Ad-hoc Networks Επίκ. Καθηγητής Συμεών Παπαβασιλείου Εθνικό Μετσόβιο Πολυτεχνείο Τμήμα Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών Τομέας Επικοινωνιών, Ηλεκτρονικής & Συστημάτων Πληροφορικής (papavass@mail.ntua.gr Τηλ: 210 772-2550 Γραφείο: 2.2.10 Κτίριο Ηλεκτρολόγων) 1
ΘΕΜΑΤΟΛΟΓΙΑ Χαρακτηριστικά Αυτοοργανούμενων Ad-hoc Δικτύων Αρχιτεκτονική Δικτύων Μεταβλητής Τοπολογίας Δίκτυα Αισθητήρων και Εφαρμογές Οργάνωση και αυτοοργάνωση Μοντελοποίηση Δρομολόγηση Θέματα ευρυεκπομπής/πολυεκπομπής Διαχείριση ενέργειας Απόδοση και παροχή ποιότητας υπηρεσιών Μοντέλα κινητικότητας (ατομικά και ομαδικά) Εφαρμογές 2
Overview of Wireless Networks: A Taxonomy Single hop networks - Cellular networks - Satellite networks - One hop wireless LAN Multi-hop self-organized networks - Peer to peer networks - Battle field, conference - Ad hoc networks - Sensor networks 3
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) WIRE- WIRE- LINE LINE NETWORK 4
Mobile Ad hoc Networks Characteristics - Absence of a fixed infrastructure (Infrastructure-less) - All nodes are potentially mobile - Network topology is dynamic - All nodes could act as individual routers - All nodes could be functionally equal Examples - Tactical and emergency solutions (i.e. emergency rescue) - Operated as robust inexpensive networks - Augmenting the Cellular Network and Support the solution of Hot Spot Communication Problem - Commercial applications involving cooperative mobile data exchange, conferencing applications, classroom - Low power sensor based network 5
Mobile Ad hoc Networks Objectives - Maintain connectivity between mobile devices - Provide congestion-free routing for multimedia traffic - Support scalability - Minimize memory, bandwidth and energy consumption 6
Mobile Ad hoc Networks (MANET) transmission range 7
Mobile Ad hoc Networks (MANET) 8
How to build an ad hoc network Node association, power control Flat vs. Clustering Self-organizing: neighbor discovery and management In this example, all nodes are within coverage of the four black nodes Same is true for the four red nodes We can let the red and black sets of nodes take turns Lifetime is doubled Very simple idea More details are needed 9
Hybrid Environments Use infrastructure when convenient Use ad hoc connectivity when necessary or superior BS1 infrastructure BS2 A Ad hoc connectivity E Z X 10 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 11
Variations May co-exist (and collaborate) with an infrastructure-based network Traffic characteristics o Bit rate o Timeliness constraints o Reliability requirements Mobility Patterns and Mobility Characteristics o Speed / Direction / Pattern of movement o Individual vs. group mobility patterns 12
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 13
Sensor Networks Application Areas 1. Military: Monitoring equipment Battlefield surveillance and damage assessment biological, chemical attack detection 2. Environmental: Forest fire / flood detection 3. Health: Tracking and monitoring doctors and patients inside a hospital Drug administration in hospitals 14
Sensor Networks Application Areas 4. Home: Smart environment 5. Other Commercial Applications: Environmental control in office buildings Managing inventory control Vehicle tracking and detection 15