Easy Notes Of Data Communication and Computer Network unit-3 @Computer Diploma

Description

3.1 Types of Errors, Forward Error Correction Versus Retransmission

• Types of Errors: Single-bit errors vs. Burst errors.

• FEC vs. Retransmission: Explaining the trade-offs between sending enough redundant information to correct errors directly (FEC) and detecting errors and asking for retransmission (ARQ).

  • Diagram idea: A simple graphic illustrating the path of data, showing where FEC would correct the error and where ARQ would send a NAK and trigger retransmission.

3.2 Framing: Fixed Sized and Variable Sized Framing

• Purpose: How a stream of bits is divided into manageable blocks (frames).

• Fixed Sized Framing: Simple, but less flexible.

• Variable Sized Framing: Character count, character stuffing, bit stuffing (most complex).

  • Diagram idea: A simple illustration contrasting fixed-size blocks with variable-size blocks using flag and stuffing mechanisms.

3.3 Error Detection: Repetition codes, Parity bits, Checksums, CRC

• Repetition codes: Basic concept.

• Parity bits: Even/Odd Parity, simple error detection.

• Checksums: Adding a sequence of data to find the one’s complement sum.

• Cyclic Redundancy Check (CRC): The most powerful method, using polynomial division.

  • Diagram idea: A step-by-step diagram showing the binary division process for a simple CRC calculation.

3.4 Error Correction: Automatic Repeat Request (ARQ), Hamming Code

• ARQ Protocols: Stop-and-Wait, Go-Back-N, Selective Repeat. (Covered briefly in 3.1, but here focusing on the protocols).

  • Diagram idea: A timeline diagram comparing the flow control/efficiency of Stop-and-Wait ARQ vs. Go-Back-N ARQ.

• Hamming Code: The fundamental concept of using redundant bits to locate and correct a single-bit error.

  • Diagram idea: A visualization of a simple Hamming code structure (e.g., Hamming(7,4)) showing how parity bits cover data bits.

3.5 Wireless LAN IEEE 802.11 standard Architecture, Features of IEEE 802.11 versions

• 802.11 Architecture: Basic Service Set (BSS), Extended Service Set (ESS), Distribution System (DS).

  • Diagram idea: A clear structural diagram showing BSS, ESS, AP, and DS connections.

• Features of Versions: A summary table of $a, b, g, n, p$ (frequency, maximum data rate).

3.6 Bluetooth Architecture: Piconet, Scatternet

• Piconet: Master and up to 7 active slaves.

  • Diagram idea: A simple illustration of the star topology of a Piconet.

• Scatternet: Interconnected Piconets.

  • Diagram idea: A diagram showing two or more Piconets linked by a bridge node to form a Scatternet.

3.7 Mobile Generations: 3G, 4G and 5G

• Focus: Key characteristics, defining technologies (e.g., 4G uses OFDM/OFDMA, 5G uses Massive MIMO, mmWave).

• Evolution: How each generation improved speed, latency, and capacity.

  • Diagram idea: A visual timeline or table contrasting the key features, data rates, and latencies of 3G, 4G, and 5G.