The present invention increases the interference diversity in systems with the frame structure described above by using frequency hopping sequences that are selected considering characteristics of the channel relating to how the channel varies. According to a first embodiment, the channel characteristics relate to channel coherence time and according to a second embodiment, the channel characteristics relate to channel coherence bandwidth. For channels with long coherence times, the transmission hops back and forth several times during a TTI on the different available frequencies. For channels with widecoherence bandwidths, hopping may be performed between the frequency used by the reference signals and its neighbor frequencies. For channels with both long coherence times and widecoherence bandwidths, a combination may be used.