6/23/2015 1r. smith - university of st thomas - minnesota cisc 370 - class today project...

04/18/23 1R. Smith - University of St Thomas - Minnesota

CISC 370 - Class Today CISC 370 - Class Today

• Project NotesProject Notes• Satellites Cell/WirelessSatellites Cell/Wireless• Lab 2Lab 2


Project NotesProject Notes

• Presentation schedule is available on Presentation schedule is available on BlackboardBlackboard– Time: 15-20 minutes per groupTime: 15-20 minutes per group

• I need one exam question from each projectI need one exam question from each project– No “true vs false”No “true vs false”– MUST be covered in your presentation!MUST be covered in your presentation!– Good ideas:Good ideas:

• Define a key term – not something in the bookDefine a key term – not something in the book• List major elements – not in the bookList major elements – not in the book• Describe a problem/solution presented in the projectDescribe a problem/solution presented in the project

– E-mail the exam question on Tuesday (paper deadline)E-mail the exam question on Tuesday (paper deadline)


Presentation SchedulePresentation Schedule

• Tuesday, May 6:Tuesday, May 6:– MahowaldMahowald

Doyle, RobyDoyle, RobyLyons, PalchukLyons, PalchukCourtneyCourtneyVangVang

• Thursday, May 8:Thursday, May 8:– Albright, RoseAlbright, Rose

Beckman, WardBeckman, WardThornton, Kursis, DavisThornton, Kursis, DavisSymoniak Symoniak


Cell PhonesCell Phones

• Based on low power transmitters and lots of Based on low power transmitters and lots of frequenciesfrequencies– Each "cell" has a "base station" at the centerEach "cell" has a "base station" at the center

• Layout in a honeycomb (hexagons) = Layout in a honeycomb (hexagons) = equidistant base stationsequidistant base stations– This is the default designThis is the default design– Honeycomb is varied according to topography, call load, etc.Honeycomb is varied according to topography, call load, etc.

• Each cell is assigned a group of frequenciesEach cell is assigned a group of frequencies• Adjacent cells use different frequenciesAdjacent cells use different frequencies

Cell System GeographyCell System Geography

• ““Beehive” arrangementBeehive” arrangement– Squares are easier to lay out (‘sections’ in homesteading)Squares are easier to lay out (‘sections’ in homesteading)– Hexagons are simplest simulation of packed circlesHexagons are simplest simulation of packed circles

• Equidistant centers between cellsEquidistant centers between cells

• Not all cell towers are identicalNot all cell towers are identical– Impact of cell traffic loadImpact of cell traffic load

• Geometry and frequency bands limit a cell’s loadGeometry and frequency bands limit a cell’s load• Most cells are far below their potential capacityMost cells are far below their potential capacity

– Cell versus ‘microcell’Cell versus ‘microcell’• Microcell has smaller transmitter powerMicrocell has smaller transmitter power• Covers smaller area, usually used in citiesCovers smaller area, usually used in cities• More cells = more capacityMore cells = more capacity


A somewhat busy towerA somewhat busy tower

• Rural, not urbanRural, not urban

• The “equipment enclosure”The “equipment enclosure”– Hidden in the treesHidden in the trees– Formerly a small houseFormerly a small house

• 1 story farm/sharecropper house1 story farm/sharecropper house


Antenna closeupAntenna closeup

• Horizontal white thingiesHorizontal white thingies– Three of them aboveThree of them above

– Each is a cell antennaEach is a cell antenna

– Fixed capacity (#calls at a time)Fixed capacity (#calls at a time)

– ““Wedge” coverageWedge” coverage


A modern cellA modern cell

• Cell phones onlyCell phones only• Self containedSelf contained

• (not in use, either)(not in use, either)


The antennaeThe antennae

• Triangle shapeTriangle shape– Cheaper than hexagonCheaper than hexagon– Provides good coverage for Provides good coverage for

the directional antennaethe directional antennae

• Not in useNot in use– ““placeholder” antennaeplaceholder” antennae


A busier towerA busier tower

• 30 miles north of Boston30 miles north of Boston– pseudo-rural (expensive) suburbpseudo-rural (expensive) suburb

• Count those antennae!Count those antennae!


A very, very rural towerA very, very rural tower

• Just south of Red WingJust south of Red Wing– We are looking northwards to the towerWe are looking northwards to the tower

• Not too many antennaeNot too many antennae– What conclusions can we draw about What conclusions can we draw about

wherewhere the cell customers are? the cell customers are?


More towersMore towers

Are these cell towers?Are these cell towers?


Close upsClose ups

Clearer now?Clearer now?Omni-directionalOmni-directional

UnidirectionalUnidirectional


SummarySummary

• How do we assess a cell phone network?How do we assess a cell phone network?

• What do the antennae tell us?What do the antennae tell us?– Current traffic levelsCurrent traffic levels– Direction of traffic levelsDirection of traffic levels– Available room for growthAvailable room for growth

• What about cell phone antennae on buildings?What about cell phone antennae on buildings?– Apartments on the Cretin/Grand cornerApartments on the Cretin/Grand corner– Apartments along I-94 near Dale exitApartments along I-94 near Dale exit



Cell OperationCell Operation

• OrganizationOrganization– Base stations connect to a mobile switching officeBase stations connect to a mobile switching office– Mobile switching office connects to POTSMobile switching office connects to POTS

• Handling a callHandling a call– Turn on the phone - it searches for a nearby cellTurn on the phone - it searches for a nearby cell– Phone does handshake with strongest base stationPhone does handshake with strongest base station

• "Setup channel" is identified to handle calls"Setup channel" is identified to handle calls• Base station registers the phone's location for incoming Base station registers the phone's location for incoming

callscalls


Operation, continuedOperation, continued

• Outgoing callOutgoing call– Phone checks to see if setup channel is freePhone checks to see if setup channel is free– Once channel is free, sends the call requestOnce channel is free, sends the call request– Mobile switching office tries to make call.Mobile switching office tries to make call.– If succeeds, the base station assigns a channel to the phoneIf succeeds, the base station assigns a channel to the phone

• HandoffHandoff– If the phone moves out of range, it contacts the nearest strong If the phone moves out of range, it contacts the nearest strong

base stationbase station– New base station provides a new control channelNew base station provides a new control channel– If a call is in progress, they assign a new channel to the call If a call is in progress, they assign a new channel to the call

and new base station handles itand new base station handles it


Increasing cell system capacityIncreasing cell system capacity

• Add new channelsAdd new channels– Look at a base station and count the vertical antenna elementsLook at a base station and count the vertical antenna elements

– Busy stations have lots of elements, less busy ones have fewerBusy stations have lots of elements, less busy ones have fewer

• Frequency borrowingFrequency borrowing– A more-busy station borrows a frequency from a less-busy neighborA more-busy station borrows a frequency from a less-busy neighbor

• Cell splittingCell splitting– Change the geographic coverage of adjacent cells to fit in another Change the geographic coverage of adjacent cells to fit in another

base stationbase station

– If you get a lot of cells in a small area, you may get "microcells" that If you get a lot of cells in a small area, you may get "microcells" that use lower power base stationsuse lower power base stations

• Cell sectoringCell sectoring– Use directional antennas and assign specific channels to specific Use directional antennas and assign specific channels to specific

directions.directions.

– Yields wedge-shaped channel coverage areasYields wedge-shaped channel coverage areas


Satellite System ArchitectureSatellite System Architecture

• Earth stationsEarth stations– Fixed locations with big satellite antennasFixed locations with big satellite antennas– or small, mobile devices like cel phonesor small, mobile devices like cel phones

• Satellites Satellites – Orbiting devices that relay the messages, Orbiting devices that relay the messages, – usually from a mobile device to a fixed stationusually from a mobile device to a fixed station– Or vice versa (pagers)Or vice versa (pagers)

• ElementsElements– + Uplink - message going from earth station to satellite+ Uplink - message going from earth station to satellite– + Downlink - opposite direction+ Downlink - opposite direction– + Transponder - typical satellite function - simply echoes the + Transponder - typical satellite function - simply echoes the

uplink signal onto a downlink.uplink signal onto a downlink.

Remember strong vs weakRemember strong vs weak

• Portable devices usually have weak signalsPortable devices usually have weak signals– battery and portability limitationsbattery and portability limitations

• Satellites have signal limitations Satellites have signal limitations – How much circuitry can we launch into orbit and keep there?How much circuitry can we launch into orbit and keep there?– How much power can we get from solar cells?How much power can we get from solar cells?

• Fixed Earth StationFixed Earth Station– The Most powerful element is the fixed earth station: The Most powerful element is the fixed earth station:

• big antenna, lots of power big antenna, lots of power • Sends strong signal to satelliteSends strong signal to satellite• detects weak signals in a downlinkdetects weak signals in a downlink• Can reduce the satellite’s needsCan reduce the satellite’s needs


Classic Satellite ApplicationsClassic Satellite Applications

• Earth surveillance (weather, spying, etc)Earth surveillance (weather, spying, etc)– Satellite collects sensor data, transmits to base stationSatellite collects sensor data, transmits to base station– Powerful base station, huge antennaPowerful base station, huge antenna

• Network TelevisionNetwork Television– Powerful Earth station transmits the program signalPowerful Earth station transmits the program signal– Smaller (but still huge) antennas to receive the signalSmaller (but still huge) antennas to receive the signal

• PagersPagers– Earth station transmits the signal, bounces off the satelliteEarth station transmits the signal, bounces off the satellite– Activates small, low powered receiverActivates small, low powered receiver


New Tech applicationsNew Tech applications

• Home TelevisionHome Television– Powered Earth station transmitters, powered (small) receiversPowered Earth station transmitters, powered (small) receivers– Satellite simply bounces the signalSatellite simply bounces the signal

• Telephones (Iridium, others)Telephones (Iridium, others)– Weak base stations (phones)Weak base stations (phones)– Satellites talk to phones, Earth stations, and each otherSatellites talk to phones, Earth stations, and each other– Earth stations provide local phone company connectionEarth stations provide local phone company connection

• GPSGPS– Satellites transmit standard, coded signalsSatellites transmit standard, coded signals– Earth receivers are small, portable, vulnerable to signal Earth receivers are small, portable, vulnerable to signal

blockageblockage



Satellite constellationsSatellite constellations

• GEOGEO• LEOLEO• MEOMEO


o GEO - geostationary orbito GEO - geostationary orbit

• + Fixed in one location+ Fixed in one location– 35,863km above earth (about 21K miles) on the Equator35,863km above earth (about 21K miles) on the Equator

• + "Geosynchronous“+ "Geosynchronous“– that height, but not necessarily a fixed locationthat height, but not necessarily a fixed location

• + Easiest type of satellite to handle+ Easiest type of satellite to handle– location never changeslocation never changes


GEOGEO

• BenefitsBenefits– # No frequency shift problems from Doppler effect# No frequency shift problems from Doppler effect– # Easy to track from earth, since it doesn't move# Easy to track from earth, since it doesn't move– # Fewer satellites (3) can cover entire habitable surface# Fewer satellites (3) can cover entire habitable surface

• ProblemsProblems– # Signal gets really weak after travelling 35K km# Signal gets really weak after travelling 35K km– # Polar regions are hard to cover from the equator# Polar regions are hard to cover from the equator– # Distance causes delays even at the speed of light# Distance causes delays even at the speed of light

• Examples: Examples: – TV - delay isn't a problem for 1-way broadcast videoTV - delay isn't a problem for 1-way broadcast video– ICO started with GEO satelliteICO started with GEO satellite


LEO - low earth orbitLEO - low earth orbit

• Orbit at 500 to 1500 KM above the earthOrbit at 500 to 1500 KM above the earth• BenefitsBenefits

– Very low transmission delay (20 ms)Very low transmission delay (20 ms)

– Strong signalsStrong signals

• Problem: lower altitude = higher speedProblem: lower altitude = higher speed– Harder to trackHarder to track

– Doppler shifts affect frequenciesDoppler shifts affect frequencies

• Problem: lower altitude = smaller signal footprintProblem: lower altitude = smaller signal footprint– Each satellite only covers circle with 8000 KM diameterEach satellite only covers circle with 8000 KM diameter

– Each satellite is visible for only 20 minutes at a time - must have Each satellite is visible for only 20 minutes at a time - must have "hand off" between satellites or you lose the connection"hand off" between satellites or you lose the connection

• Need LOTS of satellites to cover the whole planetNeed LOTS of satellites to cover the whole planet


ExamplesExamples

• ORBCOMM – ORBCOMM – – called a 'little LEO' – called a 'little LEO' – – small bandwidth satellites for paging and short text msgssmall bandwidth satellites for paging and short text msgs

• GlobalstarGlobalstar– called a 'big LEO‘called a 'big LEO‘– higher data rateshigher data rates– 48 satellites, pure transponders48 satellites, pure transponders

• IridiumIridium– 66 satellites @ 485 mile altitude66 satellites @ 485 mile altitude– they had to develop satellite mass production techniques to they had to develop satellite mass production techniques to

make this workmake this work– satellites will to each other as well as to ground stationssatellites will to each other as well as to ground stations


o MEO - Medium Earth Orbito MEO - Medium Earth Orbit

• + Height of 5000 to 12,000 KM+ Height of 5000 to 12,000 KM• + Signal delay ~ 50ms+ Signal delay ~ 50ms• + Footprint = 10K-15K km+ Footprint = 10K-15K km• + Less handoff, less Doppler shift, fewer satellites than + Less handoff, less Doppler shift, fewer satellites than

LEOLEO• + Less round trip delay than GEO+ Less round trip delay than GEO• + Example: ICO ("New ICO") with planned set of 12 + Example: ICO ("New ICO") with planned set of 12

satellites at 10,400 km orbitssatellites at 10,400 km orbits

• Imagery - Imagery - http://www.ee.surrey.ac.uk/Personal/L.Wood/constellatihttp://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/globalstar.htmlons/globalstar.html

Thursday

• Homework Due

• Will work Case Studies 6 and 7

Firewall LabFirewall Lab

• Configuring the Linksys router/firewallConfiguring the Linksys router/firewall– BlockingBlocking– Network address translationNetwork address translation

• A configuration problemA configuration problem– We need to watch with WireSharkWe need to watch with WireShark– Hub technology is lagging the network technologyHub technology is lagging the network technology

• Due in a couple of weeksDue in a couple of weeks

Linksys Home PageLinksys Home Page

• Type in the router’s Type in the router’s IP addressIP address

• 10.10.10.1010.10.10.10– or 192.168.1.1or 192.168.1.1

• PasswordPassword– Replace ‘1’ with ‘2’ in Replace ‘1’ with ‘2’ in

the admin passwordthe admin password– or “admin”or “admin”

March 2005 30R. Smith - University of St Thomas - Minnesota

Five major headings of controlsFive major headings of controls

• SetupSetup– Establishes the local address and configurationEstablishes the local address and configuration

• SecuritySecurity– Filters traffic, enables/disables certain types of trafficFilters traffic, enables/disables certain types of traffic

• Applications and GamingApplications and Gaming– Allows connections to servers on the LAN from the InternetAllows connections to servers on the LAN from the Internet

• AdministrationAdministration– Change password, enable remote management featuresChange password, enable remote management features

• StatusStatus– Check the status of the WAN connectionCheck the status of the WAN connection– Check status of LAN and its attached hostsCheck status of LAN and its attached hosts


Address SetupAddress Setup

• Set to “Obtain IP Automatically”Set to “Obtain IP Automatically”• Our local default internal addresses are Net 10Our local default internal addresses are Net 10


Address SettingsAddress Settings

• Set local address to 10.10.10.10Set local address to 10.10.10.10– That’s the address of this routerThat’s the address of this router– Subnet mask 255.255.255.0Subnet mask 255.255.255.0

• Enable Local DHCP serviceEnable Local DHCP service– Start assigning local addresses at 100, total of 50 addressesStart assigning local addresses at 100, total of 50 addresses– Renews address “leases” dailyRenews address “leases” daily


Looking at the Router StatusLooking at the Router Status

• Internal and external routing dataInternal and external routing data– The “Internet” addresses are for the “outside” of the routerThe “Internet” addresses are for the “outside” of the router


Looking at the LAN StatusLooking at the LAN Status

• Gives addressing information about the router Gives addressing information about the router as seen from the LAN sideas seen from the LAN side– Click the button to see the DHCP client tableClick the button to see the DHCP client table


DHCP Client TableDHCP Client Table

Lists all active Lists all active clients on the clients on the LANLAN

Provides a map Provides a map to the LANto the LAN

Just like the labJust like the lab


The Management ScreenThe Management Screen

Starting point for Starting point for lower level lower level controlscontrols

Actually, password Actually, password changing is all changing is all this is good forthis is good for

PLEASE DON’T PLEASE DON’T CHANGE THE CHANGE THE PASSWORD.PASSWORD.


Traffic FilteringTraffic Filtering

• Blocks LAN machines Blocks LAN machines from the Internetfrom the Internet– Block by IP addressBlock by IP address– Block by MAC addressBlock by MAC address

• Block Port NumbersBlock Port Numbers• Other filtersOther filters

– MulticastMulticast– External Internet queriesExternal Internet queries

• mostly Pingsmostly Pings


Port ForwardingPort Forwarding

• Allows inbound connections – forwards particular Allows inbound connections – forwards particular ports to specific PCs on the LANports to specific PCs on the LAN

• Under the “Applications and Gaming” tab.Under the “Applications and Gaming” tab.


Firewall LabFirewall Lab

• OverviewOverview– Rewire the lab to use the firewallRewire the lab to use the firewall– Map the rewired labMap the rewired lab– Demonstrate host blocking through the firewallDemonstrate host blocking through the firewall– Demonstrate NAT through the firewallDemonstrate NAT through the firewall



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