Networking Essentials: CDMA, Error Handling, and Transmission

Posted on Mar 25, 2025 in Computer Engineering

Networking Essentials

CDMA (Code Division Multiple Access)

Q. Working of CDMA

Ans. Code Division Multiple Access (CDMA) works by assigning a unique code to each user. Here’s how it works:

  1. Data Encoding: Each user’s data is multiplied by a unique spreading code, spreading the signal across a wider frequency band.
  2. Transmission: Multiple users transmit their encoded data over the same frequency band at the same time.
  3. Reception: The receiver uses the corresponding unique code to decode the signal, separating it from other users’ data.
  4. Signal Separation: The receiver can isolate each user’s data due to the unique codes, allowing simultaneous communication without interference.

Error Detection and Correction

Q. Error detection and corrections

Ans. Error detection identifies errors in transmitted or stored data, while error correction not only detects but also fixes those errors.

Error Detection Methods:

  1. Parity Bit: Adds a bit to make the number of 1s either even or odd.
  2. Checksums: Calculates a value based on data and verifies integrity.
  3. Cyclic Redundancy Check (CRC): Uses polynomial division to detect errors.

Error Correction Methods:

  1. Hamming Code: Detects and corrects single-bit errors.
  2. Reed-Solomon Codes: Corrects multiple errors, used in CDs/DVDs.
  3. Turbo and LDPC Codes: Advanced methods for efficient error correction in modern systems.

Analog vs. Digital Signals

Q. Differentiate between analog signals and digital signals?

Ans.

  1. Analog Signals: Continuous signals change smoothly over time.
  2. Digital Signals: Discrete signals that represent data in binary (0s and 1s).
  3. Analog Signals: Represented by continuous waves.
  4. Digital Signals: Represented by square waves (discrete steps).
  5. Analog Signals: Can take any value within a range.
  6. Digital Signals: Have a finite number of values (typically two: 0 and 1).
  7. Analog Signals: Can suffer from noise and distortion, affecting accuracy.
  8. Digital Signals: Less prone to noise and distortion, making them more accurate.
  9. Analog Signals: Can degrade over long distances.
  10. Digital Signals: Can be transmitted over longer distances with less degradation, often using error correction.
  11. Analog Signals: Require a continuous bandwidth.
  12. Digital Signals: Typically require higher bandwidth for high-quality transmission.
  13. Analog Signals: Difficult to process and manipulate.
  14. Digital Signals: Easier to process, store, and manipulate using digital devices.
  15. Analog Signals: Used in older radio, audio, and video systems.
  16. Digital Signals: Used in modern computing, telecommunication, and data storage.
  17. Analog Signals: Less efficient in terms of data transmission and storage.
  18. Digital Signals: More efficient for data compression, encryption, and transmission.

Switching in Networks

Q. Define switching

Ans. Switching in telecommunications and networking refers to the process of directing data or communication signals from one point to another through a network. It involves connecting devices or circuits to establish a communication path between them.

  1. Circuit Switching: A dedicated communication path is established between the sender and receiver for the duration of the communication.
  2. Packet Switching: Data is divided into small packets and transmitted independently across the network. Each packet can take different paths to reach the destination, where they are reassembled. This method is used in the internet and modern data networks.
  3. Message Switching: Entire messages are routed from sender to receiver, but the message may be stored temporarily at intermediate points.

Parallel Transmission

Q. Define parallel transmission

Ans. Parallel transmission is a method of data transmission where multiple bits are sent simultaneously over multiple channels or wires. In this approach, each bit of a data word is transmitted over a separate wire, allowing for faster data transfer compared to serial transmission, where bits are sent one at a time.

Parallel transmission is typically used for short-distance communication, such as inside computer systems (e.g., between the CPU and memory or within a computer’s internal components). However, it is more susceptible to signal degradation and timing issues over long distances, which makes it less efficient for long-range communication.

Serial Transmission

Q. Define serial transmission

Ans. Serial transmission is a method of data transmission where data is sent one bit at a time, sequentially, over a single communication channel or wire. This contrasts with parallel transmission, where multiple bits are sent simultaneously over multiple channels.

Serial transmission is commonly used in communication systems, including USB, RS-232, and Ethernet, due to its simplicity, lower cost, and ability to transmit data over long distances with less signal degradation. It can be further categorized into synchronous (data sent in sync with a clock signal) and asynchronous (data sent without a clock signal, relying on start and stop bits).

Twisted Pair Cable

Q. Define twisted pair cable

Ans. A twisted pair cable is a type of electrical wiring commonly used in telecommunications and computer networks. It consists of pairs of insulated copper wires twisted together to reduce electromagnetic interference (EMI) from external sources. There are two main types of twisted pair cables:

  1. Unshielded Twisted Pair (UTP): This type does not have any additional shielding around the twisted pairs and is commonly used for general networking, such as Ethernet.
  2. Shielded Twisted Pair (STP): This type includes additional shielding around the twisted pairs to further reduce interference, often used in environments with high electromagnetic interference.

Signal Bit Error and Burst Error

Q. Define signal bit error and burst error

Ans.

Signal Bit Error: A signal bit error happens when a single bit of data is corrupted during transmission. This occurs due to noise or interference in the transmission medium, causing the received bit to differ from the transmitted bit (e.g., a bit being changed from 0 to 1 or 1 to 0).

Burst Error: A burst error occurs when a sequence of consecutive bits is corrupted during transmission. The errors are clustered together, affecting multiple bits in a specific period, often caused by brief but intense interference or noise in the communication channel. This type of error affects a range of bits rather than just one.

Process-to-Process Communication

Q. Process to process communication

Ans. Process-to-process communication is the exchange of data between two processes, typically running on different machines or within the same system, using transport layer protocols like TCP or UDP. It involves the following steps:

  1. Application Layer: The application initiates communication by sending data.
  2. Transport Layer: Data is divided into segments and assigned a port number to identify the destination process.
  3. Network Layer: Adds the destination IP address for routing the data to the correct machine.
  4. Data Link Layer: Prepares data with physical addressing (MAC address) for transmission over the network.
  5. Physical Layer: Data is transmitted as signals (electrical, radio, or optical).

On the receiving end, the reverse process happens to ensure the correct data reaches the intended application.

Hubs and Routers

Q. Write the terms 1. Hub 2. Router

A.

  1. Hub: A hub is a basic networking device that connects multiple computers or devices in a local area network (LAN). It operates at the data link layer (Layer 2) of the OSI model and simply forwards data packets to all connected devices, regardless of the destination address. This can lead to network congestion as all devices receive the same data, even if it’s not meant for them.
  2. Router: A router is a networking device that connects multiple networks, such as a local area network (LAN) to a wide area network (WAN), like the internet. It operates at the network layer (Layer 3) of the OSI model and routes data packets between devices or networks based on their IP addresses. Routers can also provide features like network address translation (NAT), firewall protection, and Wi-Fi connectivity.

Coaxial Cable

Q. Define coaxial cable

Ans. A coaxial cable is a type of electrical cable commonly used for transmitting data, video, and audio signals. It consists of a central conductor (usually copper or aluminum) surrounded by an insulating layer, which is then covered by a metallic shield (typically braided or solid metal) to protect against interference. The outer layer is often covered with a plastic insulating material. The structure of coaxial cable helps in minimizing signal loss and external electromagnetic interference, making it suitable for various applications such as cable television, internet, and telecommunications.