1. The cell association is done by choosing the BS/Femto that provides the highest recveived power at the UE. This is done including the transmit-power, large scale path loss and shadowing, but not fading.
2. The decision is not taken by the actors in the network, but on an abstract level, simply comparing the received powers (as described above). So you could say that corresponds to the decision of a central controller.
3. In general, the UEs are assumed to be “fullbuffer” users. To activate traffic models, you can set
simulation_type = ‘tri_sector_tilted_traffic’;
in your launcher file. The currently implemented traffic models can be found in +traffic_models. The assigment is done in LTE_trafficmodel.m
Please let me know if you have further questions regarding the cell association or traffic models.
For what you described, I would say that it mostly depends on the number of UEs per sector as well as on their traffic models (the frequency of how fast new packets are generated), as well as the bandwidth (how fast can the generated packets be transmitted). In the schedulers that support traffic models (RoundRobin_Traffic and PropFair_Traffic) you will see that by checking attached_UEs(user_ind(ii)).traffic_model.bit_count; you can check if a traffic model has data available. This could be a trigger for you to turn on a BS.