ng at other carrier frequencies). The traffic model is dynamic arrival according to a homogeneous Poisson process with finite payload per call. In line with expectations, the benefits from the considered ICIC scheme are modest at low offered traffic as the inter-cell interference is less dominant. This also causes the ICIC scheme to mute (i.e. use ABS) with a probability of less than 5% for the offered load of 50 Mbps. When the offered load is increased to 100 Mbps (i.e. close to the clusters' capacity limit) the gain from the ICIC scheme becomes attractive as there starts to be much more inter-cell interference to combat. At 100 Mbps offered load, 5 percentile gain 50 percentile gain Average offered load (Mbps) Figure 8.17 User throughput gain versus offered load per small cell cluster from using proactive time-domain muting LTE Small Cell Optimization the average probability of muting increases to 7%, with some cells muting up to 45% of their subframes. Those cells that mute the most are the ones being identified as aggressor for multiple victim users, and therefore tend to also be the cells that are located in the centre of small cell cluster. 8.4.3 Reactive Carrier-Based Inter-cell Interference Coordination The basic principle of any reactive ICIC scheme is to take interference coordination actions only if problems are detected, and otherwise let the system operate with its current configuration. In order to illustrate such principles, let us consider a system design target where the users should be served with at least a certain minimum data rate, expressed by the guaranteed bit rate (GBR). In this context, interference coordination actions are triggered whenever the data rate for a user is found to fall below its minimum target. Assuming that each small cell is able to transmit on multiple component carriers (CCs), the ICIC can be conducted in the frequency domain by switching CCs on/off at the small cells in a coordinated manner - also known as carrier-based ICIC. Carrier-based ICIC is especially applicabl