Some of the difficulties in the study of new generation wireless mobile systems are lack of practical
implementation for various strategies like, multiuser code division multiple accesses, assigning radio resources using DSSS,
use of orthogonal codes etc. In this paper we are going to discuss some of the above stated problems with their
implementation issues. CDMA is a scheme by which multiple users are assigned radio resources using DS-SS
techniques. Although all users are transmitting in the same RF band, individual users are separated from each other via
the use of orthogonal codes. Capacity is defined as the total number of simultaneous users the system can support, and
quality is defined as the perceived condition of a radio link assigned to a particular user. We have use MATLAB as a
simulation tool and result shows how multi-user CDMA performs under certain circumstances.
1. The document provides definitions and explanations of key concepts in digital communication systems and coding techniques. It contains questions and answers on topics like modulation, sampling theorem, equalization, coding, and error correction.
2. Key concepts defined include modulation, inter-symbol interference, matched filters, maximum likelihood detection, orthogonal signals, coding gain, and convolutional codes.
3. Error correction techniques like Hamming codes, BCH codes, and RS codes are described in terms of their parameters, capabilities, and decoding methods. The differences between block codes and convolutional codes are also summarized.
A complete power point presentation to know how Public Switching Telephone Network works. Useful for those in the working field or for the ones who want to know more or submitting any project report..
The document describes MATLAB software and its uses for signal processing. MATLAB is a matrix-based program for scientific and engineering computation. It provides built-in functions for technical computation, graphics, and animation. The Signal Processing Toolbox contains functions for filtering, Fourier transforms, convolution, and filter design. The document lists some important MATLAB commands and frequently used signal processing functions, along with their syntax and purpose. It also describes the basic windows of the MATLAB interface and provides examples of generating common continuous and discrete time signals using MATLAB code.
The document discusses cellular system capacity and the Erlang B formula. It provides examples of calculating the number of supported users for different channel configurations using the formula. Key points:
- The Erlang B formula calculates the blocking probability given traffic intensity and number of channels
- Sectoring increases SIR but reduces trunking efficiency by sharing channels among more sectors
- For a 400 channel, 20MHz system with SIR>15dB and blocking <5%, 120 degree sectoring with a cluster size of 3 supports the most users at around 38,000. Smaller cluster sizes increase channels per sector and supported users.
The document discusses calculating the discrete Fourier transform (DFT) using a matrix method. It involves representing the DFT as a matrix multiplication of an N×N twiddle factor matrix and an N×1 input vector. The twiddle factor matrix contains elements that are powers of the Nth root of unity. An example calculates the 4-point DFT of the vector [1, 2, 0, 1] by multiplying it by the twiddle factor matrix.
Code-Division Multiple Access (CDMA)
Definition
Features
Example
Example Diagram
Mechanisms
Chip Sequences Code
Walsh Tables: Chip Sequence Code Generation
CDMA: Representation of Data
CDMA : An Real Example
CDMA : Digital Signal Created
CDMA : Data on the Channel
CDMA: Decoding of composite signals in one station
CDMA : Advantages of Synchronous & Asynchronous
CDMA : Uses
This document presents a seminar on symbol timing estimation. It discusses various techniques for symbol synchronization at the receiver, including transmitting a clock signal along with data, self-synchronization using a decision directed maximum likelihood approach, and extracting the clock signal from the received data. It describes how maximum likelihood timing estimation works by taking the derivative of the log-likelihood function with respect to time delay and setting it equal to zero to find the optimal estimate. Diagrams are provided to illustrate maximum likelihood timing estimation implementation using a decision directed loop with a matched filter, sampler, and voltage controlled clock/oscillator.
X.25 is an ITU-T standard protocol that defines how connections between user devices and network devices are established and maintained over packet-switched networks. It uses the Packet Layer Protocol (PLP) for network layer functions, Link Access Procedure, Balanced (LAPB) for data link layer functions, and various physical layer standards. X.25 supports both switched and permanent virtual circuits for data transfer.
1. The document provides definitions and explanations of key concepts in digital communication systems and coding techniques. It contains questions and answers on topics like modulation, sampling theorem, equalization, coding, and error correction.
2. Key concepts defined include modulation, inter-symbol interference, matched filters, maximum likelihood detection, orthogonal signals, coding gain, and convolutional codes.
3. Error correction techniques like Hamming codes, BCH codes, and RS codes are described in terms of their parameters, capabilities, and decoding methods. The differences between block codes and convolutional codes are also summarized.
A complete power point presentation to know how Public Switching Telephone Network works. Useful for those in the working field or for the ones who want to know more or submitting any project report..
The document describes MATLAB software and its uses for signal processing. MATLAB is a matrix-based program for scientific and engineering computation. It provides built-in functions for technical computation, graphics, and animation. The Signal Processing Toolbox contains functions for filtering, Fourier transforms, convolution, and filter design. The document lists some important MATLAB commands and frequently used signal processing functions, along with their syntax and purpose. It also describes the basic windows of the MATLAB interface and provides examples of generating common continuous and discrete time signals using MATLAB code.
The document discusses cellular system capacity and the Erlang B formula. It provides examples of calculating the number of supported users for different channel configurations using the formula. Key points:
- The Erlang B formula calculates the blocking probability given traffic intensity and number of channels
- Sectoring increases SIR but reduces trunking efficiency by sharing channels among more sectors
- For a 400 channel, 20MHz system with SIR>15dB and blocking <5%, 120 degree sectoring with a cluster size of 3 supports the most users at around 38,000. Smaller cluster sizes increase channels per sector and supported users.
The document discusses calculating the discrete Fourier transform (DFT) using a matrix method. It involves representing the DFT as a matrix multiplication of an N×N twiddle factor matrix and an N×1 input vector. The twiddle factor matrix contains elements that are powers of the Nth root of unity. An example calculates the 4-point DFT of the vector [1, 2, 0, 1] by multiplying it by the twiddle factor matrix.
Code-Division Multiple Access (CDMA)
Definition
Features
Example
Example Diagram
Mechanisms
Chip Sequences Code
Walsh Tables: Chip Sequence Code Generation
CDMA: Representation of Data
CDMA : An Real Example
CDMA : Digital Signal Created
CDMA : Data on the Channel
CDMA: Decoding of composite signals in one station
CDMA : Advantages of Synchronous & Asynchronous
CDMA : Uses
This document presents a seminar on symbol timing estimation. It discusses various techniques for symbol synchronization at the receiver, including transmitting a clock signal along with data, self-synchronization using a decision directed maximum likelihood approach, and extracting the clock signal from the received data. It describes how maximum likelihood timing estimation works by taking the derivative of the log-likelihood function with respect to time delay and setting it equal to zero to find the optimal estimate. Diagrams are provided to illustrate maximum likelihood timing estimation implementation using a decision directed loop with a matched filter, sampler, and voltage controlled clock/oscillator.
X.25 is an ITU-T standard protocol that defines how connections between user devices and network devices are established and maintained over packet-switched networks. It uses the Packet Layer Protocol (PLP) for network layer functions, Link Access Procedure, Balanced (LAPB) for data link layer functions, and various physical layer standards. X.25 supports both switched and permanent virtual circuits for data transfer.
Spread spectrum techniques spread data signals over a wide bandwidth to make them resistant to jamming and interception. There are two main approaches: frequency hopping spread spectrum (FHSS) rapidly switches a narrowband signal across a wide band of frequencies in a pattern known only to the transmitter and receiver, while direct sequence spread spectrum (DSSS) encodes data bits by adding extra bits using a spreading code before transmission. Code division multiple access (CDMA) allows multiple users to share the same frequency band by using user-specific spreading codes, with the signals combined at the receiver.
This document discusses modeling wireless communication systems using MATLAB. It covers:
- Characterizing the wireless channel from physics of propagation to multi-path fading channels.
- Statistical characterization of channels including Doppler spectrum, delay spread, coherence time and bandwidth.
- Simulating multi-path fading channels in MATLAB and modeling path loss.
- Explaining how multi-path propagation leads to signal distortion and is equivalent to undesired filtering.
Wireless ATM (WATM) combines ATM technology with wireless networks to provide multimedia services over mobile networks. It enables services like video conferencing and distance learning across offices, schools, hospitals and other environments. Key challenges include maintaining quality of service during handovers between wireless cells and efficiently managing the location of mobile users. The Wireless ATM Working Group was formed to develop specifications allowing ATM networks to support mobility through functions like handover signaling, location management and mobile routing.
Small scale fading and multipath measurementsVrince Vimal
1. The document discusses small-scale fading and multipath measurements in wireless channels. It describes how fading occurs due to interference from multiple copies of transmitted signals arriving at the receiver at different times.
2. Key channel parameters that influence fading are discussed, including multipath propagation, Doppler shift caused by mobility, and signal bandwidth. Multipath signals have random amplitudes and phases that cause constructive and destructive interference as the receiver moves.
3. Techniques for measuring small-scale fading and multipath include using direct radio frequency pulses or spread spectrum channel sounding with a sliding correlator. Parameters extracted from power delay profiles include mean excess delay, root mean square delay spread, and coherence bandwidth.
The document discusses routing and wavelength assignment (RWA) in wavelength-division multiplexing (WDM) networks. It covers both static and dynamic RWA problems. For routing, it discusses integer linear programming formulations for static routing and online algorithms for dynamic routing. For wavelength assignment, it discusses graph coloring approaches for static assignment and heuristics like first-fit for dynamic assignment. Several heuristics for RWA are presented, along with their computational complexities and performance. Future research directions like survivable RWA and managing multicast connections are also outlined.
This document discusses multiple-input multiple-output (MIMO) systems, including their motivations and capabilities. MIMO systems use multiple antennas at both the transmitter and receiver to achieve high data rates approaching 1 Gbps while maintaining quality of service. The document covers MIMO channel models and capacity, design criteria like diversity and spatial multiplexing, practical architectures like V-BLAST and Alamouti's scheme, and applications to networking including MIMO-OFDM and MIMO MAC protocols.
This document discusses FDMA (Frequency Division Multiple Access), a method of multiple access where a given radio frequency bandwidth is divided into smaller frequency bands. Each user is allocated a unique frequency band or channel. The key advantages of FDMA are that it does not require base station control, data transmission will not be lost, and it has simple channel operations. However, disadvantages include the inability of stations to receive from multiple sources, fixed and small data rates per channel, and wasted capacity from guard bands.
FEC-Forward Error Correction for Optics ProfessionalsMapYourTech
Forward error correction (FEC) adds redundancy to transmitted data to allow errors to be detected and corrected without retransmission. It works by encoding data at the transmitter and decoding it at the receiver. FEC provides increased transmission distance and reliability by improving the bit error rate. Reed-Solomon codes are commonly used for FEC as they can efficiently correct multiple errors within a code block. The amount of redundancy added depends on the code's error correction capability, with higher correction requiring more overhead bits.
This document discusses space division multiplexing (SDM), a new technique for fiber optic communication that increases transmission capacity. SDM utilizes unused space within the core or additional fiber cores to establish independent transmission channels. There are two main SDM strategies: multi-core fiber which has multiple cores embedded in the cladding, and multi-mode fiber which supports propagation of multiple independent modes within a single core. SDM provides significant advantages like high scalability and the ability to achieve terabit per second throughput. When combined with software defined networking, SDM networks also enable efficient infrastructure utilization and flexible bandwidth provisioning. However, SDM also faces challenges like crosstalk between cores and high insertion losses.
This document provides an overview of cellular networks and key concepts:
- It defines terminology like base station, mobile station, cells, sectors, and handoff.
- It describes early 1G and 2G cellular systems and technologies like FDMA, TDMA, CDMA.
- It covers fundamental concepts like frequency reuse, cell splitting, and forward/reverse links.
- Finally, it discusses challenges like co-channel interference and techniques for wireless quality of service and handoff management.
The document describes a digital Quadrature Amplitude Modulation (QAM) transmitter. It discusses how QAM digitally modulates information onto the amplitudes of a sine and cosine wave, or equivalently onto the amplitude and phase of a single sinusoid. The transmitter uses pulse shaping filters and a Hilbert transformer to generate the in-phase and quadrature signals from the digital bit stream before upconverting and transmitting. Performance analysis methods for QAM are also presented to calculate decision regions and probabilities of correct detection.
3rd UNIT Microwave Engineering PPT.pptxShaikShahin7
This document discusses microwave engineering and microwave cavity resonators. It provides details on:
- Microwave cavity resonators, which confine electromagnetic energy inside a metallic enclosure. The resonant frequency depends on the equivalent capacitance, inductance, and resistance of the cavity.
- Rectangular waveguide cavity resonators, which are constructed by shorting both ends of a closed waveguide section to form a cavity.
- The different modes resonant cavities can support and how maximum energy is stored at the resonant frequency.
- Common coupling mechanisms like probe coupling and loop coupling to feed or extract signals from the resonator.
This document discusses multiple access techniques for wireless communications, including FDMA, TDMA, and CDMA. It provides details on how each technique works and its advantages and disadvantages. FDMA divides the frequency band into channels that can be assigned to individual users. TDMA divides each channel into time slots that can be assigned to users. CDMA allows all users to use the whole available bandwidth simultaneously by using unique codes to distinguish users' signals.
This document provides the table of contents for the book "Satellite Communications" by Timothy Pratt and Jeremy Allnutt. The third edition of the book covers topics related to orbital mechanics, satellite subsystems, satellite link design, digital transmission, modulation, multiple access techniques, propagation effects, low throughput systems, NGSO satellite systems, direct broadcast satellite television/radio, and satellite navigation systems. The book is intended to provide comprehensive coverage of satellite communications technologies and their applications.
This document provides a course syllabus on mobile and wireless communications. The syllabus covers 4 units:
1) Wireless transmission fundamentals like frequencies, signals, and propagation effects
2) Multiplexing techniques including FDM, TDM, CDMA, and modulation methods
3) Access control mechanisms like FDMA, TDMA, CDMA and their performance
4) Wireless networks including satellite, WLAN, WATM networks and protocols
It also lists recommended textbooks for the course.
This document summarizes a study on IP over WDM networks. It discusses the motivations for using IP over WDM due to the exponential growth of IP traffic exceeding voice traffic. WDM technology allows multiple wavelengths on a single fiber, providing a good match for high capacity IP traffic needs. The document also covers IP traffic over WDM networks, MPLS approaches for IP over WDM including GMPLS control planes, and optical internetworking and signaling across network boundaries.
This document provides an introduction to error correcting codes. It discusses key concepts such as channel capacity, error detection and correction, information rate, weight and distance, maximum likelihood decoding, and linear codes. Error correcting codes add redundant bits to messages to facilitate detecting and correcting errors that may occur during transmission or storage. Linear codes allow for simpler encoding and decoding procedures compared to non-linear codes. The generator and parity check matrices are important for encoding and decoding messages using linear codes.
The document provides an overview of the GSM network architecture, including its three main subsystems: the Mobile Station subsystem, the Base Station Subsystem, and the Network Switching Subsystem. It describes the key elements and interfaces within each subsystem, such as the Mobile Station, Base Transceiver Station, Base Station Controller, Mobile Switching Center, Home Location Register, and Visitor Location Register. The interfaces that connect these elements, such as the A, Abis, and Um interfaces, are also introduced.
Small scale fading, also known as fading, describes the rapid fluctuations of signal amplitude and phase over short periods of time. It is caused by interference between multiple versions of a transmitted signal that take different paths to the receiver. This can result in changes to amplitude, phase, and time of arrival depending on factors like multipath propagation, Doppler shifts from mobile speed, movement of surrounding objects, and the signal bandwidth.
Routing is the mechanism for finding the most cost-effective path from source to destination in a packet switching network. There are several desirable properties for routing algorithms including correctness, robustness, stability, fairness, and efficiency. Common routing strategies include fixed/static routing, flooding, random routing, flow-based routing, and adaptive/dynamic routing. Fixed routing selects predetermined routes that may only change if the network topology changes, while flooding explores all possible routes by sending every incoming packet out every outgoing line except the one it arrived on.
Multi User Detection in CDMA System Using Linear and Non Linear DetectorWaqas Tariq
DS-Code division multiple access is considered as the third generation of cellular mobile used in interim standard 95(IS-95) [1]and it is currently being standardized for universal mobile telecommunication systems (UMTS). CDMA offers attractive features, such as frequency reuse, soft handoff, increased capacity, and multipath combating. In a CDMA system, several users simultaneously transmit information over a common channel using pre-assigned codes. The conventional single user detector consists of a bank of filters matched to the spreading codes. This detector suffers from two problems. First, multiple access interference (MAI) produced by the other co-channel users is a significant limitation to the capacity of this detector. The second problem is the near-far effect which occurs when the relative received power of interfering signals becomes larger. A potential solution is multi-user detection which exploits the information of signals of interfering users. In the present study performance of various linear detectors like matched filter detector, MMSE detector, and adaptive LMS detector are studied. These are the linear detectors that operate linearly on the received signal statistics and are suboptimal detectors. The matched filter bank is the conventional detector and offers the simplest way of demodulating CDMA signals .The detector resulting from the MMSE (minimum mean square error) criterion shows better performance over the conventional one for low SNR value. Adaptive LMS is employed to enhance the BER performance in MUD application.Several factors motivated the research to apply neural network as multi-user detector. NN are nonlinear classifier in addition to being adaptive and computationally efficient. The performance of two layer perceptron neural network using BP learning rule is used for multi-user detection of CDMA signals in AWGN channels. The neural network detectors show improvement of BER in the comparative analysis done in the present work. and offers further research scope for solving multi-user detection problems in CDMA application.
Spread spectrum techniques spread data signals over a wide bandwidth to make them resistant to jamming and interception. There are two main approaches: frequency hopping spread spectrum (FHSS) rapidly switches a narrowband signal across a wide band of frequencies in a pattern known only to the transmitter and receiver, while direct sequence spread spectrum (DSSS) encodes data bits by adding extra bits using a spreading code before transmission. Code division multiple access (CDMA) allows multiple users to share the same frequency band by using user-specific spreading codes, with the signals combined at the receiver.
This document discusses modeling wireless communication systems using MATLAB. It covers:
- Characterizing the wireless channel from physics of propagation to multi-path fading channels.
- Statistical characterization of channels including Doppler spectrum, delay spread, coherence time and bandwidth.
- Simulating multi-path fading channels in MATLAB and modeling path loss.
- Explaining how multi-path propagation leads to signal distortion and is equivalent to undesired filtering.
Wireless ATM (WATM) combines ATM technology with wireless networks to provide multimedia services over mobile networks. It enables services like video conferencing and distance learning across offices, schools, hospitals and other environments. Key challenges include maintaining quality of service during handovers between wireless cells and efficiently managing the location of mobile users. The Wireless ATM Working Group was formed to develop specifications allowing ATM networks to support mobility through functions like handover signaling, location management and mobile routing.
Small scale fading and multipath measurementsVrince Vimal
1. The document discusses small-scale fading and multipath measurements in wireless channels. It describes how fading occurs due to interference from multiple copies of transmitted signals arriving at the receiver at different times.
2. Key channel parameters that influence fading are discussed, including multipath propagation, Doppler shift caused by mobility, and signal bandwidth. Multipath signals have random amplitudes and phases that cause constructive and destructive interference as the receiver moves.
3. Techniques for measuring small-scale fading and multipath include using direct radio frequency pulses or spread spectrum channel sounding with a sliding correlator. Parameters extracted from power delay profiles include mean excess delay, root mean square delay spread, and coherence bandwidth.
The document discusses routing and wavelength assignment (RWA) in wavelength-division multiplexing (WDM) networks. It covers both static and dynamic RWA problems. For routing, it discusses integer linear programming formulations for static routing and online algorithms for dynamic routing. For wavelength assignment, it discusses graph coloring approaches for static assignment and heuristics like first-fit for dynamic assignment. Several heuristics for RWA are presented, along with their computational complexities and performance. Future research directions like survivable RWA and managing multicast connections are also outlined.
This document discusses multiple-input multiple-output (MIMO) systems, including their motivations and capabilities. MIMO systems use multiple antennas at both the transmitter and receiver to achieve high data rates approaching 1 Gbps while maintaining quality of service. The document covers MIMO channel models and capacity, design criteria like diversity and spatial multiplexing, practical architectures like V-BLAST and Alamouti's scheme, and applications to networking including MIMO-OFDM and MIMO MAC protocols.
This document discusses FDMA (Frequency Division Multiple Access), a method of multiple access where a given radio frequency bandwidth is divided into smaller frequency bands. Each user is allocated a unique frequency band or channel. The key advantages of FDMA are that it does not require base station control, data transmission will not be lost, and it has simple channel operations. However, disadvantages include the inability of stations to receive from multiple sources, fixed and small data rates per channel, and wasted capacity from guard bands.
FEC-Forward Error Correction for Optics ProfessionalsMapYourTech
Forward error correction (FEC) adds redundancy to transmitted data to allow errors to be detected and corrected without retransmission. It works by encoding data at the transmitter and decoding it at the receiver. FEC provides increased transmission distance and reliability by improving the bit error rate. Reed-Solomon codes are commonly used for FEC as they can efficiently correct multiple errors within a code block. The amount of redundancy added depends on the code's error correction capability, with higher correction requiring more overhead bits.
This document discusses space division multiplexing (SDM), a new technique for fiber optic communication that increases transmission capacity. SDM utilizes unused space within the core or additional fiber cores to establish independent transmission channels. There are two main SDM strategies: multi-core fiber which has multiple cores embedded in the cladding, and multi-mode fiber which supports propagation of multiple independent modes within a single core. SDM provides significant advantages like high scalability and the ability to achieve terabit per second throughput. When combined with software defined networking, SDM networks also enable efficient infrastructure utilization and flexible bandwidth provisioning. However, SDM also faces challenges like crosstalk between cores and high insertion losses.
This document provides an overview of cellular networks and key concepts:
- It defines terminology like base station, mobile station, cells, sectors, and handoff.
- It describes early 1G and 2G cellular systems and technologies like FDMA, TDMA, CDMA.
- It covers fundamental concepts like frequency reuse, cell splitting, and forward/reverse links.
- Finally, it discusses challenges like co-channel interference and techniques for wireless quality of service and handoff management.
The document describes a digital Quadrature Amplitude Modulation (QAM) transmitter. It discusses how QAM digitally modulates information onto the amplitudes of a sine and cosine wave, or equivalently onto the amplitude and phase of a single sinusoid. The transmitter uses pulse shaping filters and a Hilbert transformer to generate the in-phase and quadrature signals from the digital bit stream before upconverting and transmitting. Performance analysis methods for QAM are also presented to calculate decision regions and probabilities of correct detection.
3rd UNIT Microwave Engineering PPT.pptxShaikShahin7
This document discusses microwave engineering and microwave cavity resonators. It provides details on:
- Microwave cavity resonators, which confine electromagnetic energy inside a metallic enclosure. The resonant frequency depends on the equivalent capacitance, inductance, and resistance of the cavity.
- Rectangular waveguide cavity resonators, which are constructed by shorting both ends of a closed waveguide section to form a cavity.
- The different modes resonant cavities can support and how maximum energy is stored at the resonant frequency.
- Common coupling mechanisms like probe coupling and loop coupling to feed or extract signals from the resonator.
This document discusses multiple access techniques for wireless communications, including FDMA, TDMA, and CDMA. It provides details on how each technique works and its advantages and disadvantages. FDMA divides the frequency band into channels that can be assigned to individual users. TDMA divides each channel into time slots that can be assigned to users. CDMA allows all users to use the whole available bandwidth simultaneously by using unique codes to distinguish users' signals.
This document provides the table of contents for the book "Satellite Communications" by Timothy Pratt and Jeremy Allnutt. The third edition of the book covers topics related to orbital mechanics, satellite subsystems, satellite link design, digital transmission, modulation, multiple access techniques, propagation effects, low throughput systems, NGSO satellite systems, direct broadcast satellite television/radio, and satellite navigation systems. The book is intended to provide comprehensive coverage of satellite communications technologies and their applications.
This document provides a course syllabus on mobile and wireless communications. The syllabus covers 4 units:
1) Wireless transmission fundamentals like frequencies, signals, and propagation effects
2) Multiplexing techniques including FDM, TDM, CDMA, and modulation methods
3) Access control mechanisms like FDMA, TDMA, CDMA and their performance
4) Wireless networks including satellite, WLAN, WATM networks and protocols
It also lists recommended textbooks for the course.
This document summarizes a study on IP over WDM networks. It discusses the motivations for using IP over WDM due to the exponential growth of IP traffic exceeding voice traffic. WDM technology allows multiple wavelengths on a single fiber, providing a good match for high capacity IP traffic needs. The document also covers IP traffic over WDM networks, MPLS approaches for IP over WDM including GMPLS control planes, and optical internetworking and signaling across network boundaries.
This document provides an introduction to error correcting codes. It discusses key concepts such as channel capacity, error detection and correction, information rate, weight and distance, maximum likelihood decoding, and linear codes. Error correcting codes add redundant bits to messages to facilitate detecting and correcting errors that may occur during transmission or storage. Linear codes allow for simpler encoding and decoding procedures compared to non-linear codes. The generator and parity check matrices are important for encoding and decoding messages using linear codes.
The document provides an overview of the GSM network architecture, including its three main subsystems: the Mobile Station subsystem, the Base Station Subsystem, and the Network Switching Subsystem. It describes the key elements and interfaces within each subsystem, such as the Mobile Station, Base Transceiver Station, Base Station Controller, Mobile Switching Center, Home Location Register, and Visitor Location Register. The interfaces that connect these elements, such as the A, Abis, and Um interfaces, are also introduced.
Small scale fading, also known as fading, describes the rapid fluctuations of signal amplitude and phase over short periods of time. It is caused by interference between multiple versions of a transmitted signal that take different paths to the receiver. This can result in changes to amplitude, phase, and time of arrival depending on factors like multipath propagation, Doppler shifts from mobile speed, movement of surrounding objects, and the signal bandwidth.
Routing is the mechanism for finding the most cost-effective path from source to destination in a packet switching network. There are several desirable properties for routing algorithms including correctness, robustness, stability, fairness, and efficiency. Common routing strategies include fixed/static routing, flooding, random routing, flow-based routing, and adaptive/dynamic routing. Fixed routing selects predetermined routes that may only change if the network topology changes, while flooding explores all possible routes by sending every incoming packet out every outgoing line except the one it arrived on.
Multi User Detection in CDMA System Using Linear and Non Linear DetectorWaqas Tariq
DS-Code division multiple access is considered as the third generation of cellular mobile used in interim standard 95(IS-95) [1]and it is currently being standardized for universal mobile telecommunication systems (UMTS). CDMA offers attractive features, such as frequency reuse, soft handoff, increased capacity, and multipath combating. In a CDMA system, several users simultaneously transmit information over a common channel using pre-assigned codes. The conventional single user detector consists of a bank of filters matched to the spreading codes. This detector suffers from two problems. First, multiple access interference (MAI) produced by the other co-channel users is a significant limitation to the capacity of this detector. The second problem is the near-far effect which occurs when the relative received power of interfering signals becomes larger. A potential solution is multi-user detection which exploits the information of signals of interfering users. In the present study performance of various linear detectors like matched filter detector, MMSE detector, and adaptive LMS detector are studied. These are the linear detectors that operate linearly on the received signal statistics and are suboptimal detectors. The matched filter bank is the conventional detector and offers the simplest way of demodulating CDMA signals .The detector resulting from the MMSE (minimum mean square error) criterion shows better performance over the conventional one for low SNR value. Adaptive LMS is employed to enhance the BER performance in MUD application.Several factors motivated the research to apply neural network as multi-user detector. NN are nonlinear classifier in addition to being adaptive and computationally efficient. The performance of two layer perceptron neural network using BP learning rule is used for multi-user detection of CDMA signals in AWGN channels. The neural network detectors show improvement of BER in the comparative analysis done in the present work. and offers further research scope for solving multi-user detection problems in CDMA application.
Mobile wireless systems have progressed from 1G to 2G to 3G systems. 1G systems were the earliest analog mobile networks that suffered from low capacity and security issues. 2G systems were digital and provided higher capacity to address the problems of 1G. Both 1G and 2G focused on voice services and were not well-suited for data. 3G systems aimed to improve support for data services.
ABSTRACT : Performance enhancement of smart antennas versus their complexity for commercial wireless
applications. The goal of the study presented in this paper is to investigate the performance improvement
attainable using relatively simple smart antenna techniques when applied to the third-generation W-CDMA air
interface. Methods to achieve this goal include fixed multi beam architectures with different beam selection
algorithms (maximum power criterion, combined beams) or adaptive solutions driven by relatively simple direction
finding algorithms. After comparing these methods against each other for several representative scenarios, some
issues related to the sensitivity of these methods are also studied, (e.g., robustness to environment, mismatches
originating from implementation limitations, etc.). Results indicate that overall, conventional beam forming
seems to be the best choice in terms of balancing the performance and complexity requirements, in particular
when the problem with interfering high-bit-rate W-CDMA 3g users is considered.
This document discusses Code Division Multiple Access (CDMA) cellular radio networks. It describes the key components of a CDMA network including the mobile station, base station subsystem, and network subsystem. It explains how CDMA works by allocating different codes to users allowing multiple users to transmit over the same radio channel simultaneously. The advantages of CDMA include spread spectrum communication, soft handoff, and high quality voice. Disadvantages include the near-far problem and lower network capacity compared to GSM initially. The document concludes that CDMA is superior to other multiple access techniques and is an important technique in radio communications.
An Efficient Call Admission Control Scheme for Handling Handoffs in Wireless ...pijans
Personal Communication Network (PCN) is an emerging wireless network that promises many new
services for the telecommunication industry. The proliferation of demands for extending wireless services
to integrated services, which supports the transmission of data and multimedia information, has resulted in
the need for broadband wireless systems that are able to provide service capabilities similar to those of
wire line networks. The ATM cell - relay paradigm is one possible approach to provide broadband wireless
transmission with PCN’s using the ATM switching networks for interconnection of PCN cells. As traffic in
these mobile cellular networks increases, Handoffs will become an increasingly important issue. As cell
sizes shrink to accommodate an increasingly large demand of services, newer more efficient handoff
schemes need to be used. In this paper, the authors describe the use of novel and efficient data structure
which dynamically allocates guard channel for handoffs and introduces the concept of channel borrowing
strategy. The proposed scheme allocates the guard channels for handoff requests dynamically, based on the
traffic load for certain time period. A new originating call in the cell coverage area also uses these guard
channels if they are unused. Our basic idea is to allow Guard channels to be shared between new calls and
handoff calls. This approach maximizes the channel utilization. The simulation results prove that the
channel borrowing scheme improves the overall throughput.
The document discusses the evolution of wireless communication technologies through generations from 2G to 4G. It describes the key characteristics and speed capabilities of each generation. It also provides details on various wireless networking components and concepts such as channel access schemes, radio signals, BTS, BSC, MSC, HLR, AuC, EIR and SMSC.
The document discusses Wide Band Division Multiple Access (WCDMA) and provides details about its history, frequency bands used, network architecture, channels, and key components like Node B, RNC, CN, HLR, VLR, AuC, EIR, and OMC. WCDMA is a 3G mobile communication system standardized by ITU in 1985 as IMT-2000. It uses CDMA technology and allows multiple users to access the same frequency channel simultaneously through the use of unique codes.
Estimation and design of mc ds-cdma for hybrid concatenated coding in high sp...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Estimation and design of mc ds-cdma for hybrid concatenated coding in high sp...eSAT Journals
Abstract The design of Multi Carrier Direct Sequence Code Division Multiple Access (MC-DS-CDMA) structure which generalizes serial and parallel concatenated code is investigated to this project. This model is ideal for designing various codes in the performance of both error floor and water floor region. We propose a concatenated code for transmitter block which is used for multi carrier direct sequence CDMA technique. Simulation results of MC-DS-CDMA uplink system using Cadence software shows the various parameters such as memory, Execution time and number of transient steps required for the Execution of MC-DS-CDMA uplink system was estimated and also power consumed was determined for each block in the transmitter. An improved concatenated code model is used for uplink mobile communication. Further system performance improvements can be obtained by concatenating inner code and outer code and the results of computer simulations demonstrate that the performance of the concatenated code was investigated. Keywords: Code Division Multiple Access, Concatenated code, inner code, outer code, interleaving and power analysis.
This document discusses wireless communication and GSM networks. It provides an overview of multiple access techniques used in wireless networks like TDMA, FDMA, and CDMA. It then describes the development and standards of GSM networks and how they were created to provide a digital cellular standard across Europe to resolve issues with different analog 1G systems. Finally, it summarizes the call setup process in a GSM network for a mobile terminated call, including analyzing the number, interrogating the HLR and MSC/VLR, generating a temporary MSRN, and initiating paging to locate the called subscriber.
GSM (Global System for Mobile communications) is a digital cellular network developed to provide improved spectrum efficiency, international roaming, and compatibility with other networks. It uses TDMA to allow multiple users to access the same radio frequency channel at different time slots. The GSM architecture consists of mobile stations, a base station subsystem including base transceiver stations and base station controllers, and a network subsystem including mobile switching centers and databases like the home location register.
This document provides an overview of CDMA (Code Division Multiple Access), including its access schemes, coding, codes, spreading process, power control, handover, multipath and rake receivers. It describes how CDMA uses unique spreading codes to spread data before transmission. Receivers use correlators to despread the signal and filters to isolate the desired signal from interference. Power control is important to limit interference in this interference-limited system. Soft handovers allow connections between multiple cells. Multipath signals are combined using rake receivers to strengthen the signal.
The document discusses ad-hoc networks and their key characteristics. It describes several challenges in ad-hoc networks including limited battery power, dynamic network topology, and scalability issues. It also summarizes several ad-hoc network routing protocols (e.g. DSDV, AODV, DSR), addressing both table-driven and on-demand approaches. Additionally, it outlines some ad-hoc MAC protocols like MACA and PAMAS that aim to manage shared wireless medium access.
A QoS Based MAC Protocol For Wireless Ad-hoc NetworkIJNSA Journal
Multimedia communication over wireless Ad-hoc networks has become the driving technology for many of the important applications, experiencing dramatic market growth and promising revolutionary experiences in personal communication, gaming, entertainment, military, security, environment monitoring, and more. The advances in wireless communications and growth of real-time applications have necessitated the development of wireless networks that can support high Quality of Service (QoS) and power control. A node in an ad hoc network is normally battery operated which poses a huge constraint on the power consumption of such a node. Hence, designing a power efficient MAC protocol for ad hoc wireless networks is a major challenge. In this paper, we propose a CDMA based power controlled medium access protocol for mobile and ad hoc network (MNA). The protocol conserves power and provides QoS guarantees for multimedia traffics. In that network one of the fundamental challenger in MANETs is how to increase the overall network throughputs well as reading the delay while maintaining how energy consumption for packet processing in communication. simulation results shows that the performance of the protocol with increase in traffic while QoS is better in terms of Energy consumption, throughput, & communication delay than existing protocol.
GSM (Global System for Mobile Communications) is the second generation (2G) digital cellular standard developed in Europe in the 1980s. It uses TDMA (Time Division Multiple Access) and FDMA (Frequency Division Multiple Access) to allow multiple users to access the network simultaneously. The key components of a GSM network are the base station, base station controller, mobile switching center, home location register, and visitor location register. GSM networks operate on various frequency bands and use logical channels to transmit different types of information like voice calls, SMS messages, and signaling data. GSM became the most widely used 2G standard globally due to its widespread adoption in Europe and other regions.
1. The document discusses various topics related to data communication and computer networks including Point to Point Protocol (PPP), media access control, multiplexing techniques like frequency division multiplexing (FDM), wavelength division multiplexing (WDM), and time division multiplexing (TDM), and controlled access methods like reservation, polling, and token passing.
2. It provides details on PPP components, types of multiplexers, uses of FDM and WDM, synchronous and asynchronous TDM, and how reservation, polling, and token passing control access to shared media.
3. Controlled access methods like token passing aim to prevent collisions by allowing only one node to transmit at a time, while random access techniques
Code Division Multiple Access (CDMA) could be a digital cellular tec.pdfannamalassociates
Code Division Multiple Access (CDMA) could be a digital cellular technology used for mobile
communication. CDMA is that the base on that access strategies like cdmaOne, CDMA-2000,
and WCDMA area unit designed. CDMA cellular systems area unit deemed superior to FDMA
and TDMA, that is why CDMA plays a essential role in building economical, robust, and secure
radio communication systems.
A Simple Analogy
Let’s take an easy analogy to grasp the thought of CDMA. Assume we\'ve a couple of students
gathered in a very room WHO would really like to speak to every alternative at the same time.
Nothing would be sonic if everybody starts speaking at constant time. Either they need to
alternate to talk or use totally different languages to speak.
The second choice is kind of just like CDMA students speaking constant language will perceive
one another, whereas alternative languages area unit perceived as noise and rejected. Similarly,
in radio CDMA, every cluster of users is given a shared code. several codes occupy constant
channel, however solely those users related to a selected code will communicate.
Salient options of CDMA
CDMA, that is predicated on the unfold spectrum technique has following salient options
In CDMA, each channel uses the total accessible spectrum.
Individual conversations area unit encoded with a pseudo-random digital sequence so transmitted
employing a wide frequency vary.
CDMA systematically provides higher capability for voice and knowledge communications,
permitting a lot of subscribers to attach at any given time.
CDMA is that the common platform on that 3G technologies area unit designed. For 3G, CDMA
uses 1x EV-DO and EV-DV.
Third Generation Standards
CDMA2000 uses Frequency Division Duplexing-Multicarrier (FDD-MC) mode. Here,
multicarrier implies N × one.25 Mc channels overlaid on N existing IS-95 carriers or deployed
on unoccupied spectrum. CDMA2000 includes
1x — uses a spreading rate of one.2288 Mcps.
3x — uses a spreading rate of three × one.2288 Mcps or three.6864 Mcps.
1xEV-DO (1x Evolution – knowledge Optimized) — uses a spreading rate of one.2288 Mcps,
optimized for the info.
WCDMA/FDD-DS — band CDMA (WCDMA) Frequency Division Duplexing-Direct Sequence
spreading (FDD-DS) mode. This encompasses a single five Mc channel. WCDMA uses one
carrier per channel and employs a spreading rate of three.84 Mcps.
CDMA Development cluster (CDG)
The CDMA Development cluster (CDG), supported in Dec 1993, is a world pool of firms. It
works along to steer the expansion and evolution of advanced wireless telecommunication
systems.
CDG is comprised of service suppliers, infrastructure makers, device vendors, equipment
vendors, application developers, and content suppliers. Its members put together outline the
technical needs for the event of complementary systems CDMA2000 and 4G. Further, the ability
with alternative rising wireless technologies area unit meant to extend the provision of wireless
merchandise and services to customers and .
CDMA is a technique that allows multiple users to access the network using the same frequency band at the same time. It works by spreading each user's signal across the entire bandwidth using unique codes. This allows signals to overlap without interfering with each other. Key advantages of CDMA include larger network capacity, less transmit power per user, seamless handoffs between cells, no need for frequency planning, high tolerance of interference, and multiple diversity techniques. A typical CDMA network can support 400 subscribers per sector using 1.25MHz of spectrum, allowing a cell with 6 sectors to support up to 2,400 subscribers on a single frequency channel.
An investigation-on-efficient-spreading-codes-for-transmitter-based-technique...Cemal Ardil
This document summarizes research on efficient spreading codes for transmitter-based techniques to mitigate interference in time division duplex code division multiple access (TDD/CDMA) downlink systems. It investigates bitwise and blockwise multiuser transmission schemes that transfer complexity to the transmitter. Different spreading codes are evaluated based on correlation properties to determine suitability for techniques like precoding, pre-rake, and rake diversity. Performance is measured by bit error rate with varying numbers of users to identify the most efficient codes for interference mitigation.
Similar to MATLAB Implementation of Multiuser Code Division Multiple Access (20)
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
An improved modulation technique suitable for a three level flying capacitor ...IJECEIAES
This research paper introduces an innovative modulation technique for controlling a 3-level flying capacitor multilevel inverter (FCMLI), aiming to streamline the modulation process in contrast to conventional methods. The proposed
simplified modulation technique paves the way for more straightforward and
efficient control of multilevel inverters, enabling their widespread adoption and
integration into modern power electronic systems. Through the amalgamation of
sinusoidal pulse width modulation (SPWM) with a high-frequency square wave
pulse, this controlling technique attains energy equilibrium across the coupling
capacitor. The modulation scheme incorporates a simplified switching pattern
and a decreased count of voltage references, thereby simplifying the control
algorithm.
artificial intelligence and data science contents.pptxGauravCar
What is artificial intelligence? Artificial intelligence is the ability of a computer or computer-controlled robot to perform tasks that are commonly associated with the intellectual processes characteristic of humans, such as the ability to reason.
› ...
Artificial intelligence (AI) | Definitio
Batteries -Introduction – Types of Batteries – discharging and charging of battery - characteristics of battery –battery rating- various tests on battery- – Primary battery: silver button cell- Secondary battery :Ni-Cd battery-modern battery: lithium ion battery-maintenance of batteries-choices of batteries for electric vehicle applications.
Fuel Cells: Introduction- importance and classification of fuel cells - description, principle, components, applications of fuel cells: H2-O2 fuel cell, alkaline fuel cell, molten carbonate fuel cell and direct methanol fuel cells.
Applications of artificial Intelligence in Mechanical Engineering.pdfAtif Razi
Historically, mechanical engineering has relied heavily on human expertise and empirical methods to solve complex problems. With the introduction of computer-aided design (CAD) and finite element analysis (FEA), the field took its first steps towards digitization. These tools allowed engineers to simulate and analyze mechanical systems with greater accuracy and efficiency. However, the sheer volume of data generated by modern engineering systems and the increasing complexity of these systems have necessitated more advanced analytical tools, paving the way for AI.
AI offers the capability to process vast amounts of data, identify patterns, and make predictions with a level of speed and accuracy unattainable by traditional methods. This has profound implications for mechanical engineering, enabling more efficient design processes, predictive maintenance strategies, and optimized manufacturing operations. AI-driven tools can learn from historical data, adapt to new information, and continuously improve their performance, making them invaluable in tackling the multifaceted challenges of modern mechanical engineering.