a link layer scheme for reliable multicast in wireless networks thesis defense of: aarthi natarajan...

A Link Layer Scheme for Reliable Multicast in Wireless Networks

Thesis defense of:

Aarthi NatarajanAdvising Committee:

Dr. Sandeep GuptaDr. Partha Dasgupta Dr. Andrea Richa

April 2003 Mobile Computing and Networking GroupArizona State University

Outline Motivation Challenges Related Work: IEEE 802.11 Multicast, LBP, DBTMA System Model Protocols: RDNP and M-RDNP Simulation Environment Performance Results: Wireless LANs, Ad hoc networks Conclusions and Future Work


ChatApplication

Search and RescueOperation

Group Applications

More Applications … •Military Operations•Emergency operations•Whiteboard Applications

NEED “NEED “RELIABLERELIABLE” COMMUNICATION” COMMUNICATION


Why Wireless ?Wireless Network : devices with wireless adapters communicating with

each other using EM waves Ease and Speed of deployment. Wired network may not be possible.

Wireless Network Architectures

Motivation

Wired network

Wired network

Centralized or LAN

Base Station

Distributed or Ad hoc

1. All devices connect to base station2. Infrastructure based3. End hop wireless

1.Collection of autonomous hosts2. No Infrastructure3. All hop wireless


Problem Statement To build a reliable link-layer protocol for multicast

in single channel multi-access wireless networks Reliability can be achieved at

End-to-end: across several hop. Link level: across a single hop.

Why reliable multicast at the link layer[IG00]? Allows local error recovery. Improves throughput. Conserves energy. Reduces end-to-end delay.

Motivation

End to end reliability

Source Destination

link levelreliability


Link Level Multicasting Repeated unicast transmissions

Redundant data, Wastes energy, Increases delay, Reduces throughput Reliable Broadcast at the multicast address and filter at the receivers

Design Issues: Medium Access:

Wired Networks use CSMA/CD Wireless Networks signal strength fades with distance

self interference, hidden terminals exposed terminals, capture effect

Error Recovery Controlling the flow of feedback information

5 transmissions

Sender

1 transmissions

Sender

4

22

d

hhGGPP rt

rttr


Medium Access Issues Hidden Terminals

Nodes not within the senders range but within the receiver range

Causes collisions at the receivers Collision detection cannot be used

Location dependant carrier sensing: Even if the receiver may experience collisions, the sender may not.

Self Interference: transmit signal flows into receive path

Capture Effect Picks up stronger signal as long as

the ratio of the stronger to weaker signal exceeds the capture threshold.

Node B Node O Node G

Challenges

HIDDEN TERMINAL

Node B Node G

Can still pick up packet from Node B

Node O

Signal from Node B

Signal from Node G> Capture

Threshold (SNRT)


Error Recovery and Feedback Control Local Error Recovery

High channel BER Channel bit error rate can be as high as 1 in 104 or higher. Almost 40% or more of the packets are in error when payload is 512b.

Retransmission based [TKP97] ACK based : absence of ACK NACK based : presence of NACK Explicit retransmission requests : reception of retransmit request packet

FEC based

Controlling the flow of feedback from multiple receivers

Battery Anemic Size and weight limitation restrict the lifetime of the device battery. Energy conservation techniques


System Model and Assumptions Single channel multi-access networks Single transceiver Infrastructure-based as well as ad hoc Packet loss : Bit errors and Collisions Group membership maintained by the higher layer

protocols Two Ray Ground Propagation Model

Signal has to greater than the reception threshold to receive the packet correctly

The medium is perceived as busy as long as the signal is greater than the noise threshold.

4

22

d

hhGGPP rt

rttr

Preliminaries


Some Related Work… Solutions to Hidden Terminals

RTS-CTS based : Single Channel Unicast: IEEE 802.11Unicast Multicast: LBP, PBP, DBP

Busy Tone based : Two channels Unicast: DBTMA [DJ98] Multicast: IEEE 802.11MX [Sha02]

IEEE 802.11 Multicast

Related Work


ACKDATA CTS

RTS

IEEE 802.11 Unicast [Com99]

RTS-CTS ACK based error recovery Physical + virtual carrier sensing DIFS, SIFS inter-frame space for

prioritization of DATA

Sender Hidden Terminal Receiver

RTS

CTS

DATA

ACK

DIFS

SIFS

SIFS

SIFS Sender

Receiver

Update NAV from RTSUpdate NAV from CTS

Related Work

Others

H

H

H

H

X

XXXX

XX

RTS Request to send

CTS Clear to send

ACK Acknowledgement


RTS-CTS for Multicast Several receivers : feedback collision Try to eliminate the collision of feedback LBP[KK01] – leader node sends the

feedback information DBP[KK01] – all nodes send out feedback

after a certain random delay. PBP[KK01] – every node sends out

feedback with certain probability “p”. BSMA[TG00b], BMW[TG00a], BMMM,

LAMM [Shal02] RTS-CTS does not solve all hidden terminal

problems[XGB02]

Related Work

RTS

HCTS Collision


IEEE 802.11 Multicast [Com99]

Not Reliable Hidden terminal problems No local error recovery

DATA

DIFS

Sender

Others

Ignore data

Consume dataGroupNeighbors

Related Work

IEEE 802.11

DCF PCF

CSMA(Unreliable)

CSMA+CA(Reliable)

Polling

Multicast

Broadcast

Unicast

Unicast


Our Protocol Salient Features

Protocol RDNP Deals only with local error recovery No CTS packet. Uses a NACK or collision of NACKs to prompt retransmissions. NACKs do not contain any relevant information. Does not suppress hidden terminals

Protocol M-RDNP Mitigate the effect of hidden terminals Reliable neighbors do not suffer from hidden terminals as long

as sender is transmitting Forces routing layer to build routes only using reliable neighbors


Protocol RDNP

RTS DATA

NACK

DIFS SIFS

SIFS Sender

GroupNeighborsWithout packet

Update NAV from RTS

Others&Group NeighborsWith packet

Good for wireless LANs when there are no hidden terminals base station is the only node that can transmit multicast data.

Not so good for ad hoc networks because of hidden terminals.

Protocol


Reliable and Interference RegionProtocol

RX

CS

Node A Node B1 Node B2 Node C1 Node C2

Yippee! I still receive A’s signalThanks to capture effect.

Booo Hooo! I experience collisions

Hey! I can transmit.I am not within A’s noise range

RL

CSI

RX Reception range

CS Noise Range

RL Reliable Range

CSI Interference Range

Reception range: Radius within which the signal is greater than the reception thresholdNoise Range: Radius within which the signal is greater than the noise threshold

Hey! I cannot transmit.I am within A’s noise range

Reliable Neighbors: All neighbors within the collision free zone.

Unreliable Neighbors: All neighbors not in the reliable range


Minimum Reliable Radius

Assumption: No two nodes “start” transmitting simultaneously.

Two simultaneous transmissions must be separated from each other by a distance of CS

Around a sender the maximum number of nodes which can be transmitting simultaneously is 6

Protocol

Node S

RL

Node A

Node B

Node F

Node C

Node D

Node E

CS

Node R

Minimum RL ≈ 170m when CS = 550m

CS

CS

d Φ

dER dFR

dAR

dBRdCR

dDR

T

FBEBDBCBBRAR

SR

TFEDCBA

S

SNR

dddddd

d

SNRPPPPPP

P

444444

4

111111

1


Protocol M-RDNP Force all routes to be formed using only reliable neighbors. Thus transmissions use only reliable hops in which there are

no hidden terminal problems. Might use more number of hops to transmit to the same node

On Data On RTS

If (routing packet && !reliable()) then drop packetelse send to higher layer

If (reliable()) then prepare to send NACKelse do not prepare to send NACK

Protocol


An example RL ≈ 170m

Number of hops = 4 Number of hops = 6

Routes using IEEE 802.11 and RDNP at the MAC layer

Routes using M-RDNP at the MAC layer

Protocol

1

2

3

1

2

3


Simulation Environment Network Simulator [Net02] Performance Metrics

Average Packet Drop Ratio per Node = Average Energy Consumed per Node per packet =

Wireless LANs: IEEE 802.11, LBP, DBP, PBP, RDNP

Ad hoc networks Routing Layer: SPST [GBS00], SPST [Sri03] better than M-AODV,

ODMRP, MST IEEE 802.11, RDNP, M-RDNP

All simulation points averaged over 45 runs Accuracy 5% confidence interval 99% [Jai91]

Number of packets dropped per nodeNumber of packets sent

Results

Energy consumed per nodeNumber of packets recv


Simulation Results – Wireless LANsStationary nodes

BER (X 10e5)

Mobile nodes

BER (X 10e5)

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

0.3

0.32

0.34

0.36

0.38

0.4

0.42

0.44

1 5 10 50 100

IEEE 802.11

DBP

PBP

LBP

RDNP

0

0.01

0.02

0.03

0.04

0.05

0.06

1 5 10 50 100

IEEE 802.11

DBP

PBP

LBP

RDNP

0

0.010.02

0.030.04

0.050.06

0.070.08

0.09

1 5 10 50 100

IEEE 802.11

DBP

PBP

LBP

RDNP

Results

1

1

2 2

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

5 10 20 30 40

IEEE 802.11

DBP

PBP

LBP

RDNP

With Unicast traffic

NUMBER OF NODES

AV

G D

RO

P R

ATIO

1

2

BER (X 10e5)

Stationary nodes with explicit retransmission requests

EN

D-T

O-E

ND

DELA

Y

4

4

3


Simulation - Stationary Ad Hoc networks

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.05

0.1

0.15

0.2

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.02

0.04

0.06

0.08

0.1

0.12

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

BER (X 10e5) BER (X 10e5)


Nodes = 10, Avg. neighbor density ≈ 4,3 Nodes = 20, Avg. neighbor density ≈ 6,4


AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

Results

11

11

2 2

2 2

33

33


Simulation – MANETs

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.050.1

0.150.2

0.250.3

0.350.4

0.45

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.050.1

0.150.2

0.250.3

0.350.4

0.45

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.050.1

0.150.2

0.250.3

0.350.4

0.45

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

Speed (m/s)

Speed (m/s)

Speed (m/s)

Speed (m/s)

Nodes = 10, Low BER Nodes = 30, Low BER

Nodes = 10, High BER Nodes = 30, High BER

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

Results

11

22

3

3


Simulation – MANETS (Very High Speed ≈ 100miles/hr)

0.3

0.32

0.34

0.36

0.38

0.4

0.42

0.44

0.46

0 10

IEEE 802.11

RDNP

M-RDNP

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0 10

IEEE 802.11

RDNP

M-RDNP

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0 10

IEEE 802.11

RDNP

M-RDNP

Nodes = 10, Speed = 80 miles/hr Nodes = 30, Speed = 80 miles/hr

BER BER

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

Results

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

133 133

IEEE 802.11

RDNP

M-RDNP

BER BER

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

Nodes = 10, Speed = 150 miles/hr Nodes = 30, Speed = 150 miles/hr


Summarizing Reliability Stationary Ad hoc networks

M-RDNP - “Good” for low neighbor density. M-RDNP and RDNP – Statistically indifferent for high

neighbor density, “better” than IEEE 802.11. Mobile Ad hoc Networks Low/Moderate Speeds

M-RDNP – “Good” for low neighbor density. IEEE 802.11 - “Good” for low BER and high neighbor

density. RDNP – “Good” for high BER and high neighbor density.

Mobile Ad hoc Networks Very High Speeds All three statistically indifferent.


Energy Results The energy consumed for a retransmission is much higher than the energy

consumed for a transmission. For stationary ad hoc networks,

As the BER increases the energy consumed per packet is much higher for RDNP and M-RDNP owing to the increase in the number of retransmissions.

RDNP consumes more energy than M-RDNP because of high drop ratio hidden terminals.

For mobile ad hoc networks As the mobility increases, the energy consumed also increases. For low BER the energy consumed by RDNP and IEEE 802.11 is almost the

same, because no energy is lost in retransmissions. M-RDNP consumes the least energy for low BER because is does not lose

packets due to hidden terminals. For higher BER RDNP and M-RDNP consumes more energy because of

retransmissions


Conclusions RDNP and M-RDNP was proposed as a NACK based reliable

multicast extension to IEEE 802.11 Reliable multicast is extremely desirable when channel BER

is high. Frequent changes in route caused by SPST, “not good” for

the MAC layer. Energy cost associated with retransmission very high. For very high speed networks MAC layer is insignificant.

Future Work Addition of energy saving strategies Adapt the MAC layer based on the network characteristics Estimate the link metric for SPST based on the conclusions


Thank You!

Questions ?


References[Com 99] ANSI/IEEE Standard 802.11 Wireless LAN medium control (MAC) and physical layer (PHY) specifications, In 1999

Edition.[DJ98] J. Deng, Z. J. Haas, “Dual Busy Tone Multiple Access (DBTMA): A New Medium Access Control for Packet Radio

Networks”, In IEEE ICUPC’98, Italy, 1998.[KK01] J. Kuri, S. Kasera, “Reliable Multicast in Multi-access Wireless LANs”, Wireless Networks, 7(4):359-369, July 2001.[Net02] Network Simulator – ns-2, Available via http://www.isi.edu/nsnam/ns/, [Accessed on Aug 02][Sha02] Vikram Shankar, “A Medium Access Control Protocol with reliable multicast support for wireless networks”, Master’s

Thesis, Arizona State University, Tempe, AZ 85287, December 2002[SG03] Ganesh Sridharan and Sandeep K.S.Gupta, “Performance comparison study of self stabilizing routing protocols for mobile

ad hoc networks”, In preparation[GBS00] Sandeep K.S. Gupta, A. Bouadallah and P.K. Srimani, “Self Stabilizing Protocols for Shortest Path Tree for multi-cast

routing in mobile networks”, In proceedings of LCNS:1900, Euro-Par’00 Parallel Proceedings, pages 600-604, 2000.[TKP97] Fouad A. Tobagi and Leonard Kleinrock, “Comparison of Sender-Initiated and Receiver-Initiated Multicast Protocols”, In

IEEE Journal on Selected Areas in Communication, April 1997.[SHAL02] Min-Te Sun, Lifei Huang, Anish Arora and Ten-Hwang Lai, “Reliable MAC Layer Multicast in IEEE 802.11 wireless

networks”, In Proceedings of International Conference on Parallel Processing, ICPP ’02, pages 527-536, August 2002.[XGB02] K.Xu, M.Gerla and S.Bae, “How effective is the IEEE 802.11 RTS/CTS handshake in ad hoc networks”, In Proceedings

of IEEE Globecom 2002.[TG00a] Kent Tang and Mario Gerla. “MAC Layer Broadcast Support in 802.11 Wireless Networks”, In Proceedings of 21st

Century Military Communication Conference, MILCOM’00, pages 544-548, 2000[TG00b] Kent Tang and Mario Gerla. “Random Access MAC for Efficient Broadcast Support in Ad Hoc Networks”, In IEEE

Wireless Communications and Networking Conference, WCNC 2000, pages 454-459, 2000[TG01] Kent Tang and Mario Gerla. “MAC Reliable Broadcast Ad hoc Networks”, In Communications for Network Centric

Operations: Creating the Information force. IEEE Military Communication Conference, MILCOM’01, pages 1008-1013, 2001


Medium Access Issues Capture Effect

Picks up stronger signal as long as the ratio of the stronger to weaker signal exceeds the capture threshold.

Node B

Node P

Node G

Node O

Oops! I would like to transmit but cannot !!!

EXPOSED TERMINAL

Exposed Terminals Nodes within the senders range

but not within the receivers range Reduces throughput

Node B Node G

Can still pick up packet from Node B

Node O

Signal from Node B

Signal from Node G> Capture

Threshold


Why RTS-CTS does not work ???

Node A Node B

RX

Node C1

ABd78.1

dAB

Node C2


DATA

CTS

RTS

Leader Based ProtocolSender

Non groupneighbor

Groupneighbor

GroupLeader

RTS

CTS

DATA

ACK

NCTS NACK

DIFS

SIFS

SIFS

SIFS Sender

Leader

Groupneighbors

Update NAV from RTSUpdate NAV from CTS

ACK

Problems: Leader Mobility reduces throughput “Capture Effect” may hide NCTS and NAK from distant nodes Incoming nodes may not have heard RTS/CTS exchange and may cause collision Sender has to know the multicast group members a priori

Related Work


Busy Tone Solution to Hidden Terminals

RTS

Node B Node O Node G Node P

tone Cannot transmit because I sense a receiver busy tone

Problems:Extra hardware, more energy

Related Work


Area around a Transmitter

Node A

RX

CSI

RL

CS

Reliable Neighbors: All neighbors within the collision free zone.

Unreliable Neighbors: All neighbors not in the reliable range

Protocol

Collision Free Zone: The area around a transmitter in which receiver do not suffer from hidden terminals when the transmitter is transmitting data.

Collision Zone: The area around the transmitter within which receivers are within the range of the sender but might suffer from hidden terminals.

Interference Free Zone: The area around a transmitter within which no node transmits because of physical carrier sensing.

Interference Zone: The area around a transmitter within which nodes can cause hidden terminal problems for receivers in the collision zone.


Calculate RL and CSI

RX1.78CSI

RX1.78d

RXd10.0SNR

BC

ABT

and

78.2

1

and

CSRL

SNR

CSd

dCSd10.0SNR

4T

AB

ABBCT

For CSI -

For RL -

Node A Node B Node C

dAB dBC


An example RL ≈ 170m

Number of hops = 4 Number of hops = 6

Routes using IEEE 802.11 and RDNP at the MAC layer

Routes using M-RDNP at the MAC layer

Protocol


SPST Self Stabilizing Routing Protocol Every node periodically sends out beacon messages Using values in the beacon messages SPST builds routes to

the root of the multicast group.

Algorithm SPST

If received beacon from node j thenupdate neighbor list with Node jif Node j is the root then

distir = 0

Parenti = null

elsedistir = minimum(distir, weightij + distjr)

Parenti = j

endifendif

Related Work


Confidence Interval

Each sample mean is an estimate of the population mean With k samples we have k estimates Problem: get one from k. Best is get probabilistic bounds Two bounds c1 and c2 such that there is a high probability, 1-α, that the population

means is in interval (c1,c2)Probability(c1≤μ≤c2) = 1-α(c1,c2) confidence interval α significance level(≈0)100(1- α) confidence level (≈100)1- α confidence coefficient(≈1)

n

szx

n

szx 2121

,

Population = {…,xi,…} Sample = {x1, x2 , x3 … xn}

Population Mean μ

Population Standard deviation σ

Sample mean xmean

Sample standard deviation s or standard error

Parameters (population) fixed Statistics (sample) random variable

Confidence Level

Z(1-α/2)

90 1.645

95 1.960

99 2.576

mean x

accuracy r

deviation standard s

desired interval confidence z

runs ofnumber

1002

n

xr

zsn


Energy - Stationary Ad Hoc networks

0

0.002

0.004

0.006

0.008

0.01

0.012

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.0020.004

0.0060.008

0.010.012

0.0140.016

0.018

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP

0

0.001

0.002

0.003

0.004

0.005

0.006

0 5 10 30 50 70 100

IEEE 802.11

RDNP

M-RDNP





AV

G E

nerg

y

con

su

med

per

packet

Results

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet


Energy – MANETs (Walking Speeds)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.00050.001

0.00150.002

0.00250.003

0.00350.004

0.0045

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

0

0.0020.004

0.0060.008

0.010.012

0.0140.016

0.018

4 8 12 16 20

IEEE 802.11

RDNP

M-RDNP

Speed (m/s)

Speed (m/s)

Speed (m/s)

Speed (m/s)



Results

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet


Energy – MANETS (Vehicular Speeds)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

44 133 222 300

IEEE 802.11

RDNP

M-RDNP



Speed (m/s) Speed (m/s)


Results

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet

AV

G E

nerg

y

con

su

med

per

packet


Reliability – MANETS (Very High Speed ≈ 100miles/hr)

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0.3

0.350.4

0.450.5

0.550.6

0.650.7

0.75

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

44 133 222 300

IEEE 802.11

RDNP

M-RDNP

0.3

0.350.4

0.450.5

0.550.6

0.650.7

0.75

44 133 222 300

IEEE 802.11

RDNP

M-RDNP





AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

AV

G D

RO

P R

ATIO

Results

a link layer scheme for reliable multicast in wireless networks thesis defense of: aarthi natarajan...

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