| Summary: | Intrabuilding electric power distribution lines provide easy access and universal coverage for digital
speech communications. However, power line communication channels exhibit unpredictable and variable
levels of signal attenuation and noise. To enable effective communication requires appropriate forward
error correction of the encoded speech.
This thesis describes the design, implementation and testing of synchronization, voice compression
and forward error correction algorithms required to achieve a robust real-time communication link across
power line channels. Communication was connection oriented and synchronous with a selectable baud
rate of 9600 bps or 19200 bps. Synchronization (delineation) was accomplished using a seven bit
synchronization marker placed between frames of encoded speech. The encoded speech data was
generated using the U.S. digital cellular standard VSELP 7950 bps voice encoder. Error detection and
correction bits were added to the speech data to produce aggregate data rates of approximately 9600 and
19200 bps. Error detection of the perceptually significant bits was provided through the use of a seven
bit CRC in the 9600 bps encoded speech. The 19200 bps scheme employed an error detection/correction
scheme where the amount of protection was based on the perceptual significance of each parameter.
The synchronization algorithm was implemented in hardware and tested. Synchronization was
maintained at bit-error rates (BERs) greater than 0.1. Subjective testing of the synchronization algorithms
under random noise indicated that the 9600 and 19200 bps coding schemes were usable with channel
BERs up to approximately 7x10⁻³ and 2x10⁻², respectively. Tests performed on actual power line
communication channels indicated approximately equal performance using either the 9600 or 19200 bps
coding scheme, due to the comparatively higher BER of the 19200 bps channel. === Applied Science, Faculty of === Electrical and Computer Engineering, Department of === Graduate
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