ECE/CSC 575 – Section 1 Introduction to Wireless Networking

1. ECE/CSC 575 – Section 1 Introduction to Wireless Networking Lecture 22Dr. Xinbing Wang

2. Overview of the Course • Part 1: Wireless communication systems (Chapter 1) • Flexibility to support roaming • Limitations: Geographical coverage, transmission rate, and transmission errors • Part 2: Wireless communication technology • Radio propagation (Chapter 5) • Spread spectrum (Chapter 7) • Part 3: Current wireless systems • Cellular network architecture (Chapter 10) • Mobile IP (Chapter 12) • Wireless LAN (Chapter 11/13/14) • Part 4: Other wireless networks • Ad hoc networks (Reading materials) • Sensor networks (Reading materials) • Wireless PAN (Chapter 15) • Satellite systems (Chapter 9) • Part 5: Wireless Security Dr. Xinbing Wang

3. WPAN--INTRODUCTION • A WPAN (Wireless PAN) is a short-distance wireless network specifically designed to support portable and mobile computing devices such as PCs, PDAs, wireless printers and storage devices, cell phones, pagers, set-top boxes, and a variety of consumer electronics equipment. • Bluetooth is an example of a wireless PAN that allows devices within close proximity to join together in ad hoc wireless networks in order to exchange information. • Many cell phones have two radio interfaces-one for the cellular network and one for PAN connections. Dr. Xinbing Wang

4. WPAN--Bluetooth • WPANs such as Bluetooth provide the bandwidth and convenience to make data exchange practical for mobile devices such as palm computers. • Bluetooth overcomes many of the complications of other mobile data systems such as cellular packet data systems... • The reach of a PAN is typically a few meters. Dr. Xinbing Wang

5. WPAN--Operation (1) • A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range. • Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined. • One device is selected to assume the role of the controller during wireless PAN initialization, and this controller device mediates communication within the WPAN. Dr. Xinbing Wang

6. WPAN--Operation (2) • The controller broadcasts a beacon that lets all devices synchronize with each other and allocates time slots for the devices. • Each device attempts to join the wireless PAN by requesting a time slot from the controller. • The controller authenticates the devices and assigns time slots for each device to transmit data. • The data may be sent to the entire wireless PAN using the wireless PAN destination address, or it may be directed to a particular device. Dr. Xinbing Wang

7. WPAN--IEEE 802.15 • The 802.15 working group is defining different versions for devices that have different requirements. • 802.15.3 focuses on high-bandwidth (about 55M bit/sec), low-power MAC and physical layers, while 802.15.4 deals with low-bandwidth (about 250K bit/sec), extra-low power MAC and physical layers. Dr. Xinbing Wang

8. WPAN: History • WPAN: smaller area of coverage, ad hoc only topology, plug and play architecture, support of voice and data devices, and low-power consumption. • BodyLAN (DARPA, mid-1990s): inexpensive WPAN with modest bandwidth that could connect personal devices within a range of about 5 feet. • 802.11 project initiated a WPAN group in 1997. • In March 1998, the HomeRF group was formed • In May 1998, a Bluetooth special group was formed • In March 1999, 802.15 was approved as a separate group to handle WPAN Dr. Xinbing Wang

9. IEEE 802.15 WPAN • Development of standards for short distance wireless networks used for networking of portable ad mobile computing devices. • The original functional requirement was published in January 22, 1998, and specified devices with: • Power management: low current consumption • Range: 0 - 10 meters • Speed: 19.2 - 100 kbps • Small size: .5 cubic inches without antenna • Low cost relative to target device • Should allow overlap of multiple networks in the same area • Networking support for a minimum of 16 devices Dr. Xinbing Wang

10. IEEE 802.15 Task Groups • The initial activities in the WPAN group included HomeRF and Bluetooth group. • HomeRF currently has its own website [HomeRFweb] • IEEE 802.15 WPAN has four task groups: • Task group 1: based on Bluetooth. Defines PHY and MAC for wireless connectivity with fixed, portable, and moving devices within or entering a personal operating space. • Task group 2: focused on coexistence of WPAN and 802.11 WLANs. • Task group 3: PHY and MAC layers for high-rate WPANs (higher than 20 Mbps) • Task group 4: ultra-low complexity, ultra-low power consuming, ultra-low cost PHY and MAC layer for data rates of up to 200 kbps. Dr. Xinbing Wang

11. WPAN: Piconet • A Bluetooth PAN is also called a piconet, and is composed of up to 8 active devices in a master-slave relationship (up to 255 devices can be connected in 'parked' mode). • The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. • A piconet typically has a range of 10 meters, although ranges of up to 100 meters can be reached under ideal circumstances. Dr. Xinbing Wang

12. Bluetooth • Idea • Universal radio interface for ad-hoc wireless connectivity • Interconnecting computer and peripherals, handheld devices, PDAs, cell phones – replacement of IrDA • Embedded in other devices, goal: 5€/device (2002: 50€/USB Bluetooth) • Short range (10 m), low power consumption, license-free 2.45 GHz ISM • Voice and data transmission, approx. 1 Mbit/s gross data rate Dr. Xinbing Wang

13. Bluetooth One of the first modules (Ericsson). Dr. Xinbing Wang

14. History and hi-tech… Dr. Xinbing Wang

15. Bluetooth: History • History • 1994: Ericsson (Mattison/Haartsen), “MC-link” project • Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen [son of Gorm], King of Denmark in the 10th century • 1998: foundation of Bluetooth SIG, www.bluetooth.org • 1999: erection of a rune stone at Ericsson/Lund • 2001: first consumer products for mass market, spec. version 1.1 released • Special Interest Group • Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba • Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola • > 2500 members • Common specification and certification of products Dr. Xinbing Wang

16. …and the real stone Located in Jelling, Denmark, erected by King Harald “Blåtand” in memory of his parents. The stone has three sides – one side showing a picture of Christ. Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." This could be the “original” colors of the stone. Inscription: “auk tani karthi kristna” (and made the Danes Christians) Btw: Blåtand means “of dark complexion” (not having a blue tooth…) Dr. Xinbing Wang

17. Characteristics • 2.4 GHz ISM band, 79 RF channels, 1 MHz carrier spacing • Channel 0: 2402 MHz … channel 78: 2480 MHz • G-FSK modulation, 1-100 mW transmit power • FHSS and TDD • Frequency hopping with 1600 hops/s • Hopping sequence in a pseudo random fashion, determined by a master • Time division duplex for send/receive separation • Voice link – SCO (Synchronous Connection Oriented) • FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched • Data link – ACL (Asynchronous ConnectionLess) • Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched • Topology • Overlapping piconets (stars) forming a scatternet Dr. Xinbing Wang

18. Bluetooth: Protocol Stack Dr. Xinbing Wang

19. 625µs fk fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 M S M S M S M t fk fk+3 fk+4 fk+5 fk+6 M S M S M t fk fk+1 fk+6 M S M t Frequency Selection During Data Transmission (TDMA/TDD) symmetric asymmetric asymmetric Dr. Xinbing Wang

20. 72 54 0-2745 bits access code packet header payload 4 64 (4) 3 4 1 1 1 8 preamble sync. (trailer) S address type flow ARQN SEQN HEC Bluetooth: Frame Format (1) • The 48 bit address unique to every Bluetooth device is used as the seed to derive the sequence for hopping frequencies of the devices. • Four types of access codes: • Type 1: identifies a “M” terminal and its piconet address • Type 2: identifies a “S” identity used to page a specific “S”. • Type 3: Fixed access code reserved for the inquiry process (will be explained) • Type 4: dedicated access code reserved to identify specific set of devices such as fax machines, printers, or cell phones. • Header: 18 bits repeated 3 times with a 1/3 FEC code bits Dr. Xinbing Wang

21. 72 54 0-2745 bits access code packet header payload 4 64 (4) 3 4 1 1 1 8 preamble sync. (trailer) S address type flow ARQN SEQN HEC Bluetooth: Frame Format (2) • S-address allows addressing the 7 possible “S” terminals in a piconet • The 4-bit packet type allows for 16 choices of different grade voice systems: • 6 of this payload types are asynchronous connectionless (ACL), primarily used for packet data communication • 3 of the payload types are synchronous connection oriented (SCO), primarily used for voice communications • 1 a integrated voice (SCO) and data (ACL) packet • 4 are control packets common for both SCO and ACL links bits Dr. Xinbing Wang

22. Bluetooth: Control Packets • Four types: • ID: occupies half of a slot, and it carries the access code with no data or even a packet type code • NULL: used for ACK signaling, and there is no ACK for it • POLL: similar to the NULL, but is has an ACK • NULL and POLL: have the access code and the header, and so they have packet type codes and status report bits • “M” terminals use the POLL packet to find the “S” terminals in their coverage area. • FHS (Frequency Hop Synchronization): carries all the information necessary to synchronize two devices in terms of access code and hopping timing. This packet is used in the inquiry and paging process explained later. Dr. Xinbing Wang

23. SCO ACL SCO ACL SCO ACL SCO ACL f14 f0 f6 f12 f18 f8 f4 f20 f1 f7 f13 f19 f9 f17 f5 f21 Polling-Based Transmission • Polling-based TDD packet transmission • 625µs slots, master polls slaves • SCO (Synchronous Connection Oriented) – Voice • Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point • ACL (Asynchronous ConnectionLess) – Data • Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint MASTER SLAVE 1 SLAVE 2 Dr. Xinbing Wang

24. Piconet • Collection of devices connected in an ad hoc fashion • One unit acts as master and the others as slaves for the lifetime of the piconet • Master determines hopping pattern, slaves have to synchronize • Each piconet has a unique hopping pattern • Participation in a piconet = synchronization to hopping sequence • Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked) P S S M P SB S P SB P=Parked SB=Standby M=Master S=Slave Dr. Xinbing Wang

25.    P  S SB  SB  S   SB   M P SB SB   SB   S   SB SB  P SB  SB SB Forming a Piconet • All devices in a piconet hop together • Master gives slaves its clock and device ID • Hopping pattern: determined by device ID (48 bit, unique worldwide) • Phase in hopping pattern determined by clock • Addressing • Active Member Address (AMA, 3 bit) • Parked Member Address (PMA, 8 bit) Dr. Xinbing Wang

26. Piconets (each with a capacity of < 1 Mbit/s) P S S S P P M M SB S P SB SB S Scatternet • Linking of multiple co-located piconets through the sharing of common master or slave devices • Devices can be slave in one piconet and master of another • Communication between piconets • Devices jumping back and forth between the piconets M=Master S=Slave P=Parked SB=Standby Dr. Xinbing Wang

27. Data rate Synchronous, connection-oriented: 64 kbit/s Asynchronous, connectionless 433.9 kbit/s symmetric 723.2 / 57.6 kbit/s asymmetric Transmission range POS (Personal Operating Space) up to 10 m with special transceivers up to 100 m Frequency Free 2.4 GHz ISM-band Security Challenge/response (SAFER+), hopping sequence Cost 50€ adapter, drop to 5€ if integrated Availability Integrated into some products, several vendors Connection set-up time Depends on power-mode Max. 2.56s, avg. 0.64s Quality of Service Guarantees, ARQ/FEC Manageability Public/private keys needed, key management not specified, simple system integration Special Advantages/Disadvantages Advantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency Summary IEEE 802.15-1 Bluetooth Dr. Xinbing Wang

28. Interference Between Bluetooth and 802.11 • The WLAN industry specified three levels of overlapping: • Interference: multiple wireless networks are said to interfere with one another if colocation causes significant performance degradation • Coexistence: multiple wireless networks are said to coexist if they can be colocated without significant impact on performance. It provides for the ability of one system to perform a task in a shared frequency band with other systems that may or may not be using the same rules for operation • Interoperation: provides for an environment with multiple wireless systems to perform a given task using a single set of rules Dr. Xinbing Wang

29. IEEE 802.15 WPAN– Future • 802.15-2: Coexistence • Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference • 802.15-3: High-Rate • Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost • Data Rates: 11, 22, 33, 44, 55 Mbit/s • Quality of Service isochronous protocol • Ad hoc peer-to-peer networking • Security • Low power consumption • Low cost • Designed to meet the demanding requirements of portable consumer imaging and multimedia applications Dr. Xinbing Wang