ECE422 - Data  Commuications & Computer Networks

Data Communication
Fundamentals -StudyGuide

Master the core concepts of data representation, transmission modes, and network architectures through interactive visualizations and comprehensive theory.

1. Data Representation

How information is encoded for digital transmission

Character Encoding

Characters are represented using standardized binary codes. ASCII uses 7 bits (128 characters) or 8 bits (extended), while Unicode (UTF-8) uses variable-length encoding supporting global languages.

Enter text above to see binary representation...

ASCII Table (Selected)

Number Representation

BIN

Binary

Base-2 system using bits (0,1). Fundamental for digital circuits.

Decimal 13 →
1101₂
= 8+4+0+1
DEC

Decimal

Base-10 system (0-9). Human-readable format.

Binary 1010 →
10₁₀
= 1×2³ + 0×2² + 1×2¹ + 0×2⁰
HEX

Hexadecimal

Base-16 (0-9,A-F). Compact binary representation.

Binary 1111 0000 →
F0₁₆
= 15×16 + 0

Number Base Converter

Image Representation

Images are digitized through rasterization - dividing the image into a grid of pixels. Each pixel's color is encoded using RGB values or bit-depth for grayscale.

Bitmap (BMP) Uncompressed, pixel-by-pixel
Resolution Pixels per dimension (e.g., 1920×1080)
Color Depth Bits per pixel (24-bit RGB = 16M colors)

Pixel Visualization

8×8 Grid (64 pixels) Hover to see RGB values
Pixel data will appear here...

2. Data Flow Modes

Directionality of data transmission between devices

Simplex

One-Way
TX RX Unidirectional
  • Keyboard → Computer
  • TV Broadcast → Receiver
  • Mouse → Computer

Bandwidth: Full channel capacity used for one direction only.

Half-Duplex

Two-Way Alt
A B Alternating Direction
  • Walkie-Talkies
  • Traditional Ethernet (CSMA/CD)
  • USB 1.0/1.1

Key Limitation: Cannot send and receive simultaneously. Requires turn-taking protocol.

Full-Duplex

Simultaneous
A B Bidirectional Simultaneous
  • Telephone Networks
  • Modern Ethernet (Switched)
  • Fiber Optic (WDM)

Implementation: Uses separate channels (frequency/physical) for each direction or echo cancellation.

Technical Comparison

Feature Simplex Half-Duplex Full-Duplex
Direction One-way only Both ways, alternately Both ways simultaneously
Bandwidth Utilization 100% (one direction) 50% per direction 100% per direction
Collision Risk None High (if uncontrolled) None
Cost/Complexity Low Medium High

3. Network Topologies

Physical and logical arrangement of network nodes

Bus Topology

Linear
A B C D
Easy installation, minimal cabling
Single point of failure (backbone)
CSMA/CD for collision handling

Star Topology

Centralized
HUB A B C D
Easy fault isolation, scalable
Hub failure crashes network
Most common in modern LANs

Ring Topology

Circular
A B C D E F
Equal access for all nodes, no collisions
Single failure breaks the ring
Token passing access method

Mesh Topology

Fully Connected
A B C D E F
Highest redundancy, fault-tolerant
Complex wiring, expensive (n(n-1)/2 links)
Used in WANs, critical backbone networks

Topology Link Calculator

2 5 20
Bus/Star/Ring Links: 5
Full Mesh Links: 10
Mesh Complexity: 2.0x
n-1
Links required for Bus/Star topology
Formula: Links = n - 1
Full Mesh: Links = n(n-1)/2

Key Takeaways

Data Representation

  • • All data becomes binary (bits) for transmission
  • • ASCII: 7/8 bits per character
  • • Images: Resolution × Color Depth
  • • Hexadecimal simplifies binary representation

Data Flow

  • • Simplex: One direction only (broadcast)
  • • Half-Duplex: Alternating two-way (walkie-talkie)
  • • Full-Duplex: Simultaneous two-way (telephone)
  • • Bandwidth efficiency varies by mode

Topologies

  • • Bus: Linear, simple, single failure point
  • • Star: Centralized, scalable, common in LANs
  • • Ring: Token-passing, deterministic
  • • Mesh: Redundant, expensive, fault-tolerant