t RN p aeta ap t

1
????? t?? RN p?? ?aµß??eta? ap? t?? ?
SNB RNB - n
SNB RNB n - 1
RNB - n SNB RNB n - 1
2
Modulus m 2n ??a t?? ep??e?t??? epa?a??pt???
ARQ
n 4 SNB 0 1 2 3 4 5 6 7 RNB
4 m n 1 5 (?p?s??????s? ?at? 4) SNB
mod 5 0 1 2 3 4 0 1 2 RNB mod5 4 m
4 SNB mod 4 0 1 2 3 0 1 2 3 RNB mod 4
0 m 2n 8 (ep??e?t??? epa?a??pt???
ARQ) SNB mod 8 0 1 2 3 4 5 6 7 RNB mod 8
4
ap?de?t?
a??????ta?
ap????e???ta?
3
?p??e?t??? epa?a??pt??? ARQ µe n 2ß 2 ?a?
µ??µ? d??t? ??a ß 1 pa??ta
????µe µe??s? t?? µetaß??t?t?ta? t??
?a??st???s??.
4
Data Link Control (DLC)

• T?µata
• ?????e?s? esfa?µ???? bits, a???aµ?? ap? s???µata
  e?te ??t??ta? ?a ?a?aµetad??e? t? p?a?s??, e?te
  µe ape??e?a? d?????s?.
• ??a?s??p???s? ?a????sµ?? (DLC ??pt?) t?? a????
  ?a? t?? t????? ???e p?a?s???.

5
?????e?s? sfa?µ?t?? se µ?a a???????a bits

• ?p???ste?? p??s?es? bit e?????? ?s?t?µ?a?
  (parity check). (?????sµa t?? bits mod
  2) 1 0 1 1 0 1 0 0 sk-1 s0
  s1 c ?????e?e? ???e pe??tt? a???µ? ?a???.
• ?e?t??s? p??s?es? pe??ss?te??? bits e??????
  ?s?t?µ?a?. p.?. ??????t??? ?a? ???et?? ??e????
  ?s?t?µ?a? 1 0 1 0 0 1 0 1 1 1 0 1 0
  1 0 0 0 1 1 0 1 1 0 0 0 0 0 1 1 1
  0 1 1 0 1 0 0 1 0 1 1 1 0
  1 0 1 0 0 0 1 1 0 1 1 0 0 0 0 0 1
  1 1 0 0 ?????e?e? ???e 3-?da ?a??? ?a?
  ???e pe??tt? a???µ? ?a???.

s?µß???se???
?s?t?µ?a
??????t??? ??e????
???et?? ??e????
6
?p?d?t???t?ta e??? ??d??a e??????

• ?????st? ap?stas? ? e????st?? a???µ?? sfa?µ?t??
  p?? µp????? ?a pe??s??? ????? ?a a????e?????.
• ??a bit e?????? ?s?t?µ?a? 2.
• ??????t??? ???et?? ??e???? ?s?t?µ?a? 4.
• ???at?t?ta a????e?s?? µa????? ?a??? (burst
  detecting capability) t? µ???? t?? µa????? ?a???
  e??a? ? a???µ?? t?? bits ap? t? p??t? µ???? t?
  te?e?ta?? ?????.
• ??a bit e?????? ?s?t?µ?a? 1.
• ??????t??? ???et?? ??e???? ?s?t?µ?a? µ????
  ??aµµ?? 1.
• ???a??t?ta ?a ?e????e? ????? ???? µ?a t??a?a
  a???????a ap? bits.
• Ge????

7
???????? ??e?????? ??d??a? ??????? (Cyclic
Redundancy Check Code CRC)
S(x) sK-1xK-1 sK-2xK-2 s1x s0 C(x)
e??a? t? ?p????p? t?? d?a??es?? t?? S(x) xL µe
??a ?e???t??? p??????µ? g(x). C(x)
Remainder ?a??de??µa string 101111, ???s? L
2 bit e?????? ?a? g(x) x2 x x7 x5
x4 x3 x2 x2 x x7 x6 x5 x4
x2 1 x6 x5 x4 x3 x2 x6
x5 x4 x3 x2 x4
x3 x2 x2
x Te????10111110 x ? C(x) c1 1,
c0 0
CRC
8
???????? ??e?????? ??d??a? ??????? (CRC)
??apa??st??µe ta bit ded?µ???? ?a? ta bit e??????
µe p??????µa S(x) xL sK-1xKL-1 sK-2xKL-2
s1xL1 s0xL cL-1xL-1 cL-2xL-2
c1x c0 p.?. bit ded?µ???? 101111 ?
? S(x) x5 0 x4 x3 x2 x 1 (K6)
???????? pa??t? S(x) xL C(x) p.?. 101101
10 (?6) (L2) ???????µ? p?? a?t?st???e? se
???????? pa??t? S(x) xL C(x) x7 0 x6
x5 x4 x3 x2 x 0 K6 L2 ??a??e?ta?
µe t? g(x).
s?µß???se???
?s?t?µ?a
9

• S(x) xL Q(x) g(x) C(x)
• S(x) xL C(x) S(x) xL C(x) Q(x)
  g(x)
• ?? p??????µ? p?? a?t?st???e? st? p?a?s?? p??
  st???e? ? (p?µp??) DLC d?a??e?ta? µe t? ?e???t???
  p??????µ? g(x).
• ?ta? ? ?aµß???? DLC ?aµß??e? ??a p?a?s?? e????e?
  a? t? p??????µ? p?? t?? a?t?st???e? d?a??e?ta? µe
  t? g(x).
• A? t? ?p????p? R(x) 0, t?te ?p???te? ?t? t?
  p?a?s?? de? pe????e? ????.
• ?? t? ?p????p? R(x) ? 0, t?te a????e?e? ????.

10
?a??asµ??? ap?d???
SC 1 0 1 1 1 1 1 0 M 1 0 0 1 1 1 1 1 sf??µa
0 0 1 0 0 0 0 1 ? ?(x) x5 1 eKL-1 e2 e1
e0 (p??????µ? sf??µat??) ?(x)
eKL-1xKL-1 e1x e0 st???eta? S(x) xL
C(x) ? d?a??e?ta? µe t? g(x) ?aµß??eta? S(x)
xL C(x) E(x) ???sµ?? M(x) O d??t??
?p??????e? R(x) o??sµ?? Remainder

Remainder ????µe ?a??asµ??? ap?d??? ?ta? t?
g(x) d?a??e? t? E(x) ?a? e??a? E(x) ? 0.
p.?. ?? g(x) x2 x ?a? ?(x) x2 x, x3
x2
s?µß???se???
11
Id??t?te? t?? ??d???? CRC

• St?? p?a?µat???t?ta ? ep????? t?? g(x) ???eta? ??
  e???
• g(x) (xL-1 1) (x-1)
• xL gL-1xL-1 g1x 1
• ?????st? ap?stas? 4.
• ???at?t?ta a????e?s?? µa????? ?a??? L.
• ???a??t?ta ap?d???? t??a??? s?µß???se????
  2-L.

p??t??e??? (primitive) p??????µ?
12

• E????st? ap?stas? 4
• ?p??e? ?a a????e??e? ???e pe??tt?? a???µ??
  ?a??? ?? t? ?(x) d?a??e?ta? ap? t? g(x), t?te
  E(x) q(x) g(x) p.?. E(x) x5 x3
  x2, E(1) 1 ???? g(1) 0 af?? ??a x1
• e??a? x 1 0, ?p?te E(x) ? q(x) g(x)

(pe??tt?? a???µ?? ?a???)

• ??a p??t??e??? p??????µ? de? d?a??e? t? p??????µ?
  xn 1 a? n lt 2L 1 2 ???? ?(x) xi
  xj xj ( xi-j 1) i - j lt K L ( s??????
  lt 2L )
• KL µ???? p?a?s???

13
???at?t?ta a????e?s?? µa????? ?a??? L E(x)
xmb-1 a2xmb-2 ab-1xm1 xm
xm (xb-1 a2xb-2 ab-1x 1)
de? e??a? d?a???s?µ? ap? t? xL gL-1xL-1
g1x 1 ,a? b-1 lt L. ?p????? ?a
a????e????? µa???? ???? µ????? b L.