...Performance Evaluation of OFDM System for Different Channel and Different Modulation Techniques Thesis Report Department of Electronic and Telecommunication Engineering (ETE) Submitted By Foysal Bin Wadud (T-093011) Gazi Shamsul Arefeen Shams (T-093016) Supervised By Engr. Mohammad Jashim Uddin Contact Information: Foysal Bin Wadud (Mamun), Dept. of ETE, International Islamic University Chittagong, Metric No.: T093011, Email: mamunmoon19@yahoo.com Contact No.: +8801717934676 Gazi Shamsul Arefeen (Shams) Dept. of ETE, International Islamic University Chittagong, Metric No.: T093016, Email: shams.ete@gmail.com Contact No.: +8801676848247 Contact Information of Supervisor: Md. Jashim Uddin Dept. Of ETE, International Islamic University Chittagong. Contact No. +8801716-823959 Email: jashimcuet@yahoo.com Abstract The demand for high-speed mobile wireless communications is rapidly growing. Orthogonal Frequency Division Multiplexing (OFDM) technology promises to be a key technique for achieving the high data capacity and spectral efficiency requirements for wireless communication systems in the near future. An Orthogonal Frequency Division Multiplexing (OFDM) scheme offers high spectral efficiency and better resistance to fading environments. In OFDM the data is modulated using multiple numbers of sub-carriers that are orthogonal to each other because of which the problems associated with other modulation schemes such as Inter Symbol Interference (ISI) and Inter Carrier Interference...
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...Review Questions for Test-2 (Partial List) Part-A End-of-Chapter-4 Questions (match questions, overlook number mismatch) 1. How does analog data differ from digital data? Computers produce digital data that are binary, either on or off. In contrast, telephones produce analog data whose electrical signals are shaped like the sound waves they transfer. Analog data are signals that vary continuously within a range of values (e.g., temperature is analog). 1. Clearly explain the differences between analog data, analog transmission, digital data, and digital transmission. Data can be transmitted through a circuit in the same form they are produced. Most computers, for example, transmit their data through digital circuits to printers and other attached devices. Likewise, analog voice data can be transmitted through telephone networks in analog form. In general, networks designed primarily to transmit digital computer data tend to use digital transmission, and networks designed primarily to transmit analog voice data tend to use analog transmission (at least for some parts of the transmission). 4. How does baseband differ from broadband? Baseband is the digital transmission of binary electrical pulses. Broadband is the analog waveform used for transmission. 4. What is coding? Coding is the representation of one set of symbols by another set of symbols. In data communications, this coding is a specific arrangement of binary 0s and 1s used to represent...
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...followed by the modulation and then reception at the receiver and making sure that there is no factor of signal degradation and noise. “The binary signal is made up of two symbols namely binary digits or bits 1 and 0. If there is no influence of noise and distortion during transmission, the binary information will be the same. The change in the signal is being measure at the receiver. Encoding is needless if the information to be transferred has already been converted in binary form just like in data communications. In contrary, voice communication through telephone is not in binary form. These are analog signals that vary in range of values and therefore must be converted to digital form before it is being used in digital communications system.” (T. T. (2011). Digital signal to analog signal conversions involve the use of DAC (Digital-to-Analog Converters). DAC accepts the discrete binary values and converts them into continuously-varying values of analog signal. This conversion may affect the fidelity of the signal if the process was not properly monitored. Analog telephone lines, most commonly called POTS lines, uses separate lines (e.g. standard phone and fax lines, alarm lines, etc.) from the digital equipment lines (e.g. PBX). The use of modem for computer’s connection to the internet is one of the best examples of conversion from analog to digital signals using standard phone line. Advantages and Disadvantages of Common Modulation Techniques Amplitude...
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...different languages people can speak all over the world. Without proper translation and understanding, the conversation is pointless; this analogy is similar for analog and digital transmissions. Beginning with an analog signal, which is a continuous variable along amplitude and frequency. Analog circuits need to have a defined frequency band in which it operates. Different modulation schemes can vary the speed in which they operate, the quality of wire they require, the immunity to noise, and their overall complexity. The variety of modulation schemes in existence can be a disadvantage as this means many incompatibilities can exist within a single application. Such modulations include: * Amplitude modulation (AM) - modem relies on amplitude and associates high amplitude/zeros with low amplitude. Amplitude modulation can be demodulated using a circuit consisting of very few components but lacks a bit of quality, much like with AM radio frequencies. * Frequency modulation (FM) - modem altars the frequency value and decodes original bit patterns based on the frequency of the received signal. Frequency modulation has the advantage that, as amplitude variations do not carry any information on the signal, it can be...
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...Chapter 1 Basic Networking Chapter 1 Basic Networking: Data communication is the transfer of data from one device to another via some form of transmission medium. A data communications system must transmit data to the correct destination in an accurate and timely manner. The five components that make up a data communications system are the message, sender, receiver, medium, and protocol. Text, numbers, images, audio, and video are different forms of information. Data flow between two devices can occur in one of three ways: simplex, halfduplex, or full-duplex. A network is a set of communication devices connected by media links. In a point-to-point connection, two and only two devices are connected by a dedicated link. In a multipoint connection, three or more devices share a link. Topology refers to the physical or logical arrangement of a network. Devices may be arranged in a mesh, star, bus, or ring topology. A network can be categorized as a local area network (LAN), a metropolitan-area network (MAN), or a wide area network (WAN). A LAN is a data communication system within a building, plant, or campus, or between nearby buildings. A MAN is a data communication system covering an area the size of a town or city. A WAN is a data communication system spanning states, countries, or the whole world. An internet is a network of networks. The Internet is a collection of many separate networks. TCP/IP is the protocol suite for the Internet...
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...Analog and Digital Comparison Paper Current technology utilizes many different types of transmission cable such as fiber optics, coaxial cable, and twisted pair copper wire. These different types of cables use different communications techniques that maximize their efficiency. For instance, fiber optics can carry digital signals over long distances without amplification or repeaters required. Copper wire, on the other hand, carrying analog signals requiring amplification and noise corrections along the way in much shorter intervals. The result is there is a mix of transmission lines that require special software and equipment such as codecs and modems to convert and move data from one point to another. Codecs and Modems The most common form of analog to digital conversions uses multiplex devices and coder-decoder devices otherwise known as codecs. These programs receive analog signals from sine waves such as audio communications and code them as digital signals. These signals then travel to other locations with codec or modem devices that decode or decompress the data back to analog signals. Digital devices use modems or combinations of codecs and modems to modulate the data signals to analog signals to travel to other modems for demodulation back to digital data. The codec is “software that is used to compress or decompress a digital media file, such as a song or video” (Microsoft, 2014). This process is the same in telecommunications systems, which consist of the encoder...
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...Analog and Digital Comparison Paper Current technology utilizes many different types of transmission cable such as fiber optics, coaxial cable, and twisted pair copper wire. These different types of cables use different communications techniques that maximize their efficiency. For instance, fiber optics can carry digital signals over long distances without amplification or repeaters required. Copper wire, on the other hand, carrying analog signals requiring amplification and noise corrections along the way in much shorter intervals. The result is there is a mix of transmission lines that require special software and equipment such as codecs and modems to convert and move data from one point to another. Codecs and Modems The most common form of analog to digital conversions uses multiplex devices and coder-decoder devices otherwise known as codecs. These programs receive analog signals from sine waves such as audio communications and code them as digital signals. These signals then travel to other locations with codec or modem devices that decode or decompress the data back to analog signals. Digital devices use modems or combinations of codecs and modems to modulate the data signals to analog signals to travel to other modems for demodulation back to digital data. The codec is “software that is used to compress or decompress a digital media file, such as a song or video” (Microsoft, 2014). This process is the same in telecommunications systems, which consist of the encoder...
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...different times due to reflection. Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 6. Which of the following is an electromagnetic wave? a. | light | c. | radio | b. | heat | d. | All of the above | ____ 7. Which of the following units is used to measure frequency? a. | decibel | c. | hertz | b. | volt | d. | byte | ____ 8. The term ____ describes the rate of electrical flow. a. | voltage | c. | resistance | b. | current | d. | electrical power | ____ 9. ____ modulation changes the number of waves representing one cycle. a. | Amplitude | c. | Frequency | b. | Phase shift | d. | Phase | ____ 10. Which type of modulation changes the starting point of the cycle to represent a change from a 1 bit to a 0 bit and vice versa? a. | AM | c. | DM | b. | FM | d. | PM | ____ 11. Which binary modulation technique is similar to frequency modulation? a. | amplitude shift keying | c. | phase shift keying | b. | frequency shift keying | d. | All of the above | ____ 12. Power of an electromagnetic signal such as one used in WLANs is measured by which unit? a. | millivolts | c. | milliohms | b. | milliamps | d. | milliwatts | ____ 13. When an RF signal moves from one medium to another of a different...
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...1 CHAPTER-1 INTRODUCTION Seminar Report For Electronics (ECE) / Electrical (EEE) / Instrumentation (EI or AE&I) Engineering or Sciences 1INTRODUCTION Are you tired of slow modem connections? Cellonics Incorporated has developed new technology that may end this and other communications problems forever. The new modulation and demodulation technology is called Cellonics. In general, this technology will allow for modem speeds that are 1,000 times faster than our present modems. The development is based on the way biological cells communicate with each other and nonlinear dynamical systems (NDS). Major telcos, which are telecommunications companies, will benefit from the incredible speed, simplicity, and robustness of this new technology, as well as individual users. In current technology, the ASCII uses a combination of ones and zeros to display a single letter of the alphabet (Cellonics, 2001). Then the data is sent over radio frequency cycle to its destination where it is then decoded. The original technology also utilizes carrier signals as a reference which uses hundreds of wave cycles before a decoder can decide on the bit value (Legard, 2001), whether the bit is a one or a zero, in order to translate that into a single character. The Cellonics technology came about after studying biological cell behaviour. The study showed that human cells respond to stimuli and generate waveforms that consist of a continuous line of pulses separated by periods of silence. The...
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...• What are the various modulation techniques? Begin your explanation with frequency-shift keying and move to multilevel QAM. During this week’s readings I have found 4 different modulation techniques: Amplitude modulations, frequency modulation, phase modulation, and quadrature amplitude modulation. While these have different modulation schemes that branch out, these are the primary used modulations I have found. Amplitude modulation is when different amplitudes are used to represent the digital bitstream in analog format. Modems rely on amplitude modulation to determine the high amplitude that is represented by ones and low amplitudes that are represented by zeros. They also rely on amplitude modulation to determine the difference in the amplitudes so the receiving device can put out the message in the correct way. Frequency modulation is also known as FSK, or frequency-shift key. FSK’s uses two different frequencies to distinguish between a mark digital 1 and a space digital 0 when transmitting on an analog line. It is used on modems that operate at 1,200bps or slower (Goleniewski, 2007). Phase modulation modifies a sine wave, also known as a carrier, to allow it to carry information. The phase of the sine wave is changed to fit the type of information that is being transferred. Phase modulation can be paired with carrierless amplitude for ADSL, or Asymmetrical DSL. Last Quadrature Amplitude Modulation is a “single-carrier scheme that modulates...
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...DeVry University College of Engineering and Information Science Pomona, California MODULATION IN THE BIOMEDICAL FIELD By JeanPaul Gagner Aceflyte99@gmail.com Submitted in Partial Fulfillment of the Course Requirements for Communications Systems w/Lab ECET-310 Professor: Mohammad Muqri April 20, 2014 Since the 1950s, wireless medical implant devices have become increasingly useful in monitoring, diagnosing, and adapting a person’s physiological inability to perform mundane tasks. While there are many advantages to these devices, the engineering behind them reveals many issues with the communicating ability of these wireless implants. With patient safety and comfort in mind, overall size and power requirements became an issue. Since the most sensitive parts of the implant are inside the patient’s body, surgery for repair and maintenance can present a risk to the patient and device. Cost is always an issue as well, so creating the most efficient, reliable, and cost-effective device is of the utmost priority. Possibly the most concerning aspect of the wireless design process is conserving power and reducing interference. Since most internal devices are self-controlled, they can limit their own operation according to the needs of the patient, such as a pacemaker. The power to operate these types of devices is supplied by external battery, or created by radio-frequency signals running through inductive coupling links. This creates...
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...prime example of a telecommunication that uses this form of conversion is a telephone modem. Voice communications vary in range and are not in binary form, so these analog signals must be translated into digital signals. Digital to analog conversions or DAC is the conversion of binary code to analog signal. In order words, signals having few defined levels or states are converted into signals having a theoretically infinite number of states (Rouse, 2005). Going from digital to analog can sometimes be tricky and even cause the quality of the signal to be compromised. An example of digital to analog conversion would be the use of Internet via a modem; the modem converts computer signals (digital) using standard phone lines. Amplitude Modulation &...
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...place to another is either audio or video. This information signal is then transformed into those signals which can be transmitted via different channels. For the analog format, the data is transformed into electrical pulses with varying amplitude while for the digital format; the data is transformed into binary format representing two amplitudes. We have various such equipment like analog or digital phones, fax machines, modems, clocks, watches etc. Analog technology is the older one and has been used for decades. It is cheap too but the problem with analog signals is that there is a limitation on the size of the data that can be transmitted at any given point of time. With the advent of digital technology many improvements and new techniques have been introduced. Now days almost every appliance or equipment is based on digital technology. In this, the transmitter translate the data into binary form and the receiver re assemble and produces the original information signal. Digital signal as compared to analog gives us more options as it can be easily computed and manipulated by software. Also digital signals are frequently used in telecommunication. Instead of having various advantages over analog signal, digital signal lag behind in quality. Since in digital devices there is translating and reassembling of data because of this reason...
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...Analog and Digital Comparison Technologies for analog-to-digital and digital-to-analog conversions There is no actual all analog or all digital telecommunications going on technologically today (Goleniewsk & Wilson Jarrett, 2007, Chapter Chapter 1, Analog Versus Digital Transmission). One day, developers hope to make the network 100% digital. Connecting to the internet or just making a call to your mother two states over is a mixture of both when it comes to communicating from one terminal to the next. That being said, it takes codecs and modems for a successful conversion to occur. Say you are calling another state from a land line. This call will start out analog at your telephone and then must be converted to digital. When you pick your phone up, it connects to a codec. Your voice can range from 100Hz to 10,000Hz depending on many factors. The average Hz a phone company will allot is 4,000 which works for virtually all people. Codec is short for coder-decoder and it works by minimizing the amount of bits per second that will carry the voice to the multiplexer. In the case of a cellular network, the data will have to be compressed even further so that the most efficient transmission can occur. The codec will then transfer the data to a multiplexer. This particular multiplexer is a TDM (time division multiplexer). This will allow for one channel to be open at a time. This does make sense since it would not be good to take over a phone line once it is being...
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...Chapter 4: Digital Transmission (Line coding, Block coding, Scrambling) Digital to digital conversion (Line Coding) Converting a sequence of data bits (text, numeric, audio, or video) into a digital signal, at the sender, then recovering the original bit sequence from the signal, at the destination data rate bit rate(N) b/s, signal rate(S) baud ratechange/s (Hz) Let r bit/change, Nmax = S * r * 1/c where c is and usually assumed ½ For the average calculations of S&N The goal is to increase the data rate (information flow) while decreasing band rate (better utilization of channel BW, cheaper links) Factors to consider in digital signaling: Long strings of 0‘s or 1‘s causes a drift of the obtained baseline, hence ―baseline wandering‖ that leads to incorrect bit decoding. 1) Baseline wandering: The receiver averages the signal power (Baseline), and uses it to decode the received signal bit value. 2) DC components: Constant level for long period of time creates very low frequency components in the frequency spectrum, that might not pass through some medium (e.g., TP of 200Hz 3000Hz). Hence, we need to remove the DC from the Digital Signal . 3) Self-Synchronization: To match the sender and receiver clocks, hence match the bit intervals at both ends for correct decoding. Transitions in the digital signal act as self-synch altering the receiver to the start, mid, or end of the bit, resetting its clock in case it is out of synch. 4) Built in error detection: It is good to...
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