SM3121 Communications Technology Mark Green School of Creative Media

Introduction  Most mobile devices need to communicate  One of the main reasons for having them  Mobile phone isn’t very useful if you can’t call anyone!!  There are numerous communications systems that we can use, depend upon range and cost

Introduction  Technologies: Infrared: very local, but very cheap Infrared: very local, but very cheap Bluetooth: short range (10m), becoming widely available, fairly high speed Bluetooth: short range (10m), becoming widely available, fairly high speed Wireless Ethernet: medium range (100m or more), high speed, high cost Wireless Ethernet: medium range (100m or more), high speed, high cost Mobile phone network: long range, low speed, on most phones, quite expensive Mobile phone network: long range, low speed, on most phones, quite expensive  Need to know what to use and when

WiFi  Wireless Ethernet is the fastest wireless technology  Currently most are 11Mbps, but new ones are at 54Mbps  WiFi hardware standard on many new PCs  Becoming widely available in public places, coffee shops, universities, etc

WiFi  Two main components: Access point – AP, the interface between wireless and wired network, in control of the network Access point – AP, the interface between wireless and wired network, in control of the network Client – the hardware that runs on the mobile device Client – the hardware that runs on the mobile device  A client must connect to an AP before it can use the network

WiFi  A WiFi network can have a single AP, typical in homes  Could have multiple APs, need to coordinate APs as users move around the area  Don’t want user to know when they switch from one AP to another, shouldn’t cause a network disconnection

WiFi  Most WiFi systems use 2.4GHz radio band, this is divided into approximately 10 channels  AP and client must agree on channel to use  Newer clients and software can search channels for available APs, older ones not as smart

WiFi  This is a broadcast medium: You are sharing the bandwidth with everyone else on the AP You are sharing the bandwidth with everyone else on the AP In public areas will not see full 11Mbps bandwidth, could be much less than 1Mbps In public areas will not see full 11Mbps bandwidth, could be much less than 1Mbps Other clients see what you are sending and receiving Other clients see what you are sending and receiving Some attempt at security, but this can easily be broken Some attempt at security, but this can easily be broken

WiFi  Supports most Internet standards  Can do almost anything you can do with a standard PC  This is not always the case with the other communications technologies  In terms of equipment the most expensive technology, but bandwidth usage can be quite cheap

Hacking  WiFi can be very insecure, need to know what you are doing  Can have “open” AP, no security and anyone can use it  Sometimes the default for home systems, easier to set up  Some people look for open systems so they can steal bandwidth

Bluetooth  Originally developed to replace the wires in consumer devices  Short range, relatively high speed networking technology  Devices can be up to 10m apart, maximum bandwidth of about 1Mbps  Very complicated standard with a wide range of optional features

Bluetooth  Bluetooth uses the same frequency band as WiFi, so they can interfere  The Bluetooth standard is much more secure than WiFi and its easier for a group to share the bandwidth  Now becoming standard on many mobile devices, such as mobile phones and PDAs, relatively easy to add to PC

Bluetooth  Example: mobile phone and headset can use Bluetooth instead of wires  Bluetooth is not as complete as WiFi, it may not support any of the Internet standards  Could just be used for file transfers or simple data transfers, depending upon the devices used

Bluetooth  One of its strengths is discovery  a Bluetooth device can easily detect other devices nearby and automatically connect to them  Devices can easily move from one network to another and the connection is automatic  More flexible network organization

Bluetooth  Since Bluetooth is short range it can be used for location based services  Know that the other device is within 10m, can send information that is location dependent  Send business cards, advertisements, maps, tourist information, connect to vending machine for payment, etc

Infrared  Send information on infrared light signal  Very cheap technology, medium speed  Typically IR connections are around 100Kbps, but they can be faster  Need to be relatively close, typically less than 4m and cannot block light path  Used in remote controls, laptop computers, printers, etc

Infrared  Basically viewed as a serial connection, used for sending data  Could be used for Internet and other services, but would require considerable programming  Slowly being replaced by Bluetooth in mobile devices, only real advantage is price

Mobile Phone Network  This is a real mess: Too many standards, some poorly thought out and didn’t work Too many standards, some poorly thought out and didn’t work Bandwidth is quite low, except for 3G Bandwidth is quite low, except for 3G Bandwidth is very expensive Bandwidth is very expensive Little thought given to how it would actually be used and why people would pay for it Little thought given to how it would actually be used and why people would pay for it  We will try to make some sense out of this situation

Mobile Phone Network  Base technology is divided into generations  1G – the initial analogue mobile phone network, no longer used  Did not support data transmission in the phone itself, could use external modem for data, but usually limited to 9.6Kbps  Only voice services

Mobile Phone Network  2G – switch to digital, matches land lines which are also largely digital  Several standards, GSM is used in HK, available in most of the world  Supports data transmission, rates up to 9.6Kbps in standard systems  Start of data services, but not a major application or selling point

Mobile Phone Network  2.5G – basically 2G plus better data services, most HK networks are at this level  Adds GPRS (General Packet Radio Services), theoretically capable of 170Kbps  In HK GPRS seems to be limited to around 40 – 43 Kbps, but can get 56Kbps services at considerable extra cost

Mobile Phone Network  3G – for HK service introduced in 2004, initially one carrier, now up to three  Promises data speeds up to 2Mbps, don’t know whether this will be available locally  This high bandwidth may drop the cost of data services, currently 0.05 – 0.10 HK$ per Kbyte, very few unlimited usage plans, but they are very expensive

Mobile Services  There is a wide range of services built on top of the mobile phone network  Some of these services have been poorly designed, others have died very quickly  One solid standard would greatly help this part of the industry: Convince consumers to buy Convince consumers to buy Provide a standard for developers Provide a standard for developers

WAP  Wireless Application Protocol, there are two versions of this standard WAP 1 and WAP 2  These standards are quite different, both technically and philosophically  Consumers usually not aware of the difference, but its significant for developers  Market is moving to WAP 2

WAP 1  Want to bring web and related services to mobile phones  Set of standards that are parallel to web standards, but not the same  Assumption: mobile phones are different, so need a different set of standards  Very big mistake, cannot take content developed for web and move to phones

WAP 1  WML – Wireless Markup Language, similar to HTML, but not the same  Uses some of the same tags, but has different structure and new tags  Can use standard web servers with minor modifications, but content must go through a WAP gateway to convert to mobile phone format

WAP 1  Different browsers interpret WML differently, so content can look different on different phones  Similar to HTML situation in mid 1990s  Has simple form processing, tables, user interaction  Can use server side scripts to dynamically generate content

WAP 1  WMLScript – scripting language for WML  Sort of like JavaScript, but not quite the same  Many phone browsers don’t support it, but some do  Somewhat limited scripting language, not clear how useful it is

WAP 2  Totally different approach, try to stay as close to the web standards as possible  Use subset of HTML and CSS to maintain compatibility with standard web pages  Can be developed and tested using standard web tools  Should have more consistent appearance and behavior across a range of phones

WAP 2  Browser based on xHTML, the latest version of HTML  Special mobile profile developed for xHTML, along with CSS mobile standard  A number of new services being developed  Based on the standard Internet protocols, can add and other services

Messaging  One of the most popular mobile phone features  Started with SMS – Short Message Service, widely available, on most phones  Basically a fixed size chunk of data that can be exchanged between phones, or with a central service  Can have several formats

Messaging  Simplest format is English text, messages restricted to 160 characters, some services allow longer – 190 characters  Message goes from phone to SMSC – short message service centre  Routes message to destination phone when it becomes available  Destination phone displays message on screen

Messaging  Most phones support text SMS  Many phones support the underlying data protocol, can have other services  Can assume at most 140 bytes of data, also a header, determines how the data is interpreted by phone  Could use different character sets, for example Chinese – 70 characters

Messaging  Service can send data to phone Bookmarks and service information Bookmarks and service information Images Images Musical tones (ring tones) Musical tones (ring tones) Business cards Business cards  Anything that can be encoded as binary data can be sent to the phone, phone needs to understand the data

Messaging  SMSC is maintained by phone company, can connect to it from a PC or web server  Messages can be sent to server to perform some action (a move in a game, buy some item)  Server can then send back a response  Programs downloaded to phone can also do this

Messaging  MMS – Multimedia Messaging Service uses higher bandwidth of 2.5G and 3G networks to send larger messages  Based on SMIL, can be used to send media and synchronize its playback  Media includes images, sound, video and text (with formatting information)  Played when it reaches phone, or stored for later viewing

Messaging  MMSC serves similar purpose to SMSC, stores messages and communicates with phones  Can send MMS content from a PC or a web server  Can build your own service on top of MMS for games, movie previews or other multimedia services