This document discusses the properties and spectrum needs of nodes in a mobile ad-hoc network (MANET). Key properties of MANETs include flexible network architecture, variable routing paths due to limited wireless range, neighbor discovery abilities, and protocol diversity between nodes. Spectrum needs at nodes are also variable due to their mobility and ability to reuse frequencies. Individual nodes in a MANET require much smaller spectrum needs than those in a fixed infrastructure network due to multi-hop routing and spatial frequency reuse between low-power transmissions.

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Mobile Ad-hoc and Sensor Networks
Lesson 02
Mobile Ad-hoc Network (MANET)
Properties and Spectrum needs at the
nodes

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MANET Properties
• Seamless interaction and ubiquitous
mobile computing environment
• Seamless connectivity maintained
between the devices when they move
with the nearby wireless nodes, sensor
nodes, and embedded devices in
automobiles

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MANET Properties
• Neighbour discovery─ One of the
important characteristics of a MANET
node
• Data routing abilities ─ data can be
routed from a source node to a
neighbouring node

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MANET Properties
• Flexible network architecture and
variable routing paths ─ to provide
communication in case of the limited
wireless connectivity range and resource
constraints

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MANET Properties
• Flexibility─ enables fast establishment of
networks
• When a new network is to be
established, the only requirement is to
provide a new set of nodes with limited
wireless communication range
• A node has limited capability, that is, it
can connect only to the nodes which are
nearby and thus consumes limited power

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MANET Properties
• Using a service discovery protocol, a
node discovers the service of a nearby
node and communicates to a remote
node in the MANET
• Peer-to-Peer connectivity

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MANET Properties
• Computations decentralization─
independent computational, switching (or
routing), and communication capabilities

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MANET Properties
• Limited wireless connectivity range─
require that a node should move in the
vicinity of at least one nearby node within
the wireless communication range, else
the node should be provided with the
access-point of wired communication

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MANET Properties
• Weak connectivity and remote server
latency
• Unreliable links to base station or
gateway ─ failure of an intermediate
node results in greater latency in
communicating with the remote server

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MANET PROPERTIES
• Resource constraints─ Limited
bandwidth available between two
intermediate nodes
• Node may have limited power and thus
computations need to be energy-efficient

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MANET PROPERTIES
• No need of access-point
• Only selected access-points provided for
connection to other networks or other
MANETs

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MANET PROPERTIES
• Need to solve exposed or hidden
terminal problem
• Diversity in nodes─ iPods, palm
handheld computers, Smartphones, PCs,
smart labels, smart sensors, and
automobile-embedded systems

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MANET PROPERTIES
• Protocol diversity─ Nodes can use
different protocols, for example, IrDA,
Bluetooth, ZigBee, 802.11, GSM, or
TCP/IP
• Data caching, saving, and aggregation at
node

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Bandwidth of an access-point-based
fixed infrastructure network
• Large number devices connects to a
centralized server
• The bandwidth requirement too high
• N devices using FDMA in duplex
transmission, then the required
bandwidth will be 2 × N × fbw0, where fbw0
is the bandwidth allotted to one device
for sending a packet to its access-point

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Bandwidth of an access-point-based
fixed infrastructure network
• Using TDMA and SDMA, the bandwidth
(spectrum) requirement is reduced

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Spectrum requirement at Nodes in
MANET
• Each MANET node has much smaller
frequency spectrum requirements than
that for a node in a fixed infrastructure
network

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Mobile ad-hoc network (MANET)
Nodes A to G

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Spectrum requirement at Nodes in
MANET
• A node itself ─ a router for all the packets
coming from or going to the other nodes
• Node D at a given instant─ Can get
incoming packets from E, F, G, and A
and can send packets to C and A or vice
versa

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Spectrum requirement at Nodes in
MANET
• Nodes are themselves mobile
• Therefore, bandwidth available to any
node at any instant is variable
• MANET enables spectrum reuse

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Spectrum requirement at Nodes in
MANET
• Each wireless link provides a limited
bandwidth
• MANET communication is multi-hop
• When node D transmits to G, it is
through the three hops(i) DE, (ii)
EF, and (iii) FG.

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Each node has low and adaptable
transmission power
• Optimized to have signal strength just
sufficient to carry the signal up to single
hop
• Hops can therefore occur simultaneously
using the same frequency band

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Each node has low and adaptable
transmission power
• There is spatial reuse of bandwidth
• Also, the bandwidth depends on
surrounding environment

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Bandwidth Need computations
• Assume FDMA mode access by a node
• The bandwidth depends on the number
of next hop neighbours
• The node with higher number of next hop
neighbours require higher bandwidth in
FDMA
• The nodes D, E, and G shall need higher
bandwidth compared to C and F

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Bandwidth Need computations
• Bandwidth required will be 2 × 3 × fbw0
when three nodes D, E, or G can
transmit in full duplex mode to all the
nodes
• Will be 2 × 2 × fbw0 for two nodes C or F
• When each node path and each direction
hop scheduled to operate at different
instants, as in TDMA, then the bandwidth
required will be just fbw0

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Summary
• MANET node’s Neighbour discovery
• Data routing abilities
• Flexible network architecture
• Variable routing paths to provide
communication
• Limited wireless connectivity range and
resource constraints
…

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… Summary
• Protocol diversity
• Nodes diversity
• Weak connectivity
• Limited spectrum requirements
• Multi-hop transmission

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End of Lesson 02
Mobile Ad-hoc Network (MANET)
Properties and Spectrum needs at the
nodes