Add A.3.6; Update A.3.8 Conclusions

- Which strategy to conduct the developments needed to replace the current network simulation approach

The feasibility study is organized as follow:

- The clause [A.2](#a2-current-network-simulation-description) covers the analyze of the current architecture and provides the conclusion of this study;

- The clause [A.2](#a2-current-network-simulation-description) covers the analyze of the current architecture and provides the pros and cons of replacing;

- The clause [A.3](#a3-simu5gsimulte-description) covers the Simu5G/SimuLTE simulators [\[i.5\]] and provides the pros and cons of replacing;

- The clause [A.4](#a4-replacement-procedure) covers all the required changes in the current architecture to do the replacement.

#### A.3.5 Simulation modes

The Simu5G/SimuLTE simulators [\[i.5\]](#_ref_i.5) provides 2 simulations:

The Simu5G/SimuLTE simulators [\[i.5\]](#_ref_i.5) provide 2 simulations:

- The non‑emulation simulation is pure, offline discrete‑event runs where all traffic endpoints are simulated modules and time is virtual, - - - The emulation simulation runs in real time and connect the simulated 5G network to real interfaces and applications so real packets traverse the simulated RAN and core network.

This is the emulation mode that is required here. The emulation scenarios map simulated network interfaces (e.g. at UE, router...) to real host interfaces (TAP/veth, NICs), so IP packets from real processes or devices enter the simulation, traverse the 5G NR/LTE stack, and return to the real network.

### A.3.5 Architecture

#### A.3.6 Real-time emulation modes

#### A.3.5.1 Overview

By is architecture, the Simu5G/SimuLTE simulators [\[i.5\]](#_ref_i.5) are a discrete-event simulators (see OMNeT++ manual: https://doc.omnetpp.org/omnetpp/manual/#sec:simple-modules:discrete-event-simulation). So the simulation does not match real time clock.

To do so, a real-time simulation mode is required. Omnet++ provides such mode to run simulations so that simulation time progresses at the same pace as wall-clock time. This type of execution is also called "real time emulation". But it comes with a high limitation: this is only possible if the complexity of your simulation is low enough so that OMNeT++ can slow down the simulation time to match the wall-clock time. 

### A.3.7 Architecture

#### A.3.7.1 Overview

The fugure below shows a simplified architecture of Simu5G.

└─────────────────────────────────────────┘

```

#### A.3.5.2 Network description

#### A.3.7.2 Network description

<mark>To explain what is NED?</mark>

#### A.3.5.3 Behavior implementation (C++ classes)

#### A.3.7.3 Behavior implementation (C++ classes)

<mark>To explain behavior implementation using C++ classes?</mark>

#### A.3.5.4 Probes

#### A.3.7.4 Probes

<mark>To explain how to use the probes?</mark>

#### A.3.5.5 ETS MEC Support in Simu5G

#### A.3.7.5 ETS MEC Support in Simu5G

<mark>To explain ETS MEC support in Simu5G?</mark>

#### A.3.5.6 Why do we choose the Probes solution?

#### A.3.7.6 Why do we choose the Probes solution?

<mark>To explain why do we choose Probes mechanism isnstead of Simu5G MEC RNI?</mark>

#### A.3.5.5 How to develop a UE application in Simu5G environment

#### A.3.7.5 How to develop a UE application in Simu5G environment

<mark>Not sure this clause is useful at this stage</mark>

### A.3.6 Advantages of Simu5G/Simu4G simulators

### A.3.8 Advantages of Simu5G/Simu4G simulators

- Realistic Protocol Simulation: Complete 3GPP protocol stack

- Dynamic Network Behavior: Handovers, connection management, bearer setup

- MEC Integration: Built-in MEC support

- Research-Grade: Widely used in academic and industry research

### A.3.7 Limitations of Simu5G/Simu4G simulators

### A.3.9 Limitations of Simu5G/Simu4G simulators

- Performance: Discrete event simulation can be slower than simple TC-based approach

- Complexity: Requires understanding of OMNeT++ and simulation concepts;

>

> 1. A network scenario containing a lot of PoAs and UEs can drastically reduce the performance of the Simu5G/4G simulators. The objective of 10 simultaneous connections on the MEC Sandbox could be achieved.

>

> 2. Regarding the huge amount of work to be done to replace the current network simulation with Simu5G/SimuLTE simulators [\[i.5\]](#_ref_i.5), the objective of the Task#3 as defined in the STF 707 ToR, could be partially covered. An extension of this STF may be required (or a split with a future STF ?). A list of development steps is proposed in [clause A.4.3](#a43-phase-3-implementation). The 3 first steps are the ones to be achieve during this STF.

> 2. If the network scenario is to complex, the real-time emulation mode cannot be apply and the simulation will not match with real-tme clock.

>

> 3. Regarding the huge amount of work to be done to replace the current network simulation with Simu5G/SimuLTE simulators [\[i.5\]](#_ref_i.5), the objective of the Task#3 as defined in the STF 707 ToR, could be partially covered. An extension of this STF may be required (or a split with a future STF ?). A list of development steps is proposed in [clause A.4.3](#a43-phase-3-implementation). The 3 first steps are the ones to be achieve during this STF.

>

> We also propose to start the task 3 immediately after the acceptance of this feasability study.