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You and The Internet

You and The Internet Lecture 9 Mobile Networks Outline Basics of Wireless Communications Basics of Cellular Systems Evolution of Mobile Networks First Generation Second Generation 2.5 Generation Third Generation Objectives Understand the properties of wireless communications

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You and The Internet

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  1. You and The Internet Lecture 9 Mobile Networks IT1580 You and The Internet Dr Xiaowen Chu

  2. Outline • Basics of Wireless Communications • Basics of Cellular Systems • Evolution of Mobile Networks • First Generation • Second Generation • 2.5 Generation • Third Generation IT1580 You and The Internet Dr Xiaowen Chu

  3. Objectives • Understand the properties of wireless communications • Understand the fundamental principles of mobile networks • Describe the evolution of mobile networks IT1580 You and The Internet Dr Xiaowen Chu

  4. Wireless Communications • Wireless Communications • electromagnetic waves • carry information by systematically changing some property of the radiated waves, such as amplitude or frequency. • Wireless communications can be used for • Telegraph • AM and FM broadcast radio • Telephony • Video • Data communications • Satellite communications • Radar IT1580 You and The Internet Dr Xiaowen Chu

  5. Wireless Communications Are Important • April 14, 1912, RMS Titanic • Struck an iceberg and sank in North Atlantic • More than 700 passengers and crew on the lifeboats, waiting to be rescued • Titanic had a wireless system • Distress calls (求助信號) had been sending out • RMS Carpathia happened to know the distress calls from 93 km away. She arrived on the scene of the disaster several hours later and saved 705 people. Ref: http://www.titanic-titanic.com/carpathia.shtml IT1580 You and The Internet Dr Xiaowen Chu

  6. Electromagnetic Spectrum • Wireless signals can be used to carry information. • Frequency is an important property of wireless signals. • Ranges from 100 Hz to 1015 Hz 1MHz 1GHz 1KHz IT1580 You and The Internet Dr Xiaowen Chu

  7. Antennas • Wireless transmission and reception are achieved by means of an antenna(天線). • Antenna is a system used for radiating electromagnetic energy or for collecting electromagnetic energy. IT1580 You and The Internet Dr Xiaowen Chu

  8. Antenna • All antennas radiate some energy in all directions in free space • Omni-directional Antenna • radiates equally in all directions • Directional Antenna • radiates more in one direction than in the other IT1580 You and The Internet Dr Xiaowen Chu

  9. Ground-wave propagation Up to 2 MHz Can propagate a long distance E.g.: AM Radio Wireless Propagation Models The figure is from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  10. Sky-wave propagation 2 to 30 MHz Can propagate a very long distance: thousands of kms E.g.: international broadcasts such as BBC and Voice of America Wireless Propagation Models Ionosphere: 電離層 The figure is from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  11. Line-of-sight propagation above 30 MHz E.g.: FM radio, Cellular networks, WiFi, Microwave Antennas need to be high Wireless Propagation Models The figure is from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  12. Multipath Line-of-sight wireless signals are reflected by obstacles Multiple copies of the signal with varying delays are received Multipath The figure is from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  13. Wireless Transmission Characteristics • Attenuation • The strength of the signal falls off with distance • Noise • The received signal consists of the transmitted signal plus noise • Interference • If multiple transmitters send out signals with overlapped frequency bands, they will interfere with each other • Bandwidth: the width of frequency band • With more bandwidth, more information can be carried • Two conditions for good wireless communications • The received signal has sufficient strength • The received signal maintains a level sufficiently higher than noise IT1580 You and The Internet Dr Xiaowen Chu

  14. Satellite Communication The first artificial satellite was launched by the Soviet Union on 4 October 1957, which triggered the Space Race between the Soviet Union and the United States. The first artificial satellite launched by China was Dong Fang Hong I, in1970. The figures are from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  15. Satellite Communication Ref: http://www.af.mil/news/airman/0105/satil4b.shtml IT1580 You and The Internet Dr Xiaowen Chu

  16. Satellite Services • Satellite Internet access • terrestrial Internet access may not be available at some locations • Satellite phone • a type of mobile phone that connects to satellites instead of terrestrial base stations • Satellite radio • covers a much wider geographical range than terrestrial radio signals • Satellite television • television delivered by the means of satellite and received by a satellite dish • Satellite navigation • provide autonomous geo-spatial positioning with global coverage • E.g., GPS IT1580 You and The Internet Dr Xiaowen Chu

  17. GPS • GPS: Global Positioning System • developed by the United States Department of Defense • can be used freely for civilian applications • GPS receivers can determine their current location and the precise time • precision of civilian GPS is about 10-20m • GPS constellation • Currently a total of 24 satellites • http://upload.wikimedia.org/wikipedia/commons/9/9c/ConstellationGPS.gif • Signals from four satellites are required for normal operation • In downtown Hong Kong, GPS doesn’t work well. Why? IT1580 You and The Internet Dr Xiaowen Chu

  18. Cellular Network • Cellular technology is the foundation of mobile wireless communications. • Traditionally it was designed to support mobile voice telephony. • Mobile phone, or cell phone • 1G, 2G • Now it supports more applications, such as video phone and Internet access. • 2.5G, 3G, 3.5G IT1580 You and The Internet Dr Xiaowen Chu

  19. Cellular Network • Prior to the introduction of cellular radio, mobile radio telephone service was only provided by a high-power transmitter/receiver. • A typical system would support about 30 channels with an effective radius of about 80 km • The number of channels are limited by the allocated frequency bands • Service providers bid for the frequency bands from the government • Challenge: • how to increase the capacity? • As you will see, frequency bands are very expensive because they are scarce resources • Solution: • A cellular network! IT1580 You and The Internet Dr Xiaowen Chu

  20. Cellular Network • The great idea: Frequency Reuse • Using multiple low-power transmitters • Low-power can limit the range of the wireless transmission • Divide an area into cells, each one served by a base station (BS) • The base station has antennas and controller • Each cell is allocated a band of frequencies • Adjacent cells are assigned different frequencies to avoid interference IT1580 You and The Internet Dr Xiaowen Chu

  21. Cellular Network • An example of frequency reuse • There are 7 different frequency bands • Adjacent cells use different frequency bands • Two cells using the same frequency band are kept far way to avoid interference The cell radius can be as small as 100 meters, and as large as 20 km. The figure is from Ref [1]. IT1580 You and The Internet Dr Xiaowen Chu

  22. Mobile Switching Center Mobile Switching Center Public telephone network, and Internet Cellular Network Architecture • The Base Stations are connected to the Mobile Switching Centers, which are connected to the Public telephone network and the Internet. MS: Mobile Station BS: Base Station The figure is from Ref [2]. IT1580 You and The Internet Dr Xiaowen Chu

  23. First Generation • The first handheld mobile phone call was placed in 1973 on a prototype model • The Motorola DynaTAC 8000X was the first mobile phone to receive FCC acceptance in 1983 • The price was $3,995 in 1983 dollars • http://www.motorola.com/content.jsp?globalObjectId=7662-10811 http://en.wikipedia.org/wiki/Motorola_DynaTAC Dr. Martin Cooper of Motorola, made the first analog mobile phone call on a larger prototype model in 1983. IT1580 You and The Internet Dr Xiaowen Chu

  24. First Generation (1G) • AMPS: Advanced Mobile Phone Service • In 1980s, the most common system in North America, Australia, and China • From MS to BS: 824-849MHz • From BS to MS: 869-894MHz • Two operators (for competition), each get half of the bandwidth • Still in use today! • It uses separate frequencies, or "channels", for each conversation: FDM (Frequency Division Multiplexing) • Each channel requires 30 KHz • Each operator can have around 400 channels • Cellular technology is used to increase the number of customers! • Weakness • It is an analog standard • It is very susceptible to noise • It has no protection from eavesdropping IT1580 You and The Internet Dr Xiaowen Chu

  25. Second Generation (2G) • Beginning around 1990, 2G cellular systems were designed for voice communications with higher quality and greater capacity • 2G systems are digital systems: the cell phone converts an analog voice signal into digital format • Quality can be significantly improved • It is more secure because encryption is possible now • Two popular systems • GSM: Global System for Mobile Communications • IS-95 CDMA (or cdmaOne) IT1580 You and The Internet Dr Xiaowen Chu

  26. History of GSM • GSM was initiated for developing a pan-European mobile cellular radio system in 1982. • In 1985, West Germany, France and Italy signed an agreement for the development of GSM. The United Kingdom joined in the following year, and the group decided that digital technology would become the future of global wireless communication. • In 1991, a pilot GSM network was successfully demonstrated at the ITU’s Telecom exhibition in Geneva with around 11,000 calls made and no major problems encountered. • The real launch of GSM took place in the latter part of 1992 at a number of European countries. IT1580 You and The Internet Dr Xiaowen Chu

  27. History of GSM • In November 1995, American Personal Communications launched the first commercial GSM service in the US. • GSM is currently the most popular standard for mobile phones in the world • Based on GSM World statistics • "29% of the global population" • "82% of the global mobile market" • "850 new connections every minute" • Used by over 2 billion people across more than 212 countries and territories IT1580 You and The Internet Dr Xiaowen Chu

  28. GSM • Other features: • Roaming service • enables subscribers to use their phones in many parts of the world. • Short message service (SMS) IT1580 You and The Internet Dr Xiaowen Chu

  29. GSM • GSM networks operate in five different frequency ranges • Most GSM networks (including those in Hong Kong) operate in the 900 MHz or 1800 MHz bands • 900 MHz: 890 MHz – 915 MHz and 935 MHz – 960 MHz • The 25 MHz bandwidth is divided into 124 channels, each of 200 KHz (by FDM) • Each 200 KHz can support 8 full-rate speech by TDM • TDM (Time Division Multiplexing) • Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands • because the 900 and 1800 MHz frequency bands were already allocated. • 400 MHz is rarely used IT1580 You and The Internet Dr Xiaowen Chu

  30. GSM • Dual-band phone • operates either at GSM-900 and GSM-1800 (European standard), or GSM-850 and GSM-1900 (US standard) • Tri-band phone • operates on three of the four GSM frequencies. • is ideal for people who frequently travel • Quad-band phone • operates on four different GSM frequencies: typically, GSM-900, GSM-1800, GSM-850 and GSM-1900 • is more expensive IT1580 You and The Internet Dr Xiaowen Chu

  31. Identification • When a cell phone attempts a call, it needs to contact a BS. The BS can offer its service only if identifies the cell phone as a valid subscriber. • The cell phone stores the phone number, the personal identification number, and other information, in the SIM card • SIM: Subscriber Identity Module • the heart of a GSM phone • Without a SIM card, the cell phone is unusable IT1580 You and The Internet Dr Xiaowen Chu

  32. IS-95: CDMA • CDMA: code division multiple access • It permits several radios to share the same frequencies (but different from TDMA) • Advantages: • It can accommodate more users per MHz of bandwidth than other technologies • Cell size can be larger than GSM • Disadvantages: • Complicated system and technology • Most technologies are patented and must be licensed from Qualcomm • It only covers a smaller portion of the world , which is not good for global roaming IT1580 You and The Internet Dr Xiaowen Chu

  33. 2.5G • 2G systems are optimized for voice service and are not well adapted for data communications • 3G cellular technologies are designed to be appropriate for both voice and data communications • But it takes many years to be deployed • Need a transition from 2G to 3G: 2.5G • GPRS: General Packet Radio Service • EDGE: Enhanced Data Rates for Global Evolution • CDMA2000, Phase 1, or CDMA2000 1xRTT IT1580 You and The Internet Dr Xiaowen Chu

  34. 2.5G: GPRS • GPRS: General Packet Radio Service • Evolved from GSM • Before GPRS, the GSM cell phone can emulate a modem between the user device (such as a notebook) and the Internet. • The highest data rate is only 9.6 kbps (kilo bits per second) • With GPRS, some bandwidth resources used for voice will be allocated to data service • The data rate can be in the range of 40 kbps to 60 kbps • Charged based on the data volume • E.g., HK$500 for 30 Mbytes IT1580 You and The Internet Dr Xiaowen Chu

  35. 2.5G: EDGE • EDGE: Enhanced Data Rates for Global Evolution • Aims to increase the data rate of a GSM/GPRS network • Can be used for Internet connection, with data rate of 384 kbps • High-speed data applications such as video services are possible IT1580 You and The Internet Dr Xiaowen Chu

  36. Third Generation (3G) • 3G systems are required to provide voice service as well as data service with higher speeds than the 2G counterparts. • Capabilities of 3G systems • Voice quality comparable to the public telephone network • 144 kbps data rate in high-speed vehicles • 384 kbps data rate for walking speed • 2 Mbps for indoors IT1580 You and The Internet Dr Xiaowen Chu

  37. Third Generation (3G) • UMTS: Universal Mobile Telecommunications System • Popular in European • An evolution of the GSM • Several standards: • W-CDMA: wideband CDMA • TD-CDMA • TD-SCDMA • CDMA2000 • CDMA-2000 EV-DO • Evolution-Data Optimized • Popular in North America and part of Asia • An evolution of the IS-95 2G system IT1580 You and The Internet Dr Xiaowen Chu

  38. Third Generation (3G) • TD-SCDMA: Time Division-Synchronous Code Division Multiple Access • developed in China • an attempt not to be "dependent on Western technology” • other 3G formats require the payment of patent fees to a large number of western patent holders • In mainland China, networks using other 3G standards (WCDMA and CDMA2000 EV-DO) will be delayed until TD-SCDMA is ready. IT1580 You and The Internet Dr Xiaowen Chu

  39. 3G Licenses in UK The licenses will last for 20 years of commercial services. IT1580 You and The Internet Dr Xiaowen Chu

  40. 3G Licenses in Japan Three licenses granted in June 2000, with no fees. IT1580 You and The Internet Dr Xiaowen Chu

  41. 3G Licenses in Australia IT1580 You and The Internet Dr Xiaowen Chu

  42. 3G Licenses in Hong Kong • In 2001, four licenses have been issued, all are W-CDMA standard • Hong Kong CSL Limited: a company jointly owned by Telstra Corporation Limited (60%) and Pacific Century CyberWorks Limited (40%); • Hutchison 3G HK Limited: a company jointly owned by Hutchison Whampoa Limited (75%) and NTT DoCoMo Inc (25%); • SmarTone 3G Limited: a company wholly owned by SmarTone Telecommunications Holdings Limited; • SUNDAY 3G (Hong Kong) Limited: a company wholly owned by SUNDAY Communications Limited, and purchased by PCCW • In 2007: • PCCW won Hong Kong’s fifth 3G license: CDMA2000 IT1580 You and The Internet Dr Xiaowen Chu

  43. Subscriber Statistics From:http://www.gsmworld.com/news/statistics/pdf/gsma_stats_q1_07.pdf IT1580 You and The Internet Dr Xiaowen Chu

  44. Data Service: HSPA • HSPA: High-Speed Packet Access • extends and improves the performance of existing UMTS systems • Currently two standards: HSDPA and HSUPA • Another one, HSOPA, has been proposed • HSDPA: High Speed Downlink Packet Access • provides improved down-link performance, up to 14.4 Mbps • Sometimes called 3.5G • E.g., in Hong Kong, PCCW provides HSDPA up to 7.2 Mbps • HSUPA: High Speed Uplink Packet Access • provides improved up-link performance , up to 5.76 Mbps • HSOPA: High Speed OFDM Packet Access • currently under development • aims for maximum transfer rates of 100 Mbps for down-link, and 50 Mbps for up-link IT1580 You and The Internet Dr Xiaowen Chu

  45. Case Studies • SmarTone-vodafone • “Everything you do on the Internet, you can now do on your mobile“ • http://www.smartone-vodafone.com/jsp/mobile/prices/monthly_plans/tchinese/index.jsp • PCCW • Netvigator everywhere • http://www.netvigatoreverywhere.com/index_e.html • 3 Hong Kong • http://www.three.com.hk • CSL: • http://www.hkcsl.com/en/product_serivce/consumer.jsp • 1010 • one2free IT1580 You and The Internet Dr Xiaowen Chu

  46. Summary • Basics of Wireless Communications • Spectrum, antenna, wireless propagation models • Wireless transmission characteristics • Basics of Cellular Networks • The idea of frequency reuse • Mobile stations, base stations • First Generation • AMPS (FDM) • Second Generation • GSM (TDM), CDMA • 2.5 Generation • GPRS, EDGE • Third Generation • UMTS, CDMA2000 • 3G licenses • HSPA IT1580 You and The Internet Dr Xiaowen Chu

  47. Questions • What are the main functions of antenna? • What are the three wireless propagation models? • What are the wireless transmission characteristics? • How can cellular networks increase the system capacity? • Compare FDM with TDM. • Explain dual-band phone, tri-band phone, and quad-band phone. • Explain the functions of SIM card. • What are the advantages and disadvantages of CDMA? • What is GPRS? • What is EDGE? • What are the basic capabilities of a 3G system? • What is HSPA? • Compare the two standards of HSPA. IT1580 You and The Internet Dr Xiaowen Chu

  48. References • William Stallings, “Data and Computer Communications,”, 8th Edition, Prentice Hall, 2007. • James F. Kurose and Keith W. Ross, “Computer Networking, a Top-Down Approach,”, 4th Edition, Addison Wesley, 2007. IT1580 You and The Internet Dr Xiaowen Chu

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