1. Page 1 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Wireless Communication Protocols and Technologies Mm1 Introduction. Wireless LANs (TKM) Mm2 Wireless Personal Area Networks and Bluetooth (TKM) Mm3 IP Mobility Support (HPS) Mm4 Ad hoc Networks (TKM) Mm5 Overview of GSM, GPRS, UMTS (HPS)

2. Page 2 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Outline WLAN IEEE 802.11 (cont) Bluetooth Additional information Jochen Schiller, Mobile Communications, Ch. 7.5 http://www.bluetooth.com/ J. Haarsten, Bluetooth – The universal radio interface for ad hoc, wireless connectivity, Ericsson Review, No. 3, 1998 B.A. Miller, C. Bisdikian. Bluetooth Revealed, Prentice Hall, 2001

3. Page 3 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 DFWMAC Network Allocation Vector (NAV) is time field that indicates the duration of the current transmission Backoff procedure is used to randomized access to the channel t SIFS DIFS ACK defer access other stations receiver sender data DIFS Medium busy RTS CTS SIFS NAV (RTS) NAV (CTS) backoff

4. Page 4 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Trade-offs with RTS/CTS +Collisons are avoided +Hidden station problem is solved –Bandwidth reduction –Not with multicast and broadcast Usage With large frames When collisions are likely

5. Page 5 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Fragmentation t SIFS DIFS data ACK 1 other stations receiver sender frag 1 DIFS contention RTS CTS SIFS NAV (RTS) NAV (CTS) NAV (frag 1 ) NAV (ACK 1 ) SIFS ACK 2 frag 2 SIFS Large frames handed down from the LLC to the MAC may require fragmentation to increase transmission reliability Fragmentation_threshold the channel is not released until the whole frame is transmitted successfully or the source fails to receive ACK for a fragment.

6. Page 6 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 DFWMAC-PCF PIFS stations‘ NAV wireless stations point coordinator D1D1 U1U1 SIFS NAV SIFS D2D2 U2U2 SuperFrame t0t0 medium busy t1t1 The beginning of a super frame is indicated by a beacon transmitted by AP. (synchronization) the minimum duration of PCF period is time required to send 2 frames + overhead + PCF-end-frame the maximum duration - time must be allotted for at least one frame to be transmitted during DCF period

7. Page 7 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 DFWMAC-PCF t stations‘ NAV wireless stations point coordinator D3D3 NAV PIFS D4D4 U4U4 SIFS CF end contention period contention free period t2t2 t3t3 t4t4

8. Page 8 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 802.11 - MAC management Synchronization –try to find a LAN, try to stay within a LAN –timer etc. Power management –sleep-mode without missing a message –periodic sleep, frame buffering, traffic measurements Association/Reassociation –integration into a LAN –roaming, i.e. change networks by changing access points –scanning, i.e. active search for a network

9. Page 9 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Synchronization using a Beacon (infrastructure) beacon interval t medium access point busy B BBB value of the timestamp B beacon frame

10. Page 10 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Synchronization using a Beacon (ad- hoc) t medium station 1 busy B1B1 beacon interval busy B1B1 value of the timestamp B beacon frame station 2 B2B2 B2B2 random delay

11. Page 11 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Power management Idea: switch the transceiver off if not needed States of a station: sleep and awake Timing Synchronization Function (TSF) –stations wake up at the same time Infrastructure –Traffic Indication Map (TIM) list of unicast receivers transmitted by AP –Delivery Traffic Indication Map (DTIM) list of broadcast/multicast receivers transmitted by AP Ad-hoc –Ad-hoc Traffic Indication Map (ATIM) announcement of receivers by stations buffering frames more complicated - no central AP collision of ATIMs possible (scalability?)

12. Page 12 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Power saving with wake-up patterns (infrastructure) TIM interval t medium access point busy D TTD T TIM D DTIM DTIM interval BB B broadcast/multicast station awake p PS poll p d d d data transmission to/from the station

13. Page 13 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Power saving with wake-up patterns (ad-hoc) awake A transmit ATIM D transmit data t station 1 B1B1 B1B1 B beacon frame station 2 B2B2 B2B2 random delay A a D d ATIM window beacon interval a acknowledge ATIM d acknowledge data

14. Page 14 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 IEEE 802.11 a and b IEEE 802.11bIEEE 802.11a Time TableStandard in 1997Standard in 2001 Frequency Band and bandwidth 2.4 GHz5 GHz Speed11 Mbps54 Mbps Modulation TechniquesSpread SpectrumOFDM (Orthogonal Frequency Division Multiplexing Distance CoverageUp to 100 meters20 meters - speed goes down with increased distance InteroperabilityCurrent problems expected to be resolved in future Problems now but expect resolution soon CostCheaper - $300 for access point and $75 for adapter More expensive - $500 in 01/2002 - Interference with other devicesBand is more polluted - significant interference here Less interference because of few devices in this band

15. Page 15 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 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 2.4 GHz ISM Voice and data transmission, approx. 1 Mbit/s data rate One of the first modules (Ericsson)

16. Page 16 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 History –1994: Ericsson (Mattison/Haartsen), project –Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen, King of Denmark in the 10th century –1998: foundation of Bluetooth SIG, www.bluetooth.org –2001: first consumer products for mass market, spec. version 1.1 released –BT is de facto standard for present PAN technology –1999: IEEE 802.15 WG was created to develop WPAN standard 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

17. Page 17 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 The rune stone is 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."

18. Page 18 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 1999: Ericsson mobile communications AB reste denna sten till minne av Harald Blåtand, som fick ge sitt namn åt en ny teknologi för trådlös, mobil kommunikation.

19. Page 19 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Characteristics Unlincensed 2.4 GHz Industrial-Scientific-Medical (ISM) band, 79 (23) 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

20. Page 20 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 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 may only contain 1 master and up to 7 simultaneous/ active slaves (> 200 could be parked) 7 slaves --> in order to keep high-capacity links between all the units + to limit the addressing overhead M S S S SB P P M=Master S=Slave P=Parked SB=Standby

21. Page 21 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 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) SB M S P S S P P                  

22. Page 22 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Synchronization / Clocks Slaves add time offsets to their native clocks to synchronize to the frequency hopping  to calculate the phase

23. Page 23 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Scatternet A Scatternet is the 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 –Devices jumping back and forth between the piconets M M S S S S P SB P P M=Master S=Slave P=Parked SB=Standby

24. Page 24 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Twelve piconets interconnected into a single scatternet There is no direct transmittion between slaves in a piconet; only from master to a slave and vica versa

25. Page 25 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Communication in a piconet Polling-based TDD packet transmission –625µs slots, master polls slaves Master polls slaves according to a polling scheme. Slave transmits only after it has been polled. NULL packet  Master schedules the traffic in both the uplink and downlink  completely contention-free access  intelligent scheduling algorithms are needed

26. Page 26 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Multislot packets 3-slot and 5-slot packets Multi-slot packets are sent on a single-hop carrier Independ piconets can interfere when they occasionaly use the same hop carrier  «no listen-before-talk»

27. Page 27 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Format of packets –Access code Channel, device access, e.g., derived from master –Packet header 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating bit ARQ/SEQ, checksum access codepacket headerpayload 68(72)540-2745bits AM addresstypeflowARQNSEQNHEC 341118bits preamblesync.(trailer) 464(4)

28. Page 28 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Link types 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

29. Page 29 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Types of packets 4 control packets ID (identification packet) - used for signalling NULL - consists of access code+header POLL - used by a master to force a slave to return a responce FHS (FH synchronisation) - used to exchange clock and ID information between units 12 types packets for synchronous and asynchronous services

30. Page 30 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 PayloadUserSymmetricAsymmetric HeaderPayloadmax. Rate max. Rate [kbit/s] Type[byte][byte]FECCRC[kbit/s]ForwardReverse DM110-172/3yes108.8108.8108.8 DH110-27noyes172.8172.8172.8 DM320-1212/3yes258.1387.254.4 DH320-183noyes390.4585.686.4 DM520-2242/3yes286.7477.836.3 DH520-339noyes433.9723.257.6 AUX110-29nono185.6185.6185.6 HV1na101/3no64.0 HV2na202/3no64.0 HV3na30nono64.0 DV1 D10+(0-9) D2/3 Dyes D64.0+57.6 D ACL 1 slot 3 slot 5 slot SCO Data Medium/High rate, High-quality Voice, Data and Voice

31. Page 31 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Connection Establishment Device discovery problem Page: device ID is known, no knowledge of the clock of the device Page/ Scan/ Responce Inquiry: an inquirerer can detrmine which units are in range Inquiry/ Inquiry scan/ Responce Wake-up hop sequence is 32 hops in length and is cyclic

32. Page 32 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 States of a BT device Standby: do nothing Inquire: search for other devices Page: connect to a specific device Connected: participate in a piconet Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACLs, SCO still possible, possibly participate in another piconet

33. Page 33 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Sniff mode To reduce the duty cycle of the slave’s listen activity by only listening in specified slots parameters of sniff mode are negotiated between master and slave master can start transmission only in the sniff attempt interval Offset Sniff attempt Sniff Timeout Sniff interval Sniff attempt Sniff Timeout Sniff interval

34. Page 34 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Hold mode Hold mode stops ACL traffic for a specified period of time; it does not affect SCO traffic parameter hold time is negotiated. After hold time, slave «wakes up» 6*T poll or 9*T poll Hold time

35. Page 35 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Park mode Slave gives up its AR_ADDR (3 bit), gets PM_ADDR (8 bit) slaves wakes up periodically in predefined intervals to listen to the channel to synchronize and listen for broadcast messages clock drift

36. Page 36 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Examples of usage of lattency modes Sniff mode can be applied in scenarious with periodic traffic and is normally used to save power on low data rates. Hold mode can be used to perform another activity such as inquery, page or scan operation/ or for participation in another piconet Park mode is generally used to handle more than 7 slaves in a piconet

37. Page 37 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Bluetooth Research Interoperability Bluetooth and WLAN –Same frequency, different access, no coordination –IEEE working group: Adaptive Frequency Hopping Topology maintenence –Efficient interpiconet communication –Routing in Bluetooth scatternets Ad-hoc networking –How to build spontaneous networks –How to make this fast, but secure

38. Page 38 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 User scenario Connection of peripheral devices Support for ad hoc networking –Interactive conference – connect every participant for instant data exchange Bridging networks –Three-in-one phone – use the same phone everywhere ? Sensor networks Bluetooth access points –Aalborg Zoo

39. Page 39 Tatiana K. Madsen Hans Peter Schwefel WCPT Spring 2004 Concluding remarks BT has been optimized to allow a large number of uncoordinated communications to take place in the same area. Convergence of computer and communication worlds