On Channel-adaptive Error Con trol Techn ique V ideo Comm un ication

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1 21 10 V o l. 21 N o. 10 Con trol and D ecision O ct : (2006) ,, (, ) :,,.,,.,,. : ; ; ; : T P18 : A On Channel-adaptive Error Con trol Techn ique V ideo Comm un ication for W ireless W EN J ian2w ei, DA I Q iong 2ha i, J IN Y i2hu i (D epartm ent of A utom ation, T singhua U niversity, Beijing , Ch ina. Co rrespondent: W EN J ian2w ei, E2m ail: w enjw 02@m ails. tsinghua. edu. cn) Abstract: T he im po rtant issues of erro r contro l fo r video transm ission are discussed. A n adap tive erro r resilient schem e in transpo rt layer is p resented fo r enhancing the robustness. To op tim ize the transm ission efficiency w ith the lim itation of bandw idth and pow er consump tion, the erro r resilient schem e accounts fo r the characters of h igh erro r rate and tim e variability in w ireless video delivery, adjusts the percentage of the redundancy in the transpo rt packets adap tively, and perfo rm s the op tim al tradeoffs betw een th roughput, reliability and delay depending on the channel conditions. T he sim ulation results show a significantly im p roved visual perfo rm ance and transm ission efficiency fo r the transm itted video over a variety of w ireless channel conditions. Key words: V ideo encoding; W ireless video delivery; E rro r contro l; Feedback contro l 1 3 (3G), [1 ]. 3, [2 ]. 3.,,.., [3 ].,,., [4 ].,.,,. 1. (FEC)., FEC : ; : : ( ). : (1980 ),,,, ; (1964 ),,,,.

2 ,, FEC, [6 ]. (A RQ ), FEC,.,., FEC A RQ,, A RQ gfec [5 ]. FEC,,,., A RQ gfec.,,,,. 2,.,,.., A RQ gfec ;, ARQgFEC, 3,. 2 A RQ gfec.,,. 2,,, (A CK ) (NA CK). A CK NA CK,., A CK,NA CK ;, A CK NA CK,,, ;,,,..,,,.,. 2,.. 2 ARQgFEC

3 10 : ARQgFEC,.,.,,.. (FEC),. N, R, (R - 1) g2. (R - 1) g2,,,.,,,.,,.,.,,,,.,,,.,,.,,.,,,,.,.,,,,.,,,.,,.,,.,,.,,,,,..,,.,.,.,.,,.,.,,.,..,..,,,,.,. ;,.,.,.,,,.,,.,.,

4 ,, ;,.,,. 3,.,. ber per, N, r. rg2, NA CK, ;,, A CK,.,,,. ber, per : per = 1 - [ rg2 ] CN i (ber) i g (1 - ber) N - ị (1) i= 0, : rop t = m in{rgper perob j}. (2) : perob j,.,,. tavgobj, : tavgobj = perob j 1 - perob j. (3) 3G,, perob s.,, perob s (n - rttn) = 1 S m (n - i= 0 rttn - i). (4) : n ; rttn ; S ; m (i) i, 1 NA CK, ; 0 A CK,. s S, (4), s,,,.,,. tsh - su tsh - sd, tsh - tsh - u s ds.,, tsh - u s tsh - su, tsh - ds tsh - sd., perob s (n - rttn) = (perob s (n - rttn - 1) Β + 1 s m (n - rttn) ) Β. (5) : p erob s (n - rttn) = (perob s (n - rttn - s) Β s + 1 s- 1 s i= 0 m (n - rttn - i) g Β i ) 1 - Β 1 - Β s+ 1. (6) Β, , Β, Β,. perob s (1),, berob s. (2) n - rttn rop t (n - rttn).,,, rop t (n -, rttn) r (n) = rop t (n - rttn). (7),,., rop t (n - rttn) r (n) r (n) = rop t (n - rttn) + (rop t (n - rttn) - r (n - rttn) ) g2. (8), Χ, Χ= n p i= 1, t i t m ax (N - R i) n p N np + N ti i= 1. (9) : np, ti i, tm ax

5 10 : 1157, N, R i i., Χ , [7 ]. 6, 3G g(kbitgs) gs g(km gh) e23 3 Stream ing e23 3 Stream ing e24 3 Conversational e24 50 Conversational e24 3 Conversational e24 50 Conversational, 1 2, 9. 3e e23., : N = 255, np = 6 000, tm ax = 5, S = 1 000, s = 100, Β= 0. 95, perob j= 0. 05, tsh - su = 2. 5 perob j, tsh - u s = perob j, tsh - sd = 0, tsh - ds = 1. 5 p erob j., A RQ gfec,, 50 20,,. 36,., , 24, ARQ gfec,, , 2, , , , A RQ g FEC, ,. 3 ARQgFEC 4 ARQgFEC,, A RQ gfec : 1), ; 2),,.

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