Subcarrier allocation technique plays an important role in the ofdma system, because it can enhance subcarrier utilization ratio, improve network throughput and guarantee users qos. Research article relay selection and subcarrierpair based energyefficient resource allocation for multirelay cooperative ofdma networks wanminghao, 1 shouyiyang, 1 andwanlianghao 2 school of information engineering, zhengzhou university, zhengzhou, china. Joint network coding and subcarrier assignment in ofdmabased. The secure subcarrier assignment algorithm is designed to ensure that.
Using a large number of parallel narrowband subcarriers instead of a single wideband carrier to transport information ladvantages. Subcarrier spreading for ici mitigation in ofdmofdma systems. Optimization of subcarrier and power allocation in uplink. For this reason, a hybrid systemlink level simulator has been developed executing independent monte carlo. Mar 18, 2019 allow ofdma to extend to small subchannels.
In this paper, subcarrier allocation schemes for cellular orthogonal frequency division multiple access ofdma systems with adaptive modulation and coding amc is considered. The orthogonal frequency division multiple access ofdma based. The subcarrier indices are numbered from 1 to cin fft, where n fft is the number of fft points. The probability density function pdf of user ks channel gain phk is given by consider a k user system, where the subcarrier of interest experiences i. Orthogonal frequency division multiple access ofdma has evolved as a leading technology in future broadband wireless networks, such as 3gpp longterm evolution lte and ieee 802. This paper provides a comprehensive survey of the latest results in the field of synchronization for ofdma. Phase noise and subcarrier spacing welcome to mentor. Rather than transmit a highrate stream of data with a single carrier, ofdm. A notion of revenue maximization is used to determine the optimal ofdma subcarrier allocation to different users based on their required qos.
Spectrum of multiple ofdm subcarriers of constant amplitude. Until this time, we needed a large number of subcarrier oscillators to perform parallel modulations and demodulations. Because of this relationship, the resulting sinc frequency response curves from each subcarrier create signal nulls in the adjacent subcarrier frequencies thus preventing intercarrier interference ici. An 800subcarrier system with 64qam mapped to each subcarrier can transmit 800 x 8 6400 bits per symbol. Pdf a new modulation technique, named as orthogonal frequency division multiplexing ofdm with subcarrier number modulation snm. The goal of the study presented in this paper is to investigate the performance of a new subcarrier allocation strategy for orthogonal frequency division multiple access ofdma multicellular networks which employ multiple input multiple output mimo architecture. Ofdma physical layer basics mobile wimax physical layer. A subcarrier and bit allocation algorithm for mobile ofdma systems. Orthogonal frequencydivision multiple access wikipedia. One feature ofdma seems much more significant than the others.
This article describes ofdma basics, ofdma frame structure,ofdma symbol,ofdma physical layer as per ieee 802. A subcarrier and bit allocation algorithm for mobile ofdma. Moreover, power and subcarrier allocation were treated as two separate problems. In this paper the lte in general and scfdma will be discuss in details and its performance will be study under two types of subcarrier mapping which are localized and distributed. Pdf physical layer aware mac schemes for dynamic subcarrier. In the case of such channel variations, for example due to very high doppler spread, the. Ofdma incorporates elements of time division multiple access tdma so that the subcarriers can be allocated dynamically among the different users of the channel. One of the key features driving this connectivity improvement is orthogonal frequencydivision multiple access ofdma. Jammingresilient subcarrier assignment for ofdma based space. Interference from sub carrier to pus bands is integration of this subcarrier spectrum density across the. Introduction to ofdm lbasic idea using a large number of parallel narrowband subcarriers instead of a single wideband carrier to transport information ladvantages very easy and efficient in dealing with multipath robust again narrowband interference ldisadvantages sensitive to frequency offset and phase noise. Multiple access is achieved in ofdma by assigning subsets of subcarriers to individual users. The intent of this application note is to provide a brief introduction to ofdm and ofdma, with an eye toward the special considerations and environments for ad applications.
The orthogonal frequency division multiple access ofdma based systems are being adopted for use in different flavors of bcw systems 1. An introduction to orthogonal frequency division multiplex. Orthogonal frequencydivision multiple access ofdma is a multiuser version of the popular orthogonal frequencydivision multiplexing ofdm digital modulation scheme. Pdf ofdm with subcarrier number modulation researchgate. The reason for the large outofband emission of a basic. Keysight technologies ofdma introduction and overview for. Subcarrier power allocation scheme for ofdma networks. Orthogonal frequency division multiplexing ofdm modulation a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. Paper synchronization techniques for orthogonal frequency division multiple access ofdma. Ofdm is a form of frequency division multiplexing fdd, which typically requires guard bands between carriers and specialized hardware with. Joint network coding and subcarrier assignment in ofdma.
The main difference between an ofdm and an ofdma orthogonal frequency division multiple access system if the fact that in the ofdm the user are allocated on the time domain only while using an ofdma. Show the subcarrier mapping of the ofdm symbols created by. Jammingresilient subcarrier assignment for ofdma based. Us78892b2 ofdmofdma timing synchronization using non. This article describes ofdma basics, ofdma frame structure, ofdma symbol, ofdma physical layer as per ieee 802.
Ofdma introduction and overview for aerospace and defense. Understanding the complexities of ofdm and ofdma can be challenging, particularly if one has not previously worked with commercial wireless standards. In this study, the goal is to evaluate the performance of a new subcarrier allocation strategy for mimo ofdma networks that maximizes the desired mss signal and at the same time minimizes the interference caused to the rest of the network. Enhanced subcarrier index modulation sim ofdm dobroslav tsonev, sinan sinanovic and harald haas institute fordigital communications,joint research institute forsignal and image processing, the university of edinburgh,eh9 3jl, edinburgh,uk email. Research article relay selection and subcarrierpair based. Ofdm and ofdma subcarrier allocation with standard ofdm the subcarrier allocations are fixed for each user and performance can suffer from narrowband fading and interference. Frequency division multiplexing ofdm is a spectrally efficient digital. Orthogonal frequencydivision multiplexing wikipedia. Adaptive subcarrier and bit allocation for downlink ofdma system.
I know lte doesnt use the dc subcarrier for ofdmofdma modulation for the downlink, but no author gives a detailed explanation to this stuff. For this reason, a hybrid systemlink level simulator has been developed executing independent monte carlo mc simulations in. Optimal ofdma subcarrier, rate, and power allocation for ergodic rates maximization with imperfect channel knowledge ian c. In this paper, a medium access control mac framework tailored for orthogonal frequencydivision multiple access passive optical networks ofdmapons is defined which allows exploiting both the subcarrier and time domains in a dynamic and flexible. To reduce the overhead, the feedback information only contains the best modulation type that a subcarrier can achieve given the current snr.
Orthogonal frequency division modulation 2 ofdm 6 a adjacent subchannels interfere b guard bands protect leakage from adjacent frequencies figure 9. Subcarriers in ofdm it is easy to see that these subcarriers are orthogonal, i. I know lte doesnt use the dc subcarrier for ofdm ofdma modulation for the downlink, but no author gives a detailed explanation to this stuff. Oct 24, 2014 the probability density function pdf of user ks channel gain phk is given by consider a k user system, where the subcarrier of interest experiences i.
Ofdm has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, dsl internet access, wireless networks, power line. Network coding aware dynamic subcarrier assignment in. In this paper, a medium access control mac framework tailored for orthogonal frequencydivision multiple access passive optical networks ofdma pons is defined which allows exploiting both the subcarrier and time domains in a dynamic and flexible. Multiplexing method of sharing a bandwidth with other independent data channels. Optimization of subcarrier and power allocation in uplink ofdma systems m. Ofdma physical layer basics mobile wimax physical layer as. The objective is to maximize the resource utilization in a network, while a required quality of service qos per user is satis. Scheduling algorithms for quality of service aware ofdma. Title corrections in ofdma subcarrier allocations date submitted 20041104 sources myungkwang byun, yunjik jang, jiho jang, jeongheon kim, seungjoo maeng, jaeho jeon samsung electronics co. This multiplexing digital modulation scheme introduces newfound permeability into highly dense wifi traffic scenarios. Subcarrier power allocation scheme for ofdma networks isbn.
Embodiments use deconvolution to construct the channel impulse response associated with a received signal. This document has been prepared to assist ieee 802. A new subcarrier allocation strategy for mimoofdma. In telecommunications, orthogonal frequencydivision multiplexing ofdm is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. Pdf we study the problem of finding an optimal subcarrier and power allocation strategy for downlink communication to multiple users in an ofdm based. One can see from the figure that eventhough the subcarrier signals are overlapping in the time and frequency domains, there is no mutual interference when the sampling is done at. A controller located in the base station selects the appropriate subchannel allocation, the modulation and coding scheme mcs and the transmit. Evans the university of texas at austin, austin, texas 78712. Subcarrierpower allocation scheme for ofdma networks how immature to spew people here, at this early hour, once all the heretofore billboards above coat reacted bobbed.
Since the subcarrier resource can be allocated in both time and frequency domains, the performance of a subcarrier allocation scheme largely depends on the. Ofdma and mimo notes 1 ee442 spring semester lecture 14 orthogonal frequency division multiplexing ofdm is a digital multicarrier modulation technique extending the concept of single subcarrier modulation by using multiple subcarriers over the channel. Myung qualcommflarion technologies 500 somerset corporate blvd. Ofdm is a combination of modulation and multiplexing.
Subcarrierpower allocation scheme for ofdma networks isbn. A major breakthrough in the history of ofdm came in 1971 when weinstein and. Box 105 416, maetan3dong, yeongtonggu, suwoncity, gyeonggido, korea 442600 mk. In the distributed subcarrier mapping mode, dft outputs of the input data are allocated over the entire bandwidth with zeros occupying the unused subcarriers, whereas consecutive subcarriers are occupied by the dft outputs of the input data in the localized subcarrier mapping mode. Robust again narrowband interference ldisadvantages. Jun 01, 2015 because of this relationship, the resulting sinc frequency response curves from each subcarrier create signal nulls in the adjacent subcarrier frequencies thus preventing intercarrier interference ici. Ofdma physical layer model we consider an ofdma system with nf subcarriers over a frequency selective fading channel with l independent multipaths. A requirement for the ofdm subcarrier orthogonality 3. Around the same time, saltzberg2 performed an analysis of the performance of the ofdm system.
Introduction as a key component of the stateoftheart ieee 802. The transmitter of the assigned bs exploits the number of users, k, to divide the ofdma frame into, nsc, subchannels. Comparative study in performance for subcarrier mapping in. High spectral efficiency by spacing many subcarriers very closely and arranging them to be orthogonal, allowing each subcarrier to be independently modulated.
Network coding aware dynamic subcarrier assignment in ofdma. Introduction to orthogonal frequency division multiplexing ofdm cyclic prefix cp and circul. Relay selection and subcarrier pair based energyefficient resource allocation for multirelay cooperative ofdma networks wanminghao, 1 shouyiyang, 1 andwanlianghao 2 school of information engineering, zhengzhou university, zhengzhou, china college of navigation and aerospace engineering, information engineering university, zhengzhou, china. Is a composite of all ofdm subcarrier symbols and time. Paper synchronization techniques for orthogonal frequency. Rayleigh fading, that is, users channel gain is independent of the others, and is denoted by hk. A controller located in the base station selects the appropriate subchannel allocation, the modulation and. Subcarrier allocation in multihop orthogonal frequency. In this study, the goal is to evaluate the performance of a new subcarrier allocation strategy for mimoofdma networks that maximizes the desired mss signal and at the same time minimizes the interference caused to the rest of the network. We will refer to the localized subcarrier mapping mode of scfdma. The main difference between an ofdm and an ofdma orthogonal frequency division multiple access system if the fact that in the ofdm the user are allocated on the time domain only while using an ofdma system the user would be allocated by both time and frequency. Ofdm introduction ee225c introduction to ofdm lbasic idea using a large number of parallel narrowband subcarriers instead of a single wideband carrier to transport information ladvantages very easy and efficient in dealing with multipath robust again narrowband interference ldisadvantages sensitive to frequency offset and phase.
Ofdm is readily compatible with these technologies. However, we will focus on subcarrier allocation and bit loading for ofdma. Chapter 7 ofdm communications over timevarying channels. We will go through mobile wimax ofdma physical layer. Systems and methods which are adapted determine timing with respect to an orthogonal frequency division ofd channel, such as may be used with respect to an ofdm or ofdma systems through reliably identifying timing of a first arriving signal path. This allows simultaneous lowdatarate transmission from several users. Ofdm with subcarrier number modulation article pdf available in ieee wireless communication letters pp99. The other is the subcarrier index modulation sim, also known as orthogonal frequency division multiplexing ofdm im, wherein the frequency subcarrier index of the transmitted symbol carries. Orthogonal frequency division multiple access ofdma. Fullfilling subcarrier power allocation in ofdmabased. Due to the use of orthogonal equispaced subcarriers, ofdm systems with lti frequency.
Each subchannel requires at least one usually two pilot subcarriers, and with a 2 mhz minimum subchannel size, a smaller subcarrier spacing loses a much smaller percentage of the overall bandwidth to pilots. Pdf subcarrier allocation and power control for ofdma. It also explains ofdma tdd frame which consists of pusc, fusc and amc zones in the downlink and puscamc zones in the uplink. With dsp techniques fft and ifft, subcarrier spacing can be reduced to theoretical minimum, i.
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