1. OFDM divides a high-speed data stream into multiple lower-speed streams that are transmitted over subcarriers in parallel to mitigate the effects of multipath propagation such as inter-symbol interference.
2. A guard interval is inserted between OFDM symbols to eliminate inter-symbol interference from delayed multipath signals.
3. At the receiver, the guard interval is removed and an inverse fast Fourier transform (IFFT) is applied to convert the signal back to the time domain for decoding.
Data Communication & Computer Networks: Multi level, multi transition & block...Dr Rajiv Srivastava
These slides cover the fundamentals of data communication & networking. It covers Multi level, Multi transition and Block codes which are used in communication of data. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
This document discusses digital-to-digital conversion techniques for transmitting digital data, including line coding, block coding, and scrambling. It describes line coding as the process of converting digital data to digital signals. Common line coding schemes include NRZ-L, NRZ-I, RZ, Manchester, and AMI. Block coding and scrambling may also be used and involve techniques like B8ZS and HDB3. Digital data can be transmitted serially or in parallel, with serial transmission divided into asynchronous, synchronous, and isochronous modes.
This document summarizes the simulation of a turbo coded orthogonal frequency division multiplexing (OFDM) system. Key points:
1) OFDM divides a wideband channel into narrowband channels to mitigate multipath fading effects. Turbo codes are added to OFDM to improve performance at high data rates.
2) Turbo codes use parallel concatenated convolutional codes for encoding and iterative decoding. Simulation shows turbo coded OFDM outperforms uncoded OFDM with lower bit error rates over both additive white Gaussian noise and Rayleigh fading channels.
3) The simulation model includes a turbo encoder, QAM modulation, IFFT/FFT, channel with noise, turbo decoder. Results show turbo coded OFDM provides much
1) OFDM uses multiple carriers to transmit data in parallel. It can be described mathematically using the Fourier transform which relates events in the time and frequency domains.
2) At the transmitter, the signal is defined in the frequency domain using a discrete Fourier transform and generated using the inverse discrete Fourier transform. This allows the carriers to be orthogonal.
3) A guard interval is added between symbols to prevent intersymbol interference from multipath distortion. This increases the symbol duration and provides timing tolerance at the receiver.
The document discusses digital transmission methods including analog to digital conversion techniques. It covers the following:
- Pulse code modulation (PCM) is described as the most common technique for converting analog signals to digital data. It involves sampling, quantizing, and encoding the quantized values as a bit stream.
- Block coding techniques like 4B/5B and 8B/10B are discussed as ways to add redundancy for synchronization and error detection when transmitting digital data. Scrambling techniques are also introduced to avoid long runs of zeros for synchronization.
- The Nyquist sampling theorem states that to reproduce an analog signal, the sampling rate must be at least twice the highest frequency contained in the signal. Sampling
This document discusses digital transmission and analog-to-digital conversion. It describes how an analog signal is converted to a digital signal using pulse code modulation (PCM). PCM involves sampling, quantizing, and encoding an analog signal. The document then discusses various digital carrier systems like T1, components of a digital terminal, and codecs used in digital transmission.
Data Communication And Networking - DIGITAL TRANSMISSIONAvijeet Negel
This document discusses digital-to-digital conversion techniques, including line coding, block coding, and scrambling. Line coding is used to convert digital data into a sequence of signals representing 1s and 0s. It involves mapping data symbols to signal levels using techniques like non-return-to-zero (NRZ) coding, Manchester coding, and multilevel coding to increase data rates. Factors like baseline wandering, synchronization, error detection, and noise immunity must be considered when choosing a line coding scheme. Block coding and scrambling may also be used but are not always necessary.
Data Communication & Computer Networks: Multi level, multi transition & block...Dr Rajiv Srivastava
These slides cover the fundamentals of data communication & networking. It covers Multi level, Multi transition and Block codes which are used in communication of data. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
This document discusses digital-to-digital conversion techniques for transmitting digital data, including line coding, block coding, and scrambling. It describes line coding as the process of converting digital data to digital signals. Common line coding schemes include NRZ-L, NRZ-I, RZ, Manchester, and AMI. Block coding and scrambling may also be used and involve techniques like B8ZS and HDB3. Digital data can be transmitted serially or in parallel, with serial transmission divided into asynchronous, synchronous, and isochronous modes.
This document summarizes the simulation of a turbo coded orthogonal frequency division multiplexing (OFDM) system. Key points:
1) OFDM divides a wideband channel into narrowband channels to mitigate multipath fading effects. Turbo codes are added to OFDM to improve performance at high data rates.
2) Turbo codes use parallel concatenated convolutional codes for encoding and iterative decoding. Simulation shows turbo coded OFDM outperforms uncoded OFDM with lower bit error rates over both additive white Gaussian noise and Rayleigh fading channels.
3) The simulation model includes a turbo encoder, QAM modulation, IFFT/FFT, channel with noise, turbo decoder. Results show turbo coded OFDM provides much
1) OFDM uses multiple carriers to transmit data in parallel. It can be described mathematically using the Fourier transform which relates events in the time and frequency domains.
2) At the transmitter, the signal is defined in the frequency domain using a discrete Fourier transform and generated using the inverse discrete Fourier transform. This allows the carriers to be orthogonal.
3) A guard interval is added between symbols to prevent intersymbol interference from multipath distortion. This increases the symbol duration and provides timing tolerance at the receiver.
The document discusses digital transmission methods including analog to digital conversion techniques. It covers the following:
- Pulse code modulation (PCM) is described as the most common technique for converting analog signals to digital data. It involves sampling, quantizing, and encoding the quantized values as a bit stream.
- Block coding techniques like 4B/5B and 8B/10B are discussed as ways to add redundancy for synchronization and error detection when transmitting digital data. Scrambling techniques are also introduced to avoid long runs of zeros for synchronization.
- The Nyquist sampling theorem states that to reproduce an analog signal, the sampling rate must be at least twice the highest frequency contained in the signal. Sampling
This document discusses digital transmission and analog-to-digital conversion. It describes how an analog signal is converted to a digital signal using pulse code modulation (PCM). PCM involves sampling, quantizing, and encoding an analog signal. The document then discusses various digital carrier systems like T1, components of a digital terminal, and codecs used in digital transmission.
Data Communication And Networking - DIGITAL TRANSMISSIONAvijeet Negel
This document discusses digital-to-digital conversion techniques, including line coding, block coding, and scrambling. Line coding is used to convert digital data into a sequence of signals representing 1s and 0s. It involves mapping data symbols to signal levels using techniques like non-return-to-zero (NRZ) coding, Manchester coding, and multilevel coding to increase data rates. Factors like baseline wandering, synchronization, error detection, and noise immunity must be considered when choosing a line coding scheme. Block coding and scrambling may also be used but are not always necessary.
This document summarizes key concepts from a lecture on data communications and networking. It discusses various encoding techniques used to convert digital signals to analog forms suitable for transmission, including RZ, Manchester, differential Manchester, bipolar, AMI, and block coding methods like 4B/5B. It also covers the processes of sampling analog signals to create digital forms using PAM and PCM, and discusses the Nyquist theorem as it relates to sufficient sampling rates to avoid aliasing. The document provides examples and explanations of these various encoding and sampling concepts.
Manchester & Differential Manchester encoding schemeArunabha Saha
The two main variants of biphase encoding techniques are discussed here. Manchester and Differential Manchester encoding scheme are explained with examples. Comparison between several classes of polar encoding techniques are done along with the exposure about the advantages and disadvantages of both schemes.
This document discusses digital-to-digital conversion techniques, including line coding, block coding, and scrambling. Line coding is used to convert digital data into a sequence of signals representing 1s and 0s. Several line coding schemes are described, including unipolar, polar, return-to-zero, biphase, and multilevel coding. Characteristics of different schemes such as bandwidth requirements, synchronization capabilities, and error detection are also covered. The goal of these techniques is to increase data rates while reducing signal rates through efficient encoding of digital data into electrical signals.
This document discusses multiplexing techniques for bandwidth utilization including frequency-division multiplexing (FDM), wavelength-division multiplexing (WDM), time-division multiplexing (TDM), and statistical time-division multiplexing. It provides examples of combining multiple analog or digital signals into a single transmission medium and discusses frame rates, bit rates, and slot durations. Synchronization and data rate management techniques are also covered to efficiently allocate bandwidth when input link speeds are mismatched.
This document discusses various methods for digital transmission, including:
- Digital-to-digital conversion techniques like line coding, block coding, and scrambling.
- Analog-to-digital conversion techniques like pulse code modulation (PCM) which involves sampling, quantization, and encoding an analog signal into a digital bitstream.
- Different line coding schemes like bipolar, polar, and multilevel coding and their considerations for minimizing issues like baseline wandering and DC components.
- Transmission modes like parallel, asynchronous serial, and synchronous serial transmission and their relative advantages for speed and cost.
These slides cover the fundamentals of data communication & networking. it covers LZ algorithms which are used in communication of data over transmission medium. it is useful for engineering students & also for the candidates who want to master data communication & computer networking.
The document discusses digital-to-digital and analog-to-digital conversion techniques. It covers line coding schemes such as unipolar NRZ, polar, bipolar, multilevel, and multiline transmission. It also discusses block coding, scrambling, and pulse code modulation for analog-to-digital conversion. The key steps of PCM encoding are sampling, quantization, and encoding the analog signal into digital data.
This document provides an overview of a lecture on data communications and networking. It discusses various topics related to line coding, including conversion methods, characteristics of line coding, and different line coding schemes. Specifically, it defines line coding as the process of converting binary data to a digital signal, and discusses signal level, data rate, pulse rate, DC component, and self-synchronization in the context of line coding. It also explains different line coding schemes such as unipolar, polar, NRZ, RZ, Manchester, and bipolar encoding.
The document discusses analog-to-digital conversion techniques. It describes pulse code modulation (PCM) which involves sampling an analog signal, quantizing the sample amplitudes, and encoding the quantized values into binary digits. It also describes delta modulation which encodes changes in signal amplitude rather than absolute values. PCM provides higher quality reconstruction of signals but requires a higher bit rate. The Nyquist sampling theorem states the minimum required sampling rate is twice the highest frequency component of the signal.
This document provides an overview of digital transmission techniques, including:
- Digital-to-digital conversion techniques like line coding, block coding, and scrambling.
- Analog-to-digital conversion using pulse code modulation and delta modulation.
- Transmission modes like parallel, asynchronous serial, and synchronous serial transmission.
It includes examples and diagrams illustrating key concepts like Nyquist sampling rate, PCM encoding and decoding, delta modulation, and asynchronous vs synchronous serial transmission.
Tables and figures are provided summarizing common line coding schemes and the 4B/5B block coding mapping codes.
This document describes a MATLAB code project on an FHSS (Frequency Hopped Spread Spectrum) system. It includes the theory of FHSS, block diagrams of the transmitter and receiver, and an explanation of the improved security method used. The project generates bit sequences, modulates the signal, creates an improved PN sequence, and performs frequency hopping to generate the spread signal. Output plots generated in MATLAB are included and analyzed. The results match the theoretical background. In conclusion, the document demonstrates implementing and analyzing an FHSS system in MATLAB to improve security.
Data Communication & Computer Networks : Unipolar & Polar codingDr Rajiv Srivastava
This document discusses different line coding schemes used for data transmission and conversion. It begins by describing different data conversion techniques such as digital to digital, line coding, block coding, scrambling, analog to digital conversion, and digital to analog conversion. It then discusses the main categories of line coding schemes and focuses on polar encoding techniques including Non-Return to Zero (NRZ), Return to Zero (RZ), and biphase encoding such as Manchester encoding and differential Manchester encoding. Specific details are provided on how each scheme encodes binary data into signals. Common applications of these coding schemes in standards such as Ethernet and token ring networks are also mentioned.
Time Division Multiplexing (TDM) can operate synchronously or asynchronously. TDM structures include bit interleaving and word interleaving. The E1 and T1 systems use different coding and have different frame sizes, with E1 providing 2.048 Mbps bandwidth and T1 providing 1.544 Mbps bandwidth. Framing establishes synchronization by adding bits or channels and can be lost due to sample clock slip or channel errors. Added-digit framing inserts alternating framing bits, while added-channel framing establishes an extra channel for framing.
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion methods like line coding, block coding, and scrambling. It also covers analog-to-digital conversion techniques such as pulse code modulation and delta modulation. Additionally, it examines transmission modes including parallel, asynchronous serial, synchronous serial, and isochronous serial transmission. Key concepts covered include line coding schemes, sampling rates, quantization, encoding, decoding, and parallel versus serial data transmission.
The document discusses various topics related to digital transmission including:
1. Digital-to-digital conversion techniques like line coding, block coding, and scrambling that are used to represent digital data with digital signals. Line coding is always needed while block coding and scrambling may or may not be needed.
2. Analog-to-digital conversion techniques like pulse code modulation (PCM) and delta modulation that are used to convert analog signals to digital data. PCM involves sampling, quantization, and encoding of analog signals.
3. Transmission modes including parallel transmission of multiple bits together and serial transmission of one bit at a time. Serial transmission can be asynchronous, synchronous, or isochronous depending
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion through line coding, block coding, and scrambling. It also covers analog-to-digital conversion using pulse code modulation and delta modulation. Finally, it examines different transmission modes including parallel, asynchronous serial, synchronous serial, and isochronous serial transmission. The document contains diagrams and examples to illustrate key concepts in digital signal processing.
Chapter 4 digital transmission computer_networkDhairya Joshi
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion through line coding, block coding, and scrambling. It also covers analog-to-digital conversion using pulse code modulation and delta modulation. Finally, it examines parallel and serial transmission modes, including asynchronous, synchronous, and isochronous serial transmission. The document contains diagrams illustrating these techniques and examples applying related concepts.
This document discusses pseudo-noise (PN) sequences, which are random-looking bit sequences that repeat periodically and have useful properties for applications like code division multiple access (CDMA) networks. It outlines a 15-stage PN generator using a shift register, describes the properties of equal probability of 1s and 0s and high auto-correlation. It also discusses how PN sequences are used for data detection through correlation and includes a MATLAB code example to generate a PN sequence.
The document discusses different types of switched networks, including circuit-switched networks, datagram networks, and virtual-circuit networks. It provides examples of how each type can be used and their characteristics. The document also describes the structure of switches used in different network types, including crossbar switches, multistage switches, time-slot interchange switches, and banyan switches. Key aspects like resource reservation, routing, addressing, and delays are compared between the different network types.
Phuong writes to her friend John about the film Titanic, which she recently watched and was impressed by its beautiful scenes and love story. She recommends the film highly and believes John and his girlfriend would enjoy it for Valentine's Day. The film is a 1997 American epic romance, drama and disaster film directed by James Cameron about the sinking of the RMS Titanic in 1912. It stars Leonardo DiCaprio and Kate Winslet and also tells a fictionalized love story between two people from different social classes who fall in love on the ill-fated maiden voyage.
This document summarizes key concepts from a lecture on data communications and networking. It discusses various encoding techniques used to convert digital signals to analog forms suitable for transmission, including RZ, Manchester, differential Manchester, bipolar, AMI, and block coding methods like 4B/5B. It also covers the processes of sampling analog signals to create digital forms using PAM and PCM, and discusses the Nyquist theorem as it relates to sufficient sampling rates to avoid aliasing. The document provides examples and explanations of these various encoding and sampling concepts.
Manchester & Differential Manchester encoding schemeArunabha Saha
The two main variants of biphase encoding techniques are discussed here. Manchester and Differential Manchester encoding scheme are explained with examples. Comparison between several classes of polar encoding techniques are done along with the exposure about the advantages and disadvantages of both schemes.
This document discusses digital-to-digital conversion techniques, including line coding, block coding, and scrambling. Line coding is used to convert digital data into a sequence of signals representing 1s and 0s. Several line coding schemes are described, including unipolar, polar, return-to-zero, biphase, and multilevel coding. Characteristics of different schemes such as bandwidth requirements, synchronization capabilities, and error detection are also covered. The goal of these techniques is to increase data rates while reducing signal rates through efficient encoding of digital data into electrical signals.
This document discusses multiplexing techniques for bandwidth utilization including frequency-division multiplexing (FDM), wavelength-division multiplexing (WDM), time-division multiplexing (TDM), and statistical time-division multiplexing. It provides examples of combining multiple analog or digital signals into a single transmission medium and discusses frame rates, bit rates, and slot durations. Synchronization and data rate management techniques are also covered to efficiently allocate bandwidth when input link speeds are mismatched.
This document discusses various methods for digital transmission, including:
- Digital-to-digital conversion techniques like line coding, block coding, and scrambling.
- Analog-to-digital conversion techniques like pulse code modulation (PCM) which involves sampling, quantization, and encoding an analog signal into a digital bitstream.
- Different line coding schemes like bipolar, polar, and multilevel coding and their considerations for minimizing issues like baseline wandering and DC components.
- Transmission modes like parallel, asynchronous serial, and synchronous serial transmission and their relative advantages for speed and cost.
These slides cover the fundamentals of data communication & networking. it covers LZ algorithms which are used in communication of data over transmission medium. it is useful for engineering students & also for the candidates who want to master data communication & computer networking.
The document discusses digital-to-digital and analog-to-digital conversion techniques. It covers line coding schemes such as unipolar NRZ, polar, bipolar, multilevel, and multiline transmission. It also discusses block coding, scrambling, and pulse code modulation for analog-to-digital conversion. The key steps of PCM encoding are sampling, quantization, and encoding the analog signal into digital data.
This document provides an overview of a lecture on data communications and networking. It discusses various topics related to line coding, including conversion methods, characteristics of line coding, and different line coding schemes. Specifically, it defines line coding as the process of converting binary data to a digital signal, and discusses signal level, data rate, pulse rate, DC component, and self-synchronization in the context of line coding. It also explains different line coding schemes such as unipolar, polar, NRZ, RZ, Manchester, and bipolar encoding.
The document discusses analog-to-digital conversion techniques. It describes pulse code modulation (PCM) which involves sampling an analog signal, quantizing the sample amplitudes, and encoding the quantized values into binary digits. It also describes delta modulation which encodes changes in signal amplitude rather than absolute values. PCM provides higher quality reconstruction of signals but requires a higher bit rate. The Nyquist sampling theorem states the minimum required sampling rate is twice the highest frequency component of the signal.
This document provides an overview of digital transmission techniques, including:
- Digital-to-digital conversion techniques like line coding, block coding, and scrambling.
- Analog-to-digital conversion using pulse code modulation and delta modulation.
- Transmission modes like parallel, asynchronous serial, and synchronous serial transmission.
It includes examples and diagrams illustrating key concepts like Nyquist sampling rate, PCM encoding and decoding, delta modulation, and asynchronous vs synchronous serial transmission.
Tables and figures are provided summarizing common line coding schemes and the 4B/5B block coding mapping codes.
This document describes a MATLAB code project on an FHSS (Frequency Hopped Spread Spectrum) system. It includes the theory of FHSS, block diagrams of the transmitter and receiver, and an explanation of the improved security method used. The project generates bit sequences, modulates the signal, creates an improved PN sequence, and performs frequency hopping to generate the spread signal. Output plots generated in MATLAB are included and analyzed. The results match the theoretical background. In conclusion, the document demonstrates implementing and analyzing an FHSS system in MATLAB to improve security.
Data Communication & Computer Networks : Unipolar & Polar codingDr Rajiv Srivastava
This document discusses different line coding schemes used for data transmission and conversion. It begins by describing different data conversion techniques such as digital to digital, line coding, block coding, scrambling, analog to digital conversion, and digital to analog conversion. It then discusses the main categories of line coding schemes and focuses on polar encoding techniques including Non-Return to Zero (NRZ), Return to Zero (RZ), and biphase encoding such as Manchester encoding and differential Manchester encoding. Specific details are provided on how each scheme encodes binary data into signals. Common applications of these coding schemes in standards such as Ethernet and token ring networks are also mentioned.
Time Division Multiplexing (TDM) can operate synchronously or asynchronously. TDM structures include bit interleaving and word interleaving. The E1 and T1 systems use different coding and have different frame sizes, with E1 providing 2.048 Mbps bandwidth and T1 providing 1.544 Mbps bandwidth. Framing establishes synchronization by adding bits or channels and can be lost due to sample clock slip or channel errors. Added-digit framing inserts alternating framing bits, while added-channel framing establishes an extra channel for framing.
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion methods like line coding, block coding, and scrambling. It also covers analog-to-digital conversion techniques such as pulse code modulation and delta modulation. Additionally, it examines transmission modes including parallel, asynchronous serial, synchronous serial, and isochronous serial transmission. Key concepts covered include line coding schemes, sampling rates, quantization, encoding, decoding, and parallel versus serial data transmission.
The document discusses various topics related to digital transmission including:
1. Digital-to-digital conversion techniques like line coding, block coding, and scrambling that are used to represent digital data with digital signals. Line coding is always needed while block coding and scrambling may or may not be needed.
2. Analog-to-digital conversion techniques like pulse code modulation (PCM) and delta modulation that are used to convert analog signals to digital data. PCM involves sampling, quantization, and encoding of analog signals.
3. Transmission modes including parallel transmission of multiple bits together and serial transmission of one bit at a time. Serial transmission can be asynchronous, synchronous, or isochronous depending
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion through line coding, block coding, and scrambling. It also covers analog-to-digital conversion using pulse code modulation and delta modulation. Finally, it examines different transmission modes including parallel, asynchronous serial, synchronous serial, and isochronous serial transmission. The document contains diagrams and examples to illustrate key concepts in digital signal processing.
Chapter 4 digital transmission computer_networkDhairya Joshi
This document summarizes different techniques for digital transmission and conversion. It discusses digital-to-digital conversion through line coding, block coding, and scrambling. It also covers analog-to-digital conversion using pulse code modulation and delta modulation. Finally, it examines parallel and serial transmission modes, including asynchronous, synchronous, and isochronous serial transmission. The document contains diagrams illustrating these techniques and examples applying related concepts.
This document discusses pseudo-noise (PN) sequences, which are random-looking bit sequences that repeat periodically and have useful properties for applications like code division multiple access (CDMA) networks. It outlines a 15-stage PN generator using a shift register, describes the properties of equal probability of 1s and 0s and high auto-correlation. It also discusses how PN sequences are used for data detection through correlation and includes a MATLAB code example to generate a PN sequence.
The document discusses different types of switched networks, including circuit-switched networks, datagram networks, and virtual-circuit networks. It provides examples of how each type can be used and their characteristics. The document also describes the structure of switches used in different network types, including crossbar switches, multistage switches, time-slot interchange switches, and banyan switches. Key aspects like resource reservation, routing, addressing, and delays are compared between the different network types.
Phuong writes to her friend John about the film Titanic, which she recently watched and was impressed by its beautiful scenes and love story. She recommends the film highly and believes John and his girlfriend would enjoy it for Valentine's Day. The film is a 1997 American epic romance, drama and disaster film directed by James Cameron about the sinking of the RMS Titanic in 1912. It stars Leonardo DiCaprio and Kate Winslet and also tells a fictionalized love story between two people from different social classes who fall in love on the ill-fated maiden voyage.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms for those who already suffer from conditions like anxiety and depression.
Phuong writes to her friend John about the film Titanic, which she recently watched and was impressed by its beautiful scenes and love story. She recommends the film highly and believes John and his girlfriend would enjoy it for Valentine's Day. The film is a 1997 American epic romance, drama and disaster film directed by James Cameron about the sinking of the RMS Titanic in 1912. It stars Leonardo DiCaprio and Kate Winslet and also tells a fictionalized love story between two people from different social classes who fall in love on the ill-fated maiden voyage.
Teks logam baja dibuat dengan menambahkan berbagai efek layer style seperti drop shadow, bevel and emboss, gradient overlay, dan pattern overlay pada teks di Photoshop, lalu mengatur parameternya sesuai contoh gambar untuk menciptakan ilusi bahwa teks tersebut terbuat dari logam baja.
Power point smoothie presentation minus vidioy11woodse
This document introduces a new smoothie product made from various fruits like pineapple, mango, passion fruit, blackberries, and strawberries. It receives positive reviews from customers who say it is delicious, refreshing, and that the flavors work well together. The document also mentions a limited time offer and is signed off by the creators of the smoothie: Issy, Trini, Tierney, Ella, and Will.
Performance analysis of Adaptive Bit-interleaved Coded Modulation in OFDM usi...IOSR Journals
This document discusses the performance analysis of Adaptive Bit-interleaved Coded Modulation (ABICM) in OFDM using a Zero Padding Scheme (ZPS). It begins with background on OFDM and techniques like ABICM, CP-OFDM, and ZP-OFDM. It then presents the system model for the proposed ABICM-OFDM-ZPS scheme. Next, it analyzes and compares CP-OFDM and ZP-OFDM, noting benefits of ZP like reduced power back-off and wider spectrum. Finally, it discusses how ABICM is applied to the proposed ZP-OFDM system, using channel state information and bit interleaving to improve performance over
Comparative evaluation of bit error rate for different ofdm subcarriers in ra...ijmnct
In the present situation, the expectation about the quality of signals in wireless communication is as high as possible. This quality issue is dependent upon the different communication parameters. One of the most important issues is to reduce the bit error rate (BER) to enhance the performance of the system. This paper provides a comparative analysis on the basis of this bit error rate. I have compared the BER for different number of subcarriers in OFDM system for BPSK modulation scheme. I have taken 6 varieties of data subcarriers to analyze this comparison. Here my target is to reach at the lowest level of BER for BPSK modulation. That is achieved at 2048 number of subcarriers.
Performance evaluation on the basis of bit error rate for different order of ...ijmnct
This document summarizes research evaluating the bit error rate (BER) for different modulation orders and subchannel lengths in an orthogonal frequency division multiplexing (OFDM) system. The research considers QPSK, 8-QAM, and 16-QAM modulation with 256, 512, and 4096 subchannels. Simulation results in MATLAB show that:
1) For 256 subchannels, QPSK modulation has the lowest BER across signal-to-noise ratio (SNR) values from 0-27dB.
2) BER increases with higher modulation orders (from QPSK to 16-QAM) for a given subchannel length.
3) The research provides a comparative analysis of BER performance in an OFDM system
BER Performance of OFDM-QAM over AWGN and RICAIN Channels Using Error Correct...IJERA Editor
In this paper, the performance of OFDM - QAM system by using error correcting codes (Convolutional, Reed Solomon and Interleaving) schemes that are used to encode the data stream in wireless communications using AWGN and RICIAN channels has been reported here. OFDM is presented for wireless communications we curing basic OFDM and affined modulations, as well as techniques to improve the performance of OFDM for wireless communications. Various simulations are performed to detect the best BER performance of each of the QAM system; OFDM-QAM and OFDM-QAM with Error Correction and to use the best outcomes to model the OFDM-QAM, Their effect of improving the total BER can be noticed due to the benefits of OFDM-QAM with correcting codes.
Design Ofdm System And Remove Nonlinear Distortion In OFDM Signal At Transmit...Rupesh Sharma
although OFDM seems to be a solution to keep up with
the demand of increasing data rates, it has some drawbacks.
Sensitivity to high PAPR is the most significant of these
drawbacks. The main objective of this paper was to investigate
and document the effects of PAPR on the performance of OFDM
based digital communications under different channel conditions.
A step-by-step approach was adopted in order to achieve the
objective of this paper. The first step is to provide a basic
background on the principles of OFDM. The reasons for the
PAPR and a theoretical analysis of these effects on OFDM
systems are documented. The OFDM system has a high peak-toaverage
power ratio (PAPR) that can cause unwanted saturation
in the power amplifiers, leading to in-band distortion and out-ofband
radiation. To be able to observe the system behavior, the
simulation results for different channel models are presented in
graphical form. Next, the simulation results obtained in this work
are compared to the simulation results reported in related studies
The document provides an overview of GSM RF interview questions and answers. It covers topics such as the three services offered by GSM (teleservices, bearer services, and supplementary services), spectrum allocation for GSM-900 and DCS-1800, carrier frequencies and separation, ciphering and authentication algorithms, equalization, interleaving, speech coding, channel coding, frequency reuse, cell splitting, interfaces (Um, Abis, A), LAPD and LAPDm, WPS, MA, MAIO, frequency hopping types, DTX, DRX, gross data rate, Erlangs and grade of service, coverage differences between GSM900 and DCS1800, time advance, location area and location update
This document discusses VLSI implementation of orthogonal frequency division multiplexing (OFDM). It provides background on OFDM, explaining that it consists of multiple closely spaced carriers that can achieve high data transmission rates with wide bandwidths. The document outlines the key components of an OFDM transceiver including scrambling, interleaving, constellation mapping, IFFT/FFT processing, and parallel-to-serial conversion. It describes the hardware implementation of these components and advantages of OFDM such as robustness to interference and insensitivity to timing errors.
This document provides an overview of OFDM and the downlink physical layer design in LTE. It discusses why OFDM is necessary for high data rates in LTE, describing how OFDM avoids intersymbol interference through the use of multiple orthogonal subcarriers. It then covers OFDM signal structure and modulation, including the transmitter and receiver designs based on the inverse discrete Fourier transform and discrete Fourier transform. The document also introduces the concept of a guard interval to eliminate intersymbol interference and provides a matrix representation of multicarrier systems using cyclic prefix and DFT/IDFT.
This document summarizes the performance analysis of OFDM and LDPC coded OFDM systems over additive white Gaussian noise (AWGN) and Rayleigh fading channels. It first provides background on OFDM systems, including their block diagram and advantages/disadvantages. It then discusses LDPC coding and how it can reduce the peak-to-average power ratio problem of OFDM. The document compares the bit error rate performance of an uncoded OFDM system versus an LDPC coded OFDM system through simulation over different channel conditions and with varying FFT sizes. Quasi-cyclic LDPC codes with iterative probabilistic decoding are used in the proposed coded OFDM system.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
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This document summarizes a simulation of an IEEE 802.16-2004 OFDM physical layer model in MATLAB. The model includes key parameters like modulation type, bandwidth, SNR, delays, and more. By changing these parameters, their effects on performance metrics like BER are observed. Key findings include higher SNR and larger bandwidth resulting in better performance with more widely spaced constellation points and lower BER. Larger cyclic prefix also improves performance by reducing inter-symbol interference. The document concludes the model is viable for analyzing important WiMAX parameters and their impacts.
Designing and Performance Evaluation of 64 QAM OFDM SystemIOSR Journals
Abstract (11Bold) : — In this report, the performance analysis of 64 QAM-OFDM wireless communication
systems affected by AWGN in terms of Symbol Error Rate and Throughput is addressed. 64 QAM (64 ary
Quadrature Amplitude Modulation) is the one of the effective digital modulation technique as it is more power
efficient for larger values of M(64). The MATLAB script based model of the 64 QAM-OFDM system with
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5 ofdm
1. 5 OFDM
In the last chapter we introduced the multipath propagation and its influence on the
transmission. In sec. 4.4 OFDM is mentioned as one possible solution for mitigating the
influence of delay spread and to increase the robustness of the transmission.
Transmitting digital signals with high data rates using single carrier results in a lot of
difficulties because of the multipath propagation. Due to the short symbol time and the
long channel response time for it, this results in very high requirements for the equaliser.
Dividing the data rate in N subcarriers results in an N times longer symbol duration. In
spite of this improvement there are still some inter-symbol-interferences due to the dif-
ferent runtimes of the signals in the multipath environment. To reduce the inter-symbol-
interference a guard interval is introduced. This guard interval provides some time for the
symbols to raise and decay.
The following paragraph explains some special features of OFDM compared to other multi
carrier systems. One of the most advantages is the abdication of complex filter banks due
to the use of digital signal processing. A characteristic of an OFDM system is the equidis-
tant subchannel order. The distance between different subchannels is chosen in a way that
they do not disturb each other. To obtain this, the carriers of two adjacent subchannels
are orthogonal. This results in the distance of two subchannels
∆f =
1
Ts
. (5.1)
Rectangular pulses are used for calculating the magnitude spectrum. In fig. 5.1 the known
form of the function si(x) = sin(x)
x is shown.
Fig. 5.2 shows the spectrum of an OFDM signal as a composition of frequency shifted
subcarriers. If the frequency shift is exactly an integer multiple of 1/T (refering to 5.1),
the interference of adjacent cariers is equal to zero. There are no inter-carrier-interferences
in spite of an overlapping spectrum.
5.1 Overview about an OFDM system
In this section we are going to shortly discuss the elements which can be found in an
OFDM system. Some elements have been already discussed in previous chapters. In the
following sections each of the new elements will be descriped in detail.
Looking at our simulation chain so far, we notice that we have already discussed the
OFDM system up to the encoder element. First new element we want to introduce is the
interleaver. The interleaver is used to increase the performance gain by changing the bit
order within the bitstream to avoid errors in adjacent bits caused by interferences on adja-
cent subchannels. How an interleaver is working is explained in sec. 5.2. The next element
57
2. 5 OFDM
−5pi −4pi −3pi −2pi −1pi 0 pi 2pi 3pi 4pi 5pi
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
Figure 5.1: Sinc function
−5pi −4pi −3pi −2pi −1pi 0 pi 2pi 3pi 4pi 5pi
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
Figure 5.2: OFDM spectrum as a composition of frequency shifted subcarriers.
58
3. 5 OFDM
Figure 5.3: OFDM-System overview
is a serial to parallel converter (S/P). This converter translates our encoded serial data
stream into N parallel data streams. These N data stream are in the next step mapped
to the different subchannels. The mapping process itself is described in sec. 2.2. After
the mapping we have with the IFFT the second new element. The IFFT is a method in
digital signal processing and converts our subchannel signals from the frequency domain
into a time domain signal. After the conversion into time domain the guard interval is
inserted to eliminate inter-symbol-interference and the signal is send over the channel.
At the receiver the first step is to have syncronisation of the OFDM symbols using cyclic
extension. At this point the additional guard interval is removed. In a second step the
FFT of the signal is calculated. A further explanation about the FFT can be found in
sec. 2.7.2 and in sec. 5.3. With the FFT the signal is converted back from time domain
into frequency domain. As a result we obtain the N different subcarriers. In the parallel
to serial converter the different subchannels are converted back to one single data stream.
The rest of the OFDM system is the same as we had already introduced and discussed in
sec. 3 and 2.
5.2 Interleaving
From the basic principles of OFDM, we know that in the frequency and time selective
transmission environment, the channel does not change significantly in one OFDM sym-
bol or one OFDM sub-carrier, however it changes from sub-carrier to subcarrier in the
frequency domain and symbol to symbol in the time domain. When the channel has a
deep fading, some sub-carriers and some OFDM symbols will suffer from strong noise
interference, which causes a degrading SNR at these positions resulting in excessive burst
errors at the receiver.
To overcome this problem, coding and interleaving are employed in OFDM system. As we
see in the diagram, the block of coding could be done by implementing the convolutional
encoder that we discussed in chapter 3. In the rest of this section, we would focus on the
block of interleaving.
As mentioned above, interleaving is an efficient way to combat burst error, which is
achieved by rearrange the order of the transmit bits. For example, fig. 5.4 shows how
a certain type of interleaver works. This interleaver simply writes the coded bits into the
matrix by rows and then reads them out afterwards by columns. The deinterleaver at the
receiver side performs the reverse procedure, i.e., the bits are written by columns and read
out by rows. The bits in the figure are written row-by-row into a 6×8 matrix and reading
out column-by-column. We define the number of rows B = 6 as the interleaving depth,
59
4. 5 OFDM
(b0, b1, b2, · · · , b7)
b0 b1 . . . b7
b8 b9 . . . b15
b16 b17 . . . b23
b24 b25 . . . b31
b32 b33 . . . b39
b40 b41 . . . b47
Write bits
Read bits
(b0, b8, b16, · · · , b40)
Figure 5.4: Block Interleaver 8 × 6
and the number of columns N = 8 as the interleaving length.
After this kind of interleaving, the fading processes that affect N successive symbols will be
uncorrelated. Therefore, it makes the burst errors appear as ’random errors’, which can be
corrected by coding. Since the interleaver requires memory and deinterleaver causes extra
delay (because deinterleaving takes place only after all the interleaved data is received),
the dimension of the interleaver is a compromise between the delay and the performance
of the system.
Frequency interleaving is usually employed in IEEE802.11a standard, which is to interleave
the information across the sub-carriers prior to transmissions. By implementing frequency
interleaving in OFDM systems, the local deep fading is averaged over the whole bandwidth
of the system. It is implemented for all the data symbols in a single OFDM symbol. The
interleaving pattern shows us how to rearrange the order of the data symbols, which should
be chosen according to the channel and the coding technique used. The following matlab
code describe the interleaving pattern used in HIPERLAN type 2:
cBitsPerBlock = nrDataCarriers*log2(length(map));
bitBlock = 0 : cBitsPerBlock-1;
perm1 = (cBitsPerBlock/16)*rem(bitBlock, 16)+floor(bitBlock/16)+1;
s2 = max([log2(length(map))/2 1]);
perm2 = s2*floor((1/s2)*bitBlock)+rem(bitBlock+cBitsPerBlock-...
floor((16/cBitsPerBlock)*bitBlock), s2)+1;
perm = perm2(perm1);
As shown above, all coded data bits shall be interleaved by a block interleaver with a
block size corresponding to the number of bits in a single OFDM symbol, ’cBitsPerBlock’.
’bitBlock’ represents the index of the coded bit. The interleaver is defined by a two step
permutation. The first ensures that adjacent coded bits are mapped onto nonadjacent
sub-carriers, which is described in the third line. The second permutation ensures that
adjacent coded bits are mapped alternately onto less and more significant bits of the con-
stellation, which is implemented in the 5th and 6th line.
60
5. 5 OFDM
Task:
With the defined interleaving pattern, the frequency interleaver can be imple-
mented as following:
if (~isempty(perm))
for ii = 0 : cBitsPerBlock : length(enc)-cBitsPerBlock
enc(1, perm+ii) = enc(1, ii+1:ii+cBitsPerBlock);
end
end
where enc is the vector of encoded bits. The for-loop rearranges the coded bits
according to the interleaving pattern described in perm. Try to understand how
the code of interleaver works above, and explain it.
Task:
Based on the understanding of the interleaver, try to write a function of dein-
terleaver
Y = deinterleaver(X,cBitsPerBlock,perm) nonumber
where X is the vector of input bits to the deinterleaver, cBitsPerBlock is the
number of bits in a single OFDM symbol and perm represents the interleaving
pattern discussed before.
5.3 Fast Fourier Transform
The complex baseband OFDM signal is the inverse Fourier transform of as many QAM
input symbols as number of subcarriers are utilized. This is done by using the inverse
fast Fourier transform (IFFT), which represents a very quick algorithm to shorten the
calculation of an inverse discrete Fourier transform (IDFT). For best performance, the
number of FFT/IFFT input samples has to be N = 2n with n is a positive integer.
When using the FFT algorithm, it has to be taken in account, that the N output samples
are arranged as follows: index 0 ≤ n ≤ N/2 represents the values for positive frequencies
and index N/2 < n < N represents the values for negative frequencies. Hence, the spec-
trum for positive and negative frequencies has to be flipped (rearranged) before applying
the IFFT (see sec. 2.7.2).
In this lab course, the MATLAB functions fft(), ifft(), fftshift() and ifftshift()
will be utilized to do the transformation between time and frequency domain.
5.4 Cyclic Extension
Multipath propagation introduces delayed copies of the transmit OFDM symbols, which
leads to inter symbol interference (ISI) at the receiver, since the end of the previous symbol
interferes with the beginning of the current symbol. To avoid ISI, a so called guard interval
seperates two adjacent OFDM symbols. Of course, only ISI caused by delays not longer
61
6. 5 OFDM
−.5pi 0 .5pi pi 1.5pi 2pi
−3
−2
−1
0
1
2
3
Figure 5.5: Cyclic extension (red) is copied before the OFDM symbol in time domain
than the guard interval can be avoided by this method.
Since the output of the IFFT (the OFDM symbol) is a periodic function, the guard interval
is a copy of the last part of the OFDM symbol and pasted in front of this symbol. Fig. 5.5
shows the input of the cyclic extension.
5.5 OFDM Modulator/Demodulator
Task
Write an m-file ofdm mod(in, numcarrier, guard) to build up an OFDM
modulator. Calculate the number of OFDM symbols that can be created by
distributing the elements of the QAM symbol stream in to the different car-
riers. Find out the appropriate length of the IFFT, which has to be a power
of two. Rearrange the input stream vector to form a matrix, in which each
column consists of one OFDM symbol. What is the dimension of this matrix.
Preventing FFT inverts the spectrum, cut out the last half of the rows of
the matrix and paste it before the first half. In between these two halfs insert
a block of zeros, thus the number of rows increases to the value of the FFT
length. Now, apply the function ifft() to the matrix, hence the result is
a matrix containing the time representation of the OFDM symbols (column
wise).
Adding the guard interval to each OFDM symbol is simply copying the last
guard rows and pasting them in front of the first row of the matrix.
Task
Write an m-file ofdm demod(in, numcarriers, guard) to build up an OFDM
demodulator. Calculate the necessary FFT length, as it is done in the modu-
lator part. Define the variable symleng for the sum of FFT length and guard
62
7. 5 OFDM
interval, which results in the OFDM symbol length. Calculate the total num-
ber of OFDM symbols in the input stream. Rearrange the input vector in
to a matrix with as many columns as number of OFDM symbols and with a
number of rows corresponding to symleng. Crop the submatrix not belonging
to the guard intervall and apply a FFT. After this, shift the second half of
rows in front of the first half and delete the frequency samples which do not
belong to the used carriers.
5.6 OFDM Chain
In previous sections, we have discussed the elements which are included in a OFDM sys-
tem. In the following, we would start to build a OFDM chain with the functions we
implemented before. In the end of this section, we should have a complete OFDM chain
built in a m function in Matlab, which allows us to do some performance evaluation later.
Follow the descriptions below , which would define the parameters that we use for the
OFDM chain and also would help you to build the signal chain step by step.
Assume we want to transmit 100 bursts of information signal, and each burst contains
24 OFDM symbols. The number of sub-carriers is set to 48, and we use 16QAM mapping
here. The encoder employs a convolutional code of rate equals to 1/2 without any punc-
turing.
Based on the description of the parameters above, try to calculate the number of bits
that need to be generated by the source, and then use the function ’sig gen’ you have
implemented in sect.2.1 to generate the amount of bits we want to transmit.
As shown in fig. 5.3, after the signal source there follows a block of coding, which we use
here is a convolutional code of rate 1/2, and generator polynomials are G1 = 133, G2 =
171. Use the function ’convcode’ that we built before to implement the block of encoding
here.
The interleaving part is described in sect. 5.2, please use the interleaving pattern men-
tioned exactly as in that section.
The bits are mapped to symbols through the block of mapping, which we have also imple-
mented before. Check the function ’mapping’, and make sure 16QAM scheme is adopted
here.
After mapping, there is a IFFT operation which is explained in sect.5.3, and then fol-
lows the operation of inserting the guard interval described in sect.5.4. What we use here
is a guard interval of the length of 16 bits.
The transmission channel employed here is the multipath channel which is described and
implemented in sect.4.1,and at the receiver side comes the FFT operation, demapping
(function ’demapping’),deinterleaving(function ’deinterleaver’), and decoding(function ’con-
decoder’).
63
8. 5 OFDM
5.7 OFDM performance analysis
In this performance chapter you should not only measure some parameters. Furthermore
you are expected to think about some enhancements, that could be made to optimize an
OFDM system.
Task
Run the simulation for different values of the guard interval and analyse the
influence on the BER performance. Try to calculate the throughput of the
system and explain the influence of the guard interval on the achievable max-
imum throughput. Make a comparison to the simulation chain of chapter 4.
Think about some limitations of the presented OFDM system. How can the
OFDM system as we have presented it be improved?
64
9. Bibliography
[1] Proakis, J. G.: Digital Communications. 4th ed. McGraw-Hill, 2001. – ISBN
0–071–18183–0
[2] The MathWorks: Communications Toolbox 3 User’s Guide. http://www.
mathworks.com/access/helpdesk/help/pdf_doc/comm/comm.pdf, March 2007
[3] ETSI EN 300 744 V1.5.1 (Hrsg.): Digital Video Broadcasting (DVB); Framing
structure, channel coding and modulation for digital terrestrial television. ETSI EN
300 744 V1.5.1, November 2004
[4] Kattenbach, Ralph: Charakterisierung zeitvarianter Indoor-Funkkan¨ale anhand
ihrer System- und Korrelationsfunktionen, Universit¨at Kassel, Diss., 1997
[5] Bello, P.: Characterization of Randomly Time-Variant Linear Channels. In: Com-
munications, IEEE Transactions on [legacy, pre - 1988] 11 (1963), Nr. 4, S. 360–393
65