Which of the following multiple access technique can be used for using the entire available bandwidth for a user FDMA TDMA CDMA OFDMA?
In the post on the GSM Standard, we learned that data and other signals are transmitted through allocated bands of frequencies called channels. In this post, we shall have a look at different multiple access schemes that are employed on these channels to facilitate wireless communication. Show
What are Multiple Access Schemes?
An Analogy A simple analogy that can be employed to understand these Multiple Access Schemes is a room in which there are many people trying to talk to someone else in the same room at the same time. This would lead to confusion as no one would be able to understand which message is directed at them. Hence, by restricting how each person can talk to the other while in the room, it can be made sure that everyone understands what’s being spoken. First, we shall have a look at the three main multiple access schemes, namely:-
Time Division Multiple Access
In the analogy about the room, by providing each pair of people to converse at different slots of time, it can be made sure that everyone receives messages intended for them. This is exactly how TDMA works.
The figure shows the functioning of TDMA, with the spectrum having been split into eight time slots. The Mobile Station (MS) at terminal A has been allocated time slot 1 to communicate, while MS at B uses the spectrum at time slot 6. Advantages
Disadvantages
Use of TDMA
Code Division Multiple Access
In the analogy about the room, if we ensure that each room is filled with people such that each pair of people speak a unique language, we ensure that only those who understand the language can decipher what’s being said to them. Though the analogy sounds weak practically, it is exactly how CDMA works. The figure shows how in CDMA, the channels are split on the basis of code, ensuring that the entire spectrum and time are available for communication. Advantages
Disadvantages
Used of CDMA
Frequency Division Multiple Access
Going back to our analogy about the room, if each person speaks in such a way that the pitch of their voice is different, the listener would theoretically be able to obtain what the source is trying to convey. This is definitely not practical, and is just a representation of how FDMA works. The figure above shows how different frequency bands are allocated for different channels. Advantages
Disadvantages
Use of FDMA
We have seen the three major multiple access schemes, now we move on to other multiple access schemes being used in communication. Space Division Multiple Access
Advantages
Disadvantages
Use of SDMA
Power Division Multiple Access
Advantages
Disadvantages
Beam Division Multiple Access
Advantages
Disadvantages
Use of BDMA
Non Orthogonal Multiple Access (NOMA)
Sparse Code Multiple Access (SCMA)
Orthogonal Frequency Division Multiple Access (OFDMA)
Advantages of Orthogonal Frequency Division Multiple Access (OFDMA)
Disdvantages of Orthogonal Frequency Division Multiple Access (OFDMA)
There are several multiple access schemes that could be employed for 5G. The one used (if not a hybrid of multiple schemes) will be chosen as a result of the standardization process for the technology. In this post, we have seen the different multiple access schemes that have been employed in the wireless communication industry, along with its various advantages, disadvantages, and uses. We hope the explanations were clear for you. If you have any queries, please let us know in the comments section below! About the author Gopikrishnan is an Electronics and Communication Engineering undergraduate at Amrita School of Engineering, Coimbatore, and is quite interested in anything wireless. He loves to tinker around with any Raspberry Pis or Arduino devices lying around, and is a huge fan of Linux and FOSS. Memes, Movies, and Music are what fuels him for those late-night coding sessions. Which of the following multiple access method the entire bandwidth is used simultaneously?CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel.
In which of the following multiple access schemes can each user use all of the available bandwidth for a limited time period?Time Division Multiple Access
In this scheme time is divided into slots and each slot is assigned to different user. They can use the whole spectrum for a limited time.
Which is better CDMA or TDMA or FDMA?FDMA supports a low rate of data. TDMA supports a medium rate of data. CDMA supports a high rate of data.
Which of the following technique is suitable for digital transmission options CDMA FDMA TDMA all of the above?It usually optimized the use of the bandwidth in an efficient manner. So the correct answer is CDMA.
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