CDRE - Reducing Packet Error Rate by Utilizing Network Coding

• Main Authors: Yi-Fong Tseng, 曾翊峰
• Other Authors: Hsi-Lu Chao
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/72007670465481670896

碩士 === 國立交通大學 === 網路工程研究所 === 97 === Wireless signals have strong fading and interference effects, therefore they are unstable and unreliable compared with wired signals. The bit error rate (BER) grows when the signal-to-noise ratio (SNR) gets low. Various channel coding technologies in physical layer were designed to reduce BER under the same SNR. In IEEE 802 families, the packet error rate (PER) of MAC layer is decided by BER and packet length. That means PER will be fixed if BER and packet length are both decided. Larger packet length brings better performance in high speed networks. However, the PER grows with the increasing of packet length. To against PER to be high, IEEE standards specified the max packet lengths of various network technologies. This restricts the raising of packet length. In this thesis, we proposed a flexible coding scheme for delivery rate enhancement (CDRE) based on network coding, which brings a lower PER than before with the same BER. This scheme can be used to improve the delivery rate and throughput under a poor link quality, and applied to both traffic type of realtime and best-effort. Of course, it needs some additional memory and computations in return. Through the simulation, we will show that this scheme can reduce the SNR requirement of about 2.4dB for transmitting without any channel coding in physical layer, or 1.8dB in case of convolutional coding.