India’s Breakthrough Underwater 4G Connectivity: Understanding Its Far-Reaching Implications

India’s 5G network has expanded dramatically since its launch, reaching cities, districts, and towns. However, in areas where 5G is still unavailable, 4G is the best bet. But who would have imagined smartphones receiving the 4G network signals underwater?

The Department of Telecommunications (DoT) has shared a video showing a smartphone receiving 4G network signals under the sea at Swaraj Deep in the Andaman and Nicobar Islands, underscoring the advancements in India’s telecommunications infrastructure. But how does 4G work underwater?

Understanding underwater 4G technology

The fourth-generation wireless communication technology was developed for terrestrial connections, such as mobile phones and IoT (Internet of Things) devices. 4G uses traditional radio waves to transmit data, but they cannot propagate well through water because of rapid attenuation, a condition where the intensity of signals or waves decreases rapidly over time.

“It’s difficult to receive 4G signals underwater because water significantly weakens radio signals, preventing them from traveling effectively,” telecom expert Charu Paliwal told Republic Tech in an exclusive conversation.

To make 4G connectivity available underwater, the communication must rely on acoustic waves (sound-based signals) or optical signals (lasers or LEDs).

Acoustic communication uses sound waves to transmit data similar to how submarines communicate via sonar. It is similar to how dolphins communicate using sonar. This technology allows 4G networks to cover long distances. However, it has a flip side. The network has limited bandwidth and high latency, resulting in slow data speeds — typically in kilobits per second (kbps) — and transmission delays. It also faces challenges such as marine life, ships, or waves, while the speed of sound in the water adds latency to the communication system.

On the other hand, optical signal-based communication involves light (particularly in the blue-green spectrum) that easily penetrates water compared to other wavelengths to offer high-speed data transfers. Optical communication allows data speed ranges of megabits to gigabits per second (Mbps to Gbps). However, the transmission happens over short distances of typically 10-100 metres as it is prone to water absorption. Optical systems also require a clean line of sight to work as they are impacted by turbidity, plankton, or particulate matter present in water.

A hybrid system, combining acoustic and optical methods, is also used to offer long-distance coverage, low-bandwidth controls, and high-bandwidth data transfers, typically used for data transmission from a submarine.

India’s approach to underwater 4G

India’s first underwater 4G system uses submarine optical fibre cables (OFCs), which allows for high-speed connections, faster internet, and better mobile coverage. According to studies, submarine OFCs have a 70 per cent better data transfer rate and 50 per cent lower latency, which could help introduce commercial communication and boost naval connectivity in the Andaman & Nicobar Islands.

“In the Andaman and Nicobar Islands, 4G connectivity has improved with the introduction of a submarine optical fibre cable. The submarine fibre optic cable acts as the backbone for mobile networks on land. With this high-speed connection, telecom providers can set up 4G networks across the islands, giving people faster internet and better mobile coverage,” Paliwal added.

How will underwater 4G connectivity help boost wireless connectivity?

While underwater 4G is of little help to people living above the water, it could provide significantly faster data transfer speeds and communication systems to divers, underwater robots, autonomous underwater vehicles (AUVs), and submarines, enabling them to stream high-quality video, sensor data, and transfer large files in real-time. This is critical for applications such as underwater exploration or remote vehicle operations.

According to Paliwal, underwater 4G connectivity will also pave the way for 5G networks on the islands. “People will have a much better experience with web browsing, online gaming, and video calls. Digital services like online education, e-governance, and remote healthcare will also work more smoothly,” said Paliwal, adding that it will also give “a big boost” to local tourism and economy.

With the latest breakthrough, India has joined the likes of the United States and Norway, which pioneered underwater wireless networks for naval operations.

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