11/11/2018 Bluetooth: The Universal Radio Interface for Ad hoc, Short-Range Connectivity CIS 642 Maria Adamou

Overview Introduction Bluetooth Air Interface Architecture Connection Establishment Piconets and Scatternets Power Management Security Competing technologies Issues facing Bluetooth 11/11/2018

Introduction In February 1998 five major telecom and PC companies – Ericsson, Nokia, IBM, Toshiba, and Intel- formed a Special Interest Group (SIG) to create a standard radio interface for short-range connectivity between electronic devices The radio interface was named Bluetooth after a Danish Viking king Harald Bluetooth who united Denmark and Norway during 10th century This group was further expanded in December 1999 with 3Com, Lucent, Microsoft and Motorola Today more than 2000 companies have joined as adopters of the Bluetooth technology 11/11/2018

What is Bluetooth Bluetooth is a universal standard radio interface for short-distance, point-to-multipoint voice and data transfer between portable devices Its nominal link range is from 10 cm to 10 meters but can be extended to 100 meters by increasing the transmission power Printers, desktops, fax machines, cellular phones and virtually any other digital device can be part of the Bluetooth system and form ad hoc groupings that replace cables 11/11/2018

Goals The system must operate globally The system must support peer connectivity, connections are made on an ad hoc basis The connection must support voice and data Ability to withstand interference from other sources The radio transceiver must be small and operate at low power, to fit into small, portable devices, such as mobile phones, headsets, PDAs etc Low cost, short-range 11/11/2018

User Scenarios 3-in-1 phone: At home, portable phone (fixed line charge), when on the move, mobile phone (cellular charge), and when your phone comes within range of another mobile phone a walkie-talkie (no telephony charge) Ultimate Headset: Connect your wireless headset to your mobile phone, mobile computer or any wired connection Interactive Conference in meetings and conferences Automatic Synchronizer: Automatic synchronization of your desktop, PDA, notebook and your mobile phone. Internet Bridge: use of a mobile telephone or cordless modem device that provides modem services to a PC, to enable cordless access for dial-up networking services. LAN access: use of a device that acts as a LAN access point (LAP) providing Bluetooth access services to one or more data terminals. many others... 11/11/2018

Definitions Piconet: a collection of (up to eight) devices connected via Bluetooth technology in an ad hoc fashion. Each piconet is identified by a different frequency hopping sequence and all hosts on the same piconet are synchronized Scatternet: two or more independent and non-synchronized piconets that communicate with each other Master unit: the device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet Slave units: all devices in a piconet that are not the master (up to 7 active units for each master) 11/11/2018

Bluetooth Air Interface License-free, globally available frequency band: Industrial-Scientific-Medical (ISM) band, at 2.45 GHz in most countries in the world Frequency-hopping (FH) spread spectrum to better support low-cost, low-power radio implementations with maximum immunity to interference Channels use a Frequency-Hopping/ Time Division Duplex (TDD) scheme: the channel is divided into slots of 625ms giving 1600hops/sec and subsequent slots are alternately used for transmitting and receiving (TDD) One packet can be transmitted per slot The channel makes use of 79 equally spaced 1-MHz channels (from 2,402 MHz to 2,480 MHz), frequency shift keying (FSK) modulation 1 Mb/s transmission/reception rate 2 power levels: 0dBm for 10 meters or 20dBm (100 meters) 11/11/2018

Packet Definition 72 bits 54 bits 0 - 2745 bits Access code Packet Header Payload 3 4 1 1 1 8 M_ADDR TYPE FLOW ARQN SEQN HEC 72-bit access code unique for the channel, used for packet identification and synchronization, derived from the master Header: 3-bit slave address, packet type, flow control bits, ARQ bit, sequence number, Header-Error-Check fields Payload: 0-2745 bits Multislot packets have been defined: a packet may cover one, three or five slots, sent on a single hop channel 11/11/2018

Links supported Two types of links to support multimedia applications: Synchronous Connection-Oriented (SCO) link Asynchronous Connectionless Link (ACL) SCO links support symmetrical, circuit-switched point-to-point connections typically used for voice Reservation is carried out by the master and the slave ACL links support packet-switched point-to-multipoint connection typically used for bursty data transmission Master units use a polling scheme to control ACL connections: a master-to-slave packet or a POLL packet poll the slave. Collisions are avoided. All SCO and ACL traffic is scheduled by the master 11/11/2018

Architecture 11/11/2018

RF and Baseband Controls the unit’s synchronization and transmission frequency hopping sequence, compresses and puts data into packets, assigning identifiers etc The two link types SCO and ACL are also managed by this layer Takes care of retransmissions and transmission error detection and recovery 11/11/2018

HCI Provides a uniform interface method for accessing the Bluetooth hardware capabilities It contains a command interface to the Baseband controller and link manager and access to the hardware status 11/11/2018

Link Manager Protocol (LMP) Responsible for: Connection set-up Generation, exchange and control of link and encryption keys for Authentication and Encryption Link mode negotiation and set-up, e.g. data or data/voice Sending and receiving of data Management of power modes, power consumption and state of a unit 11/11/2018

Logical Link Control and Adaptation Protocol (L2CAP) L2CAP is an interface between upper layer protocols and baseband and operates in parallel to LMP Multiplexing: L2CAP must support protocol multiplexing, since a number of protocols (e.g. SDP, RFCOMM and TCS Binary) can operate over L2CAP. Segmentation and Reassembly: Data packets exceeding the Maximum Transmission Unit, MTU, must be segmented before being transmitted. This and the reverse functionality, reassemble, is performed by L2CAP. Quality of Service: The establishment of an L2CAP connection allows the exchange of information regarding current Quality of Service for the connection between the two Bluetooth units 11/11/2018

Service Discovery Protocol (SDP) Defines how a Bluetooth client's application shall act to discover available Bluetooth servers' services (like printing, file transfer, synchronization) and their Bluetooth characteristics. Defines how a client can search for a service based on specific attributes without the client knowing anything of the available services. Provides means for the discovery of new services becoming available when the client enters an area where a Bluetooth server is operating. Provides functionality for detecting when a service is no longer available 11/11/2018

Other protocols RFCOMM - Cable replacement protocol: emulates serial port to cover applications that use serial ports of the kind used in PCs and provides transport capabilities for upper level services Telephony Control Protocols TCS BIN: defines the call control signaling for the establishment and release of calls between units TCS AT Commands: transmitting control signals for telephony control Adopted protocols PPP TCP/UDP/IPThe TCP/UDP/IP standards are defined to operate in Bluetooth units allowing them to communicate with other units connected, for instance, to the Internet. WAP 11/11/2018

Connection Establishment When units are not connected they are in STANDBY mode, where they listen to 32 unique (for each unit) wake-up channels, for page or inquiry messages, for about 10ms each Wake-up interval ranges between 0 to 3.84s (usually 1.28s) A unit enters the PAGE or INQUIRY state in which it broadcasts page or inquiry messages If the paging unit knows the identity of the unit to which it wants to connect, it knows the wake-up sequence and transmits the unit’s access code every 1.25ms to 16 different hop frequencies defined for the slave unit (total 10ms period) If the pager does not know the identity of the unit, it broadcasts an inquiry message according to a common inquiry sequence, every 0 to 2.56s 11/11/2018

Connection Establishment 11/11/2018

Piconets and Scatternets Two or more Bluetooth units that share a FH channel form a piconet. At most 1 master and 7 slaves can be in one piconet Any unit can become a master, but by definition the paging unit that establishes the piconet is the master The master identity and clock specify the channel parameters All devices in a piconet are synchronized to the same FH sequence Up to 10 piconets can co-exist with overlapping coverage areas and form a scatternet A unit can be a master in one piconet and a slave in another, or slave in several piconets 11/11/2018

Power Management Frequency-hopping mechanism provides synchronization between master-slaves therefore no dummy packets have to be exchaged A receiver can quickly decide whether a packet is present or not, by the access code and the header and sleep for the rest of the slot Power-save modes: HOLD mode, where no communication is possible for a specified hold time SNIFF mode, where the slave listens only to some slots (depends on the application) PARK mode, where the slave listens to the master’s beacon at large intervals to re-synchronize, does not have a MAC address and does not participate in the traffic 11/11/2018

Modes of operation 11/11/2018

Security As radio signals can be easily intercepted, Bluetooth devices have built-in security to prevent eavesdropping or falsifying the origin of messages (spoofing) The main security features are: a challenge-response routine – for authentication stream cipher – for encryption session key generation – session keys can be exchanged during a connection 11/11/2018

Competing Technologies Infrared Data Association (IrDA) vs Bluetooth IEEE 802.11b vs Bluetooth 11/11/2018

IrDA vs Bluetooth Wireless Standard 11/11/2018 IrDA vs Bluetooth Wireless Standard IrDA already proven standard (50 million units) Bluetooth still in development Data Transfers IrDA up to 4Mbps; 16Mbps( under development) Bluetooth 1Mbps(max) 721Kbps(average) Range IrDA – 3 feet Bluetooth - 30 feet (or more) Line of Sight Required for IrDA, can be advantage in crowded situations Not required for Bluetooth (penetrates walls) Cost of Implementation IrDA - Currently $2 Bluetooth- Initially $20 11/11/2018

IEEE 802.11b vs Bluetooth IEEE 802.11b high rate Bluetooth Market   IEEE 802.11b high rate Bluetooth Market Home, school, and enterprise WLAN Wireless cable Technology 2.4 GHz, ISM, DSSS FHSS, 1,000 hops/sec Data rate 11 Mbps 1 Mbps Power 20 dBm 0 dBm, 20 dBm Range 50 m 1 to 10 m, 50 m Topology 128 devices, CSMA/CA 8 devices, Piconet Security Optional WEP* Encryption, authentication Separate voice channel Optional Yes 11/11/2018

IEEE 802.1b vs Bluetooth The 802.15.2 task group deals with Co-existence and interoperability between Bluetooth and 802.11b Bluetooth offers ubiquity and low price Both technologies can co-exist reasonably well: Bluetooth will function as an aid to a larger-scale network 11/11/2018

Issues facing Bluetooth Implementation Issues Cost Interoperability Performance 11/11/2018

Future of Bluetooth Conservative estimates foresee several hundred million Bluetooth-enabled devices in the next five years By 2004, 75% of all mobile devices will support Bluetooth Communications companies will no longer have to build external cables and PC cards to enable their wireless phones and network cards to interface with computers Bluetooth will provide the "glue" for the merger of wireless and computers. 11/11/2018

References 11/11/2018