In this paper, we consider single-cell cellular networks assisted with fixed relay station (RS), used by mobile stations (MS) to access the base station (BTS) via a relaying strategy. The RSs are positioned around the BTS, in such a way that wireless channels on the relay link (from RSs to the BTS) are line-of-sight, we analyze the achievable sum-of-rates for up-link communications. We compare two relaying strategies at the RSs, namely Amplify-and-forward (AF) and Compress-and-forward (CF). It is assumed that mobile signals and relay signals are emitted on orthogonal bands (FDD), with the possibility of having a larger bandwidth (BW) on the relay-to-base links. We predict the system gains bought by relays, in comparison with two other reference systems. One reference is an ideal relay-based system where the relays enjoy noiseless communications to the BTSs, i.e. a so-called distributed antenna system (DAS). The second reference is offered by a conventional cellular systems without relays, but same number of overall infrastructure antennas. In this paper, it is demonstrated the surprising result that with a relay bandwidth just twice that of the mobile's bandwidth, the system capacity approaches that of an ideal distributed antenna system, (while probably being much superior in practice in terms of ease of deployment and cost). The capacity gains of the relayassisted network over a conventional network are also analyzed.