Overview of Wireless Networks Cellular Mobile Ad hoc

Overview of Wireless Networks: Cellular Mobile Ad hoc Sensor

Cellular Architecture - Infrastructure-based networks - All units are fixed in location except mobile units - BS and MSC are connected via wirelines - Communication between BS and mobile unit is wireless Cell Base Station (BS) Mobile unit Wireless Links Wired Links Mobile Switching Center (MSC) WIRELINE NETWOR K

Why Mobile Ad hoc Networks? Ø Characteristics - Infrastructure-less - All nodes are potentially mobile - Network topology is dynamic - All nodes act as individual routers Ø Examples - Disaster recovery situations - Battle field communications - Law enforcement operations - Civilian applications Ø Objectives - Maintain connectivity between mobile devices - Provide congestion-free routing for multimedia traffic - Support scalability - Minimize memory, bandwidth and energy consumption

Mobile Ad hoc Networks (MANET) transmission range

Hybrid Environments Use infrastructure when convenient Use ad hoc connectivity when necessary or superior BS 1 infrastructure A BS 2 E Z Ad hoc connectivity X © 2001 Nitin Vaidya

Variations • Symmetric environments o Nodes having identical capabilities and responsibilities • Asymmetric capabilities o Transmission ranges o Processing power o Battery lifetime o Mobility speed • Asymmetric responsibilities o Some nodes may forward route packages o Leaders vs. ordinary nodes • May co-exist (and collaborate) with an infrastructure-based network

Variations • Traffic characteristics o Bit rate o Timeliness constraints o Reliability requirements • Mobility Patterns o Students on campus o Passengers on airports o Taxi cabs • Mobility Characteristics o Speed / Direction / Pattern of movement

Sensor Networks Wireless sensor networks consists of group of sensor nodes to perform distributed sensing task using wireless medium. Characteristics - low-cost, low-power, lightweight - densely deployed - prone to failures - two ways of deployment: randomly, pre-determined or engineered Objectives - Monitor activities - Gather and fuse information - Communicate with global data processing unit

Sensor Networks Application Areas [Akyildiz+ 2002] 1. Military: Ø Ø Ø Monitoring equipment and ammunition Battlefield surveillance and damage assessment Nuclear, biological, chemical attack detection and reconnaissance 2. Environmental: Ø Forest fire / flood detection 3. Health: Ø Ø Tracking and monitoring doctors and patients inside a hospital Drug administration in hospitals

Sensor Networks Application Areas [Akyildiz+ 2002] 4. Home: Ø Ø Home automation Smart environment 5. Other Commercial Applications: Ø Ø Environmental control in office buildings Detecting and monitoring car thefts Managing inventory control Vehicle tracking and detection

Sensor Networks vs. Traditional Wireless Networks (Cellular, MANET) – Higher number of sensor nodes (several orders of magnitude) – Dense deployment – Prone to failures – Limited in power, computation and memory – May not have global identification (ID) due to high overhead and the total number of sensors – Optimization on the energy consumption vs. Qo. S and high bandwidth constraints – Stationary vs. mobile – Data flow: unidirectional vs. bi-directional – Date rates

Sensor Networks Preliminaries – For large scale environment monitoring applications, dense sensor networks are mainly used – Sensing capabilities should be distributed and coordinated amongst the sensor nodes – Algorithms deployed should be localized since transmissions between large distances are expensive and lowers networks life time – These networks should be self-configuring, scalable, redundant and robust during topology changes

Current Challenges 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)

Research Problems in Ad hoc and Sensor Networks Ø Clustering – Partitioning of the network – Identification of vital nodes (clusterheads) Ø Routing – – – Discovering routes from source to destination Maintaining the routes Rediscovery and repair of routes Ø Topology management – Maintain the links – Minimize the changes in underlying graph Ø Security

Research Problems in Ad hoc and Sensor Networks Ø Medium Access Control Protocols Ø Sensor data management Ø Power conservation/energy consumption Ø Data fusion and dissemination of sensor data Ø New applications for ad hoc and sensor networks

References [Akyildiz+ 2002] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, A Survey on Sensor Networks, IEEE Communications Magazine, Vol. 40, No. 8, pp. 102 -114, August 2002.