Week 3= TM

Introduction to Wireless Communication

Welcome to the lecture session on wireless data transmission, which corresponds to chapter two of the prescribed book "Guide to Wireless Communication." Today, we will cover the following topics:

• Types of wireless data communication, focusing primarily on radio communication.

• Key properties including amplitude, wavelength, frequency, and phase.

• Concepts and techniques related to radio wave data transmission.

• Overview of spread spectrum transmission.

Types of Wireless Communication

Radio Communication

Radio communication is the primary mode of wireless data transmission used in various applications such as mobile phones, which function using cellular towers and other communication infrastructures.

Infrared Communication

Another form of wireless communication is infrared transmission, which is less commonly used in comparison to radio waves. Although infrared signals are not susceptible to interference from other radio-frequency devices, their range and mobility are limited.

Properties of Wireless Communication

To understand wireless media, one must grasp the properties of radio waves and electromagnetic waves, which are the underlying carriers of signals.

• Electromagnetic Waves (EM Waves): These high-frequency waves travel through space at the speed of light (approximately 300,000 km/s) and are crucial for wireless communication.

• Types of Waves: Two main types of EM waves employed in data transmission are infrared light and radio waves.

• Spectrum of EM Waves: The electromagnetic spectrum is categorized based on frequency or wavelength, ranging from radio waves to gamma rays.

Key Concepts and Techniques

Signal Properties

• Amplitude: Refers to the height of the waveform, essential in determining signal strength and clarity.

• Frequency: Measured in hertz, indicating the number of cycles per second.

• Wavelength: The physical distance between two consecutive points of a wave, which is inversely related to frequency.

Modulation Techniques

1. Amplitude Modulation (AM): Changes the height of the carrier wave based on the signal’s amplitude. Commonly used in AM radio broadcasting, AM is prone to interference.

2. Frequency Modulation (FM): Changes the frequency of the wave in response to the signal’s characteristics. FM is less susceptible to interference and is utilized in music quality radio broadcasting.

3. Phase Modulation: Alters the starting point of the wave cycle, mostly used in digital communication.

4. Quadrature Amplitude Modulation (QAM): Combines both amplitude and frequency modulation to enhance data rates and transmission efficiency.

Digital and Analog Data Transmission

Data transmitted over wireless media can be classified into:

• Analog Data: Continuous waveforms that vary smoothly over time.

• Digital Data: Discrete signals represented as sequences of zeros and ones, which provide advantages like better bandwidth usage and reduced power consumption.

Spread Spectrum Techniques

Frequency Hopping Spread Spectrum (FHSS)

This technique uses multiple frequencies for transmission, where the transmitter hops between frequencies according to a predetermined sequence, making it more resilient to interference.

Direct Sequence Spread Spectrum (DSSS)

In this method, each bit of data is encoded into a longer bit sequence using a redundant code, allowing for more robust communication against interference.

Multiplexing Techniques

Frequency Division Multiplexing (FDM)

FDM is utilized to increase the data transmission capacity without raising the transmission speed. By dividing a single communication channel into several distinct channels, data can be transmitted simultaneously.

Summary and Conclusion

The use of radio waves for data transmission is prevalent in modern communication systems, driven by modulation techniques and spread spectrum methods to ensure reliability and efficiency. As we transition to advanced communication technologies such as 5G networks, understanding these foundational concepts will be critical.

Future Lessons

Looking ahead, our next lecture will cover chapter three, and a quiz based on chapters one to three will be scheduled for week five. Ensure to review the material thoroughly and engage with any extra resources provided on Canvas.