Consequently, the relatively low eukaryotic barriers against endosymbiotic gene transfer compared to random HGT represents a continuous genetic link to archaea and bacteria that is probably still evolutionary active today.
Motivated by the fact that it is common to have large objects or other hindrances affecting the DP, the authors of [19] proposed a new algorithm for these situations, while bringing RA performances close to the continuous link transmission.
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.
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.
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.
This gives Glenrothes a continuous dual-carriageway link to Edinburgh and the major central Scotland road networks, whilst much of the route north to Dundee remains a single-carriageway.
Thus, for the case of single-antenna relays, it takes twice the time to transmit as compared to the time that the continuous link would take if available for the two-relay case, and thrice the time for three- and four-relay cases and so forth.
Through the use of the proposed multiple-relay-assisted scheme we achieve full diversity, with a moderate degradation relatively to the case where a continuous link is available, where the number of RNs and antennas in each one can be selected according to the required quality of service.
Despite the advantages mentioned in using the RA schemes, they require the use of constellations with higher cardinality in comparison with the continuous link transmission from the base station(BS) to the user terminal UT), when this is available.
