Unit-1 Introduction to Wireless Communication Systems

1. Unit-1Introduction to Wireless Communication Systems

2. Introduction to Wireless Communication Systems “The ability to communicate with people on move” • In 1897, Guglielmo Marconi first demonstrated radio’s ability to provide continuous contact with ships sailing the English channel. • During the past 10 years, fueled by • Digital and RF circuit fabrication improvements • New VLSI technologies • Other miniaturization technologies (e.g., passive components) The mobile communications industry has grown by orders of magnitude. • The trends will continue at an even greater pace during the next decade.

3. Introduction to Wireless Communication Systems Wired Communications 1834 − Gauss and Weber build telegraph system in Germany 1844 − Morse connects Baltimore and Washington by telegraph 1858 − First transatlantic telegraph cable laid 1876 − Alexander Bell demonstrates telephone 1911 − New York can telephone Denver ♦ Wireless Communications → Not so “new” had slow growth at first compared to other inventions. But now is growing very rapidly.

4. Wired Vs. Wireless Communication Each cable is a different channel One media (cable) shared by all Highsignal attenuation Signal attenuation is low High interference noise; co-channel interference; adjacent channel interference No interference

5. Why go wireless ? • Advantages • Sometimes it is impractical to lay cables • User mobility • Cost • Limitations • Bandwidth • Fidelity • Power • (In) security

6. Wired and Wireless Home Networks • Wired home networks use coaxial cable, telephone wires, cat-5 wires, or the home’s electric power wiring. • Wireless home networks use radio signals.

7. Wired and Wireless Applications • Teleconferencing: • It is the simplest wired application for voice communication. • A telephone is used to conduct a conference between more than two people who are separated by a distance. • Videoconferencing: • Two or more people can have a face-to-face meeting when they are geographically separated. • Cameras, a computer, and videoconferencing software are used to conduct the conference.

8. Wired and Wireless Applications • Telecommuting: • Telecommuting is performing work at home while being linked to the office by telecommunications-equipped computers. • The advantages of telecommuting include not having to commute, flexible hours, more family time, and familiar surroundings. • Workgroup Computing: • A workgroup is a group of individuals, working together on a task, who are able to communicate and collaborate by way of computers connected to a network. • Groupware software is used by workgroups.

9. Electromagnetic radiation spectrum < 30 KHz VLF30K-300KHz LF 300KHz – 3MHz MF3 MHz – 30MHz HF 30MHz – 300MHz VHF 300 MHz – 3GHz UHF 3-30GHz SHF > 30 GHz EHF

10. ISM band 902 – 928 Mhz 2.4 – 2.4835 Ghz FM radio S/W radio TV TV AM radio cellular 5.725 – 5.785 Ghz VHF UHF SHF EHF LF MF HF  300MHz 30MHz 30GHz 300GHz 3GHz 3MHz 30kHz 300kHz  100mm 10cm 10m 1cm 1m 100m 10km 1km X rays Gamma rays visible UV infrared  1 MHz 1 GHz 1 kHz 1 THz 1 EHz 1 PHz Propagation characteristics are different in each frequency band EM Spectrum

11. Electromagnetic Specturm

12. Electromagnetic Specturm

13. Electromagnetic Specturm

14. Wireless Transmission Media Microwave Radio Infrared • Wireless transmission media refers to the methods of carrying data through the air or space using infrared, radio, or microwave signals.

15. Mobile Telephony, WLL MW Radio SW Radio Satellite Links FM Radio WLANs Blueooth IR Wireless Systems: Range Comparison 1 m 10 m 100 m 1 Km 10 Km 100 Km 1,000 Km

16. Infrared • Infrared is a wireless transmission medium that carries data via light beams. • Transmitter and receiver must be in line of sight. • An IrDa port is needed to use infrared with a computer.

17. Radio • Radio is a wireless transmission medium that carries data via radio frequency signals. • Wireless LANs in a home or business are one type of radio technology. • Radio signals can be long range (between cities or regions) and short range (within a building). • Radio signals are susceptible to noise and electrical interference.

18. Microwaves • Microwaves are high-frequency radio waves. • Much of long-distance telephone service is carried by microwaves. • Microwaves travel in a straight line. • Microwave relay stations are built about 30 miles apart.

19. Satellites • Satellites are microwave relay stations suspended in space. • They are positioned in geosynchronous orbits. • Satellites use microwave signals to transmit data to and from earth-based microwave relay stations.

20. Cellular Telephones • Cellular telephones enable calls to be placed through a wireless telecommunications system. • Cellular phones use radio or infrared signals. • Cells are limited geographic transmission areas. • A mobile telephone switching office (MTSO) monitors the signal strength of cellular phones.

21. Personal Communication Service (PCS) • Personal Communication Service (PCS) refers to digital cellular telephone service technologies. • Digital cellular phones offer: • Noise-free sound • Improved coverage • Protection from eavesdropping and phone fraud • Voice recognition • High-speed Internet access

22. Pagers • Pagers work like a simple radio. • Pagers are: • Constantly listening for a specific signal from a transmitter • Either one-way (only receive signals) or two-way (send and receive signals) • Declining in use due to the increase in cell phone use

23. Web-Enabled Devices • A web-enabled device is any device that can display and respond to HTML or XML. • PDAs, cell phones, and tablet PCs are web-enabled devices.

24. Facsimile (Fax) Transmission • Fax transmission is the means of sending an image of a document over telephone lines. • Fax modems support fax as well as data protocols.

25. TV Internet Set-Tops • Internet TV is an Internet service that uses a TV to: • Broadcast TV programs • Send and receive e-mail • Access Web sites • Navigate the Internet using a remote control

26. Electromagnetic Specturm • FCC controls all usable Radio Spectrum - allocates specific frequency bands for specific uses • Military • Public safety and public service - Police, fire, utilities, medical • Commercial - To customers, between commercial mobiles • Unlicensed • Amateur • Etc.

27. Electromagnetic Specturm • SMR Bands - Specialized Mobile Radio • Three 20 MHz bands from 800-900 MHz • Large number of radio system licenses nationwide • paging/messaging • voice dispatch - taxi, Police/Fire/Ambulance • data (UPS/Fedex) • Extended SMR • Nextel/Motorola partnership • Nationwide coverage providing digital cellular/data service • Created by buying SMR licenses from a large number of private radio service providers

28. Electromagnetic Specturm • ISM Bands - Industrial/Scientific/Medical • 902-928 MHz, 2400-2484 MHz, & 5725-5850 MHz • “Garbage” bands • spread spectrum modulation • Transmit (Tx) power level < 1 W • Remote meter reading • Wireless medical monitors • Digital cordless telephones • Big new application: Wireless Local Area Networks (WLAN’s)

29. Electromagnetic Specturm • Cellular Phone • AMPS: Advanced Mobile Phone System • 824-849 MHz • Reverse Channel: Transmit from mobile to fixed base station • 869-894 MHz • Forward Channel: Transmit from base station to mobile • FCC mandated duopoly in Major Trading Areas (MTAs) • MTA = 51 largest U.S. cities • two providers per MTA

30. Electromagnetic Specturm • Personal Communication Services(PCS) Band • 1.8-1.9 GHz • FCC Spectrum Auctions - $10 Billion!! • 1st time spectrum sold for $$ in U.S. • It is has been hard for companies to recover this investment • A & B blocks for Major Trading Areas (MTAs) • duopoly like AMPS • C, D, E, & F blocks - Basic Trading Areas (BTAs) • BTA = 492 large rural areas (includes MTAs) • Digital cellular phone service + PCS • PCS = special services like messaging, caller ID, voice mail, FAX, data, etc. • Compete with analog cellular and SMR services combined

31. Evolution of Mobile Radio Communications • Major Mobile Radio Systems • 1934 - Police Radio uses conventional AM mobile communication system. • 1935 - Edwin Armstrong demonstrate FM • 1946 - First public mobile telephone service - push-to-talk • 1960 - Improved Mobile Telephone Service, IMTS - full duplex • 1960 - Bell Lab introduce the concept of Cellular mobile system • 1968 - AT&T propose the concept of Cellular mobile system to FCC. • 1976 - Bell Mobile Phone service, poor service due to call blocking • 1983 - Advanced Mobile Phone System (AMPS), FDMA, FM • 1991 - Global System for Mobile (GSM), TDMA, GMSK • 1991 - U.S. Digital Cellular (USDC) IS-54, TDMA, DQPSK • 1993 - IS-95, CDMA, QPSK, BPSK

32. Evolution of Mobile Radio Communications

33. Mobile Radiotelephone in the U.S. • In 1934, AM mobile communication systems for municipal police radio systems. • vehicle ignition noise was a major problem. • In 1946, FM mobile communications for the first public mobile telephone service • Each system used a single, high-powered transmitter and large tower to cover distances of over 50 km. • Used 120 kHz of RF bandwidth in a half-duplex mode. (push-to-talk release-to-listen systems.) • Large RF bandwidth was largely due to the technology difficulty (in mass-producing tight RF filter and low-noise, front-end receiver amplifiers.) • In 1950, the channel bandwidth was cut in half to 60kHZ due to improved technology.

34. Mobile Radiotelephone in the U.S. • By the mid 1960s, the channel bandwidth again was cut to 30 kHZ. • Thus, from WWII to the mid 1960s, the spectrum efficiency was improved only a factor of 4 due to the technology advancements. • Also in 1950s and 1960s, automatic channel trunking was introduced in IMTS (Improved Mobile Telephone Service.) • offering full duplex, auto-dial, auto-trunking • became saturated quickly • By 1976, has only twelve channels and could only serve 543 customers in New York City of 10 millions populations.

35. Mobile Radiotelephone in the U.S. • Cellular radiotelephone • Developed in 1960s by Bell Lab and others • The basic idea is to reuse the channel frequency at a sufficient distance to increase the spectrum efficiency. • But the technology was not available to implement until the late 1970s. (mainly the microprocessor and DSP technologies.) • In 1983, AMPS (Advanced Mobile Phone System, IS-41) deployed by Ameritech in Chicago. • 40 MHz spectrum in 800 MHz band • 666 channels (+ 166 channels), per Fig 1.2. • Each duplex channel occupies > 60 kHz (30+30) FDMA to maximize capacity. • Two cellular providers in each market.

36. Mobile Radiotelephone in the U.S.

37. Mobile Radiotelephone in the U.S. • In late 1991, U.S. Digital Cellular (USDC, IS-54) was introduced. • to replace AMPS analog channels • 3 times of capacity due to the use of digital modulation ( DQPSK), speech coding, and TDMA technologies. • could further increase up to 6 times of capacity given the advancements of DSP and speech coding technologies. • In mid 1990s, Code Division Multiple Access (CDMA, IS-95) was introduced by Qualcomm. • based on spread spectrum technology. • supports 6-20 times of users in 1.25 MHz shared by all the channels. • each associated with a unique code sequence. • operate at much smaller SNR.(FdB)

38. Mobile Radio Systems Around the World

39. Mobile Radio Systems Around the World

40. Mobile Radio Systems Around the World

41. Example of Mobile Radio Systems • Examples • Cordless phone • Remote controller • Hand-held walkie-talkies • Pagers • Cellular telephone • Wireless LAN • Mobile - any radio terminal that could be moved during operation • A cellular telephone in a fast moving vehicle • Portable - hand-held and used at walking speed • A walkie-talkie or cordless telephone inside a home • Subscriber - mobile or portable user

42. AM, FM Radio TV Broadcast Satellite Broadcast 2-way Radios Cordless Phones Satellite Links Mobile Telephony Systems Wireless Local Loop (WLL) Microwave Links Wireless LANs Infrared LANs Broadcast (analog) Wireless Systems: Examples 2-way communication (analog) 2-way communication (digital)

43. Mobile Radio Terminology • Mobile: high speed motion (e.g. cell phone in car) • Portable: low speed motion (cordless phone in home, walking) • Mobile Unit = subscriber unit = user communication device • Transmitter (Tx) and Receiver (Rx) • Base Station: Tx/Rx on tower at center of cell that provides service to group of mobile users

44. Wireless Communication System Definitions

45. Example of Mobile Radio Systems • Classification of mobile radio transmission system • Simplex: communication in only one direction • Half-duplex: same radio channel for both transmission and reception • (push-to-talk) • Full-duplex: simultaneous radio transmission and reception (FDD, TDD) • Frequency Division Duplexing uses two radio channel • Forward channel: base station to mobile user • Reverse channel: mobile user to base station • Time Division Duplexing shares a single radio channel in time.

46. Duplex Communication Base Station B • FDD: Frequency Division Duplex Mobile Terminal M Forward Channel Reverse Channel Forward Channel and Reverse Channel use different frequency bands • TDD: Time Division Duplex Base Station B Mobile Terminal M M B M B M B A singe frequency channel is used. The channel is divided into time slots. Mobile station and base station transmits on the time slots alternately.

47. Example of Mobile Radio Systems • In FDD • a device, called a duplexer, is used inside the subscriber unit to enable the same antenna to be used for simultaneous transmission and reception. • to facilitate FDD, it is necessary to separate the XMIT and RCVD frequencies by about 5% of the nominal RF frequency, so that the duplexer can provide sufficient isolation while being inexpensively manufactured. • Used in analog mobile radio systems • In TDD • only possible with digital transmission format and digital modulation. • very sensitive to timing. Consequently, only used for indoor or small area wireless applications.

48. Paging Systems • Conventional paging system send brief messages to a subscriber • One-way communication (SX) • Send short message to mobile unit (pager) • Wide area coverage • Page broadcast from many base stations simultaneouslyto remote units no information as to user location • Modern paging system: news headline, stock quotations, faxes, etc. • Simultaneously broadcast paging message from each base station (simulcasting) • Large transmission power to cover wide area.

49. Paging Systems • Reliable communication everywhere (need good Signal to Noise performance) • Requires large Tx power and low data rate (~ 2-8 kbps) • Noise has less of an effect when the data rate is lower. • Coverage needed even inside buildings w/ 20-30 dB signal attenuation • Needs an extensive network of transmitters to transmit the signal everywhere • Paging receivers are simple and inexpensive, but the transmission system required is quite sophisticated. • Designed to provide ultra-reliable coverage, even inside buildings • Buildings can attenuate radio signals by 20 or 30 dB, making the choice of base station locations difficult for the paging companies. • Small RF bandwidths are used to maximize the signal-to-noise ratio at each paging receiver, so low data rates (6400 bps or less) are used.

50. Paging Systems