Frequency Diversity vs Time Diversity: Difference and Comparison

Diversity is a well-known concept in the telecommunication industry. Generally, diversity refers to optimizing the signals by increasing the number of transmission channels.

It is achieved by transmitting multiple copies of the same data.

Moreover, frequency and time diversity are two vital types of diversities to diminish the fading of the communication signal and enhance the signal quality between sender and receiver.

Key Takeaways

  1. Frequency diversity is a communication technique that uses multiple frequencies or frequency bands to transmit signals, improving signal reliability and reducing interference.
  2. Time diversity is a communication technique that transmits signals at different time intervals or with varying delays, enhancing signal reliability and minimizing the effects of fading or interference.
  3. Both frequency and time diversity improve signal reliability in communication systems, but “frequency diversity” uses multiple frequencies, while “time diversity” leverages time intervals or delays.

Frequency Diversity vs Time Diversity

The difference between frequency and time diversity is that frequency diversity means changing the frequency of the same signal or increasing the frequency carriers. On the other hand, time diversity means transmitting the same signal at a different time intervals to avoid fading and disturbance in the signal.

Frequency Diversity vs Time Diversity

The frequency diversity technique is not so old since it was introduced in the 20th century.

During that time, radio signal improvement became necessary to avoid disturbance in signals between sender and receiver.

Therefore, expertise tried to modify the frequency of the same signal to reduce signal fading (amplitude variation).

Sometimes, disturbance or fading in a signal is experienced due to improper time management of the signals.

The technique of time diversity means diverting the time of the same channel. The modified time interval must be higher than the coherence time ( when a problem arose in the data due to time).

Comparison Table

Parameters of ComparisonFrequency DiversityTime Diversity
DefinitionFrequency diversity means diverting the frequency of the data sent.Time diversity means modifying the interval for disturbance-free data.
AmountThe frequency of the signal must be higher than the coherence bandwidth.The time interval of data should be more than the coherence time.
PreferencesSince we need spare bandwidth for the frequency diversity, it is preferred less.One does not need to install spare satellites to use time diversity.
ProcedureCertain frequency is assigned to each sender to transmit, and the receiver coordinates with that frequency level.A signal is divided into different time slots to avoid fading of it.
Example Frequency-hopping spread spectrum is an example of frequency diversity.An example of time diversity is the Rake receiver (a radio-based technique to combat data fading).

What is Frequency Diversity?

Frequency diversity is vital in wireless network systems (telecommunication, Wi-Fi signal, etcetera).

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Frequency diversity, as the name implies, is the process of diverting the frequency level to maintain the quality of networking communications.

The signal travels utilizing two or more carriers’ frequencies in this technique ( measured in Hertz).

It is suitable for line-of-sight propagation and belongs to the micro-density group. Each signal is separated from the other based on frequency to diminish the signal-to-noise ratio.

The level of frequency chosen should be more than that of coherence bandwidth ( a level of frequency at which the channel is flat or constant).

This way, each transmitting signal will experience distinct waves and will not be co-related to one- another.

It aids the receiver in receiving signals from a variety of pathways. Frequency diversity is implemented via N:1 protection switching, according to experts.

One frequency is used to build a frequency diversity scheme through the N number of the carrier frequency. It means one spare bandwidth is required for frequency diversity.

A single antenna is necessary to boost the signal’s intensity through frequency diversity. Moreover, the number of receivers would be similar to the number of channels.

It could be an expensive technique in size and power management.

What is Time Diversity?

Time diversity is also a crucial technique in the networking sector. It means sending the same information but at different time intervals.

In other words, signals are sent out again at specific time slots.

Each of which must be longer than the time at which the signals faded earlier (coherence time). The sender sends the encoded signal with the forward error control coding.

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This technique is called channel coding to minimize errors in signals.

Signal fading, transmitter interference, or sender and receiver obstacles can cause errors (error bursting).

This technique is applied when more errors appear at an interval of time, but the signals are excellent or less faulty at another time interval.

Moreover, little or no hardware exists for error control. Through time diversity, users can recollect information that they missed due to signal errors.

An example is the Rake receiver in CDMA (Code Division Multiple Access).

Rake in English means collecting something. The rake receiver is practically helpful in combating signal error issues. It consists of sub-receivers under CDMA.

When a sender sends data but runs into difficulties, the signals pass through many routes to the rake receiver.

The rake receiver flows the same signals from multiple sub-receivers (fingers) at different time slots. It is how the receiver receives the error-free signal.

Main Differences Between Frequency Diversity and Time Diversity

  1. The term frequency diversity means modifying the frequency of the transmitting signal to avoid distortion. On the other hand, time diversity means changing the time of the transmitted data.
  2. The technique frequency diversity is expensive to remove the error from the signals. However, the time diversity method is cheap because less hardware is required to protect data signals.
  3. The frequency diversity is a less preferable technology as compared to the time diversity method.
  4. Senders are assigned with frequency to transmit the data, and receivers tune with them under the frequency diversity method. On the contrary, signals are divided into separate time intervals during transmission in the time diversity technique.
  5. The practical example of frequency diversity is the frequency hopping spread spectrum. However, in the case of time diversity, it is Rake receiver.
References
  1. https://dl.acm.org/doi/abs/10.1145/2030613.2030642
  2. https://ieeexplore.ieee.org/abstract/document/6513233/

Last Updated : 13 July, 2023

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