Wireless Signals, Radio & Network Protocols Explained
Antennas and Electromagnetic Waves
In many communication systems, it’s not necessary for the sender and receiver to be connected by a physical cable. This wireless communication is achieved using an antenna. Antennas are devices responsible for converting electromagnetic waves into electrical impulses (reception) and vice versa (transmission).
An electrical conductor, such as an antenna, can emit energy as electromagnetic waves if a variable electric current flows through it. These electromagnetic waves propagate through space at the speed of light. They are characterized by their frequency and wavelength.
Wave Characteristics
Key characteristics of electromagnetic waves include:
- Wavelength (λ): The distance a wave travels during one complete cycle.
- Amplitude (A): The maximum displacement or intensity of the wave from its equilibrium position. It relates to the wave’s energy and typically diminishes as it propagates.
- Frequency (f): The number of wave cycles that occur in one second. It is measured in Hertz (Hz).
- Period (T): The time taken for one complete wave cycle. It is the inverse of frequency:
f = 1 / T.
The speed of light (c), a constant, relates wavelength (λ) and frequency (f) through the formula: c = λ × f.
Because c is constant, high-frequency signals possess short wavelengths, whereas low-frequency signals have very long wavelengths.
The Electromagnetic Spectrum
The entire range of electromagnetic waves, arranged by frequency (or alternatively, wavelength), is known as the electromagnetic spectrum.
For context, human-audible sound frequencies range from approximately 20 Hz to 20,000 Hz (20 kHz). Frequencies above this audible range are termed ultrasonic, with applications like medical ultrasound and sonar. Frequencies below the audible range are called infrasound.
A similar concept applies to light, which is part of the electromagnetic spectrum. Below the frequency of red visible light lies infrared (IR) radiation (associated with heat). Above the frequency of violet visible light is ultraviolet (UV) radiation, a significant portion of which is absorbed by the Earth’s ozone layer.
Radio Signal Modulation
Raw radio frequency (RF) signals, if directly used for transmission and received, would often result in unintelligible noise. To effectively transmit information like an audio signal, it is combined with an RF signal. The RF signal then acts as a carrier wave for the message. This process is known as modulation, and the resulting combined signal is called a modulated signal.
Two common types of modulation are:
- Amplitude Modulation (AM): The amplitude of the carrier wave is varied in proportion to the instantaneous amplitude of the audio signal, while the frequency of the carrier remains constant.
- Frequency Modulation (FM): The frequency of the carrier wave is varied in accordance with the instantaneous amplitude of the audio signal, while the amplitude of the carrier wave remains constant.
Radio Signal Reception Process
The stages of radio signal reception include:
- Tuning: The receiver’s antenna is tuned to the specific frequency of the desired radio station. The antenna captures the RF signal and converts it into weak electrical signals.
- RF Amplification: The voltage of these weak electrical signals from the antenna is amplified.
- Demodulation: The original message signal (e.g., audio) is extracted or separated from the carrier wave. This process reverses modulation.
- Audio Amplification: The strength (power) of the demodulated message signal is amplified to a level sufficient to drive a speaker.
- Output: The amplified electrical audio signal is converted by speakers into sound waves that are audible to the human ear.
Understanding TCP/IP Network Protocols
When devices, such as a laptop, communicate over a network, they adhere to a set of rules known as a network protocol.
TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational suite of communication protocols that powers the Internet and many other private networks.
The TCP/IP suite is built around two core protocols:
- TCP (Transmission Control Protocol): This protocol ensures reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts connected to an IP network. It manages data segmentation, acknowledgment of received packets, and retransmission of lost packets.
- IP (Internet Protocol): This protocol is responsible for addressing hosts and routing datagrams (packets) from a source host to a destination host across one or more IP networks.
Beyond TCP and IP, the TCP/IP suite encompasses numerous other protocols that support various functions, such as application-specific communication (e.g., HTTP for web browsing, SMTP for email) and network management tasks.