WiFi, Bluetooth & Satellite: Alternatives to Mobile (lecture 3)

Written by: Jonathan Briggs

February 15, 2007 [4231 views]

Objectives of this session

• Describe the technology
• Help you see what they share
• Help you separate these technologies
• Help you understand their applications

Bluetooth

• Designed for short range communication between devices at 1-2 Mbps
• Normal distance is less than 10 meters (although higher power devices are capable of 100 meters)
• Security is maintained by switching channels many times be second
• Think of it as a replacement for cables
• Low power and low cost
• Ideal add-on technology for mobile phones allowing keyboards, mice, speakerphones, joysticks, monitoring devices, headphones, cameras, gps, printers, car information systems, PCs to connect
• Extensive information on Bluetooth on Wikipedia
• Official Bluetooth site

WiFi (802.11)

• Designed to replace network cables in Local Area Networks, LANs
• 802.11b theoretically delivers 11 Mbps over 100 meters but more realistically 6 Mbps over 35m
• 802.11g delivers 54 Mbps over 75 meters but realistically 25 Mbps over 25m
• 802.11n should deliver 200 Mbps (theoretically 540) over 50 meters
• Each version of WiFi attempts to be backwards compatible with the previous versions
• Roaming (switching from one base station to another while moving) is being investigated but does not work reliably so don’t design applications that need it
• WiFi access is often free on community hotspots or charged via Access control software
• WiFi is excellent for stationary mobility (hotel rooms)
• WiFI data speeds make it excellent for VOIP applications (and are a major threat to cell phone companies)
• WiFI.org site
• Directory of hotspots
• or buy a WiFi finding gadget

What they share

• Both are families of technologies: Bluetooth is Bluetooth 1.2 and Bluetooth 2.0, WiFi is 802.11b, 802.11g and soon 802.11n
• Both are radio technologies designed to link devices
• Both operate on an unregulated part of the radio spectrum 2.45 GHz (shared with microwaves and some cordless phones)

Satellite

• Most satellite activity in the home (such as SKY) is broadcast with thousands of homes receiving the same signal. This is very cost effective.
• Satellites have limited numbers of available two-way channels and these (and the equipment to run them are expensive.
• Satellite phone costs £60 per month plus 50p per minute for calls
• Satellite internet costs £600 for the equipment plus £2000 for 700 MB
• Used when no other form of IP connectivity is possible
• Satellite phone
• Information about the Astra satellite
• Costs of renting a satellite
• Internet via satellite

Think about

• How would airplane and train passengers be provided with WiFi?
• How about a taxi?
• When would you use Bluetooth instead of WiFi?

WiFi supplier for railways
How Emirates provide GSM onboard?

What do you think?

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