BLUETOOTH TM :A new radio interface providing ubiquitous connectivity

1. BLUETOOTHTM:A new radio interface providing ubiquitous connectivity Jaap C.Haartsen Ericssion Radio System B.V. 2000 IEEE

2. Introduction • A new universal radio interface that enable electronic devices to connect and communicate via short-range radio connections • Operates in the unlicensed 2.45GHz frequency band and makes use of frequency hopping

3. Introduction • Low-power,small-sized and low-cost radios that can be embedded in a wide range of future products • The interface supports: • Synchronous services—voice • Asynchronous services—file transfer

4. History • At the beginning of 1998, a group of five companies—Ericsson, Nokia, IBM, Toshiba, and Intel—founded a Special Interest Group • At the end of 1999, the group was extended with Microsoft, Motorola, Lucent, and 3COM to further develop

5. General Purposes • Bridging standards:a universal access mechanism • Functional integration: a functional integration is obtained by connecting several devices wirelessly • Universal interface: provide a universal interface and overcome incompatible connectors and protocols

6. The BluetoothTM air interface • Peer connectivity • Unlicensed spectrum • FSK transceivers • Dynamic slot structure • Packet transmission

7. Peer Connectivity • BluetoothTM is based on peer connectivity: any device must be able to connect to any other device • Cellular phone and wireless LANs system is based on an infrastructure of interconnected stationary base stations

8. Unlicensed spectrum • The ISM band ranging from 2400 MHz to 2483.5 MHz • A major issue for BluetoothTM is interference immunity • Optimal interference immunity against jammers is obtained by frequency hopping

9. Unlicensed spectrum (cont.) • BluetoothTM is based on FH-CDMA using 79 carriers 1MHz spaces • The nominal hopping rate is 1600 hops/s • Each BluetoothTM unit has its own pseudo-random hopping sequence

10. Hop selection mechanism

11. PSK transceivers • The air interface uses a Gaussian-shaped (BT=0.5) FSK modulation with a symbol rate of 1 Ms/s • Gives a –20dB spectral bandwidth of 1 MHz • FSK radios are simple, cheap, and robust

12. Dynamic slot structrue • The BluetoothTM air interface is based on time slots • A time slot lasts 625 us • In a point-to-point connection, one unit always starts to transmit in the even-numbered slots where the other unit transmit in the odd-numbered slots

13. Dynamic slot structrue (cont.) • A circuit-switched connection is created by a SCO(Synchronous Connection-Oriented) link • All slot not in use for SCO links can be used for packet-switched traffic through a ACL(Asynchronous Connection-Less) link

14. Dynamic slot allocation

15. Packet transmission • The information stream is fragmented into packets • Only one packet can be sent in each slot • All packets have the same format: access code, packet header, user payload

16. Packet format

17. Packet transmission (cont.) • Access code : the identity of the master • Packet header : • 3-bit slave address • 2-bit ARQ control information • 4-bit packet type code • 8-bit header-error-check(HEC) code

18. The BluetoothTM connectivity • Pico- and scatternets • Connection establishment • Synchronization • Security

19. Pico- and scatternets • Two or more BluetoothTM units sharing the same FH channel form a piconet • A cluster of co-located, independent piconet is called a scatternet • The number of units active in a piconet is limited to 8

20. Pico- and scatternets (cont.) • The master-slave concept has been introduced • One unit in the piconet is assigned to be the master • The remaining units participating on the channel are slaves

21. Pico- and scatternets (cont.) • The master-slave are only roles which exist during the presence of the piconet • Using the 3-bit slave address in the header, the master can direct packets to the proper recipients

22. Connection establishment • The pager :the unit who wants to make the connection • The recipient :the unit in standby that must be susceptible to the pager • The burden of solving the time-frequency uncertainty has been placed at the pager

23. Standby state • A unit in standby resides in a low-power state • Sleeps most of the time • Wakes up at the fixed intervals to scan a single hop carrier for a short period of time

24. Page message • Consists of a single 68-bit code • A shortened version of the 72-bit access code used in front of the packet • The code is derived from the identity of the recipient

25. Paging • To page a unit, its identity must be known • If a pager has no identity or wants to discover which units are in range, it can issue an inquiry message • The inquiry procedure works similar as the page procedure

26. Synchronization • In the BluetoothTM system, each unit has a free-running native clock • An accuracy of 20ppm when the unit is active and 250ppm when the unit is in a low-power mode

27. Synchronization (cont.) • A BluetoothTM unit have a list of unit addressed with corresponding native clocks • The slave add an offset to their native clock in order to be hop synchronized to the master

28. Synchronization

29. Security • Apply a conventional challenge-response scheme • To prevent eavesdropping, payload information is encrypted • Keys of 128 bits are pair-wise generated during an initialization phase

30. Conclusion • BluetoothTM is a young technology • The applications seem to be unlimited and new scenarios are discussed every day • Higher data rates are envisioned which will boost the current data rate by a factor 10 to 20