Public or Private (2)

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Benedict Foster
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// Public or Private () CCST90 Mar, 0 Dr.

and Electronic Engineering The Making of

Systematically capture photos of the street

1 // Public or Private () CCST90 Mar, 0 Dr. Hayden Kwok-Hay So Department of Electrical and Electronic Engineering The Making of Google Street View Google Street View Systematically capture photos of the street by driving specially designed car with 0 degree camera E.g. Systematically blurs faces and car license plates due to privacy concern

// Google Streetview Controversy? Mother's fury after Google Street View publishes naked picture of her son, three, online http://www.dailymail.co.

2 // Google Streetview Controversy? Mother's fury after Google Street View publishes naked picture of her son, three, online Mothers-fury-Google-shows--year-old-son-naked-garden.html 8 Ways to Locate You n WiFi n GPS n Mobile Phone 9 0 Locating based on WiFi n Relatively straightforward n When a computer is connected to a Wi-Fi network, it must associate itself with a wireless access point. n The range of WiFi is usually short è the computer must be relatively close to the access point è computer location access point location But how do we know location of an access point?

// Global Navigation Systems n Satellite-based navigation/positioning systems n Major systems: GPS GLONASS COMPASS Galileo USA Russia China European Union n GPS (from USA) is most popular GPS n

3 // Global Navigation Systems n Satellite-based navigation/positioning systems n Major systems: GPS GLONASS COMPASS Galileo USA Russia China European Union n GPS (from USA) is most popular GPS n Global Positioning System n Provides location and time information to receiver based on satellites n Developed by the US government Still largely maintained and controlled by the US government n Free use for public worldwide As long as you have the right receiver Two coexisting versions n Precise Positioning System (PPS) Military Use More robust Redundant information and encryption Avoid Jamming n Standard Positioning System (SPS) Civilian Use Less robust No encryption Accuracy n Originally PPS has higher precision than SPS. n But augmented GPS systems have made civilian GPS as precise as military system WAAS, DGPS, AGPS, etc n Today, civilian systems have accuracy to about a few meters. How does it work? n Conceptually divided into -segments n Space Segment: satellites orbiting earth to provide information in operation as of Mar 008 Very high precision atomic clock on-board Adjusted according to fine details only revealed by relativity n Control Segment: Ground control stations that monitor and control the satellites n User Segment: GPS receivers of the user Orbiting Satellites n Real time location: 8

// Calculating your Location n Receiver obtains signals from at least different satellites The orbit is such that at any one time, there will be at least in sight n The signals contain: Location of

distance to fixed points with known position. n In D, need fixed, known points to locate position n E.g.

4 // Calculating your Location n Receiver obtains signals from at least different satellites The orbit is such that at any one time, there will be at least in sight n The signals contain: Location of the satellite in space Time of the message More n Receiver calculates distance from each of the satellites n Calculate exact location by trilateration Trilateration n Calculate position bases on the distance to fixed points with known position. n In D, need fixed, known points to locate position n E.g. distance to P è circumference of red circle + distance to P è A or B + distance to P è B n More complex in D but similar concept 9 0 Using Location Information n The GPS system allows a device to calculate it s own location. It only knows its location GPS system cannot be used to transmit location information More importantly: n how this information is being used. n Common usage model: Location-aware application Tracking Logging Location Aware Application n Allows an application to display relevant information depending on the user s current geographical location n E.g. Application shows/recommends restaurants close to your location Games that require you to travel to specific geographical location for puzzle solving A mapping application show your current location on map by default n But you are sharing your location information to the application Your electronic device now knows a lot about you. Accessing Location Information n When is it ok to allow an application to use your location data? n Steve Job: We take privacy extremely seriously n See: n Privacy means people know what they're signing up for. In plain English. And repeatedly. Location Information Misuse? n In April 0, Alasdair Allan and Pete Warden discovered that Apple secretly tracking location in all iphones?

// http://www.apple.com/pr/library/0/0/apple-q-a-on-location-data.

Rather, it s maintaining a database of Wi-Fi hotspots and cell towers around your current

Calculating a phone s location using just GPS satellite data can take up to several

iphone can reduce this time to just a few seconds by using Wi-Fi hotspot and cell tower

5 // iphone Location Log The iphone is not logging your location. Rather, it s maintaining a database of Wi-Fi hotspots and cell towers around your current location to help your iphone rapidly and accurately calculate its location when requested. Calculating a phone s location using just GPS satellite data can take up to several minutes. iphone can reduce this time to just a few seconds by using Wi-Fi hotspot and cell tower data to quickly find GPS satellites, and even triangulate its location using just Wi-Fi hotspot and cell tower data when GPS is not available Plotting the location information on a trip from NY to DC, USA. 8 0 Late 90s Early 80s 9

// First Mobile Phone Motorola DynaTAC Year: 99 Weight: > lbs Talk Time: 0 mins

systems 90s Analog Voice G systems AMPS Pre-Cellular Networks A Brief Walk in

systems were designed so that one radio base station has enough power to cover a

systems GSM system GPRS PSTN Digital Voice and Data G systems EDGE UMTS

is large only small number of users are allowed at the same time 0km Cellular

needed Large physical size Not convenient 0m Many low-power base stations cover

each station is called cell Individual cell sites are connected by conventional

area is smaller The first cellular telephone system (Bell Telephone System) began

6 // First Mobile Phone Motorola DynaTAC Year: 99 Weight: > lbs Talk Time: 0 mins Charge Time: 0 hours Cost: ~US$000 Around 00 DynaTAC 8000x (98) Pre-cellular systems 90s Analog Voice G systems AMPS Pre-Cellular Networks A Brief Walk in Cell Phone History Logically an extension to landline telephone service Early systems were designed so that one radio base station has enough power to cover a large geographical area Entire city Large rural area Digital Voice (and Data) G systems GSM system GPRS PSTN Digital Voice and Data G systems EDGE UMTS PSTN=Public Switch Telephone Network Pre-Cellular Networks The collision domain is large only small number of users are allowed at the same time 0km Cellular Networks Mobile phones must transmit with high power as well Larger battery is needed Large physical size Not convenient 0m Many low-power base stations cover the service area instead of one high-power base station The region covered by each station is called cell Individual cell sites are connected by conventional wired technology Number of active users in each cell is still restricted, but the area is smaller The first cellular telephone system (Bell Telephone System) began to deploy in 99 Neighbor cells use different frequency channels to reduce interference Need ways to support simultaneous users!

.... QR Mobile ST... Broadcasting.9.9... ]^ Satellite _W Fixed..... 0. 0 0 0.9.99.0. 9. UVWX Radiolocation UVYZ Radionavigation Note : The frequency chart is not drawn to scale.

$0....9. 0.. 8 0 0. 0. [\QR. Maritime Mobile.8. [\UVYZ.. Maritime Radionavigation 0 9 9.0 9. ZMQR 9.9. 0.. ZMUVYZ Aeronautical Mobile 80 0. Aeronautical Radionavigation..8.. 0 90 8. 8. 8. 8.8 9 9. 9.. 8 8.$

7 .... QR Mobile ST... Broadcasting ]^ Satellite _W Fixed UVWX Radiolocation UVYZ Radionavigation Note : The frequency chart is not drawn to scale. Details can be found in Hong Kong Table of Frequency Allocations which can be obtained from OFTA website ( : "#$%&'()*+,-./089:;<#$=>&?8@ ( [\QR. Maritime Mobile.8. [\UVYZ.. Maritime Radionavigation ZMQR ZMUVYZ Aeronautical Mobile Aeronautical Radionavigation `abc Meteorological Aids Lde 8 Radio Astronomy fg hfijklmn(ism) 90 Industrial, Scientific & Medical (ISM) Amateur MNOP Space Research op#$qrns (SFT) 8... Standard Frequency and Time Signal (SFT) tuvw 8 Earth Exploration DEFGHI:JKL All emissions are prohibited ABC= To be planned // Tech Brief: Radio Frequency n Wireless communications are based on electromagnetic (EM) waves n The empty space can be divided into different radio frequencies Frequency measured in Hz n Different communication schemes use different chunks of the radio frequency space so they will not interfere with each other n Example frequency: Commercial Radio (88 90): 88. MHz, 90. MHz 80.g WiFi products: ~. GHz Analog TV broadcast in HK: ~00 MHz Cell Phone: 900 MHz, 800MHz, 00 MHz Frequency Allocation in HK VLF khz - 0kHz LF 0kHz - 00kHz MF 00kHz - MHz HF MHz - 0MHz VHF 0MHz - 00MHz UHF 00MHz - GHz SHF GHz - 0GHz EHF 0GHz - 00GHz 00kHz 0kHz khz GHz 00MHz 0MHz MHz 0GHz Hong Kong Frequency Allocation Chart (!"#$%&'() n Office of the Telecommunications Authority (OFTA) GHz GHz 00MHz 0MHz MHz 00kHz 0kHz 00GHz Cellular Networks Components n Three basic components: Mobile station (MS) Base station (BS) Mobile switching center (MSC) n Mobile station (e.g. a cell phone) connects to a base station through a wireless link n Base station connects to an MSC n MSC connects to the PSTN Handoff (Handover) n When a cell phone in conversation moves between the coverage of a cell, call must be handed off to other cell n When the signal becomes weak in the active site, central control unit will find another site n Different cell phone systems have different handoff protocols When a handoff is not successful, the call is dropped 9 0 Mobile phone positioning n Since the physical location of the cell towers are known, it is possible to locate a mobile phone through triangulation and/or trilateration n Triangulation: Find the location of a mobile phone given the angle of the mobile phone relative to the cell tower is known n Trilateration Find the location of a mobile phone given the distance of the mobile phone relative to the cell tower is know.

8 // Tower-based Positioning n Only a cell tower would know the angle of a mobile phone relative to the tower Multiple antennas on a tower n Using cell tower information only, the network operator will be able to locate a mobile phone if enough cell tower is in range n It is slightly more difficult for a tower to find out the distance to a phone Mobile Device-based Positioning n A mobile device can find out the distance to a cell tower from the signal strength it receives n If it receives enough signals from multiple cell tower, it can find out its location But n It needs to know the physical location of the tower

Radio Spectrum Allocations 101

Radio Spectrum Allocations 101 Presentation to The National Academies Board on Physics and Astronomy Committee on Radio Frequencies Washington DC May 27 th, 2009 Andrew Clegg National Science Foundation