Bluetooth Wireless Technology

Transcription

1 Bluetooth Wireless Technology Jamel Lynch Sr.Consultant/ Architect, IBM

2 Agenda Bluetooth Overview What is Bluetooth? What isn t Bluetooth? Bluetooth Air Interface Bluetooth Protocol Stack Bluetooth Profiles Bluetooth Security 2

3 Wireless landscape 3

4 What is Bluetooth? CABLES The term Bluetooth refers to an open specification for a technology to enable short-range wireless voice and data communications anywhere in the world. It is the fastest growing standard ever proposed. Over 2,800 companies have signed up to be adopters of the Bluetooth specification. In 1994 Ericsson initiated study to investigate the feasibility of a low power, low cost, short range radio interface between mobile phones and their accessories. Aim - eliminate cables between mobile phones and PC Cards Ericsson, Nokia, IBM,Intel, Toshiba formed a SIG. 4

5 Why is it called Bluetooth? The Origin of the Bluetooth name: Named after Herald Bluetooth, the Viking King who Christened, united and controlled Denmark and Norway in the 10th century. King of Denmark Bluetooth Wireless technology will unite mobile electronic devices of the world. 5

6 BT Specification adopted by IEEE formed a working group (802.15) to develop standards for WPAN. IEEE approved IEEE standard for PANs SIG provided BT spec 1.1 to IEEE as a candidate for an IEEE 802 WPAN. IEEE licensed wireless technology from the BT SIG. IEEE Adoption Collaboration between standards organization and SIG improve specification. Further strengthens the position of Bluetooth as the de-facto WPAN standard. Formally elevates BT from industry spec into the realm of an official industry standard. BT will be better accepted in the US once one can refer to it as an IEEE standard. 6

7 Bluetooth Industry Timeline New Feature Spec Specification BT v1.1 Core Spec 2.4GHz 721kbps BT v1.2 V1.2 Spec. Ratification Minor spec. release AFH (Adaptive Frequency Hopping) No radio HW nor driver impacts FW update only Backward compatible Ratification & Product BT v2.0 V2.0 Spec Release Major release Higher BW - MR: 2Mbps - HR: 10Mbps HW update (radio) New Profiles Ratification & Product IEEE BT v Standard Bluetooth v1.1 Ratified (MAC & Phy) IEEE future efforts abandoned Current 4Q03 1Q04 2Q04 3Q04 4Q04 1H05 2H05 7

8 Bluetooth Technology Summary Globally free spectrum 2.45 GHz, ISM band GFSK modulation Frequency Hopping (1600 hops/sec) Range 10m piconet (0dBm) 100m optional (+20dBm) Data and voice capable (1Mbps) Full duplex: 478kbps, Asymmetric 721kbps Secure Authentication 128 Encryption Limited Signal range 0 - dbm Pseudo Random hop sequence 8

9 Form factors PC Card Compact Flash USB devices Mini-PCI Secure Digital cards ultraport 9

10 What does Bluetooth provide? Provides point-to-point connections. Provides ad-hoc networking capabilities. Bluetooth specification details how the technology works. Bluetooth Profiles detail how specific applications work to ensure interoperability. 10

11 Master /Slave Bluetooth Network Topology 1 master and up to 7 slaves per piconet. scatternet is not yet supported. 11

12 Point-to-Point (Piconet) Two devices locate each other. Form a connection and transfer data. Wireless cable replacement scenario. The device that initiates the connection is called the Master. Any other devices the Master is connected to are referred to as Slaves. 12

13 Point-to-Multi-Point: The Piconet Two devices create a point-to-point connection. A third device comes into range. The new device is discovered. is added to the piconet and data can be transferred. 13

14 Point-to-Multi-Point: The Piconet Up to seven slaves can be connected to one master. Slaves cannot pass data to other slaves without sending through the master. The master defines the timing for the piconet. 14

15 Piconet-to-Piconet: The Scatternet Scatternets allow devices to be active in numerous piconets. The device can be a slave in one piconet and a master in another. It cannot be a master in two piconets! The device can act as a gateway from one piconet to another. 15

16 Identifying Bluetooth Devices lsb Each Bluetooth device is assigned a unique 48-bit MAC address by the Bluetooth SIG. This is enough addresses for 281,474,976,710,656 Bluetooth units, this should last a few years even with the optimistic predictions of the analysts! The address is split into three parts: LAP: Lower Address Part - used to generate frequency hop pattern and header sync word. UAP: Upper Address Part - used to initialise the HEC and CRC engines. NAP: Non-significant LAP [0:23] Address UAP[24:31] Part - used NAP to seed [32:47] the encryption engine. msb 16

17 Bluetooth Channels A master can create two types of logical channel with a slave device: Asynchronous Connection Less (ACL): Packet Switched System provides a reliable data connection with a best effort bandwidth; depends on radio performance and number of devices in the piconet. Synchronous Connection Oriented (SCO): Circuit Switched System provides real time unreliable connection with a guaranteed bandwidth; usually used for voice based applications. The Bluetooth connections are limited to 1Mbps across the air. This gives a theoretical maximum of ~723kbps of useable data. 17

18 What Bluetooth isn t! Bluetooth is not intended to compete with or replace b, they are complimentary technologies. The data rates, usage scenarios and fundamental ethos behind them are all different! It is unlikely to be used in corporate wireless LAN s. It is not suitable for high data rate applications. High is defined to be >600kbps this allows suitable margin for re-transmissions. Therefore, high quality video streaming is not possible. 18

19 The Air Interface and Bluetooth Baseband 19

20 The ISM Band Bluetooth uses the 2.4GHz ISM frequency band. The Industrial, Scientific and Medical (ISM) band is an unlicensed band, I.e. any one can use it provided they don t exceed certain power constraints. The 2.4GHz ISM band is unlicensed all over the world which makes Bluetooth the only completely world wide standard. Bluetooth uses the frequency range GHz. 20

21 Spectrum Usage The 2.4GHz ISM band is a free for all for anyone who wants to use it. Direct Radio waves Visible X-rays Current 100 khz 300 GHz light Extremely Ultraviolet Gamma low frequency FM radio radiation rays (ELF) MHz Very low frequency Microwaves (VLF) 300 MHz 300 GHz mediumwave radio khz Infrared longwave radio radiation kHz Frequency in hertz (Hz) khz MHz GHz The 2.4GHz ISM Band is also used by: Microwave Ovens. Digital Cordless Phones b. Home RF. Bluetooth 21

22 Overcoming Interference Due to the unrestricted nature of the ISM band, Bluetooth must overcome interference from other systems and minimise its interference on other systems. Bluetooth does this by using a Frequency Hopping Spread Spectrum (FHSS) technique. This spreads the RF power across the spectrum which reduces interference and the spectral power density. 22

23 Frequency Hopping Spread Spectrum - FHSS Bluetooth splits the spectrum up into 79 1MHz wide channels with a small guard band at each end of the whole band. The Bluetooth radio changes transmission frequency 1600 times a second. The frequency hops follow a pseudo random sequence that meets the power density requirements for the FCC and other regulatory bodies. Guard Band Guard Band Frequency, GHz

24 Hop Selection and Synchronisation One frequency hop lasts 625us, this increment is called a time slot. Each Bluetooth device has a clock circuit that counts frequency hops. The address of the master of the piconet is used to seed a frequency hop calculation algorithm. The phase of the hop sequence is defined by the Bluetooth clock of the master. Device address and clock phase information is exchanged during connection negotiation. The slave synchronises its own clock to the master s during connection so that both devices change frequency at the same time. 24

25 The Bluetooth Clock msb lsb C27 The Bluetooth Clock keeps each device synchronised to the Bluetooth slot timing. 28-bit free running clock clocked at 3.2kHz. The clock must have an accuracy of +/-20ppm. Bits of importance: C 0 : 312.5us - Twice slot rate or Inquiry rate. C 1 : 625us - Slot rate. C12 C 12 : 1.28s - Inquiry scan period. C2 C 27 : ~23.3h - Clock wraps about once per day. C1 C0 25

26 Modulation Scheme During each hop, data is transmitted using Gaussian Frequency Shift Keying, G-FSK. FSK uses two different frequencies to transmit a binary 1 or 0. For Bluetooth the two frequencies are: fc + for 1 fc - for 0 where fc = frequency of current hop and = ~157kHz 26

27 Transmission Timing A slave can only send data to the master after it has received a valid packet from the master. Masters transmit in even numbered slots and slaves respond in the next odd numbered slot. Single slot packets are less then 366us long to allow the synthesiser to retune to the next frequency hop. Master f(k + 2) 27 Slave t

28 Time Division Duplex Master and slave alternate transmitting and receiving. 28

29 Power Classes Bluetooth defines 3 power classes for devices: Class 1: 0dBm to +20dBm (1mW to 100mW). Class 2: -6dBm to +4dBm (250uW to 2.5mW). Class 3: <0dBm ( <250uW). These power classes translate in to approximate distances often used when discussing Bluetooth: Class 1: 100 Meters. Class 2: 10 Meters. Class 3: <10 Meters. 29

30 Bluetooth & b interference Bluetooth hops over the entire 2.4 GHz frequency band. Bluetooth splits the spectrum up into 79 1MHz wide channels with a small guard band at each end of the whole band. The Bluetooth radio changes transmission frequency 1600 times a second. The frequency hops follow a pseudo random sequence that meets the power density requirements for the FCC and other regulatory bodies. If there are other users in the band (802.11,Microwave, cordless phones) collisions are unavoidable. Frequency Collision Guard Band Guard Band Frequency, GHz

31 Software Protocol stack : allows devices to locate, connect and exchange data with each other. Major components of the Bluetooth protocol stack Application layer actual applications that make use of BT links. Application, APIs. Middleware layer transport protocols needed for existing and new applications to operate over BT links. SDP, RFCOMM. Transport layer composed of protocols designed to allow devices to locate and to create, configure and manage both physical and logical links that allow higher layer applications to pass data through these transport protocols. L2CAP, link manager. 31

32 Architecture and Protocol Stack Software Firmware Firmware Hardware Hardware Applications TCP/IP HID RFCOMM Data L2CAP Audio Link Manager Baseband RF Control LMP Logical Link Control & Adaptation Protocol (L2C A P ) Segmentation & Reassembly M ultiplexing QoS Link Management Protocol (LMP) Setup and Management of Baseband Connections A uthentication & S ecurity Flow control Baseband & MAC 48bit IEEE address 3 bit connection address P t-pt, P t-m pt links Power efficient modes Link Types: SCO ACL 32

33 What can you do with Bluetooth? The Bluetooth specification defines a series of profiles that aid interoperability between similar devices. The profiles describe applications and usage scenarios for common applications. Application Profile Name Serial Emulation Generic Serial Ad-hoc Network LAN Access Dial up w/ Phone DUN File transfer FTP FAX FAX Audio Headset Print HRCP 33

34 The Bluetooth Ultimate Headset Cable replacement technology Keep your hands free with the ultimate solution for the: Road Office Car Streaming MP3s 34

35 Dial Up Networking (DUN) Profile Allows wireless connection from a PC to a mobile phone for remote LAN or Internet access. Any PC should interoperate with any mobile phone in a secure fashion. Profile interoperability is tested at qualification and voluntarily at UnPlug Fests. 35

36 The Conference Table Create and share informations with your colleagues by forming small private work space Collaborative work File and resource sharing LAN connection 36

37 The Instant Postcard Send instant photos and video clips from any location Suitable for professional as well as private use GSM D-AMPS CDMA PSTN etc. 37

38 Other Profile Examples Electronic Business Card Exchange (OBEX) & P.I.M. Synchronisation Personal Area Networking (PAN) LAN Access 38

39 Bluetooth Security The BT system provides security measures both at the application layer and the application the link layer for usage protection and information confidentiality. Four different entities are used for maintaining security at the link layer A public address unique for each user Two secret keys A random number unique for each new transaction 39

40 Future Usages 40

41 Emerging Technology WLAN WWAN RFID SDR 41

42 WLAN a/b/g Technical Specifications Frequency band a GHz to 5.85 GHz b/g GHz to GHz Modulation a and g: OFDM (54Mbps) b : DBPSK,DQPSK, CCK (11Mbps) Security Data encryption: 64-bit, 128-bit, Wired Equivalency Protection (WEP) 802.1x EAP WPA CCX 42

43 Wireless LAN - Standards b Speed: 11 Mbps Uses: 2.4 GHz band Three non-overlapping channels a Speed: 54 Mbps Uses: 5 GHz band Eight nonoverlapping channels g Speed: 54 Mbps Uses: 2.4 GHz band Three non-overlapping channels h f i e Security and Authentication enhancements Modifications to comply with European regulations Protocol for interoperability between WLAN access points QoS and CoS Mechanisms 43

44 Wireless WAN Switching Technologies Circuit Switching - an electrical physical didcated path that transmits ever-fluctuating voice or data signals. A dedicated path is established through every switch and transmission line needed to connect the call before the person being called ever hears the telephone ring. Packet Switching - a virtual path for data switching. The addresses of the packets are read by the switches and routed to the approiate path. Bursts of data are sent only when needed allowing an "always on state" Wireless Access Standards Frequency Division Multiple Access (FDMA) - analog wireless transmission technology that allocates a single channel to one user at a time Time Division Multiple Access (TDMA) - digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel. Code Division Multiple Access (CDMA) - digital wireless spread spectrum technique allowing multiple users to share the same frequency assigning each active user an individual code 44

45 Wireless WAN W W AN connectivity requires a wireless access device and a wireless network infrastructure, provided by a wireless service carrier. Carrier - wireless service provider providing subscriber access to the network SIM (subscriber identity module - GPRS only) - authentication to service provider W ireless Access Device - device enabling access to the wireless network Mobile PC + + Mobile PC W ireless Access Device carrier The wireless access device sends and receives voice and data via radio waves with radio towers, which carry the signal to a mobile switching center, where the signal is passed on to the appropriate public or private network link. The signal can then be transferred to an organization's existing network. 45

46 Questions Personal Computing Division 46