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IT 284 Seminar Unit 9. One-Way Paging Systems The traditional way to handle paging is to have a network of powerful transmitters, all of which transmit.

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Presentation on theme: "IT 284 Seminar Unit 9. One-Way Paging Systems The traditional way to handle paging is to have a network of powerful transmitters, all of which transmit."— Presentation transcript:

1 IT 284 Seminar Unit 9

2 One-Way Paging Systems The traditional way to handle paging is to have a network of powerful transmitters, all of which transmit all of the pages on all of the transmitters Frequencies are reused by using the same frequencies for every transmitter In a voice system, this would result in low capacity, but as messages are typically very short, the transmission times are also short TDMA systems are used for many paging systems Each pager has a unique address called a capcode

3 Spectrum Wireless uses a portion of the total spectrum Bands are regulated for different uses – AM Radio: kHz; FM Radio: 87.5 – 108mHz – Paging: 30-50mHz, mHz, mHz, 900mHz – Cellular: 800mHz (analog, TDMA, CDMA-Verizon) – PCS Cellular: 1900mHz (GSM, CDMA-Sprint)

4 Basic Paging Networks Because all pages are sent from all transmitters, there is no need to know the location of any pager Satellites are often used to transmit pages great distances to local systems, which are relayed using terrestrial transmitters LEO satellites are used for this

5 Wide-Area Paging System Paging Terminal Paging Terminal Paging Terminal Paging Control Center Terrestrial Link Satellite Link City 1 City 2 City N

6 Paging Terminal Overview Callers PSTN Pagers Operators Entering Alphanumeric Messages Wide-Area Applications TNPP Paging Terminal

7 Simulcast (Multicast) Simulcast versus Single transmission – Better in building penetration paging networks simulcast from multiple towers at up to 3500 watts (high power) Cellular type networks transmit from a single tower at 60 watts ERP (low power)

8 Simulcast Transmitter A Transmitter B Link Overlap Area 15 m. sec 10 m. sec ?

9 FLEX (One-way paging) 1600, 3200, 6400 bps Four-minute FLEX protocol cycle Short capcodes: 7 digits Long capcodes: 9 digits

10 ReFLEX (Two-way paging) 1920 Frames per Hour, 128 Frames per 4 Minute Cycle 128 frames per 4 minutes = 1920 frames of 1.76 usable time (seconds) per hour Forward bps, 3200 bps, 1600 bps Reverse bps, 6400 bps, 1600 bps, 800 bps Reverse Channel Number of packets vary with data speed, about 120 bits per frame 800 bps = 11 packets per frame 1600 bps = 23 packets per frame 6400 bps = 96 packets per frame 9600 bps = 116 packets per frame

11 Each pager is assigned to a base frame in a set of 128 frames – these frames repeat every four minutes. 15 of these repetitions occur during an hour. The pager awakes depending on the collapse value assigned to it – each set of pagers have a base frame in which they are synchronized. Page collapse value defines how often the pager awakens. Collapse of 0 = pager scans every frame Collapse of 1 scans every other frame Collapse of 2 scans every 4 th frame Collapse of 3 scans every 8 th frame Collapse of 4 scans every 16 th frame Collapse of 5 scans every 32 nd frame Collapse of 6 scans one out of every 64 th frame Collapse of 7 scans every 128 th frame ReFLEX (Two-way paging continued)

12 ReFLEX (Two-way paging) Narrowband PCS Nationwide frequencies Forward: MHz Reverse: , MHz

13 Current Trends Cellular / PCS – Cell phones – PDA’s – PC cards Location-based Services – Network – Handset SIM Cards – Personal data – Stored minutes (prepay) – Stored value (m-cash) Messaging Technologies – – SMS – IM Telematics – Private vehicles (Onstar) – Commercial Telemetry

14 9.6 to 14.4 Kb/sec115 Kb/sec 384 Kb/sec 384+ Kb/sec (GPRS) (EDGE) (UMTS) 9.6 to 43.2 Kb/sec 9.6 Kb/sec Kb/sec ??? 19.2 Kb/sec 4.8 to 19.2 Kb/sec 9.6 Kb/sec64 Kb/sec 2G2.5G3G 14.4 – 64 Kb/sec 144 Kb/sec 384 Kb/sec cdmaOne (95A-95B) (cdma2000 1XRTT) (cdma2000 EVDV) GSM TDMA CDMA iDEN CDPD Mobitex & DataTAC ReFLEX Cellular Standards & Evolution

15 Devices Faster processors More memory Screens – Bigger – More color depth – Bitmap addressable New user interfaces – Keyboards (built-in / attachable) – Joysticks Device convergence – Hybrid phone/PDA Cameras / MP3 players Virtual machines/browsers

16 Existing Mobile Terminals and Devices Handset Personal Information Manager Personal Communicator Handheld PC Laptop PC Low End High End Voice and SMS DataVoice and Data Data

17 How do Applications run on Devices? Three Paths Processor Device OS Application Processor Device OS VM (App) VM Application Processor Device OS Browser (App) ML Application Native OS  Palm  Symbian  Windows CE  Linux Virtual Machine  Sun J2ME  Qualcomm BREW  AppForge  Syclo Agentry Markup Language

18 Location-based Services 911 locator – Government mandate – Find someone within 50m Advertising – Impulse buying, walking past a store – Discounts Telematics – Mapping and Directions Weather forecasts – Truly local Find things: – Restaurants – Movie theaters – ATMs – Gas Stations Significant Privacy Issues

19 SMS – Short Message Service Integral part of GSM standard – Added to other standards as well Uses control channel of phone – Send/Receive short text messages – Sender pays (if from mobile phone) Phone has " " address – SMTP Interface – Technology Message Length 2- way? GSM 160 bytes Yes TDMA/PDC No* CDMA 256 bytes Yes iDEN 140 bytes Yes

20 SMS Around the World Hugely successful in Europe and Far East 1 Billion phone-to-phone messages / day worldwide – 1.3 Billion messages / day if alerts from Internet  phone are included Avg msgs / month / person – Especially by young people Cheaper than in the US Interchange agreements between carriers

21 SMS Advantages SMS Disadvantages Adopted by young people Simple Fast Inexpensive 2-way (some networks) “Poor person's” Bare bones – No support for fonts, alignment UI - hard to type – Letter “s” requires 4 presses – Wait for next letter No guarantee of delivery Not suitable for interactive conversations Interoperability in the US – Recently addressed

22 The Convergence - Multichannel Universal NET Access PDA Set Top Box Web Pad Games Console WID Messaging Contacts Agenda Secure personal data Fax Corporate data Inter/Intra/Extra NET WAP Phone Work PC Home PC


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