TELECOM TRANSMISSION INFRASTRUCTURE
The transmission infrastructure serves as the "backbone" of the telecommunications network, responsible for carrying massive amounts of data over long distances—between cities, states, and even continents.
1. Fundamentals of Transmission Systems
Transmission is the process of moving voice, data, or video signals from one point to another. In the BSNL network, this is achieved through a combination of fiber optics and microwave links.
2. Multiplexing Hierarchies: PDH vs. SDH
To carry thousands of conversations on a single cable, we use multiplexing.
- PDH (Plesiochronous Digital Hierarchy): An older standard where data streams are not perfectly synchronized. To extract one channel, the entire high-speed signal must be demultiplexed (like unloading a whole truck to find one box).
- SDH (Synchronous Digital Hierarchy): The modern standard used by BSNL. It allows "Add-Drop" multiplexing, meaning we can pull out a single data stream without disturbing the others. This makes the network much more flexible.
3. DWDM (Dense Wavelength Division Multiplexing)
DWDM is a technology that allows multiple "colors" or wavelengths of light to be sent through a single strand of fiber at the same time.
- Example: Imagine a fiber optic cable as a highway. Without DWDM, it's a single-lane road. With DWDM, it becomes an 80-lane superhighway, with each lane carrying its own massive stream of data. This is how BSNL handles terabits of data across India.
4. Microwave Transmission
In terrains where laying fiber is difficult (like hilly areas or dense urban centers), BSNL uses microwave radio.
- Point-to-Point: Signals are beamed from one tower's dish to another.
- Challenge: Microwave signals can be affected by "Rain Fade," where heavy rain absorbs the radio energy, causing temporary signal drops.
5. Passive Infrastructure
This refers to the non-electronic parts of the site:
- Towers: GBT (Ground Based Tower) for rural/open areas and RTT (Roof Top Tower) for urban buildings.
- Power: Telecom equipment requires 24/7 power. Sites use Battery Banks for short outages and Diesel Generators (DG) for long-term backup.
- Cooling: High-speed electronics generate heat. Shelter air conditioning is critical to prevent hardware failure.
Summary:
The transmission layer ensures that data moves reliably across the network. Whether through light in a fiber or radio waves in the air, it is the foundation of modern connectivity.