Wireless and Mobile Networks

Transcription

1 Monash University Department of Electrical and Computer Systems Engineering Wireless and Mobile Networks Present and Future Y. Ahmet Şekercioğlu August 2007wireless-nets.tex,v1.5 Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 1

2 Outline Introduction and Background Wireless Links, Characteristics Ad Hoc Networks Wireless Sensor Networks Cellular Internet Access Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 2

3 Introduction and Background Future: From the User s Perspective Converged Services Single and universal phone number for every kind of communication - e.g. sekerci.net Seamless mobility - communicate wherever and whenever one wants Freedom to choose cheapest communication medium/service easily Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 3

4 Introduction and Background Future: From the Technologist s Perspective Converged Infrastructure Fusion of hardware architectures - fixed+mobile+wireless+cellular+satellite Fusion of software architectures - around IPv6 Widespread coverage without requiring expensive network management Always-on connections for mobile devices at the edge of a fixed core network Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 4

5 Introduction and Background Wireless Links, Characteristics Ad Hoc Networks Wireless Sensor Networks Cellular Internet Access Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 5

6 Elements of a Wireless Network (note the meaningless diagram) Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 6

7 A Taxonomy of (From Kurose-Ross) Infrastructure Mode No Infrastructure Single Hop host connects to base station (WiFi, WiMAX, cellular) which connects to larger Internet no base station, no connection to larger Internet (Bluetooth, ad hoc networks) Multiple Hops host may have to relay through several wireless nodes to connect to larger Internet: mesh networks no base station, no connection to larger Internet. May have to relay to reach other a given wireless node: MANET, VANET Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 7

8 Wireless Links, Characteristics Wireless Link Characteristics (I) (From Kurose-Ross) Differences from wired links... decreased signal strength: radio signal attenuates as it propagates through matter (path loss) interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well multipath propagation: radio signal reflects off objects ground, arriving at the destination at slightly different times...make communication across (even a point to point) wireless link much more difficult Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 8

9 Wireless Links, Characteristics Wireless Link Characteristics (II) (From Kurose-Ross) signal-to-noise ratio (SNR): larger the SNR - easier to extract signal from noise SNR versus BER tradeoffs: given physical layer: increase power increase SNR decrease BER given SNR: choose physical layer that meets BER requirement, giving highest throughput SNR may change with mobility: dynamically adapt physical layer (modulation technique, rate) Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 9

10 Wireless Sensor Networks WSNs are wireless networks consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 10

11 Cellular Internet Access Introduction and Background Wireless Links, Characteristics Ad Hoc Networks Wireless Sensor Networks Cellular Internet Access Y. Ahmet Şekercioğlu: Wireless and Mobile Networks 11