Full Duplex and Half Duplex Channel Capacity As far as I know about full and half duplex, if we have a channel with bandwidth 10Mbps then in full duplex both sender and receiver can transfer 10Mb in both directions at the same time and in half duplex only sender or receiver can transfer 10Mb at a time. If suppose, propagation delay is 1 sec then is the capacity of channel in full duplex 20Mb and in half duplex 10Mb ? How can the capacity of a channel double based on the mode, it should be same all the time right?

Think of a half-duplex connection as a single channel that you can turn around between packets. Then think of a full-duplex connection as two unidirectional channels that can be used simultaneously.

Physically, all modern twisted-pair or fiber Ethernet connections have two channels, one for sending, one for receiving (most prominent in 10BASE-T, 100BASE-TX and fiber). With half duplex they may not be used at the same time while with full duplex they may.