Communication Process: Models, Channels & Protocols

TAKEAWAYS:

• Communication follows three models (linear, interactive, transactional) with distinct sender-receiver roles and feedback loops.
• Channels (wired/wireless, analog/digital) determine speed, reliability, and cost—critical for apps like Pathao’s GPS tracking.
• Protocols (e.g., TCP/IP, HTTP) define rules for data formatting, addressing, and error handling in networks like NEPSE’s stock trading system.
• Noise and interference degrade signals; techniques like error correction (parity bits, checksums) ensure data integrity in bank transactions.
• Real-world systems (eSewa’s payment gateway, WhatsApp’s end-to-end encryption) rely on layered communication models and protocols.
• Exam focus: Compare models, trace data flow in protocols, and explain how noise affects communication (e.g., NTC’s fiber-optic vs. mobile networks).

1. Definitions: What Is Communication?

Communication is the exchange of information between a sender and a receiver using a channel and a protocol. It involves:

• Sender: Originates the message (e.g., your phone when sending a WhatsApp text).
• Receiver: Decodes the message (e.g., the recipient’s phone).
• Message: The actual data (text, voice, binary code).
• Channel: The medium (air for radio, fiber for internet).
• Protocol: Rules governing how data is formatted, addressed, and transmitted (e.g., HTTP for web pages).
• Feedback: Receiver’s response (e.g., "read receipt" in WhatsApp).

Why does this matter? Without protocols, devices wouldn’t "understand" each other. For example, your laptop and a router use Ethernet protocol to share data, while your phone and a 4G tower use LTE protocol.

2. Models of Communication

Communication is classified into three models, each with different roles for sender/receiver and feedback mechanisms.

Model 1: Linear (One-Way) Model

flowchart LR
    A["Sender"] -->|"Message"| B["Channel"] -->|"Message"| C["Receiver"]

• Example: Radio broadcast, TV transmission.
• Key traits:
  • No feedback from receiver.
  • Sender controls the entire process.
• Limitations:
  • No confirmation of receipt (e.g., you can’t know if your radio listener understood the news).
  • Used where feedback is impossible (e.g., satellite TV signals).

Model 2: Interactive (Two-Way) Model

flowchart TD
    A["Sender"] -->|"Message"| B["Channel"] -->|"Message"| C["Receiver"]
    C -->|"Feedback"| B -->|"Acknowledgment"| A

• Example: Phone call, email exchange.
• Key traits:
  • Receiver provides feedback (e.g., "I got your email").
  • Communication is bidirectional but still structured.
• Limitations:
  • Feedback may be delayed (e.g., waiting for a reply to an email).
  • Used in customer service calls (e.g., Ncell helpline).

Model 3: Transactional Model

flowchart LR
    A["Sender/Receiver"] -->|"Simultaneous Message & Feedback"| B["Shared Field"]
    B -->|"Ongoing Exchange"| A

• Example: Live chat (WhatsApp call), group discussion.
• Key traits:
  • Both parties simultaneously send and receive messages.
  • Shared context (e.g., two people debating traffic routes in Kathmandu).
  • Most efficient for real-time systems (e.g., Pathao driver-passenger chat).
• Advantages:
  • Faster problem-solving (e.g., clarifying an order on Daraz).
  • More natural (like face-to-face conversation).

Comparison Table:

3. Channels of Communication

Channels are the pathways through which messages travel. They can be:

• Physical: Wired (copper cables, fiber optics) or wireless (radio waves, Bluetooth).
• Digital: Internet, mobile networks, satellite links.
• Analog: Traditional signals (e.g., voice over telephone lines).

Types of Channels

How NTC’s fiber-optic cables transmit data as light pulses. (Image: J.P.Lon at English Wikipedia, CC BY 2.5, via Openverse)

4. Protocols: Rules for Data Exchange

Protocols are agreed-upon rules that ensure devices can communicate. They define:

• Data format (e.g., text, binary, JSON).
• Addressing (e.g., IP addresses like 192.168.1.1).
• Error handling (e.g., retries, checksums).
• Flow control (e.g., how fast data is sent).

Example: HTTP Protocol (Web Browsing)

When you visit daraz.com.np, this happens:

sequenceDiagram
    participant Browser as Your Browser
    participant Server as Daraz Server
    Browser->>Server: GET /product/123 (HTTP Request)
    Server-->>Browser: HTTP/1.1 200 OK (Response with HTML)
    Browser->>Server: POST /cart (Add to cart)
    Server-->>Browser: HTTP/1.1 200 OK (Confirmation)

Key HTTP Fields:

GET /product/123 HTTP/1.1
Host: daraz.com.np
User-Agent: Mozilla/5.0
Accept: text/html

• Request Line: GET /product/123 (action + resource).
• Headers: Metadata (e.g., Host tells the server which website you’re accessing).

Error Detection: Checksums

To ensure data isn’t corrupted (e.g., during a bank transfer), protocols use checksums:

1. Sender calculates a checksum (e.g., sum of bytes modulo 256).
2. Receiver recalculates and compares.
3. If mismatched → error detected (e.g., retry or alert).

Example: Sending 1010 (binary):

• Sum = 1 + 0 + 1 + 0 = 2 → Checksum = 0010.
• If received as 1011, checksum recalculated as 3 → Mismatch!

5. Noise and Interference

Noise is any unwanted disturbance that corrupts signals. Types:

• Physical: Electrical interference (e.g., power lines affecting Wi-Fi).
• Human: Typo in an email (semantic noise).
• Channel: Weak signal (e.g., poor 4G coverage in remote areas).

How Systems Handle Noise:

Real-World Example:

• NTC’s Fiber Optics: Uses light pulses (immune to electromagnetic noise), ensuring stable internet even during load shedding.
• WhatsApp Encryption: Uses end-to-end encryption to prevent eavesdropping (noise from hackers).

6. Real-World Applications

Example 1: eSewa Payment Gateway

sequenceDiagram
    participant User as You (Phone)
    participant eSewa as eSewa Server
    participant Bank as Bank Server
    User->>eSewa: Scan QR (Request Payment)
    eSewa->>Bank: Verify Funds (HTTP Request)
    Bank-->>eSewa: Approve/Reject (Response)
    eSewa-->>User: Confirmation (SMS/Notification)

• Models Used:
  • Transactional (real-time feedback between user and bank).
  • Protocols: HTTPS (secure), SMS (for OTP).
• Channels: Mobile network (4G/5G), bank’s wired network.

Example 2: Pathao Ride Booking

1. Channel: Mobile data (4G) + GPS (wireless).
2. Protocol: Pathao’s custom API (like HTTP but for rides).
3. Noise Handling: If GPS signal is weak, Pathao asks for manual location update.
4. Feedback: Driver confirms pickup → transactional model.

Example 3: NEPSE Stock Trading

• Model: Transactional (buyers/sellers exchange orders instantly).
• Protocol: FIX (Financial Information eXchange) protocol for order matching.
• Noise: If a trade fails, the system retransmits the order.

7. Layered Communication Models

Most systems use layered models to organize communication tasks. The OSI Model (7 layers) is a standard:

![OSI 7-layer model diagram](/media/37b37e3d61e983da8ea5.jpg "How data travels from your phone to a server. (Image: Ardika6879, CC BY-SA 4.0, via Wikimedia Commons)")

Why Layers?

• Modularity: Change one layer without affecting others (e.g., upgrade from 4G to 5G only affects Physical/Data Link layers).
• Interoperability: Devices from different makers can communicate (e.g., your phone + a Chinese router).

8. Worked Example: Daraz Order Processing

Scenario: You order a product on Daraz. Trace the communication process.

1. Model: Transactional (real-time updates between you, Daraz, and the seller).
2. Layers Involved:
   • Application: Daraz website (HTTP).
   • Transport: TCP ensures all order packets arrive.
   • Network: IP routes your request to Daraz’s server.
   • Physical: Fiber optic cable carries data to Daraz’s data center.
3. Protocols:
   • HTTP: Sends your order.
   • HTTPS: Secures payment info.
   • SMTP: Sends order confirmation email.
4. Noise Handling:
   • If your internet drops, TCP retransmits lost packets.
   • Daraz’s server uses checksums to verify order data integrity.

Exam Tip

1. Models: Always compare linear vs. interactive vs. transactional in terms of feedback and direction.

   • Exam Q: "Why is WhatsApp more efficient than email for customer support?"
   • Answer: WhatsApp uses a transactional model (instant feedback), while email is interactive (delayed replies).

2. Protocols: Draw a sequence diagram for real-world examples (e.g., eSewa payment, Pathao ride).

   • Exam Q: "Explain how HTTP works when you visit daraz.com.np."
   • Answer: Use the sequence diagram above + explain headers like Host and GET.

3. Noise: Relate to real systems:

   • Exam Q: "How does NTC reduce noise in fiber-optic cables?"
   • Answer: Uses light pulses (immune to electromagnetic interference) + error correction in higher layers.

4. Layers: Memorize the OSI model and match protocols to layers (e.g., TCP is Transport, IP is Network).

   • Exam Q: "Which OSI layer handles IP addressing?"
   • Answer: Network Layer (Layer 3).

5. Worked Examples: Always tie theory to real apps (eSewa, WhatsApp, NTC). Examiners love this!

   • Exam Q: "How does Pathao use communication models?"
   • Answer: Transactional model for live chat + TCP for reliable ride data.

Final Checklist for Full Marks: ✅ Define sender, receiver, channel, protocol, feedback. ✅ Compare three models with examples (radio vs. WhatsApp call). ✅ Explain wired vs. wireless channels with speed/reliability trade-offs. ✅ Draw a sequence diagram for a real protocol (HTTP, eSewa). ✅ Describe error handling (checksums, retransmission) with a binary example. ✅ Link to Nepali apps (eSewa, Pathao, NTC) in every possible way. ✅ Sketch the OSI model and label a protocol to each layer.