ABSTRACT: Cooperative communication has offered a new dimension to the design of wireless transmission protocols. Many advantages of a relay have been reported such as being a virtual antenna providing additional spatial diversity or multiplexing capability. However, these benefits often come at a cost when half-duplex relays are deployed. Spectral inefficiency would become a serious concern since additional timeslots are required for message overhearing or forwarding. The optimal role of a relay and its potential in different networks remain unclear in general. In this talk, we focus on relaying in a cellular network and discuss several cooperation benefits that could be achieved in a spectrally-efficient setting using half-duplex relays. Channel state information is assumed only at receivers. We first consider the uplink and demonstrate cooperation benefits other than just the availability of the additional spatial relaying paths. Specifically, we show that a cooperative user there could utilize the overheard information of other users to further improve its own code distance spectrum. Then, the focus is shifted to the downlink where we study how such network topology facilitates spectrally-efficient relaying using simple repetition-type decode-and-forward protocol. Good diversity-multiplexing tradeoff is observed.