SM3121SM3121Communications Communications

TechnologyTechnology

Mark GreenMark Green

School of Creative MediaSchool of Creative Media

IntroductionIntroduction

Most mobile devices need to communicateMost mobile devices need to communicate One of the main reasons for having themOne of the main reasons for having them Mobile phone isn’t very useful if you can’t Mobile phone isn’t very useful if you can’t

call anyone!!call anyone!! There are numerous communications There are numerous communications

systems that we can use, depend upon systems that we can use, depend upon range and costrange and cost

IntroductionIntroduction

Technologies:Technologies: Infrared: very local, but very cheapInfrared: very local, but very cheap Bluetooth: short range (10m), becoming Bluetooth: short range (10m), becoming

widely available, fairly high speedwidely available, fairly high speed Wireless Ethernet: medium range (100m or Wireless Ethernet: medium range (100m or

more), high speed, high costmore), high speed, high cost Mobile phone network: long range, low speed, Mobile phone network: long range, low speed,

on most phones, quite expensiveon most phones, quite expensive Need to know what to use and whenNeed to know what to use and when

WiFiWiFi

Wireless Ethernet is the fastest wireless Wireless Ethernet is the fastest wireless technologytechnology

Currently most are 11Mbps, but new ones Currently most are 11Mbps, but new ones are at 54Mbpsare at 54Mbps

WiFi hardware standard on many new WiFi hardware standard on many new PCsPCs

Becoming widely available in public Becoming widely available in public places, coffee shops, universities, etcplaces, coffee shops, universities, etc

WiFiWiFi

Two main components:Two main components: Access point – AP, the interface between Access point – AP, the interface between

wireless and wired network, in control of the wireless and wired network, in control of the networknetwork

Client – the hardware that runs on the mobile Client – the hardware that runs on the mobile devicedevice

A client must connect to an AP before it A client must connect to an AP before it can use the networkcan use the network

WiFiWiFi

A WiFi network can have a single AP, A WiFi network can have a single AP, typical in homestypical in homes

Could have multiple APs, need to Could have multiple APs, need to coordinate APs as users move around the coordinate APs as users move around the areaarea

Don’t want user to know when they switch Don’t want user to know when they switch from one AP to another, shouldn’t cause a from one AP to another, shouldn’t cause a network disconnectionnetwork disconnection

WiFiWiFi

Most WiFi systems use 2.4GHz radio Most WiFi systems use 2.4GHz radio band, this is divided into approximately 10 band, this is divided into approximately 10 channelschannels

AP and client must agree on channel to AP and client must agree on channel to useuse

Newer clients and software can search Newer clients and software can search channels for available APs, older ones not channels for available APs, older ones not as smartas smart

WiFiWiFi

This is a broadcast medium:This is a broadcast medium: You are sharing the bandwidth with everyone You are sharing the bandwidth with everyone

else on the APelse on the AP In public areas will not see full 11Mbps In public areas will not see full 11Mbps

bandwidth, could be much less than 1Mbpsbandwidth, could be much less than 1Mbps Other clients see what you are sending and Other clients see what you are sending and

receivingreceiving Some attempt at security, but this can easily Some attempt at security, but this can easily

be brokenbe broken

WiFiWiFi

Supports most Internet standardsSupports most Internet standards Can do almost anything you can do with a Can do almost anything you can do with a

standard PCstandard PC This is not always the case with the other This is not always the case with the other

communications technologiescommunications technologies In terms of equipment the most expensive In terms of equipment the most expensive

technology, but bandwidth usage can be technology, but bandwidth usage can be quite cheapquite cheap

HackingHacking

WiFi can be very insecure, need to know WiFi can be very insecure, need to know what you are doingwhat you are doing

Can have “open” AP, no security and Can have “open” AP, no security and anyone can use itanyone can use it

Sometimes the default for home systems, Sometimes the default for home systems, easier to set upeasier to set up

Some people look for open systems so Some people look for open systems so they can steal bandwidththey can steal bandwidth

BluetoothBluetooth

Originally developed to replace the wires Originally developed to replace the wires in consumer devicesin consumer devices

Short range, relatively high speed Short range, relatively high speed networking technologynetworking technology

Devices can be up to 10m apart, Devices can be up to 10m apart, maximum bandwidth of about 1Mbpsmaximum bandwidth of about 1Mbps

Very complicated standard with a wide Very complicated standard with a wide range of optional featuresrange of optional features

BluetoothBluetooth

Bluetooth uses the same frequency band Bluetooth uses the same frequency band as WiFi, so they can interfereas WiFi, so they can interfere

The Bluetooth standard is much more The Bluetooth standard is much more secure than WiFi and its easier for a group secure than WiFi and its easier for a group to share the bandwidthto share the bandwidth

Now becoming standard on many mobile Now becoming standard on many mobile devices, such as mobile phones and devices, such as mobile phones and PDAs, relatively easy to add to PCPDAs, relatively easy to add to PC

BluetoothBluetooth

Example: mobile phone and headset can Example: mobile phone and headset can use Bluetooth instead of wiresuse Bluetooth instead of wires

Bluetooth is not as complete as WiFi, it Bluetooth is not as complete as WiFi, it may not support any of the Internet may not support any of the Internet standardsstandards

Could just be used for file transfers or Could just be used for file transfers or simple data transfers, depending upon the simple data transfers, depending upon the devices useddevices used

BluetoothBluetooth

One of its strengths is One of its strengths is discoverydiscovery a Bluetooth device can easily detect other a Bluetooth device can easily detect other

devices nearby and automatically connect devices nearby and automatically connect to themto them

Devices can easily move from one Devices can easily move from one network to another and the connection is network to another and the connection is automaticautomatic

More flexible network organizationMore flexible network organization

BluetoothBluetooth

Since Bluetooth is short range it can be Since Bluetooth is short range it can be used for location based servicesused for location based services

Know that the other device is within 10m, Know that the other device is within 10m, can send information that is location can send information that is location dependentdependent

Send business cards, advertisements, Send business cards, advertisements, maps, tourist information, connect to maps, tourist information, connect to vending machine for payment, etcvending machine for payment, etc

InfraredInfrared

Send information on infrared light signalSend information on infrared light signal Very cheap technology, medium speedVery cheap technology, medium speed Typically IR connections are around Typically IR connections are around

100Kbps, but they can be faster100Kbps, but they can be faster Need to be relatively close, typically less Need to be relatively close, typically less

than 4m and cannot block light paththan 4m and cannot block light path Used in remote controls, laptop Used in remote controls, laptop

computers, printers, etccomputers, printers, etc

InfraredInfrared

Basically viewed as a serial connection, Basically viewed as a serial connection, used for sending dataused for sending data

Could be used for Internet and other Could be used for Internet and other services, but would require considerable services, but would require considerable programmingprogramming

Slowly being replaced by Bluetooth in Slowly being replaced by Bluetooth in mobile devices, only real advantage is mobile devices, only real advantage is priceprice

Mobile Phone NetworkMobile Phone Network

This is a real mess:This is a real mess: Too many standards, some poorly thought out Too many standards, some poorly thought out

and didn’t workand didn’t work Bandwidth is quite low, except for 3GBandwidth is quite low, except for 3G Bandwidth is very expensiveBandwidth is very expensive Little thought given to how it would actually be Little thought given to how it would actually be

used and why people would pay for itused and why people would pay for it We will try to make some sense out of this We will try to make some sense out of this

situationsituation

Mobile Phone NetworkMobile Phone Network

Base technology is divided into Base technology is divided into generationsgenerations

1G – the initial analogue mobile phone 1G – the initial analogue mobile phone network, no longer usednetwork, no longer used

Did not support data transmission in the Did not support data transmission in the phone itself, could use external modem for phone itself, could use external modem for data, but usually limited to 9.6Kbpsdata, but usually limited to 9.6Kbps

Only voice servicesOnly voice services

Mobile Phone NetworkMobile Phone Network

2G – switch to digital, matches land lines 2G – switch to digital, matches land lines which are also largely digitalwhich are also largely digital

Several standards, GSM is used in HK, Several standards, GSM is used in HK, available in most of the worldavailable in most of the world

Supports data transmission, rates up to Supports data transmission, rates up to 9.6Kbps in standard systems9.6Kbps in standard systems

Start of data services, but not a major Start of data services, but not a major application or selling pointapplication or selling point

Mobile Phone NetworkMobile Phone Network

2.5G – basically 2G plus better data 2.5G – basically 2G plus better data services, most HK networks are at this services, most HK networks are at this levellevel

Adds GPRS (General Packet Radio Adds GPRS (General Packet Radio Services), theoretically capable of Services), theoretically capable of 170Kbps170Kbps

In HK GPRS seems to be limited to In HK GPRS seems to be limited to around 40 – 43 Kbps, but can get 56Kbps around 40 – 43 Kbps, but can get 56Kbps services at considerable extra costservices at considerable extra cost

Mobile Phone NetworkMobile Phone Network

3G – for HK service introduced in 2004, 3G – for HK service introduced in 2004, initially one carrier, now up to threeinitially one carrier, now up to three

Promises data speeds up to 2Mbps, don’t Promises data speeds up to 2Mbps, don’t know whether this will be available locallyknow whether this will be available locally

This high bandwidth may drop the cost of This high bandwidth may drop the cost of data services, currently 0.05 – 0.10 HK$ data services, currently 0.05 – 0.10 HK$ per Kbyte, very few unlimited usage plans, per Kbyte, very few unlimited usage plans, but they are very expensive but they are very expensive

Mobile ServicesMobile Services

There is a wide range of services built on There is a wide range of services built on top of the mobile phone networktop of the mobile phone network

Some of these services have been poorly Some of these services have been poorly designed, others have died very quicklydesigned, others have died very quickly

One solid standard would greatly help this One solid standard would greatly help this part of the industry:part of the industry: Convince consumers to buyConvince consumers to buy Provide a standard for developersProvide a standard for developers

WAPWAP

Wireless Application Protocol, there are Wireless Application Protocol, there are two versions of this standard WAP 1 and two versions of this standard WAP 1 and WAP 2WAP 2

These standards are quite different, both These standards are quite different, both technically and philosophicallytechnically and philosophically

Consumers usually not aware of the Consumers usually not aware of the difference, but its significant for developersdifference, but its significant for developers

Market is moving to WAP 2Market is moving to WAP 2

WAP 1WAP 1

Want to bring web and related services to Want to bring web and related services to mobile phonesmobile phones

Set of standards that are parallel to web Set of standards that are parallel to web standards, but not the samestandards, but not the same

Assumption: mobile phones are different, Assumption: mobile phones are different, so need a different set of standardsso need a different set of standards

Very big mistake, cannot take content Very big mistake, cannot take content developed for web and move to phonesdeveloped for web and move to phones

WAP 1WAP 1

WML – Wireless Markup Language, WML – Wireless Markup Language, similar to HTML, but not the samesimilar to HTML, but not the same

Uses some of the same tags, but has Uses some of the same tags, but has different structure and new tagsdifferent structure and new tags

Can use standard web servers with minor Can use standard web servers with minor modifications, but content must go through modifications, but content must go through a WAP gateway to convert to mobile a WAP gateway to convert to mobile phone formatphone format

WAP 1WAP 1

Different browsers interpret WML Different browsers interpret WML differently, so content can look different on differently, so content can look different on different phonesdifferent phones

Similar to HTML situation in mid 1990sSimilar to HTML situation in mid 1990s Has simple form processing, tables, user Has simple form processing, tables, user

interactioninteraction Can use server side scripts to dynamically Can use server side scripts to dynamically

generate contentgenerate content

WAP 1WAP 1

WMLScript – scripting language for WMLWMLScript – scripting language for WML Sort of like JavaScript, but not quite the Sort of like JavaScript, but not quite the

samesame Many phone browsers don’t support it, but Many phone browsers don’t support it, but

some dosome do Somewhat limited scripting language, not Somewhat limited scripting language, not

clear how useful it isclear how useful it is

WAP 2WAP 2

Totally different approach, try to stay as Totally different approach, try to stay as close to the web standards as possibleclose to the web standards as possible

Use subset of HTML and CSS to maintain Use subset of HTML and CSS to maintain compatibility with standard web pagescompatibility with standard web pages

Can be developed and tested using Can be developed and tested using standard web toolsstandard web tools

Should have more consistent appearance Should have more consistent appearance and behavior across a range of phonesand behavior across a range of phones

WAP 2WAP 2

Browser based on xHTML, the latest Browser based on xHTML, the latest version of HTMLversion of HTML

Special mobile profile developed for Special mobile profile developed for xHTML, along with CSS mobile standardxHTML, along with CSS mobile standard

A number of new services being A number of new services being developeddeveloped

Based on the standard Internet protocols, Based on the standard Internet protocols, can add email and other servicescan add email and other services

MessagingMessaging

One of the most popular mobile phone One of the most popular mobile phone featuresfeatures

Started with SMS – Short Message Started with SMS – Short Message Service, widely available, on most phonesService, widely available, on most phones

Basically a fixed size chunk of data that Basically a fixed size chunk of data that can be exchanged between phones, or can be exchanged between phones, or with a central servicewith a central service

Can have several formatsCan have several formats

MessagingMessaging

Simplest format is English text, messages Simplest format is English text, messages restricted to 160 characters, some restricted to 160 characters, some services allow longer – 190 charactersservices allow longer – 190 characters

Message goes from phone to SMSC – Message goes from phone to SMSC – short message service centreshort message service centre

Routes message to destination phone Routes message to destination phone when it becomes availablewhen it becomes available

Destination phone displays message on Destination phone displays message on screenscreen

MessagingMessaging

Most phones support text SMSMost phones support text SMS Many phones support the underlying data Many phones support the underlying data

protocol, can have other servicesprotocol, can have other services Can assume at most 140 bytes of data, Can assume at most 140 bytes of data,

also a header, determines how the data is also a header, determines how the data is interpreted by phoneinterpreted by phone

Could use different character sets, for Could use different character sets, for example Chinese – 70 charactersexample Chinese – 70 characters

MessagingMessaging

Service can send data to phoneService can send data to phone Bookmarks and service informationBookmarks and service information ImagesImages Musical tones (ring tones)Musical tones (ring tones) Business cardsBusiness cards

Anything that can be encoded as binary Anything that can be encoded as binary data can be sent to the phone, phone data can be sent to the phone, phone needs to understand the dataneeds to understand the data

MessagingMessaging

SMSC is maintained by phone company, SMSC is maintained by phone company, can connect to it from a PC or web servercan connect to it from a PC or web server

Messages can be sent to server to Messages can be sent to server to perform some action (a move in a game, perform some action (a move in a game, buy some item)buy some item)

Server can then send back a responseServer can then send back a response Programs downloaded to phone can also Programs downloaded to phone can also

do thisdo this

MessagingMessaging

MMS – Multimedia Messaging Service MMS – Multimedia Messaging Service uses higher bandwidth of 2.5G and 3G uses higher bandwidth of 2.5G and 3G networks to send larger messagesnetworks to send larger messages

Based on SMIL, can be used to send Based on SMIL, can be used to send media and synchronize its playbackmedia and synchronize its playback

Media includes images, sound, video and Media includes images, sound, video and text (with formatting information)text (with formatting information)

Played when it reaches phone, or stored Played when it reaches phone, or stored for later viewingfor later viewing

MessagingMessaging

MMSC serves similar purpose to SMSC, MMSC serves similar purpose to SMSC, stores messages and communicates with stores messages and communicates with phonesphones

Can send MMS content from a PC or a Can send MMS content from a PC or a web serverweb server

Can build your own service on top of MMS Can build your own service on top of MMS for games, movie previews or other for games, movie previews or other multimedia servicesmultimedia services