We have two options, one hire a big truck or a bunch of smaller ones. The multiuser capability is achieved by assigning each user a subset of ofdm subcarriers see ofdm. Performance evaluation of lte physical layer using scfdma. Frequencydivision multiple access fdma is a channel access method used in some multipleaccess protocols. Ofdma as 3gpp longterm evolution uplink friday december 4, 2009 ee359 project nima soltani 1. Rf engineers of the industry are now using methods to remedy these problems. Ofdma channel access method code division multiple access.
It is not possible to use ofdma on the uplink since, as told before, it presents a high peaktoaverage power ratio. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Introduction in order to transition from todays 3rd generation 3g communications systems to meet the needs of 4th. Frequency division multiple access ofdma in downlink dl and single carrier frequency division multiple access sc fdma for uplink ul, as shown in figure 3. Fundamentals of communications access technologies. Multisubframe modulation processing results in a waveform that does not have. Aug 11, 2016 multiple access fdma tdma cdmaofdma in 4g lte multiplexing is the process of combining multiple signals and transmitting them over a common channel and it. Comparing the advantages and disadvantages of ofdm, ofdma and cdma 4glte technology uses ofdma. Mar, 2014 frequency division multiple access fdma 1. Orthogonal frequency division multiple access ofdma. Wavelength division multiple access wdma is a related to fdma. Fdma versus tdma versus cdmadifference between fdma,tdma,cdma.
So, the mutual interference is in a nicefree way, reduced by. An analysis of ofdma, precoded ofdma and scfdma for the uplink in cellular systems. Many of the problems experienced in tdma due to different propagation delays are eliminated in fdma. Handling high papr places demands on the power amplifier as it requires a larger linear range to maintain distortion free transmission. Multiplexing and demultiplexing it was observed that majority of the device which is used for personage data. Analysis of scfdma and ofdma performance over fading channels.
Both ofdm and ofdma are used in many modern wireless systems including acmimo radio, 802. What are the different multiple access schemes for ofdm. Get your kindle here, or download a free kindle reading app. What are the main differences between mccdma and mcdscdma. Design and analysis of ofdma and scfdma for lte uplink. This page compares sc fdma vs ofdma and mentions difference between sc fdma and ofdma modulation techniques. Used in communications networks such as wimax and lte, ofdma provides air interfaces that are superior to cdma and tdma. Like other multiple access schemes tdma, fdma, cdma, ofdma, it deals with the assignment of multiple users to a shared communication resource. Fdma or frequency division multiplexing access is a method of dividing a single band into 30 discrete channels. As shown in the figure in sc fdma one extra module dft is added before ifft module in the transmitter chain and idft. Sidelink scfdma modulation matlab lteslscfdmamodulate. Single carrier frequency division multiple access sc fdma which utilizes single carrier modulation at the transmitter and frequency domain equalization at the receiver is a technique that has similar performance and essentially the same overall structure as those of an ofdma system.
Fdma is the process of dividing one channel or bandwidth into multiple individual bands, each for use by a single user fig. This paper examines and compares the use of orthogonal frequency division multiple access ofdma and. This paper examines and compares the use of orthogonal frequency. Design and analysis of ofdma and sc fdma for lte uplink enhancement 2677 b. This page describes various multiple access techniques to make use of common resources by multiple userssubscribers.
Fdma and tdma are two pre3g technologies that have been utilized to improve the performance of the 2g network. Lte for umts ofdma and sc fdma based radio access april 2009. Scfdma can be viewed as a special ofdma system with the users signal preencoded by discrete fourier transform dft, hence also known as dftprecoded ofdma or dftspread ofdma. Multiple access fdmatdmacdmaofdma in 4g lte multiplexing is the process of combining multiple signals and transmitting them over a common channel and it. Difference between ofdm and ofdma compare the difference. Department of electrical and computer engineering university of toronto, canada ydepartment of electrical and computer engineering, national university of singapore, singapore. Orthogonal frequency division multiple access ofdma basestations allow multiple users to transmit simultaneously on different subcarriers during the same symbol period. This page on the ofdm vs ofdma describes difference between ofdm and ofdma modulation schemes. Ever since the invention and commercialization of cellular systems, industry leaders and engineers had already foreseen the inevitable overcrowding of simultaneous callers because the number of accessible channels is very limited. However, both are based on the same concept of bundling evenly spaced multiple subcarriers with special characteristics into one. Multiple access fdmatdmacdmaofdma in 4g lte multiplexing is the process of combining multiple signals and transmitting them over a. Frequency division multiple access implemented at the media access control mac layer the user is assigned a specific frequency band in the electromagnetic spectrum, and during a call that user is the only one who has the right to access the specific band. When the resource element grid input to lteslscfdmamodulate spans multiple subframes, the windowing and overlapping is applied between all adjacent sc fdma symbols, including the last symbol of the previous subframe and the first symbol of the next subframe. On sc fdma before applying the ifft the symbols are pre coded by a dft discrete fourier transform.
In this tutorial article, we discuss the reasons for the popularity of ofdma and outline some of the important concepts which are used in ofdma as applied to bcw systems. In ofdm systems, only a single user can transmit on all of the subcarriers at any given time. Performance analysis of scfdma and ofdma in the presence of. Let us understand comparison between them with example of qpsk data symbols which need to be transmitted as shown in the figure1. It just comes down to how many subscribers they can serve at the same time with the same amount of infrastructure deployed. Duplexing can be implemented in either frequency or time domain. The major disadvantage of fdma is the relatively expensive and complicated bandpass filters required.
Orthogonal frequency division multiplexing is a technique for transmitting large amounts of digital data over a radio wave the technology works by splitting the radio signal into multiple smaller subsignals that are then transmitted simultaneously at. Singlecarrier fdma sc fdma is a frequencydivision multiple access scheme. Pdf comparison of ofdma and gfdma for nextgeneration pons. Pdf an analysis of ofdma, precoded ofdma and scfdma for.
Ofdm fdma ofdma each terminal occupies a subset of subcarriers subset is called an ofdma traffic channel each traffic channel is assigned exclusively to one user at any time. In scfdma, the transmitter adds an msize fft stage before the ofdm transmitter. Difference between tdma and cdma difference between. Most of the action takes place at the media access control mac layer layer 2 and the physical phy layer layer 1 or the air interface. The tabular comparison between ofdm and ofdma are also outlined. This page on fdma versus tdma versus cdma provides difference between fdma, tdma and cdma technologies. Ofdma orthogonal frequency division multiple access a cellular air interface based on ofdm for multiple, simultaneous users. Another way to see this intuitively is to use the analogy of making a shipment via a truck. Single carrierfdma is a recently developed single carrier multiple access technique which has similar structure and performance to ofdma. The papr issue led the lte designers to choose scfdma in the uplink direction. Sc fdma means single carrier frequency division multiple access and ofdm means orthogonal frequency division multiplexing. Performance analysis of sc fdma and ofdma in the presence of receiver phase noise gokul sridharan and teng joon limy edward s. Llttee ooffddmm tteecchhnnoollooggyy to overcome the effect of multi path fading problem available in umts, lte uses orthogonal frequency division multiplexing ofdm for the downlink that is, from the base station to the terminal to transmit the data over many narrow band careers of 180 khz each instead of. Analysis of scfdma and ofdma performance over fading.
Comparison of ofdma and gfdma for nextgeneration pons. Different users are separated in the frequency domain. Difference between fdma and tdma difference between. The detailed specification of lte is given in table 1. A new air interface for long term evolution myung, hyung g.
In digital twoway radio systems, there are two main channel access methods used today. This page compares sc fdma vs ofdm and mentions difference between sc fdma and ofdm modulation techniques. Jul 31, 2014 ofdm vs ofdma ofdm orthogonal frequency division multiplexing and ofdma orthogonal frequency division multiple access are both wideband digital communication technologies with a slight difference between them. An introduction to lte systems is presented in this manuscript. This page provide comparison between ofdm vs cdma and mentions difference between ofdm and cdma technologies. Jun, 2015 lte for umts ofdma and sc fdma based radio access april 2009. Both ofdm and cdma are wideband wireless digital communication systems widely used for fixed as well as mobile applications.
Why is the implementation of ofdm fdma the most straightforward. Sc fdma singe carrier fdma presents the benefit of a single carrier multiplexing of having a lower peaktoaverage power ratio. Multiple access technique lecture 8 website staff ui. Design and analysis of ofdma and scfdma for lte uplink enhancement 2677 b.
631 212 1361 93 742 1527 957 900 379 963 634 20 815 1019 180 1282 1344 1137 737 212 1095 1453 566 624 1253 985 508 1178 386 997 599 1488 518 560 754 1214 811 1102 388 836 318 1407 555 1019