There have been a number of papers focusing on fiber distributed sensing with coherent Rayleigh backscattering
published. However, up to now, very limited research articles on investigation of coherent Rayleigh backscattering signal
waveform and its physical mechanism have been reported. This paper first proposes a theoretical derivation to illustrate
coherent Rayleigh backscattering waveform. The theoretical model is then proved with numerical simulation and
experimental measurement. In addition, signal processing method is an important factor on the performance of a phasesensitive
OTDR system. An improvement of signal processing method, which is consisted of digital average, moving
average and interval subtraction, with good effect on locating external perturbation is also introduced.
This paper describes fixed-point design methodologies and several resulting implementations of the Inverse
Discrete Cosine Transform (IDCT) contributed by the authors to MPEG's work on defining the new 8x8 fixed
point IDCT standard - ISO/IEC 23002-2. The algorithm currently specified in the Final Committee Draft (FCD)
of this standard is also described herein.
This paper analyzes the drift phenomenon that occurs between video encoders and decoders that employ different
implementations of the Inverse Discrete Cosine Transform (IDCT). Our methodology utilizes MPEG-2, MPEG-4
Part 2, and H.263 encoders and decoders to measure drift occurring at low QP values for CIF resolution video
sequences. Our analysis is conducted as part of the effort to define specific implementations for the emerging ISO/IEC
23002-2 Fixed-Point 8x8 IDCT and DCT standard. Various IDCT implementations submitted as proposals for the new
standard are used to analyze drift. Each of these implementations complies with both the IEEE Standard 1180 and the
new MPEG IDCT precision specification ISO/IEC 23002-1. Reference implementations of the IDCT/DCT, and
implementations from well-known video encoders/decoders are also employed. Our results indicate that drift is
eliminated entirely only when the implementations of the IDCT in both the encoder and decoder match exactly. In this
case, the precision of the IDCT has no influence on drift. In cases where the implementations are not identical, then the
use of a highly precise IDCT in the decoder will reduce drift in the reconstructed video sequence only to the extent that
the IDCT used in the encoder is also precise.
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