24.2 Communication systems and networks

Communication systems and networks are the backbone of our connected world. From wireless 5G to fiber optics, these technologies enable data transmission across vast distances. They use advanced techniques like modulation and multiplexing to send information efficiently and securely.

This topic explores various communication methods, including satellite, wired, and wireless networks. It also covers protocols, error correction, and security measures that ensure reliable data transfer. Understanding these systems is crucial for developing modern communication infrastructure.

Wireless Communication Networks

5G Networks and Wireless Sensor Networks

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• 5G networks provide high-speed, low-latency wireless communication
  • Enables applications such as autonomous vehicles, virtual reality, and Internet of Things (IoT)
  • Uses advanced technologies like massive MIMO, beamforming, and millimeter-wave spectrum
  • Offers improved network capacity, reliability, and energy efficiency compared to previous generations (4G, 3G)
• Wireless sensor networks consist of spatially distributed autonomous sensors that monitor physical or environmental conditions
  • Applications include environmental monitoring, industrial process control, and healthcare monitoring
  • Sensors communicate wirelessly to transmit data to a central location for analysis and decision-making
  • Challenges include limited battery life, network scalability, and data security

Satellite Communications

• Satellite communications involve the use of artificial satellites to provide communication links between various points on Earth
  • Enables global communication coverage, including remote and underserved areas
  • Used for applications such as television broadcasting, GPS navigation, and emergency communication
• Satellites are classified based on their orbit: low Earth orbit (LEO), medium Earth orbit (MEO), and geostationary orbit (GEO)
  • LEO satellites are closer to Earth and offer lower latency but require more satellites for continuous coverage
  • GEO satellites are farther from Earth and provide wider coverage but have higher latency
• Challenges in satellite communications include signal attenuation, propagation delay, and interference from weather conditions

Wired Communication Systems

Fiber Optic Communications

• Fiber optic communications use optical fibers to transmit data as light pulses over long distances
  • Offers high bandwidth, low attenuation, and immunity to electromagnetic interference
  • Used in backbone networks, long-haul communications, and fiber-to-the-home (FTTH) applications
• Fiber optic systems consist of a transmitter (laser or LED), optical fiber cable, and a receiver (photodetector)
  • Single-mode fibers have a smaller core diameter and support higher bandwidth over longer distances
  • Multi-mode fibers have a larger core diameter and are used for shorter distances and lower bandwidth applications

Network Protocols and Software-Defined Networking

• Network protocols define the rules and formats for data exchange between devices in a communication network
  • Examples include TCP/IP for internet communication, HTTP for web browsing, and FTP for file transfer
  • Protocols are organized in layers (physical, data link, network, transport, application) to provide a modular approach
• Software-defined networking (SDN) separates the network control plane from the data forwarding plane
  • Enables centralized control and management of network resources through software
  • Provides flexibility, programmability, and easier network configuration compared to traditional networking
  • OpenFlow is a common protocol used in SDN for communication between the control plane and data plane

Data Transmission Techniques

Modulation and Multiplexing

• Modulation is the process of varying one or more properties of a carrier signal to encode information for transmission
  • Digital modulation techniques include amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK)
  • Analog modulation techniques include amplitude modulation (AM) and frequency modulation (FM)
• Multiplexing allows multiple signals or data streams to be combined and transmitted over a single communication channel
  • Time-division multiplexing (TDM) allocates time slots to each data stream in a repeating frame structure
  • Frequency-division multiplexing (FDM) assigns different frequency bands to each data stream
  • Code-division multiple access (CDMA) assigns unique codes to each data stream, allowing simultaneous transmission

Error Correction and Network Security

• Error correction techniques are used to detect and correct errors that may occur during data transmission
  • Forward error correction (FEC) adds redundant data to the transmitted message, enabling the receiver to correct errors without retransmission
  • Automatic repeat request (ARQ) uses acknowledgments and retransmissions to ensure reliable data delivery
• Network security measures protect communication networks from unauthorized access, attacks, and data breaches
  • Encryption techniques, such as symmetric-key and public-key cryptography, protect data confidentiality
  • Firewalls monitor and control incoming and outgoing network traffic based on predetermined security rules
  • Virtual private networks (VPNs) provide secure and encrypted connections over public networks (internet)