Adaptive Forward Error Correction for Video Delivery over Wireless Networks

• Main Authors: Yao-Ting Chung, 鍾耀霆
• Other Authors: 許健平
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/98592421461460963140

碩士 === 國立中央大學 === 資訊工程研究所 === 95 === With the advance of wireless network technologies, wireless multimedia applications can be widely used in the near future. The video transmission over wireless networks is an important and inevitable trend by providing handheld devices with the telecommunication technique. However, the wireless networks are not trustworthy and reliable. The video multi-media over the wireless network service will be filled with challenges. The forward error correction (FEC) usually reduces the errors of the wireless networks with high bit error rate (BER). The FEC sends out redundant data packets to recover the data errors. If we want to correct data during the wireless networks with higher BER, we need to send more redundant information. If the BER of wireless networks is high, the low-strength error correction coding does not offer notable improvement. On the other hand, the high-strength of error correction coding in low BER would waste network bandwidth. It is reasonable that using dynamic FEC adapts the variety of BER. For raising the power of forward error correction for video delivery over wireless networks, we present an adaptive forward error correction (AFEC) mechanism. In our AFEC mechanism, if the sender receives feedback information, it will decide whether the forward error correction transmission should be used or not. The AFEC would adjust the additional length (redundancy) of data according to the BER of wireless networks. The sender would not stop transferring data for waiting the feedback information. The result of the experiments reveals that the AFEC mechanism can improve the quality of video delivery over bad situations. The experiment comparison result shows that the image quality of AFEC obviously better than the image quality without FEC method. When PER is 0.2, The PSNR of AFEC mechanism is higher without FEC mechanism more than 10 db. The result shows that the image quality of AFEC mechanism almost the same with fixed FEC mechanism. However, AFEC mechanism cost less redundant packets obviously. When PER is 0.005, the AFEC mechanism only increase 6% redundancies. In the same situation, Fixed FEC mechanism still increase 100% redundancies. The AFEC provides a new method for transferring online video. We also suggest a mean frame corruption rate which estimates a video error rate. The user can set the optimal threshold value for AFEC according to different video quality level.