Index Assignment for Multiple Description Quantization over Mobile Ad Hoc Networks

• Main Authors: I-Te Lin, 林宜德
• Other Authors: Wen-Whei Chang
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/45470108245396556584

碩士 === 國立交通大學 === 電信工程系所 === 94 === This study addresses the index assignment optimization for multiple description quantizers and its application to distributed speech recognition over Mobile Ad Hoc Networks (MANET). In the encoder, the speech parameters are quantized and mapped to two or more descriptions according to a predefined index assignment. After being transmitted over multiple independent channels, the decoder uses the received descriptions to reproduce the speech parameters. The optimization criterion and a practical approach based on the multiple description binary switching algorithm (MD-BSA) are first presented for the index assignment optimization. The basic idea of the MD-BSA is to switch a pair of codevectors recursively until the expected channel distortion can not be further reduced. In order to reduce its computational complexity, we formulated the index assignment problem on the basis of a linear programming framework and then proposed a fast local search algorithm based on the multiple description Hungarian algorithm (MD-HA). Experiments on the Mandarin digit string recognition task show that the proposed multiple description scheme outperforms single description methods in the presence of random and Gilbert-model packet losses. The ns-2 based MANET simulation was also conducted to examine the performance of the proposed multiple description transmission scheme.