Bit map protocol is basic reservation protocol

Assume there are N stations and all stations wants to transmit. So in the contention period there will be N contention slots where every station will be given a chance to make a reservation by putting 1 bit in its contention slot(in basic reservation protocol a station uses 1 bit to make reservation)

For worst case assume s is first station. Station s will wait for N-1 contention slots in the contention period. As s made the reservation first so after N-1 contention slots it can begin transmission

Generalizing, if there are 'd' reservation bits then s has to wait for (N-1)*d bit times