Local Area Networks NETW 901 Lecture 6 IEEE 802.15.1 - Bluetooth Course Instructor: Dr.-Ing. Maggie Mashaly maggie.ezzat@guc.edu.eg C3.220 1
The 802.15 Family Target environment: communication of personal devices working together Short range Low power Low cost Small number of devices Four Standards IEEE 802.15.1 Bluetooth IEEE 802.15.2 Interoperability IEEE 802.15.3 High Data Rate WPAN IEEE 802.15.4 Low Data Rate WPAN (ZigBee) 2
What is Bluetooth? It is a universal radio standard for adhoc wireless connectivity with the following characteristics: Low cost of Bluetooth modules Short range (10m) Low power consumption Operates license free at 2.45 GHz Used for voice and data transmission (1Mb/s gross data rate) 3
What is Bluetooth? Bluetooth History Ericsson started a research project on Bluetooth in 1994 Bluetooth SIG (Special Interest Group) was founded in 1998 www.bluetooth.com Version 1.1 of consumer products was released to the market in 2001 Development until 2017 SIG hosts 30,000 member companies Bluetooth can be found in 90% of all mobile devices More than 2.5 billion products shipped annually 4
What is Bluetooth? Strange name? Named after 10 th century Viking King (Harald Blatand, A.K.A., Bluetooth) The king had peacefully united all the tiny island kingdoms of Denmark, Southern Sweden and Southern Norway in one country Bluetooth was named after him since it was designed as a low-cost radio technology to unite or collect all different types of devices to effectively work as one 5
Bluetooth Characteristics 2.4 GHz ISM band, 79 RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz channel 78: 2480 MHz G-FSK modulation (Gaussian Frequency Shift Keying), 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 6
Bluetooth Characteristics 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, packet switched Topology Overlapping piconets (stars) forming a scatternet 7
What is a 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 The master is the unit that establishes 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 8
What is a Piconet? Each piconet has one master and up to 7 simultaneous slaves ( >200 could be parked) If more than 7 devices are to be connected, extra devices will be put into low power mode (Parked) When a parked device wants to actively participate in the network it does so by exchanging roles with the least active device Nodes in Standby mode have their radio switched-off 9
Forming a Piconet Any two or more device can form a piconet where the device establishing the piconet becomes the master Master sends its clock and device ID to the slaves Hopping pattern determined by the device ID Phase is determined by the clock of the master Addressing: Active Member Address (AMA, 3 bit) Parked Member Address (PMA, 8 bit) 10
Scatternet Scatternet = group of piconets Device can participate multiple piconets Jumping between hopping sequences of the different piconets Before leaving a device informs the current master that it will be unavailable for a certain amount of time A device can be a slave in one piconet and master of another 11
Bluetooth Protocol Stack audio apps. NW apps. vcal/vcard telephony apps. mgmnt. apps. TCP/UDP OBEX IP BNEP PPP AT modem commands TCS BIN SDP Control Audio RFCOMM (serial line interface) Logical Link Control and Adaptation Protocol (L2CAP) Link Manager Baseband Radio Host Controller Interface AT: Attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. 12
Bluetooth Protocol Stack Bit oriented protocol defines signaling for establishing voice communication audio apps. NW apps. vcal/vcard telephony apps. mgmnt. apps. Emulates a serial line TCP/UDP IP BNEP PPP OBEX AT modem commands TCS BIN SDP Control Audio RFCOMM (serial line interface) Logical Link Control and Adaptation Protocol (L2CAP) Link Manager Baseband Host Controller Interface Radio AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. 13
Bluetooth Radio Layer Uses license free 2.4 GHz 1600 hopes per second 79 hop carriers with 1 MHz spacing Use three Power classes Class 1 maximum power of 100mW and min power of 1 mw Power control is mandatory Class 2 maximum power of 2.5 mw and min power of 0.25 mw 10 m typical range Power control optional Class 3 Maximum power is 1 mw 14
Bluetooth Radio Layer Frequency selection during data transmission 625 µs f k f k+1 f k+2 f k+3 f k+4 f k+5 f k+6 M S M S M S M Three slot packet t f k f k+3 f k+4 f k+5 f k+6 M S M S M t f k Five slot packet f k+1 f k+6 M After transmitting the packet the radio return to the frequency required for its hoping S M t 15
Bluetooth Baseband Access code Needed for timing, synchronization, and pioneer identification It may represent special codes during paging (device access code) and inquiry Synchronization field is derived from the lower 24 bits of an address If access code is used for channel access it is derived from the master 48 bit address In case paging the LAP (Linear Address Pointer) of the paged device is used For discovery a special LAP is used access code packet header payload 68(72) 54 0-2745 bits 4 64 (4) preamble sync. (trailer) 3 4 1 1 1 8 bits AM address type flow ARQN SEQN HEC 16
Bluetooth Baseband Packet Header 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating bit ARQ/SEQ, checksum 68(72) 54 0-2745 bits access code packet header payload 4 64 (4) preamble sync. (trailer) 3 4 1 1 1 8 bits AM address type flow ARQN SEQN HEC 17
Bluetooth Baseband Link Types 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 SCO ACL SCO ACL SCO ACL SCO ACL f 0 f 6 f 8 f 12 f 4 f 20 f 14 f 18 SLAVE 1 f 1 f 7 f 9 f 13 f 19 SLAVE 2 f 5 f 21 f 17 18
Bluetooth Baseband Data Rates ACL 1 slot 3 slot 5 slot SCO Payload User Symmetric Asymmetric Header Payload max. Rate max. Rate [kbit/s] Type [byte] [byte] FEC CRC [kbit/s] Forward Reverse DM1 1 0-17 2/3 yes 108.8 108.8 108.8 DH1 1 0-27 no yes 172.8 172.8 172.8 DM3 2 0-121 2/3 yes 258.1 387.2 54.4 DH3 2 0-183 no yes 390.4 585.6 86.4 DM5 2 0-224 2/3 yes 286.7 477.8 36.3 DH5 2 0-339 no yes 433.9 723.2 57.6 AUX1 1 0-29 no no 185.6 185.6 185.6 HV1 na 10 1/3 no 64.0 HV2 na 20 2/3 no 64.0 HV3 na 30 no no 64.0 DV 1 D 10+(0-9) D 2/3 D yes D 64.0+57.6 D Data Medium/High rate, High-quality Voice, Data and Voice 19
Bluetooth Physical Links Synchronous Connection Oriented (SCO) Allocates fixed bandwidth between point-to-point connection of master and slave Master reserves two consecutive slots at fixed interval Master can support three simultaneous SCOs to the same slave or different slaves A slave supports two links from different masters or three links from the same master. Each SCO carries voice at 64 Kbit/s and 0,2/3 or 1/3 FEC 20
Bluetooth Physical Links Synchronous Connection Oriented (SCO) SCO Payload Types payload (30) HV1 audio (10) FEC (20) HV2 audio (20) FEC (10) HV3 audio (30) DV audio (10) header (1) payload (0-9) 2/3 FEC CRC (2) (bytes) 21
Bluetooth Physical Links Asynchronous connectionless (ACL) Point-to-multipoint link between master and all slaves Master uses polling scheme A slave answers only if it has been addressed in the previous slot Only single ACL link can exist Data can be protected using a 2/3 FEC Fast Automatic repeat Request can be used 22
Bluetooth Physical Links Asynchronous connectionless (ACL) ACL payload types payload (0-343) header (1/2) payload (0-339) CRC (2) DM1 header (1) payload (0-17) 2/3 FEC DH1 header (1) payload (0-27) CRC (2) CRC (2) (bytes) DM3 DH3 header (2) payload (0-121) 2/3 FEC header (2) payload (0-183) CRC (2) CRC (2) DM5 DH5 header (2) payload (0-224) 2/3 FEC header (2) payload (0-339) CRC (2) CRC (2) AUX1 header (1) payload (0-29) 23
Bluetooth Robustness Slow frequency hopping with hopping patterns determined by a master Protection from interference on certain frequencies Separation from other piconets (FH-CDMA) Retransmission ACL only, very fast Forward Error Correction SCO and ACL Error in payload (not header) NAK ACK MASTER A C C F H SLAVE 1 B D E SLAVE 2 G G 24
References Local Area Networks, Course Slides by D. Mohamed Ashour Bluetooth Technology, Presentation by K. Kumari www.bluetooth.com Bluetooth Piconet Applications, report by J. Mander and D. Picopoulos Advanced Computer Systems, Course slides by E. Ucan, ETH Zurich 25