UNIT - VII

MOBILE AD-HOC&

WIRELESS SENSOR NETWORKS

INTRODUCTION: • A fixed infrastructure network is one, in

which incorporated access points, base stations, and gate ways.

• The systems which are remotely located are networked using switches, hubs and routes, location of these are fixed.

• A mobile device moved in the vicinity (connectivity range) of an access point, that enables itself to connect to the access point and access the network. Cellular network is example for fixed infrastructure network.

• An ad-hoc network is one, in which locations of switches, hubs, and routers can also be mobile.

• At an instant of time the availability of routers can be increased or decreased and routing paths may also changed.

• In ad-hoc networks, the mobile devices can work as access points or routers and routes between them are changed from time to time, it depends on the presence, locations and capacity of number of mobile devices in the vicinity.

Fixed Infrastructure Architecture:• In fixed infrastructure network, each

mobile device connects to an access-point, base station, or gateway using a switch, hub, or router.

• A switch is used to provides connectivity between the two or more mobile devices, and a hub functions as a central switching exchange.

• A router provide two or more paths to route a message or packet so all the available paths can be used at an instant.

• The access point function as the node of the network.

• A mobile device or sensor has to acquire an access-point or node of the fixed infrastructure network before being able to connect to another, then only the messages can be routed.

• For example, the connectivity between two or more cellular phones are established only through the GSM base stations in which it has three sub systems. Each mobile first connects to the RSS of GSM.

• The following diagram shows the fixed infrastructure network architecture;

• The following are some drawbacks with fixed infrastructure networks;

a) Disconnection from the network - thusunable to communicate through the

network when a wireless sensor or mobile device moves out of the range of access point, base station, or gateway having the switch or router, even though there may be another wireless device in the vicinity connected to the network.

b) Network not usable in operations like disaster relief.

MANET Infrastructure Architecture:• MANET is a self configured wireless ad-

hoc network of mobile nodes.• Each node act as a router or a switch

connected by the wireless connection.• The combination of all these connections

may form an arbitrary topology and the network either function independently or connect to internet.

• An important characteristic of ad-hoc network architecture is, its organization can change due to movement of a devices.

•A MANET organization depends upon the location of the nodes, their connectivity, their service discovery capability, and their ability to search and route messages using nearest node or nearby nodes.• so in MANET The routes available to the mobile devices or wireless sensors can thuschange at any time depend on presence and locations of other wireless devices.• The following diagram shows MANET architecture;

• In the above diagram the ad-hoc network is formed by the nodes A, B, C, D, E, F and G.

• The diagram shows that each mobile device functions as a node with a switch or router.

• The following is an example describes how MANET are established and organize them selves.

1)Let us consider the above diagram, suppose the nodes D and E move away from each other then two new ad-hoc networks will be formed one with A, C and D and other with A, G, F and E. But all the devices in connection to each other through common node A.

2) Let consider a Bluetooth enabled mobile device, a Bluetooth enabled computer and the computer has Wi-Fi internet connection. Let us assume the computer also connects through Jini client with printer which is at office. now the user by carrying the mobile device moves from office to home, when he reaches to home an ad-hoc network is established between mobile device, computer at home and printer at office.

MANET Properties & Spectrum Applications:• MANET provides seamless way of

interaction and everywhere mobile computing environment.

• Seamless connectivity maintained between the devices when they move with the nearby wireless nodes, sensor nodes, and embedded devices in

Automobiles.• Generally each MANET node have a

frequency spectrum that is smaller than the spectrum frequency in fixed infrastructure network.

• Another version of MANET is VANET- Vehicular ad-hoc network which is used for communication among vehicles and between vehicles and road side equipment.

• The following are some properties of MANET;

• One of the important property of MANET is neighbour discovery, it enables data reception and transmission using discovered node.

• Data routing is another property of MANET that is data routed from source node to a neighbouring node.

1) 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.

2) Direct communication through nearby node and neighbour discovery:

• A MANET node has a ability to discover a neighbouring node and service.

• A node discovers the service of the neighbouring node using service discover protocol then it is able to communicate with remote node.

3) Peer-to-Peer connectivity: MANET nodes have peer-to-peer connectivity among themselves.

4) Computations decentralizations: We know that each MANET node has an independent computational, switching and communication capabilities.

5) Limited wireless connectivity range: In MANETs a node should move in the

Coverage area of at least one near by node, else the node should be provided with access point of wired communication.

• we conclude that the wireless connectivity range in MANETs only nearest node connectivity.

6) Weak connectivity and remote server latency: Unreliable links to base station or gateway and failure of an intermediate nodes may cause in greater latency in communicating with the remote server.

7) Resource constraints: Limited bandwidth available between the nodes is the major constraint in MANETs, and also limited power capability needs may perform energy efficient operations only.

8) No access point requirement: There is no need of access points in MANETs, only selected access points are provided for connection to other networks or MANETs

9) Requirement to solve hidden/exposed terminal problem: The MANET organization should require a mechanism to solve hidden and exposed terminal problem.

10) Diversity in nodes: The MANET support various kinds of nodes such as iPods, handheld computers, smart phones, PCs, Smart labels, Smart sensors, and automobile embedded systems.

11) Protocol diversity: MANET nodes can use different protocols, such as IrDA, Bluetooth, ZigBee, 802.11, GSM, and TCP/IP.

12) Data caching, Saving and Aggregation: The MANET node can perform data caching, saving it can also perform data aggregation.

Spectrum: We know that a huge number of devices are connected to the access point based fixed infrastructure network. The bandwidth required to service all these devices within the vicinity is too large.

• Suppose N devices are connected to the access point by using FDMA, then the required bandwidth for these devices is:

N X fbw0

where fbw0 is bandwidth allotted for one device.

• Suppose it is a full duplex transmission then the need of bandwidth is doubled, i.e 2 X N X fbw0

• But we know that in fixed infrastructure network the bandwidth requirement can reduced by using some other techniques like TDMA and SDMA.

• In each MANET node has much smaller frequency spectrum requirements than that for a node in a fixed infrastructure network.

• Here a node itself a router for all the packets coming from or going out to the other nodes.

• In MANET the nodes are themselves mobile so the bandwidth available to any node at any instant is not constant.

• The MANETs allow reuse of spectrum and each wireless link provide a limited bandwidth.

• In MANET the communication is carried in multi hop fashion, so each node has low and adaptable transmission power which is having signal strength just sufficient to carry the data up to next hop.

• The hops can occur in MANET simultaneously using same frequency band.

• It mean that there is a spatial reuse of bandwidth, which depending on the surrounding environment.

• Let us consider an example

• In the above diagram node D at a instant get incoming packets from E, F, G and A and can send packets C and A vice versa.

• When node D transmit data to G it happen in three hops D-E, E-F and F-G

• In MANET which node need higher bandwidth is depends number of next hop neighbours from that node.

• The bandwidth requirement can also reduced in MANET by scheduling the each node path and hop direction at different instants.

MANET Applications: The MANET supports many applications the following are few applications;

a)Content distribution & content synchronization: Let us consider in an enterprise, there are a number of Bluetooth-enabled mobile handheld devices, PCs, laptops, and Wi-Fi access points, the MANET used for content-distribution, by following PIM, information dissemination,

information fusion, and file sharing techniques.

b) Multicast network: MANET supports multicasting by organizing the nodes in multicast tree topology. Here we use CGSR protocol for multicasting.

c) Mesh network: Mesh-based mobile networks offer highly dynamic autonomous topology segments for the robust IP-compliant data services. The mesh is inexpensive to infrastructure-based cellular mobile networks.

• Mesh network is build by using PUMA (Protocol for unified multicasting through announcements) protocol. Mesh connects MANET nodes each other.

• We know that the multicast tree is different from mesh. Multicast tree provides a single path between the sender and receiver, but mesh supports multiple paths between sender and receiver.

• But we know that the error rate is high on wireless links so PUMA can send the packets from sender to receiver through various paths.

d) Image acquisition, processing and distribution using MANET: Let us consider number of imaging devices forming a MANET.

•low cost digital still camera with a wireless network interface, Wireless Webcam, mobile device connected to a digital still camera, mobile phones, and pocket PCs equipped with an image acquisition sensor.•The following are some applications where MANETs to apply;1.Remote view finder by security personal in office.2.Remote processing on a computer for a video from wireless webcam or from other devices.3.Image file transfer

4) Messaging and data transmission to remote device using 802.11b.

5) Remote controlling.e) IPv6 integration and wireless sensor

networks: IPv6 is a new generation internet protocol used for internet radio and real time video over the internet.

• Now we integrate IPv6 with MANET and wireless sensor networks. This integration leads to pervasive computing and other innovative applications.

Security in Ad-hoc Networks: security is important for maintaining

privacy in mobile ad-hoc networks, the following are some of the security problems in wireless computing systems;

1)Confidentiality: Only intended user only able to read the data. Encryption of the data before the transmission and decryption at the user end is employed for confidentiality.

2)Integrity: Here data integrity as well as the system integrity to be maintained to avoid manipulated messages and messages to wrong nodes.

3) Pre-Keying: A key should be exchanged before the transmission of the data between the sender and receiver for decryption of the data at receiver side. The key exchanging is through wireless link, it increases the risk of key tapping.

4) Availability: There may be a denial of service attack, a source may block the availability of data at the user end due to intermediate router misdirection.

5) Non-Repudiation: A sender is unable to refuse send a message or information.

6) Resource constraint: Resource constraint of mobile systems have several points;

a) The service provider (server) runs slower than a node.

b) Less memory availability.c) Limited battery life.d) Certain kinds of attacks.7) Power of detection: A mobile device may

not detect the signals therefore unable to get the data by jamming the signals.

8) Interception: Some times the signals may intercepted.

9) Replay: Some time the attacker replay the same sequence of messages to the server by hacking the authentication requests.

10) Stealing of subscriber service: Hijacking of user name and password by an attacker, results getting service of another client.

11) Mobility risks: Frequent change in locations may lead to changing of routing path frequently.

12) Spoofing: A node can imitate the address of another node in ad-hoc network. Suppose spoofing at common node leads to

chocking of all routes.13) Reconfiguration: Changing of network

parameters due to configuration attacks may cause configure the network in frequent intervals of time.

14) eavesdropping: Certain times unsolicited messages from third party during a talk between two nodes.

15) Traffic analysis: By extracting the network traffic analysis some security problems may occur.

Wireless Sensor Networks:• Wireless sensor networks are a kind of

MANETs functions with smart sensors having computational, communication and networking capabilities.

• A sensor is consider as a smart one, if it consists of computational and logical capabilities.

• A wireless sensor is one which have communication abilities by using a radio frequency transceiver.

• The RF transceiver is able to receive the data from nearby nodes and route these packets to the next hop neighbouring nodes.

• The RF transmission and reception can use Wi-Fi, Access-point, or ZigBee protocols.

• The following diagram shows wireless sensor networks,

•

• The following are elements of wireless sensor network;

1)Sensor.2)An RF transceiver for communication.3)A micro controller (CPU, ADC, Memory)4)Energy source or power supply – A

charge pump in the sensor can catch the charge from radiations and supply the power.

5)Alternative energy – An energy harvesting module can used to catch the solar radiations and store the energy.

• The following diagram shows wireless sensor architecture;

• The wireless sensor node is able to disseminate the data to the neighbouring nodes in the network, central computer or to a controller.

• The wireless node have sophisticated hardware and software, each node has a sensor, which senesces light, temperature, physical, chemical and biological data.

• Software once embedded into the sensor node is for lifetime should be robust, fault tolerant, and should provide maximum features.

•Software should have features of security, self-healing, and self configuration.•Finally we know that the sensors has computational, communication and networking capabilities, but are constrained due to size, energy availability, and memory. So the sensors operated at limited computational speed and bandwidth.

Data dissemination in sensor networks: Data dissemination in wireless sensor networks is carried out in three ways;

1) Aggregation: It refers to the process of joining present and previously received data packets after removing the duplicate data.

2) Compacting: It is the process of making information short without changing meaning and context.

3) Fusion: It mean formatting the information received in parts through various packets and several types of data, in case when individual records not required and/or not retrievable later.

Wireless Sensor Network Applications:1)Street lights with local as well as remote

central control.2)Industrial plant wireless sensor networks:

Industrial plants use large number of sensors in instruments and Controllers they proves powerful for industrial plants.

3)Pervasive computing networks: Mobile pervasive computing means a set of computing devices, sensors, or systems or a network having the characteristics of transparency, application-aware adaptation, and environment sensing.4) Traffic monitoring using traffic density wireless sensor networks: Traffic can be monitored at different points in a city and traffic density information can be aggregated at central server. The server send the information in the form of SMS to drivers to select roads with least hurdles.

5) Medical applications: Patients can be monitored by sensors attached to them.

6) Military applications: The physical characteristics of a person can be sensed by a wireless sensor networks deployed in borders. This monitors the army troops and machines moments.

7) Smart labels and RFID applications: These are used world wide for monitoring movement of goods and supply chain management system.

8)Environmental applications: Environmental parameters, such as temperature, pressure, light, rainfall, and seismic activities are sensed and communicated over the wireless links.

9) Home automation: Various home automation applications like security may possible with sensor networks.

UNIT-VII

THE END