Ford Amateur Radio League February 21 2013 Introduction Bluetooth is a wireless technology standard for exchanging data over short distances using shortwavelength radio transmissions in the ID: 789845
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Slide1
Bluetooth Technology
David TreharneFord Amateur Radio LeagueFebruary 21, 2013
Slide2Introduction
Bluetooth is a
wireless
technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the
ISM
band from 2400–2480 MHz) from fixed and mobile devices, creating
personal area networks
(PANs) with high levels of security. Created by telecom vendor
Ericsson
in 1994,
[2]
it was originally conceived as a wireless alternative to
RS-232
data cables. It can connect several devices, overcoming problems of synchronization
Slide3Who was Harold Bluetooth?
Harald "Bluetooth"
Gormsson
(Old Norse:
Haraldr
blátǫnn Gormsson, Danish: Harald Blåtand Gormsen) (probably born c. 935) was the son of King Gorm the Old and of Thyra Dannebod. He died in 985 or 986 having ruled as King of Denmark from c. 958 and King of Norway for a few years probably around 970. Some sources state that his son Sweyn Forkbeard forcibly deposed him as King.The Bluetooth communications protocol in these devices is named after this king, ostensibly due to his abilities to make diverse factions communicate with each other. According to legend, he gained the nickname "Bluetooth" due to his love of blueberries, which stained his teeth. The Bluetooth logo is a bind rune merging the Younger Futhark runes (Hagall) (ᚼ) and (Bjarkan) (ᛒ), Harald's initials.
Slide4Frequencies of Operation
Bluetooth uses a radio technology called
frequency-hopping spread spectrum
, which chops up the data being sent and transmits chunks of it on up to 79 bands (1 MHz each; centered from 2402 to 2480 MHz) in the range 2,400–2,483.5 MHz (allowing for guard bands). This range is in the globally unlicensed Industrial, Scientific and Medical (
ISM
) 2.4 GHz short-range radio frequency band. It usually performs 800 hops per second, with
Adaptive Frequency-Hopping (AFH) enabledIn the US, FCC part 15 on unlicensed system in the 900 MHz and 2.4 GHz bands permits more power than non-spread spectrum systems. Both frequency hopping and direct sequence systems can transmit at 1 Watt. The limit is increased from 1 milliwatt to 1 watt or a thousand times increase.
Slide5Antennas
Savvi Bluetooth 8x3 antenna
BT
Antenna 2.4—2.5 GHz
Peak Gain 1.39
dBi
Average Efficiency 78%VSWR Match 2.0:1 maxFeed Point Impedance 50 ohms unbalancedPower Handling .5 Watt cwPolarization LinearIsolated magnetic dipole
Slide6Polar Plots
Antenna is directional in one direction, pretty isotropic in others. Designed for the top of a cell phone to be strong toward a headset.
Slide7Spread Spectrum
Bluetooth can connect up to eight devices
simultaneously in a 10 m radius.
Bluetooth uses a technique called
spread-spectrum frequency hopping
that makes it rare for more than one device to be transmitting on the same frequency at the same time. In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the
radio spectrum. One of the challenges of frequency-hopping systems is to synchronize the transmitter and receiver. One approach is to have a guarantee that the transmitter will use all the channels in a fixed period of time. The receiver can then find the transmitter by picking a random channel and listening for valid data on that channel. The transmitter's data is identified by a special sequence of data that is unlikely to occur over the segment of data for this channel and the segment can have a checksum for integrity and further identification. The transmitter and receiver can use fixed tables of channel sequences so that once synchronized they can maintain communication by following the table. On each channel segment, the transmitter can send its current location in the table.
Slide8Speed of Data
The older Bluetooth 1.0 standard has a maximum transfer speed of 1 megabit per second (Mbps), while Bluetooth 2.0 can manage up to 3 Mbps
. Bluetooth 2.0 is backward-compatible with 1.0 devices.
Net throughput:
Bluetooth can send data at more than 64 kilobits per second (Kbps) in a full-duplex link -- a rate high enough to support several voice conversations. If a particular use calls for a half-duplex link -- connecting to a
computer printer
, for example -- Bluetooth can transmit up to 721 Kbps in one direction, with 57.6 Kbps in the other. If the use calls for the same speed in both directions, Bluetooth can establish a link with 432.6-Kbps capacity in each direction.
Slide9Typical Applications
Headsets for phonesStreaming audio to a vehicle stereo or home speaker system
PC mouse, keyboard, and printer
Replacment
for RS-232 (its original intent) for PCs, GPS units, and medical devices
Replacement for
infared controls, since it does not have to be strict line of sight.Game controllers, such as Nintendo Wii“Man Overboard” alarm when the device leaves a defined area.
Slide10Protocol
Bluetooth has a wide variety of protocols available. Maybe too many, since it is not possible for all devices to talk to one another.
L2CAP
The
Logical Link Control and Adaptation Protocol
(L2CAP)
In Basic mode, L2CAP provides packets with a payload configurable up to 64 kB, with 672 bytes as the default MTU, and 48 bytes as the minimum mandatory supported MTU.In Retransmission and Flow Control modes, L2CAP can be configured either for isochronous data or reliable data per channel by performing retransmissions and CRC checks.Streaming Mode (SM): This is a very simple mode, with no retransmission or flow control. SDP The Service Discovery Protocol (SDP) allows a device to discover services offered by other devicesRFCOMM: Radio Frequency Communications is a cable replacement protocol used to create a virtual serial data stream. RFCOMM provides for binary data transport and emulates EIA-232 (formerly RS-232) control signals over the Bluetooth baseband layer, i.e. it is a serial port emulationAnd more!
Slide11Security
Original versions could be hacked within 24 hours.Newer versions in 2.0 and beyond improve that.Pairing also prevents unknown devices from connecting to systems
There has been problems, and they have been addressed by newer devices.
Slide12What is Next?
Bluetooth had a slow start, but is now gaining great popularity.Protocols were a problem, dropouts and directivity of the radio signal, body shielding (2.4 GHz is microwave band)
Faster speeds are coming available, capable of video and higher data transmissions.
Medical devices worn outside or inside the body can send data to a smart phone to record data and notify personnel of an emergency.
Canada is experimenting using Bluetooth from cars to the roadside to gain information on vehicle congestion.
Will not replace
WiFi, but is great for local communication.
Slide13Credits and Sources
http://en.wikipedia.org/wiki/Bluetoothhttp://www.bluetooth.com/Pages/Bluetooth-Home.aspx
http://www.howstuffworks.com/bluetooth.htm
https://www.bluetooth.org/apps/content/
http://
en.wikipedia.org/wiki/Harald_Bluetooth
http://www.ethertronics.com/products/bluetooth/http://www.bluetooth.com/Pages/Product-Directory.aspx