NTC362 Time Division Multiple Access, Frequency Division, Multiple Access, and Orthogonal Frequency Division Multiplexing

An assignment explaining TDMA, FDMA, and OFDM in networking.

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Running head: TIMEDIVISION MULTIPLE ACCESS,FREQUENCY1Time Division Multiple Access, Frequency Division, Multiple Access, and OrthogonalFrequency Division MultiplexingNTC362Daniel AldamaExplain the key differences between Frequency Division Multiple Access (FDMA), TimeDivision Multiple Access (TDMA), and Code Division Multiple Access (CDMA) in terms oftheir channel access methods, advantages, and disadvantages. In your response, provide real-world applications of each technology, discussing their impact on network efficiency and userexperience. Additionally, consider the advancements in CDMA technology, such as CDMA2000, and explain how it enhances performance and security. Your response should be 800-900words.

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TIME DIVISION MULTIPLEACCESS,FREQUENCY2Frequency Division Multiple AccessAs the name implies, Frequency Division Multiple Access (FDMA), utilizesFrequency Division Modulation (FDM) to separate the given spectrum into individualanalog bands or channels. A simplified view of how this is done can be seen in figure 1below. Each of these channels is then able to facilitate communication for a single user.According to (Goleniewski, 2007)each FDMA cell is able to facilitate about 60 users,which is veryalow number by current standards.Figure 1.Goleniewski, L. (2007). Example of FDMA channel separation.FDMA was short lived as a viable option for commercial use on its own;however,it was an important step in the right direction. I say this because it is now a critical partof multiple other techniques, where it is used to divide spectrum into channels beforeother modulation techniques are applied. Once such technology is the one explainednext.Time Division Multiple Access

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TIME DIVISION MULTIPLEACCESS,FREQUENCY3Time Division Multiple Access or TDMA is a channel access that is shared outand is used on medium networks. This is also known as the 2G network that is slowlybeing phased out. What TDMA does is it allows multiple users to share the samechannel within a network. This is accomplished by splitting a single channeling into twoor three different time slots to maximize the data flow. The communication then can takeplace by allowing the users communication to pass through the channel at differentintervals. When the communication is picked up on the other end the intervals arereconstructed as if each user was using a single line by themselves. Thiscommunication technology is used in the cell phone industry. “DMA is used by Digital-American Mobile Phone Service (D-AMPS), Global System for Mobile communications(GSM), and Personal Digital Cellular (PDC)”(Time division multiple). Since TDMAcannot be used in the exact same way these companies have to implement it indifferent ways. There are many advantages to using this system and here are a few ofthem:oTDMA can easily adaptableoTDMA provides users with an extended battery lifeoTDMA is the most cost effectiveSince TDMA is use a split channel it can be easily adapted to not only datatransmissions, but voice communications as well. This is a great feature becauseanything that can do two things is going to be an asset. Having that ability to adapt onthe fly without flipping a switch can save time and money for a company. Having the

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TIME DIVISION MULTIPLEACCESS,FREQUENCY4ability to adapt to either communication type is great, but adding that to a channel thatcan support two or three users id even better.Another advantage that this provides is a longer battery life for user. This mightseem a little strange, but since the channel is divided into two or three segments andcommunication takes place in intervals the devices is not in constant communication.The only time that the devices are used in when data or voice communication is takingplace; this is why the battery life is extended. Now how much battery life it does save, isa different question.The last advantage that is listed is the fact that the system is truly cost effectivein terms of signal conversions. Having the ability to convert analog signals to digitalsignals is a plus because the technology already does so much. When taking intoaccount everything that the technology can do you can see why it is truly cost effective.It is like a Swiss army knife by providing multiple functions to a cell phone network whilemaximizing the signal to its full capacity.There are however disadvantages that this can bring a caller. Since users are notassigned a specific channel then can lose or drop calls. This happens because the slottime is not assigned to the user and when they go to roaming this may or may not allowthe user to call out because the particular slot time is being occupied. This can reallystink especially if you are trying to make an important call. The bottom line is that withnew technology, comes better improvements with existing systems. These systems arenot that bad because without them we would have nothing, but as we are alwayslooking for the next best thing.

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TIME DIVISION MULTIPLEACCESS,FREQUENCY5CDMACode Division Multiple Access (CDMA), is atechnology based on spreadspectrum: Direct Sequence Spread Spectrum (DSSS) to be precise. What makes itunique in relation to TDMA or FDMA is that spread spectrum allows users to operate onthe same frequency simultaneously. Early CDMA operated at 1.25 MHz, with newergenerations, also known as Wideband CDMA, operate at 3 MHz, 10 MHz, or 15 MHz(Goleniewski, 2007).The larger channels of the latter allow it to carry more calls andimplement superior encryption. Compared to the analog technologies discussed in theprevious two sections the spectral efficiency of first generation CDMA was 10 to 20times greater. This translates into being able to squeeze 10 to 20 times the data giventhe same amount of spectrum.As mentioned above CDMA allows users to share the same frequency. This isaccomplished by using code to delineate users instead of frequency, which as the nameimplies is the heart of CDMA. This provides CDMA networks with a better resistance tointerference and better security. This is how. DSSS converts each bit into micro pulsescalled chips. Chips are very fast pulses used to represent each bit as its ownpseudorandom bit pattern (PN code). First generation CDMA utilizes a 64-bit (read chip)PN code. What this means is that each 1 bit is represented by a 64 chip pattern, and a 0bit is represented by the exact inverse of the 1 bit. Consequently, even if some 1s and0s are lost from the pattern, there are usually still enough intact for the receiver todetermine the intended bit. The result is much higher quality, less error prone signal.
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