Difference between network simulation & system-level simulations

[Chinmay Bhat]

Hi All!

In System-level simulations, physical layer is abstract. It is simplified & low complexity but captures the essential characteristics with high accuracy. In Network-Simulations, again physical layer is abstract and focus is on the MAC & higher layers. 

Documentation of LTE module (https://www.nsnam.org/docs/models/html/lte-design.html#lte-model) says how Network-simulations are different from System-level simulations as below. 

1. At the radio level, the granularity of the model should be at least that of the Resource Block (RB). In fact, this is the fundamental unit being used for resource allocation. Without this minimum level of granularity, it is not possible to model accurately packet scheduling and inter-cell-interference. The reason is that, since packet scheduling is done on a per-RB basis, an eNB might transmit on a subset only of all the available RBs, hence interfering with other eNBs only on those RBs where it is transmitting. Note that this requirement rules out the adoption of a system level simulation approach, which evaluates resource allocation only at the granularity of call/bearer establishment.

   What i understand is, Network Simulations are not System Level simulations because the granularity in Network Simulations is Resource Block in frequency domain.  

Questions: 

        1) What is the granularity in System-Level simulations? 

        2) How granularity (in time / freq) affects the Network simulations / System-level simulations? 

        3) What are the differences between Network & System-level simulations ?

Thanks and regards

Chinmaya