Internet of Things Communication-Final Review

Chapter 0: Overview

1: The framework of the Internet of Things

Perception control layer

• 1.Data collection sublayer:
    The types of sensing equipment mainly include: various sensors, RFID, multimedia information collection devices, barcode (one-dimensional, two-dimensional barcode) recognition devices and real-time positioning devices, etc.
• 2.Short-range communication transmission sublayer：
    Mainly include: short-distance wired data transmission system (usb), wireless transmission system (infrared, bluetooth), wireless sensor network
• 3.Cooperative Information Processing Sublayer:
    Mainly include: information aggregation system, information collaborative processing system, middleware system and transmission gateway system, etc.

Network transport layer

The transmission to the application layer through various bearer networks
mainly includes mobile communication networks, fixed communication networks, the Internet, radio and television networks, and satellite networks.

Application layer (the highest level of the framework of the Internet of Things)

• 1.Service support layer: Information collaboration, information processing, information sharing, information storage, etc. for various industry applications (public information service platform)
• 2.Industry application layer: For applications such as environment, power, intelligence, industry, agriculture, home furnishing, etc.

Running through these 3 levels isCommon support layer, To ensure the safe and effective progress of the Internet of Things

2: The basic structure of the Internet of Things communication system

Perception control layer communication system

• purpose: Transmit the information sensed by various sensing devices to the information aggregation system within a short communication distance, and then transmit (or interconnect) the system to the network transmission layer.
• Features: Short transmission distance, flexible and diverse transmission methods

Network transport layer communication system

• Main composition：Data communication host (or server), network switch, router, etc.

Chapter 1: Basic Model and Concept of Communication System

1: Analog communication system model

The original signal contains low-frequency components that are not suitable for channel transmission due to other components.
Modulator: The original electrical signal is transformed into a suitable channel transmission signal.
Demodulator: The appropriate channel transmission signal is transformed into the original electrical
signal. Modulated signal: The modulated signal is called a modulated signal.

• The modulated signal has two basic characteristics: one isCarry message, ButSuitable for channel transmission

2: Communication method

1) According to transmission direction and time:

• Simplex: Messages can only be transmitted in one direction
• Half duplex: Both communication parties can send and receive messages, but they cannot send and receive messages at the same time. Messages need to be sent and received separately (e.g., walkie-talkie)
• Duplex communication: Both communication parties can send and receive messages at the same time

2) According to the transmission sequence of digital symbols:

• Kushiyuki communication：It means that the symbols of the digital signal are transmitted in the channel one by one in chronological order
• Parallel communication: Divide the digital symbols into two or more digital signal symbol sequences for simultaneous transmission in multiple channels

3: Signal and semaphore

4: Main performance indicators in data communication systems

Transmission rate

Symbol transmission rate (R _B ), information transmission rate (R _b )

Error rate

Signal-to-noise ratio

Combined channel capacity test

Chapter 3: Channels in Data Communication

Channel capacity

Chapter 4: Source Coding

sampling:

Discretization of analog signals in the time domain is to transform a time-continuous and continuous signal into a time-discrete and continuous-amplitude signal. (Analog -----> Digital Process)
Sampling Theorem (Band Pass Sampling Theorem):

Quantification:

Requirements: understand the concept. Comparison and concept of uniform and non-uniform quantification.

Topic 1:

Chapter 5: Digital Baseband Transmission

Requirements: drawing

Waveform of digital baseband signal

Unipolar code

• The presence or absence of pulse means "1" and "0", and the pulse width is equal to the symbol width

Bipolar code

• The positive and negative pulses represent "1" and "0", and the pulse width is equal to the symbol width

Unipolar return to zero code

• The presence or absence of pulse means "1" and "0", the pulse width is less than the symbol width, and the rest of the less than the symbol must return to 0 level

Bipolar return-to-zero code

• The positive and negative pulses indicate "1" and "0". The pulse width is smaller than the symbol width, and the rest of the pulse width is smaller than the symbol width to return to 0 level.

Differential coding

• Level jump means "0", level unchanged means "1"

Multi-level code (multi-ary code)

For example: -3V represents 00, -1V represents 01, +1V represents 10

Chapter 6: Digital Modulation System

Digital amplitude modulation (ASK)

Features: simple circuit and poor noise immunity.
Currently
, the most widely used applications are: FSK and PSK ASK classification: binary 2ASK and multi-system ASK
2ASK:

• When there is carrier output, it means sending "1", when there is no carrier output, it means sending "0"
• Modulation method: direct multiplication method, amplitude shift keying method
• Demodulation method: envelope demodulation method, coherent demodulation method

Digital phase modulation

Binary absolute phase shift modulation (2PSK)

1:2PSK modulation

• Direct phase modulation and phase shift keying

2: 2PSK demodulation

• Coherent demodulation method

Chapter 7: Error Control Technology

Cyclic code

Question type: code polynomial and code group conversion

Chapter 8: Data link transmission control procedures

HDLC frame structure

A complete HDLC frame includes the flag field (F), address field (A), control field (C), information field (I), frame check field (FCS), etc. The
flag field is composed of
a unique 01111110 8 bits are delimited at both ends of the frame, indicating the start of the frame and the end of the previous frame

Chapter 9: Short-distance wired communication technology

RS-232C: 9-pin structure

IEEE-1394 interface

Another interface standard similar to the USB interface is IEEE-1394, which has a faster transfer rate, more flexible and convenient than USB, but its cost is higher.
The applications of USB and IEEE-1394 are different.

• USB is suitable for use on medium, high and low speed devices such as keyboards, mice, scanners, mobile hard drives and printers
• IEEE-1394 is suitable for the connection of video or other high-speed systems and occasions where there is no host

Week 10: Short-range wireless communication technology

Bluetooth technology

• Features: low power consumption, high communication rate, short transmission distance, unlimited working frequency band, high reliability, short communication distance, flexible networking, automatic search, low cost, mature technology, and wide application range
• Bluetooth physical channel uses multi-frequency (HF) and division multiple access (TDMA) technology

Chapter 12: IEEE802.15.4 and ZigBee protocol specifications

ZigBee three topological structures: star, mesh and hybrid network topologies

IEEE802.15.4 physical layer:

Chapter 22: Propagation Characteristics and Multiple Access Technology

Frequency division multiple access technology and time division multiple access technology:

• Frequency division multiple access technology (FDMA): the difference in the carrier frequency of the transmission signal
• Time Division Multiple Access (TDMA): The transmission signal exists at different times

Code Division Multiple Access Technology—Frequency Hopping Code Division Multiple Access (FH-CDMA):