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 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

Spectrum

• Wireless uses a portion of the total spectrum• Bands are regulated for different uses

– AM Radio: 520-1710kHz; FM Radio: 87.5 – 108mHz– Paging: 30-50mHz, 150-170mHz, 450-570mHz, 900mHz– Cellular: 800mHz (analog, TDMA, CDMA-Verizon)– PCS Cellular: 1900mHz (GSM, CDMA-Sprint)

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

Wide-Area Paging System

PSTN

Base stationTelephone

PagingTerminal

PagingTerminal

PagingTerminal

Base station

Base station

pager

Satellite

Paging Control Center

Terrestrial Link

Terrestrial Link

Satellite Link

City 1

City 2

City N

Paging Terminal Overview

CallersCallers

PSTNPSTN

PagersPagers

Operators Entering Alphanumeric MessagesOperators Entering Alphanumeric Messages

Wide-Area ApplicationsWide-Area Applications

TNPPTNPP

Paging Paging TerminalTerminal

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)

Simulcast

Transmitter A

Transmitter BTransmitter B

LinkLink

Overlap AreaOverlap Area

15 m. sec15 m. sec

10 m. sec10 m. sec

??

FLEX (One-way paging)

• 1600, 3200, 6400 bps• Four-minute FLEX

protocol cycle• Short capcodes: 7 digits• Long capcodes: 9 digits

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 - 6400 bps, 3200 bps, 1600 bps• • Reverse - 9600 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

•

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 frameCollapse of 2 scans every 4th frameCollapse of 3 scans every 8th frameCollapse of 4 scans every 16th frameCollapse of 5 scans every 32nd frameCollapse of 6 scans one out of every 64th frameCollapse of 7 scans every 128th frame

ReFLEX ReFLEX (Two-way paging continued)(Two-way paging continued)

ReFLEX (Two-way paging)

• Narrowband PCS• Nationwide frequencies• Forward: 896-902 MHz• Reverse: 929 - 931, 940 -

941 MHz

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– Email– SMS– IM

• Telematics– Private vehicles (Onstar)– Commercial

• Telemetry

9.6 to 14.4 Kb/sec 115 Kb/sec 384 Kb/sec 384+ Kb/sec(GPRS) (EDGE) (UMTS)

9.6 to 43.2 Kb/sec

9.6 Kb/sec 60-70 Kb/sec ???

19.2 Kb/sec

4.8 to 19.2 Kb/sec

9.6 Kb/sec 64 Kb/sec

2G 2.5G 3G

14.4 – 64 Kb/sec 144 Kb/sec 384 Kb/seccdmaOne (95A-95B) (cdma2000 1XRTT) (cdma2000

EVDV)

GSM

TDMA

CDMA

iDEN

CDPD

Mobitex &

DataTAC

ReFLEX

2000 2001 2002 2003 2004 2005

Cellular Standards & Evolution

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

Existing Mobile Terminals and Devices

Handset

PersonalInformation

Manager

Personal Communicator

Handheld PC

LaptopPC

Low EndLow End High EndHigh End

Voice andSMS

Data Voice andData

Data Data

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 OSNative OS PalmPalm SymbianSymbian Windows Windows

CECE LinuxLinux

Virtual MachineVirtual Machine Sun J2MESun J2ME Qualcomm Qualcomm

BREWBREW AppForgeAppForge Syclo AgentrySyclo Agentry

Markup LanguageMarkup Language

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 PrivacyIssues

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 "email" address– SMTP Interface– 3125551234@wireless.att.net

TechnologyTechnology Message Message LengthLength

2- way?2- way?

GSMGSM 160 bytes160 bytes YesYes

TDMA/PDCTDMA/PDC 160 bytes160 bytes No*No*

CDMACDMA 256 bytes256 bytes YesYes

iDENiDEN 140 bytes140 bytes YesYes

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 30-40 msgs / month / person

– Especially by young people• Cheaper than in the US• Interchange agreements between carriers

SMS Advantages SMS Disadvantages

• Adopted by young people• Simple• Fast• Inexpensive• 2-way (some networks)• “Poor person's” email

• 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

The Convergence - Multichannel• Universal NET Access

PDASet Top BoxWeb PadGames Console

WID

MessagingContacts Agenda

Secure personal data

Fax

Corporate data

Inter/Intra/ExtraNET

WAP PhoneWork PC

Home PC