Pulse position modulation (PPM) is an encoding scheme in which the digital input value determines the position of a narrow pulse relative to the clocking time. This method is used in optical communication systems such as optical fiber, IR local area networks, and IR remote controls, where efficiency is required and little or no external interference occurs. Transmission uses an intensity modulation scheme, in which the presence of a signal corresponds to a binary 1 and the absence of a signal corresponds to binary O a. A 16-PPM scheme is used for the 1-Mbps IEEE 802.11 infrared standard. Each group of 4 data bits is mapped into one of the 16-PPM symbols; each symbol is a string of 16 bits. Each 16- bit string consists of fifteen Os and one binary 1, such that the position of the binary 1 in the string encodes a value from 0 through 15. a1. What is the period of transmission (time between bits)?For the corresponding infrared pulse transmission: a2. What is the average time between pulses (1 values) and the corresponding average rate of pulse transmission? a3. What is the minimum time between adjacent pulses? a4. What is the maximum time between pulses? b. Repeat (a) for the 4-PPM scheme used for the 2-Mbps infrared standard. In this scheme, each group of 2 data bits is mapped into one of four 4-bit sequences