adhoc networking and challenges
DESCRIPTION
adhoc networking that is a temporary networkTRANSCRIPT
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
C. Rama Krishna
Assistant Professor
Dept. of CSENITTTR, Chandigarh
Email: rkc_97 at yahoo.com
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Outline
• History and Introduction
• Brief overview to Physical Layer
• Issues in Medium Access Control (MAC)
• Issues in Routing and Transport Layers
• Quality-of-Service Issues
• Security Issues
• Additional Resources
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Cellular Technologies 2G Systems 2.5G Systems 3G Systems 4G Systems Next G Systems
Other Short-range Technologies Home RF Bluetooth ZigBee
Wireless LAN Technology
• 2.4 GHz Wireless LAN
• 5 GHz Wireless LAN
• Ad-hoc Mode
• Infrastructure Mode
Long Range Technologies
Internet
Which Technology ?
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
History and Introduction
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
History
• Packet Radio NETwork (PRNET) by DARPA - late 1960s• Military Communications• Disaster Management
• Survivable Packet Radio Networks (SURAN) – 1980s
• MANET group formed under Internet Engineering Task Force (IETF) – 1990s
• IEEE released 802.11 PHY and MAC standard – 1995 (later updated versions evolved)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
What is an Ad hoc Network ?
• Network of wireless nodes (may be static/mobile)– No infrastructure (e.g. base stations, fixed links, routers,
centralized servers, etc.)– Data can be relayed by intermediate nodes– Routing infrastructure created dynamically
AB C
D
radio range of node A
traffic from A D is relayed by nodes B and C
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Does not depend on pre-existing infrastructure
• Ease to deploy
• Speed of deployment
• Anytime-Anywhere-Any device-Anyone (A4) network paradigm
Why an Ad hoc Network?
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Ad hoc Network Example
• Communication between nodes may be in single/multi-hop
• Each of the nodes acts as a host as well as a router
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Typical Applications
• Military environments• soldiers, tanks, planes
• Emergency operations• search-and-rescue
• Personal area networking• cell phone, laptop, etc.
• Civilian environments• meeting rooms, sports stadiums, hospitals, etc.
• Education• virtual classrooms, conferences, etc.
• Sensor networks• homes, environmental applications, etc.
• And many more …
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Some Challenges
• Limited wireless transmission range
• Broadcast nature of the wireless medium• hidden terminal and exposed terminal
problems – MAC problem
• Packet losses due to: transmission errors and mobility
• Mobility-induced route changes – routing problem
• Battery constraints
• Ease of snooping - security problem
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Physical Layer
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
IEEE 802.11 WLAN standards
Sl.No
Standard Specification
1 802.11 Physical Layer & MAC Layer2 802.11a Physical Layer
3 802.11b Physical Layer4 802.11c Support of 802.11 frames5 802.11d New support for 802.11
frames6 802.11e QoS enhancement in MAC7 802.11f Inter Access Point Protocol
8 802.11g Physical Layer9 802.11h Channel selection and
power control10 802.11i Security enhancement in MAC
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Supports networking in two modes:
• Infrastructure based WLAN using access points (APs)
• Infrastructure-less ad hoc networks – widely used in simulation studies and testbeds of MANET
IEEE 802.11 standard
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Access Point (AP)
Basic Service Set (BSS)
Wire line
PC
Laptop
IEEE 802.11 based infrastructure WLAN
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Independent Basic Service Set (IBSS)
Laptop
IEEE 802.11 based infrastructure-less Adhoc Network
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
IEEE 802.11 PHY Layer Specification
StandardParameter
802.11 802.11a 802.11b
Bandwidth 83.5MHz 300MHz 83.5MHz
Frequency band
2.4-2.4835 GHz
5.15-5.35 GHz and 5.725 – 5.825 GHz
2.4-2.4835 GHz
Channels 3 12 3
Data Rate( in Mbps)
1, 2 6, 9, 12, 18, 24, 36, 48 and 54
1, 2, 5.5, and 11
Transmission Scheme
FHSS, DSSSwith QPSK
OFDM (with PSK and QAM )
DSSS(with QPSK & CCK modulation)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Present PHY Layer• IEEE 802.11, 11a, 802.11b and 802.11g
• Supports 1/ 2 /11/ 22/ 54 Mbps data rate in static indoor environment
• DSSS is not suitable for data rate more than 10Mbps
• OFDM based PHY layer design for high data rate transmission up to 54 Mbps [ 802.11a & g]
Physical Layer for high speed MANET
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Medium Access Control (MAC) & Issues
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Need for a MAC Protocol
• Wireless channel is a shared medium and bandwidth is a scarce resource
• Need access control mechanism to avoid collision(s)
• To maximize probability of successful transmissions by resolving contention among users
• To avoid problems due to hidden and exposed nodes
• To maintain fairness amongst all users
• MAC protocol design has been an active area of research in recent years
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Classification of Wireless MAC Protocols
Wireless MAC protocols
Distributed Centralized
RandomAccess
HybridAccess
GuaranteedAccess
RandomAccess
• Guaranteed Access and Hybrid Access protocols require infrastructure such as Base Station or Access Point – Not suitable for MANETs • Random Access protocols can be operated in either architecture – suitable for MANETS
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Distributed Random Access Protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Pure ALOHA MAC Protocol
• In pure ALOHA, frames are transmitted at completely arbitrary times.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
The throughput for pure ALOHA is S = G × e −2G
The maximum throughputSmax = 0.184 , when G = 0.5
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Slotted ALOHA MAC Protocol
• In slotted ALOHA, frames are transmitted only at slot boundaries.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
The throughput for slotted ALOHA is S = G × e−G
The maximum throughput Smax = 0.368, when G = 1
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Throughput versus offered load for pure and slotted ALOHA
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Carrier Sense Multiple Access (CSMA) Protocol
• Max. throughput achievable by pure ALOHA is 0.184 and slotted ALOHA is 0.368
• CSMA gives improved throughput compared to ALOHA protocols
• Listens to the channel before transmitting a packet (reduces collisions)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Variants of CSMA
CSMA
Nonpersistent CSMA
Persistent CSMA
Unslotted Nonpersistent CSMA
Unslotted persistent CSMA
Slotted Nonpersistent CSMA
Slotted persistent CSMA
1-persistent CSMA
p-persistent CSMA
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Behavior of three persistence methods
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CD
• Adds collision detection capability to CSMA; greatly reduces time wasted due to collisions
• Standardized as IEEE 802.3, most widespread LAN
• Developed by Robert Metcalfe during early 1970s..... led to founding of “3COM” company. [later Metcalfe sold his company for $400M)• The name 3COM comes from the company's focus on "COMputers,
COMmunication and COMmpatibility"
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Why can’t we use CSMA or CSMA/CD in a Wireless LAN or Adhoc Network?
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• If the channel is idle, transmit
• If the channel is busy, wait for a random time
• Waiting time is calculated using Binary Exponential Backoff (BEB) algorithm
• Limitations of carrier Sensing
- hidden terminals
- exposed terminals
Carrier Sense Multiple Access (CSMA)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Hidden Terminal Problem
!
• Node A can hear both B and C; but B and C cannot hear each other
• When B transmits to A, C cannot detect this transmission using the carrier
sense mechanism• If C also transmits to A, collision will occur at node A• Increases data packet collisions and hence reduces throughput• Possible solution: RTS (request-to-Send)/ CTS (Clear-to-Send)
handshake
CB A Note: colored circles represent the Tx rangeof each node
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Exposed Terminal Problem
DB CA ?
• When A transmits to B, C detects this transmission using carrier sense
mechanism
• C refrains from transmitting to D, hence C is exposed to A’s transmission
• Reduces bandwidth utilization and hence reduces throughput
• Possible solution: Directional Antennas, separate channels for control
and data
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Uses Request-To-Send (RTS) and Clear-To-Send (CTS) handshake to mitigate the effects of hidden terminals
• Data transfer duration is included in RTS and CTS, which helps other nodes to be silent for this duration
• If a RTS/CTS packet collides, nodes wait for a random time which is calculated using BEB algorithm
Multiple Access Collision Avoidance (MACA)
Drawback:
• Cannot avoid RTS/CTS control packet collisions
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
A BC
D
EDATA
A BC EDRTS
CTS
RTS-CTS Handshake in Action
• A is the source which is in the range of B, D and C• B is the destination which is in the range of A, D and E
radio range of Aradio range of B
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
A BC
D
EDATA
RTS
CTS
• A is the source which is in the range of B, D and C• B is the destination which is in the range of A, D and E• B sends ACK after receiving one data packet • Improves link reliability using ACK
MACA for Wireless LANs (MACAW)
ACK
A BC ED
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Has provision for two modes- Point Coordination Function (PCF)- Distributed Coordination Function
(DCF)
• Point Coordination Function- Provides contention-free access- Requires Access Point (AP) for
coordination- Not suitable for a MANET
IEEE 802.11 MAC Protocol
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Two schemes:
• Basic access scheme (CSMA/CA)
• CSMA/CA with RTS (Request-to-Send)/CTS (Clear-to-Send) handshake (optional)
Distributed Coordination Function (DCF)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Node X
Node A
Node B
Node C
DIFS (DCF Inter-Frame Space)
Time
Data packet
Data packet
Data packet
Basic Access Scheme (CSMA/CA)
-- Data packet
-- Backoff slot
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS
C FA B EDRTS
RTS = Request-to-Send
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDRTS
RTS = Request-to-Send
NAV = 20
NAV (Net Allocation Vector) = indicates remaining duration to keep silent
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDCTS
CTS = Clear-to-Send
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDCTS
CTS = Clear-to-Send
NAV = 15
NAV (Net Allocation Vector) = indicates remaining duration to keep silent
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDDATA
• DATA packet follows CTS. Successful data reception
acknowledged using ACK.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDACK
ACK = Acknowledgement packet
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
CSMA/CA with RTS/CTS (contd.)
C FA B EDACK
Reserved area for transmission betweennode C and D
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Limitations of IEEE 802.11 DCF MAC
• Performance of Basic Access Method (CSMA/CA) degrades due to
hidden and exposed node problems
• CSMA/CA with RTS/CTS – consumes additional bandwidth for
control packets transmission• may introduce significant delay in data packet
transmission if RTS/CTS control packets experience frequent collisions and retransmissions (possible in case of high node concentration)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Example: RTS/CTS packet collisions
A BRTS
CTSC
CTSRTS
RTSD
E
• Node C (which is hidden from node A) misses the CTS packet from node B due to a collision with an RTS packet from D
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Multi-Channel MAC
• Divides bandwidth into multiple channels using frequency division or by using orthogonal CDMA codes
• Selects any one of the idle channels
Advantages:• Improves throughput performance in the network by distributing traffic over time as well as over bandwidth
Disadvantages:• Increases hardware complexity
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Example: Single-channel/Multiple-Channel MAC Protocol
PEF
D
C
PAB
Ban
dwid
th
(a) Single Channeltime
PAB PCD PEF
PAB
PCD
PEF
Channel 1
Channel 2
Channel 3
time
Ban
dwid
th
(b) Multiple Channels (3 channels)
PCDA
B
E
F
• Node A, C and E are in radio range
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Use of Directional Antennas
• Wireless nodes traditionally use omni-directional antennas
e.g., IEEE 802.11.MAC• Disadvantage: Increases exposed node problem
RTS
CTS
A B C D
G
E
H
RTS
RTS
CTS
CTS
F
X
Reserved Area
Example: IEEE 802.11 MAC
Node B, E, G & H are exposed nodes, hence cannot communicate
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Example: Directional Antennas
• Node B only is exposed for communication between C & D• Communication between E & X is possible• Use of directional antennas reduces exposed terminals
C
D
E
XBA
G
H
F
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Directional Antennas: Advantages & Disadvantages
• Reduces interference to neighboring nodes- helps in frequency reuse- increases packet success probability (or reduces number of collisions)
• Higher gain due to their directivity- allows transmitters to operate at a smaller transmission power and still
maintain adequate signal-to-interference-plus-noise ratio (SINR)- reduces average power consumption in the nodes
• Requires a mechanism to determine direction for transmission and reception
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Energy Conservation
• Many wireless nodes are powered by batteries, hence needs MAC protocols which conserve energy
• Two approaches to reduce energy consumption
- power save: Turn off wireless interface when not required
- power control: Reduce transmit power
• Need for power-aware MAC protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Power Control
A B C D
Radio
rang
e
Fig.1
• When node C transmits to D at a higher power level, B cannot receive A’s transmission due to interference from C (Fig. 1)
A B C D
Fig. 2
• If node C reduces Tx power, it still communicates with D (Fig. 2)
- Reduces energy consumption at node C
- Allows B to receive A’s transmission (spatial reuse)
• Reduces interference and increases spatial reuse• Energy Saving
Radio
rang
e
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Routing Protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Importance of Routing in MANET• Host mobility
• link failure due to mobility of nodes
• Rate of link failure may be high when nodes move fast
• Some desirable features of routing protocols
• Minimum route discovery and maintenance time• Minimum routing overhead• Stable and optimum route despite mobility• Shortest route, etc.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Classification of Unicast Routing Protocols
STAR: Source Tree Adoptive Routing DSDV: Destination Sequence Distance Vector WRP: Wireless Routing Protocol OLSR: Optimized Link State Routing, CSGR: Cluster Switch Gateway Routing (CSGR) FSR : Fisheye State RoutingDSR: Dynamic Source Routing, ABR: Associativity Based Routing TORA: Temporally Ordered Routing, SSR : Signal Stability-based Routing AODV: Ad hoc On-Demand Distance Vector Routing LAR: Location Aided Routing, LANMAR: Landmark Ad hoc Routing Protocol ZRP: Zone Routing Protocol, PR: Preemptive Routing
STAR
Proactive Reactive Hybrid
DSDV WRP CSGR DSR AODV ZRPABR LANMARTORA LARSSROLSR FSR PR
Unicast Routing Protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Proactive Routing Protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Characteristics of Proactive Routing Protocols
• Distributed, shortest-path protocols
• Maintain routes between every host pair at all times
• Based on Periodic updates of routing table
• High routing overhead and consumes more bandwidth
• Example: Destination Sequence Distance Vector (DSDV)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Reactive Routing Protocols
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Characteristics of Reactive Routing Protocols
• Reactive protocols
• Determine route if and when needed
• Less control packet overhead
• Source initiates route discovery process
• More route discovery delay
• Example: Ad hoc On-Demand Distance Vector Routing (AODV)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Proactive and Reactive Protocol Trade-Off
• Latency of route discovery• Proactive protocols may have lower latency
since routes are maintained at all times• Reactive protocols may have higher latency
because a route from X to Y will be found only when X attempts to send a packet to Y
• Overhead of route discovery and maintenance• Reactive protocols may have lower overhead
since routes are determined only if needed• Proactive protocols may result in higher
overhead due to continuous route updating• Which approach achieves a better trade-off
depends on the traffic and mobility patterns
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Transmission Control Protocol
(TCP)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Transmission Control Protocol (TCP)
• Reliable ordered delivery
• Implements congestion avoidance and control
• Reliability achieved by means of retransmissions if necessary
• End-to-end semantics• Acknowledgements (ACKs) sent to TCP
sender confirm delivery of data received by TCP receiver
• ACK for data sent only after data has reached the destination
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
TCP in MANET
Several factors affect TCP performance in a MANET:
• Wireless transmission errors– may cause fast retransmit, which results in
• retransmission of a lost packet• reduction in congestion window size
– reducing congestion window in response to errors is unnecessary
• Route failures due to mobility
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Impact of Transmission Errors on TCP
• TCP cannot distinguish between packet losses due to congestion and mobility induced transmission errors
• Unnecessarily reduces congestion window size
• Throughput suffers
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
QoS Issues
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
• Guarantee by the network to satisfy a set of pre-determined service performance constraints for the user:
- end-to-end delay - throughput
- probability of packet loss- delay jitter (variance)
• Enough network resources must be available during service invocation to honor the guarantee
• Power consumption and service coverage area- other QoS attributes specific to MANET
• QoS support in MANETs encompasses issues at physical layer, MAC layer, network, transport and application layers
Quality-of-Service (QOS)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
QoS support in MANETs: Issues
• Unpredictable link properties
• Node mobility
• Limited battery life
• Hidden and exposed node problem
• Route maintenance
• Security
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Security Issues
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Security Issues in Mobile Ad Hoc Networks
• Wireless medium is easy to snoop
• Due to ad hoc connectivity and mobility, it is hard to guarantee access to any particular node
• Easier for trouble-makers to insert themselves into a mobile ad hoc network (as compared to a wired network)
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Open Issuesin
Mobile Ad Hoc Networking
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
Open Problems
• Better PHY layer required to support high speed services
• Efficient MAC protocols to support mobility, QoS, energy conservation, etc.
• Efficient routing protocols with scalability, QoS and security, etc.
• Security issues at other layers• Interoperation with Internet• Many more …
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
References
• C.E. Perkins, Ad Hoc Networking, Addison-Wesley, 2002
• E. Royer and C.K. Toh, “A Review of Current Routing Protocols for Ad hoc Mobile Wireless Networks,” IEEE Personal Communications Magazine, Vol. 6, Issue 2, pp. 46-55, 1999.
• C.E. Perkins, E.M. Royer, and Samir Das, “Ad hoc On-Demand Distance Vector Routing,” http://www.ietf.org/internet-drafts/draft-ietf-manet-aodv-13.txt, (work in progress), February 2003.
• L. Bajaj et al., “GloMoSim: A Scalable Network Simulation Environment,” CSD Technical Report, #990027, UCLA, 1997.
• IEEE Standards Department, Wireless LAN Medium Access Control (MAC) and PHYsical layer (PHY) specifications, IEEE standard 802.11-1997, 1997.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
References (contd.)
• B.P. Crow et al., “IEEE 802.11 Wireless Local Area Networks,” IEEE Communications Magazine, Vol. 35, Issue 9, pp. 116-126, September 1997.
• C-K. Toh, Ad Hoc Mobile Wireless Networks: Protocols and Systems, Prentice-Hall, 2002.
• Yiyan Wu and WilliumY. Zou, “Orthogonal Frequency Division Multiplexing,” IEEE Trans.Consumer electronics, vol.41, no.3, pp. 392-399, Aug. 1995.
• R.V. Nee and Ramjee Prasad, OFDM for Wireless Multimedia Communications, Artech House, Boston,London,2000.
• A.Chandra, V.Gummalla, J.O.Limb, “Wireless Medium Access Control Protocols,” IEEE Communications Survey, pp.2-15, Second Quarter 2000.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
References (contd.)
• Y. B. Ko, V. Shankarkumar, and N. H. Vaidya, “Medium Access Control Protocols using Directional Antennas in Ad hoc Networks,” In Proceedings of IEEE INFOCOM’2000, Mar. 2000.
• G.Gaertner, V.Cahill, “Understanding Link Quality in 802.11 Mobile Ad hoc Networks,” IEEE Internet computing, pp. 55-60, Jan.-Feb. 2004.
• X.Shugong,T.Saadawi,“Does the IEEE MAC protocol work well in multi-hop wireless ad hoc networks?” IEEE Comm. magazine, pp. 130-137,June 2001.
• M.Tubaishat, S.Madria, ”Sensor networks: an overview,” IEEE potentials, pp.20-23,April-May-2003.
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar
References (contd.)
• Prasant Mohapatra, J.Li, Chao Gui,” QoS in Mobile Ad hoc Networks,” IEEE Wireless Communication, pp.44-52,June-2003.
• N,Choi,Y.Seok,Y.Choi, “Multi-channel MAC for Mobile Ad hoc Networks,” Proc.VTC’03, pp.1379-1383, Oct. 2003.
• C. Rama Krishna, S. Chakrabarti, and D. Datta, “A Modified Backoff Algorithm for IEEE 802.11 DCF-based MAC Protocol in a Mobile Ad hoc Network,” Proc. of the International Conference IEEE TENCON 2004, Chiang Mai, Thailand, 21-24 November 2004.
• V. Bhargavan et al., “MACAW: A New Media Access Protocol for Wireless LANs,” Proc. of ACM SIGCOMM, pp. 212-225, 1994.
• P. Karn, “MACA – A New Channel Access Method for Packet Radio,” in ARRL/CRRL Amateur Radio 9th Computer Networking Conference, pp. 134-140, 1990
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National Workshop on C. Rama Krishna NITTTR, ChandigarhMobile Communication Technology & Networking (MCTN-09)on March 14, 2009 at KIST, Bhubaneswar