In this paper, a new combination of a multiple access scheme and spatial diversity offered by relays is proposed. In order to support several users in a system, Interleave Division Multiple Access (IDMA) is suggested here due to the capability to deal with asynchronous transmission by the users. The relays apply Amplify-and-Forward combined with delay-diversity in order to exploit the spatial diversity without the need of synchronization of the relays. Furthermore, the IDMA detector can easily

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... e extended to utilize the diversity very efficiently. So this combination of basic approaches can deal with asynchronous transmission of the users and the relays, respectively, resulting in a very flexible system with small signaling overhead.