CS计算机代考程序代写 compiler c++ 1

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Protocol Stack

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Target of this class

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twisted pair
1 Mm 300 Hz
VLF
coax cable
optical transmission
1 μm 300 THz
visible light UV
Radio spectrum for communication
10 km 30 kHz
100 m 3 MHz
MF HF
1 m
300 MHz
VHF UHF
10 mm 30 GHz
SHF EHF
100 μm 3 THz
infrared
LF
© Jochen Schiller, FU Berlin

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ISM bands


Frequency
13,553-13,567 MHz 26,957 – 27,283 MHz 40,66 – 40,70 MHz 433 – 464 MHz
900 – 928 MHz
2,4 – 2,5 GHz
5,725 – 5,875 GHz 24 – 24,25 GHz
Europe Americas
802.11b/g, Bluetooth
802.11a
Frequency Allocation

US Frequency Allocation
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Modulation: Transmitting Data With Radio Waves
➢ ➢
–φ ➢

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Modulation Examples



© Tanenbaum, Computer Networks
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Modulation and Keying – IQ Data
Source: TI.com

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Receiver: Demodulation

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Attenuation and Distortion

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– –
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Attenuation: Path Loss

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Distortion Effects: Non-line-of-sight Paths

– –
signal at receiver
© Jochen Schiller, FU Berlin
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Non-line-of-sight path Line-of-
multipath pulses
sight path
LOS pulses

Wireless signal strength in a multi-path environment
➢ Brighter color = stronger signal
➢ Obviously, simple (quadratic) free space attenuation formula is not sufficient to capture these effects
© Jochen Schiller, FU Berlin
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γ –γ
Attenuation
–σ –

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Noise and Interference

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➢ ➢


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Symbols and Bit Errors

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Channel Models – Analog

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WSN-specific channel models
–γ –σ

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Wireless channel quality – summary

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Some transceiver design considerations

➢ ➢
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– –


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Choice of modulation

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Automatic Modulation Recognition

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Summary

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IEEE 802.15.4 Application Space
● ● ● ● ●

Differences between IEEE 802.15.4 & ZigBee
➢ IEEE 802.15.4
– PHYsical Layer (PHY)
• Radio portion, transmitter and receiver
– Media Access Control (MAC) Layer • Radio controller, data to next device
➢ ZigBee
– Network Layer
– Application Support Layer
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IEEE 802.15.4 Architecture
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IEEE 802.2 LLC
868/915 MHz
2400 MHz
Upper Layers
Other LLC
IEEE 802.15.4 MAC
IEEE 802.15.4
PHY
IEEE 802.15.4
PHY

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802.15.4 General Characteristics
➢ ➢ ➢ ➢ ➢ ➢ ➢ ➢
✓ ✓
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IEEE 802.15.4 PHY Overview
Operating Frequency Bands
868MHz / 915MHz PHY
Channel 0
868.3 MHz
Channels 1-10
902 MHz
2 MHz
928 MHz
2.4 GHz PHY
2.4 GHz
Channels 11-26
5 MHz
2.4835 GHz
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● ● ● ●
Preamble
Start of Packet Delimiter
6 Octets
PHY Header
PHY Service Data Unit (PSDU)
0-127 Octets
IEEE 802.15.4 PHY Overview
Packet Structure

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IEEE 802.15.4 PHY Overview
Modulation/Spreading

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● ●
● ● ●
IEEE 802.15.4 PHY Overview
Common Parameters


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IEEE 802.15.4 PHY Overview
PHY Primitives

Principles of Object-Oriented Programming using C++
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➢ ➢ ➢
What is OOP?

Basic Concepts of OOP
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Classes in C++
Can you see the problem in this piece of code?
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Abstraction / Information Hiding

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Abstraction / Information Hiding (2)

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Encapsulation

➢ ➢ ➢
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Inheritance

Inheritance (2)
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Inheritance (3)
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Static vs Dynamic Binding

Let’s Fix the Problem…
➢ Defining in a base class a virtual function, with another version in a derived class, signals to the compiler that we don’t want static binding for this function
➢ What we do want is the selection of the function to be called at any given point in the program to be based on the kind of object for which it is called
➢ This is called dynamic linkage, or late binding
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Pure Virtual Functions
➢ ➢ ➢

Virtual Functions
+
Inheritance
=
Polymorphism! (can somebody define it now?)
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Polymorphism:
Ability of a reference variable to change behavior according to what instance variable it is holding
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Examples of Design Patterns that use Polymorphism
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Factory Design Pattern
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Observer Design Pattern (Code Example)
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State Design Pattern (Code Example)
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