reduced, but detection accuracy for tone signals is degraded
Solution Approach 1:
The patent employs periodic audio tones at predetermined frequencies to represent data. These periodic signals provide clear, distinguishable patterns that can be detected even with limited vocoder parameters. The periodic nature of the tones creates consistent spectral signatures that improve detection accuracy while maintaining bandwidth efficiency.
Solution Approach 2:
The system changes the representation of data from direct digital encoding to frequency-based audio tone modulation. By mapping data to specific frequency parameters of audio tones, the system creates detectable spectral features that work well within the constraints of vocoder parameter limitations, thereby maintaining detection accuracy.
3Productivity
If data transmission rate is increased by changing tones quickly, then productivity is improved, but vocoder modeling capability is degraded
Solution Approach 1:
The patent implements dynamic tone switching where the frequency and timing of audio tones are varied according to the data being transmitted. This dynamic approach allows higher data rates by changing tones more frequently, while the systematic modulation scheme ensures that even rapid changes can be tracked and decoded accurately, maintaining reliability despite increased speed.
Solution Approach 2:
The system uses predetermined frequency tones that are established before transmission begins. These pre-defined frequency assignments allow the receiver to anticipate and correctly interpret tone changes, maintaining accurate detection even when tones change rapidly. The preliminary establishment of frequency mappings supports higher transmission rates without sacrificing reliability.
Data Source
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AI summary
A system is provided for transmitting information through a speech codec (in-band) such as found in a wireless communication network. A modulator transforms the data into a spectrally noise-like signal based on the mapping of a shaped pulse to predetermined positions within a modulation frame, and the signal is efficiently encoded by a speech codec. A synchronization sequence provides modulation frame timing at the receiver and is detected based on analysis of a correlation peak pattern. A request/response protocol provides reliable transfer of data using message redundancy, retransmission, and/or robust modulation modes dependent on the communication channel conditions.