A cellular service provider decides to use digital TDMA scheme which can tolerate a signal-to-interference ratio (SIR) of 15 dB in the worst case. Assume that all co-channel BSs are equal distant from the mobile, i.e., Di-D. Also assume a path loss exponent of n-4. Find the optimal value of N for a) Omnidirectional antennas b) 120 degree sectoring antennas c) 60 degree sectoring antennas. Should sectoring be used. If so, which case, 60 degree or 120 degree, should be used?