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Philip Jansen C. Guarin

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Bluetooth

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The Bluetooth wireless technology uses a digital coding techniquecalled spread spectrum.

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Bluetooth uses FHSS technology.

In US there 79 channels in Bluetooth

technology.The protocol operates in the unlicensed ISM

band at 2.4-2.4835 GHz.

The Bluetooth protocol divides the bandinto 79 channels (each 1 MHz wide) andchanges channels 1600 times per second

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The Bluetooth protocol uses acombination of circuit and packet

switching.

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WLANIEEE 802.11

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 A WLAN is a flexible datacommunication systemimplemented as an extension to oran alternative for a wired local area

network.

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 WLANs transmit and receive dataover the air, minimizing the needfor wired connections.

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Most WLAN systems use spreadspectrum technique (bothfrequency hopping and directsequence).

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U.S. allows the use of channels 1 thru. 11.

U.K. can use channels 1 through 13.

Japan allows the use of all 14 channels.

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 WLANs are being used in healthcare, retail, manufacturing, warehousing, academic and otherarenas.

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These industries have profitedfrom the productivity gains of using handheld terminals andnotebook computers to transmit

real-time information tocentralized hosts for processing.

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Space Systems

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In space stations, which arecontinuously accessible tointerference, spread-spectrummethods have proved effective.

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This is especially true forcommunication satellites.

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all the spread spectrummodulation and demodulationmust be done on the ground toeliminate the complexity of the

system.

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Global

Positioning

System (GPS)

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GPS is a satellite-based navigationsystem developed and operated by the US Department of Defense.

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The idea behind GPS is to transmitspread-spectrum signals that allowrange measurement from anunknown satellite location.

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GPS uses NAVSTAR (NAVigationSatellite Timing And Ranging)

satellites.

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Constellation of 24 Sattelites

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GPS Receiver

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The satellites are identified by thespace vehicle number or thepseudo-random code number.They transmit on two L-band

frequencies: 1.57542 GHz (L1) and1.22760 GHz (L2).

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The DSSS is the same technology used in

GPS satellite navigation systems.

The data stream is combined via an XOR function with a high-speed pseudo-randomnumerical sequence (PRN).

For 1 and 2 Mbps DSSS the PRN code is the11-chip Barker sequence, which is10110111000.

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An Example of GPS DSSS Coding

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A “0” and “1” in GPS DSSS Coding 

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Summary FHSS

DSSS

Chirp SS Hybrid

 Applications

Bluetooth

GPS

 WLAN

Space System

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The End