The document discusses ad hoc networks and wireless sensor networks. It defines an ad hoc network as a temporary network composed of mobile nodes without preexisting infrastructure that is self-organizing. Wireless sensor networks are introduced as a collection of sensor nodes densely deployed to monitor conditions and cooperatively pass data back to central nodes. The document outlines key characteristics of both networks including their temporary and adaptive nature, multi-hop routing, and challenges of mobility, power constraints, and dynamic topology changes.

1. Chandra Prakash
Assistant Professor
LPU
Ad Hoc Network
Lecture (5-6)
1

2. Introduction
Introduction - Ad Hoc Network definition
Characteristic/features and application
Heterogeneity in Mobile Devices
Wireless Sensor Networks
Traffic Profiles
Types ofAd Hoc Mobile Communications
Types of Mobile Host Movements
Challenges FacingAd Hoc Mobile Networks
Issues and Challenges Facing Ad Hoc Mobile network
Ad Hoc wireless Internet
2

3. A BSS without an AP is called an ad hoc network;
a BSS with an AP is called an infrastructure network.
3

4. Ad hoc networks
 Temporary network composed of mobile nodes without preexisting
communication infrastructure, such as Access Point (AP) and Base Station
(BS).
 Each node plays the role of router for multi-hop routing.
 Self-organizing network without infrastructure networks
 Started from DARPA PRNet in 1970
 Cooperative nodes (wireless)
 Each node decode-and-forward packets for other nodes
 Multi-hop packet forwarding through wireless links
 Proactive/reactive/hybrid routing protocols
 Most works based on CSMA/CA to solve the interference problem
 IEEE 802.11 MAC
4

5. What Is an Ad Hoc Network?
 An ad hoc wireless network
 collection of two or more devices equipped with
wireless communications and networking capability.
 Such devices can communicate with another node that is
immediately within their radio range or one that is outside
their radio range.
 For the latter scenario, an intermediate node is used to relay or
forward the packet from the source toward the destination.
 Since an ad hoc wireless network does not rely on any fixed
network entities, the network itself is essentially infrastructure-
less.There is no need for any fixed radio base stations, no wires or
fixed routers.
5

6. (cont…)
 An ad hoc wireless network is self-organizing and adaptive.
 This means that a formed network can be de-formed on-the-
fly without the need for any system administration.
 The term "ad hoc" tends to imply "can take different
forms" and "can be mobile, standalone, or
networked.“
 Ad hoc nodes or devices should be able to detect the
presence of other such devices and to perform the necessary
handshaking to allow communications and the sharing of
information and services.
6

7. Wireless Ad-hoc Network
 A wireless ad-hoc network is a decentralized type
of wireless network.
 The network is ad hoc because it does not rely on a pre-
existing infrastructure, such as routers in wired networks
or access points in managed (infrastructure) wireless
networks.
 Each node participates in routing by forwarding data for other
nodes, and so the determination of which nodes forward data
is made dynamically based on the network connectivity.
 In addition to the classic routing, ad hoc networks can
use flooding for forwarding the data.
7

8. Mobile Ad Hoc Networks (MANET)
Mobile nodes
Access points
Backbone
Wireless Mobile Network
MANET
8

9. Mobile Ad-hoc Network
 Self-configuring network of mobile routers (and associated
hosts) connected by wireless links
 This union forms a random topology
 Routers move randomly free
 Topology changes rapidly and unpredictably
 Standalone fashion or connected to the larger Internet
 While MANETs are self contained, they can also be tied to an
IP-based global or local network – Hybrid MANETs
 Suitable for emergency situations like natural or human-induced
disasters, military conflicts, emergency medical situations, etc.
9

10. Cellular and ad hoc wireless networks
10

11. Comparison of wireless cellular and wireless ad-hoc network
concepts
11

12. MANET Application
Applications Descriptions/Services
Tactical Networks •Military communication, operations
•Coordination of military object moving at high speeds such as fleets
of airplanes or ships
•Automated battlefields
Sensor networks •Collection of embedded sensor devices used to collect real time data
to automate everyday functions. Data highly correlated in time and
space, e.g., remote sensors for weather, earth activities; sensors for
manufacturing equipments.
•Can have between 1000 -100,000 nodes, each node collecting sample
data, then forwarding data to centralized host for processing using low
homogeneous rates.
Emergency
services
•Search, rescue, crowd control, and commando operations as well as
disaster recovery
•for e.g. Early retrieval and transmission of patient data ( record,
status, diagnosis ) from /to the hospital
•Replacement of a fixed infrastructure in case of earthquakes,
hurricanes, fire etc.12

13. MANET Application
Applications Descriptions/Services
Commercial
environments
•E-commerce, e.g., electronic payments from anywhere (i.e., in taxi).
•Business:
dynamic access to customer files stored in a central location
on the fly provide consistent databases for all agents
Mobile office
•Vehicular services:
transmission of news ,road conditions ,weather, music
local ad hoc network with nearby vehicles for road/accident
guidance
Home and
enterprise
networking
•Home/office wireless networking(WLAN), e.g., shared whiteboard
application, use PDA to print anywhere, trade shows
•Personal area network (PAN)
Educational
applications
•Set up virtual classrooms or conference rooms
•Set up ad hoc communication during conferences, meetings, or
lectures13

14. MANET Application
Applications Descriptions/Services
Entertainment Multiuser games
Robotic pets
outdoor internet access
Location- aware
Services
Follow- on services, e.g., automatic call forwarding, transmission of the
actual workspace to the current location
Information services
push, e.g., advertise location-specific services, like gas stations
pull, e.g., location-dependent travel guide; services( printer, fax,
phone, server, gas stations) availability information; caches,
intermediate results, state information, etc.
14

15. Issues in Ad-Hoc
 Ad hoc wireless devices can take different forms (for example,
palmtop, laptop, Internet mobile phone, etc.), the computation,
storage, and communications capabilities and
interoperability of such devices will vary tremendously.
 Ad hoc devices should not only detect the presence of connectivity
with neighbouring devices/nodes, but also identify what type the
devices are and their corresponding attributes.
 Due to the presence of mobility, routing information will have to
change to reflect changes in link connectivity.
 The diversity of ad hoc mobile devices also implies that the battery
capacity of such devices will also vary. Since ad hoc networks rely on
forwarding data packets sent by other nodes, power consumption
becomes a critical issue.15

16. Heterogeneity in Mobile Devices
(a) Heterogeneous mobile device ad hoc networks, and (b) homogeneous ad hoc
network comprising powerful laptop computers.16

17. Heterogeneity in Mobile Devices
 The presence of heterogeneity implies that some devices are
more powerful than others, and some can be servers while
others can only be clients.
 It is evident that there are differences in size, computational
power, memory, disk, and battery capacity.
 Mobile devices can exist in many forms.There are great
differences among these devices,
 heterogeneity can affect communication performance and
the design of communication protocols.
17

18. Characteristics of some existing
mobile devices
18

19. Heterogeneity in Mobile Devices
 Come in different favours:
 Sensor Network
 PersonalArea Network
 Traditional MobileAd Hoc Network
19

20. WIRELESS SENSOR NETWORK
20

21. INTRODUCTION TO WSN
 A wireless sensor network is one form of an ad hoc wireless
network.
 A sensor network is a collection of a large number of
sensor nodes that are deployed in a particular region.
 Sensors are wirelessly connected and they, at appropriate times, relay
information back to some selected nodes.
 These selected nodes then perform some computation based on the
collected data to derive an ultimate statistic to allow critical
decisions to be made.
 There are a variety of sensors, including acoustic(sound related) ,
seismic (Subject to an earthquake or earth vibration), image, heat,
direction, smoke, and temperature sensors.
21

22. Basic features of sensor networks
 A large number of low-cost, low-power, multifunctional, and small sensor
nodes
 Sensor node consists of sensing, data processing, and communicating
components
 A sensor network is composed of a large number of sensor nodes,
 which are densely deployed either inside the phenomenon or very close
to it.
 The position of sensor nodes need not be engineered or pre-determined.
 sensor network protocols and algorithms must possess self-organizing
capabilities.
22

23. Basic features of sensor networks
 Self-organizing capabilities
 Short-range broadcast communication and multihop routing
 Dense deployment and cooperative effort of sensor nodes
 Frequently changing topology due to fading and node
failures
 Limitations in energy, transmit power, memory, and computing
power
23

24. Wireless Sensor Networks
 A sort of ad-hoc networks
 A network of low cost,
densely deployed,
untethered sensor nodes
 Application areas:
heath, military, and home
 Placed in inaccessible terrains or disaster areas
 It may be impossible to recharge batteries
 Different Node Characteristics fromTraditional nodes
 No of nodes in a sensor network can be several orders of magnitude higher than
the nodes in an Ad Hoc network (100s to 1000s nodes)
 Densely deployed (20 nodes/m3)
 Mobility of nodes is not mendatory
 Prone to failures
 Topology changes very frequently
 Mainly use a broadcast communication, whereas most Ad Hoc networks are based
on point-to-point
 Limited in power, computing capacities, and memory
 May not have global ID because of the large amount of overhead and large number
of sensors
Ad Hoc Net
Wireless
Sensor
Network
24

25. Existing Wireless Net vs. Sensor Net
Cellular system Bluetooth, MANET Sensor Network
Single Hop Multi-hop Multi-hop
High QOS
Bandwidth efficiency
High QOS Power conservation
Limited bandwidth
Large number of node
Narrow radio range
Frequent topology change
Station to Base station Peer to peer
Peer to multi node
Peer to multi node
25

26. Factors influencing sensor network design
 Fault tolerance;
 Scalability;
 Production costs;
 Operating environment;
 Sensor network topology;
 Hardware constraints;
 Transmission media;
 Power consumption.
26

27. Sensor Network Model
SourceStimulus
Sink
Sink
27

28. Sensor Networks Architecture
 Sensor node
 Made up of four basic components
 Sensing unit, Processing unit,Transceiver unit, and Power unit
 Additional application-dependent components
 Location finding system, power generator, and mobilizer
 Scattered in a sensor field
 Collect data and route data back to the sink
 Sink
 Communicate with the task manager node (user) via Internet
or satellite
28

29. Components of Sensor Node
A sensor node is made up of four basic components
 sensing unit
 usually composed of two subunits: sensors and analog to digital converters
(ADCs).
 processing unit,
 Manages the procedures that make the sensor node collaborate with the other
nodes to carry out the assigned sensing tasks.
 Transceiver unit
 Connects the node to the network.
 Power units (the most important unit)
29

30. Sensor network topology
 Pre-deployment and deployment phase
 Sensor nodes can be either thrown in mass or placed one by one in
the sensor field.
 Post-deployment phase
 Sensor network topologies are prone to frequent changes after
deployment.
 Re-deployment of additional nodes phase
 Addition of new nodes poses a need to re-organize the network.
30

31. DEPLOYMENT OF NODES IN WSN
Deploy
Sensors
31

32. Environment
 Sensor nodes may be working
 in busy intersections,
 in the interior of a large machinery,
 at the bottom of an ocean,
 inside a twister,
 in a battlefield beyond the enemy lines,
 in a home or a large building
Transmission media
 Industrial, scientific and medical (ISM) bands
 offer license-free communication in most countries.
 Infrared
 License-free and robust to interference
 requirement of a line of sight between sender and receiver
32

33. Micro-sensors
 Uses
 In military: surveillance and target tracing
 health-care industry: allow continuous monitoring of life-
critical information.
 food industry: biosensor technology applied to quality control
can help prevent rejected products from being shipped out,
 Agriculture: help to determine the quality of soil and moisture
level; they can also detect other bio-related compounds.
 Sensors are also widely used for environmental and weather
information gathering.They enable us to make preparations in
times of bad weather and natural disaster.
33

34. APPLICATIONS OF WSN
34

35. Wireless Mesh Networks
 Mesh networking is the holy grail of wireless networking.
“Mesh” refers to many types of technology that enable
wireless systems to automatically find each other and self-
configure themselves to route information amongst
themselves.
35

36. 36
Wireless Mesh Networks
 Mesh network implemented over
WLAN
 “Mesh” refers to many types of
technology that enable wireless
systems to automatically find each
other and self-configure themselves to
route information amongst themselves.
 Industrial standardsActivities
 IEEE 802.11, IEEE 802.15, IEEE
801.16 have established sub-working
groups to focus on new standards for
WMNs

37.  In a wireless mesh network, the network connection is spread out among
dozens or even hundreds of wireless mesh nodes that "talk" to each other
to share the network connection across a large area.
 Mesh nodes are small radio transmitters that function in the same way as a
wireless router.
 In a wireless mesh network, only one node needs to be physically
wired to a network connection like a DSL Internet modem.That
one wired node then shares its Internet connection wirelessly with all other
nodes in its vicinity.Those nodes then share the connection wirelessly with
the nodes closest to them.The more nodes, the further the connection
spreads, creating a wireless "cloud of connectivity" that can serve a small
office or a city of millions.
37

38. Wireless Mesh Networks
 Possible deployment scenarios:
 Residential zone : where broadband connectivity is required
 Highway: where a communication facility for moving automobiles
is required
 Business zones: where an alternative communication system to
cellular network is required
 Important civilian regions: where a high degree of service
availability is required
 University campus: where inexpensive campus wide network
coverage can be provided.
Operates at license-free ISM band -2.4 GHz and 5 GHz.
Speed - 2Mbps to 60 Mbps38

39. 39

40. Benefits
 Using fewer wires means it costs less to set up a network, particularly for large areas of coverage.
 The more nodes you install, the bigger and faster your wireless network becomes.
 They rely on the same WiFi standards (802.11a, b and g) already in place for most wireless
networks.
 They are convenient where Ethernet wall connections are lacking -- for instance, in
outdoor concert venues, warehouses or transportation settings.
 They are useful for Non-Line-of-Sight (NLoS) network configurations where wireless
signals are intermittently blocked. For example, in an amusement park a Ferris wheel occasionally
blocks the signal from a wireless access point.
 Wireless mesh configurations allow local networks to run faster, because local packets don't
have to travel back to a central server.
 Wireless mesh nodes are easy to install and uninstall, making the network extremely adaptable and
expandable as more or less coverage is needed.
40

41.  Electric meters now being deployed on residences transfer their readings from
one to another and eventually to the central office for billing without the need
for human meter readers or the need to connect the meters with cables.
 Mesh networks are "self configuring;" the network automatically incorporates a
new node into the existing structure without needing any adjustments by a
network administrator.
 Mesh networks are "self healing," since the network automatically finds the
fastest and most reliable paths to send data, even if nodes are blocked or lose
their signal.
41

42. 42
Taxonomy
Wireless
Networking
Multi-hop
Infrastructure-less
(ad-hoc)
Infrastructure-based
(Hybrid)
Infrastructure-less
(MANET)
Single
Hop
Cellular
Networks Wireless Sensor
Networks
Wireless Mesh
Networks
Car-to-car
Networks
(VANETs)
Infrastructure-based
(hub&spoke)
802.11 802.16 Bluetooth802.11

43. 43
Mesh vs. Ad-Hoc Networks
 Multihop
 Nodes are wireless, possibly
mobile
 May rely on infrastructure
 Most traffic is user-to-user
Ad-Hoc Networks Wireless Mesh Networks
 Multihop
 Nodes are wireless,
some mobile, some
fixed
 It relies on
infrastructure
 Most traffic is user-
to-gateway

44. 44
Mesh vs. Sensor Networks
 Bandwidth is limited (tens of kbps)
 In most applications, fixed nodes
 Energy efficiency is an issue
 Resource constrained
 Most traffic is user-to-gateway
Wireless Sensor Networks Wireless Mesh Networks
 Bandwidth is generous (>1Mbps)
 Some nodes mobile, some fixed
 Normally not energy limited
 Resources are not an issue
 Most traffic is user-to-gateway

45. 45
Broadband Internet Access

46. 46
Extend WLAN Coverage
Source: www.belair.com
Source: www.meshdynamics.com

47. 47
WMN Architecture
 WMNs (Wireless Mesh Networks) consist of:
 mesh routers and mesh clients
 Mesh routers
 Conventional wireless AP (Access Point) functions
 Additional mesh routing functions to support multi-hop communications
 Usually multiple wireless interfaces built on either the same or different
radio technologies
 Mesh clients
 Can also work as a router for clientWMN
 Usually one wireless interface
 Classification ofWMN architecture
 Infrastructure/BackboneWMNs
 ClientWMNs
 HybridWMNs

48. 48
Infrastructure/backbone WMNs
Internet
Wi-Fi
Networks
Cellular
Networks WiMAX
Networks
Sensor
NetworksBase Station
Sink node
Sensor
Wireless Mesh
Backbone
Wired Clients
Mesh RouterMesh Router
with Gateway
Mesh Router
with Gateway
Mesh Router
with Gateway/Bridge
Mesh Router
with Gateway/Bridge
Mesh Router
with Gateway/Bridge
Access Point
Base Station
Mesh Router
with Gateway/Bridge
Wireless Clients

49. 49
Client WMNs
Mesh Client
Mesh Client
Mesh Client

50. 50
Hybrid WMNs
Wi-Fi, Wi-MAX,
Sensor Networks,
Cellular Networks, etc.
Internet
Wireless Mesh Clients
Wireless Mesh
Backbone
Conventional Clients
Mesh Router
Mesh Router
Mesh Router
with Gateway
Mesh Router
with Gateway
Mesh Router
with Gateway/Bridge
Mesh Router Mesh Router
Mesh Router
with Gateway/Bridge

51. Types of Ad Hoc Mobile
Communications
 Mobile hosts in an ad hoc mobile network can communicate
with their immediate peers (peer-to-peer) that are a single
radio hop away.
 If three or more nodes are within range of each other (but
not necessarily a single hop away from one another), then
remote-to-remote mobile node communications
exist.
 Remote-to-remote communications are associated with
group migrations.
51

52. Types of traffic patterns in Adhoc
Ad hoc wireless communications can occur in several different
forms.
1) Peer-to-peer communication
 Mobile host communicates in pair
 For a pair of ad hoc wireless nodes, communications will occur
between them over a period of time until the session is
finished or one of the nodes has moved away.
2) Remote-to-remote communication
 when two or more devices are communicating among
themselves and they are migrating in groups.
 The traffic pattern is, therefore, one where communications
occur over a longer period of time.
52

53. Types of traffic patterns in Adhoc
3) Hybrid Communication
 have a scenario where devices communicate in a non-
coherent fashion and their communication sessions are,
therefore, short, abrupt, and undeterministic.
MH: Mobile host
53

54. Types of Mobile Host Movements
 Movements by Nodes in a Route
 Movements by Subnet-Bridging Nodes
 Concurrent Node Movements
54

55. Movements by Nodes in a Route
Source nodes
Downstream
link
Intermediate
nodes
Destination
nodes
Upstream
link
55

56. Cont…
An ad hoc route comprises the source (SRC), destination (DEST), and/or a
number of intermediate nodes (INs).
 Movement by any of these nodes will affect the validity of the route.
 An SRC node
 has a downstream link, and
 when moves out of its downstream neighbour's radio coverage range, the existing
route will immediately become invalid.
 all downstream nodes may have to be informed so they can erase their invalid route
entries.
 DEST node
 moves out of the radio coverage of its upstream neighbour, the route becomes
invalid.
 The upsteam nodes will have to be informed so they can erase their invalid route
entries.
 IN node : any movement by an IN supporting an existing route may cause the
route to be invalid.
56

57.  Movements cause many conventional distributed routing
protocols to respond in sympathy with the link changes.
 Need to update all the remaining nodes within the network
so that consistent routing information can be maintained.
 Updating process involves broadcasting over the
wireless medium, which results in wasteful bandwidth and
an increase in overall network control traffic. Hence, new
routing protocols are needed.
57

58. Movements by Subnet-Bridging Nodes
 Subnet-bridging node movement
between two mobile subnets can
fragment the mobile subnet into
smaller subnets
 Movements by certain nodes can
result in subnets merging (yielding
bigger subnets) while sometimes
subnet is partitioned by some subnet-
bridging mobile nodes
 Updating all the nodes' routing tables
 Choose to update only the affected
nodes' association tables.
58

59.  Concurrent movements by nodes (SRC, DEST, or
INs)
 Ensure there is consistency when multiple route
reconfiguration or repair processes are invoked.
 Ultimately converge where the most appropriate
route reconfiguration is performed.
Concurrent Node Movements
59

60. Challenges in Ad Hoc Networks
 Limited wireless transmission range
 Broadcast nature of the wireless medium
 Packet losses due to transmission errors
 Mobility-induced route changes
 Mobility-induced packet losses
 Battery constraints
 Potentially frequent network partitions
 Ease of snooping on wireless transmissions (security hazard)
60

61. Issues in Ad Hoc Networks
1. SpectrumAllocation and Purchase
2. Medium access scheme
3. Routing
4. Multicasting
5. Transport layer protocol Performance
6. Pricing shceme
7. QoS provisioning
8. Security
9. Energy management
10. Addressing and service discovery
11. Scalability
12. Deployment considerations61

62. 1. Spectrum Allocation and Purchase
 FCC control the regulations regarding the use of radio
spectrum.
 Who regulates the use of radio spectrum in INDIA??
 To prevent interference, ad hoc networks operate over
some form of allowed or specified spectrum range.
 Most microwave ovens operate in the 2.4GHz band, which
can therefore interfere with wireless LAN systems.
 Frequency spectrum is not only tightly controlled and
allocated, but it also needs to be purchased.
 With ad hoc networks capable of forming and deforming on-
the-fly, it is not clear who should pay for this spectrum.
62

63. 63
2.Medium Access Scheme
 Distributed operation
 Synchronization
 Hidden terminal problem
 Exposed terminal problem
 Throughput
 Access delay
 Fairness: especially for relaying nodes
 Real-time traffic support
 Resource reservation
 Ability to measure resource availability
 Capability for power control
 Adaptive rate control
 Use of directional antennas

64. Media Access
 TDMA and FDMA schemes are not suitable.
 Many MAC (Media Access Control) protocols do not deal with host
mobility.
 The scheduling of frames for timely transmission to support QoS is difficult.
 In ad hoc wireless networks, since the same media are shared by multiple
mobile ad hoc nodes, access to the common channel must be made in a
distributed fashion, through the presence of a MAC protocol.
 There are no static nodes, nodes cannot rely on a centralized coordinator.
The MAC protocol must contend for access to the channel while at the same
time avoiding possible collisions with neighboring nodes.
 The presence of mobility, hidden terminals, and exposed nodes
problems must be accounted for when it comes to designing MAC
protocols for ad hoc wireless networks.
64

65. 65
Difference Between Wired and
Wireless
 If both A and C sense the channel to be idle at the same time, they send
at the same time.
 Collision can be detected at sender in Ethernet.
 Half-duplex radios in wireless cannot detect collision at
sender.
A B C
A
B
C
Ethernet LAN Wireless LAN

66. IEEE has defined the specifications for a wireless LAN, called IEEE
802.11, which covers the physical and data link layers.
In IEEE 802.11, carrier sensing is performed
at the air interface (physical carrier sensing), and
at the MAC layer (virtual carrier sensing)
Physical carrier sensing
detects presence of other users by analyzing all detected packets
Detects activity in the channel via relative signal strength from other
sources
Virtual carrier sensing is done by sending MPDU duration information in
the header of RTS/CTS and data frames
Channel is busy if either mechanisms indicate it to be
Duration field indicates the amount of time (in microseconds) required to
complete frame transmission
Stations in the BSS use the information in the duration field to adjust their
network allocation vector (NAV)
802.11 - Carrier Sensing
66

67.  A and C cannot hear each other.
 A sends to B, C cannot receiveA.
 C wants to send to B, C senses a “free” medium.
 Collision occurs at B.
 A cannot receive the collision.
 A is “hidden” for C.
Hidden Terminal Problem
BA C
67

68. Exposed Terminal Problem
 A starts sending to B.
 C senses carrier, finds medium in
use and has to wait for A->B to
end.
 D is outside the range of A,
therefore waiting is not necessary.
 A and C are “exposed” terminals
A B
C
D
68

69. 69
3. Routing
 Challenges
 Mobility
 results in path breaks, packet collisions, transient loops, stale routing
information, and difficulty in resource reservation
 BW constraints
 Error-prone and shred channel
 Bit error rate BER: 10-5
~ 10-3
wireless vs. 10-12
~ 10-9
wired
 Location-dependent contention
 Distribute load uniformly

70. Routing
 The presence of mobility implies that links make and break often and in an
indeterministic fashion.
 Classical distributed Bellman-Ford routing algorithm is used to
maintain and update routing information in a packet radio network.
 Yet distance-vector-based routing not designed for wireless networks,
still applicable to packet radio networks since the rate of mobility is not
high.
 Mobile devices are now small, portable, and highly integrated.
 Ad hoc mobile networks are different from packet radio networks since
nodes can move more freely, resulting in a dynamically changing topology.
 Existing distance-vector and link-state-based routing protocols
are unable to catch up with such frequent link changes in ad hoc wireless
networks, resulting in poor route convergence and very low
communication throughput. Hence, new routing protocols are needed70

71. Routing protocols
Routing protocols
 Purpose is to dynamically communicate information about all
network paths used to reach a destination and to select the from
those paths, the best path to reach a destination network.
Types of routing protocol
 Distance –vector Routing Protocol
 Distance vector protocols use a distance calculation (distance metric) plus
an outgoing network interface (a vector) to choose the best path to a
destination network.
 The network protocol (IPX, SPX, IP,Appletalk, DECnet etc.) will forward
data using the best paths selected
 Well Supported Protocols such as RIP have been around a long time and
most, if not all devices that perform routing will understand RIP.
71

72.  Link state based
 Selects the best routing path by calculating the state of each link
in a path and finding the path that has the lowest total metric to
reach the destination.
 Link State protocols track the status and connection type of
each link and produces a calculated metric based on these and
other factors, including some set by the network administrator.
 Link state protocols know whether a link is up or down and
how fast it is and calculates a cost to 'get there'.
 Link State protocols will take a path which has more hops, but
that uses a faster medium over a path using a slower medium
with fewer hops.
72

73. Difference
 If all routers were running a DistanceVector protocol, the path or
'route' chosen would be from A B directly over the ISDN serial link,
even though that link is about 10 times slower than the indirect route
from A C D B.
 A Link State protocol would choose the A C D B path because it's
using a faster medium (100 Mb ethernet).
 In this example, it would be better to run a Link State routing protocol,
but if all the links in the network are the same speed, then a Distance
Vector protocol is better.
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74. 74
Routing (2)
 Requirements
 Minimum route acquisition delay
 Quick route reconfiguration
 Loop-free routing
 Distributed routing approach
 Minimum control overhead
 Scalability
 QoS provisioning
 Support for time-sensitive traffic
 Security and privacy

75. 4. Multicasting
 Multiparty communcations are enabled through the
presence of multicast routing protocols.
 The multicast backbone (MBone) comprises an
interconnection of multicast routers that are capable of
tunnelling multicast packets through non-multicast routers.
 Some multicast protocols use a broadcast-and-prune
approach to build a multicast tree rooted at the
source.Others use core nodes where the multicast tree
originates.
 All such methods rely on the fact that routers are
static, and once the multicast tree is formed, tree nodes will
not move. However, this is not the case in ad hoc wireless
networks.
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76. 76
Multicasting
 Robusteness
 recover and reconfigure quickly from potential mobility-
induced link breaks
 Efficiency
 Min control overhead
 QoS support
 Efficient group management
 Scalability
 security

77. 5. Energy Efficiency
 Mobile devices today are mostly operated by batteries. Battery
technology is still lagging behind microprocessor technology.
 The lifetime of an Li-ion battery today is only 2-3 hours. Such a
limitation in the operating hours of a device implies the need for
power conservation.
 For ad hoc mobile networks, mobile devices must perform both the
role of an end system (where the user interacts and where user
applications are executed) and that of an intermediate system
(packet forwarding).
 Hence, forwarding packets on the behalf of others will consume
power, and this can be quite significant for nodes in an ad hoc
wireless network.
77

78. 78
Energy Management
 Tx power mgmt
 MAC: sleep mode
 Routing: consider battery life time: load balancing
 Transport: reduce ReTx
 App
 Battery energy mgmt
 Extend battery life by taking adv of chemical properties,
discharge patterns, and by the selection of a battery from a set
of batteries
 Processor power mgmt
 Device power mgmt

79. 6. TCP Performance
 TCP is an end-to-end protocol designed to provide flow and
congestion control in a network. TCP is a connection-
oriented protocol; hence, there is a connection
establishment phase prior to data transmission.The
connection is removed when data transmission is completed.
 TCP (Transmission Control Protocol) assumes that nodes in
the route are static, and only performs flow and
congestion activities at the SRC and DEST nodes.
79

80.  TCP relies on measuring the round-trip time (RTT) and packet loss
to conclude if congestion has occurred in the network.
 In telecommunications, the round-trip delay time
(RTD) or round-trip time (RTT) is the length of time it takes for
a signal to be sent plus the length of time it takes for an
acknowledgment of that signal to be received.This time delay
therefore consists of the transmission times between the two points of
a signal.
 TCP is unable to distinguish the presence of mobility and
network congestion.
 Mobility by nodes in a connection can result in packet loss and long
RTT.
 Enhancements needed to ensure that the transport protocol performs
properly without affecting the end-to-end communication throughput.80

81. 7. Service Location, Provision, and
Access
 Ad hoc networks comprise heterogeneous devices and
machines and not every one is capable of being a server.
 The concept of a client initiating task requests to a server for
execution and awaiting results to be returned may not be
attractive due to limitations in bandwidth and power.
 Concept of remote programming as used in mobile agents is
more applicable since this can reduce the interactions
exchanged between the client and server over the wireless
media.
 Also, how can a mobile device access a remote service in an
ad hoc network? How can a device that is well-equipped
advertise its desire to provide services to the rest of the
members in the network?All these issues demand research.
81

82. 8. Security & Privacy
 Ad hoc networks are intranets and remain as intranets unless
connected to Internet.
 Such confined communications have already isolated
attackers who are not local in the area.
 Through neighbor identity authenication, a user can know if
neighboring users are friendly or hostile.
 Information sent in an ad hoc route can be protected in some
way but since multiple nodes are involved, the relaying of
packets has to be authenicated by recognizing the originator
of the paket and the flow ID or label.
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83. 83
Security
 DoS attack
 Resource consumption
 Energy depletion
 Buffer overflow
 Host impersonation
 Information disclosure
 Interference

84. 84
9. Deployment Consideration (1)
 Adv. in ad hoc net
 Low cont of deployment
 Incremental deplyment
 Short deplyment time
 Reconfigurablity
 Scenario of deployment
 Military deployment: data-centric or user-centric
 Emergency operation deployment: hend-held, voice/data,
< 100 nodes
 Commercial wide-area deployment: e.g.WMN
 Home network deplyment

85. 85
Deployment Consideration (2)
 Required longevity of network
 Area of coverage
 Service availability: redundancy
 Operational integration with other infrastructure
 Satellite network, UAV(unmanned aerial vehicles), GPS
 Cellular network
 Choice of protocols
 TDMA or CSMA-based MAC?
 Geographical routing (using GPS)
 Power-saving routing ?
 TCP extension ?