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Wi-Fi direct to enable wireless connection between
cell phones and car computers. This feature makes
them more user-friendly by alleviating the need for
wired connection (e.g., USB).
Currently, the number of cars equipped with
WLAN is minimal and is restricted to premium-
priced automobiles. This exclusivity will likely
change relatively soon due to the attractiveness of
WLAN for various applications and the availability of
high supported data rate. According to a report from
GSMA (Sbd, 2012), all new cars will have WLAN by
2025. Consequently, millions of new overlapped ba-
sic subscriber sets (OBSSs) will coexist with current
networks, moreover they are mobile with different
speeds, which makes any kind of network planning
not possible. Unlike indoor scenarios (e.g. offices,
homes), interference between vehicle WLANs is ex-
tremely high due to weak attenuation of car bodies.
Simulations and measurements in (Blesinger et al.,
2013; Blesinger et al., 2012) show that the attenu-
ation of car bodies and windows is very low; mean
path loss does not exceed 85 dB at 50 m distance
around the car. This demonstrates the severity of
coexistence problems in this domain. Several fac-
tors affect path loss (e.g., antenna position and win-
dow type), which should be taken into account by
car manufacturers. Mutual interference between con-
current 802.11 systems in cars is studied in (Pfeif-
fer et al., 2014). Measurements validate the notion
that the achieved throughput is strongly affected by
the WLAN connection in a neighboring car. When
both 2.4 GHz and 5 GHz ISM bands are considered,
the results show that the interference in the 2.4 GHz
band is higher due to the lower path loss. A study on
the effectiveness of WLAN in vehicles is presented in
(Heddebaut et al., 2004). The objective was to charac-
terize radio frequency (0.7-6 GHz) propagation inside
vehicles. Measurements show that mean attenuation
ranges from a few decibel to more than 40 dB, de-
pending on the antenna positions. As such, good link
quality for WLAN inside the vehicle should not be
difficult to achieve. In (Kukolev et al., 2015), chan-
nel measurements are conducted inside the vehicle in
the frequency band 5.8 GHz. The primary focus is
centered on IEEE 802.11p standard for both intra-
vehicle and out-of-vehicle environments. The mea-
sured power delay profile (PDF) is described using a
double exponential model; delay spread is small re-
sulting in negligible effect on inter-symbol interfer-
ence (ISI).
In (Lin et al., 2013), a performance study of intra-
vehicle wireless sensor networks (IVWSN) based on
Bluetooth low energy and ZigBee under Wi-Fi and
Bluetooth interference is presented; performance of
both IVWSNs significantly degrades when Wi-Fi in-
terference is introduced. Although the interference
from the surrounding networks is not considered, it
will definitely increase its influence. In previous
work (Mourad et al., 2016), test drives were con-
ducted to investigate WLAN performance in the ve-
hicles. Highway and city center test drives in Ger-
many demonstrate that achieved throughput inside
the car under test is strongly affected by interference
from surrounding networks. Currently, WLANs are
primarily found in offices, homes, and public areas,
as noted earlier, the number of cars equipped with
WLAN is still limited.
In this work, the focus is on WLAN used for info-
tainment applications in vehicles, which is expected
to be widely spread before the vehicular Ad-Hoc net-
work (VANET). Having WLANs in vehicles will es-
calate the coexistence problem in the ISM bands. A
consequence of millions of new mobile OBSSs, per-
formance of the surrounding fixed Hotspots will be
strongly affected. The high density of devices in ve-
hicles and their mobility, in addition to low inser-
tion loss between neighboring cars make this domain
unique.
Wi-Fi has been studied in various indoor/outdoor
scenarios and under many attenuation scenarios.
However, studies of vehicular environment are lim-
ited. Consequently, this paper provides a first step into
investigating Wi-Fi performance in realistic vehicle
coexistence scenario. The main contribution of this
paper is to study how the WLANs in two neighboring
cars affect each other and to discuss solutions lever-
aging the most recent WLAN standard –802.11n– at
2.4 GHz. To accomplish this, two cars are parked
near to each other and two WLANs are established
in them. Throughput and power values are collected
and analyzed. Both TPC and MIMO techniques are
discussed.
The IEEE 802 community has recently recognized
this issue in the sake of increased demand by car man-
ufacturers. A new study group, namely wireless au-
tomotive coexistence, has been established under the
working group 802.19. The groups effort focuses on
wireless coexistence, optimizing the 802.11 and Blue-
tooth parameter settings for the automotive domain.
The remainder of this paper is organized as fol-
lows. Section 2 presents briefly the IEEE 802.11
standards family. Section 3 describes the measure-
ments setup and the baseline, while section 4 shows
the measurement results. In section 5, the results are
discussed, and the paper is concluded in section 6.
VEHITS 2017 - 3rd International Conference on Vehicle Technology and Intelligent Transport Systems
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