1. FEC coding scheme in Multi-hop Wireless Networks 2010.3.8 Koh Choi Networked Media Laboratory Dept. of Information & Communications Gwangju Institute of Science & Technology (GIST) 1

2. 2 Classification of coding scheme(1/2)  Block codes Hamming, BCH, RS, Golay, Algebraic geometric codes, LDPC codes  Tree codes Convolutional codes, Turbo codes, Tornado codes

3. 3 Classification of coding scheme(2/2)  Fountain codes LT-codes, Raptor codes (Rateless codes) k packets of a file can potentially generate limitless encoded packets; once you receive any k(1+α) packets regardless of the order (α is a small fraction < 1, especially when k is large), you can quickly reconstruct the original file.

4. 4 Raptor codes  Raptor codes Fountain codes  Consist of precode and LT code Redundant data

5. 5 FEC scheme in Wireless channels  Wireless channels Bursty error channel Tree codes: Convolutional codes Each symbols have dependent RS code More strong in bursty channels

6. 6 Complexity comparison Enc Time: Tornado = Raptor< LT < RS codes Dec Time: Tornado < Raptor < LT < RS codes RS: O(k) per encoding and decoding Tornado: O(1) per encoding and decoding Raptor: O(1) per encoding, O(k) per decoding

7. 7 RS VS. Raptor  Reed Solomon codes General FEC scheme in Multi-hop wireless networks Fixed symbol size  Raptor codes IPTV, DVB-H multimedia broadcasting service Multicast and broadcast in wireless networks Variable symbol size Actually Raptor codes is more powerful than RS codes in general sense.

8. 8 Discussion  Bandwidth problems in wireless channel Raptor codes: infinite output symbols RS codes: fixed output symbols Impact of Raptor and RS in multi-hop wireless channel?  Real comparison of Raptor and RS codes Recovery probability in each hop Recovery probability in burst error channel Coding overhead  Not determined in multi-hop wireless networks  In my approach, RS codes 접목  FEC 기법 자체가 아닌 FEC 가 적용된 비디오 전송이 주요 연구 주제  General approach  Issue Compare and analyze performance evaluation of FEC coding schemes in wireless channel (WMNs, Multicast, WLANs …) – is a valid approach?