# Experimental Demonstration of MmWave Vehicle-to-Vehicle Communications Using IEEE 802.11 ad
## 4 Experimental Configuration  
### IEEE 802.11 ad  
Previously, the mmWave technologies were studied and standardized for WLANs, which are primarily used for home appliances and hand-held devices at indoor environments. IEEE 802.15.3 task group 3c (TG3c) [55] and IEEE 802.11 ad [56] standards specify physical and MAC layer protocols at 60 GHz unlicensed bands. The IEEE 802.11 ad defines operations between an access point (AP) and a mobile stations (STA) using a two-phase beam training (i.e., association beamforming training (A-BFT), beam refinement protocol (BRP)), in which both detect a transmitting or receiving sector approximately by sweeping all directions during the beacon header interval (BHI); subsequently beam refinement is performed by BRP during the service period (SP) of data transmission interval (DTI). Additionally, IEEE 802.11 ad supports a relay mode for link blockage between the AP and the STA. During the SPs that are set by the AP for searching a relay STA, a source and destination STA exchange the BRP packets with the neighboring candidate relay STAs nearby. Subsequently, the source STA requests measurement reports from several possible relays with good channel quality (i.e., high signal to noise ratio (SNR)), which include the link state information to both the source and destination STAs. Then, the source STA finally selects the best relay that has the highest SNR in both links.  
For the GiV2V testbed used in this study, we used off-the-shelf modules of IEEE 802.11 ad [56]. The IEEE 802.11 ad standard supports mmWave communications at 60 GHz unlicensed bands and was developed for a considerable time after the completion of the standard. The IEEE 802.11 ad standard defines the specification of a physical and MAC protocol for an Access Point (AP) and a directional multi-gigabit (DMG) mobile station (STA). In addition, the relay DMG STA (RDS) operation is specified for the NLOS environment. IEEE 802.11 ad has six channels with 2.1 GHz bandwidth each from 58.32 to 69.12 GHz spectrum, which allow different modulations with single or multiple carriers; the single carrier can achieve data rate from 385 Mbps to 4.62 Gbps and multiple carriers (such as orthogonal frequency-division multiplexing(OFDM)) can achieve data rate from 693 Mbps to 6.75 Gbps according to the MCSs.  
In this study, we utilized the commercial products developed by Tensorcom [57] shown in Figure 3, which achieves the physical/MAC protocol stack of IEEE 802.11 ad and are being used for communications between smart phones, televisions, laptops and their supplementary devices. The performance features of the Tensorcom 802.11 ad module are noted listed in Table 2. With these parameters, expected theoretical radio range \(d\) can be calculated with a given pathloss exponent using Equation (4) from Section 3.2. The reachable distances according at the required threshold \(T=-68\) dBm for MCS1 are presented in Table 3 with varying pathloss exponents.  
\begin{table}
\begin{tabular}{l l} \hline EIRP & 12.5 dBm \\ IL & 7.5 dB \\ G & 7.5 dBi \\ MIMO & 2 \(\times\) 2 \\ BW & 1.76 GHz \\ MCS & 0–7 \\ \hline \end{tabular}
\end{table}
Table 2: Tensorcom 802.11 ad module features.