Wireless Networks

Lecture 39
Bluetooth/Wireless Personal Area Networks (WPAN)
Dr. Ghalib A. Shah

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Outlines
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Bluetooth introduction
Technical features
Access technique
Bluetooth topology/scenario
Specifications
Architecture
Core Protocols
Packet format
Link connections
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Last Lecture
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Security primitives in TinySec
Encryption Schemes
Keying mechanism
WMSN
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Architecture
Applications
Advantages
Design Considerations
Protocols

 WSAN
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Motivation

WSN vs WSAN
Architecture
Issues
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What is Bluetooth?
 “Bluetooth wireless technology is
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an open specification for a
low-cost, low-power, short-range radio technology
for ad-hoc wireless communication of
voice and data anywhere in the world.”

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Ultimate Headset

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Cordless Computer

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Bluetooth Application Areas
 Data and voice access points
► Real-time voice and data transmissions

 Cable replacement
► Eliminates need for numerous cable attachments for
connection

 Ad hoc networking
► Device with Bluetooth radio can establish connection
with another when in range

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Overview of Bluetooth History
 What is Bluetooth?
► Bluetooth is a short-range wireless communications
technology.

 Why this name?
► It was taken from the 10th century Danish King Harald
Blatand who unified Denmark and Norway.

 When does it appear?
► 1994 – Ericsson study on a wireless technology to link
mobile phones & accessories.
► 5 companies joined to form the Bluetooth Special
Interest Group (SIG) in 1998.

► First specification released in J uly 1999.
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Technical features
Conne ction Type

Spread Spectrum (Frequency Hopping)
& Time Division Duplex (1600
hops/sec)

S pe ctrum

2.4 GHz ISM Open Band (79 MHz of
spectrum =79 channels)

Modulation

Gaussian Frequency Shift Keying

Trans m is s ion Powe r

1 mw – 100 mw

Data R ate

1 Mbps

R ange


30 ft

S upporte d S tations

8 devices

Data S e curity –Authe ntication 
Ke y

128 bit key

Data S e curity –Encryption Ke y

8-128 bits (configurable)

Module  s iz e

9 x 9 mm

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Time-Division Duplex Scheme
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Channel is divided into consecutive slots (each 625 s)

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One packet can be transmitted per slot


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Subsequent slots are alternatively used for transmitting and
receiving
► Strict alternation of slots between 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

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Radio Specification
 Classes of transmitters
► Class 1: Outputs 100 mW for maximum range
• Power control mandatory
• Provides greatest distance

► Class 2: Outputs 2.4 mW at maximum
• Power control optional

► Class 3: Nominal output is 1 mW
• Lowest power

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Typical Bluetooth Scenario
 Bluetooth will support wireless point-to-point
and point-to-multipoint (broadcast) between

devices in a piconet.
 Point to Point Link

m
► Master - slave relationship
► Bluetooth devices can function as masters or slaves

s

 Piconet
► 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)
s

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m

s

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Piconet Structure
Master
Active Slave
Parked Slave

Standby

All devices in piconet hop together.
Master’s ID and master’s clock determines frequency hopping 
sequence & phase.
Hopping sequence shared with all devices on piconet
Bluetooth devices use time division duplex (TDD)
Access technique is TDMA
FH-TDD-TDMA

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Ad-hoc Network – the Scatternet
 Inter-piconet
communication
 Up to 10 piconets in a
scatternet
 Multiple piconets can
operate within same
physical space
 This is an ad-hoc, peer to
peer (P2P) network

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Bluetooth Standards Documents
 Core specifications
► Details of various layers of Bluetooth protocol 

architecture
► Bluetooth is a layered protocol architecture
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Core protocols
Cable replacement and telephony control protocols
Adopted protocols

 Profile specifications
► Use of Bluetooth technology to support various 
applications
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Profiles
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Generic Access Profile
Service Discovery Application Profile
Cordless Telephony Profile
Intercom Profile
Serial Port Profile
Headset Profile
Dial-up Networking Profile
Fax Profile
LAN Access Profile
Generic Object Exchange Profile
Object Push Profile
File Transfer Profile
Synchronization Profile
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Architecture

Core protocols
Radio
Baseband
Link manager protocol
(LMP)
Logical link control and
adaptation protocol
(L2CAP)
Service discovery
protocol (SDP)
ble replacement protocol

RFCOMM
lephony control protocol
Telephony control specification – binary (TCS BIN)
opted protocols
PPP
TCP/UDP/IP
OBEX
WAE/WAP

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Core Protocols
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Radio:
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Baseband:
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It is transactional protocol between two link management entities used to setup
properties of BT link. For example a device may authenticate each other, may
learn each others features (SCO/ACL links, size of packet, power consumption
mode).


Host Constroller Interface (HCI):
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Defines procedure to communicate with other BT devices like formation of
piconets, links in a piconet (ACL or SCO), and access of transmit resources in
a piconet etc.

Link Manager protocol (LMP):
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defines technical characteristics of BT radios.
For example licence-free ISM band 2.4 GHz, FHSS at 1600 Hops/sec, 1 MHz
channel bandwidth, GMSK modulation, tx power from 100 mw to 1 mw, raw
transmission rate of 1 Mbps and so on.

it is not a protocol rather an interface through which BT devices access the
lower layers of BT protocol stack. A device may pass and receive data
destined to or coming from another BT device, execute inquiries, request
authentication and so on.

Logical Link Control and Adaptation protocol (L2CAP):
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shields the specifics of BT lower layers and provides a packet interface to
higher layers.


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Bluetooth protocols
 Service Discovery Protocol (SDP)
► Defines a service record format
• Information about services provided by attribute s
• Attributes composed of an ID (name) and a value
• IDs may be universally unique identifiers (UUIDs)

► Defines an inquiry/response protocol for discovering
services
• Searching for and browsing services

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Bluetooth protocols
 RFCOMM (based on GSM TS07.10)
► emulates a serial-port to support a large base of legacy (serialport-based) applications
► allows multiple “ports” over a single physical channel between
two devices

 Telephony Control Protocol Spec (TCS)
► call control (setup & release)
► group management for gateway serving multiple devices

 Legacy protocol reuse
► reuse existing protocols, e.g., IrDA’s OBEX, or WAP for

interacting with applications on phones
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Baseband
 Addressing
► Blue to o th de vic e  addre s s  (BD_ADDR)
– 48 bit IEEE MAC address

► Ac tive  Me mbe r addre s s  (AM_ADDR)
– 3 bits active slave address
– all zero broadcast address

► Parke d Me mbe r addre s s  (PM_ADDR)
– 8 bit parked slave address

 This MAC address is split into three parts
► The  No n­s ig nific ant Addre s s  Part (NAP)
– Used for encryption seed

► The  Uppe r Addre s s  part (UAP)

– Used for error correction seed initialization & FH sequence generation

► The  Lo we r Addre s s  Part (LAP)

– Used for FH sequence generation

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Packet Structure
72 bits

Access
Code

54 bits

Header

Voice

No CRC
FEC (optional)

0 - 2744 bits

Payload

header

Data

CRC

ARQ
FEC (optional)

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Types of Access Codes
 Channel access code (CAC) – identifies a piconet
 Device access code (DAC) – used for paging and 
subsequent responses
 Inquiry access code (IAC) – used for inquiry 
purposes

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Inquiry Procedure
 Potential master identifies devices in range that wish to 
participate
► Transmits ID packet with inquiry access code  (IAC)
► Occurs in Inquiry state

 Device receives inquiry
► Enter Inquiry Response state
► Returns FHS packet with address and timing information
► Moves to page scan state

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Page Procedure
 Master uses devices address to calculate a page 
frequency­hopping sequence
 Master pages with ID packet and device access code 

(DAC) of specific slave
 Slave responds with DAC ID packet
 Master responds with its FHS packet
 Slave confirms receipt with DAC ID
 Slaves moves to Connection state 

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