A Link Layer Scheme for Reliable Multicast in Wireless Networks

1
A Link Layer Scheme for Reliable Multicast in
Wireless Networks

• Thesis defense of
• Aarthi Natarajan
• Advising Committee
• Dr. Sandeep Gupta
• Dr. Partha Dasgupta Dr. Andrea Richa

2
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

3
Group Applications
Search and Rescue Operation
Chat Application

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

NEED RELIABLE COMMUNICATION
4
Why Wireless ?
Motivation

• 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

Centralized or LAN
Distributed or Ad hoc
Wired network
Base Station
1.Collection of autonomous hosts 2. No
Infrastructure 3. All hop wireless
1. All devices connect to base station 2.
Infrastructure based 3. End hop wireless
5
Problem Statement
Motivation

• 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 layerIG00?
• Allows local error recovery.
• Improves throughput.
• Conserves energy.
• Reduces end-to-end delay.

link level reliability
Destination
Source
End to end reliability
6
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

Sender
5 transmissions
Sender
1 transmissions
7
Medium Access Issues
Challenges

• 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
HIDDEN TERMINAL
Can still pick up packet from Node B
Node O
Node B
Node G
8
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

9
System Model and Assumptions
Preliminaries

• 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.

10
Some Related Work
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

11
IEEE 802.11 Unicast Com99
Related Work
Sender
Hidden Terminal
Receiver
H
H
RTS
DATA
Sender
CTS
ACK
H
Receiver
H
Update NAV from CTS
Update NAV from RTS
Others

• RTS-CTS
• ACK based error recovery
• Physical virtual carrier sensing
• DIFS, SIFS inter-frame space for prioritization
  of DATA

12
RTS-CTS for Multicast
Related Work

• Several receivers feedback collision
• Try to eliminate the collision of feedback
• LBPKK01 leader node sends the feedback
  information
• DBPKK01 all nodes send out feedback after a
  certain random delay.
• PBPKK01 every node sends out feedback with
  certain probability p.
• BSMATG00b, BMWTG00a, BMMM, LAMM Shal02
• RTS-CTS does not solve all hidden terminal
  problemsXGB02

RTS
H
CTS Collision
13
IEEE 802.11 Multicast Com99
Related Work
DATA
Sender
Consume data
Group Neighbors
Ignore data
Others

• Not Reliable
• Hidden terminal problems
• No local error recovery

14
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

15
Protocol RDNP
Protocol
RTS
DATA
Sender
NACK
Group Neighbors Without packet
Update NAV from RTS
Others Group Neighbors With 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.

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Reliable and Interference Region
Protocol
Reception range Radius within which the signal
is greater than the reception threshold Noise
Range Radius within which the signal is greater
than the noise threshold
Hey! I cannot transmit. I am within As noise
range
Hey! I can transmit. I am not within As noise
range
Reliable Neighbors All neighbors within the
collision free zone. Unreliable Neighbors All
neighbors not in the reliable range
Node A
Node B1
Node B2
Node C1
Node C2
Booo Hooo! I experience collisions
Yippee! I still receive As signal Thanks to
capture effect.
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Minimum Reliable Radius
Protocol
Minimum RL 170m when CS 550m
Node F
Node E

• 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

CS
dER
dFR
CS
Node R
dAR
dDR
d
Node D
F
RL
Node A
CS
Node S
dBR
dCR
Node B
Node C
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Protocol M-RDNP
Protocol

• 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

19
An example
Protocol
RL 170m
Routes using IEEE 802.11 and RDNP at the MAC layer
Routes using M-RDNP at the MAC layer
1
1
2
2
3
3
Number of hops 4
Number of hops 6
20
Simulation Environment
Results

• 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 node Number of
packets sent
Energy consumed per node Number of packets recv
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Simulation Results Wireless LANs
Results
Stationary nodes
Mobile nodes
AVG DROP RATIO
AVG DROP RATIO
BER (X 10e5)
BER (X 10e5)
Stationary nodes with explicit retransmission
requests
END-TO-END DELAY
BER (X 10e5)
22
Simulation - Stationary Ad Hoc networks
Results
Nodes 10, Avg. neighbor density 4,3
Nodes 20, Avg. neighbor density 6,4
AVG DROP RATIO
AVG DROP RATIO
BER (X 10e5)
BER (X 10e5)
Nodes 30, Avg. neighbor density 8,5
Nodes 40, Avg. neighbor density 10,6
AVG DROP RATIO
AVG DROP RATIO
3
3
BER (X 10e5)
BER (X 10e5)
23
Simulation MANETs
Results
Nodes 30, Low BER
Nodes 10, Low BER
AVG DROP RATIO
AVG DROP RATIO
Speed (m/s)
Speed (m/s)
Nodes 10, High BER
Nodes 30, High BER
AVG DROP RATIO
AVG DROP RATIO
Speed (m/s)
Speed (m/s)
24
Simulation MANETS (Very High Speed
100miles/hr)
Results
Nodes 10, Speed 80 miles/hr
Nodes 30, Speed 80 miles/hr
AVG DROP RATIO
AVG DROP RATIO
BER
BER
Nodes 10, Speed 150 miles/hr
Nodes 30, Speed 150 miles/hr
AVG DROP RATIO
AVG DROP RATIO
BER
BER
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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.

26
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

27
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

28
Thank You!

• Questions ?

29
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
  ICUPC98, 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, Masters 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 LCNS1900,
  Euro-Par00 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, MILCOM00, 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, MILCOM01, pages 1008-1013, 2001

30
Medium Access Issues

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

• Exposed Terminals
• Nodes within the senders range but not within the
  receivers range
• Reduces throughput

Can still pick up packet from Node B
Node O
Node O
Node P
Node B
Node B
Node G
Node G
EXPOSED TERMINAL
31
Why RTS-CTS does not work ???
RX
dAB
Node A
Node B
Node C1
Node C2
32
Leader Based Protocol
Related Work
RTS
DATA
Sender
CTS
ACK
Leader
NCTS
NACK
Group neighbors
Update NAV from CTS
Update NAV from RTS

• 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

33
Busy Tone Solution to Hidden Terminals
Related Work
Cannot transmit because I sense a receiver busy
tone
tone
RTS
Node O
Node B
Node G
Node P
Problems Extra hardware, more energy
34
Area around a Transmitter
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.

Reliable Neighbors All neighbors within the
collision free zone. Unreliable Neighbors All
neighbors not in the reliable range
35
Calculate RL and CSI
For CSI -
dAB
dBC
Node A
Node B
Node C
For RL -
36
An example
Protocol
RL 170m
Routes using IEEE 802.11 and RDNP at the MAC layer
Routes using M-RDNP at the MAC layer
Number of hops 4
Number of hops 6
37
SPST Self Stabilizing Routing Protocol
Related Work

• Every node periodically sends out beacon messages
• Using values in the beacon messages SPST builds
  routes to the root of the multicast group.

38
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-a, that the population means is in
  interval (c1,c2)
• Probability(c1µc2) 1-a
• (c1,c2) confidence interval
• a significance level(0)
• 100(1- a) confidence level (100)
• 1- a confidence coefficient(1)

39
Energy - Stationary Ad Hoc networks
Results
Nodes 10, Avg. neighbor density 4,3
Nodes 20, Avg. neighbor density 6,4
AVG Energy consumed per packet
AVG Energy consumed per packet
BER (X 10e5)
BER (X 10e5)
Nodes 30, Avg. neighbor density 8,5
Nodes 40, Avg. neighbor density 10,6
AVG Energy consumed per packet
AVG Energy consumed per packet
BER (X 10e5)
BER (X 10e5)
40
Energy MANETs (Walking Speeds)
Results
Nodes 10, Low BER
Nodes 30, Low BER
AVG Energy consumed per packet
AVG Energy consumed per packet
Speed (m/s)
Speed (m/s)
Nodes 10, High BER
Nodes 30, High BER
AVG Energy consumed per packet
AVG Energy consumed per packet
Speed (m/s)
Speed (m/s)
41
Energy MANETS (Vehicular Speeds)
Results
Nodes 10, Low BER
Nodes 30, Low BER
AVG Energy consumed per packet
AVG Energy consumed per packet
Speed (m/s)
Speed (m/s)
Nodes 10, High BER
Nodes 30, High BER
AVG Energy consumed per packet
AVG Energy consumed per packet
Speed (m/s)
Speed (m/s)
42
Reliability MANETS (Very High Speed
100miles/hr)
Results
Nodes 10, Low BER
Nodes 30, Low BER
AVG DROP RATIO
AVG DROP RATIO
Speed (m/s)
Speed (m/s)
Nodes 10, High BER
Nodes 30, High BER
AVG DROP RATIO
AVG DROP RATIO
Speed (m/s)
Speed (m/s)