Compared to that of the half duplex, the end-to-end channel capacity of the full duplex decreases more slowly.
Moreover, the signal processing of full duplex is considered to be more complicated than that of the half duplex.
The end-to-end channel capacity of full duplex is higher and more robust than that of the half duplex due to a double of allocation time and a half of delay time.
The reason this is not obvious is because of the half-duplex nature of the relay.
However, because of the half-duplex constraint at the relays, relaying-assisted transmission would require the use of a higher order constellation than in the case when a continuous link is available from the BS to the UT.
In such study, it was found that the use of relays to assist a communication with the objective of increasing its capacity is only effective in high path-loss scenarios, because of the half-duplex constraint of RA schemes.
In the above two approaches spatial diversity can be achieved, but because of the half-duplex constraints of relays, the information has to be transmitted in half of the time that would be needed in the case of a continuous link available from the source to the destination.
In this approach, spatial diversity can be achieved, but because of the half-duplex constraints of relays, the information has to be transmitted during half of the time that would be needed in the case of a continuous link available from the source to the destination.
Because of the half-duplex constraint at the relays, transmission of a data rate equivalent to that of a modulation technique with bits per symbol in the case the direct link would be available from the BS to the UT would require the use of a constellation with bits per symbol.
The classical RA systems using distributed space-time/frequency coding algorithms, because of the half-duplex constraint at the relays, require the use of a higher order constellation than in the case of a continuous link transmission from the base station to the user terminal.
