This paper investigates the secure communications of multiuser untrusted amplify-and-forward relay networks in the presence of\ndirect links. In the considered system, one user is selected among multiple ones for secure transmission to the destination node\nwith the help of an untrusted relay node. To reduce the information leakage to the untrusted relay, the paper considers two selection\ncriteria to select the user based on the direct and the relaying links, respectively.The impact of direct and the relaying link on the\nsystem secrecy performance is studied by deriving the close-form ergodic secrecy rate (ESR) as well as the asymptotic expression.\nFromthe asymptotic expression, it can be found that the asymptotic ESR increases linearlywith the logarithmof the average channel\ngain ratio of the direct link to the relaying link.
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