Cellular Telephone-Why is it cell phone?-How does it work?-Why are some phones free?-Why can’t I buy any phone?-Does my phone know where I am?-How does text messaging work?-New services?Wednesday, October 16, 13Off the Island• Not participating- different than disagreeing• Not Attending• Not doing work• Ways of rewarding (or non rewarding)- Peer Review (10% of grade)• Ask them to leave• To d ay- meet with group- Scouts tell the group members who have missed meetings- designate a vote counter- vote on kicking them out -- I will meet with themWednesday, October 16, 13Cellular TelephoneWhy is it called Cellular?•Cell phone is radio.•Uses towers•Tower arrangement•Cells•10 miles area•3 X 3 milesWednesday, October 16, 13Cellular TelephoneWhy is it called Cellular?•Why not hocka-ma-joka tower•Low power towers•Allows frequency reuse•And batteries smallerWednesday, October 16, 13Cellular TelephoneWhy is it called Cellular?•Frequency reuse•416 duplex channels in cell•Green cells can reuse•Millions of calls in cityWednesday, October 16, 13Cellular TelephoneWhy do I get that weird busy signal?•Cell approach works if population dispersed•Too many people in once area•No more channels available•Try calling between classes•Why not just throw up more towers?•Public reaction•Frequency reuse Wednesday, October 16, 13Cellular TelephoneWhy can’t I use different phones with my service?•ESN – Electronic Serial Number•Programmed into phone at manufacturer•MIN – Mobile ID Number•10 digit phone number•Programmed at activation•SID – System ID Code•Each service has one•Programmed into phoneWednesday, October 16, 13Cellular TelephoneHow does it work when someone calls me?•MTSO – Mobile Telephone Switching office•Connected to each tower with land lines•Connected to regular phone system•One per cityWednesday, October 16, 13Cellular TelephoneHow does it work when someone calls me?1. Turn on phone2. Phone listens for SID (system id code)3. Compares SID to one in phone• Get to non matching later4. Phone transmits request to MTSO5. MTSO picks frequency pair 6. Communicates over control channel7. Talk on 2 way radio8. Monitors channel strengthWednesday, October 16, 13Cellular TelephoneRoaming1. SID phone gets doesn’t match in phone2. Local MTSO contacts home MTSO3. Local MTSO tracks youWednesday, October 16, 13Cellular TelephoneWhat happens when I leave a cell?•Control channel monitors signal strength•Of your signal•And other potential signals•When another signal becomes stronger•Switches to other tower Wednesday, October 16, 13Cellular TelephoneBuying Phone• Comes with• Electronic Serial Number (ESN)• Have to register• Mobile Identification Number (MIN)• System Identification Code (SID)Wednesday, October 16, 13Cellular TelephoneBuying Phone• SIM Chip• Has SID built inWednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?Digital• Can do compression• Much more efficientWednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?Duplex• Talk on one channel• Listen on other channelSimplex• Talk and listen on same channel• OverWednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?Transmission Schemes• Frequency Division Multiple Access (FDMA)• Time Division Multiple Access (TDMA)• Code Division Multiple Access (CDMA)Wednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?FDMA• Channel gets separate frequency• AnalogWednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?TDMA• Each channel into 3 time slots• 6.7 milliseconds each• Digital• GSM uses this• packetizedWednesday, October 16, 13Cellular TelephoneWhat’s the difference between phone systems?CDMA• Spreads out data• Spread spectrum• Sequence code• GPS• 8-10 betterWednesday, October 16, 13Cellular TelephoneWhy won’t my phone work overseas?• GSM is International Standard• Europe, Australia, Africa, Asia• SIM – Subscriber Identification Module• SID on a chip• Different frequency range in US• 900 MHz & 1800MHz in Europe• 1900 MHz (1.9GHz) in US• Dual Band Phones• Can handle bothWednesday, October 16, 13Cellular TelephoneWhy are some phones free?• In US• Carrier involved• Protect network• Protect $$• Certain phones• Nokia phone costs $200• AT&T pays $100• Gives it to you• You will spend more than $100Wednesday, October 16, 13Cellular TelephoneWhy can’t I use any phone?• Certified for network• Unlocked phones• Can work on any network• Maybe?• New FCC rules could change that• Apple and Google could bid.Wednesday, October 16, 13Cellular TelephoneText messaging?• SMS• Short Text Messaging Service• < 160 characters• Uses control channel• For technical features • 1st commercial1992• Computer to phone• Merry Christmas• 8 trillion per yearWednesday, October 16, 13Cellular TelephoneText messaging?• SMS• Billions sent world-wide• Phone companies love them• Voice market saturated• Pay both ways• To send• To receive• Much bigger elsewhere• Different internet experienceWednesday, October 16, 13Cellular TelephoneText messaging?• SMS• Person to Person• Can be sent over computer•AT&T = #@txt.att.net• T-Mobile = #@tmomail.net•Verizon = #@myairmail.com• Business• Premium SMS• Shortcode = 284367• 4castWednesday, October 16, 13Cellular TelephoneWhat is E911?• Enhanced 911• Phase I• All phones have to be able to reach 911• Doesn’t have to have service• Location of signal tower• Phase II• Locate the user within 100 meters• ALI – Automatic Location IdentifierWednesday, October 16, 13Cellular TelephoneWhat is E911?• Enhanced 911• Set deadlines for Phase II• Cell Industry has missed all of them• Hard to do• GPS• Big upgrade requirements• New handsets• Big ecommerce potential• Privacy concernsWednesday, October 16, 13Cellular TelephoneAre cell phones dangerous?• Electromagnetic radiation Wednesday, October 16, 13Cellular TelephoneAre cell phones dangerous?• Electromagnetic radiation• Ionizing• Changes tissue• Changes atoms• Non-Ionizing• No changesWednesday, October 16,