April 10, 2023 1

Mobile Computing COE 446

Mobile Ad hoc NetworksTarek Sheltami

KFUPMCCSECOE

http://faculty.kfupm.edu.sa/coe/tarek/coe446.htm

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Many Applications Personal area networking

cell phone, laptop, ear phone, wrist watch Military environments

soldiers, tanks, planes Civilian environments

taxi cab network meeting rooms sports stadiums boats, small aircraft

Emergency operations search-and-rescue policing and fire fighting

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Why Ad hoc Networks? No infrastructure needed (no routing in fixed

wireless) Can be deployed quickly, where there is no

wireless communication infrastructure present Can act as an extension to existing networks

enhances coverage Cost-effective – cellular spectrum costs $XX

billion Adaptive computing and self-configuring Support for heterogeneous computational

devices and OSs

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Ad hoc Constraints

Dynamic topologies Bandwidth-constrained Constraints on Tx power Infrastructure-less property, no central

coordinators hidden terminal, exposed terminal

No QoS preservation Load balancing Energy-constrained operation Limited physical security

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Background

Table-driven routing protocols Routing Disadvantages

On-demand routing protocols Routing Disadvantages

Cluster-based routing protocols (Laura Feeney, Infocom 2001)

Routing Disadvantages

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DSDV Routing Protocol

2 13 44 46 15

DEST Next hop1 4

5

1 13 59 8

10 12

DEST Next hop

1

Source

Destination

2 13 34 47 9

DEST Next hop

3

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DSDV Routing Protocol (Cont’d)

2 1

3 4

DESTNexthop

Metric#

4

Seq #

8

2 1

3 4

DESTNexthop

Metric#

4

Seq #

8

2 1

3 4

DESTNexthop

Metric#

4

Seq #

8

DEST 2Next hop 3Metric # 4

Sequence # 7

DEST 2Next hop 3Metric # 6

Sequence # 8

DEST 2Next hop 16Metric # 9

Sequence # 9

+

+

+

=

=

=

Ignore update

Ignore update

2 163 4

DESTNexthop

Metric#

9

Seq #

9

Table Updated

ReturnReturn

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Disadvantages of Table Driven Protocols

Routing is achieved by using routing tables maintained by each node The bulk of the complexity in

generating and maintaining these routing tables

If the topological changes are very frequent, incremental updates will grow in size

ReturnReturn

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1

2

3

4

5

6

7

8

S

D

On-demand Routing Protocol (DSR)

1,8

1,8

1,3,8

1,2,8

1,3,8

1,3,

4,7,

8

1,2,5,8

1,3,

4,8

1,3,4,8

1,3,6,8

8,5,2,15,2,1

2,1

XDAT

A

DATA

DATA

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timeout

AODV Routing Protocol

1

2

3

4

5

6

7

8

D

S

X

X

DATA

DATA

DATA

DATA

DATA

ReturnReturn

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Disadvantages of On-demand Protocols

Not scalable to large networks, because of the source routing requirement. Furthermore, the need to place the

entire route in both route replies and data packets causes a significant

overhead. Some of them requires symmetric links

between nodes, and hence cannot utilize routes with asymmetric links. ReturnReturn

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Cluster-based Routing

Transmission Range of MT 1

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Cluster-based Routing..

3

1

2 6

4

5

7

Range of MT 1

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Cooperative Routing vs Direct Sending

In simple radio model, a radio dissipates Eele = 50 nJ/bit at the sender and receiver sides. Let us assume the d is the distance between the source and destination, then, the energy loss is d2. The transmit amplifier at the sender consumes Eampd2, where Eamp = 100 pJ/bit/m2. Therefore, from the sender side, to send one bit at distance d, the required power is Eele + Eampd2, whereas at the receiver will need is Eele only. Normalizing both by dividing by Eamp:

Pt = E + d2 and Pr = E, where Pt and Pr are the normalized transmission and reception power respectively, and E = Eele / Eamp = 500m2

At the HCB-model, the power needed for transmission and reception at distance d is:

u(d) = Pt + Pr = 2E + d2

u(d) = adu(d) = adαα + c + c

Power-aware localized routing in wireless networks Stojmenovic, I.; Lin, X.; Parallel and Distributed Systems, IEEE Transactions on Volume 12, Issue 11, Nov. 2001 Page(s):1122 – 1133

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Where in HCB-model α = 2, a = 1, and c = 2E = 1,000 Let us assume that the source S can reach the destination D

directly. Let us further assume that there is a middle node between the source and the destination. Let |SA| = x and |SD| = d as in the below Figure

If d > (c/(a(1-2d > (c/(a(1-21-α1-α))))))1/α1/α, then there is an intermediate node A between the source and destination such that the retransmission of the packet through A will save the energy. Moreover, the greatest saving is achieved when A in the middle of SD.

S x d - x

d

S A D

Cooperative Routing vs Direct Sending..

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Also if d > (c/(a(1-2d > (c/(a(1-21-α1-α))))))1/α1/α, then the greatest power saving are obtained when the interval SD is divided into n > 1 equal subintervals, where n is the nearest integer to d(a(α-1)/c)d(a(α-1)/c)1/α1/α.

Cooperative Routing vs Direct Sending..

S

d

S D

S d/nd/n d/nd/n

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Now the power needed for direct transmission is u(d) = adu(d) = adαα + c + c , which is optimal when d≤d≤(c/(a(1-2(c/(a(1-21-α1-α))))))1/α1/α, otherwise when d>d>(c/(a(1-2(c/(a(1-21-α1-α))))))1/α1/α, n-1 is equally spaced nodes can be selected for transmission,

Where, n = d(a(α-1)/c)n = d(a(α-1)/c)1/α1/α The minimal power:v(d) = dc(a(α-1)/c)v(d) = dc(a(α-1)/c)1/α1/α + da(a(α-1)/c) + da(a(α-1)/c)(1-α)/α(1-α)/α

Cooperative Routing vs Direct Sending..