# Performance Analysis of the IEEE 802.11p Multichannel MAC Protocol in Vehicular Ad Hoc Networks
## 5 Model Validation and Numerical Analysis  
In this section, the proposed analytical model is applied to a specific VANETs environment for the evaluation of the performance of reliability and effectiveness of the multichannel defined in the IEEE 1609.4 standard, in terms of packet transmission delay, PRR and throughput. We adopt VISSIM [47] and NS-2 simulator [48] for road traffic and network simulations, respectively. Moreover, we implement 802.11e EDCA [49] developed by the TKN group in the Technical University of Berlin. Some parts of original codes have been modified according to the IEEE 802.11p and the IEEE 1609.4 standard. The simulation scenario is on a 6-km-long highway with one lane in each direction as shown in Figure 4. Every vehicle has a GPS and a single-radio WAVE communication device with parameters shown in Table 4. With regard to ACs assignment to safety-related packets and WSA packets, we refer to [20] to set the values of \(W_{e}\), \(W_{s,0}\), AIFSN[0] and AIFSN[1]. The simulation scenario description is given in Table 5. All nodes can act as both service providers and service users. The vehicle density is varied from 0.01 to 0.08. Due to the performance analysis in terms of throughput, this model focuses on the effect of fixed switching defined in the IEEE 1609.4 standard on throughput versus the \(\gamma\)-varying multichannel scheme, and thus we set \(p_{ber}\) equal to zero on the SCHs. Figure 9 shows the packet transmission delay and PRR on the CCH, and the throughput on the SCHs under varied vehicle density. We change the channel data rate, packet arrival rate, bit error rate and the payload of safety-related packets. The parameter configurations are: 1 \(R_{d}\) = 6 Mbps, \(\lambda_{e}=\lambda_{s}\) = 5 packets/s, \(p_{ber}=10^{-5}\), \(L_{e}\) = 200 Bytes, \(L_{s}\) = 160 bits, \(L_{data}\) = 2000 Bytes; 2 \(R_{d}\) = 12 Mbps, \(\lambda_{e}=\lambda_{s}\) = 5 packets/s, \(p_{ber}=10^{-5}\), \(L_{e}\) = 200 Bytes, \(L_{s}\) = 160 bits, \(L_{data}\) = 2000 Bytes; 3 \(R_{d}\) = 12 Mbps, \(\lambda_{e}=\lambda_{s}\) = 10 packets/s, \(p_{ber}=10^{-5}\), \(L_{e}\) = 100 Bytes, \(L_{s}\) = 160 bits, \(L_{data}\) = 2000 Bytes; and 4 \(R_{d}\) = 6 Mbps, \(\lambda_{e}=\lambda_{s}\) = 5 packets/s, \(p_{ber}=0\), \(L_{e}\) = 200 Bytes, \(L_{s}\) = 160 bits, \(L_{data}\) = 2000 Bytes. It can be seen that analytical and simulation results match well. According to the results in Figure 9, we can observe that the packet transmission delay for the safety-related messages meets the real-time requirement, however, the PRR for the safety-related messages and the throughput for the non-safety messages rapidly decreases when the vehicle density changes from smooth to jammed. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Frequency & 5.9 GHz \\ Modulation & QPSK, 16 QAM \\ Signal bandwidth & 10 MHz \\ Channel data rate (\(R_{d}\)) & 6, 12 Mbps \\ \(W_{e}\) & 8 \\ \(W_{s,0}\) & 16 \\ AIFSN[0] & 3 \\ AIFSN[1] & 6 \\ \(m^{\prime}\) & 2 \\ \(R\)etry limit (\(m\)) & 4 \\ \(SIFS\) & 32 us \\ \(DIFS\) & 64 us \\ Slot time (\(\sigma\)) & 13 us \\ Propagation delay (\(\delta\)) & 1 us \\ \hline \end{tabular}
\end{table} 
Table 4: Parameter for communications in DSRC. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Highway length & 6000 m \\ Number of lanes & 1 lane in each direction \\ Vehicle density (\(\beta\)) & 0.01 to 0.08 vehicles/m \\ Transmission range (\(R\)) & 300 m \\ Carrier sensing range (\(L_{cs}\)) & 400 m \\ Packet arrival rate (\(\lambda_{e}\)), (\(\lambda_{s}\)) & 5 packets/s \\ The bit error rate (\(p_{ber}\)) & \(10^{-5}\) \\ MAC-layer header length (\(H_{MAC}\)) & 256 bits \\ Physical-layer header length (\(H_{PHY}\)) & 192 bits \\ An ACK packet size (\(L_{ACK}\)) & \(H_{PHY}\) + 112 bits \\ The payload of a safety packet (\(L_{e}\)) & 200 Bytes \\ The payload of a WSA packet (\(L_{s}\)) & 160 bits \\ The payload of a non-safety packet (\(L_{data}\)) & 2000 Bytes \\ \hline \end{tabular}
\end{table} 
Table 5: Parameter for road traffic.