Radio Waves vs. Light Waves: WiFi and LiFi Differences

This page compares radio frequency waves and light waves, highlighting the key differences. WiFi utilizes radio signal waves (EM waves), while LiFi relies on light signals.

Introduction

The electromagnetic spectrum is divided into eight sections based on radiation intensity and their wavelengths. There are two major divisions: the radio frequency (RF) spectrum and the optical spectrum. The radio spectrum includes radio waves, microwaves, and terahertz (THz) waves. The optical spectrum includes infrared, visible light, ultraviolet light, X-rays, and gamma radiation.

What are Radio Frequency Waves?

Radio frequency waves are EM signals that occupy the range of 3 KHz to 300 GHz. These waves have much lower frequencies compared to microwave frequencies. The radio waves transmitted by antennas have wavelengths ranging from about 1 mm to 100 meters.

They are used for various applications such as:

• Cellular communication
• Radio and TV broadcasting
• Satellite communication
• WLAN (i.e., WiFi)
• Zigbee

The unit of radio frequency signal is Hertz (Hz), which represents the number of oscillations or cycles per second. The relationship between wavelength and frequency is:

Wavelength (λ) = C / Frequency

Where C is the speed of light, approximately 3 x 10^8 meters/second.

Here’s a typical system used for radio transmission and reception:

The transmitter and receiver parts consist of the following components. Before radio frequency waves are transmitted by the antenna, they undergo modulation, up-conversion, and power amplification according to system requirements.

Similarly, radio waves are processed after being received by the antenna. They pass through various modules such as LNA (Low Noise Amplifier), down-conversion, and demodulation.

What are Light Waves?

Light waves are EM waves that occupy the frequency range of 430 THz to 790 THz. They have wavelengths ranging from 380 nm to 750 nm.

LEDs, lasers, or fluorescent bulbs are used as transmitters of light waves, while photodiode detectors are used as receivers. For more information, refer to a LiFi tutorial. Data bits are modulated onto light waves before transmission.

Difference Between Radio Waves and Light Waves

The following points summarize the major differences between radio frequency waves and light waves:

• Radio waves are affected by other EM sources, while light waves are generally not.
• Radio waves typically consume more power than light waves.
• Radio waves offer lower bandwidth compared to the high bandwidth offered by light waves.
• Radio waves do not require a direct line of sight between the transmitter and receiver, while light waves often do.
• Radio waves can be harmful at high power levels, whereas light waves are generally not harmful in typical usage.
• Radio waves are often amplified before transmission, while light waves may not require amplification.
• Radio waves can cover medium to larger distances, while light waves typically cover shorter distances.
• Radio waves are not visible, while light waves are visible.

Difference Between WiFi and LiFi

The following table summarizes the major comparison between WiFi and LiFi technologies based on various specifications.