This document provides an overview of orthogonal frequency-division multiplexing (OFDM) communication technology. It introduces OFDM fundamentals such as signal spectrum, system design considerations including cyclic prefix usage and signal parameters. Key receiver functional blocks like channel estimation and its impact on performance are discussed. The document outlines OFDM transmitter operation and issues like carrier frequency error and sampling frequency error on system performance.
Orthogonal Frequency Division Multiplexing, OFDM uses a large number of narrow sub-carriers for multi-carrier transmission to overcome the effect of multi path fading problem. LTE uses OFDM for the downlink, from base station to terminal to transmit the data over many narrow band careers of 180 KHz each instead of spreading one signal over the complete 5MHz career bandwidth. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates.
The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions. Channel equalization is simplified. The low symbol rate makes the use of a guard interval between symbols affordable, making it possible to eliminate inter symbol interference (ISI).
OFDM allows tightly packed carriers to convey information orthogonally and with high bandwidth efficiency
Objectives Description:
Concepts
Basic idea
Introduction to OFDM
Implementation
Advantages and Drawbacks.
FDMA
Orthogonal Frequency Division Multiplexing, OFDM uses a large number of narrow sub-carriers for multi-carrier transmission to overcome the effect of multi path fading problem. LTE uses OFDM for the downlink, from base station to terminal to transmit the data over many narrow band careers of 180 KHz each instead of spreading one signal over the complete 5MHz career bandwidth. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates.
The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions. Channel equalization is simplified. The low symbol rate makes the use of a guard interval between symbols affordable, making it possible to eliminate inter symbol interference (ISI).
OFDM allows tightly packed carriers to convey information orthogonally and with high bandwidth efficiency
Objectives Description:
Concepts
Basic idea
Introduction to OFDM
Implementation
Advantages and Drawbacks.
FDMA
orthogonal frequency division multiplexing(OFDM)
its orthogonal frequency multiplexing topic basicallly in digital signal processing , network signal and system , it also helpful in engineering course either electrical or electronics and communication engineering.
Its exploring the technique for spatially successive interference cancellation and superposition of transmission for upcoming radio communication 5G technology.
This project deals with investigations on development of OFDM based baseband receiver for wireless application. After carrying out initial studies on OFDM based transmitter and receiver, taking into account industrial requirements, an OFDM based baseband receiver has been configured. The block schematic of such a receiver comprises of RF module, ADC fallowed by Digital Down Converter together with the cyclic prefix remover block, serial to parallel converter, FFT module, parallel to serial converter and pilot extractor, the subsequence output is subjected to channel equalization and symbol demapping resulting in the output data that can be processed appropriately.
orthogonal frequency division multiplexing(OFDM)
its orthogonal frequency multiplexing topic basicallly in digital signal processing , network signal and system , it also helpful in engineering course either electrical or electronics and communication engineering.
Its exploring the technique for spatially successive interference cancellation and superposition of transmission for upcoming radio communication 5G technology.
This project deals with investigations on development of OFDM based baseband receiver for wireless application. After carrying out initial studies on OFDM based transmitter and receiver, taking into account industrial requirements, an OFDM based baseband receiver has been configured. The block schematic of such a receiver comprises of RF module, ADC fallowed by Digital Down Converter together with the cyclic prefix remover block, serial to parallel converter, FFT module, parallel to serial converter and pilot extractor, the subsequence output is subjected to channel equalization and symbol demapping resulting in the output data that can be processed appropriately.
Channel Coding and Clipping in OFDM for WiMAX using SDRidescitation
Recent developments in broadband wireless
technology heightened the need for WiMAX which assures
high-speed data services. Mobile WiMAX is grounded on
orthogonal frequency division multiplexing/orthogonal
frequency division multiplexing Access (OFDM/OFDMA)
technology which is an increasing important technique in
LTE systems. This paper describes the OFDM transceiver
implementation using software-defined radio system (SDR).
A SDR is a radio communication system where elements have
been generally implemented in hardware are rather
implemented by software on a personal computer. In this paper,
the software part is realized using GNU Radio and the
hardware part is implemented using USRP N210. OFDM poses
a problem of a Peak to Average Power Ratio (PAPR) or high
crest factor. To stave off this problem either High Power
Amplifiers (HPAs) with large dynamic range or PAPR reduction
techniques are used. The former scheme raises cost of the
system, while the latter induces redundancy or distortion.
This paper presents a novel architecture (which combines
channel coding and clipping) for the PAPR reduction and
analyzes various parameters which effects the performance
of OFDM such as power spectral density, the crest factor and
BER. Channel coding part is framed of three steps
randomization, Forward Error Correction (FEC) and
interleaving. In clipping, certain threshold limits the
amplitude of time domain samples. Without filtering, clipping
causes out-of-band radiation. The paper analyzes the out band
radiation value (at 2.395 GHz) and PAPR reduction with respect
to clipping threshold value. This scheme is preferred because
of its lower complexity and hence would be cheaper to
implement than conventional reduction techniques.
Experimental results prove that the clipping method reduced
PAPR significantly as the number of clip and filtering level is
increased.
Simulation and Implementation for Several PAPR Reduction Techniques in OFDM using USRP with LABVIEW
Using digital signal processing to reduce PAPR in OFDM which used as a modulation technique for many modern communication systems such as wifi, WiMax and LTE. Project has Designed using labVIEW and implemented on real wireless communication system using USRPs.
In recent past the influence of Radar has played a significant part in various fields. Radar sensing is one of
the prime application by which velocity and distance of a moving target can be found out. A joint RadCom
system to serve both radar sensing and wireless communication is proposed which ensures better
performance in terms of spectral efficiency, extended detection range and cost effectiveness. Such systems
demand for a common waveform which is designed in this work that perfectly matches to the system
requirements. OFDM multi carrier technique is chosen to generate a common waveform. Applicability of
multiple antenna technique for direction of arrival estimation is also considered. MIMO-OFDM technique
has gained much interest in the field of communication which improves the signal to noise ratio and lowers
the bit error rate. On the other hand the usage of MIMO reflects in the form of interference between
signals. In order to overcome this effect beamforming technique is used. In addition to theoretical
explanations we have also simulated and discussed the results for the proposed RadCom system using
MATLAB simulation tool.
Old Codex memos on digital timing synchronization. 1985Fuyun Ling
This is a correction of old memoes on modem timing synchronization written in 1985 at Codex Corp., a subsidiary of Motorola. In the memos, many aspects and implementation details are discussed in detail. The products developed based on these memos in mid-80s were probably the earliest commercial Modems with digital timing technology available in the world. Since then this technology are widely used today, it should still have reference value to engineers and researchers working in this area.
A technical description on how to show video over wireless devices. A short description of the challenges such as power consumption, Doppler effect and the many encapsulation protocols
UMTS Long Term Evolution, LTE, is the technology of choice for the majority of network operators worldwide for providing mobile
broadband data and high-speed internet access to their subscriber base. Due to the high commitment LTE is the innovation platform
for the wireless industry for the next decade.
This class will provide the basics of this fascinating technology. After attending this course you will have an understanding of
OFDM-principles including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO),
a fundamental part of LTE, will be explained as well as its impact on the design of device and network architecture. We’ll give a quick
introduction into the evolution of this technology including future upgrades of LTE features like multimedia broadcast, location based
services and increasing bandwidth through carrier aggregation.
The second part of the course will provide an overview including practical examples and exercises on how to test a LTE-capable device
while performing standardized RF measurements such as power, signal quality, spectrum and receiver sensitivity. We’ll address how
to automate these measurements in a simple and cost-effective way. We will introduce application based testing by demonstrating
end-to-end (E2E), throughput and application testing using the Rohde & Schwarz R&S®CMW500 Wideband Radio Communication
Tester. Examples of application tests are voice over LTE, VoLTE or Video over LTE.
EFFECTS OF FILTERS ON THE PERFORMANCE OF DVB-T RECEIVERijwmn
Digital Video Broadcasting-Terrestrial (DVB-T) is an international standard for digital television
services. Orthogonal Frequency Division Multiplexing (OFDM) is the core of this technology. OFDM
based system like DVB-T can handle multipath fading and hence it can minimize Inter Symbol
Interference (ISI). DVB-T has some limitations too namely large dynamic range of the signals and
sensitivity to frequency error. In order to overcome these limitations DVB-T receivers should be optimally
designed. In this paper we address the issues related to optimal DVB-T receiver design. There of several
signal processing units in a DVB-T receiver. A low-pass filter is one of them. In this paper, we consider
some classic filters namely Butterworth, Chebyshev, and elliptic in the DVB-T receiver. The effects of
different filters on the performances of DVB-T receiver have been investigated and compared in this
paper under AWGN channel condition
Blind Channel Shortening for MIMO-OFDM System Using Zero Padding and Eigen De...ijsrd.com
This paper deals with multiple-input multiple-output (MIMO) broadband wireless communication systems, employing orthogonal frequency-division multiplexing (OFDM). In order to exploit the benefits of OFDM in highly frequency-selective channels, without any significant increase in receiver complexity, a channel shortening prefilter is inserted at the receiver. The main aim of inserting channel shorteners is to shorten the channel so that the main energy of the composite channel is concentrated within a duration smaller than the guard interval inserted while transmission. Thus by including channel shortening equalizers at the receiver the inter symbol interference or the inter block interference can be suppressed. The new approach proposed in this thesis is zero padding approach with Eigen decomposition approach. The advantages of the proposed approaches include immunity to delay spread, resistance to frequency selective fading and simple equalization. This shortening design is a blind one, i.e., a priori knowledge of the MIMO channel impulse response to be shortened is not required, and can be carried out in closed-form.
An adaptive channel estimation scheme based on redundancy minimization for fi...TELKOMNIKA JOURNAL
Filtered orthogonal frequency division multiplexing (F-OFDM), a technology which is being considered as a promising platform for beyond 4G era is expected to help deliver the new features at millimeter wave in the new 5th generation of cellular communication. Some of its key features notably better spectral utilization, enhanced throughput and immunity to interference can be enabling for the new cellular standards. These features of filtered OFDM comes with strict requirements of filter design, guard tone managements, and efficient channel state information harness. This paper is intended to propose an intuitive channel estimation scheme which will allow efficient acquisition of channel state information (CSI) through exploiting the redundant steps of the conventional pilot training-based algorithms and by also using an adaptive weight to expedite the minimization of the error between the estimated values and the actual values. Various simulations will follow to demonstrate the superiority of the scheme over traditional pilot-based algorithms and thus prove its utility in the current 5G cellular era.
The new 5G unified air interface is being designed to not only vastly enhance mobile broadband performance and efficiency, but also scale to connect the massive Internet of Things and enable new types of services such as mission critical control that require ultra-low latency and new levels of reliability and security. The new design will unify diverse spectrum types and bands, scale from macro deployments to local hotspots and efficiently multiplex the envisioned 5G services across an extreme variation of requirements.
For more information on 5G technologies, use cases and timelines, please visit us at www.qualcomm.com/5G.
Initial acquisition in digital communication systems by Fuyun Ling, v1.2Fuyun Ling
This presentation describes the initial acquisition process in digital communication systems, their optimality, and useful rule of thumb formulas, e.g., the non-coherent combining gain. Example the initial acquisitions in CDMA2000, WCDMA and LTE are also given.
New book information added
This is the third part of the mini-series of synchronization in the Topics in Digital Communication Presentations.
Timing synchronization is another key component in modem design and implementation. However, this subject, especially its practical aspects, were not covered in details in text books. The materials covered in this presentation are not really new, but discussed in the literature published over past forty years. I hope that putting them in a single slide deck can help people who want to learn more on this subject.
New book information is added
Fuyun Ling
During past a few months, I spent some time on the subject of "In Band Full-Duplex" wireless communications, because it is related to echo cancellation that I worked on many years ago. I put together a presentation on this subject for share with people have same interest.
It should be noted that what shown in the presentation are based on my experience and reflect my understanding and opinions. As usual, my opinions are in general conservative and may or may not be totally correct. Please let me know if you have any comments. Thanks.
This is the third part of the mini-series of synchronization in the Topics in Digital Communication Presentations.
Timing synchronization is another key component in modem design and implementation. However, this subject, especially its practical aspects, were not covered in details in text books. The materials covered in this presentation are not really new, but discussed in the literature published over past forty years. I hope that putting them in a single slide deck can help people who want to learn more on this subject.
Fuyun Ling
Initial acquisition in digital communication systemsFuyun Ling
This presentation describes the initial acquisition process in digital communication systems, their optimality, and useful rule of thumb formulas, e.g., the non-coherent combining gain. Example the initial acquisitions in CDMA2000, WCDMA and LTE are also given.