The physical layer overview document discusses:
1. The physical layer architecture and clear channel assessment function.
2. The standardized physical layers for 802.11 including frequency hopping, direct sequence, and infrared.
3. Licensed and unlicensed frequency bands where 802.11 operates, requiring spread spectrum technology in unlicensed bands.
Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use radio
Fundamental of Radio Frequency communications.pptginanjaradi2
Fundamentals of Radio Frequency (RF) communications encompass the principles and techniques used to transmit and receive information wirelessly using electromagnetic waves within the radio frequency spectrum. Here's a breakdown of the key components:
1. **Electromagnetic Spectrum**: RF communications utilize a portion of the electromagnetic spectrum. This spectrum ranges from low frequencies used for power transmission to high frequencies used in technologies like microwaves and beyond. RF typically occupies the frequency range from about 3 kHz to 300 GHz.
2. **Modulation**: Modulation is the process of impressing information onto a radio wave by varying one or more of its properties such as amplitude, frequency, or phase. Common modulation techniques include Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
3. **Transmitters**: Transmitters generate radio frequency signals carrying the information to be transmitted. They typically consist of an oscillator to produce the carrier frequency, modulation circuitry to impress the information onto the carrier, and amplifiers to boost the signal for transmission.
4. **Receivers**: Receivers capture radio frequency signals, extract the desired information, and convert it into a usable form. Receivers include components such as antennas to capture the incoming signal, amplifiers to boost weak signals, demodulators to extract the information from the carrier, and filters to remove unwanted noise and interference.
5. **Antennas**: Antennas are crucial components for both transmitting and receiving RF signals. They convert electrical signals into electromagnetic waves for transmission and vice versa for reception. Antennas come in various designs optimized for different applications, such as dipole antennas, patch antennas, and parabolic antennas.
6. **Propagation**: RF signals propagate through the atmosphere, and their behavior is influenced by factors such as frequency, distance, terrain, and environmental conditions. Understanding propagation characteristics is essential for designing efficient communication systems.
7. **Propagation Models**: Propagation models describe how RF signals propagate in different environments. These models help engineers predict signal strength, coverage areas, and potential sources of interference. Common models include free-space path loss, multipath fading, and terrain-based models.
8. **Spectrum Management**: Since the radio frequency spectrum is a finite and shared resource, its allocation and usage are regulated by government agencies such as the Federal Communications Commission (FCC) in the United States. Spectrum management involves allocating frequency bands to different users, enforcing regulations to prevent interference, and promoting efficient spectrum utilization.
9. **Applications**: RF communications find applications in various fields, including broadcasting, telecommunications, wireless networking.
Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use radio
Fundamental of Radio Frequency communications.pptginanjaradi2
Fundamentals of Radio Frequency (RF) communications encompass the principles and techniques used to transmit and receive information wirelessly using electromagnetic waves within the radio frequency spectrum. Here's a breakdown of the key components:
1. **Electromagnetic Spectrum**: RF communications utilize a portion of the electromagnetic spectrum. This spectrum ranges from low frequencies used for power transmission to high frequencies used in technologies like microwaves and beyond. RF typically occupies the frequency range from about 3 kHz to 300 GHz.
2. **Modulation**: Modulation is the process of impressing information onto a radio wave by varying one or more of its properties such as amplitude, frequency, or phase. Common modulation techniques include Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
3. **Transmitters**: Transmitters generate radio frequency signals carrying the information to be transmitted. They typically consist of an oscillator to produce the carrier frequency, modulation circuitry to impress the information onto the carrier, and amplifiers to boost the signal for transmission.
4. **Receivers**: Receivers capture radio frequency signals, extract the desired information, and convert it into a usable form. Receivers include components such as antennas to capture the incoming signal, amplifiers to boost weak signals, demodulators to extract the information from the carrier, and filters to remove unwanted noise and interference.
5. **Antennas**: Antennas are crucial components for both transmitting and receiving RF signals. They convert electrical signals into electromagnetic waves for transmission and vice versa for reception. Antennas come in various designs optimized for different applications, such as dipole antennas, patch antennas, and parabolic antennas.
6. **Propagation**: RF signals propagate through the atmosphere, and their behavior is influenced by factors such as frequency, distance, terrain, and environmental conditions. Understanding propagation characteristics is essential for designing efficient communication systems.
7. **Propagation Models**: Propagation models describe how RF signals propagate in different environments. These models help engineers predict signal strength, coverage areas, and potential sources of interference. Common models include free-space path loss, multipath fading, and terrain-based models.
8. **Spectrum Management**: Since the radio frequency spectrum is a finite and shared resource, its allocation and usage are regulated by government agencies such as the Federal Communications Commission (FCC) in the United States. Spectrum management involves allocating frequency bands to different users, enforcing regulations to prevent interference, and promoting efficient spectrum utilization.
9. **Applications**: RF communications find applications in various fields, including broadcasting, telecommunications, wireless networking.
Access the video from this presentation for free from
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Overview:
Electromagnetic interference is increasingly becoming a problem in complex systems that must interoperate in both digital and RF domains. When failures due to EMI occur it is often difficult to track down the sources of such failures using standard test receivers and spectrum analyzers. The unique ability of real-time spectrum analysis and synchronous time domain signal acquisition to capture transient events can quickly reveals details about the sources of EMI.
What You Will Learn:
How to isolate and analyze sources of EMI using an oscilloscope
Measurement considerations for correlating time and frequency domains
Near field probing basics
Presented By:
Dave Rishavy, Product Manager Oscilloscopes, Rohde & Schwarz
Dave Rishavy has a BS in Electrical Engineering from Florida State University and an MBA from the University of Colorado. Prior to joining Rohde and Schwarz, Mr. Rishavy gained over 15 years of experience in the test and measurement field at Agilent Technologies. This included positions in a wide range of technical marketing areas such as application engineering, product marketing, marketing management and strategic product planning. While at Agilent, Dave led the marketing and industry segment teams for the Infiniium line of oscilloscopes as well as high end logic analysis.
Topics covered in this presentation:
Radio & Microwave Communication.
2. Spectrum Management.
3. Digital Microwave Systems.
4. Fading and measures to counter Fading effect.
5. Digital Microwave link – Performance Objectives.
6. Modulation Methods.
7. A word about BWA
8. Other wireless communication Applications
High performance browser networking ch5,6Seung-Bum Lee
Presentation material including summary of "High Performance Browser Networking" by Ilya Grigorik. This book includes very good summary of computer network not only for internet browsing but also multimedia streaming.
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.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
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
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and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
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adversary training.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
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!
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2. Physical-Layer Architecture
• The physical layer also incorporates a clear channel assessment (CCA) function
to indicate to the MAC when a signal is detected
3. The Radio Link
• Based on physical medium, three physical layers were
standardized in 802.11 :
1. Frequency-hopping (FH) spread-spectrum radio PHY
2. Direct-sequence (DS) spread-spectrum radio PHY
3. Infrared light (IR) PHY
• 3 further physical layers based on radio technology
1. 802.11a: Orthogonal Frequency Division Multiplexing (OFDM) PHY
2. 802.11b: High-Rate Direct Sequence (HR/DS or HR/DSSS) PHY
3. 802.11g: Extended Rate PHY (ERP)
4. The future 802.11n, which is colloquially called the MIMO PHY or
the High-Throughput PHY
4. The Radio Link - Two frequency bands:
• What is a frequency band?
• Two categories of wireless frequency bands:
1. Licensed frequency bands
2. Unlicensed frequency bands
5. The Radio Link – Licensed frequency bands:
What are licensed frequency bands ?
• licensed frequency bands:
• Users are primary users or narrowband receivers
• Licenses can restrict
i. frequencies
ii. transmission power used ,
iii. area over which radio signals can be transmitted
• E.g. radio broadcast stations must have a license
• Intentional interference may be subject to criminal or civil
penalties
6. The Radio Link - unlicensed frequency bands:
• What are unlicensed frequency bands ?
• No license , users are secondary users
• These bands are commonly referred to as the ISM bands -
industrial, scientific, and medical equipment
• The 2.4-GHz band is available worldwide for use
• E.g. microwave ovens operate at 2.45 GHz
• Building, manufacturing, and designing 802.11 equipment
does require a license
7. The Radio Link - unlicensed frequency bands:
Unlicensed does not mean it doesn’t have any rules and
regulations to be followed.
• unlicensed devices must do is obey limitations on
transmitted power.
• Interference with any device (licensed or Unlicensed) must
be avoided by using spread-spectrum technologies
8. Spread Spectrum
• This technology is a requirement for unlicensed devices.
• Spreading the transmission over a wide band which tries to
eliminate the interference problems with other devices
• But doesn't make the problem go away : As more RF devices
occupy the area that your wireless network covers, you'll see
the noise level go up.
9. Types of spread spectrum
1. Frequency hopping (FH or FHSS)
• FH systems jump from one frequency to another in a
random pattern, transmitting a short burst at each
subchannel
2. Direct sequence (DS or DSSS)
• spread the power out over a wider frequency band using
mathematical coding functions.
• Two direct-sequence layers were specified.
• a 2-Mbps PHY, and
• HR/DSSS PHY.
10. Types of spread spectrum
3. Orthogonal Frequency Division Multiplexing (OFDM)
• OFDM divides an available channel into several sub
channels and encodes a portion of the signal across each
sub channel in parallel.
• Frequency-hopping systems
• are the cheapest to make.
• Precise timing is needed to control the frequency hops,
• But sophisticated signal processing is not required
11. Types of spread spectrum
• Direct-sequence systems
• require more sophisticated signal processing,
• require more specialized hardware
• and higher electrical power consumption.
• But allows a higher data rate than frequency-hopping
systems.
12. RF Propagation with 802.11
• Radio signal on space is mixture of signal and noise.
• Main functionality of radio signal communication is making signal
intelligible over noise.
• Performance of the signal is measured in terms of signal-to-noise ratio
(SNR).
Signal Reception and Performance
14. RF Propagation with 802.11
• Theoretically there is no limit for the amount of data carried by a radio
channel. But practically there is a limit for radio channel.
• The theorem expresses the mathematical limit of the capacity of a
communications channel. Also called as shannon capacity.
The Shannon limit
S/N = 2 ^ (C/W) - 1 (S/N as power ratio)
SNR = 10 * log10 (2 ^ (C/W) - 1) (SNR as dB)
15. RF Propagation with 802.11
• The theorem expresses the mathematical limit of the capacity of a
communications channel
The Shannon limit
Shannon limit as a function of SNR
16. RF Propagation with 802.11
• Range is the distance of MS from AP
• As range increases, the signal level drops, hence the throughput drops;
• with a constant noise floor, the degraded signal will result in a degraded
signal to noise ratio.
Path Loss, Range, and Throughput
Throughput versus distance
when the signal-to-noise ratio
gets too small to support a high
data rate, the station will fall
back to a lower data rate with
less demanding signal-to-noise
ratio requirements
17. RF Propagation with 802.11
• What is path loss ?
• The loss in free-space is sometimes called the path loss. It is
the minimum loss occurring when signal travels in a path.
Path loss (dB) = 32.5 + 20 log F + log d
• where the frequency F is expressed in GHz,
• and the distance d is expressed in meters
• . Obstacles such as walls and windows will reduce the signal, and
antennas and amplifiers may be used to boost the signal, which
compensates for transmission losses.
Total loss = TX power + TX antenna gain - path loss - obstacle loss - link
margin + RX antenna gain
18. RF Propagation with 802.11
Multiple paths
Multipath Interference
• Waves spread outward from the transmitting antenna in all directions and are
reflected by surfaces in the area
• The wave at the receiver is the sum of all the different components
• multipath interference can be resolved by changing the orientation or position
of the receiver.
19. RF Propagation with 802.11
Multipath Interference
Wave combination by superposition
In (c) ,the two waves are almost exactly the
opposite of each other, so the net result is
almost nothing
20. RF Propagation with 802.11
Inter-Symbol Interference (ISI)
• Waves that take different paths from the transmitter to the receiver will travel
different distances and be delayed with respect to each other
• Once again, the two waves combine by superposition, but the effect is that the
total waveform is garbled.