Moreover, the timing constraint set from HCCA scheduling is:
[ ] { }
,
max
,
,
1
, and : min ( )
( )
i
i j i
v
i ij l i j
L
v cl
g l ??? ???
?¤ + ?‹…
??? ??? ??? ?‰¤ p
p
p P . (16)
The two constraints of (15) and (16) can provide two bounds for the maximum number of
retries for each MSDU v for each link li,j. Since both the MAC-layer scheduling and the
application-layer deadline constraints are concurrently imposed, if
{ } ,
,
( )
, min ( ) 1 0 i j
v i j i
g l
i j L l
c l
??? ???
??’ >
p
we set the tightest bound for the maximum retry limit:
Cross-layer Optimized Video Streaming over Wireless Multi-hop Mesh Networks 114
total
,
total
1 deadline , , queue , 1 max
1
overhead 1 ,
( ) min{( )} ( )
min , 1
( )
i
i j i
i
i
i j i j v ijl j
v v
j i j
g l c l d d l
L L T
g l
??
??
??’
??? ??? =
??’
=
??± ??? ??? ??? ??? ??? ?‹… ??? ??? ??’ ??? ??? ??? ??? ?¤ = ??’ ??? ??? ??« ??¶ ??? ??? ??· ??? ??? ??¬ + ??· ??? ??? ??¬ ??·??· ??? ??? ??¬?? ??? ??? ??? ??? ???
??‘
??‘
p
p . (17)
Obviously, if there is no path pi for which
total 1 deadline
queue , 1 ( ) i
v ij j d d l ?? ??’
= > ??‘ then the
current MSDU may be dropped.
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