ECE 5600 Introduction to Computer Networking Lecture 19

ECE 5600 Introduction to Computer Networking Lecture 19 – Bluetooth Prof. Rose Qingyang Hu Electrical and Computer Engineering Department Utah State University

READING Book: Andrew S. Tanenbaum, Computer Networks, Fifth Edition, Prentice Hall Chapters 4. 6

BLUETOOTH v v v v Introduction Architecture Applications Protocol stack Radio layer Link layers Frame structure

INTRODUCTION v Named after a Danish king v Intended as a replacement for shortrange cables v Inexpensive v Flexible v Robust

BLUETOOTH CHARACTERISTICS Unlicensed 2. 4 GHz radio band § ISM (industrial, scientific, medical) band - Available worldwide § Also used by Microwave ovens, 802. 11, Home. RF… Gross data rate of 1 Mbit/s Basic 10 m range extended to 100 m with amplifiers TDMA - TDD - Frequency hopping Mixed voice / data paths Encryption Low power Low cost Extremely small

PICONET v Only one master v Dynamically selected v Roles can be switched v Up to 7 active slaves v Active piconet v Up to 255 parked slaves v Can be reactivated quickly v No central network structure v “Ad-hoc” network

SCATTERNET v Interconnected piconets v One master piconet v Few devices shared between piconets v No central network structure v “Ad-hoc” network

SCATTERNET APPLICATIONS v Data exchange across piconets

BLUETOOTH PROTOCOL STACK Audio applications can bypass L 2 CAP once connections are established Application Middleware Supports serial data protocols such as virtual COM ports or LAN via PPP. Profiles (applications) Audio RFcomm ……… L 2 CAP Data Link LMP Baseband Physical Media Access Control and Framing Radio Service discovery Logical Link Control Adaptation Protocol. Frames variable length messages and provides reliability. Shields upper layers from transmission details e. g. Segmentation/Reassembly, multiplexing, Qo. S (Link Management Protocol): establish logical channels, Power management, Pairing, Authentication, Qo. S.

BLUETOOTH RADIO 1 v 2. 4 GHz ISM Frequency Band v FHSS (Frequency hopping spread spectrum) using 79 channels, 1 MHz bands. v Modulated using FSK 1 bit/ μsec v Interferes with 802. 11 v 1 Mbps raw data rate. v 625μsec slots v Frames may be 1, 3 or 5 slots long v Master transmissions start in even slots, slaves start in odd slots.

BLUETOOTH RADIO 2 v Basic 10 m range (with 0 d. Bm radio) v Extended 100 m range (20 d. Bm) v Power classes v Class 1 v Maximum output power: 100 m. W (20 d. Bm) v Minimum output power: 1 m. W (0 d. Bm) v Class 2 v Maximum output power: 2. 5 m. W (4 d. Bm) v Minimum output power: 0. 25 m. W (-6 d. Bm) v Class 3 v Maximum output power: 1 m. W (0 d. Bm) v Power control required for high powered Bluetooth devices to minimize interference

BASEBAND CONTROLLER v Baseband: baseband protocols and low level link routines v Link Manager: Link Layer messages for setup and link control

BLUETOOTH BASEBAND 1 v Frame Format (625 μsec, 1 bit per μsec) Stabilization (250 usec) (Master’s) Access Code (72 -bits) 3 Headers (54 bits) Payload (240 bits*) *can be up to 2744 bits if 5 slots are used. v Frame Header (repeated 3 times) Address (3 bits) Type (4 bits) Flow ACK SEQ CRC (8 bits)

FRAME HEADER FIELDS v Address: 3 bit member address defines active members of a piconet v Data Type: Defines various types of packets and their length. Allows non-addressed slaves to determine when they can transmit. v Flow: for flow control. Asserted by a slave when its buffer is full. v ACK: ACK/NAK field v SEQ: 1 sequence number for retransmission in stop and wait. v CRC: header error check, if an error is found, the entire packetm s discarded

BLUETOOTH BASEBAND 2 v TDMA – Time division multiple access v TDD – Time division duplex

BLUETOOTH LINKS v All data transmitted over Master/Slave Links v Link Types v ACL – Asynchronous Connection-Less. Used for file transfer, etc. v SCO – Synchronous Connection-Oriented. Used for real-time data such as audio/telephony

ACL LINKS v Best Effort – No guarantee of success. v Automatic Repeat Request (ARQ) causes frame to be retried automatically until acknowledged or timeout occurs. v Frames may be 1, 3 or 5 slots long. v A slave may have only 1 ACL Link at a time.

SCO LINKS v Single slot frames (240 data bits) only. v 80 bits of data per frame (64 kbps max). v Real-time, no retries are ever attempted. v Can have 1, 2 or 3 simultaneous SCO links. v Error Correction v 1 SCO link: 80 bits are repeated 3 times. v 2 SCO links: 15 -bit FEC code words encode 10 bits. v 3 SCO links: No error correction.

SCO VS ACL v Synchronous Connection-Oriented (SCO) Link v Circuit switching v Symmetric, synchronous services v Slot reservation at fixed intervals v Asynchronous Connection-Less (ACL) Link v Packet switching v (A)symmetric, asynchronous services v Polling access scheme

SCO TRANSMISSION