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Where Have All The Sine Waves Gone? David Waitt Kate Disney 2008 April Digitizing An Analog World.

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Presentation on theme: "Where Have All The Sine Waves Gone? David Waitt Kate Disney 2008 April Digitizing An Analog World."— Presentation transcript:

1 Where Have All The Sine Waves Gone? David Waitt Kate Disney 2008 April Digitizing An Analog World

2 Digital Television (DTV) Starting on 17 February 2009 Starting on 17 February 2009 New type of broadcasting that will allow better quality picture and sound New type of broadcasting that will allow better quality picture and sound More efficient use of the radio spectrum More efficient use of the radio spectrum The same radio spectrum can now be used for other applications The same radio spectrum can now be used for other applications Public Safety (Police, Fire)Public Safety (Police, Fire) Wireless dataWireless data Other communicationsOther communications GPS enhancementsGPS enhancements

3 Digital Television What do I need to do if I use a TV antenna and have an older television? What do I need to do if I use a TV antenna and have an older television? Need a converter box to convert the received digital signal into analog video and soundNeed a converter box to convert the received digital signal into analog video and sound Nothing is required if your television already has a Digital TV Tuner Nothing is required if your television already has a Digital TV Tuner

4 Digital Television Different levels of quality Standard Definition TV (SDTV) - SDTV is the basic level of quality display and resolution for both analog and digital. Transmission of SDTV may be in either the traditional (4:3) or widescreen (16:9) format. Enhanced Definition TV (EDTV) - EDTV is a step up from Analog Television. EDTV comes in 480p widescreen (16:9) or traditional (4:3) format and provides better picture quality than SDTV, but not as high as HDTV. High Definition TV (HDTV) - HDTV in widescreen format (16:9) provides the highest resolution and picture quality of all digital broadcast formats. Combined with digitally enhanced sound technology, HDTV sets new standards for sound and picture quality in television. (Note: HDTV and digital TV are not the same thing HDTV is one format of digital TV.)

5 DTV...More Info The National Telecommunications and Information Administration (NTIA) is administering the coupon program. For more information, visit the NTIA website at

6 Is Going Digital Enough? Simply digitizing information (Music, video, voice, pictures) for transmission is not enough to use the RF spectrum efficiently Simply digitizing information (Music, video, voice, pictures) for transmission is not enough to use the RF spectrum efficiently The information must be transmitted as efficiently as possible The information must be transmitted as efficiently as possible

7 Common Wireless Devices Today Cell phone Cell phone GSMGSM (850, 900, 1800, 1900 MHz)(850, 900, 1800, 1900 MHz) CDMACDMA (900, 1900 MHz)(900, 1900 MHz) Wireless (WiFi, ) Wireless (WiFi, ) (2400, 5100, 5800 MHz) (2400, 5100, 5800 MHz) Bluetooth Bluetooth (2400 MHz) (2400 MHz) -> How do these devices use the RF spectrum efficiently? -> How do these devices use the RF spectrum efficiently?

8 Getting From Here To There

9 The Cell site Cells are actually Covered by multiple cell sites. The cell sites operate on different frequencies so they do not interfere with each other within a given cell.

10 GSM – Global System for Mobile communications Time Division Multiplexing Time Division Multiplexing Cell site communicates with up to 8 phones on a single frequency for a short amount of time, Time Slot Cell site communicates with up to 8 phones on a single frequency for a short amount of time, Time Slot Each slot is Seconds Each slot is Seconds AT&T (Cingular), T- Mobile AT&T (Cingular), T- Mobile

11 CDMA – Code Division Multiple Access Phones are assigned codes that are embedded into the signal Phones are assigned codes that are embedded into the signal The cell site can distinguish between the different codes The cell site can distinguish between the different codes The number of phones communicating on a given frequency is determined by the Bit Error Rate The number of phones communicating on a given frequency is determined by the Bit Error Rate Verizon, Sprint Verizon, Sprint

12 IEEE A/B/G (WiFi) Typical wireless home router Typical wireless home router Several methods for varying the radio signal (modulation) Several methods for varying the radio signal (modulation) BPSK, QPSK, QAM BPSK, QPSK, QAM

13 QPSK Quadrature Phase Shift Keying Vary the phase of the radio signal to indicate one of four locations (0, 90, 180, 270 degrees) Vary the phase of the radio signal to indicate one of four locations (0, 90, 180, 270 degrees) Each star can represent 2 bits. Each star can represent 2 bits. Amplitude is constant Amplitude is constant

14 Higher Order Modulations 8 PSK 8 PSK 16 QAM (Quadrature Amplitude Keying) 16 QAM (Quadrature Amplitude Keying) The more stars in the constellation, the closer they will get to each other, and they will be more susceptible to interference, 256 QAM for very short communications linksThe more stars in the constellation, the closer they will get to each other, and they will be more susceptible to interference, 256 QAM for very short communications links

15 Bluetooth Most common use is Bluetooth headsets for use with cellular phones Most common use is Bluetooth headsets for use with cellular phones Frequency Hopping Spread Spectrum Frequency Hopping Spread Spectrum

16 Frequency Hopping 79 hopping channels 79 hopping channels Used in a random order Used in a random order seconds per frequency seconds per frequency

17 Why Frequency Hopping? If a few packets of data is lost due to interference, only a very small portion of the information is lost! If a few packets of data is lost due to interference, only a very small portion of the information is lost!

18 What Else Can Be Done What else can be done to encourage Frequency Re-Use? What else can be done to encourage Frequency Re-Use? This drawing shows very poor use of the radio spectrum. if this was a GSM cellular system with, 10 different frequencies, this system could accommodate 80 phones for the state of California

19 Reducing Coverage Area Reducing the coverage area of each cell site increases capacity, but costs more to deploy the network

20 Pico-Cells Pico-Cells increase capacity and improve frequency re-use Pico-Cells increase capacity and improve frequency re-use Cell site coverage will overlap, but on a different frequency. Sites using the same frequency are spaced further apart Cell site coverage will overlap, but on a different frequency. Sites using the same frequency are spaced further apart Some pico-cells are small enough to be located in office buildings in closets! Some pico-cells are small enough to be located in office buildings in closets!


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