Explanation:

A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity.

Functions of BTS

• The process of channel coding, Encryption, Multiplexing and modulation for trans-direction and reverse for reception are to be carried out. It has to arrange for transmission in advance from the mobiles depending upon their distance from BTS (Timing Advance). Hence option 1st is correct.