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Wireless Digital Communication System

Wireless Communication is fundamentally the art of communicating information without wires. In principle, wireless communication encompasses any number of techniques including underwater acoustic communication, semaphores, smoke signals, radio communication, and satellite communication, among others.<br> Scientech Wireless Digital Communication System is an practical approach to wireless digital communication. This approach makes wireless more concrete, avoids simply drowning in mathematics and useful for graduate students as well. Students build a practical foundation for further study and good preparation for industry.

ManishJoshi
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Wireless Digital Communication System

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  1. Wireless Digital Communication System

  2. Wireless Digital Radio - SDR Wireless Digital Radio System -SDR

  3. Wireless Digital Radio - SDR “Life is beautiful if powered by Wireless Technology”

  4. Wireless Digital Radio - SDR Communication

  5. Wireless Digital Radio - SDR Communication “Communication is the process of transfer of information from a sender to a receiver who understands the message from the sender.”

  6. Wireless Digital Radio - SDR Block Diagram of Digital Communication System Input Transducer Source Encoder Channel Encoder Digital Modulator Input Signal Channel Output Transducer Source Decoder Channel Decoder Digital Demodulator Output Signal

  7. Wireless Digital Radio - SDR Software Defined Radio

  8. The SDR Forum defines the ultimate software radio (USR) as a radio that accepts fully programmable traffic and control information and supports a broad range of frequencies, air-interfaces, and application software. A good working definition of a software radio is a radio that is substantially defined in software and whose physical layer behavior can be significantly altered through changes to its software. Software defined radios are “radios that provide software control of a variety of modulation techniques, wideband or narrowband operation, communications security functions (such as frequency hopping), and waveform requirements of current and evolving standards over a broad frequency range”.

  9. Wireless Digital Radio - SDR Antenna SDR – Five Tire Definition Earphone Radio Frequency Modulation/ Demodulation Security, Digitization Signal Processing etc. Mouthpiece USR Tier 4 ISR Display/ Keyboard Tier 3 SDR Tier 2 SCR Tier 1 HR Tier 0

  10. Wireless Digital Radio - SDR Practical Model Smart Antenna Processing Channelization and Sample rate Conversion IF Output Flexible RF Hardware ADC • Software • Algorithms • Middleware • CORBA • Virtual Radio Machine • Hardware • FPGAs • DSPs • ASICs Input DAC Control

  11. Wireless Digital Radio - SDR Technical Parameters

  12. Compression, Error Correction, Encryption 011010100101 Wireless Digital Radio - SDR Data Bits to Symbol Symbol Mapping [Convert to Symbols] 011010100101 • Symbols are represented by the possible states of digital modulation. • Higher order modulation allows more bits per symbol. • What does that mean? Mapping symbols to I and Q. bit rate Symbol rate = the number of bits transmitted with each symbol

  13. Wireless Digital Radio - SDR Bandwidth • Bandwidth is a measure of the frequency content of a signal. • Bandwidth can be imagined as a frequency width. • Sort of the fatness of the signal. • Why Carrier signal BW is zero? • The more information in a signal, the larger the BW of the information signal. • The span of information frequency content is called BW. • Example:- Human Voice – Spans in frequency from 30 Hz to 10,000 Hz. www.scientechworld.com

  14. Wireless Digital Radio - SDR Message Bandwidth = W

  15. Wireless Digital Radio - SDR Transmission Bandwidth = 2W

  16. Wireless Digital Radio - SDR Shannon’s Theorem (1950’s) • Relates Bit Rate, Bandwidth, & Signal to Noise • Bit Rate = BW * log2(1 + SNR) • Bit Rate (Bits/Sec.) = BR • Signal bandwidth = BW • SNR = Signal to Noise Ratio • Bit Rate is limited by S/N • Symbol rate is a function of Bandwidth • Bit Rate / Symbol Rate is a function of signal complexity • Complex modulations optimize Bit Rates/BW • Higher BR/BW requires higher Signal to Noise • In a noiseless system • Infinite complexity and Bit Rate is theoretically attainable • Shannon Theoretical limit has never been reached • C grows linearly with B, but only logarithmically with S/N

  17. Wireless Digital Radio - SDR Filter Effect • Filtering allows the transmitted bandwidth to be significantly reduced without losing • the content of the digital data. This improves the spectral efficiency of the signal. • Any fast transition in a signal, whether it be amplitude, phase, or frequency, will • require a wide occupied bandwidth. • Any technique that helps to slow down these transitions will narrow the occupied • bandwidth. • Filtering serves to smooth these transitions (in I and Q). Filtering reduces • interference because it reduces the tendency of one signal or one transmitter to • interfere with another in a transmission system.

  18. Wireless Digital Radio - SDR Root-Raised Cosine Filters Time Domain Response of a Raised Cosine Filter Filter Bandwidth Parameters ()

  19. Wireless Digital Radio - SDR Filter Bandwidth Parameter – Alpha (Roll-off Factor) The sharpness of a raised cosine filter is described by alpha () or roll-off factor. Alpha gives a direct measure of the occupied bandwidth of the system and is calculated as: If the filter has a perfect (brick wall) characteristic with sharp transitions and an alpha of zero, the occupied bandwidth would be: In a perfect world, the occupied bandwidth would be the same as the symbol rate, but this is not practical. An alpha of zero is impossible to implement. Alpha is sometimes called the “excess bandwidth factor” as it indicates the amount of occupied bandwidth that will be required in excess of the ideal occupied bandwidth (which would be the same as the symbol rate). At the other extreme, take a broader filter with an alpha of one, which is easier to implement. An alpha of one uses twice as much bandwidth as an alpha of zero. In practice, it is possible to implement an alpha below 0.2 and make good, compact, practical radios. Typical values range from 0.35 to 0.5, though some video systems use an alpha as low as 0.11.

  20. Wireless Digital Radio - SDR Filter Bandwidth Parameter – Alpha (Roll-off Factor)

  21. EYE Diagram • Recovered Pulse must avoid the RED area • RED area is an error in the amplitude or time

  22. Wireless Digital Radio - SDR Link Budget Vacation Plan Mode : Railway with Sleeper Estimate : Rs 5000/- for hotel, restaurants, food etc. Watch money get spent at each stop. Get back to home : Still Rs 500/- left in your wallet Communication Link : Link budget Traveler : Signal Money : Power Travel : wire or wireless Credit Card along the way for extra money : Extra power using repeaters for telephone link & transponder in satellite link.

  23. Wireless Digital Radio - SDR Link Budget First Class Vacation Plan Mode : Flight Five star hotel, restaurants, food etc. Budget of Rs 5000/- will not be enough and possibly will need instead Rs 25000/-. Quality of the trip desired determines how much money we need to take along. With Signal, the quality is measured by the BER. If we want our signal to have a low BER, we would start it out with higher power.

  24. Wireless Digital Radio - SDR Modulation and its application

  25. Wireless Digital Radio - SDR

  26. Wireless Digital Radio - SDR

  27. Wireless Digital Radio - SDR

  28. Wireless Digital Radio - SDR

  29. Wireless Digital Radio - SDR

  30. Wireless Digital Radio - SDR

  31. “Life is beautiful if powered by Wireless Technology”

  32. Thank you For more details. Please visit www.scientechworld.com

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