# Enhancing the 3 GPP V2X Architecture with Information-Centric Networking
## 6 Evaluation Methodology
### Performance Metrics  
The _total number of transmitted Interest packets in the network_ was derived to account for the original Interests generated by the consumers and transmitted in the uplink direction towards the eNodeB, as well as the Interests forwarded in downlink by the eNodeB for a cell-wide dissemination.  
To get more insights into the allocated radio resources for the aforementioned Interest packets, the _number of RBs per Interest_ was also quantified, representing the total number of RBs needed to accommodate the Interest packets transmitted by all consumers and sent over the LTE-Uu interface, in UL and DL directions separately. The number of RBs for carrying an Interest was derived according to the packet size and the modulation and coding scheme (MCS) index, as reported in [7]. Longer packets and more robust MCS indexes require a higher number of RBs. The number of RBs required for UL and DL directions are different, since different MCS indexes apply to unicast and multicast transmission, respectively. An MCS index equal to 11 was assumed on the UL to achieve a good trade-off between reliability and RB usage. Multicasting in the DL direction needs a more robust MCS, hence an MCS index equal to 8 was assumed, similar to the study in [36].  
The _average Interest dissemination latency_ was computed as the time since a UE issues an Interest packet until the packet is received by the UEs in the cell, after the DL multicasting by the eNodeB. More in detail, for our proposal, the metric was derived accounting for the following contributions (see Table 2): (i) the processing delay (\(T_{tx,p}\)) at the transmitter UE for the Interest generation; (ii) the time to undergo the dynamic scheduling procedure for an UL transmission grant (\(T_{sched}\)), which also includes the waiting time for the SR opportunity (\(T_{SR}\)) that is a varying parameter in our simulations (\(T_{SR}\) depends on the network load; it tends to be longer if the eNodeB has many connected UEs to schedule on the Physical Uplink Control Channel (PUCCH) [40]); (iii) the Interest transmission time over the LTE-Uu interface in the UL direction (\(T_{tx,I}\)); (iv) the decoding latency (\(T_{dec,eNB}\)) and the buffering delay that considers the \(T_{MSP}\) periodicity, at the eNodeB; (v) the Interest transmission time in the DL direction (\(T_{tx,I}\)); and (vi) the decoding (\(T_{dec,ILE}\)) and processing delays (\(T_{rx,p}\)) at the upper layer at receiving UEs. For the baseline solution, instead, the processing time at the V2X AS to trigger multicast procedures was added to the above parameters and named \(T_{edge}\). It is a varying parameter in our simulations.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Notation** & **Value** \\ \hline Transmission processing delay & \(T_{tx,p}\) & 1 ms \\ Scheduling procedure delay & \(T_{sched}\) & 8 ms \\ Waiting time for the SR opportunity & \(T_{SR}\) & Varying \\ Interest transmission time in both UL/DL & \(T_{tx,I}\) & 1 ms \\ Decoding delay at the eNodeB & \(T_{dec,eNB}\) & 1 ms \\ MCH Scheduling Period & \(T_{MSP}\) & 10 ms \\ Decoding delay at the receiver UE & \(T_{dec,UE}\) & 1.5 ms \\ Application-layer receiver processing & \(T_{rx,p}\) & 3 ms \\ Processing time at the V2X AS & \(T_{edge}\) & Varying \\ \hline \hline \end{tabular}
\end{table}
Table 2: Simulation settings.