Slide 1: Bluetooth 1 Bluetooth Technology Farinaz Edalat, Ganesh Gopal, Saswat Misra, Deepti Rao
April 26, 2001 Bluetooth : Bluetooth 2 Bluetooth A new global standard for data and voice
Goodbye Cables ! Ultimate Headset : Bluetooth 3 Ultimate Headset Cordless Computer : Bluetooth 4 Cordless Computer Automatic Synchronization : Bluetooth 5 Automatic Synchronization In the Office At Home Bluetooth Specifications : Bluetooth 6 Bluetooth Specifications Bluetooth Protocol Stack : Bluetooth 7 Bluetooth Protocol Stack Composed of protocols to allow Bluetooth devices to locate each other and to create, configure and manage both physical and logical links that allow higher layer protocols and applications to pass data through these transport protocols RF Baseband Audio Link Manager L2CAP SDP RFCOMM Applications Transport Protocol Group Transport Protocol Group (contd.) : Bluetooth 8 Transport Protocol Group (contd.) Radio Frequency (RF)
Sending and receiving modulated bit streams
Defines the timing, framing
Flow control on the link.
Managing the connection states.
Enforcing Fairness among slaves.
Logical Link Control &Adaptation Protocol
Handles multiplexing of higher level protocols
Segmentation & reassembly of large packets
Device discovery & QoS Middleware Protocol Group : Bluetooth 9 Middleware Protocol Group Middleware Protocol Group RF Baseband Audio Link Manager L2CAP SDP RFCOMM Applications Middleware Protocol Group Additional transport protocols to allow existing and new applications to operate over Bluetooth. Packet based telephony control signaling protocol also present. Also includes Service Discovery Protocol. Middleware Protocol Group (contd.) : Bluetooth 10 Middleware Protocol Group (contd.) Service Discovery Protocol (SDP)
Means for applications to discover device info, services and its characteristics.
Network Protocols for packet data communication, routing
Cable replacement protocol, emulation of serial ports over wireless network Application Group : Bluetooth 11 Application Group Application Group RF Baseband Audio Link Manager L2CAP SDP RFCOMM Applications Consists of Bluetooth aware as well as un-aware applications. Master - Slave : Bluetooth 12 Master - Slave Master
Device in Piconet whose clock and hopping sequence are used to synchronize all other devices (slaves) in the Piconet.
It also carries out Paging procedure and also Connection Establishment.
Units within the piconet that are syncronized to the master via its clock and hopping sequence.
After connetion establishment, Slaves are assigned a temporary 3 bit member address to reduce the no. of addresing bits required Piconets : Bluetooth 13 Piconets Point to Point Link
Master - slave relationship
Bluetooth devices can function as masters or slaves
It is the network formed by a Master and one or more slaves (max 7).
Each piconet is defined by a different hopping channel to which users synchronize to.
Each piconet has max capacity (1 Mbps).
Hopping pattern is determined by the master. s s s m Piconet Structure : Bluetooth 14 Piconet Structure Physical Link Types : Bluetooth 15 Physical Link Types Synchronous Connection Oriented (SCO)
Point to Point Full Duplex between Master & Slave
Established once by master & kept alive till released by Master
Typically used for Voice connection ( to guarantee continuity )
Master reserves slots used for SCO link on the channel to preserve time sensitive information
Asynchronous Connection Link (ACL)
It is a momentary link between master and slave.
No slots are reserved.
It is a Point to Multipoint connection.
Symmetric & Asymmetric links possible Packet Types : Bluetooth 16 Packet Types Control
DM1 Voice data HV1
DH5 Access Code Header Payload Packet Structure : Bluetooth 17 Packet Structure 72 bits 54 bits 0 - 2744 bits Data Voice CRC No CRC
No retries header ARQ FEC (optional) FEC (optional) Access Code Header Payload Access Code : Bluetooth 18 Access Code Purpose
DC offset compensation
Channel Access Code (CAC)
Identifies a piconet.
Device Access Code (DAC)
Used for signalling procedures like paging and response paging.
Inquiry Access Code (IAC)
General IAC is common to all devices, Dedicated IAC is for a dedicated group of Bluetooth devices that share a common characteristic. Packet Header : Bluetooth 19 Packet Header Addressing ( 3 bits )
Packet type (4 bits )
Flow Control ( 1 bit )
Sequencing ( 1 bit )
HEC ( 8 bit ) For filtering retransmitted packets Verify header integrity Connection State Machine : Bluetooth 20 Connection State Machine Standby Inquiry Page Connected Transmit data Park Hold Sniff Connection State Machine (contd.) : Bluetooth 21 Connection State Machine (contd.) Inquiry Scan
A device that wants to be discovered will periodically enter this mode and listen for inquiry packets.
Device sends an Inquiry packet addressed to GIAC or DIAC
Transmission is repeated on the inquiry hop sequence of frequencies.
When an inquiry message is received in the inquiry scan state, a response packet (FHS) containing the responding device address must be sent after a random number of slots. Connection State Machine (contd.) : Bluetooth 22 Connection State Machine (contd.) Inquiry Response Connection State Machine (contd.) : Bluetooth 23 Connection State Machine (contd.) Page
The master uses the clock information, about the slave to be paged, to determine where in the hop sequence, the slave might be listening in the page scan mode.
The master sends a page message
The page scan substate can be entered by the slave from the standby state or the connection state. It listens to packets addressed to its DAC.
On receiving the page message, the slave enters the slave page response substate. It sends back a page response consisting of its ID packet which contains its DAC, at the frequency for the next slot from the one in which page message was received. Power Control Modes : Bluetooth 24 Power Control Modes Sniff Mode
This is a low power mode in which the listening activity of the slave is reduced.
In the sniff mode, the slave listens for transmissions only at fixed intervals Tsniff, at the offset slot Dsniff for Nsniff times. These parameters are given by the LMP in the master when it issues the SNIFF command to the slave.
Slave temporarily (for Thold sec) does not support ACL packets on the channel (possible SCO links will still be supported).
By this capacity can be made free to do other things like scanning, paging, inquiring, or attending another piconet.
The slave unit keeps its active member address (AM_ADDR). Power Control Modes (contd.) : Bluetooth 25 Power Control Modes (contd.) Park Mode
This is a very low power mode with very little activity.
The slave however, stays synchronized to the channel.
The parked slaves regularly listen for beacon signals at intervals decided by the beacon structure communicated to the slave during the start of parking.
The parked slave has to be informed about a transmission in a beacon channel which is supported by the master to keep parked slaves in synchronization and send them any other information.
Any message to be sent to a parked member are sent over the broadcast channel.
It also helps the master to have more than seven slaves. Security : Bluetooth 26 Security Security Measures
Limited/Restricted Access to authorized users.
Both Link Level Encryption & Authentication.
Personal Identification Numbers (PIN) for device access.
Long encryption keys are used (128 bit keys).
These keys are not transmitted over wireless. Other parameters are transmitted over wireless which in combination with certain information known to the device, can generate the keys.
Further encryption can be done at the application layer.
Authentication Key(128 bits)-Private
Encryption Key(8-128 bits)-Private
Random Number Frequency Hop Spread-Spectrum : Bluetooth 27 Frequency Hop Spread-Spectrum Bluetooth channel is represented by a pseudo random hopping sequence through the entire 79 RF frequencies
Nominal hop rate of 1600 hops per second
Channel Spacing is 1 MHz Time-Division Duplex Scheme : Bluetooth 28 Time-Division Duplex Scheme Bluetooth devices use a Time-Division Duplex (TDD) scheme
Channel is divided into consecutive slots (each 625 s)
One packet can be transmitted per slot
Subsequent slots are alternatively used for transmitting and receiving
Strict alternation of slots b/t the master and the slaves
Master can send packets to a slave only in EVEN slots
Slave can send packets to the master only in the ODD slots Performance Analysis of Link(Reference: Pedersen and Eggers, VTC 2000) : Bluetooth 29 Performance Analysis of Link(Reference: Pedersen and Eggers, VTC 2000) Results collected from “real” Bluetooth link
two notebook PC’s
PC cards from Digianswer
full power devices Pt = 20 dBm
stationary master and slave
- slave moves in circle R = 3 at 1.5 RPM Test Parameters : Bluetooth 30 Test Parameters Testing done from a master to a single slave
No major sources of interference
Tests used DH5 packet only 8-bit HEC 16-bit payload CRC Pictures : Bluetooth 31 Pictures Results: Indoor : Bluetooth 32 Results: Indoor Results: Outdoor : Bluetooth 33 Results: Outdoor How reliable are Bluetooth Devices ? : Bluetooth 34 How reliable are Bluetooth Devices ? Indoor:
Within 10 meters
Within 25 meters, with LOS
Concrete, Glass….? Outdoor:
Within 150-220 meters with LOS
More than 220 meters Analytic Analysis of Link(Reference: A.Kumar and A.Karnik, ICPWC 2000) : Bluetooth 35 Analytic Analysis of Link(Reference: A.Kumar and A.Karnik, ICPWC 2000) Goal: Find a bound on the BER as a function of network size The Problem : Bluetooth 36 The Problem Occasionally, two piconets will use overlapping frequencies Assumptions and Parameters : Bluetooth 37 Assumptions and Parameters “Open” (LOS) indoor room; circular with radius R
Received power is a random variable
mean received power falls off as d2
for fixed d, signal fading is Rician with K = 6dB
Interference from other Bluetooth devices only
ignore 802.11, microwaves
Time offset of each Piconet is uniform [0,T] SIR calculation : Bluetooth 38 SIR calculation For a reference piconet
Ignore noise power
2.5 nW for device within Bluetooth specs operating at 1Mbps with BER < .001 f(t) because the interfering and receiving devices within a piconet change with time SIR Calculation (cont.) : Bluetooth 39 SIR Calculation (cont.) Probability of Outage: SIR Calculation (cont.) : Bluetooth 40 SIR Calculation (cont.) Evaluation of Pout is complicated and requires numerical techniques (see reference)
Some results (for R = 5m; uniform distribution)
In general Pout increases linearly with M
Pout (M-1) / Nf Other Technologies : Bluetooth 41 Other Technologies IrDA
Infrared, LOS, serial data comm.
Point to point
Intended for Data Communication
Simple to configure and use
Both devices must be stationary, for synchronization
Can not penetrate solid objects IrDA vs Bluetooth : Bluetooth 42 IrDA vs Bluetooth Bluetooth Advantages
Point to Multipoint
Data & Voice
Easier Synchronization due to omnidirectional and no LOS requirement
Devices can be mobile
Range 10 m
Currently 16 Mbps
Ample security and very less interference
Already ubiquitous & Low cost Bluetooth: Today and Tomorrow… : Bluetooth 43 Bluetooth: Today and Tomorrow… First market-ready product shipped November 2000
Digital headset produced by GN Netcom $300 Bluetooth: Today and Tomorrow.. (cont.) : Bluetooth 44 Bluetooth: Today and Tomorrow.. (cont.) Will Bluetooth become a household name? Conclusions : Bluetooth 45 Conclusions A new global standard for data and voice
Low Power, Low range, Low Cost network devices
Delivers Automatic synchronicity between devices
Master-Slave relationship can be adjusted dynamically for optimal resource allocation and utilization
Adaptive, closed loop transmit power control can be implemented to further reduce unnecessary power usage References : Bluetooth 46 References  Bluetooth Consortium :
 Bluetooth Tutorial :
 G.F.Pedersen, P.Eggers, “Initial Investigation of the Bluetooth Link”, VTC, pp 64 – 70
 J.C.Haartsen, et al, “Bluetooth – A New Low-Power Radio Internface Providing Short-Range Connectivity”, IEEE Proc. , Vol 88, No.10, Oct 2000
 Min-Chul Ju, et al. , “Channel Estimation and DC-Offset Compensation Schemes for Frequency Hopped Bluetooth Networks”, IEEE Communications Letters, Vol 5, No.1, Jan 2001