Answer any Three of the following questions.a$)$ Explain the three technical issues of mobility. b$)$ Briefly discuss the $1$G$,2$G$,3$G and $4$G technologiesc$)$ Discuss the three satellite systems with the help of examples. d$)$ Explain the mobile agents.e$)$ Discuss the Bluetooth technology and its advantagesf$)$ Illustrate the layers of IrDA protocol stackg$)$ Difference between CSMA$/$CD and CSMA$/$CA$.$h$)$ Discuss the three modulation techniques of IEEE $802\mathrm{.}11$ standard used for sending MAC frames.