Difference between FDMA, TDMA, and CDMA
These are all techniques for data transfer and communication. They are quite effective, but they are employed in several ways due to their unique features. In this article, you will learn about the difference between FDMA, TDMA, and CDMA. But before discussing the differences, you must know about FDMA, TDMA, and CDMA with their advantages and disadvantages.
What is FDMA?
FDMA is an abbreviation for "Frequency Division Multiple Access". It is a form of channelization protocol. In this system, the bandwidth is separated into different frequency bands. Each station is assigned a band to transmit data, and that band is always reserved for that station.
A tiny band of unused frequency separates different stations' frequency bands, and these unused frequency bands are known as guard bands, which prevent station interference. It is similar to the data link layer access approach, in which the data link layer at each station instructs the physical layer to generate a bandpass signal from the data provided to it. The signal is generated in the assigned band, and no physical multiplexer is present at the physical layer.
Advantages and Disadvantages of FDMA
There are various advantages and disadvantages of FDMA. Some main advantages and disadvantages of FDMA are as follows:
- In terms of hardware resources, it is very simple and easy to use.
- Because FDMA is efficient, it can manage a smaller user population.
- The system's complexity is modest.
- All stations may constantly run for 24 hours without waiting for their chance.
- The reduced information bit rate can have a positive impact on capacity.
- It reduces inter-symbol interference.
- It only works with analogue signals.
- There isn't much room for flexibility. Therefore, existing traffic patterns must be slowly changed.
- The transponders require extensive bandwidth.
- The traffic's carrying capacity is not very high.
- RF (Radio Frequency) filters must fulfil stringent adjacent channel rejection specifications. It can enhance the system's cost.
- The highest bit rate per channel is small and fixed.
What is TDMA?
TDMA is an abbreviation for "Time Division Multiple Access". It is a channelization system that divides channel bandwidth into many stations simultaneously. Each station is assigned a time slot and may only transmit data during the same time slot. Each station should be aware of the beginning and location of its time slot. Synchronization between stations is needed for TDMA. It is a form of data link layer access mechanism. The data link layer instructs each station to utilize the assigned time slot.
It is utilized in digital 2G cellular network systems like Personal Digital Cellular (PDC), GSM, IS-136, and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for mobile phones. Western Union's Westar 3 communications satellite was the first to utilize it in satellite communication networks in 1979. It is commonly used for upstream traffic from premises to the operator in combat-net radio systems, satellite communications networks, and a passive optical network (PON).
TDMA is a form of time-division multiplexing (TDM) in which numerous transmitters are connected to a single receiver rather than a single transmitter. The uplink from a cellular phone to a base station is particularly troublesome because it may move and modify the timing advance needed to match the transmission gap from its peers.
Advantages and Disadvantages of TDMA
There are various advantages and disadvantages of TDMA. Some main advantages and disadvantages of TDMA are as follows:
- As cell sizes reduce, TDMA delivers significant investment dollars in space, support, and base-station hardware.
- It may transmit data at speeds ranging from 64 kbps to 120 Mbps.
- It separates clients based on time guarantees that no interference from concurrent transmission will occur.
- TDMA enables administrators to do administrations such as fax, voiceband information, SMS, and applications such as mixed media and video conferencing.
- It extends the client's battery life by communicating alone for a part of the time during discussions.
- TDMA may surely adapt to information transmission and voice correspondence.
- The user won't be connected to a call if all of the time slots in the current cell and the cell they are entering are already taken because they have been allotted a specific slot.
- In TDMA, frequency/slot allocation will be complicated.
- In TDMA, high data rates needed equalization.
- Network and spectrum planning is a complex and time-consuming process requiring great expertise and resources.
- The focus is on organization and range arranging.
What is CDMA?
CDMA is an abbreviation for "Code Division Multiple Access". It is a combination of FDMA and TDMA in which resources are allocated based on frequency and time. FDMA divides the frequency band across several users for the duration of the session, whereas TDMA permits each user to utilize the full frequency band for a defined session. On the other hand, the CDMA system takes advantage of both systems by allowing several users to simultaneously utilize the same frequency band defined by a unique code.
These codes are selected in such a way that if the code is utilized for a second time, the user who knows the code may identify that specific user among the other users. This method may only be applied to a specific number of users because each user is a source of noise for the receiver. As a result, it is highly susceptible to noise. Because as the number of user numbers increases, the noise also increases. As a result, the system may collapse.
Advantages and Disadvantages of CDMA
There are various advantages and disadvantages of CDMA. Some main advantages and disadvantages of CDMA are as follows:
- It has an extremely high spectral capacity to support many users in MHz of bandwidth.
- There is no need for synchronization.
- CDMA channels are difficult to decode, so they enhance cellular communication security.
- It offers better secure transmission.
- Dropouts occur only when the user is twice the distance from the base station.
- One of the main issues with the CDMA system is channel pollution, which occurs when a user's phone has two or more cell sites, but only one of them is powerful.
- It is not a mature organization because the CDMA is still new compared to GSM.
- CDMA needed time synchronization.
- As the number of users rises, the CDMA system's performance decreases.
- It has a high price because of the greater equipment.
Key differences between FDMA, TDMA, and CDMA
Here, you will learn the various key differences between FDMA, CDMA, and CDMA. Various differences between FDMA, TDMA, and CDMA are as follows:
- FDMA distributes a single bandwidth among multiple stations by dividing it into sub-channels, whereas TDMA only shares the time of transmission through the satellite, not the channel. On the other hand, CDMA shares both time and bandwidth among multiple stations by allocating a unique code to each slot.
- FDMA only requires the guard bands between adjacent channels, whereas TDMA requires the guard time of the adjacent slots. On the other hand, CDMA requires both guard time and guard bands.
- FDAM has a low data rate, whereas TDMA has a medium data rate. On the other hand, CDMA has a high data rate.
- FDMA doesn't need any synchronization, whereas TDMA system needs synchronization. On the other hand, CDMA doesn't need any synchronization.
- FDMA has a very low cell capacity, and TDMA has a very restricted cell capacity as well. On the other hand, CDMA has no capacity restriction for a channel, although it is interference-limited.
- The FDMA does not require a codeword, and neither does the TDMA. On the other hand, CDMA needs the codeword.
- FDMA happens by filtration in the frequency domain, while TDMA involves synchronizing the time domain. In contrast, CDMA happens through codes and sophisticated receivers.
- FDMA has little flexibility, but TDMA has moderate flexibility. On the other hand, CDMA is highly flexible.
Head-to-head comparison between FDMA, TDMA, and CDMA
Here, you will learn the head-to-head comparisons between FDMA, TDMA, and CDMA. The main differences between FDMA, TDMA, and CDMA are as follows:
||FDMA is an abbreviation for Frequency Division Multiple Access.
||GPRS is an abbreviation for Time Division Multiple Access.
||CDMA is an abbreviation for Code Division Multiple Access.
|Mode of Operation
||It distributes a single bandwidth among multiple stations by dividing it into sub-channels
||It only shares the time of transmission through the satellite, not the channel.
||It shares both time and bandwidth among multiple stations by allocating a unique code to each slot.
||It has a little flexible.
||It has moderate flexibility.
||It has high flexibility.
||It doesn't require a codeword.
||It also doesn't require a codeword.
||It needs a codeword.
|Rate of Data
||It has a low data rate.
||It has a medium data rate.
||It has a high data rate.
|Mode of Data transfer
||It uses continuous signals for data transmission.
||It uses signals in bursts for data transmission.
||It uses digital signals for data transmission.
||It doesn't need any synchronization.
||It requires synchronization.
||It also doesn't require any synchronization.
||Every terminal has its own constant frequency.
||Every terminal on the same frequency is active for just a short period of time.
||Every terminal may remain operational at the same time and in the same location without interruption.
||It has a limited cell capacity.
||It also has a limited cell capacity.
||It has no capacity restriction for a channel, although it is interference-limited.
||It has a high cost.
||It has a low cost.
||Its installation cost is high, but the operational cost is low.
|Guard times and Bands
||It needed guard bands.
||It needed guard times.
||It needed both guard times and guard bands.
||It doesn't require an equalizer.
||It needed an equalizer
|| RAKE receiver may be possible in CDMA.
||It is a very reliable, well-established, and straightforward protocol.
||It is highly flexible, entirely digital, and well-established.
||It is more flexible, needs less frequency planning, and offers a softer signal handover.
||It is very flexible, and the frequencies are limited.
||It requires guard space.
||It works with extremely complicated receivers, and senders/transmitters need a more complex power control method.
FDMA is generally combined with SDMA (Space Division Multiple Access) and TDMA, whereas TDMA holds the standards in fixed networks. Many mobile networks utilize it in conjunction with SDMA or FDMA. On the other hand, CDMA continues to face significant challenges, and it is more complicated and has lower expectations. It will most likely be compatible with FDMA and TDMA.