Computer Networks: Wireless Networks

44
Computer Networks: Wireless Networks Ivan Marsic Rutgers University Chapter 6 – Wireless Networks

description

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). - PowerPoint PPT Presentation

Transcript of Computer Networks: Wireless Networks

Page 1: Computer Networks: Wireless Networks

Computer Networks:Wireless Networks

Ivan Marsic

Rutgers University

Chapter 6 – Wireless Networks

Page 2: Computer Networks: Wireless Networks

Wireless Networks

Chapter 6

Page 3: Computer Networks: Wireless Networks

Topic:Mobile Ad-hoc Networks

(MANETs)

Ad-hoc Network Definition Routing Protocols

Dynamic Source Routing (DSR) Ad Hoc On-Demand Distance-

Vector (AODV)

Page 4: Computer Networks: Wireless Networks

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

Page 5: Computer Networks: Wireless Networks

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)

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A

B

D

E

F

C

packet packet

C E

F

B

A D

Network Layer Notation vs.Link Layer Transmissions (1)

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Network Layer Notation vs.Link Layer Transmissions (2)

C

B

E

FA D

C

B

E

FA D

C

B

D

E

FA

C

B

D

E

FA

packet packet

A

C

B

D

E

F

packet packet

A

C

B

D

E

F

Network layer (t)

Link layer (t1)

Link layer (t2)

Link layer

Network layer

Link layer

Network layer

Page 8: Computer Networks: Wireless Networks

Multihop Throughput

Challenge: more hops, less throughputLinks in route share radio spectrumExtra hops reduce throughput

Throughput = 1

Throughput = 1/2

Throughput = 1/3

Page 9: Computer Networks: Wireless Networks

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

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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

Page 11: Computer Networks: Wireless Networks

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

Page 12: Computer Networks: Wireless Networks

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

Page 13: Computer Networks: Wireless Networks

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

Page 14: Computer Networks: Wireless Networks

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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.

Page 15: Computer Networks: Wireless Networks

Route Discovery in DSR (1)

FB

D

E G

H

KJ

I

Y

Z

LA

C

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Route Discovery in DSR (2)

Broadcast RREQ[C]

Represents a node that has received RREQ for H from C

F

C

B

D

E G

H

KJ

I

Y

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LA

RREQ[C]

RREQ[C]

Page 17: Computer Networks: Wireless Networks

Route Discovery in DSR (3)

F

C

B

D

E G

H

KJ

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LA

RREQ[C, E]

RREQ[C, B]

Page 18: Computer Networks: Wireless Networks

Route Discovery in DSR (4)

C

B

D

E G

H

KJ

I

Y

Z

LA

RREQ[C, E, G]

RREQ[C, B, A]

RREQ[C, B, A]

F

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Route Discovery in DSR (5)

Unicast RREP[C, E, G, H]

F

C

B

D

E G

H

KJ

I

Y

Z

A

RREP[C, E, G, H]

RREQ[C, B, A, K]

L

Page 20: Computer Networks: Wireless Networks

(a)

(d)(c)

(b)

FB

D

E G

H

KJ

I

LA

C

FB

D

E G

H

KJ

I

LA

C

F

C

B

D

E G

H

KJ

I

LA

RREQ[C]

RREQ[C]

F

C

B

D

E G

H

KJ

I

LA

RREQ[C]

RREQ[C]

C

B

D

E G

H

KJ

I

LA

RREQ[C, E, G]

RREQ[C, B, A]

RREQ[C, B, A]

F

C

B

D

E G

H

KJ

I

LA

RREQ[C, E, G]

RREQ[C, B, A]

RREQ[C, B, A]

F F

C

B

D

E G

H

KJ

I

A

RREP[C, E, G, H]

RREQ[C, B, A, K]

L

Route Discovery in DSR

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Route Discovery in AODV (1)

F

C

B

D

E G

H

KJ

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LA

F

C

B

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E G

H

KJ

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LA

Routing tables

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Route Discovery in AODV

(a)

(d)(c)

(b)

F

C

B

D

E G

H

KJ

I

LA

RREQ(H)

RREQ(H)

F

C

B

D

E G

H

KJ

I

LA

RREP(C)

RREQ

F

C

B

D

E G

H

KJ

I

LA

RREQ(H)

RREQ(H)

RREQ(H)

F

C

B

D

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

Page 23: Computer Networks: Wireless Networks

Topic:IEEE 802.11n (MIMO Wi-Fi)

Physical (PHY) Layer Enhancements MAC Layer Enhancements:

Frame Aggregation Block Acknowledgement Reverse Direction (RD) Protocol

Backward Compatibility

Page 24: Computer Networks: Wireless Networks

IEEE 802.11n - MIMO

ReceiverTransmitter

Reflecting surface

Reflecting surface

Page 25: Computer Networks: Wireless Networks

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))

Page 26: Computer Networks: Wireless Networks

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

Page 27: Computer Networks: Wireless Networks

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

Page 28: Computer Networks: Wireless Networks

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

Page 29: Computer Networks: Wireless Networks

Packet Aggregation

Page 30: Computer Networks: Wireless Networks

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)

Page 31: Computer Networks: Wireless Networks

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

Page 32: Computer Networks: Wireless Networks

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

Page 33: Computer Networks: Wireless Networks

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

Page 34: Computer Networks: Wireless Networks

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

Page 35: Computer Networks: Wireless Networks

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

Page 36: Computer Networks: Wireless Networks

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

Page 37: Computer Networks: Wireless Networks

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)

Page 38: Computer Networks: Wireless Networks

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

Page 39: Computer Networks: Wireless Networks

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

Page 40: Computer Networks: Wireless Networks

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

Page 41: Computer Networks: Wireless Networks

Topic:RFID: Radio-Frequency

Identification

Query Slot Protocol (ALOHA) for Tag Interrogation

Page 42: Computer Networks: Wireless Networks

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

Page 43: Computer Networks: Wireless Networks
Page 44: Computer Networks: Wireless Networks

Classification of QoS Techniques in 802.11