FEC for efficient video transmission over CDMA

Abstract

Video is one of the most important and also one of the most challenging types of traffic on communication networks. One of the challenges arises because communication networks can insert errors into video, and also compressed video is fragile in the presence of errors; that is a single error can propagate over a large portion of the video. This thesis describes how to protect the content of video during transmission by employing error correcting codes. It deals with the concept of transmitting video packets with redundancy embedded in it for attempting error recovery and improving the quality at the receiver side. The effect of bit errors on the overall video quality has been studied. This thesis throws light on the importance of each bit in a video frame to the overall received quality. The effect of the important bits has been monitored by performing a “bit killing” operation, wherein the critical bits are flipped. We have adopted BCH codes to improve the quality of video. Two types of FEC schemes have been implemented. In the first FEC scheme, data is not prioritized and various segments in the video stream are given equal importance. BCH (63, 51, 2) is used for this case. In the second scheme, a stronger FEC is applied to the first frame (the first I frame) as the important data is found in it. Hence BCH (63, 24, 7) is used for the first frame and BCH (63, 57, 1) is used for the rest inter frames. The main aim of the algorithm is to strengthen the video stream against most possible error cases and also reduce the percentage of the overhead bits arising because of BCH coding. The strength of the BCH is also varied to study the effect of signal-to-noise ratio on the BER. All discussions are furnished with simulation results. The primary target is the transmission of video through CDMA channels.