NB IoT RA Example Script - a3794110/ns-3-NB-IoT GitHub Wiki

1. Overview

This article offer the description of NB-IoT RA example script and the brief performance validation referred from article Simulating NB-IoT Random Access: Using ns-3 as an Example.

2. NB-IoT RA example script

This part of project is based on ns-3 LTE module, hence, naming systems of functions are the same as LTE module. (funciton names and using way is same as LTE module) Tables I shows the parameters in this project.

Table IV

It is worth mentioning that the NB-IoT random access will initiate in any attach procedure when you use our project.

2.1 What this example script capable of ?

There are 1 UE and 1 eNodeB in this scenario; we can observe the influence of CE level mechanism with modying the distance between UE and eNodeB.

2.2 How to run the example srcipt ?

We offer an example script for observing NB-IoT RA on ns-3. To run the script, please put the following file into folder, waf.

NB-IoT_RA_example.cc

Then run the following command for observing the RA procedure.

./waf --run scratch/NB-IoT_RA_example

2.3 How to modify the parameter for observing the CE level mechanism?

The line 143 in file NB-IoTRAexample.cc is the location of UE position assignment:

 positionAlloc->Add (Vector(3000, 0, 0));

Modify the position to 3000, 30000 and 60000 can observe the CE level mechanism with CE level 1, 2 and 3, respectively.

3. Validation

We valid our implementation with three perspectives: (briefly refer from article Simulating NB-IoT Random Access: Using ns-3 as an Example.)

Delay evaluation
Outage probability evaluation
Simulation correctness evaluation

3.1. Delay evluation:

Access delay in our simulation is defined as the time interval between the time when the device transmits the first RA preamble and the time when the device receives the RAR message.

Following figure illustrates the results of the simulation we performed through the aforementioned scenario.

3.2. Outage probability evaluation:

The outage probability is defined as the probability that the device unable to successfully receive the RAR message after the number of RA preambles it transmitted has reached the maximum transmission limit.

Following figure illustrates the results of the simulation we performed through the aforementioned scenario.

3.3. Simulation correctness evaluation

We want to verify the CE level mechanism; therefore we run this evaluation.

First we assume 200 UEs start with CE level 0 and allocated randomly. Then these UEs start RA, if CE level mechanism works in our works, the correspondense of UEs delay time and CE level will follow table II.

Following figure is the simulation results. The figure shows that UEs are allocated in the delay time interval as we expected.