Medium access control

This includes medium access control(MAC) algorithms which were specificially adapted to the wireless domain .Medium access control consist all mechanism that regulate user access to a medium using FDM,TDM,SDM.MAC is thus similar to traffic regulations in the vehicals used in same street crossing TDM, it reqires rules to cross TDM.
IT includes hidden and exposed terminals:
Consider a scenario with 3 mobile phones as assumption .The transmission ranges of mobile A can reach to B but not C.On the other hand transmission range of C cant reach A ,it can only reach B .Finally transmission range of B can reach both A & C.
A starts sending to B , C does not receive any transmissoin .C also wants to send something to B.But it detects that the medium is busy,so carrier ssense fails .C also starts sending to B ,thus causing collision at B .But A cannot detect this collision and continues to send to B.
Thus A is hidden for C and vice versa
While hidden terminals may cause collision .the next effect only causes necessary delay .Now consider the situation that B sends something to A and want to trnsmit data to some other mobile phones outside the interferance range of A and B.C senses the carrier and detecs htat the carrier is busy .C postpones the its transmission until it detects the medium being idle again .But as A is outside the interferance of C ,waiting is not necessary .Causing collison at B does not matter much because the collison is too weak to resist to A.In this situation C is exposed to A.