The Effect of Hybrid FEC/ARQ on Frame-Layer Rate-Control of TMN8 for Wireless Video Transmission
| Autor: | Chih-Hao Sun, 孫志豪 |
|---|---|
| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 Wireless channel transmission is known to suffer location-dependent, time-varying and burst errors. We study the problem of rate control for video transmission over wireless flat and slow Rayleigh fading channels, and use the hybrid ARQ retransmission scheme to improve the video quality. After receiving NAK information, sender needs time to retransmit the relative error packet. It will reduce effective channel throughput and the video encoder buffer may fill up quickly and lead the TMN8 rate-control algorithm to reduce the bit allocation of each frame and increase the number of skipped frame. We use a modified rate-control scheme that takes into consideration an a priori channel model, i.e. Gilbert channel model and channel feedback information, i.e., ACK/NAK to diminish the problem of filling up the encoder buffer and many skipped frames. After the acknowledgments received through the backward channel, we can estimate of the current channel states and use simplified Gilbert channel to predict the future channel throughput. We combine these two kinds of information from a priori channel condition and statistically predict the future channel throughput to reach our goal. The method we used to simulate channel transmission is GE model. GE model is the extension of Gilbert model. If we use channel code to protect data in the lower SNR, the parameter of GE model would also reflect the difference of with coding and without coding. When the received SNR becomes lower, the bit error probability would increase and the receiver would receive more erroneous data. We will consider using correcting ability of BCH code to increase effective throughput. Although it needs to decrease source data rate to form redundant bit to protect source data when channel condition become worse, it is worthy from comparison of the effective throughput between different code rate of BCH code in different SNR. From the comparison of the effective throughput, we could know that choosing which code rate of BCH code to encode source date in which SNR would be more effective. When the received signal is in lower SNR, we can use prediction model and coding method to see the difference of number of skipped frames, target number of bit and buffer fullness between with coding and without coding. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|