《计算机网络》课程PPT教学课件（英文版）Chapter 4 物理层 PHYSICAL LAYER

PROTOCOL STACK Application Layer Transport Layer Network Layer 33卫 Link Layer Physical Layer CS5602: Principles and Techniques for Sensors and Information Perception

PROTOCOL STACK CS5602: Principles and Techniques for Sensors and Information Perception 1 Application Layer Transport Layer Network Layer Link Layer Physical Layer Power Management Plane Mobility Management Plane Task Management Plane

Chapter 4 PHYSICAL LAYER CS5602: Principles and Techniques for Sensors and Information Perception

CS5602: Principles and Techniques for Sensors and Information Perception 2 Chapter 4. PHYSICAL LAYER

PHYSICAL LAYER Source Source Codeword;ChannelChannel Codeword eNcoder Encoder Modulator Transmitte Application Phvsical Wireless Laver Laver Source I Source Codeword ChannelChannel Codeword Decoder Demodulator Decode 一一一一一一一一一一一一一 CS5602: Principles and Techniques for Sensors and Information Perception

CS5602: Principles and Techniques for Sensors and Information Perception 3 PHYSICAL LAYER

Source coding (data compression) At the transmitter end the information source is first encoded with a source encoder Exploit the information statistics Represent the source with a fewer number of bits → source codeword Performed at the application layer CS5602: Principles and Techniques for Sensors and Information Perception

Source coding (data compression) ▪ At the transmitter end, the information source is first encoded with a source encoder ▪Exploit the information statistics ▪Represent the source with a fewer number of bits, ▪→ source codeword ▪ Performed at the application layer CS5602: Principles and Techniques for Sensors and Information Perception 4

Channel coding (error control coding) Source codeword is then encoded by the channel encoder → channel codeword Goal: address the wireless channel errors that affect the transmitted information CS5602: Principles and Techniques for Sensors and Information Perception

Channel coding (error control coding) ▪ Source codeword is then encoded by the channel encoder ▪ → channel codeword ▪Goal: address the wireless channel errors that affect the transmitted information CS5602: Principles and Techniques for Sensors and Information Perception 5

Interleaving and modulation The encoded channel codeword is then interleaved to combat the bursty errors Channel coding and the interleaving mechanism help the receiver either to Identify bit errors to initiate retransmission Correct a limited number of bits in case of errors CS5602: Principles and Techniques for Sensors and Information Perception

Interleaving and modulation ▪ The encoded channel codeword is then interleaved to combat the bursty errors ▪ Channel coding and the interleaving mechanism help the receiver either to ▪Identify bit errors to initiate retransmission ▪Correct a limited number of bits in case of errors. CS5602: Principles and Techniques for Sensors and Information Perception 6

Interleaving and modulation Then, an analog signal (or a set thereof) is modulated 2 the digital information to create the waveform that b ill be sent over the channel Finally, the waveforms are transmitted through the antenna to the receiver CS5602: Principles and Techniques for Sensors and Information Perception

Interleaving and modulation ▪ Then, an analog signal (or a set thereof) is modulated by the digital information to create the waveform that will be sent over the channel ▪ Finally, the waveforms are transmitted through the antenna to the receiver CS5602: Principles and Techniques for Sensors and Information Perception 7

Wireless channel propagation The transmitted waveform travels through the channel Meanwhile, the waveform is attenuated and distorted by several wireless channel effects CS5602: Principles and Techniques for Sensors and Information Perception

Wireless channel propagation ▪ The transmitted waveform travels through the channel ▪ Meanwhile, the waveform is attenuated and distorted by several wireless channel effects CS5602: Principles and Techniques for Sensors and Information Perception 8

Information Processing Source stream Source codeword Channel codeword ource Channel 田图 Encoder Encode 图 Correlated bits 彐 Control bits 3 Parity bits CS5602: Principles and Techniques for Sensors and Information Perception

Information Processing CS5602: Principles and Techniques for Sensors and Information Perception 9

Wireless communication basics provides data and starts MAC protocol Transmission Data to be Transmitted ncode processing Start Symbol Transmission Encoded data to be transmitted MAC Delay Transmitting encoded bits durations几几几∏几L「 amples↑↑ttt+↑↑↑↑↑↑↑↑↑↑↑↑ Start Symbol Search Receiving individual bits Reception Start Symbol Detection Encoded data received Decode processing Data Received CS5602: Principles and Techniques for Sensors and Information Perception

Wireless Communication Basics CS5602: Principles and Techniques for Sensors and Information Perception 10