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Pranali_d-AWN.pptx
- 1. Ad Hoc Wireless Network Prof. Pranali Deshmukh Department of Information technology International Institute of Information Technology, I²IT www.isquareit.edu.in
- 2. 2 Introduction • Ad Hoc Network is a multi-hop relaying network • ALOHAnet developed in 1970 • Ethernet developed in 1980 • In 1994, Bluetooth proposed by Ericsson to develop a short-range, low-power, low- complexity, and inexpensive radio inteface • WLAN 802.11 spec. is proposed in 1997
- 3. Cellular and Ad Hoc Wireless Networks • Cellular Wireless Networks: infrastructure dependent network • Ad Hoc Networks: multi-hop radio relaying and without support of infrastructure – Wireless Mesh Networks – Wireless Sensor Networks 3
- 4. Cellular Wireless Networks Hybrid Wireless Networks Wireless Mesh Networks Wireless Sensor Networks 4 Infrastructure Dependent (Single-Hop Wireless Networks) Ad Hoc Wireless Networks (Multi-Hop Wireless Networks) Figure Cellular and ad hoc wireless networks.
- 5. B A C D E Switching Center + Gateway Path from C to E Base Station Mobile Node Figure A cellular networks. 5 5
- 6. B A C F D E Path from C to E Mobile Node Wireless Link Figure. An ad hoc wireless networks 6 6
- 7. Differences between cellular networks and ad hoc wireless networks Cellular Networks Ad Hoc Wireless Networks Fixed infrastructure-based Infrastructure-less Single-hop wireless links Multi-hop wireless links Guaranteed bandwidth (designed for voice traffic) Shared radio channel (more suitable for best-effort data traffic) Centralized routing Distributed routing Circuit-switched (evolving toward packet switching) Packet-switched (evolving toward emulation of circuit switching) Seamless connectivity (low call drops during handoffs) Frequency path break due to mobility High cost and time of deployment Quick and cost-effective deployment Reuse of frequency spectrum through geographical channel reuse Dynamic frequency reuse based on carrier sense mechanism 7 7
- 8. Differences between cellular networks and ad hoc wireless networks (cont.) Easier to achieve time synchronization Time synchronization is difficult and consumes bandwidth Easier to employ bandwidth reservation Bandwidth reservation requires complex medium access control protocols Application domains include mainly civilian and commercial sector Application domains include battlefields, emergency search and rescue operation, and collaborative computing High cost of network maintenance (backup power source, staffing, etc.) Self-organization and maintenance properties are built into the network Mobile hosts are of relatively low complexity Mobile hosts require more intelligence (should have a transceiver as well as routing/switching capacity) Major goals of routing and call admission are to maximize the call acceptance ratio and minimize the call drop ratio Man aim of routing is to find paths with minimum overhead and also quick reconfiguration of broken paths Widely deployed and currently in the third generation Several issues are to be addressed for successful commercial deployment even though widespread use exists in defense 8 8
- 9. 9 Applications of Ad Hoc Wireless Networks • Military Applications – Establishing communication among a group of soldiers for tactical operations – Coordination of military object moving at high speeds such as fleets of airplanes or ships – Requirements: reliability, efficiency, secure communication, and multicasting routing, • Collaborative and Distributed Computing – Conference, distributed files sharing • Emergency Operations – Search, rescue, crowd control, and commando operations – Support real-time and fault-tolerant communication paths
- 10. Wireless Mesh Networks • An alternate communication infrastructure for mobile or fixed nodes/users • Provides many alternate paths for a data transfer session between a source and destination • Advantages of Wireless Mesh Networks – High data rate, quick and low cost of deployment, enhanced services, high scalability, easy extendability, high availability, and low cost per bit 10
- 11. A house with rooftop transceiver 11 Transmission range Wired link to the Internet Wireless link Figure 5.4. Wireless mesh networks operating in a residential zone Wired Network Gateway node
- 12. Internet Wired link to the Internet 12 Multi-hop radio relay link Lamp Radio relay node Figure 5.5 Wireless mesh network covering a highway Coverage area
- 13. 13 Wireless Sensor Networks • A collection of a large number of sensor nodes that are deployed in a particular region • Applications: – military, health care, home security, and environmental monitoring • Differences with the ad hoc wireless networks: – Mobility of nodes, size of network, density of deployment, power constraints, data/information fusion, traffic distribution
- 14. 14 Hybrid Wireless Networks • HWN such as Multi-hop cellular networks and integrated cellular ad hoc relay networks – The base station maintains the information about the topology of the network for efficient routing – The capacity of a cellular network can be increased if the network incorporates the properties of multi-hop relaying along with the support of existing fixed infrastructure • Advantages: – Higher capacity than cellular networks due to better channel reuse – Increased flexibility and reliability in routing – Better coverage and connectivity in holes
- 15. Switching Center + Gateway B A C D E MCN communication 15 Base Station Mobile Node Figure 5.6. MCN architecture.
- 16. 16 Issues in Ad Hoc Wireless Networks • Medium access scheme • Routing, Multicasting, TPC protocol • Pricing scheme, QoS, Self-organization • Security, Energy management • Addressing and service discovery • Deployment considerations
- 17. Medium Access Scheme • Distributed operation – fully distributed involving minimum control overhead • Synchronization – Mandatory for TDMA-based systems • Hidden terminals – Can significantly reduce the throughput of a MAC protocol • Exposed terminals – To improve the efficiency of the MAC protocol, the exposed nodes should be allowed to transmit in a controlled fashion without causing collision to the on- going data transfer • Access delay 17
- 18. The Major Issues of MAC Scheme • Throughput and access delay – To minimize the occurrence of collision, maximize channel utilization, and minimize controloverhead • Fairness – Equal share or weighted share of the bandwidth to all competing nodes • Real-time traffic support • Resource reservation – Such as BW, buffer space, and processing power • Capability for power control • Adaptive rate control • Use of directional antennas 18
- 19. 19 The Major Challenge of Routing Protocol • Mobility result in frequent path break, packet collision, and difficulty in resource reservation • Bandwidth constraint: BW is shared by every node • Error-prone and share channel: high bit error rate • Location-dependent contention: distributing the network load uniformly across the network • Other resource constraint: computing power, battery power, and buffer storage
- 20. 20 The Major Requirement of Routing Protocol • Minimum route acquisition delay • Quick route reconfiguration: to handle path breaks • Loop-free routing • Distributed routing approach • Minimum control overhead • Scalability • Provisioning of QoS: • supporting differentiated classes of services • Support for time-sensitive traffic • Security and privacy
- 21. The Major Issues in Multicast Routing Protocols • Robustness – recover and reconfigure quickly from link breaks • Efficiency – minimum number of transmissions to deliver a data packet to all the group members • Minimal Control overhead • QoS support • Efficient group management • Scalability • Security 21
- 22. Transport Layer Protocols • Objectives:setting up and maintaining – End-to-end connections, reliable end-to-end data delivery, flow control, and congestion control • Major performance degradation: – Frequent path breaks, presence of old routing information, high channel error rate, and frequent network partitions 22
- 23. 23 Quality of Service Provisioning • QoS often requires negotiation between the host and the network, resource reservation schemes, priority scheduling and call admission control • QoS in Ad hoc wireless networks can be on a per flow, per link, or per node • Qos Parameters: different applications have different requirements – Multimedia: bandwidth and delay are the key parameters – Military: BW, delay, security and reliability – Emergency search –and-rescue: availability is the key parameters, multiple link disjoint paths – WSN: battery life, minimum energy consumption
- 24. 24 Quality of Service Provisioning • QoS-aware routing: – To have the routing use QoS parameters for finding a path – The parameters are network through put, packet delivery ratio, reliability, delay, delay jitter, packet lost rate, bit error rate, and path loss • QoS framework: – A frame work for QoS is a complete system that attempts to provide the promised service – The QoS modules such as routing protocol, signaling protocol, and resource management should react promptly according to changes in the network state
- 25. 25 Self-Organization • An important property that an ad hoc wireless network should exhibit is organizing and maintaining the network by itself • Major activities: neighbor discovery, topology organization, and topology reorganization • Ad hoc wireless networks should be able to perform self-organization quickly and efficiently
- 26. 26 Security • The attack against ad hoc wireless networks are classified into two types: passive and active attacks • Passive attack: malicious nodes to observe the nature of activities and to obtain information in the network without disrupting the operation • Active attack: disrupt the operation of the network – Internal attack: nodes belong to the same network – External attack: nodes outside the network
- 27. References “Ad Hoc Wireless Networks Architectures and Protocols” By Shiva Ram Murthi.
- 28. Prof Pranali Deshmukh Information Technology Department I2TT,Hinjewadi 2 8