Q.Why are the cells in hexagon shape during cell splitting?

Cell splitting is the central idea that makes a cellular network work: rather than treating the whole coverage region as one area, it is broken up into many small areas called cells. Each cell is small enough that a low-power transmitter can serve it, and — crucially — the same radio channels can be reused in other cells far enough away. Splitting one large area into many small cells increases the channel capacity (the number of channels available per unit area) and decreases the cell radius, so far more users can be served with the same spectrum.

The cells are drawn as hexagons that fit together edge-to-edge like a honeycomb. The reason for the hexagon is geometric: a transmitter's coverage is naturally circular, but circles cannot tile a plane without either leaving uncovered gaps between them or overlapping wastefully. Among the regular shapes that do tile perfectly — triangle, square and hexagon — the hexagon is the one that most closely approximates a circle, so it gives the most efficient, gap-free coverage while wasting the least area.

Depending on their size, cells are further described as macrocells, minicells and microcells, with the smallest cells used where many users are packed into a small area, such as a busy city centre. Cell splitting therefore trades a larger number of small, low-power cells for greatly increased capacity — the compromise at the heart of every mobile network.