Technologies for Mobile Environments
What ismobility?
- Physical mobility
- Service mobility
- Session mobility
Data communicationcross table
|
? |
Wired |
Wireless |
|
Mobile |
PDA without wireless interface |
Cellular phone, smart phone with UMTS capability |
|
Stationary (non-mobile) |
Desktop computer with LAN-connection |
PC/Notebook with WiFi connection or WiMax |
Mobile technologiesfor business application
Mobile computerconvenience
- Smaller
- More aesthetical(beautiful)
- Cooler
- Simpler to use
- Cheaper
Mobile specialchallenges
- Usability issues(small display, toilsome data input no standardizedinterface)
- Limited battery capacity
- Great heterogeneity(too many kinds of mobile phones) of mobiledevices
- Wireless data communication (legal requirements, interferenceproblems, low bandwidth, health problem….)
- Security issues(shoulder surfing, loss of mobile device, trackingof user’s whereabouts)
Mobile technologyapplications’ list
- Mobile commerce
- Mobile business
- Mobile gaming
- Mobile banking
- Mobile advertising
- Mobile payment
- Mobile health
- Mobile learning
- Mobile music
- Mobile messaging
- Mobile parking
- …………
Basics of radiotechnology
- Frequency & wavelength(notice unit change whencalculate)
- Attenuation(decrease, with increasing frequency the radio signal issubject to stronger attenuation)
- Obstructions(Obstacle)
Radio wavepropagation
- Propagation in free space is linear
- Power density in vacuum decreases proportional to 1/d^2 withdistance d between sender and receiver
- Even stronger decreasing if radio waves travel throughnon-vacuum(something there) space
Propagation ranges ofradio waves transmission range
- Transmission range(only range where communication is possible)
- Detection range(detection of the signal possible, nocommunication)
- Interference range(neither communication nor detection possible,signal adds to the background noise)
Signalpropagation
- Attenuation (depends on frequency)
- Shadowing
- Reflection at large objects
- Scattering at small objects
- Diffraction at edges
- Refraction depending on density of medium
Note:
Difference: shadowing means that you are in the building andsignal can not get into the building, so that you find yourself areout of signal. Maybe in the government secret building you can notget signal so that you can not give a call. Some signals areabsorbed and others are reflected. Reflection means when the signalmeets the building it changes its path, if you are standing outsidethe building, maybe you can get signal which is not originally sentto you. The left three ones are easy, just like the light.
Multipathpropagation
Radio signal is reflected by large obstacles. These reflectedsignals arrive later than the “original” signals which travelled ondirect line between sender and receiver.