The signal occupies a bandwidth much greater than that which is necessary to send the information. Performance of dsss system in presence of noise is better than fhss system. The techniques used for this are tdma time division multiple access, fdma frequency division multiple access and cdma code division multiple access. The fact that cdma2000 1x has the ability to support both voice and data services on the same carrier makes it cost effective for wireless operators. It has the ability to carry 64 kbps to 120 mbps of data rates. Due to codeword allocated to each user, interference is reduced. It is wellmatched with other cellular technologies.
Compared with gsm phones, cdma mobile phone has the following advantages. The main benefits of the use of cdma as a multiple access scheme are. In 2000, gsm become very popular technology worldwide. The goal is to dramatically increase the number of essentially simultaneous users within a specific portion of. Thus, it is used in the rural areas where gsm cannot cover. It provides very cost effective products and solutions. Gsm is the combination of both time and frequencydivision multiple access tdmafdma. In general, spread spectrum communications is distinguished by three key elements. International roaming facility permits the use of one phone throughout the world unlike cdma which will work in asia, but not european nations. It has more number of users can share the same bandwidth.
Tdma can easily adapt to transmission of data as well as voice communication ability to carry 64 kbps to 120 mbps of data rates disadvantages of tdma. The advantages and disadvantages of fdma with respect to tdma or cdma are. Cdma cannot offer international roaming, a large gsm advantage. Gsm standard still evolving and improved with new features and services. Multiple users occupy different spectrum at a time a. It offers significant advantages over the schemes used in the previous 2g systems that were predominantly tdma based schemes. The technology is commonly used in ultrahighfrequency uhf cellular telephone systems, bands ranging between the 800mhz and 1.
Ifdma a scheme combining the advantages of ofdma and. Cdma, code division multiple access, alternatively signifies a more powerful digital air interface standard, equating about eight to fifteen times the capacity of conventional analog cellular systems. This article is all about the difference between gsm and cdma technology. What are the advantages of cdma over tdma,fdma,gsm, etc. In cdma, calls do not drop because of hand offs because unlike tdmagsm, cdma handoffs are controlled by the phone, not the network. Cdma is codedivision multiple access abbreviation, full known as code division multiple access, is a more advanced digital interface technology, which is characterized by a high frequency of. In around 1995 this was a huge technology argument, with intense marketing and lobbying.
The use of cdma offers several advantages and it is for this reason that cdma technology has been adopted for many 3g cellular telecommunications systems. Ifdma a scheme combining the advantages of ofdma and cdma. Gsm stands for global system for mobile communications. Cdma can be implemented in several ways, two of which are frequency hopping and direct sequencing. Basic note on spread spectrum cdma signals 3 figure 1. Gsm technology global system for mobile communication or groupe special mobile to standardize cellular communication thoughout europe. Gsm and cdma spectrum frequencies the cdma network operates in the frequency spectrum of cdma 850 mhz and 1900 mhz while the gsm network operates in the frequency spectrum of gsm 850 mhz and 1900 mhz. Cdma is almost exclusively used in the united states and some parts of canada and japan. Cdma is relatively not popular, and the network is not as mature as gsm. There are some important advantages of cdma code division multiple access are given below, the cdma does not require any synchronization. Advantages and disadvantages of gsm information technology essay.
The goal is to dramatically increase the number of essentially simultaneous users within a. Gsm is used all over the world with more than 450 million users. Ds cdma directsequence code division multiple access is a multiple access scheme based on dsss, by spreading the signals fromto different users with different codes. Second, the use of advanced softswitching technology allows mobile phone is not gsm phones are dropped. High synchronization overhead using tdma system frequencyslot allocation is to be complex. In cdma technology there is no time limitation slot division for using the band width and sending and receiving the data like in. Using cdma it is possible for a terminal to communicate with two base stations at once. Multipleaccess techniques tho lengoc page5 cooperative cdma in cooperative cdma, k users simultaneously transmit their codewords, x is, one from each user codebook, simultaneously in time. Phil flikkemas usf briefing introduction to spread spectrum pdf about the capacity of a ds spread spectrum cdma cellular system pdf overview of modulation techniques for wireless pdf prof. This is done in gsm via gaussian minimum shift keying gmsk.
Throughout this article, ifdma is derived from a cdma perspective as well as from. Gsm technology was developed by europe in1982 but its massive deployment started in 1992. In cdma, signal to be transmitted spread across the wide bandwidth due to spreading. Keyword cellular communication, multimedia, cdma, 3gsm. The unique features, benefits, and performance of cdma2000 make it an excellent technology for highvoice capacity and highspeed packet data. The multiuser receiver knows the spreading waveforms or codebooks of all users. The advantages of using a cdma technique over other spread spectrum techniques are 1. Advantages relative to tdma and fdma no guard bands or guard times are typically required no equalizer is typically required, when a rake receiver is used the is95 cdma 2g forward link a.
It has gained widespread international acceptance by cellular radio system operators as an upgrade that will dramatically increase both their system capacity and the service quality. Cdma technology has given significant advantages over other parallel technologies in terms of spectrum efficiency and overall performance. Technically gsm global system for mobile communications, originally from groupe special mobile. The bandwidth of the data signal is now multiplied by a factor n ds. Throughout this article, ifdma is derived from a cdma perspective as well as from an ofdma perspective and the properties of the scheme and. One of the main advantages of cdma is that dropouts occur only when the phone is at least twice as far from the base station.
Advantages, disadvantages and applications of direct. Tdma is the widespread type of service that is used in. Such standards included cdma ds, cdma mc, and some tdd technologies. Advantages, disadvantages and applications of cdma code. Tdma time division multiple access and cdma code division multiple access. You can find the guidelines for evaluation, known as m. Cdma as one of the major problems facing the development of telecommunications, bandwidth demand has driven the search for protocols that could be used to maximize bandwidth efficiency. The use of cdma as the multiple access technology, combined with the qpsk modulation format used provides significant.
Advantages and disadvantages of gsm information technology. 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. A benefit is reduced cost at the base station and longer battery life for the mobile unit. Dec 10, 2016 disadvantages of cdma due to its proprietary nature, all of cdmas flaws are not known to the engineering community. Most efficient use of available bandwidth the foremost advantage is the large band width and its equivalent effect utilization for sending and receiving the data. Cdma is a form of direct sequence spread spectrum communications. Dscdma directsequence code division multiple access is a multiple access scheme based on dsss, by spreading the signals fromto different users with different codes. Code division multiple access for wireless communications. Supporting both voice and data, the standard was devised and tested in various spectrum bands, including the new imt2000 allocations. When to answer a question about umts its somehow related to soft handover in wcdma networks compared with tdmafdma networks like gsm anyhow for a general view.
The itur went through an evaluation process of them all. Cdma allows far greater development and the use of broad band devices such as wireless laptop modems. Gsm is established, started in the mid80s due to which a more stable network with healthy features are available. Multiple accesses multiplexing for short enable multiple signals to occupy a single communications channel. In particular, it was the standard for all of europe. Gsm and cdma are competing wireless technologies with gsm enjoying about an 82% market share globally. Multiple access technique lecture 8 website staff ui. Basics idea about cdma technology and its applications. Disadvantages of cdma due to its proprietary nature, all of cdmas flaws are not known to the engineering community. Cdma allows far greater development and the use of broad band devices such as wireless laptop modems, gps system units and other innovative devices. Advantages of cdma2000 cdma2000 benefited from the extensive experience acquired through several years of operation of cdmaone systems. Cdma calls drop because errors in the stream due to interference and weak signals.
Advantages of gsm less signal deterioration inside buildings. Introduction to cdma code division multiple access cdma is a radically new concept in wireless communications. In 1985, the fcc allocated three frequency bands to spread spectrum communications. Mar 20, 2020 such standards included cdma ds, cdma mc, and some tdd technologies. It avoids intentional interference such as jamming effectively. Tdma is the costeffective technology to convert an analogue system to digital. Both the technologies can be used with 3g standard phones, but 3g gsm speeds can be faster than 3g cdma speeds. A cdma receiver can retrieve the wanted signal by multiplying the receive signal with the same code as the one used during transmission. As a result, cdma2000 is a very efficient and robust technology. Global system for mobile communication technology mobile device investigations program technical operations division. Fitzek universita di ferraracode division multiple accessfrank h. It is mainly a channel access method that is used for shared medium networks as well as a digital transmission technology that allows its users to access a single radiofrequency channels without any interference. Such efficiencies can best be grasped when we contrast cdma with gsm the most successful implementation of time division and frequency division technology. Tdma is the widespread type of service that is used in north.
Cdma, code division multiple access an implementation of direct sequence spread spectrum, dsss, and was used almost universally for 3g mobile communications standards as it provided an excellent format as a multiple access scheme. Capacity can be increased by reducing the information bit rate and using an effi cient digital speech coding scheme see chapter 8 20. Fdma and tdma usually need reuse factors of 4 7 capacity increased 47 fold. Gsm techology has been matured since long and hence gsm mobile mobile phones and modems are widely available across the world. Other advantages such as lowprobability of interception, privacy, and antijam capability are more relevant for military needs. Thus it is used in the rural areas where gsm cannot cover. Due to inherent advantages of cdma over tdma and fdma such as user capacity, soft hand offs and security, etc. As the transmitted information is below the noise floor, it is difficult to intrude the cdma spectrum. Cdma code division multiple access or cdma has its roots in wwii era spread spectrum technology. The bandwidth of the coded data signal is chosen to be much larger.
There are some advantages of direct sequence spread spectrum which are given below, it has best discrimination against multipath signals. In this presentation suitable multiple access for future generations has been presented. Advantages of gsm following are the advantages of gsm. The receiver, knowing the code sequence of the user, decodes the received signal and recovers the original data. Rates for global evolution edge cdma, are 3g gsm based standards.
First, the transmission power is extremely small, so conversation is not only less radiation, but also longer battery life mobile phones. Advantages of cdma2000 nortel networks confidential pg 12 lower cost to operate always on anytime, anywhere and in any form voice and multimedia self service, intuitive simpler for the end user secure, trusted and reliable platform for services creation cdma2000 advantages. Code division multiple access cdma is a sort of multiplexing that facilitates various signals to occupy a single transmission channel. The scheme has been introduced in 10 as interleaved frequency division multiple access ifdma. People who complain about cdma handoffs have no idea when a handoff occurs, so they cant say calls drop because of a handoff. Fitzek04 february 2003lecture 2the following text is taken partially from my phd thesis. Technological advances required for implementation are simple.
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