FEC

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FEC
The Reed-Solomon Method
Project Members Alon Keren Sagi Linsker
Instructor Omer Gurewitz
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Whats today?

• Overview
• Reed-Solomon short review
• File-transfer by RS and UDP
• File encoding and packetizing
• File decoding and reassembly
• UDP considerations
• Application sending and receiving
• Sender side
• Receiver side
• Results
• 5. Future improvements

3
Overview
???? ?? ?? ???????? ????? ???????? ?????? ?????
????? (????? ?????? BMP) ??? ??? ?????? ??? ????
??-??????.
????????? ????? ??? ???????? UDP ??????? ??????
Reed-Solomon ?? ??? ?????? ?? ????? ?????? ?????,
??? ??? ?? ???? ?????? ????? ?????.
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Reed-Solomon
Reed-Solomon ???? ??? ?????? ?????? (FEC), ?????
?? ??? ????? ???? ????? ????? ??????, ?? ??????
?? ????? ??? ??????, ????? ???? ????
??????. ??? ??????? ?? ??? 3 ??????? m,n,k
?????? ?? ??? RS(n,k). ???? ??? ???????? ?? n
??? n 2m 1.
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RS encoding
????? ?-RS ????? ??????
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RS decoding
????? Reed-Solomon ????? ????? ?? ????? ?????? ??
?? ???? n-k ???????? ????? ???? ?-n.
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From symbols to packets
?????? ????, ??? ????????? ?????? ?? ?????
??????. ???? ????? ????? ?????? gtgt ???? ??????,
????? ????? ??? ????? ???? ??????? ???? ??????.
?????
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File encoding packetizing
??? ??, ?????, ???? ?? ????? ??????? ?? k ??????
????? PS ?? ???, ????? ?????? ????? ?????.
File
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File encoding packetizing
???? ???? ?? ???? ?????? ????? ?????? ???
?? ????? ?????? ?-symbols (?? ??? ????? m ??????).
????????? ???????? ????? ?-i ??? ??? ????????,
??????? ?-n ????????
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File encoding packetizing
Packet 1
Packet k
Packet 2
Packet k 1
Packet n
Symbol i
Symbol i
Symbol i
Symbol i
Symbol i
??? ????? ?????? PS/m ????????, ???? ?? ????? ??
k ?????? ??? ????? ?? PS/m ?????? ?? k
????????. ????? ??????? ????? ?? ????? ???
?????? ?????? ?-i ????? ?????? ?-symbol ?-i ???
??? ?-PS/m ???????. ??, ??????? k ?????? ?????
???? ?-n, ?? ??? ????? ?? k ??????? ????????.
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File decoding reassembly
n packets
Original packets
Redundant packets
???? ????
??????
Original packets
????? ?? ????? ???? ?? ???? ?? ??????. ?????
??????? ?????? ?? ????? ?????? ?????, ????? ????
???????.
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UDP considerations

• ????? ????????? ??? ???? ?-UDP ????? ???????
  ????? ??????
• ????? ?????? ???? ????? ?? ??? ??????
  Reed-Solomon.
• ??? ?????? ??? ????? ????? ?? ??? ??? ???? ??
  ??? ????? ???? ????? ?????? ??? ?????.
• ????? ?????? ?????? ????? ???? ??? ?????- ???? ??
  ??? ????? ????? ?? ?? ??? ???? ??? ????? ???????
  ??? ?????.

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UDP considerations (Cont.)

• -???? ????? ??????? ????? ?? ??? ???? ????? IP
  ????? ????? ?- port ??? ????? ???? ?????. ?????
  ????? ???? ????? ??????? ??
• Min IP length IP Header length UDP
  Header length,
• Sender buffer-size,
• Receiver buffer-size
• ????? ?? ???? ????? ????? ????? ???? ??? ???
  ???? ???? ????? ????? (?? ????? ??? ?????? ??
  ???? ??? ????? - ?? ??? ????? ???? ????? / ?????
  / ??????)

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Sender side
????????? ???
GUI - send
????? BMP Header
????? ?????? ??????? ?? ????? ??????
????? ?????? ???????
????? ???????
????? ????? ????
????? ?????
- ????? ???????? (????? ????) n, k, Packet Size,
File Size, File Type (BMP/TXT)
- ????? header ?? BMP ????? ?? ??? ?????? ????
?????? (?? ?? ??????) ??? ?????.
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Sender side (Cont.)
????????? ???
GUI - send
????? BMP Header
????? ?????? ??????? ?? ????? ??????
????? ?????? ???????
????? ???????
????? ????? ????
????? ?????
????? ?????? ??????? ????? ??????. ????????
????? ???? ?? ????? ???? ??? ???? ?????? ??
???????? ????? ???? ?? ???? ????? ???. ????????
????? ???? ????? ?? ??????? ???????? ????? ???
????? ?????? ??????? ???????? ??????? ?????????
??????. ??? ????? ????? header ?????? ?? ????
????? ?? ??? ????? ??? ?????? ??.
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Sender side (Cont.)
????????? ???
GUI - send
????? BMP Header
????? ?????? ??????? ?? ????? ??????
????? ?????? ???????
????? ???????
????? ????? ????
????? ?????

• ???? ?????? ????? ?????? ?? ??
• EPB Errors per Block
• ???? ?????? ??? ???? ??? ????? ????
• PER Packet Error Rate
• ??????? ????? ?????

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Receiver side
GUI - receive
????? ????????
???? ??????? n, k Packet Size File Size File
Type (BMP/TXT)
????? ?????? ????? ????????
???? Header ???? ???? BMP.
???? ??????? ???? ????.
????? ??????
- ???? ???????? ???? ?????? ?????? ????? ???????
???? ?????? ?? ??? ????.
????? ?-header ????? ?????? ????? ?????? ??? ??
????? (??????) ??????.
- ?????? ??????? ????????, ?????? ??? ???? ??????
??????? ?? ????? ?? ?? ??????.
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Receiver side (Cont.)
GUI - receive
????? ????????
???? ??????? n, k Packet Size File Size File
Type (BMP/TXT)
????? ?????? ????? ????????
???? Header ???? ???? BMP.
???? ??????? ???? ????.
????? ??????
- ???? ????? ????? k (???? n) ?????? ???? ???????
(??? ?? ?? ??? k ??????? ????????).
????? ?-header ????? ?????? ????? ?????? ??? ??
????? (??????) ??????.
- ???? ??? ?? ????? ?????? ??????? ??????.
??????? ???? ??????? ???? ??????? ?? ??? ?????
???? ????? ?????, ???? ????.
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Results
????????? ??? ????? ?????

• ?????? ??????? ???? ???????.
• ?????? ??????? ??? ??????.
• ???? ??????? ??????? ?????? ???? ?? ???????
  ??????.
• ???? ??????? ??? ??????.
• ???? ????? ??????? ??????.

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Future improvements

• ????? ?-bursts ?? ??? ????? ?? ???? ???????
  ???????? ????? ???? ????? (interleaved)
• ??????? ???? ???? ????? ????? n ?-k ???? ?????
  ??????? ????.
• ????? ?- Multicast

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?????

• ???? ??????'
• ?? ?????
• ???? ????
• ???? ???-??

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The End