This document discusses spread spectrum modulation techniques. It begins with an introduction and explains that spread spectrum is a technique where a signal is transmitted over a wider bandwidth than the original signal. It then describes two major spread spectrum techniques: frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). The document outlines the advantages of spread spectrum including resistance to jamming, reduced interference, and security. It also discusses applications of spread spectrum such as wireless communications and Bluetooth.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media
These slides cover a topic on Spread spectrum in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Spread spectrum system promises several benefits, such as higher capacity, anti-jamming and the ability to resist multipath propagation in wireless communication. I hope this content will provide useful informations about this system.
Spread spectrum is a communication technique that spreads a narrowband communication signal over a wide range of frequencies for transmission then de-spreads it into the original data bandwidth at the receive.
These slides cover a topic on Spread spectrum in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Spread spectrum system promises several benefits, such as higher capacity, anti-jamming and the ability to resist multipath propagation in wireless communication. I hope this content will provide useful informations about this system.
Spread spectrum is a communication technique that spreads a narrowband communication signal over a wide range of frequencies for transmission then de-spreads it into the original data bandwidth at the receive.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Wireless# Guide to Wireless CommunicationsChapter 3Und.docxambersalomon88660
Wireless# Guide to Wireless Communications
Chapter 3
Understanding Radio Frequency Communications
Wireless# Guide to Wireless Communications
ObjectivesList the components of a radio systemDescribe how different factors affect the design of a radio systemDiscuss why standards are beneficial and list the major telecommunications standards organizationsExplain the radio frequency spectrum
Wireless# Guide to Wireless Communications
Components of a Radio SystemComponents include:FiltersMixersAmplifiersAntennas
Wireless# Guide to Wireless Communications
FiltersFilterRemoves unwanted RF signalsRF filterEither passes or rejects a signal based on frequencyTypes of filtersLow-pass filterHigh-pass filterBandpass filter
Wireless# Guide to Wireless Communications
Filters (continued)
Wireless# Guide to Wireless Communications
Filters (continued)Filters are also found in transmittersUsed to eliminate some unwanted frequenciesThat result from the process of modulating the signal before transmissionIntermediate frequency (IF) signalResulting output from the modulation processIF signal is filtered through a bandpass filterTo remove any undesired high- or low-frequency signals
Wireless# Guide to Wireless Communications
Filters (continued)
Wireless# Guide to Wireless Communications
MixersCombine two radio frequency inputs to create a single outputOutput is in the range of the highest sum and the lowest difference of the two frequenciesSum and differences are known as the sidebands of the frequency carrierShield transmitted signal from “stray” signalsUsed to convert an input frequency to a specific desired output frequency
Wireless# Guide to Wireless Communications
Mixers (continued)
Wireless# Guide to Wireless Communications
Mixers (continued)
Wireless# Guide to Wireless Communications
AmplifiersIncrease the amplitude of an RF signalRF signals tend to lose intensity (amplitude)When they move through circuits, air, or spaceAmplifier is an active deviceMust be supplied with electricityIncreases a signal’s intensity or strengthBy using the input signal to control a circuit that “shapes” the outputTo reflect the shape of the input signal exactly
Wireless# Guide to Wireless Communications
Amplifiers (continued)
Wireless# Guide to Wireless Communications
AntennasTransmit or receive an RF signal
Wireless# Guide to Wireless Communications
Antennas (continued)
Wireless# Guide to Wireless Communications
Design of a Radio SystemDesigners of radio communications systems Need to consider how the systems will be used
Wireless# Guide to Wireless Communications
Multiple AccessOnly a limited number of frequencies are available for radio transmissionConserving the use of frequencies is importantConserving a frequencyShare a frequency among several individual usersMethods that allow multiple accessFrequency Division Multiple Access (FDMA)Time Division Multiple Access (TDMA)Code Division Mult.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
2. INTRODUCTION
WHY SPREAD SPECTRUM MODULATION?
HOW IT WORKS
SPREAD SPECTRUM TECHNIQUES
APPLICATIONS
CONCLUSION
3. Wireless Networks Spring 2005
Spread-spectrum radio communications is a favorite technology of the military
because it resists jamming and is hard for an enemy to intercept, Just as they
are unlikely to be intercepted by a military opponent
4. Spread Spectrum : This is a technique in which
a telecommunication signal is transmitted on a bandwidth considerably
larger than the frequency content of the original information.
Frequency hopping is a basic modulation technique used in spread
spectrum signal transmission.
A communication system is considered a spread spectrum system if it
satisfies the following two criteria:
Bandwidth of the spread spectrum signal has to be greater than the
information bandwidth. (This is also true for frequency and pulse code
modulation!)
The spreading sequence has to be independent from the information.
Thus, no possibility to calculate the information if the sequence is known
and vice versa.
5. Problem of radio transmission: frequency dependent fading can wipe
out narrow band signals for duration of the interference
Solution: spread the narrow band signal into a broad band signal
using a special code
detection
at
receiver
interference
spread
signal
signal
spread
interference
f f
power
power
7. Spread spectrum signals are distributed over a wide range
of frequencies and then collected back at the receiver
These wideband signals are noise-like and hence difficult to
detect or interfere with
Initially adopted in military applications, for its resistance
to jamming and difficulty of interception
More recently, adopted in commercial wireless
communications
Wireless Environment and Wireless LANs
7
8. Safeguards for physical
security must be even greater
in wireless communications
Encryption: intercepted
communications must not be
easily interpreted
Authentication: is the node
who it claims to be?
Wireless Environment and Wireless LANs
8
9. A noise-like and random signal has to be generated at the
transmitter.
The same signal must be generated at the receiver in
synchronization.
We limit the complexity by specifying only one bit per
sample, i.e., a binary sequence.
These special "Spreading" codes are called "Pseudo
Random" or "Pseudo Noise" codes. They are called
"Pseudo" because they are not real Gaussian noise
9
10. PN generator produces periodic sequence that appears
to be random
PN Sequences
Generated by an algorithm using initial seed
Sequence isn’t statistically random but will pass many test of
randomness
Sequences referred to as pseudorandom numbers or
pseudonoise sequences
Unless algorithm and seed are known, the sequence is
impractical to predict
Wireless Networks Spring 2005
11. THE MAJOR SPREAD SPECTRUM TECHNIQUES
ARE
DSSS
FHSS
12. Wireless Environment and Wireless LANs
12
1101010010011
11010111010100100001101010010011111010100100111
17. SS Technique advantage disadvantage
Direct Sequence best behavior in multi
path rejection
no synchronization
simple implementation
difficult to detect
near far effect
coherent bandwidth
Frequency
Hopper
complex hardware
error correction
needed
no need for coherent
bandwidth
less affected by the near far
effect
18. 1. Reduced crosstalk interference:
2. Better voice quality/data integrity and less static
noise
3. Lowered susceptibility to multipath fading
4. Inherent security:
5. Co-existence:
6. Longer operating distances
7. Hard to detect:
8. Hard to intercept or demodulate:
9. Harder to jam
19. • Radio-jamming is ever-present threat to radio channels
• This is an attack on the availability of signals
– Denial-of-Service (DoS) attack
• Traditional anti-jamming techniques rely on pre-shared
secret codes (keys) to increase channel availability
19
RCVR
XMTR JMR
20. • Spread-Spectrum Techniques
– FHSS (Frequency Hopping
Spread Spectrum)
– DSSS (Direct-Sequence
Spread Spectrum)
20
frequency
Hopping sequence (PRNG seed) must be known
to the sender and receiver but not the jammer.
Spreading code (PRNG seed) must be known
to the sender and receiver but not the jammer.
frequency
energyenergy
PRNGPRNG
PRNGPRNG
21. Universal framework to
integrate a diverse set of
devices in a seamless, user-
friendly, efficient manner
Devices must be able to
establish ad hoc
connections
Support for data and voice
Similar security as cables
Simple, small, power-
efficient implementation
Inexpensive!
Wireless Environment and Wireless LANs
21
Bluetooth
printer
module
Bluetooth
phone and
headset
22. Multiple Transmitters 1 Receiver
Choice of unique sequences to spread the
data bits
Ability of receiver to distinguish between
data streams
23. This method of communication
i.e in CDMA cannot offer much of the international
roaming and many other advanced user services
Increased complexity
Large Bandwidth