Mobile Networks Prof. Jean-Pierre Hubaux EPFL The Playground of - PDF document

1 Mobile Networks Prof. Jean-Pierre Hubaux EPFL

The Playground of Communication Networks Control Information server Cellular network server Information MSC BS server MSC Control server Control IP network server PSTN Router Switch WLAN MSC: Mobile services Switching Center Station BS: Base Station WLAN: Wireless LAN Gateway PSTN: Public Switched Telephone NW 2

Wireless communication and mobility g Aspects of mobility: i user mobility : users communicate “anytime, anywhere, with anyone” i device portability : devices can be connected anytime, anywhere to the network g Wireless vs. mobile Examples � � stationary computer (desktop) � � laptop connected to an Ethernet network � � desktops in historic buildings � � Personal Digital Assistant (PDA) g The demand for mobile communication creates the need for integration of wireless networks or mobility mechanisms into existing fixed networks: i telephone network � cellular telephony (e.g., GSM) i local area networks � Wireless LANs (e.g.,IEEE 802.11) i Internet � Mobile IP

Wireless systems: development over the last 20 years cordless satellite wireless cellular phones phones networks LAN, wireless 1980: 1981: CT0 PAN NMT 450 1982: 1984: Inmarsat-A 1983: CT1 AMPS 1986: NMT 900 1987: 1988: CT1+ Inmarsat-C 1991: 1991: 1989: CDMA 199x: D-AMPS CT 2 (USA: IS-95) proprietary 1991: 1992: 1992: DECT Inmarsat-B GSM 1995/96/97: Inmarsat-M 1993: IEEE 802.11, PDC HIPERLAN 1994: DCS 1800 1998: Iridium analog 2001 - ?: IEEE 802.15 2002 - ?: digital Bluetooth UMTS/IMT-2000 CDMA-2000 (USA) NMT: Nordic Mobile Telephone DECT: Digital Enhanced Cordless Telecom. AMPS: Advanced Mobile Phone System (USA) DCS: Digital Cellular System CT: Cordless Telephone PDC: Pacific Digital Cellular UMTS: Universal Mobile Telecom. System PAN: Personal Area Network

Mobile devices Laptop Wireless sensors • functionally eq. to desktop • Limited proc. power • standard applications • Small battery Mobile phones • voice, data • simple text displays RFID tag Pager • A few thousands of logical gates • receive only • Responds only • tiny displays PDA • simple text to the RFID reader • simple graphical displays messages requests (no battery) • character recognition • simplified WWW performance performance 5

Upcoming wireless networks g Personal communications g Vehicular networks g Sensor networks g RFID 6

Upcoming wireless networks: personal communications g Proliferation of small operators g Operators in shared spectrum g Mesh networks g Hybrid ad hoc networks g Mesh networks TAP 3 TAP 2 TAP 1 Internet HS TAP 7 TAP 5 TAP 4 7 TAP 6

Preventing greedy behavior at the MAC layer in WiFi hotspots The access point is trusted The access point is trusted Well-behaved node Cheater For more information: http://domino.epfl.ch 8

Wireless Operators in a Shared Spectrum game G = ( Players , Strategy , Utility function ) g operators → players g radio range → strategy g utility: useful coverage of their pilot signal: g = − γ ⋅ coverage interference U i i i i : maximum power range (regulator) R MAX : minimum power range (for coverage) R MIN Static game – Pareto-optimal Nash equilibria γ = = Small : r r R A B MAX γ = = Large : freely roaming users r r R g A B MIN power control of the pilot signal g users attach to the base station with the best g Repeated game – pilot signal: A Nash equilibrium based on R MIN is enforceable using punishments ⎡ ⎤ where the channel gain: ⋅ ⎢ ⎥ P g max i iu ⎢ ⎥ 1 ∑ http://winet-coop.epfl.ch/ + ⋅ = N P g P g ⎢ ⎥ i 0 9 j ju 2 ⎣ ⎦ iu d j iu

Vehicular communications: why? g Combat the awful side-effects of road traffic i In the EU, around 40’000 people die yearly on the roads; more than 1.5 millions are injured i Traffic jams generate a tremendous waste of time and of fuel g Most of these problems can be solved by providing appropriate information to the driver or to the vehicle 10

Example of attack : Generate “intelligent collisions” SLOW DOWN The way Similar attack: stop a highway is clear For more information: http://ivc.epfl.ch 11

European Project SeVeCom • SeVeCom: Secure Vehicular Communications • Started January 2006; Duration: 3 years; Total budget: 3 MEuros • Research topics: key management, secure communication, privacy, tamper-proof device • http://www.sevecom.org • A small, well-balanced consortium, with a precise goal • Partners: 12

Sensor network for environmental monitoring 13 http://www.commonsense.ch

Reference model Application Application Transport Transport Network Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Radio link 14

Layer model i security g Application layer i service location i Signal processing i new applications, multimedia i adaptive applications g Transport layer i congestion and flow control i quality of service g Network layer i addressing, routing, mobility management i hand-over i authentication g Data link layer i media access i multiplexing i media access control i encryption i modulation g Physical layer i interference i attenuation i frequency allocation 15

Overlay Networks - the global view Integration of heterogeneous fixed and mobile networks with varying transmission characteristics wide area vertical hand-over metropolitan area campus-based horizontal hand-over in-house 16

The classical solution for mobile networks g 2 nd generation (GSM, IS-41,…) deployed, 3 rd generation (UMTS,…) recently deployed g Huge, expensive fixed infrastructure g Operational responsibility: network operators (telcos, ISPs) 17

The new paradigm: mobile ad hoc networks g Terminal and node merge g Everything is potentially mobile g Initial applications: communication in the battlefield (Packet Radio Networks, in the 70’s) g The network is self-organized when it is run by the users themselves 18 g Similar trend at the application layer (Napster � Gnutella)

Upper bound for the throughput of ad hoc networks If we have: - identical randomly located nodes n - each capable of transmitting bits/s W λ Then the throughput ( ) obtainable by each node n for a destination is randomly chosen ⎛ ⎞ W λ = Θ⎜ ( ) ⎟ n ⎜ ⎟ log ⎝ n n ⎠ Ref: P. Gupta, P. Kumar, The Capacity of Wireless Networks IEEE Transactions on Information Theory, March 2000 19

Intuition behind the upper bound N nodes (users) O(N) transmissions from left to right over O( ) transmission links N mean 1 O( ) capacity per attempted transmission N Ways to improve scalability: O(N) users O(N) users Ways to improve scalability: • Directional antennas • Directional antennas N Cut set ~ • Locality of the traffic • Locality of the traffic • Hybrid system • Hybrid system 20

Terminal + Node = Terminode www.terminodes.org g All network functions (packet forwarding, flow control, error control,…) and terminal functions (coding/decoding, A/D and D/A, storage, ciphering,…) are embedded in the terminode Destination g A communication must be relayed by intermediate terminodes g The network is self - organized : it is operated by its users g All terminodes are wireless and battery-operated g All terminodes are potentially Source mobile g There exist gateways to other networks (e.g., Internet and 21 cellular networks)

References g J. Schiller: Mobile Communications , Addison-Wesley, Second Edition, 2004 g B. Walke: Mobile Radio Networks , Wiley, Second Edition, 2002 g T. Rappaport: Wireless Communications , Prentice Hall, Second Edition, 2001 g M. Schwartz: Mobile Wireless Communications, Cambridge University Press, 2004 22