surements in the multi-cell environment with 10 MHz of bandwidth and proportional fair scheduling. Three different cases were studied in terms of adjacent cell loading: full load in adjacent cells, partial load in adjacent cells with random allocation and partial load in adjacent cells with fixed allocations. FSS OFF case uses wideband CQI reporting which gives no information about the interference or fading in the frequency domain. FSS ON case uses frequency-selective CQI reporting. FSS showed 40-65% improvement in the cell edge throughput depending on the case. The highest gain was obtained with partial load and fixed allocations because CQI reporting can accurately reflect the inter-cell interference. FSS can also provide some gain with the full loading in the adjacent cell because of frequency-dependent fast fading. This FSS gain would be lower for the moving UEs since CQI reporting would not be fast enough to follow the fast fading. 7.3 Enhanced Inter-cell Interference Coordination 7.3.1 Concept Description The small cell deployment on the same frequency with macro cell requires efficient interference management. The challenge is that the small cell coverage area can be very small in a co- channel deployment due to the difference in the transmission power between the macro cell and the pico cell. If there would be no co-channel macro cell, the pico cell could provide service to larger coverage area. The challenge is illustrated in Figure 7.7. The target is to increase the pico cell coverage area in the case of co-channel deployment. One option is to coordinate the interference in the time domain, which is defined in 3GPP Release 10 and called enhanced inter-cell interference coordination (eICIC). The solution is shown in Figure 7.8. The macro cell stops its transmission in some subframes to minimize interference to the pico cells. Those muted subframes are called almost blank subframes (ABS). Only cell-specific reference signals and other mandatory signalling channels including physical control format indica