Complex sentence: The Kennelly-Heaviside layer, also known as the E region or just as the Heaviside layer, named after Oliver Heaviside, is a layer of ionised gas occurring at 90-150km in above the ground--one of several layers in the Earth's ionosphere.
Split into simpler sentences: The Kennelly-Heaviside layer is also known as the E region or just as Heaviside layer (after Oliver Heaviside). It is a layer of ionised gas occurring at 90-150km in altitude, one of several layers in the Earth's ionosphere.