2023 1 embedded systems chapter 5

Wireless communication▪ First Wireless Communication SystemMarconi’s Radio Transmitter Systemhttp://iwcmediaecology.pbworks.com/w/page/8480806/Guglielmo%20Marconi... Wireless communicati

HỆ THỐNG NHÚNG

Dr Thanh Nguyen

Email: thanh.nguyenngoc@phenikaa-uni.edu.vn Office: Room 606 - Building A4

Chương 5: HỆ THỐNG NHÚNG VÀ IOT

➢ 1895, Marconi first heard of wireless and He was fascinated

➢ 1897, He formed the Wireless Telegraph and Signal Co Ltd ,

the first commercial development in the world

Wireless communication

▪ First Wireless Communication System

Marconi’s Radio Transmitter System

http://iwcmediaecology.pbworks.com/w/page/8480806/Gugliel

mo%20Marconi

Wireless communication

▪ RF – Radio Frequency (few kHz to 300GHz)

Wireless communication

▪ Half-Duplex RF System

▪ Operation mode of a radio

communication system in which each end can transmit and

receive, but not simultaneously.

▪ The communication is

bi-directional over the same frequency, but uni-directional for the duration of a message The devices need to be transceivers

Wireless communication

▪ Full-Duplex RF System

▪ Radio system which each end can transmit and receive simultaneously.

▪ Typically use two frequencies as channel Each channel is used solely for

transmitting (or receiving)

▪ Example: Cell phone, satellite communication,…

▪ Frequency Shift Keying (FSK)

▪ Less susceptible to noise

▪ Require larger bandwidth

▪ Phase Shift Keying (PSK)

▪ Less susceptible to noise,

bandwidth efficient

▪ Require synchronization in phase

and frequency

Wireless communication

Basis Elements of Wireless Communication System

Wireless communication

Avoiding Interference in ISM Band

▪ Spread Spectrum Technique: intentionally spread over a wide frequency

range

▪ Resistant to noise and interference thus increasing the probability that

the signal will be received correctly

▪ Unlikely to interfere with other signals even if they are transmitted on

the same frequency

▪ Types of Spread Spectrum common in ISM bands :

▪ Direct Sequence Spread Spectrum ( DSSS )

▪ Frequency Hopping Spread Spectrum ( FHSS )

▪ Orthogonal Frequency Division Multiplexing ( OFDM )

Wireless communication

Direct Sequence Spread Spectrum

Wireless communication

Direct Sequence Spread Spectrum

▪ Advantage of DSSS:

▪ More bandwidth

▪ Data are encoded

▪ Low power density, noise-like signal

Wireless communication

Frequency Hopping Spread Spectrum

▪

Wireless communication

Orthogonal Frequency Division Multiplexing

▪

Wireless communication

Orthogonal Frequency Division Multiplexing

▪

Wireless communication

ISM band – 2.4 GHz

▪ ISM: Industrial, scientific and Medical

▪ ISM band: 2.4GHz-2.483GHz

▪ Getting more crowed day by day

▪ Why use this band?

BLUETOOTH

▪ Initiated by Ericsson Mobile in 1989

▪ Named as a king of Denmark in 900s, Harald Bluetooth

▪ Frequency band 2.402 GHz - 2.480 GHz

▪ Connection between devices, point to point/ multipoint

BLUETOOTH Addresses and Name

▪ Every Bluetooth device has a unique 48-bit address – MAC

address (Medium Access Control)

▪ Bluetooth devices can also have user-friendly names (presented

to user to identify devices)

BLUETOOTH

▪ Version

BLUETOOTH

▪ Version

BLUETOOTH Low Energy (BLE)

▪ BLE aims to operate at very low power

▪ BLE compromises in data rate

▪ 1Mbps (theory) – 0.27Mbps (practical)

▪ BLE devices switch between sleeping and

working state to save energy

▪ BLE requires rapid connection, small package

BLE Direction Finding

▪ Direction Finding is feature of BLE 5.1

▪ Enable positioning solution

▪ Old BLE rely on RSSI (Receive Signal Strength Indicator)

▪ New BLE knows the actual direction of signal

BLE MCU

▪ “Wireless Fidelity”

▪ Exchange data wirelessly in Wireless

▪ IEEE 802.11

▪ links two or more devices using some wireless distribution method, and

provides a connection through an access point to the wider internet

▪ High Speed , wide range ( 50m indoor , 100m out door )

▪ Power consumption : chipsets 0.5-1w; wifi device 1-2w , router 4-5w ,

WIFI star network

• Same role devices

• All connect to Hub

• Security

• Limited access

• Access IP (192.168.xxx)

▪ Consume very low power: 2.5-3 times more efficient than Bluetooth

▪ "optimized for the unique needs of remote monitoring and control

Zigbee Mesh Network

▪ Message can be transferred from any

source to any destination

▪ Every FDD (full function device) or

Router can connect to its neighbors

▪ High reliability achieved through

multiple paths

Zigbee Mesh Network

Zigbee Architecture

Comparison

WEB SERVER

System Diagram

Advantage

• Directly control system

• Make use of the hardware capability

Disadvantage

• Limited by hardware and OS

• Can’t remote control

• Difficult to access online database

WEB SERVER

System Diagram

Advantage

• Not depend on OS

• Control/monitor system from anywhere

• Use resource available on the internet

Disadvantage

• Depend on wifi/internet

• Can’t be very complex

• Show data, plot graph

• Simple algorithms/calculation

WEB SERVER

Problem

• What is the web server and its functions?

• How to create a web server?

• How to communicate/transfer data between web server and devices

• Why do we need an embedded system?

WEB SERVER

• Web server hosts a web site and provides reliable services for any

requesting client

• Web server communicate

with clients via different

protocols: TCP, UDP,…

WEB SERVER

• Web server

Server apache

Database MySQL

WEB SERVER

https://ruslanspivak.com/lsbaws-part1/

HyperText Transfer Protocol (HTTP)

• HTTP is an asymmetric request-response client-server

protocol

• HTTP is a stateless protocol

HyperText Transfer Protocol (HTTP)

• HTTP client and server communicate by sending text messages

• An HTTP message consist of a message header and an optional

message body, separated by a blank line

HTTP request message

• The request message syntax:

• Request-method-name: GET, POST, HEAD, OPTIONS

• Request-Url: specify the resource requested

• HTTP version: HTTP/1.0 &HTTP/1.1

HTTP request message

• The request header syntax:

• request-header-name: request-header-value1, request-header-value2

• The request header syntax:

• name1=value1& name2=value2&…

HTTP response message

• Status line: HTTP ver status-code reason-phrase