Internet of Things review summary

Summarize the main points that the teacher said (there may be omissions)
mark * as sure

Chapter 1 Overview of Internet of Things

1. Important Features*

Ordinary objects are equipment-based, autonomous terminals are interconnected, and ubiquitous services are intelligentized

2. Four layers of IoT*

(1) Perceptual recognition layer

Information generation
GPS, RFID, sensors

The diversification of information generation methods is an important feature that distinguishes the Internet of Things from other networks

(2) Network construction layer

Information transmission
WLAN, MAN, WAN, Internet

(3) Management service layer

Information processing
Data center, search engine, intelligent decision-making, information security, data mining

(4) Comprehensive application layer

Information application
Intelligent logistics, smart grid, green building, intelligent transportation, environmental monitoring

3. Main features

Large-scale networked terminals, universal perception and recognition, interconnection of heterogeneous devices, intelligent management and control, and chain-based application services

Chapter 2 Perceptual Recognition

1.RFID

It is wireless radio frequency identification technology, also known as non-contact radio frequency identification technology, through radio frequency signal and space coupling, realizes non-contact information transmission and achieves the purpose of automatic identification through the transmitted information

2. Three major components of RFID*

Reader (transmitter, receiver, microprocessor), antenna, tag
Principle: The reader sends an electronic signal through the antenna, and the tag transmits the identification information stored in the internal storage after receiving the signal, and the reader receives and identifies the information sent back by the tag through the antenna, and finally the reader sends the identification result to the host

3. Classification of RFID tags

Passive tags, active tags, semi-active tags

4. Features of RFID tags

Small and diverse, environmental resistance, reusable, strong penetrability, data security

5. RFID frequency*

(1) low frequency

30~300kHz
Wavelength 2500 meters, communication range is generally less than 1 meter
Low transmission rate, high cost
Such as car keyless door opening, access control, automatic parking lot

(2) High frequency

3~30MHz
wavelength is 22 meters, and the communication range is generally less than 1 meter,
such as book management system, clothing production line, logistics system

(3) UHF

300MHz~3GHz
Wavelength 30cm, the communication range is generally greater than 1 meter, the maximum is 10 meters
Can not pass through many materials
Fast transmission rate
Such as production line automation, container management, air/railway parcel management

Supplementary barcode

• Features of one-dimensional barcode:
  It can directly display English, numbers, and simple symbols; there
  is not much data stored, mainly relying on the associated database in the computer;
  the confidentiality performance is not high; the readability
  is poor after contamination.

• Two-dimensional barcode features:
  it can directly display English, Chinese, numbers, symbols, and graphics; it can
  store a large amount of data, which can store 1K characters, and the content can be read directly by a scanner without connecting to a database; it has
  high confidentiality (can be encrypted);
  when the security level is the highest, the complete information can still be read even if it is 50% damaged.

Chapter 3 Wireless Sensor Network

1. Sensor

• A device or device that can sense what is being measured and convert it into a usable output signal according to certain rules
• Sensors are an important means of information acquisition, and communication technology and computer technology constitute the three pillars of information technology
• The hardware components of wireless sensor network nodes include sensors, microprocessors, communication chips and energy supply devices.

2. Limitations of traditional sensors

Limited degree of networking and intelligence

3. Modern sensor development

Miniaturization, intelligence, networking

4. Common sensors*

Visible light sensor
Temperature sensor
Humidity sensor
Pressure sensor
Magnetic sensor
Acceleration sensor Acoustic sensor
Smoke sensor Passive infrared
sensor Synthetic light sensor Soil moisture sensor

5. The processor interacts with the sensor through analog and digital signals

6.CC2420*

ZigBee
works in the 2.4GHz channel
Packet-based communication chip, which can automatically judge the start and end of the data packet
IEEE 802.15.4

7. ETC

Select the path with the minimum transmission cost
The sum of 1/receiving rate of each segment of the path

8. Development Prospects of the Internet of Things*

(1) Low cost and miniaturization

Prerequisites for mass deployment

(2) Low power consumption

Prerequisites for long-term deployment

(3) Flexibility and scalability

An important guarantee for large-scale deployment

(4) Robustness

An important guarantee for long-term deployment
More communication methods (ZigBee, LoRa, NB-IoT)

Chapter Four System Orientation

1. Three elements of location information*

The geographic location (spatial coordinates), the time at the geographic location (time coordinates), the object (person or device) at the geographic location (identity information)

2. Three parts of GPS*

satellite navigation system

(1) Space part

(2) Ground monitoring part

(3) User equipment part

3. Basic operating principle of GPS*

• First measure the distance between the receiver and three GPS satellites, and then determine the position of the receiver by three-point positioning

4. Advantages and disadvantages of GPS

• Advantages
  High accuracy
  Global coverage for use in harsh environments

• Cons
  Long startup time
  Poor signal indoors
  Requires GPS receiver

5. Cellular base station positioning

Using the conditions of known base station location , the communication equipment can be positioned

(1) Single base station positioning method

• COO positioning

The location of the base station to which the mobile device belongs is regarded as the location of the mobile device.
The accuracy directly depends on the coverage area of ​​the base station
. In areas where base stations are loosely distributed, the coverage radius of a base station can reach several kilometers, and the error is huge.

Advantages: simple, fast, suitable for emergencies

(2) Multi-base station positioning method

• ToA/TDoA positioning method

Measure the propagation time of wireless signals.
Three base stations are required to locate.
In sparse areas, only two base stations may be received. Not applicable

• AoA positioning method

Measure the direction of propagation of wireless signals
Requires two base stations

6. Advantages and disadvantages of cellular base station positioning

• Advantages
  No need for GPS receiver, positioning can be done through communication
  Fast startup speed
  Strong signal penetration ability, can also be received indoors

• Disadvantages
  Relatively low positioning accuracy
  The base station needs special hardware, which is expensive

7. Indoor precise positioning*

Use known location nodes to calculate the location to be requested. The
indoor GPS signal is weak, and the base station positioning is affected by many aspects and the effect is not good.

Most of the existing ones are based on RSS (using signal strength)

Including infrared positioning, ultrasonic positioning, WI-Fi positioning, Bluetooth positioning, radio frequency identification positioning, ultra-wideband positioning, ZigBee positioning

8. Common positioning methods:

• Positioning based on distance (time) (Time of Arrival, ToA)
• Positioning based on distance (time) difference (Time Difference of Arrival, TDoA)
• Positioning based on signal characteristics (Received Signal Strength, RSS)

9. Distance (time) based positioning*

Measure the physical quantity and determine the position of the target according to the measured physical quantity

(1) Distance measurement method

Using electromagnetic waves and sound waves to measure, assuming that they are sent out at the same time

d=vs(ts-tr)
vs: the speed of the sound wave, ts: the time when the sound wave is received, tr: the time when the electromagnetic wave is received

or measure the round-trip time of a wave

d=v(t-t0-△t)/2

(2) Position calculation method

Multi-point measurement method
Take three reference points as the center of the circle, draw a circle with the distance from the target to the center of the circle as the radius, and the intersection point of the three circles is the target position
In practice, more than three reference points are used, and the least square method reduces the error

10. Positioning based on distance difference

• Limitations of ToA
  Requires reference point and measurement target clock synchronization (synchronization algorithm!!??)

• TDoA
  does not require reference point and measurement target clock synchronization
  Clock synchronization is still required between reference points

(1) Distance measurement method

Measure target broadcast signal
Reference point i, j respectively record the moment when the signal is received,
measure the distance difference between the target and i, j

(2) Position calculation method

Solve simultaneous equations with at least two sets of data,
actually use the least squares method for multiple sets of data to solve

11. Positioning based on signal features

• Positioning based on signal strength ranging directly uses radio frequency signal positioning of wireless communication, no additional equipment is required
• Principle: Signal strength attenuates with propagation distance
• Problem: The ideal formula is difficult to apply in practice
• Solution: Treat signal strength features as "fingerprints". Disadvantage: Cannot cope with dynamic changes

12. Future challenges

• Network heterogeneity
• Changeable environment
• Information Security and Privacy Protection
• large scale application

13. Free space loss

Chapter 5 Internet and Mobile Internet

1. In the Internet, the interconnection channels of various terminals are mainly composed of communication links and data exchange equipment.

2. The development history of the Internet

• 1960s to 1970s: Evolution of data exchange strategies
• 1970s and 1980s: Transformation of private networks and Internet technologies
• 1980s to the Present: The Expansion and Explosion of the Internet

3. Mobile communication

• First Generation Mobile Communications: Analog Voice
• The second generation of mobile communication: digital voice
  The second generation of mobile communication technology: digital system
• Third Generation Mobile Communications: Digital Voice and Data
• The fourth generation of mobile communication: multimedia mobile communication 4G
• The fifth generation of mobile communication: IoT and intelligence

4.CDMA

• Coding techniques can be used to distinguish and separate multiple simultaneously transmitted signals
• CDMA2000 is commonly used in my country

There are still a few days to take the exam, don't be in a hurry, if you can't be in a hurry, just remind me to change it, to be continued. . .

Chapter 6 Wireless Access

1. Basic composition elements

• wifi user
• base station
• Wireless connections

2. Features

• Signal Strength Attenuation
  The wireless signal energy decreases as the transmission distance increases.
• Non-line-of-sight transmission
  If the path between the sender and receiver is partially blocked, it is called non-line-of-sight transmission.
  Wireless signals may be absorbed or rapidly attenuated by obstructions.
• Signal Interference
  Signals in the same wireless frequency band, such as 2.4GHz, will interfere with each other.
  Electromagnetic noise from the external environment, such as microwave ovens, cars, high-voltage power lines.
• Multipath Propagation
  Due to the reflection and refraction of obstacles, wireless signals may arrive at the receiving end at slightly different times.
• Hidden Terminal problem
  Unaware of mutual interference

3.Wi-Fi（IEEE802.11）

• The Basic Service Set (BSS) is the most important part of the 802.11 architecture.
  base station mode
• Wireless users (laptops, PDAs, desktops, etc.): Obtain upper-layer network data by associating with an access point.
  Access point (base station): connected to the upper public network through a wired network device (switch/router). A "wireless router" is a combination of access point and router functions.
• Self-organization mode
  Wireless users: Each wireless network user is not only a terminal for data interaction but also a route during data transmission.

4.CSMA/CA

• Carrier Sense Multiple Access Protocol with Collision Avoidance
• The user listens to the channel before sending data, and if the channel is occupied, no data is sent.
• Mechanism of RTS and CTS to avoid "hidden terminal" problem

Sender:
Use CSMA/CA to send RTS to access point
Access point:
Broadcast CTS
User who receives CTS:
RTS sender sends data
Other users delay their transmission

5. Reasons for not adopting CSMA/CD

• Collision detection (CD) requires full-duplex (transmitting data and receiving data at the same time), the hardware cost is too high, and it is difficult for the wireless network card to receive conflict detection frames and send wireless signals at the same time.

• The attenuation characteristics of wireless signals and the problem of hidden terminals make collisions difficult to detect

6.802.11 three address fields

The three address fields (address 1-3) play a vital role in the data exchange between the wireless basic service group and the upper layer network, and are used for the conversion of the address field in the 802.11 data frame and the Ethernet data frame format.

7. Bluetooth

• IEEE 802.15.1 standard
• The frequency range is 2.402GHz-2.480GHz
• Original Bluetooth: long time to establish connection, high power consumption, low security
• 4.0 features
  A master device can communicate with up to seven slave devices at the same time
  The communication distance is also increased to more than 100 meters, and the communication rate reaches 24Mbps,
  including high-speed Bluetooth, classic Bluetooth and Bluetooth low energy
  consumption Low power consumption, low latency, suitable for App Store mode

8.ZigBee

• IEEE 802.15.4 standard
• Can work in 3 frequency bands: 2.4GHz (popular in the world), 868MHz (popular in Europe) and 915MHz (popular in the United States)
• Features: low power consumption, low cost, short delay, large network capacity, reliable and safe
• 3 frequency bands
• Using Carrier Sense Multiple Access (CSMA/CA)
• MAC layer design: how to reduce energy consumption? Sample Listening and Scheduling

9. Comparison of different protocols

• Communication distance, communication bandwidth and communication energy consumption restrict each other.
  

Chapter 7 Internet of Things and Big Data

1. Big data 4v features

• Large quantity (Volume)
• Variety
• Fast (Velocity)
• Low value (Value)

2. Network storage

• Directly attached storage DAS
  is easy to manage and has a simple structure; the centralized system structure cannot meet the needs of large-scale data access; the utilization rate of storage resources is low, and the ability to share resources is poor, resulting in "information islands".
• The storage entity of the network attached storage NAS
  network is easy to realize file-level sharing; the performance is heavily dependent on the network traffic, the number of users is too large, and the performance is limited when reading and writing are too frequent.
• Storage area network SAN
  simplifies storage management and improves storage capacity utilization; there is no direct file-level access capability, but a file system can be established on the basis of SAN.

3. Data center

• Google File System
• MapReduce
• BigTable
• Hadoop
• HDFS

4. Reduce data center costs

• The key to improving server utilization is to respond to dynamic changes in demand in a timely manner
• New data center network structure
• Reduce server energy consumption
• Reduce cooling system energy consumption

Chapter 8 Cloud Computing

1. Service level

• Infrastructure as a Service (IaaS)
• Platform as a Service (Platform as a Service, PaaS)
• Software as a Service (SaaS)

2. Virtualization level

Chapter 9 Information Security and Privacy Protection in the Internet of Things

1. General indicators

• Reliability: three measures (insurgency, survival, effective)

• Availability: Measured by the ratio of normal service time to overall working time

• Confidentiality: Commonly used confidentiality technologies (anti-interception, radiation protection, encryption, physical confidentiality)

• Integrity: Information cannot be changed without authorization; difference from confidentiality: Confidentiality requires information not to be disclosed to unauthorized persons, while integrity requires information not to be destroyed for various reasons.

• Non-repudiation: the property that participants cannot deny completed operations and commitments

• Controllability: control over information dissemination and content

2. Privacy

• Right to privacy: the right to self-determination of personal information, including personal information, body, property or self-determination.
• IoT and Privacy
  Misuse can compromise privacy
  Right technology can protect privacy

3. The main safety hazards of RFID

• tapping
• man-in-the-middle attack
• spoof, replay, clone
• denial of service attack
• physical crack
• falsification of information
• RFID virus
• Other hidden dangers
  Electronic sabotage
  Shielding interference
  Demolition

4. Major Privacy Issues

• Leakage of private information
  Name, medical records and other personal information
• Tracking
  and monitoring, mastering user behavior rules and consumption preferences, etc.
  further attack

5. Location Privacy

• Users' ability to control their own location information
• Three elements: time, place, person
• Threat
  Communication
  Service Provider
  Attacker

6. Means of Protecting Location Privacy

• 
  5 principles of institutional constraints (right to know, right to choose, right to participate, collectors, mandatory)
• Privacy policy
  Customized targeted privacy protection
• Identity anonymity
  Hide "identity" in location information
• Data Obfuscation
  Preserve identity, obfuscate other parts of location information, so that attackers cannot know the user's exact location