📢 Join our SPPU IT WhatsApp Community!
Study Material
Semester-03
BCN
Unit-01

Unit 1: Data Communication and Network Models

Introduction to Communication Theory

Basics of Data Communication

Data communication refers to the exchange of information between devices using some form of transmission media. The primary purpose of data communication is to send data from one device to another efficiently and reliably. A data communication system includes five essential components:

  • Sender: The device that sends the data.
  • Receiver: The device that receives the data.
  • Message: The data being communicated.
  • Transmission Medium: The physical or logical path through which the message travels (e.g., cables, wireless signals).
  • Protocol: A set of rules governing data exchange.

Types of Signals

Signals are used to represent data in data communication. There are two primary types:

  1. Analog Signals: Continuous signals that vary over time (e.g., sound waves, AM radio signals).
  2. Digital Signals: Discrete signals represented by binary values (0s and 1s), often used in modern computer systems.

Analog to Digital (A/D), Digital to Analog (D/A), Analog to Analog (A/A), Digital to Digital (D/D) Signal Conversion Methods

Signal conversion is essential for communication between different systems. The common methods are:

  • Analog to Digital (A/D) Conversion: Converts analog signals into digital data (e.g., pulse code modulation used in telephony).
  • Digital to Analog (D/A) Conversion: Converts digital signals into analog forms (e.g., modem converting binary data into sound waves).
  • Analog to Analog (A/A) Conversion: Modulation techniques like AM and FM, used in radio transmission.
  • Digital to Digital (D/D) Conversion: Line coding schemes like Manchester encoding, where binary data is transformed for more efficient transmission.

Bandwidth Utilization and Data Rate Limits

Bandwidth refers to the range of frequencies available for data transmission. Higher bandwidth enables more data to be transmitted. However, various factors like noise and signal strength can limit the maximum achievable data rate. Two essential theorems govern this:

  1. Nyquist Theorem: Determines the maximum data rate for noiseless channels. For a noiseless channel, the maximum data rate is given by:

  2. Shannon-Hartley Theorem: Defines the maximum data rate for a channel in the presence of noise. The channel capacity (C) in bits per second is determined as:

Noise, Types of Noise, and Noise Impact on Data Transmission

Noise refers to unwanted signals that interfere with communication. There are several types of noise:

  • Thermal Noise: Caused by the random motion of electrons.
  • Intermodulation Noise: Caused by mixing of signals.
  • Crosstalk: Occurs when a signal from one circuit affects another.
  • Impulse Noise: Sudden bursts of irregular noise caused by electrical interferences.

Noise can cause signal degradation, leading to errors in data transmission.

Shannon-Hartley Theorem, Channel Capacity, Nyquist Theorem, and Bandwidth S/N Trade-off

Channel capacity measures the maximum rate of data transmission over a communication channel. The Shannon-Hartley theorem and Nyquist theorem are the two key theorems that define limits based on noise and bandwidth. As the signal-to-noise (S/N) ratio improves, more bandwidth can be utilized effectively, increasing data transmission rates.

Multiplexing Techniques and Topologies

Multiplexing Techniques

Multiplexing is the process of combining multiple signals over a single communication medium. The primary types of multiplexing are:

  • Time Division Multiplexing (TDM): Divides time into intervals and assigns each signal a specific time slot.
  • Frequency Division Multiplexing (FDM): Divides the available bandwidth into different frequency bands, assigning each signal its band.
  • Wavelength Division Multiplexing (WDM): Used in fiber-optic communication where signals are transmitted at different light wavelengths.

Common Network Topologies

Network topology refers to the arrangement of different components in a communication system. Common types include:

  1. Bus Topology: All devices are connected to a single communication line (bus). Suitable for small networks.
  2. Star Topology: Each device is connected to a central hub or switch. If the hub fails, the whole network goes down.
  3. Ring Topology: Devices are connected in a circular manner. Data passes through each device in one direction.
  4. Mesh Topology: Every device is connected to every other device. Provides redundancy and reliability but is expensive to implement.

Network Models and Addressing

OSI Model

The Open Systems Interconnection (OSI) model is a conceptual framework used to understand network communication. It has seven layers:

  1. Physical Layer: Deals with the transmission of raw bits over a communication medium (e.g., cables, wireless signals).
  2. Data Link Layer: Handles error detection and correction, as well as media access control (e.g., MAC addresses).
  3. Network Layer: Manages routing of data between devices in different networks (e.g., IP addresses).
  4. Transport Layer: Ensures end-to-end communication, managing flow control, error checking, and retransmission (e.g., TCP, UDP).
  5. Session Layer: Establishes, maintains, and terminates communication sessions.
  6. Presentation Layer: Responsible for data translation, encryption, and compression.
  7. Application Layer: Interfaces with the user, providing services like email, file transfer, and web browsing (e.g., HTTP, FTP).

TCP/IP Model

The TCP/IP model is more commonly used in real-world networking. It has four layers:

  1. Network Interface Layer: Corresponds to the OSI physical and data link layers.
  2. Internet Layer: Corresponds to the OSI network layer and manages IP addresses and routing.
  3. Transport Layer: Corresponds to the OSI transport layer and uses protocols like TCP and UDP.
  4. Application Layer: Corresponds to the OSI session, presentation, and application layers, handling communication protocols like HTTP, FTP, and SMTP.

Data Format and Addressing Mechanisms

In network communication, data is transmitted in the form of packets, which consist of headers (containing control information like source and destination addresses) and payloads (the actual data being transmitted). Addressing mechanisms include:

  • MAC Addresses: A unique identifier for network devices used at the data link layer.
  • IP Addresses: Used for identifying devices in a network and routing packets across networks. Divided into IPv4 (32-bit) and IPv6 (128-bit) formats.
  • Port Numbers: Identify specific applications or services within a device. For example, port 80 is used for HTTP.

Devices Used in Network Communication

Common network devices include:

  • Hubs: Broadcast incoming data to all connected devices.
  • Switches: More intelligent than hubs, switches send data only to the intended recipient.
  • Routers: Connect different networks and manage IP address-based packet routing.
  • Modems: Convert digital data into analog signals for transmission over telephone lines.

Conclusion

Understanding data communication and network models is essential for designing efficient networks. From the basics of signal conversion and bandwidth to the nuances of addressing and network topologies, these concepts form the backbone of modern communication systems. By mastering these topics, one can better understand how data is transmitted, routed, and processed across global networks.

ResourcesUnit-02