Digital Communication Chapter 1: Introduction – ppt download

Presentation on theme: “Digital Communication Chapter 1: Introduction”— Presentation transcript:

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Digital Communication Chapter 1: Introduction
Fall 2011

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Elements of A Digital Communication System
Modulation/ Demodulation Channel Coding Source Coding Information Source Source Encoder Channel Encoder Digital Modulator Channel Digital Demodulator Channel Decoder Source Decoder Output Transducer Output Signal

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Information Source Analog Sources Digital Sources Voice, Video
Data Packet from Internet Discrete content in CD

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Source Coding Function Design Objective: Example
Convert the analog or digital information source to a bit sequence Remove redundancy in the information source Design Objective: Use minimum number of bits to represent the source with minimum distortion Example JPEG, MPEG, PCM, etc. Is introduced in a different course

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Channel Coding Function Design Objective Example
Add redundancy to achieve reliable communication Design Objective Use minimum redundancy to achieve maximum reliability To achieve larger coding gain Example Block Code, Convolutional Code, Turbo Code, LDPC Is introduced in a different course

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Modulation/Demodulaton
Function Map the bit sequence to signal waveforms suitable for channel transmission Design Objectives Design modulation schemes and signal waveforms to achieve the channel capacity Example BPSK, QAM, PSK, CPM  Single Antenna Space-Time Coding/Modulation  Multiple Antennas Is the main focus of this course

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Joint Source-Channel Coding
Information Source Source Encoder Channel Encoder Digital Modulator Channel Output Signal Output Transducer Source Decoder Channel Decoder Digital Demodulator Combine the source coding and channel coding to achieve better performance: Source Coding  Remove Redundancy Channel Coding  Add Redundancy Have found applications in speech and video transmission

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Coded Modulation Coded Modulation Information Source Source Encoder
Channel Encoder Digital Modulator Channel Output Signal Output Transducer Source Decoder Channel Decoder Digital Demodulator Combine the channel coding and modulation to achieve better performance: Channel Coding  Reduce the data rate (add redundancy) Modulation Improve the data rate (transmits more bits in a symbol) Have found wide applications Trellis Coded Modulation Bit-Interleaved Coded Modulation

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Channel Type of channels We cannot design the channel
Wireline Channel Fiber-optic Channel Wireless Channel Underwater Acoustic Channel Storage Channel We cannot design the channel One exception: Anechoic Chamber We can design source coding, channel coding, modulation etc. to achieve optimum performance for one particular channel.

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Layered Model Application Application HTTP, FTP, Email, VoIP, Video
Representation Representation Session Session Transport Transport TCP, UDP Network Layer Network Layer IPv4, IPv6 Data Link Data Link MAC, LLC Physical Layer Physical Layer Our Course Channel

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AWGN Channel Ideal abstraction channel model, mainly used in design and analysis Source of Noise Mainly from the electronic components and amplifiers at the receiver

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Band-Limited (AWGN) Channel
Bandwidth is limited by the linear filter Example Wireline Telephone Channel

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Fading (Band-Limited AWGN) Channel
A special case commonly used Example Wireless Channel

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Outline of The Course Deterministic and Random Signals TX Channel RX
Coded Bits Modulated Waveform Received Waveform To Decoder Modulation Schemes Chapter 3* Pulse Shaping Chapter 9 Diversity Techniques Chapter 14 AWGN Channel Chapter 3, 4 Band-Limited Channel Chapter 9, 10, Fading Channel Chapter 13,14 Detection Chapter 4 Synchronization Chapter 5 Equalization Chapter 10,13,14 *The Chapter number is based on the Fifth Edition of Proakis’ Book