if last 4 digits of your student ID are 7281, then a = 7, b=2, c = 8, d = 1. Design an OFDM system with the following specifications: transmissions should be protected against multipath in a cell with radius = 100b+10c+d meter. The required data rate is = 10c + d Mbps. The bandwidth available for transmission is = 10+a MHz. 1) Select the duration of the cyclic prefix. 2) Given the cyclic prefix duration you selected in a), select the duration of the OFDM symbol such that cyclic prefix is no larger than 25% of the OFDM symbol duration. 3) What is the number of information bits each OFDM symbol needs to carry to meet system specification? 4) What is the subcarrier spacing in the system you designed? 5) Suggest a number of subcarriers such that the OFDM symbol meets system requirements. 6) What constellation (digital modulation) should be used?