Skip to main content

Comparison of FDMA, TDMA, & CDMA | Methods of Transmitting and Receiving ...




Two key modulation techniques utilized in 2G GSM are TDM and FDM. The advantages of modulation techniques have already been explored. TDM and FDM allow several data streams to pass through the channel between transmitter and receiver at the same time. We can figure out what they are based on their names. For example, each GSM channel has a bandwidth of 200 KHz. Furthermore, a single channel can connect up to eight users at the same time.
 

1. FDMA:


Frequency division multiplexing access (FDMA) is an acronym for frequency division multiplexing. The entire available bandwidth is subdivided into several sections using this strategy. Each sub band is assigned to a certain device. It's also feasible to apply TDMA on each of the sub bands separately.
 

2. TDMA: [↗]


Time division multiplexing access (TDMA) is an acronym for time division multiplexing. TDMA is a modulation technology that allows us to connect many devices to a base station or access point by providing them distinct time slots. We use a rotator in TDMA to establish distinct time slots, and then we use TDMA to link multiple devices. For example, each 2G GSM channel has a bandwidth of 200 KHz, and we connect eight users using TDMA or various time slots.
 

3. CDMA:[↗]

Code division multiplexing access (CDMA) is the abbreviation for code division multiplexing access. 3G technology was the first to use this strategy. Different forms of coding are used in code division multiplexing access. So, the term "CDMA" can refer to a variety of communication protocols. The fundamental idea is to give each mobile phone a special code. These codes are all mutually orthogonal to one another. For example, a base station (BS) emits a code, which many devices attempt to decode. The signal will only be received by the intended user; it will be discarded by others. Simply put, we can say that there is a conference room and that there are numerous individuals speaking different languages in it. Now that one of the speakers is speaking Chinese, only those who are familiar with the language will be able to understand. A person who does not speak Chinese will be unable to comprehend a single word. The same thing happens when users or linked devices have access to code division multiplexing.

Each user in this scenario has access to the full frequency band and is free to transmit at any moment. In comparison to FDMA and TDMA, CDMA is hence more flexible. Other CDMA plans make advantage of system resources to provide multiple channels.

Spread spectrum techniques include the frequency-hopping CDMA technology. Pseudorandom (PN) codes assigned to each user are used to modulate the signal that will be broadcast. This is comparable to FDMA because each user will be transmitting at a separate frequency as a result. As the PN code evolves, the user will eventually be broadcasting over a different carrier frequency for each time slot, which is akin to TDMA.
[Click here to read about CDMA in details]

4. Comparison of TDMA & FDMA:


1.In FDM, you can transmit and receive in different bands at the same time.


2.In TDM, transmission and reception take place on the same frequency range, but at different times.


3.For FDM, guard frequency bands are necessary, resulting in system overhead.


4.Spectral inefficiency is required for TDM guard time slots.


5.TDM outperforms FDM in terms of noise resistance.




We can conclude from the three multiplexing techniques mentioned above that we can send multiple data streams utilizing those multiplexing techniques over a single signal path / route. It is also clear that while using the same transmission line, desired users can access independent signals.


5. Advantages of CDMA Technique over FDMA and TDMA

The use of a CDMA system has some key benefits. There may be excessive multipath propagation when signals are sent across a random medium. This phenomenon results in small-scale fading. A frequency selective channel is one sort of fading channel that attenuates some frequencies more than others. Because of this, received signal strength inside this kind of channel can fluctuate significantly. 

A user in a poor frequency band will only use that band for a brief amount of time in an FH-CDMA scheme. Therefore, CDMA systems can aid in combating fading channels. It is a benefit of a CDMA

Another advantage to a CDMA code is the privacy that it can afford a user. Any receiver can pick up the same signal that a user is transmitting and receiving when the user has a stable frequency band.


Read more about

[1] Click here to read about CDMA in details

[2] CDMA Simulator

People are good at skipping over material they already know!

View Related Topics to







Contact Us

Name

Email *

Message *

Popular Posts

BER vs SNR for M-ary QAM, M-ary PSK, QPSK, BPSK, ...

📘 Overview of BER and SNR 🧮 Online Simulator for BER calculation of m-ary QAM and m-ary PSK 🧮 MATLAB Code for BER calculation of M-ary QAM, M-ary PSK, QPSK, BPSK, ... 📚 Further Reading 📂 View Other Topics on M-ary QAM, M-ary PSK, QPSK ... 🧮 Online Simulator for Constellation Diagram of m-ary QAM 🧮 Online Simulator for Constellation Diagram of m-ary PSK 🧮 MATLAB Code for BER calculation of ASK, FSK, and PSK 🧮 MATLAB Code for BER calculation of Alamouti Scheme 🧮 Different approaches to calculate BER vs SNR What is Bit Error Rate (BER)? The abbreviation BER stands for Bit Error Rate, which indicates how many corrupted bits are received (after the demodulation process) compared to the total number of bits sent in a communication process. BER = (number of bits received in error) / (total number of tran...
Read more

Online Simulator for ASK, FSK, and PSK

Try our new Digital Signal Processing Simulator!   Start Simulator for binary ASK Modulation Message Bits (e.g. 1,0,1,0) Carrier Frequency (Hz) Sampling Frequency (Hz) Run Simulation Simulator for binary FSK Modulation Input Bits (e.g. 1,0,1,0) Freq for '1' (Hz) Freq for '0' (Hz) Sampling Rate (Hz) Visualize FSK Signal Simulator for BPSK Modulation ...
Read more

Constellation Diagrams of ASK, PSK, and FSK

📘 Overview of Energy per Bit (Eb / N0) 🧮 Online Simulator for constellation diagrams of ASK, FSK, and PSK 🧮 Theory behind Constellation Diagrams of ASK, FSK, and PSK 🧮 MATLAB Codes for Constellation Diagrams of ASK, FSK, and PSK 📚 Further Reading 📂 Other Topics on Constellation Diagrams of ASK, PSK, and FSK ... 🧮 Simulator for constellation diagrams of m-ary PSK 🧮 Simulator for constellation diagrams of m-ary QAM BASK (Binary ASK) Modulation: Transmits one of two signals: 0 or -√Eb, where Eb​ is the energy per bit. These signals represent binary 0 and 1.    BFSK (Binary FSK) Modulation: Transmits one of two signals: +√Eb​ ( On the y-axis, the phase shift of 90 degrees with respect to the x-axis, which is also termed phase offset ) or √Eb (on x-axis), where Eb​ is the energy per bit. These signals represent binary 0 and 1.  BPSK (Binary PSK) Modulation: Transmits one of two signals...
Read more

What is - 3dB Frequency Response? Applications ...

📘 Overview & Theory 📘 Application of -3dB Frequency Response 🧮 MATLAB Codes 🧮 Online Digital Filter Simulator 📚 Further Reading Filters What is -3dB Frequency Response?   Remember, for most passband filters, the magnitude response typically remains close to the peak value within the passband, varying by no more than 3 dB. This is a standard characteristic in filter design. The term '-3dB frequency response' indicates that power has decreased to 50% of its maximum or that signal voltage has reduced to 0.707 of its peak value. Specifically, The -3dB comes from either 10 Log (0.5) {in the case of power} or 20 Log (0.707) {in the case of amplitude} . Viewing the signal in the frequency domain is helpful. In electronic amplifiers, the -3 dB limit is commonly used to define the passband. It shows whether the signal remains approximately flat across the passband. For example, in pulse shapi...
Read more

BER performance of QPSK with BPSK, 4-QAM, 16-QAM, 64-QAM, 256-QAM, etc

📘 Overview 📚 QPSK vs BPSK and QAM: A Comparison of Modulation Schemes in Wireless Communication 📚 Real-World Example 🧮 MATLAB Code 📚 Further Reading   QPSK provides twice the data rate compared to BPSK. However, the bit error rate (BER) is approximately the same as BPSK at low SNR values when gray coding is used. On the other hand, QPSK exhibits similar spectral efficiency to 4-QAM and 16-QAM under low SNR conditions. In very noisy channels, QPSK can sometimes achieve better spectral efficiency than 4-QAM or 16-QAM. In practical wireless communication scenarios, QPSK is commonly used along with QAM techniques, especially where adaptive modulation is applied. Modulation Bits/Symbol Points in Constellation Usage Notes BPSK 1 2 Very robust, used in weak signals QPSK 2 4 Balanced speed & reliability 4-QAM ...
Read more

Channel Impulse Response (CIR)

📘 Overview & Theory 📘 How CIR Affects the Signal 🧮 Online Channel Impulse Response Simulator 🧮 MATLAB Codes 📚 Further Reading What is the Channel Impulse Response (CIR)? The Channel Impulse Response (CIR) is a concept primarily used in the field of telecommunications and signal processing. It provides information about how a communication channel responds to an impulse signal. It describes the behavior of a communication channel in response to an impulse signal. In signal processing, an impulse signal has zero amplitude at all other times and amplitude ∞ at time 0 for the signal. Using a Dirac Delta function, we can approximate this. Fig: Dirac Delta Function The result of this calculation is that all frequencies are responded to equally by δ(t) . This is crucial since we never know which frequenci...
Read more

Theoretical BER vs SNR for binary ASK, FSK, and PSK

📘 Overview & Theory 🧮 MATLAB Codes 📚 Further Reading Theoretical BER vs SNR for Amplitude Shift Keying (ASK) The theoretical Bit Error Rate (BER) for binary ASK depends on how binary bits are mapped to signal amplitudes. For typical cases: If bits are mapped to 1 and -1, the BER is: BER = Q(√(2 × SNR)) If bits are mapped to 0 and 1, the BER becomes: BER = Q(√(SNR / 2)) Where: Q(x) is the Q-function: Q(x) = 0.5 × erfc(x / √2) SNR : Signal-to-Noise Ratio N₀ : Noise Power Spectral Density Understanding the Q-Function and BER for ASK Bit '0' transmits noise only Bit '1' transmits signal (1 + noise) Receiver decision threshold is 0.5 BER is given by: P b = Q(0.5 / σ) , where σ = √(N₀ / 2) Using SNR = (0.5)² / N₀, we get: BER = Q(√(SNR / 2)) Theoretical BER vs ...
Read more

Coherence Bandwidth and Coherence Time

🧮 Coherence Bandwidth 🧮 Coherence Time 🧮 MATLAB Code s 📚 Further Reading For Doppler Delay or Multi-path Delay Coherence time T coh ∝ 1 / v max (For slow fading, coherence time T coh is greater than the signaling interval.) Coherence bandwidth W coh ∝ 1 / Ï„ max (For frequency-flat fading, coherence bandwidth W coh is greater than the signaling bandwidth.) Where: T coh = coherence time W coh = coherence bandwidth v max = maximum Doppler frequency (or maximum Doppler shift) Ï„ max = maximum excess delay (maximum time delay spread) Notes: The notation v max −1 and Ï„ max −1 indicate inverse proportionality. Doppler spread refers to the range of frequency shifts caused by relative motion, determining T coh . Delay spread (or multipath delay spread) determines W coh . Frequency-flat fading occurs when W coh is greater than the signaling bandwidth. Coherence Bandwidth Coherence bandwidth is...
Read more