Post on 04-Feb-2016
description
transcript
Computer Networks:Wireless Networks
Ivan Marsic
Rutgers University
Chapter 6 – Wireless Networks
Wireless Networks
Chapter 6
Topic:Mobile Ad-hoc Networks
(MANETs)
Ad-hoc Network Definition Routing Protocols
Dynamic Source Routing (DSR) Ad Hoc On-Demand Distance-
Vector (AODV)
Ad-hoc Networks
• Each mobile device (node) can act as a router• Links form and break based on mobility and
environmental factors• Connectivity (e.g., high probability of instantaneous
end-to-end paths existing) is assumed
Mobile Ad-hoc Networks (MANETs)
Physical wireless links Network topology
A
B
D
E
F
C
TransmissionTransmissionrangerange
A
B
D
E
F
C
(a) (b)
A
B
D
E
F
C
packet packet
C E
F
B
A D
Network Layer Notation vs.Link Layer Transmissions (1)
Network Layer Notation vs.Link Layer Transmissions (2)
C
B
E
FA D
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B
E
FA D
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FA
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FA
packet packet
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packet packet
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Network layer (t)
Link layer (t1)
Link layer (t2)
Link layer
Network layer
Link layer
Network layer
Multihop Throughput
Challenge: more hops, less throughputLinks in route share radio spectrumExtra hops reduce throughput
Throughput = 1
Throughput = 1/2
Throughput = 1/3
Ad-hoc Networks
• Goal: Nodes within the network can send data between themselves.
• Challenges:– No centralized coordinator to help routing– No “default route” for nodes within the network– Fast topology changes– Limited bandwidth – can’t have too much overhead
S
D
Ad-hoc Networks
• Nodes that want to route messages must:– Find out about the topology of the network– Use that topology to do something with the
message
Control PlaneControl Plane
Data PlaneData Plane
S
D
Routing Protocol Categories
• Proactive:– Nodes actively maintain and share topology
information, regardless of if there is data to send– Generally timer- or event-based
• Reactive (On-demand):– “Lazy” approach: Don’t do more work then you
have to– Only discover topology/routes when there is data
to send
Control PlaneControl Plane
Routing Protocol Categories
• Local next-hop forwarding:– Consult forwarding table for a next hop– Completely local decision
• Source routing:– Source node places complete path in packet
header– Intermediate nodes don’t have to consult their
forwarding tables
Data PlaneData Plane
SS AA BB DD
A B D
Reactive Protocols
• Names are useful hints at understanding the protocol properties:
Ad-hoc On-demand Distance Vector (AODV)Ad-hoc On-demand Distance Vector (AODV)
Dynamic Source Routing (DSR)Dynamic Source Routing (DSR)
Source RoutingSource Routing
Next-hop ForwardingNext-hop Forwarding
Distance VectorDistance Vector
ReactiveReactiveMANETMANET
MANETMANET
14
Dynamic Source Routing (DSR)
• When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery.
• Source node S floods the network with route request (RREQ) packets (also called query packets).
• Each node appends its own address in the packet header when forwarding RREQ.
Route Discovery in DSR (1)
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E G
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LA
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Route Discovery in DSR (2)
Broadcast RREQ[C]
Represents a node that has received RREQ for H from C
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C
B
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E G
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LA
RREQ[C]
RREQ[C]
Route Discovery in DSR (3)
F
C
B
D
E G
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KJ
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LA
RREQ[C, E]
RREQ[C, B]
Route Discovery in DSR (4)
C
B
D
E G
H
KJ
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Y
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LA
RREQ[C, E, G]
RREQ[C, B, A]
RREQ[C, B, A]
F
Route Discovery in DSR (5)
Unicast RREP[C, E, G, H]
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C
B
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KJ
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A
RREP[C, E, G, H]
RREQ[C, B, A, K]
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(a)
(d)(c)
(b)
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LA
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FB
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E G
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KJ
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LA
RREQ[C]
RREQ[C]
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C
B
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E G
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LA
RREQ[C]
RREQ[C]
C
B
D
E G
H
KJ
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LA
RREQ[C, E, G]
RREQ[C, B, A]
RREQ[C, B, A]
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C
B
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E G
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LA
RREQ[C, E, G]
RREQ[C, B, A]
RREQ[C, B, A]
F F
C
B
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E G
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KJ
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RREP[C, E, G, H]
RREQ[C, B, A, K]
L
Route Discovery in DSR
Route Discovery in AODV (1)
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C
B
D
E G
H
KJ
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LA
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C
B
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LA
Routing tables
Route Discovery in AODV
(a)
(d)(c)
(b)
F
C
B
D
E G
H
KJ
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LA
RREQ(H)
RREQ(H)
F
C
B
D
E G
H
KJ
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LA
RREP(C)
RREQ
F
C
B
D
E G
H
KJ
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LA
RREQ(H)
RREQ(H)
RREQ(H)
F
C
B
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E G
H
KJ
I
LA
Destination: C, Next hop: C
Dest: C, NxtHop: E
Dest: C, NxtHop: B
Dest: C, NxtHop: EDest: H, NxtHop: H
Dest: C, NxtHop: CDest: H, NxtHop: G
Dest: H, NxtHop: E
Dest: CNxtHop: C
Topic:IEEE 802.11n (MIMO Wi-Fi)
Physical (PHY) Layer Enhancements MAC Layer Enhancements:
Frame Aggregation Block Acknowledgement Reverse Direction (RD) Protocol
Backward Compatibility
IEEE 802.11n - MIMO
ReceiverTransmitter
Reflecting surface
Reflecting surface
802.11n Channel Bonding and20/40 MHz Operation
Frequency 40 MHz operation 20 MHz operation
Sec
on
dar
y20
MH
zch
ann
el
Pri
mar
y20
MH
zch
ann
el
In both 20 MHz and In both 20 MHz and 40 MHz operation, 40 MHz operation,
all control and all control and management management frames are frames are
transmitted in transmitted in primary channelprimary channel
Traffic inTraffic inoverlapping cellsoverlapping cells
in 20 MHz channelin 20 MHz channel(including control frames)(including control frames)T
rans
ition
20
40
MH
z, s
ee:
Pha
sed
Co
exi
sten
ce O
pera
tion
(PC
O) Traffic inTraffic in
this cellthis cellin 20 MHz channelin 20 MHz channel((HTHT--Mixed modeMixed mode
ororNonNon--HT modeHT mode))Traffic inTraffic in
this cellthis cellin 40 MHz channelin 40 MHz channel
((HT greenfield modeHT greenfield mode))
Tra
nsiti
on 4
0
20 M
Hz,
see
:P
hase
d C
oe
xist
ence
Ope
ratio
n (P
CO
)
Traffic inTraffic inoverlapping cellsoverlapping cells
in 20 MHz channelin 20 MHz channel(including control frames)(including control frames)
20 MHz operation
Traffic inTraffic inthis cellthis cell
in 20 MHz channelin 20 MHz channel((HTHT--Mixed modeMixed mode
ororNonNon--HT modeHT mode))
802.11n PHY-layer Frame Format
L-STF L-SIGL-LTF Data
8 s 8 s 4 s
Service16 bits
PSDU Tail6 bits
Pad bits
Rate4 bits
Length12 bits
reserved1 bit
Parity1 bit
Tail6 bits
Legacy physical-layer header
L-STF = Non-HT Short Training fieldL-LTF = Non-HT Long Training fieldL-SIG = Non-HT Signal field
HT-SIG = HT Signal fieldHT-STF = HT Short Training fieldHT-LTF = HT Long Training field
Non-HT physical-layer frame (PPDU)
HT-mixed format physical-layer frame
L-SIGL-LTFL-STF Data
8 s 8 s 4 s
HT-STF HT-LTFHT-SIG HT-LTF HT-LTF HT-LTF
8 s 4 s
Data HT-LTFs4 s per LTF
Extension HT-LTFs4 s per LTF
HT-greenfield format physical-layer frame
HT-LTF1HT-GF-STF
8 s 8 s
HT-SIG
8 s
DataHT-LTF HT-LTF HT-LTF HT-LTF
Data HT-LTFs4 s per LTF
Extension HT-LTFs4 s per LTF
Legacy preamble
IEEE 802.11 Terminology
PHY PHY headerheader
PHY PHY preamblepreamble
MAC MAC headerheader
DataData FCSFCS
Key:
PPDU = PLCP protocol data unitPPDU = PLCP protocol data unitPSDU = PLCP service data unitPSDU = PLCP service data unitMPDU = MAC protocol data unitMPDU = MAC protocol data unitMSDU = MAC service data unitMSDU = MAC service data unit
PLCP = physical (PHY) layerPLCP = physical (PHY) layerconvergence procedureconvergence procedure
MAC = medium access controlMAC = medium access control
Key:
PPDU = PLCP protocol data unitPPDU = PLCP protocol data unitPSDU = PLCP service data unitPSDU = PLCP service data unitMPDU = MAC protocol data unitMPDU = MAC protocol data unitMSDU = MAC service data unitMSDU = MAC service data unit
PLCP = physical (PHY) layerPLCP = physical (PHY) layerconvergence procedureconvergence procedure
MAC = medium access controlMAC = medium access control
PSDU = MPDU
PPDU
MSDU
802.11n MAC-layer Frame Format
bytes: 2 2 6 6 6 2 6 2 4 0 to 7955 4
FC D/I Address-1 Address-2 Address-3 Address-4SC QC Data FCS
MAC header MSDU
HT HT ControlControl
TRQ = Training RequestMAI = MCS request or Antenna Selection IndicationMFSI = MFB Sequence IdentifierMFB/ASELC = MCS Feedback
and Antenna Selection Command/Data
MCS = Modulation and Coding SchemeMFB = Modulation and Coding Scheme Feedback
bits: 16 2 2 2 2 1 5 1 1
Link Adaptation ControlCalibration
PositionCalibrationSequence
ReservedCSI/
Steering
NDPAnnouncement
ReservedAC
Constraint
RDG/More PPDU
Link Adaptation ControlCalibration
PositionCalibrationSequence
ReservedCSI/
Steering
NDPAnnouncement
ReservedAC
Constraint
RDG/More PPDU
bits: 1 1 4 3 7
Reserved
TRQ MAI MFSI MFB/ASELC
HT = High Throughput
Packet Aggregation
802.11n Frame Aggregation
E{b0}=16 slots
TimePHY PHY preamblepreamble
DIFSBackoff
BusyBusyBusyBusyPHY PHY
headerheader
Data payload(0 to 2304 bytes)
FCSFCS
SIF
SMAC MAC headerheader
ACKACKPHY PHY
preamblepreamblePHY PHY
headerheader FCSFCSMAC MAC
headerheader
Overhead
Overhead
PHY PHY preamblepreamble
DIFSBusyBusyBusyBusy
PHY PHY headerheader
Aggregated data payload(up to ~64 Kbytes)
FCSFCSMAC MAC
headerheader
(a)
(b)
Frame Aggregation:A-MSDU and A-MPDU
DIFS
A-MSDU = Aggregated Ethernet frames (= PSDU up to 8 KB)
Ethernet Ethernet headerheader DataData
MSDU subframe = Ethernet frame:
PHY PHY preamblepreamble
PHY PHY headerheader
802.11n 802.11n MAC MAC
headerheaderFCSFCS
Subframe Subframe 11
Subframe Subframe 22
Subframe Subframe NN
BusyBusyBusyBusy
A-MPDU = Aggregated 802.11n frames (= PSDU up to 64 KB)
802.11n 802.11n MAC MAC
headerheaderDataData
PHY PHY preamblepreamble
PHY PHY headerheader
FCSFCS
Subframe 1Subframe 1DIFS
PaddingPadding
MPDU MPDU DelimiterDelimiter PaddingPadding
Subframe 2Subframe 2RIF
SR
IFS
RIF
SR
IFS
Subframe Subframe NN
Block ACKBlock ACK
SIF
SS
IFS
RIF
SR
IFS
BusyBusyBusyBusy
(a) MSDU Aggregation
(b) MPDU AggregationRDG/More PPDU = RDG/More PPDU = 11
RDG/More PPDU = RDG/More PPDU = 00A-MPDU subframe:
MPDU
ACKACK
SIF
SS
IFS
TXOP duration
Block Acknowledgement Session
Transmitter Receiver
ACK
addBA Request
addBA Response
ACK
Block ACKsetup
Data MPDU
Block ACK
BlockAckReq (BAR)
Data andBlock ACKtransmission
Data MPDU
Data MPDUrepeatedmultipletimes
ACK
delBA Request
Block ACKteardown
Block Acknowledgement Frame
bytes: 2 2 6 6 2 variable 4
MAC header
Duration / ID Receiver Address Transmitter Addr. BA Control Block ACK InformationFrame Ctrl FCS
bits: 1 1 1 9 4
Block ACK Policy
Multi TIDCompressed
BitmapReserved TID_INFO
(a)
(b)
Block ACKStarting Sequence Control
Block ACK Bitmap
bytes: 2 8
Block ACKStarting Sequence Control
Block ACK Bitmap
bytes: 2 2 8
Per TID Info Block ACK BitmapBlock ACK
Starting Sequence Control
Basic Block ACK – 128 byte bitmap
Compressed Block ACK- mandatory 8-byte bitmap
- no support for fragmentation
Multi-TID Block ACK (repeated for each TID)
bits: 4 12
Fragment Number (0)
Starting Sequence Number
bytes: 2 128
Block ACK Frame Subfields
Multi-TIDCompressed
BitmapBlock ACK
frame variant
BasicBlock ACK
Multi-TIDBlock ACK
Compressed Block ACK
reserved
0
0
1
1
0
1
0
1
Multi-TIDCompressed
BitmapBlock ACK
frame variant
BasicBlock ACK
Multi-TIDBlock ACK
Compressed Block ACK
reserved
0
0
1
1
0
1
0
1
(a) (b)
Frame fragments
Ac
kn
ow
led
ge
d d
ata
fra
me
s
0 1 2 3 4 5 … 13 14 15
012345
.
.
.
616263
Frame fragments
Ac
kn
ow
led
ge
d d
ata
fra
me
s
0 1 2 3 4 5 … 13 14 15
012345
.
.
.
616263
Block ACK Example
Time
Block ACKBlock ACK(Compressed)(Compressed)
MPDUMPDU#147#147
MPDUMPDU#148#148
MPDUMPDU#178#178
BlockAckReqBlockAckReq#146#146
MPDUMPDU#149#149
MPDUMPDU#150#150
A-MPDU
(lost frame)
Starting Sequence Number = 146BA Bitmap (64 bits) =
11110111 11111111 11111111 11111111 00000000 00000000 00000000 00000000 =7F FF FF FF 00 00 00 00
Time
Block ACKBlock ACK(Compressed)(Compressed)
MPDUMPDU#179#179
MPDUMPDU#180#180
BlockAckReqBlockAckReq#150#150
MPDUMPDU#181#181
A-MPDU
Starting Sequence Number = 150BA Bitmap (64 bits) =
11111111 11111111 11111111 11111111 11111111 11111111 11111111 11110100 =FF FF FF FF FF FF FF 4F
MPDUMPDU#211#211
MPDUMPDU#210#210
(lost frame)
MPDUMPDU#146#146
MPDUMPDU#150#150
(retransmittedframe)
#179 #210
Reverse Direction (RD) Protocol
Unidirectional vs. Bidirectional RTS/CTS Access Scheme
RTSTimeDIFS Backoff
BusyBusy SIF
S
CTS
SIF
S
SIF
S
BACK
Data_fwd
RTSDIFS Backoff
BusyBusy SIF
S
CTS
SIF
S
SIF
SBACKf
Data_fwd
DIFS
SIF
S
BACKr
Data_rvs
DIFS
(a)
(b)
RD initiator
RD responder
Transmitter
Receiver
RDG/More PPDU = RDG/More PPDU = 11
RDG/More PPDU = RDG/More PPDU = 11
RDG/More PPDU = RDG/More PPDU = 00
TXOP duration
TXOP duration
802.11n Backwards Compatibility Modes: CTS-to-Self
(a) Legacy compatibility mode
(b) Mixed compatibility mode
(c) Greenfield mode
SIF
SS
IFS
Blocking out non-HT stations with Network Allocation Vector (NAV)
Legacy Legacy 802.11802.11
MAC headerMAC headerCTSCTS--toto--selfself
ACKACK
FCSFCS802.11n802.11n
MAC headerMAC headerDataData S
IFS
SIF
S
Legacy Legacy 802.11802.11
PHY headerPHY header
CTS-to-self frame (Non-HT format)
802.11n802.11nPHY headerPHY header
Data frame (HT format)
Legacy Legacy 802.11802.11
PHY headerPHY header
ACKACK
Blocking out non-HT stations with spoofed duration value (L-SIG field)
FCSFCS802.11n802.11n
MAC headerMAC header DataData SIF
SS
IFS
FCSFCS802.11n802.11n
MAC headerMAC headerDataData S
IFS
SIF
S
ACKACK
802.11n802.11nPHY headerPHY header
802.11n802.11nPHY headerPHY header
(no protection)
Data frame (HT-mixed format)
Data frame (HT format)
Dual-CTS protection (CTS-to-self)
802.11n(HT-Greenfield)
802.11g(Legacy non-HT)
AAP
B
AP
A
B
RTS (HT)RTS (HT)
CTS (HT)CTS (HT) CTS (L)CTS (L)
Data (HT)Data (HT)
CTS (HT)CTS (HT)
TimeCTS-to-self
sets NAV
sets NAV
CTS-to-self
CTS (L)CTS (L) Data (L)Data (L)
receivesdata (L)
receivesdata (HT)
SIF
S
Example of L-SIG Duration Setting
BACKBACK
Leg
acy
Leg
acy
prea
mbl
epr
eam
ble
RTSRTS DataData
LL -- S
IGS
IG
CTSCTS
Leg
acy
Leg
acy
prea
mbl
epr
eam
ble
LL -- S
IGS
IG
Leg
acy
Leg
acy
prea
mbl
epr
eam
ble
LL -- S
IGS
IG
Leg
acy
Leg
acy
prea
mbl
epr
eam
ble
LL -- S
IGS
IG
CFCF--EndEnd
L-SIG duration
L-SIG duration
L-SIG duration
NAV duration
NAV duration
NAV duration
802.11n Phased Coexistence Operation (PCO)
Sec
ond
ary
20 M
Hz
chan
nel
Prim
ary
20 M
Hz
chan
nel
Traffic in Traffic in BSSBSS--11 in in 802.11g802.11g
20 MHz channel (20 MHz channel (NonNon--HT or HTHT or HT--Mixed modeMixed mode))
Traffic in Traffic in BSSBSS--22in 802.11gin 802.11g
20 MHz channel20 MHz channel
20 MHz phase
AP reservesboth 20-MHz channels for
40 MHz phase
AP reservesboth 20-MHz channels for
40 MHz phase
AP releasesthe 20 MHz channels
AP releasesthe 20 MHz channels
802.11n(HT-Greenfield)
802.11g(HT-Mixed)
802.11nAP
CC
B
802.11g(HT-Mixed)
A
AnotherAP
802.11g802.11g(Legacy)(Legacy)
BSS-1
BSS-2
Time
CT
SC
TS
-- toto
-- se
lfse
lf
CF
CF
-- En
dE
nd
CT
SC
TS
-- toto
-- se
lfse
lf
Be
aco
nB
ea
con
OR
OR
Se
tS
et --
PC
OP
CO
-- Ph
ase
Ph
ase
BusyBusy(traffic in(traffic inBSSBSS--22))
PIF
S
CF
CF
-- End
End
APAP and and AAexchange traffic exchange traffic
in 802.11nin 802.11n40 MHz channel 40 MHz channel ((HT greenfield HT greenfield
modemode))P
IFS
Set
Set
-- PC
OP
CO
-- Pha
seP
hase
CF
CF
-- En
dE
nd
(truncated)
(truncated)
NAV of station B (primary channel)
NAV of station C (secondary channel)
(truncated)NAV of sta. A(40 MHz ch.)
NAV (A)
20 MHzphase
Transition
40 MHz phase
Tran
sitio
n
Topic:RFID: Radio-Frequency
Identification
Query Slot Protocol (ALOHA) for Tag Interrogation
RFID - Query Slot ProtocolVisit http://www.gs1.org/epcglobal/standards for RFID Protocols Class-1 Generation-2
slot 0: QueryRequest(Q=2)
slot 1: QueryRepeat
slot 2: QueryRepeat
Reader R Tag T1 T2 T3 T4 T5 T6 T7 T8 T9 T10
cnt=2invt=0
cnt=1invt=0
cnt=0invt=0
cnt=3invt=0
cnt=0invt=0
cnt=2invt=0
cnt=3invt=0
cnt=0invt=0
cnt=1invt=0
cnt=2invt=0
slot 0: QueryAdjust
NAK
Q Q1 = 3
cnt=5 cnt=7 cnt=0 cnt=2 cnt=6 cnt=1 cnt=2 cnt=4 cnt=3 cnt=2
RN16(T3)
( collision )RN16(T3,T5,T8)
ACK(RN16-T3)
EPC(T3)invt=1
cnt=4 cnt=6 cnt=1 cnt=5 cnt=0 cnt=1 cnt=3 cnt=2 cnt=1
RN16(T6)
ACK(RN16-T6)
EPC(T6)invt=1
( collision )RN16(T3,T5,T8)
cnt=3 cnt=5 cnt=0 cnt=4 cnt=0 cnt=2 cnt=1 cnt=0
Classification of QoS Techniques in 802.11