Technically gsm global system for mobile communications, originally from groupe special mobile. Cdma, unlike tdma, virtually allows numerous users to use the channel at the same time. Oct 10, 2017 difference between ofdm and cdma technologies. Supervised by munawwar mahmud sohul thesis submitted by md. Adjacent frequency bands interference generated because of nonlinearity of satellite transponder amplifier. This page provide comparison between ofdm vs cdma and mentions difference between ofdm and cdma technologies. Multicarrier and spread spectrum systems from ofdm and mc cdma to lte and wimax second edition k. Orthogonal frequency division multiplexing ofdm is a modulation method that divides a channel into. The suitability of ofdm as a modulation technique for wireless telecommunications, with a cdma comparison.
Towards a comprehensive comparison of ofdm and cdma techniques. In telecommunications, orthogonal frequency division multiplexing ofdm is a type of digital modulation, a method of encoding digital data on multiple carrier frequencies. Gsm and cdma are competing wireless technologies with gsm enjoying about an 82% market share globally. Cdma code division multiple access and ofdm orthogonal frequency division multiplexing are two well known air interface technologies in modern mobile communication. The advantages of ofdm orthogonal frequencydivision multiplexing immunity to delay spread and multipath resistance to frequency. Often the ofdm cdma choice will not be easy, but many systems these days are tending to opt for the ofdm ofdma solution over the cdma solution. Lte is better at multipath signal handling with no signal interference and. From what ive gathered, the primary differentiation between dsss and ofdm comes in a congested or constrained rf environment. Interference between the user of adjacent time slots is generated because of incorrect synchronization. We also apply turbo codes and or bitinterleaved coded modulation with soft input soft. Towards a comprehensive comparison of ofdm and cdma techniques dimitrios a. John ya john has over 15 years of research and development experience in the field of wireless communications.
Direct sequence code division multiple access dscdma and orthogonal frequency division multiplexing ofdm systems are two options for broadband. But what are gsm and cdma, and how do they affect your phone, service, and coverage. Meanwhile, 3g cdma answers will coexist with these higherbandwidth ofdm based totally answers until ofdm based total technology is fully capable of handing over an equal or better cost proposition to the stop person, together with ubiquitous coverage, compelling broadband services, providergrade voip replacing circuitswitched voice services. Difference between lte and cdma difference between. However, the main focus is to differentiate between 3g and cdma. Individual conversations are encoded with a pseudorandom digital sequence. He has worked for a number of companies around the world including qualcomm inc. When undertaking an ofdm cdma comparison, or more correctly an ofdma cdma comparison, it is necessary to take a look at all the advantages and disadvantages. Cdma consistently provides better capacity for voice and data communications than other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3g technologies are built. Fundamentals of communications access technologies. Thesis on evaluation performance between ofdm and cdma in perspective of wireless communication. Introduction up until the end of the 20th century, there was a fairly clear division between the cellular industry and other telecommunication. Cdma performs better in multi cellular case where in single frequency is allocated to all the base stations.
Cdma ebm performance can be improved with better pilot code design 10% ofdm results match with qualcomms. Ofdm based system in single cell environment can allocate about 2 to 10 times more subscribers compare to cdma. Comparing the advantages and disadvantages of ofdm, ofdma and cdma 4glte technology uses ofdma both ofdm and ofdma are used in many modern wireless systems including acmimo radio, 802. Comparison of cdma and ofdm systems for broadband power. For this reason, cdma was also investigated so that the performance of cdma could be compared with ofdm. It was found that ofdm performs extremely well compared with cdma, providing a. Theres a variant of ofdm thats directly comparable to cdma, and thats orthogonal frequency division multiple access, or ofdma. And wcdma and lte are specific standards that use them.
Dec 03, 2016 comparison of cdma, tdma,ofdm,cdma2000, ssma,wcdma 1. Cdma and ofdm the convergence of wireless mobile services. Ofdmascfdma in 4g lte part 2 streams of data, in the form of bits, reaches network gateway from various sources. Each user of the channel takes turns to transmit and receive signals. Cdma is short for code division multiple access and it is also a kind of multiplexing that allows several signals to use a single transmission channel.
Both ds cdma and ofdm are well understood and proven in other conventional narrowband commercial radio technologies e. These are two very different methodologies use to accomplish the same task, use frequency spectrum much more efficiently than the traditional dedicated fixed frequency transmitting system. Cdma versus ofdm, a performance comparison in selective fading channels abstract. Ofdm for wideband cellular systems yong peng, giridhar mandyam, senior member, ieee, and dinesh rajan, senior member, ieee abstractin this paper, we compare the downlink transport spectral ef. Gsm uses tdma and fdma for user and cell separation. Performance is affected because of adjacent time and frequency slots.
The receiver undoes the randomization to collect the bits together and produce the original data. The suitability of ofdm as a modulation technique for. Ofdm, dscdma, and mccdma systems with phase noise and. After more than 20 years, it appears that an almost universallyaccepted standard for mobile radio may finally be implemented, bringing to an end the standards war between carriers that deployed tdmagsm for second generation and carriers that deployed cdma for second generation. In ofdma, both time and frequency are distributed among users.
In telecommunications, orthogonal frequencydivision multiplexing ofdm is a type of digital transmission and a. In telecommunications, orthogonal frequencydivision multiplexing ofdm is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. Fdma versus tdma versus cdmadifference between fdma,tdma,cdma. Because dsss is transmitting as many bits as possible all at once, it runs the risk of having some of the transmission disrupted in transit should the rf become less than ideal. Sep 25, 20 evaluation performance between ofdm and cdma 1. Verizon and sprint, on the other hand, use cdma, which stands for code division multiple access. 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 networks, and 4g mobile communications. Gaussian noise tolerance of ofdm is better compare to cdma.
It is known that ofdm and cdma modulation techniques are used in modern wireless. Aug 11, 2016 multiple access fdmatdma cdma ofdma in 4g lte multiplexing is the process of combining multiple signals and transmitting them over a common channel and it is implemented on telecommunication. The maturity of these approaches, however, is vastly different in the world of uwb. Gsm as a consumer, there are just a few things you need to be concerned with when it comes to the big differences between cdma and gsm devices.
Cdma versus ofdm, a performance comparison in selective. Cdma uses a spreadspectrum multiple access technique for transmission, whereas lte is the 4 th generation mobile communication standards that uses orthogonal frequency division multiplexing ofdm that transmits data over many narrowed carriers of 180 khz each. With the advent of 4g and the adoption of lte and lteadvanced as the standard by the majority of network carriers. Comparison between mc cdma and cdma ofdmoqam systems in. Adjacent frequency bands interference generated because of nonlinearity of satellite. It is used for lte 4g but is also the basis for wiimax and wifi. These techniques form the basis of understanding the world of 3g4g wireless communication systems as well as that of the newest 5g. If we use multiple antennas at the transmitter as well as receiver. Ofdm orthogonal frequency division multiplexing cablefree. The goal is to dramatically increase the number of essentially simultaneous users within a.
Thus, transmitting and receiving are all done by various users simultaneously. This tutorial is part of the most recent update to course 101, chapter 6, october 2008. In ofdmtdma, timeslots are attributed to each users and the whole ofdm symbol is dedicated to one user. A second and rather novel technique is orthogonal frequency division multiplexing ofdm applying maximumlikelihood detection mld at the receiver. Ofdm ofdm stands for orthogonal frequency division multiplexing. Most third generation mobile phone systems are proposing to use code division multiple access cdma as their modulation technique. Shannon capacity cdma vs ofdma january 26, 2015 capacity, fundamentals 4g, lte, ofdm, shannon capacity, snr john ya we have previously discussed shannon capacity of cdma and ofmda, here we will discuss it again in a bit more detail. Gsm vs cdma whats the difference between the two technologies. Multiple access cdma, orthogonal frequency division multiplexing ofdm, multiple input multiple output mimo. Difference between tdma and cdma difference between. Orthogonal frequency division multiplexing, is a form of signal modulation that divides a high data rate modulating stream placing them onto many slowly modulated narrowband closespaced subcarriers, and in this way is less sensitive to frequency selective fading.
Timedivision multiple access tdma provides multiuser access by chopping up the channel into sequential time slices. Both ofdm and cdma are wideband wireless digital communication systems widely used for fixed as well as mobile applications. Suitability of ofdm for wireless communications, with a cdma. Orthogonal frequencydivision multiplexing wikipedia. Gsm and cdma are different technologies that phones use to connect. The credit for the development of the cdma standard goes to the american wireless telecommunications research and development company, qualcomm. This acronym designates protocols for allowing multiple users to the same radio channel. Whereas, cdma stands for code division multiple access. We focus our work on dscdma is95, umts, cdma2000 and ofdm. Ofdma broadband overlay timeline ofdm based solutions will be builtout over time as demand grows and spectrum becomes available 3g cdma wan networks will coexist with ofdm based solutions until. When they both are used together, they will be termed as 3g cdma. Ofdm has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, dsl internet access.
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