Seminar: Mobile Systems. Krzysztof Dabkowski Supervisor: Fabio Hecht

Transcription

1 Personal Area Networks Seminar: Mobile Systems November 19th 2009 Krzysztof Dabkowski Supervisor: Fabio Hecht

2 Agenda Motivation Application areas Historical and technical overview Security issues Discussion

3 Motivation From: numerous mobile and stationary devices To: self-organizing network

4 The idea market view Wireless network that cover a small geographical area Self-organizing, ad hoc networks Seamless plugging in Ubiquitous computing

5 Application areas Being constantly online 4G technology Body Area Network (BAN) Devices integrated with a human user E.g. physiology measurements in sports Healthcare Health status sensed wireless sensors Providing information about the health status of a patient Long-time measurements Smart things Smart home Smart car Ambient intelligence

6 standardization March 1999 IEEE 802 forms a Working Group to work on WPANs Multiple suppliers of technologies and services Cost-effective devices, services and implementation Open systems for interoperability, and ease of use Standard interfaces World-wide regulatory acceptance of standards-based technology Task Group 1 Bluetooth specification Task Group 2 Recommended Practice for Coexistance Task Group 3 High Rate WPANs Task Group 4 promoting and understanding

7 Issues Coexistance 2.4 GHz ISM band Interference from other devices Share Physical Layer Interoperability Inter-application operability Interoperability classes (4 0) determine also coexistance

8 Bluetooth Emerged as an alternative to RS232 Bluetooth protocol stack Set of specified protocols Companies-dependant implementations Profile interface specification Protocols, options, parameters Dependencies on other profiles Suggested user interface format Aplication Presentation Session Transport Network Data Link Physical

9 Piconets and scatternets Several piconets form scatternets Communication between piconets goes through interpiconet nodes Single device different roles in different piconets New units join a piconet All communication goes through the master unit Time Division Duplex ms slot

10 Routing in Bluetooth Requirements Extremely strong volatility Lack of external network devices (e.g. routers) Interconnection to other types of networks Strongly influenced by IP-based mobile ad hoc networks (MANETs) algorithms 48-bit address (BD-ADDR) Bluetooth Network Encapsulation Protocol (BNEP) Interconnection and independence from higher-layer protocols Scheduling mechanisms Intra- and interpiconet scheduling

11 Ultra-wideband (UWB) Radio technology physical layer (base technology for WUSB) Emerged in 60s, applied to radar systems Several operational bands: GHz and 6.2 9,7 GHz (Direct Spread UWB) GHz (Multi Band OFDM) Efficient use of scarce radio bandwith high data rate PAN longer-range applications radar systems Time-modulation UWB 1.3 giga-pulses per second up to 675 Mbit/s with error correction and encoding Low power, data rate quickly decrease with increase of distance Aplication Presentation Session Transport Network Data Link Physical

12 Wireless USB Primarily, connect PC with peripherals Objective: leverage experience gained from USB Developed by Wireless USB Promoter Group Hewlett-Packart Intel Microsoft NEC Philips Samsung Aplication Presentation Session Transport Network Data Link Physical

13 WUSB topology Hub-and-spoke Each spoke is a pointto-point connection Up to 127 devices All devices have to be MAC-suited

14 ZigBee Low data rate PAN standard Defined by the ZibBee Alliance as an adaptation of the IEEE TG4 Target: Applications requiring low data rate (from 250 kbps at 2.4 GHz to 20 kbps at 868 Mhz) Low energy consumption long battery life Low cost Need for security E.g. sensor networks Aplication Presentation Session Transport Network Data Link Physical

15 ZigBee technical details Two types of physical devices Full Function Device (FFD) Can become a network coordinator Similarity to a master unit in Bluetooth Reduced Function Device (RFD) Can be used only in star topology and only as a distant unit Communicates only with network coordinator Cost saving carrier sense, multiple access/collision avoidance (CSMA/CA) Check if no one is talking before starting communication

16 ZigBee - topoogies

17 Need for security Plethora of personal devices personal information Data synchronization (calendar, contacts) puts the data into the network Accessible for everyone applications

18 Security in bluetooth E0 stream cypher PIN code used to generate an encryption key Security manager application, multiplexing protocol (e.g. BNEP), logical link layer mechanism Storage of information about divices and services Decisions about access and disconnection Application of authentication and authorisation Device Trust Level (trusted, untrusted) Security Level of Services (authorisation required, encryption required)

19 Security in ZigBee AES algorithm as the base for security Three modes: AES in Counter (CTR) mode used at MAC layer, ensures encription AES in Cipher Block Chaining (CBC-MAC) Counter with CBC-MAC (CCM) mode Combination of encryption and integrity Responsibilities: MAC layer: security over a single hop Upper layers: security over multi-hop messaging only when using CCM mode

20 Security in WUSB AES-128 as encryption method (in CCM mode) Public key encryption only for authentication Wired connection recognized as secure seamless secure combination of wireless and wire communication

21 PAN vs. Wi-Fi Specification Wireless USB ZigBee Bluetooth 2.1 Bluetooth 4.0 Wi-Fi (IEEE n) Frequency band 3.1 GHz 10.6 GHz 2.4 GHz and 868/915 MHz 2.4 GHz UWB (not decided) 2.4 GHz/5 GHz Bandwidth Mbit/s kbps Max. 3 Mbit/s Mbit/s Max. 600 Mbit/s Distance 3-10 m 50 m 100 m (usually 10 m) 3 10 m 100 m Security Encryption, Encryption, Encryption, Firewalling, WEP, Encryption authentication authentication authentication WPA Uses Game controllers, printers, digital cameras, drives Self-organizing mesh networks; sensor networks Communication between similar devices in range Communication between similar devices in range IP networks, managed and organized by network devices Standardization May 2005 November 2007 July 2007 pre-standard September 2009

22 Summary Wireless self-organizing, ad-hoc networks Idea of ubiquitous computing Standards (Bluetooth, WUSB, ZigBee, UWB) Security issues

23 Thanks for your attention!

24 Discussion question 1 Are the presented WPAN technologies likely to take over Wi-Fi connectivity, to converge with them or lose the competition?

25 Discussion question 2 What issues can/will PAN technologies face? Could the issues be addressed by them or will the standards go in different direction?

26 Discussion question 3 Are PANs going to be commonly used in people s everyday lifes?