Communication Systems Overview

Simple Communication System

• A communication system involves a transmitter, channel, and receiver.
• Data travels across a medium from a source to a destination.
• The fundamental purpose of a communication system is the exchange of data between two points.

Communications Model

• Data communication examines how data travels in the form of energy from a source to a destination through some form of medium.
• Source system, transmitter, transmission system, receiver, and destination system are the components of communication.

Communications Model [2/6]

• In a simplified communication system, the source plays a crucial role in transmitting information to the destination.
• The system involves both physical and logical components.

Communications Model [3/6]

• The source system transforms/encodes the signal from the source.
• The source generates data to be transmitted.
• The transmitter converts data into transmittable signals.

Communications Model [4/6]

• The transmission system allows the transport of signal from one point to another, e.g., copper cables, fiber optics, radio waves, or a combination of these.

Communications Model [5/6]

• The destination system decodes the received signal for handling by the destination device.
• The receiver converts the received signal into data.
• The destination takes incoming data.

Communications Model [6/6]

• The figure shows communication between a workstation and a server over a public telephone network, and another example is the exchange of voice signals between two telephones over the same network.

Next Lecture

• The lecture will discuss what allows different applications' existence without interruption.
• Several related applications and smart technologies are mentioned, e.g. Smart Parking, Smart Health, Waste Management, etc.

Frequency Allocation and Spectrum Licensing

• The Federal Communications Commission (FCC) manages and licenses the radio spectrum in the US.
• The FCC allocates specific bands for different applications like Wi-Fi, cellular networks, emergency services, and broadcasting to prevent interference.
• The International Telecommunication Union (ITU) plays a global role in spectrum management.
• The ITU divides the world into three regions and allocates spectrum differently in each region.

Frequency Allocation and Spectrum Licensing (Why it Matters)

• Preventing interference between services by allocating specific bands for each service type.
• Supporting diverse applications, e.g., emergency services, broadcasting, and satellite communication.
• Efficient use of limited spectrum by allocating bands carefully to allow multiple services to coexist without degrading their quality.

Data (Signal) Transmission [1/4]

• Successful data transmission depends on the quality of the transmitted signal and the characteristics of the transmission medium.
• Data transmission occurs between a transmitter and a receiver over a transmission medium.

Data Transmission [2/4]

• Wired: Physical media, no antennas, electrical/optical signals, less complex, high speed, good security, difficult installation, less interference and noise, not supported mobility.
• Wireless: No physical antenna, electromagnetic waves, more complex, low speed, weak security, easy installation, high interference and noise, supported mobility.

Data Transmission [3/4]

• Direct link refers to a transmission path between two devices without intermediate devices.
• Guided transmission medium is point-to-point if it directly connects two devices.
• In multipoint configuration, more than two devices share the same medium.

Data Transmission [4/4]

• Transmission can be simplex (one direction), half-duplex (one at a time), or full-duplex (simultaneous).

Operations on Signal

• Includes operations relating to signals.

Analog and Digital Data Transmission

• Analog and digital correspond to continuous and discrete, respectively.
• Analog and digital concepts apply to data, signals, and transmission.
• Data carries information, while signals are electric or electromagnetic representations of data.
• Signaling is the physical propagation of the signal, while transmission involves communication of data via propagation and signal processing.

Analog and Digital Data

• Analog data takes on continuous values, while digital data takes discrete values.
• Audio is an example of analog data, while text or character strings are examples of digital data.

Analog and Digital Signals

• Data are propagated in communications systems using electric or electromagnetic signals.
• An analog signal is a continuously varying electromagnetic wave propagated over various media.
• A digital signal is a sequence of voltage pulses that can be transmitted over a wire medium.
• Digital signaling is generally cheaper and less susceptible to interference than analog signaling, but digital signals suffer more from attenuation.

Data and Signals [1/4]

• Analog signals represent analog data, while digital signals represent digital data.
• Analog data are functions of time and occupy a limited frequency spectrum.
• Digital data can be represented by digital signals with different voltage levels for each binary digit.

Data and Signals [2/4]

• Digital data can be converted to analog signals using a modem (modulator/demodulator).
• Modems convert binary voltage pulses into an analog signal by encoding digital data onto a carrier frequency.

Data and Signals [3/4]

• The resulting signal occupies a certain spectrum, which is centered around the carrier frequency.
• Modems allow digital data transmission over ordinary voice-grade lines, requiring another modem for decoding at the recipient end.

Data and Signals [4/4]

• Analog data can be represented by digital signals using a codec (coder-decoder).
• The codec takes an analog signal and converts it into a bit stream that represents the voice data.
• The bit stream is used to reconstruct the analog data at the receiver.

Transmission Impairments

• Received signals may differ from transmitted ones due to degradation in signal quality (analog) or bit errors (digital).
• Attenuation, delay distortion, and noise are major impairments.

Attenuation

• Signal strength weakens with distance over communication mediums.
• Signal strength varies with frequency, with higher frequencies needing stronger signals.
• Received signals must be strong enough for detection and stronger than noise.
• Repeaters or amplifiers increase signal strength to overcome attenuation.

Delay Distortion

• Delay distortion is a phenomenon in transmission cables (e.g., twisted pair, coaxial cable, optical fiber), and satellite communication.

Noise

• Unwanted signals inserted between transmission and reception are noise.
• Noise is a major limiting factor in communication system performance.
• Crosstalk is a type of noise where a signal from one line interferes with another.

Test your understanding of fundamental concepts in communication systems. This quiz explores the roles of various components, types of transmission media, and important principles like frequency allocation. Perfect for students eager to grasp the basics of data transmission and media types.