Transmission Impairments and Communication Performance

Transmission Impairments

1. Attenuation (Signal Weakening)

Attenuation occurs when the signal loses strength as it travels through a medium like a wire, fiber optic cable, or air. A long telephone cable weakens the voice signal, requiring amplifiers to boost it. Using repeaters or amplifiers helps restore signal strength.

2. Distortion (Signal Alteration)

Distortion happens when different frequency components of a signal travel at different speeds, changing its original shape. A song played over a poor-quality Bluetooth speaker may sound different. Equalizers or filters can help correct distortions.

3. Noise (Unwanted Signals)

Noise refers to unwanted disturbances that interfere with communication, making the signal unclear.

• Thermal Noise: Caused by random electron movement in circuits.

• Intermodulation Noise: Occurs when different frequency signals mix and create interference.

• Crosstalk: When one signal affects another, like hearing another conversation in a landline phone.
  Using shielding, error detection, and noise filtering techniques reduces noise impact.

Performance Metrics of Communication Systems

1. Bandwidth (Data Capacity)

Bandwidth determines how much data can be transmitted in a given time. A fiber optic cable has higher bandwidth than a copper wire, allowing faster internet speeds.

2. Throughput (Actual Data Transfer)

Throughput is the real data transfer rate, often lower than bandwidth due to network congestion. If your internet provider offers 100 Mbps, but you get 70 Mbps, your throughput is 70 Mbps.

3. Latency (Delay in Transmission)

Latency is the time taken for data to reach the receiver. Video calls may have a delay due to high latency. Using fast network connections like fiber optics reduces latency.

4. Jitter (Variation in Delay)

Jitter occurs when packets arrive at different times, causing choppy audio or video lag. It is common in online gaming and video streaming. Buffering techniques and quality-of-service (QoS) settings help minimize jitter.

Transmission Modes

1. Parallel and Serial Transmission

• Parallel Transmission: Sends multiple bits at once using multiple wires. Used in internal computer data transfer (RAM to CPU). Faster but costly due to multiple channels.

• Serial Transmission: Sends bits one by one over a single wire. Used in USB and internet data transfer. Cost-effective but slower than parallel transmission.

2. Asynchronous and Synchronous Transmission

• Asynchronous Transmission: Sends data at irregular intervals using start and stop bits, like keyboard input (each keypress sends data separately). Simple and cost-effective but less efficient due to extra bits.

• Synchronous Transmission: Sends data in a continuous stream with synchronized timing, like video streaming and live calls. Efficient for large data transfer but requires synchronization between sender and receiver.

Satellite Communication

Introduction

Satellite communication is a technology that uses artificial satellites to transmit and receive signals across long distances. It plays a crucial role in modern communication systems, enabling global connectivity, television broadcasting, GPS navigation, internet services, and military applications.

Working of Satellite Communication

1. Signal Transmission (Uplink) – A ground station sends signals (radio waves) to the satellite in space.

2. Signal Processing – The satellite receives, amplifies, and changes the frequency of the signal to avoid interference.

3. Signal Reception (Downlink) – The processed signal is transmitted back to another ground station or a receiving device (like a TV dish).

This process ensures communication across vast distances, overcoming geographical barriers.

Types of Satellites in Communication

1. Geostationary Earth Orbit (GEO) Satellites

Placed at 35,786 km above Earth.

Remains fixed over a specific location.

Used for TV broadcasting (DTH), weather monitoring, and internet services.

Example: INSAT (India), SES, Intelsat.

Advantage: Provides continuous coverage.

Disadvantage: High latency (signal delay).

2. Medium Earth Orbit (MEO) Satellites

Placed between 2,000 km and 35,000 km above Earth.

Used for GPS navigation, telecommunications, and disaster management.

Example: GPS (USA), Galileo (Europe), Glonass (Russia).

Advantage: Lower latency than GEO satellites.

Disadvantage: Requires multiple satellites for coverage.

3. Low Earth Orbit (LEO) Satellites

Placed at 500 km to 2,000 km altitude.

Used for satellite phones, remote sensing, and internet services (like Starlink).

Example: Starlink (SpaceX), Iridium, OneWeb.

Advantage: Low latency, better data speed.

Disadvantage: Needs a large number of satellites to maintain coverage.

Applications of Satellite Communication

1. Broadcasting (TV & Radio)

Direct-to-Home (DTH) services like Tata Sky, Dish TV rely on satellites to provide television signals.

FM radio stations also use satellites to transmit signals.

2. Global Positioning System (GPS)

GPS satellites help in navigation and location tracking for vehicles, smartphones, and military operations.

Used in Google Maps, Ola, Uber, and logistics tracking.

3. Internet and Telecommunication

Provides high-speed internet to remote areas where traditional broadband cannot reach.

Satellite phones are used in disaster-stricken areas or military operations.

4. Disaster Management

Satellites help monitor natural disasters like cyclones, tsunamis, and earthquakes.

Aid organizations use satellite communication for rescue operations.

5. Weather Forecasting

Satellites collect atmospheric data to predict weather conditions and climate changes.

Used by meteorological departments worldwide.

6. Military and Defense

Secure satellite networks are used for intelligence gathering, communication, and surveillance.

Countries launch defense satellites for border security and space defense systems.

Advantages of Satellite Communication

✔ Provides global coverage, even in remote locations.

✔ Reliable for long-distance communication.

✔ Useful for emergency and disaster management.

✔ Supports high-speed internet and telecommunication.

Disadvantages of Satellite Communication

✘ High latency in GEO satellites, causing a delay in real-time communication.

✘ Expensive launch and maintenance costs.

✘ Weather interference can degrade signal quality.

✘ Limited lifespan (satellites need replacement every 10-15 years).

Future of Satellite Communication

5G and Satellite Integration – Expanding 5G networks using satellites.

Low-Latency Internet – Starlink and OneWeb are working on reducing internet latency.

AI in Space Communication – AI will improve satellite efficiency and automation.