What is Bluetooth???
Bluetooth is a universal radio interface in the 2.4 GHz frequency band that enables electronic devices to connect and communicate wirelessly via short-range (10-100 m), ad-hoc networks
Key features
- Peak data rate : 1 Mbps
- Low power : peak tx power <= 20 dBm
- Low cost : target is $5-10 per piece
- Ability to simultaneously handle both voice and data
- Line of sight not required
- 2.4 GHz ISM Open Band
- Globally free available frequency
- 79 MHz of spectrum = 79 channels
- Frequency Hopping & Time Division Duplex (1600 hops/second)
- 10-100 Meter Range
- Class I – 100 meter (300 feet)
- Class II – 20 meter (60 feet)
- Class III – 10 meter (30 feet)
- 1 Mbps Gross Rate
- Simultaneous Voice/Data Capable
History of Bluetooth
- Invented in 1994 by L. M. Ericsson, Sweden
- Named after Harald Blaatand “Bluetooth”, king of Denmark 940-981 A.D.
- Bluetooth SIG founded by Ericsson, IBM, Intel, Nokia and Toshiba in Feb 1998
- More than 1900 members today
- Bluetooth version 1.0 and 1.1 have been released
Bluetooth Vision
- Originally conceived as a cable replacement technology
- Personal Area Network (PAN)
- Ad-hoc networks
- Data/voice access points
- Wireless telematics
Motivation for Bluetooth
Started as a Cable replacement technology
- Ubiquitous Computing environment of intelligent networked devices
- Mobile access to LANs/Internet
- Home Networking
- Automatic Synchronization of data
- Voice applications - hands-free headset
System Challenges
- Work across a diverse set of devices with varying computing Dynamic environment - the number, location and variety of devices changing - connection establishment, routing and service discovery protocols have to take this into consideration
- power and memory
- Unconscious connection establishment
- Size of the implementation should be small. The power consumption should not be more than a fraction of the host device .
System Architecture
The Radio, Baseband and Link Manager are on firmware. The higher layers could be in software. The interface is then through the Host Controller (firmware and driver)
Frequency Hopping
- Divide Frequency band into 1 MHz hop channels
- Radio hops from one channel to another in a pseudo random manner as dictated by a hop sequence
- The instantaneous (hop) bandwidth remains small
- Narrow band interference rejection
Piconets, Masters and Slaves
- In principle each unit is a peer with the same hardware capabilities
- Two or more Bluetooth units that share a channel form a piconet
- One of the participating units is becomes the master (by defn the unit that establishes the piconet).
- Participants may change roles if a slave unit wants to take over as master
- Only one master in a piconet.
- Upto 7 slaves
Link Manager
- LMP (Link Manager Protocol) basically consists of a number of PDUs sent in the baseband payload.
- LMP packets can be recognized by the L_CH field in the baseband header.
- Link Manager handles
- Piconet management (attach/detach slaves, master- slave switch)
- Link Configuration (low power modes, QoS, packet type selection) Security
L2CAP
Concept of L2CAP channels and Channel ids analogous to sockets in TCP/IP
Functions
SDP
Service Discovery Protocol – runs on a client server model. Each device runs only one SDP server and one client may be run for each application.
RFCOMM
Transport protocol providing serial data transfer
Potential Markets
Total of 17 Market Segments
These include:
- Mobile handsets
- Notebooks, laptops
- PDAs,
- Cell Phones
How Mobile Devices Talk to Each Other????
- Maximum of 8 Devices can communicate simultaneously
- Speed: 1MB per second
- Range: 10 meters and 100 with increased power
- 128 bit Encryption
Which Devices Do What
- Phone can be a wireless modem for a notebook computer
- Laptops have a PC Card Antenna that connects to network
- Data from laptop or PDA sent by radio to cell Phone
Applications
- Wireless headsets
- PDA’s
- Cell Phones
- Printers
- Watches
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