A multi-relay-selection scheme with cyclic delay diversity

In our proposed multi-relay-selection scheme with cyclic delay diversity (CDD), relays with spectral efficiency above a threshold are chosen to forward information, and a distinct cyclic shift is assigned to each selected relay. We derive an approximate expression of the end-to-end mutual information for the proposed scheme. We further analyze the outage probability and diversity-multiplexing tradeoff (DMT) performance. Numerical results show that the proposed scheme can realize full diversity and achieve the same outage probability and DMT performance as that of the selection cooperation scheme without the need for feedback information and strict synchronization among relays.