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Effective capacity (EC) is a valuable metric in investigating the impact of the physical-layer infrastructure on the quality of service (QoS) of the data link layer. By means of the EC, this paper provides a link-layer look at the concept of multirelaying transmission. A closed-form expression for the EC of a multirelay network is derived to simplify the computation of this quantity. It is shown that increasing the number of relays leads to an unavoidable reduction in EC. Some techniques such as best relay selection (BRS) and distributed space-time coding (DSTC) are used to solve this problem. It is found that the EC performance of BRS, DSTC, and direct transmission schemes extremely depends on the amount of QoS exponent θ. Inspired by this dependence, a novel interesting cross-layer relaying transmission framework is introduced, in which the best scheme of transmission is selected for maximizing the EC, according to …