IPv6 Wireless Access in Vehicular Environments (IPWAVE): Problem Statement and Use Cases
Department of Computer Science and Engineering
Sungkyunkwan University2066 Seobu-Ro, Jangan-GuSuwonGyeonggi-Do16419Republic of Korea+82 31 299 4957+82 31 290 7996pauljeong@skku.eduhttp://iotlab.skku.edu/people-jaehoon-jeong.php
Internet
IPWAVE Working GroupInternet-Draft
This document discusses the problem statement and use cases of
IPv6-based vehicular networking for Intelligent Transportation Systems (ITS).
The main scenarios of vehicular communications are vehicle-to-vehicle (V2V),
vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X) communications.
First, this document explains use cases using V2V, V2I, and V2X networking.
Next, for IPv6-based vehicular networks, it makes a gap analysis of current
IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management, and
Security & Privacy).
Vehicular networking studies have mainly focused on improving road
safety and efficiency, and also enabling entertainment in vehicular
networks. To proliferate the use cases of vehicular networks,
several governments and private organizations have committed to
allocate dedicated spectrum for vehicular communications.
The Federal Communications Commission (FCC) in the US allocated wireless
channels for Dedicated Short-Range Communications (DSRC)
in the Intelligent Transportation Systems (ITS) with the frequency band of
5.850 - 5.925 GHz (i.e., 5.9 GHz band). In November 2020, the FCC adjusted
the lower 45 MHz (i.e., 5.850 - 5.895 GHz) of the 5.9 GHz band for
unlicensed use instead of DSRC-dedicated use
. DSRC-based wireless communications
can support vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I),
and vehicle-to-everything (V2X) networking.
The European Union (EU) allocated radio spectrum for safety-related and
non-safety-related applications of ITS with the frequency band of
5.875 - 5.905 GHz, as part of the Commission Decision 2008/671/EC
. Most other countries and regions in
the world have adopted the 5.9 GHz band for vehicular networks, though
different countries use different ways to divide the band into channels.
For direct inter-vehicular wireless connectivity, IEEE has amended
standard 802.11 (commonly known as Wi-Fi) to enable safe driving services based on DSRC
for the Wireless Access in Vehicular Environments (WAVE)
system. The Physical Layer (L1) and Data Link Layer (L2) issues are addressed
in IEEE 802.11p
for the PHY and MAC of the DSRC, while IEEE 1609.2
covers security aspects, IEEE 1609.3
defines related services at network and transport layers, and IEEE 1609.4
specifies the multichannel operation.
IEEE 802.11p was first a separate amendment, but was later rolled into
the base 802.11 standard (IEEE 802.11-2012) as IEEE 802.11 Outside the Context
of a Basic Service Set (OCB) in 2012 .
3GPP has standardized Cellular Vehicle-to-Everything (C-V2X) communications
to support V2X in LTE mobile networks (called LTE V2X)
and V2X in 5G mobile networks (called 5G V2X) .
With C-V2X, vehicles can directly communicate with each other without
relay nodes (e.g., eNodeB in LTE and gNodeB in 5G).
Along with these WAVE standards and C-V2X standards, regardless of a wireless
access technology under the IP stack of a vehicle, vehicular networks can
operate IP mobility with IPv6 and Mobile IPv6
protocols (e.g., Mobile IPv6 (MIPv6) , Proxy MIPv6
(PMIPv6) , Distributed Mobility Management (DMM)
, Network Mobility (NEMO)
, and Locator/ID Separation Protocol (LISP)
.
In addition, ISO has approved a standard specifying the IPv6 network
protocols and services to be used for Communications Access for Land Mobiles
(CALM) .
This document describes use cases and a problem statement about
IPv6-based vehicular networking for ITS, which is named IPv6 Wireless Access in
Vehicular Environments (IPWAVE).
First, it introduces the use cases for using V2V, V2I, and V2X networking
in ITS.
Next, for IPv6-based vehicular networks, it makes a gap analysis of
current IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility
Management, and Security & Privacy) so that those protocols
can be tailored to IPv6-based vehicular networking.
Thus, this document is intended to motivate development of
key protocols for IPWAVE.
This document uses the terminology described in .
In addition, the following terms are defined below:
Context-Awareness: A vehicle can be aware of spatial-temporal mobility
information (e.g., position, speed, direction, and acceleration/deceleration)
of surrounding vehicles for both safety and non-safety uses through sensing
or communication .
DMM: "Distributed Mobility Management"
.
Edge Computing Device (ECD): It is a computing device (or server)
at edge for vehicles and vulnerable road users. It co-locates with
or connects to an IP-RSU, which has a powerful computing capability
for different kinds of computing tasks, such as image processing
and classification.
Edge Network (EN): It is an access network that has an IP-RSU for wireless
communication with other vehicles having an IP-OBU and wired communication
with other network devices (e.g., routers, IP-RSUs, ECDs, servers, and MA).
It may have a global navigation satellite system (GNSS), such as Global
Positioning System (GPS), radio receiver for its
position recognition and the localization service for the sake of vehicles.
IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a computer
situated in a vehicle (e.g., car, bicycle, autobike,
motorcycle, and a similar one), which has a basic processing ability
and can be driven by a low-power CPU (e.g., ARM).
It has at least one IP interface that runs
in IEEE 802.11-OCB and has an "OBU" transceiver.
Also, it may have an IP interface that runs in Cellular V2X
(C-V2X) .
It can play the role of a router connecting multiple computers (or
in-vehicle devices) inside a vehicle. See the definition of the term
"IP-OBU" in .
IP-RSU: "IP Roadside Unit": An IP-RSU is situated along the road. It has
at least two distinct IP-enabled interfaces. The wireless PHY/MAC layer of
at least one of its IP-enabled interfaces is configured to operate in
802.11-OCB mode. An IP-RSU communicates with the IP-OBU over an 802.11
wireless link operating in OCB mode. Also, it may have a third
IP-enabled wireless interface running in 3GPP C-V2X in addition to the
IP-RSU defined in . An IP-RSU is similar to an
Access Network Router (ANR), defined in , and
a Wireless Termination Point (WTP), defined in .
See the definition of the term "IP-RSU" in .
LiDAR: "Light Detection and Ranging". It is a scanning device
to measure a distance to an object by emitting pulsed laser light and
measuring the reflected pulsed light.
Mobility Anchor (MA): A node that maintains IPv6 addresses and
mobility information of vehicles in a road network to support
their IPv6 address autoconfiguration and mobility management
with a binding table.
An MA has End-to-End (E2E) connections (e.g., tunnels) with
IP-RSUs under its control for the address autoconfiguration
and mobility management of the vehicles. This MA is similar to
a Local Mobility Anchor (LMA) in PMIPv6
for network-based mobility management.
OCB: "Outside the Context of a Basic Service Set - BSS". It is a mode
of operation in which a Station (STA) is not a member of a BSS and does not
utilize IEEE Std 802.11 authentication, association, or data
confidentiality .
802.11-OCB: It refers to the mode specified in IEEE Std 802.11-2016
when the MIB attribute dot11OCBActivited
is 'true'.
Platooning: Moving vehicles can be grouped together to reduce
air-resistance for energy efficiency and reduce the number of drivers such
that only the leading vehicle has a driver, and the other vehicles are autonomous
vehicles without a driver and closely follow the leading vehicle .
Traffic Control Center (TCC): A system that manages road
infrastructure nodes (e.g., IP-RSUs, MAs, traffic signals, and
loop detectors), and also maintains vehicular traffic statistics
(e.g., average vehicle speed and vehicle inter-arrival time per
road segment) and vehicle information (e.g., a vehicle's identifier,
position, direction, speed, and trajectory as a navigation path).
TCC is part of a vehicular cloud for vehicular networks.
Urban Air Mobility (UAM): It refers to using lower-altitude aircraft to
transport passengers or cargo in urban and suburban areas. The carriers
used for UAM can be manned or unmanned vehicles, which can include
traditional helicopters, electrical
vertical-takeoff-and-landing aircraft (eVTOL), and unmanned aerial
vehicles (UAV).
Vehicle: A Vehicle in this document is a node that has an IP-OBU
for wireless communication with other vehicles and IP-RSUs.
It has a GNSS radio navigation receiver for efficient navigation.
Any device having an IP-OBU and a GNSS receiver (e.g., smartphone and
tablet PC) can be regarded as a vehicle in this document.
Vehicular Ad Hoc Network (VANET): A network that consists of vehicles
interconnected by wireless communication.
Two vehicles in a VANET can communicate with each other using
other vehicles as relays even where they are out of one-hop
wireless communication range.
Vehicular Cloud: A cloud infrastructure for vehicular networks, having
compute nodes, storage nodes, and network forwarding elements
(e.g., switch and router).
V2D: "Vehicle to Device". It is the wireless communication between
a vehicle and a device (e.g., smartphone and IoT device).
V2P: "Vehicle to Pedestrian". It is the wireless communication between
a vehicle and a pedestrian's device (e.g., smartphone and IoT device).
V2I2V: "Vehicle to Infrastructure to Vehicle". It is the wireless
communication between a vehicle and another vehicle via an
infrastructure node (e.g., IP-RSU).
V2I2X: "Vehicle to Infrastructure to Everything". It is the wireless
communication between a vehicle and another entity (e.g., vehicle,
smartphone, and IoT device) via an infrastructure node (e.g., IP-RSU).
V2X: "Vehicle to Everything". It is the wireless communication between
a vehicle and any entity (e.g., vehicle, infrastructure node,
smartphone, and IoT device), including V2V, V2I, and V2D.
VMM: "Vehicular Mobility Management". It is an IPv6-based mobility
management for vehicular networks.
VND: "Vehicular Neighbor Discovery". It is an IPv6 ND extension for
vehicular networks.
VSP: "Vehicular Security and Privacy". It is an IPv6-based security and
privacy term for vehicular networks.
WAVE: "Wireless Access in Vehicular Environments" .
This section explains use cases of V2V, V2I, and V2X networking.
The use cases of the V2X networking exclude the ones of the V2V
and V2I networking, but include Vehicle-to-Pedestrian (V2P) and
Vehicle-to-Device (V2D).
IP is widely used among popular end-user devices (e.g.,
smartphone and tablet) in the Internet. Applications
(e.g., navigator application) for those devices can be extended
such that the V2V use cases in this section can work with IPv6
as a network layer protocol and IEEE 802.11-OCB as a link layer
protocol. In addition, IPv6 security needs to be extended to
support those V2V use cases in a safe, secure, privacy-preserving
way.
The use cases presented in this section serve as the description and
motivation for the need to augment IPv6 and its protocols to facilitate
"Vehicular IPv6".
summarizes the overall problem statement and IPv6 requirements.
Note that the adjective "Vehicular" in this document is used to
represent extensions of existing protocols such as IPv6 Neighbor
Discovery, IPv6 Mobility Management (e.g., PMIPv6
and DMM ), and
IPv6 Security and Privacy Mechanisms rather than new
"vehicular-specific" functions.
The use cases of V2V networking discussed in this section include
Context-aware navigation for safe driving and collision avoidance;Collision avoidance service of end systems of Urban Air
Mobility (UAM);Cooperative adaptive cruise control in a roadway;Platooning in a highway;Cooperative environment sensing.
The above use cases are examples for using V2V networking, which can
be extended to other terrestrial vehicles, river/sea ships,
railed vehicles, or UAM end systems.
Context-Aware Safety Driving (CASD) navigator
can help drivers to drive safely by alerting them to
dangerous obstacles and situations. That is, a CASD navigator displays
obstacles or neighboring vehicles relevant to possible collisions in
real-time through V2V networking. CASD provides vehicles with a
class-based automatic safety action plan, which considers three
situations, namely, the Line-of-Sight unsafe, Non-Line-of-Sight
unsafe, and safe situations. This action plan can be put into action
among multiple vehicles using V2V networking.
A collision avoidance service of UAM end systems in air can be envisioned
as a use case in air vehicular environments
. This use case is similar
to the context-aware navigator for terrestrial vehicles.
Through V2V coordination, those UAM end systems (e.g., drones) can avoid
a dangerous situation (e.g., collision) in three-dimensional space rather
than two-dimensional space for terrestrial vehicles.
Also, UAM end systems (e.g., flying car)
with only a few meters off the ground can communicate with terrestrial vehicles
with wireless communication technologies (e.g., DSRC, LTE, and C-V2X).
Thus, V2V means any vehicle to any vehicle, whether the vehicles are
ground-level or not.
Cooperative Adaptive Cruise Control (CACC)
helps individual vehicles to adapt their
speed autonomously through V2V communication among vehicles according
to the mobility of their predecessor and successor vehicles in an
urban roadway or a highway. Thus, CACC can help adjacent vehicles to
efficiently adjust their speed in an interactive way through V2V
networking in order to avoid a collision.
Platooning allows a series (or group) of
vehicles (e.g., trucks) to follow each other very closely.
Trucks can use V2V communication in addition to
forward sensors in order to maintain constant clearance between two
consecutive vehicles at very short gaps (from 3 meters to 10 meters).
Platooning can maximize the throughput of vehicular traffic in
a highway and reduce the gas consumption because the leading vehicle
can help the following vehicles to experience less air resistance.
Cooperative-environment-sensing use cases suggest that vehicles can
share environmental information (e.g., air pollution, hazards/obstacles,
slippery areas by snow or rain, road accidents, traffic congestion,
and driving behaviors of neighboring vehicles) from various
vehicle-mounted sensors, such as radars, LiDARs, and cameras, with other
vehicles and pedestrians.
introduces millimeter-wave
vehicular communication for massive automotive sensing.
A lot of data can be generated by those sensors, and
these data typically need to be routed to different destinations.
In addition, from the perspective of driverless vehicles, it is
expected that driverless vehicles can be mixed with driver-operated
vehicles. Through cooperative environment sensing, driver-operated
vehicles can use environmental information sensed by driverless vehicles
for better interaction with the other vehicles and environment.
Vehicles can also share their intended maneuvering information (e.g.,
lane change, speed change, ramp in-and-out, cut-in, and abrupt braking)
with neighboring vehicles.
Thus, this information sharing can help the vehicles behave as more
efficient traffic flows and minimize unnecessary acceleration and
deceleration to achieve the best ride comfort.
To support applications of these V2V use cases, the required functions
of IPv6 include IPv6-based packet exchange in both control and data planes,
and secure, safe communication
between two vehicles. For the support of V2V under multiple radio
technologies (e.g., DSRC and 5G V2X), refer to
.
The use cases of V2I networking discussed in this section include
Navigation service;Energy-efficient speed recommendation service;Accident notification service;Electric vehicle (EV) charging service;UAM navigation service with efficient battery charging.
A navigation service, for example, the Self-Adaptive Interactive
Navigation Tool (SAINT) , using V2I networking
interacts with a TCC for the large-scale/long-range road traffic
optimization and can guide individual vehicles along appropriate
navigation paths in real time.
The enhanced version of SAINT can
give fast moving paths to emergency vehicles (e.g., ambulance
and fire engine) to let them reach an accident spot while redirecting other vehicles
near the accident spot into efficient detour paths.
Either a TCC or an ECD can recommend an energy-efficient speed to a vehicle
that depends on its traffic environment and traffic signal scheduling
. For example, when a vehicle approaches
an intersection area and a red traffic light for the vehicle becomes
turned on, it needs to reduce its speed to save fuel consumption. In
this case, either a TCC or an ECD, which has the up-to-date
trajectory of the vehicle and the traffic light schedule, can notify
the vehicle of an appropriate speed for fuel efficiency.
studies fuel-efficient route
and speed plans for platooned trucks.
The emergency communication between accident vehicles (or emergency
vehicles) and a TCC can be performed via either IP-RSU, 4G-LTE or
5G networks.
The First Responder Network Authority (FirstNet)
is provided by the US government to
establish, operate, and maintain an interoperable public safety
broadband network for safety and security network services, e.g.,
emergency calls. The construction of the nationwide FirstNet network
requires each state in the US to have a Radio Access Network (RAN)
that will connect to the FirstNet's network core.
The current RAN is mainly constructed using 4G-LTE for the communication
between a vehicle and an infrastructure node (i.e., V2I)
, but it is expected that DSRC-based vehicular
networks will be available for V2I and V2V in the near future.
An equivalent project in Europe is called Public Safety Communications
Europe (PSCE) , which is developing a network for
emergency communications.
An EV charging service with V2I can facilitate the efficient battery
charging of EVs. In the case where an EV charging station is connected to
an IP-RSU, an EV can be guided toward the deck of the EV charging station
or be notified that the charging station is out of service
through a battery charging server connected to the IP-RSU. In addition to
this EV charging service, other value-added services (e.g.,
firmware/software update over-the-air and media streaming)
can be provided to an EV
while it is charging its battery at the EV charging station.
For a UAM navigation service, an efficient battery charging plan can
improve the battery charging schedule of UAM end systems (e.g., drone)
for long-distance flying .
For this battery charging schedule, a UAM end system can communicate with
a cloud server via an infrastructure node (e.g., IP-RSU).
This cloud server can coordinate the battery charging
schedules of multiple UAM end systems for their efficient navigation path,
considering flight time from their current position to a battery charging
station, waiting time in a waiting queue at the station, and battery
charging time at the station.
In some scenarios such as vehicles moving in highways or staying in parking
lots, a V2V2I network is necessary for vehicles to access the Internet
since some vehicles may not be covered by an IP-RSU. For those vehicles,
a few relay vehicles can help to build the Internet access. For the
nested NEMO described in
, hosts inside a vehicle shown in
for the case of V2V2I may have the same issue in the nested NEMO scenario.
To better support these use cases, the existing IPv6 protocol must be
augmented either through protocol changes or by including a new adaptation
layer in the architecture that efficiently maps IPv6 to a diversity of
link layer technologies.
Augmentation is necessary to support wireless multihop V2I communications
in a highway where RSUs are sparsely deployed, so a vehicle can reach the
wireless coverage of an IP-RSU through the multihop data forwarding of
intermediate vehicles as packet forwarders. Thus, IPv6 needs to be extended for multihop V2I
communications.
To support applications of these V2I use cases, the required functions
of IPv6 include IPv6 communication enablement with neighborhood discovery
and IPv6 address management, reachability with adapted network models and
routing methods, transport-layer session continuity, and secure, safe
communication between a vehicle and an infrastructure node (e.g., IP-RSU)
in the vehicular network.
The use case of V2X networking discussed in this section is
for a vulnerable road user (VRU) (e.g., pedestrian and cyclist)
protection service.
Note that the application area of this use case is currently limited
to a specific environment, such as construction sites, plants, and
factories, since not every VRU (e.g., children) in a public area
(e.g., streets) is equipped with a smart device (e.g., smartphone,
smart watch, and tablet).
A VRU protection service, such as Safety-Aware Navigation
Application (SANA) , using V2I2P networking
can reduce the collision of a vehicle and a pedestrian carrying a
smartphone equipped with a network device for wireless communication
(e.g., Wi-Fi, DSRC, 4G/5G V2X, and BLE) with an IP-RSU.
Vehicles and pedestrians can also
communicate with each other via an IP-RSU. An edge computing device
behind the IP-RSU can collect the mobility information from vehicles
and pedestrians, compute wireless communication scheduling for the
sake of them. This scheduling can save the battery of each
pedestrian's smartphone by allowing it to work in sleeping mode
before the communication with vehicles, considering their mobility.
The location information of a VRU from a smart device
(e.g., smartphone) is multicasted only to the nearby vehicles.
The true identifiers of a VRU's smart device shall be protected,
and only the type of the VRU, such as pedestrian, cyclist, and
scooter, is disclosed to the nearby vehicles.
For Vehicle-to-Pedestrian (V2P), a vehicle can directly communicate
with a pedestrian's smartphone by V2X without IP-RSU relaying.
Light-weight mobile nodes such as bicycles may also communicate
directly with a vehicle for collision avoidance using V2V. Note that
it is true that either a pedestrian or a cyclist may have a higher risk of
being hit by a vehicle if they are not with a smartphone in the current
setting. For this
case, other human sensing technologies (e.g., moving object detection
in images and wireless signal-based human movement detection
) can be
used to provide the motion information of them to vehicles. A vehicle
by V2V2I networking can obtain the motion information of a VRU
via an IP-RSU that either employs or connects to a human
sensing technology.
The existing IPv6 protocol must be augmented through protocol changes
in order to support wireless multihop V2X or V2I2X communications in an
urban road network where RSUs are deployed at intersections, so a vehicle
(or a pedestrian's smartphone) can reach the wireless coverage of an IP-RSU
through the multihop data forwarding of intermediate vehicles (or
pedestrians' smartphones) as packet forwarders. Thus, IPv6 needs to be
extended for multihop V2X or V2I2X communications.
To support applications of these V2X use cases, the required functions
of IPv6 include IPv6-based packet exchange, transport-layer session
continuity, and secure, safe communication between a vehicle and a
pedestrian either directly or indirectly via an IP-RSU, and the
protection of identifiers of either a vehicle or smart device (such as
MAC address and IPv6 address), which is discussed in detail in
.
This section describes the context for vehicular networks
supporting V2V, V2I, and V2X communications.
It describes an internal network within a vehicle or an edge network
(called EN). It explains not only the internetworking between the
internal networks of a vehicle and an EN via wireless links, but also
the internetworking between the internal networks of two vehicles
via wireless links.
* | Mobility Anchor | *
+-------------+ * +-----------------+ *
* ^ *
* | *
* v *
*******************************************
^ ^ ^
| | |
| | |
v v v
+---------+ +---------+ +---------+
| IP-RSU1 |<--------->| IP-RSU2 |<--------->| IP-RSU3 |
+---------+ +---------+ +---------+
^ ^ ^
: : :
+-----------------+ +-----------------+ +-----------------+
| : V2I | | : V2I | | : V2I |
| v | | v | | v |
+--------+ | +--------+ | | +--------+ | | +--------+ |
|Vehicle1|===> |Vehicle2|===>| | |Vehicle3|===>| | |Vehicle4|===>|
+--------+<...>+--------+<........>+--------+ | | +--------+ |
V2V ^ V2V ^ | | ^ |
| : V2V | | : V2V | | : V2V |
| v | | v | | v |
| +--------+ | | +--------+ | | +--------+ |
| |Vehicle5|===> | | |Vehicle6|===>| | |Vehicle7|==>|
| +--------+ | | +--------+ | | +--------+ |
+-----------------+ +-----------------+ +-----------------+
Subnet1 Subnet2 Subnet3
(Prefix1) (Prefix2) (Prefix3)
<----> Wired Link <....> Wireless Link ===> Moving Direction
]]> shows an
example vehicular network architecture for V2I and V2V in
a road network.
The vehicular network architecture contains vehicles
(including IP-OBU), IP-RSUs, Mobility Anchor, Traffic Control
Center, and Vehicular Cloud as components.
These components are not mandatory, and they can be deployed
into vehicular networks in various ways. Some of them (e.g.,
Mobility Anchor, Traffic Control Center, and Vehicular Cloud) may
not be needed for the vehicular networks according to target use
cases in .
Existing network architectures, such as the network architectures of
PMIPv6 , RPL (IPv6 Routing Protocol for Low-Power
and Lossy Networks) , and AERO/OMNI
, can be extended to a
vehicular network architecture for multihop V2V, V2I, and V2X, as
shown in .
Refer to for the
detailed discussion on multihop V2X networking by RPL and OMNI.
Also, refer to
for the description of how OMNI is designed to support the use of multiple radio
technologies in V2X.
Note that though AERO/OMNI is not actually deployed in the industry,
this AERO/OMNI is mentioned as a possible approach for vehicular
networks in this document.
As shown in , IP-RSUs as
routers and vehicles with IP-OBU
have wireless media interfaces for VANET.
The three IP-RSUs (IP-RSU1, IP-RSU2, and IP-RSU3) are deployed in the road
network and are connected with each other through the wired networks
(e.g., Ethernet).
A Traffic Control Center (TCC) is connected to the Vehicular Cloud for
the management of IP-RSUs and vehicles in the road network.
A Mobility Anchor (MA) may be located in the TCC as a mobility management
controller.
Vehicle2, Vehicle3, and Vehicle4 are wirelessly connected to IP-RSU1,
IP-RSU2, and IP-RSU3, respectively.
The three wireless networks of IP-RSU1, IP-RSU2, and IP-RSU3 can belong to three
different subnets (i.e., Subnet1, Subnet2, and Subnet3), respectively.
Those three subnets use three different prefixes (i.e., Prefix1, Prefix2,
and Prefix3).
Multiple vehicles under the coverage of an IP-RSU share a prefix just as
mobile nodes share a prefix of a Wi-Fi access point in a wireless
LAN. This is a natural characteristic in infrastructure-based wireless
networks. For example, in ,
two vehicles (i.e., Vehicle2, and Vehicle5) can use Prefix 1 to configure
their IPv6 global addresses for V2I communication.
Alternatively, mobile nodes can employ a "Bring-Your-Own-Addresses (BYOA)"
(or "Bring-Your-Own-Prefix (BYOP)") technique using their own IPv6 Unique Local Addresses (ULAs)
over the wireless network.
In wireless subnets in vehicular networks (e.g., Subnet1 and Subnet2
in ), vehicles can
construct a connected VANET (with an arbitrary graph topology) and can
communicate with each other via V2V communication.
Vehicle1 can communicate with Vehicle2 via V2V communication, and
Vehicle2 can communicate with Vehicle3 via V2V communication because
they are within the wireless communication range of each other.
On the other hand, Vehicle3 can communicate with
Vehicle4 via the vehicular infrastructure (i.e., IP-RSU2 and IP-RSU3)
by employing V2I (i.e., V2I2V) communication because they are not
within the wireless communication range of each other.
As a basic definition for IPv6 packets transported over IEEE 802.11-OCB,
specifies several details, including
Maximum Transmission Unit (MTU), frame format, link-local address,
address mapping for unicast and multicast, stateless autoconfiguration, and
subnet structure.
An IPv6 mobility solution is needed for the guarantee of communication
continuity in vehicular networks so that a vehicle's TCP session can be
continued, or UDP packets can be delivered to a vehicle as a destination
without loss while it moves from an IP-RSU's wireless coverage to another
IP-RSU's wireless coverage.
In ,
assuming that Vehicle2 has a TCP session (or a UDP session) with a
correspondent node in the vehicular cloud, Vehicle2 can move from
IP-RSU1's wireless coverage to IP-RSU2's wireless coverage. In this case,
a handover for Vehicle2 needs to be performed by either a host-based
mobility management scheme (e.g., MIPv6 ) or a
network-based mobility management scheme (e.g., PMIPv6
, NEMO , and
AERO ).
This document describes issues in mobility management for vehicular
networks in .
For improving TCP session continuity or successful UDP packet delivery, the
multi-path TCP (MPTCP) or QUIC protocol
can also be used. IP-OBUs, however, may still
experience more session time-out and re-establishment procedures due to
lossy connections among vehicles caused by the high mobility dynamics of
them.
This section discusses the internetworking between a vehicle's
internal network (i.e., mobile network) and an EN's internal
network (i.e., fixed network) via V2I communication.
The internal network of a vehicle is nowadays constructed with
Ethernet by many automotive vendors .
Note that an EN can accommodate multiple routers (or switches)
and servers (e.g., ECDs, navigation server, and DNS server)
in its internal network.
A vehicle's internal network often uses Ethernet to interconnect
Electronic Control Units (ECUs) in the vehicle. The internal
network can support Wi-Fi and Bluetooth to accommodate a driver's
and passenger's mobile devices (e.g., smartphone or tablet).
The network topology and subnetting depend on each vendor's
network configuration for a vehicle and an EN.
It is reasonable to consider interactions between the internal
network of a vehicle and that of another vehicle or an EN.
Note that it is dangerous if the internal network of a vehicle is
controlled by a malicious party. These dangers can include unauthorized
driving control input and unauthorized driving information disclosure to
an unauthorized third party. A malicious party can be a group of
hackers, a criminal group, and a competitor for industrial espionage
or sabotage.
To minimize this kind of risk, an augmented identification and verification
protocol, which has an extra means, shall be implemented based on a basic identity verification process.
These extra means can be certificate-based, biometric, credit-based,
and one-time passcode (OTP) approaches in addition to a used approach
.
The parties of the verification protocol can be from a built-in
verification protocol in the current vehicle, which is pre-installed by a
vehicle vendor. The parties can also be from any verification authorities
that have the database of authenticated users. The security properties
provided by a verification protocol can be identity-related information,
such as the genuineness of an identity, the authenticity of an identity,
and the ownership of an identity .
The augmented identification and verification protocol with extra means can
support security properties such as the identification and verification of
a vehicle, driver, and passenger. First, a credit-based means is to let a
vehicle classify the received messages sent by another host to different
severity levels for driving safety in order to calculate the credit for the
sender. Based on an accumulated credit, a correspondent node can verify
the other party to see whether it is genuine or not. Second, a
certificate-based means includes a user certificate (e.g., X.509
certificate ) to authenticate a vehicle or its
driver. Third, a biometric means includes a fingerprint, face or voice to
authenticate a driver or passenger. Lastly, one-time passcode (called
OTP) means lets another already-authenticated device (e.g., smartphone and
tablet) of a driver or passenger be used to authenticate a driver or
passenger.
(*) +----->| Vehicular Cloud |
(2001:db8:1:1::/64) | | | +-----------------+
+------------------------------+ +---------------------------------+
| v | | v v |
| +-------+ +-------+ | | +-------+ +-------+ |
| | Host1 | |IP-OBU1| | | |IP-RSU1| | Host3 | |
| +-------+ +-------+ | | +-------+ +-------+ |
| ^ ^ | | ^ ^ |
| | | | | | | |
| v v | | v v |
| ---------------------------- | | ------------------------------- |
| 2001:db8:10:1::/64 ^ | | ^ 2001:db8:20:1::/64 |
| | | | | |
| v | | v |
| +-------+ +-------+ | | +-------+ +-------+ +-------+ |
| | Host2 | |Router1| | | |Router2| |Server1|...|ServerN| |
| +-------+ +-------+ | | +-------+ +-------+ +-------+ |
| ^ ^ | | ^ ^ ^ |
| | | | | | | | |
| v v | | v v v |
| ---------------------------- | | ------------------------------- |
| 2001:db8:10:2::/64 | | 2001:db8:20:2::/64 |
+------------------------------+ +---------------------------------+
Vehicle1 (Mobile Network1) EN1 (Fixed Network1)
<----> Wired Link <....> Wireless Link (*) Antenna
]]>
As shown in , as internal
networks, a vehicle's mobile network and an EN's fixed network
are self-contained networks having multiple subnets and having
an edge router (e.g., IP-OBU and IP-RSU) for the communication with
another vehicle or another EN.
The internetworking between two internal networks via V2I communication
requires the exchange of the network parameters and the network
prefixes of the internal networks. For the efficiency, the network
prefixes of the internal networks (as a mobile network) in a
vehicle need to be delegated and configured automatically. Note
that a mobile network's network prefix can be called a Mobile
Network Prefix (MNP) .
also shows the internetworking
between the vehicle's mobile network and the EN's fixed network.
There exists an internal network (Mobile Network1) inside Vehicle1.
Vehicle1 has two hosts (Host1 and Host2), and two routers (IP-OBU1
and Router1). There exists another internal network (Fixed Network1)
inside EN1. EN1 has one host (Host3), two routers (IP-RSU1 and
Router2), and the collection of servers (Server1 to ServerN) for
various services in the road networks, such as the emergency
notification and navigation. Vehicle1's IP-OBU1 (as a mobile router)
and EN1's IP-RSU1 (as a fixed router) use 2001:db8:1:1::/64 for an
external link (e.g., DSRC) for V2I networking.
Thus, a host (Host1) in Vehicle1 can communicate with a server
(Server1) in EN1 for a vehicular service through Vehicle1's moving
network, a wireless link between IP-OBU1 and IP-RSU1, and EN1's fixed
network.
For the IPv6 communication between an IP-OBU and an IP-RSU or between
two neighboring IP-OBUs, they need to know the network parameters,
which include MAC layer and IPv6 layer information.
The MAC layer information includes wireless link layer parameters,
transmission power level, and the MAC address of an external network
interface for the internetworking with another IP-OBU or IP-RSU.
The IPv6 layer information includes the IPv6 address and network
prefix of an external network interface for the internetworking with
another IP-OBU or IP-RSU.
Through the mutual knowledge of the network parameters of
internal networks, packets can be transmitted between the vehicle's moving
network and the EN's fixed network. Thus, V2I requires an efficient
protocol for the mutual knowledge of network parameters. Note that
from a security point of view, a perimeter-based policy enforcement
can be applied to protect parts of the internal network of a vehicle.
As shown in , the addresses
used for IPv6 transmissions over the wireless link interfaces for
IP-OBU and IP-RSU can be link-local IPv6 addresses, ULAs, or global
IPv6 addresses. When IPv6 addresses are used, wireless interface
configuration and control overhead for DAD and
Multicast Listener Discovery (MLD)
should be minimized to support V2I and V2X communications for vehicles
moving fast along roadways.
Let us consider the upload/download time of a ground vehicle when it passes
through the wireless communication coverage of an IP-RSU.
For a given typical setting where 1km is the maximum DSRC communication
range and 100km/h is the speed limit in highway for
ground vehicles, the dwelling time can be calculated to be 72 seconds
by dividing the diameter
of the 2km (i.e., two times of DSRC communication range where an IP-RSU
is located in the center of the circle of wireless communication) by
the speed limit of 100km/h (i.e., about 28m/s). For the 72 seconds, a
vehicle passing through the coverage of an IP-RSU can upload and download
data packets to/from the IP-RSU.
For special cases such as emergency vehicles moving above the speed limit, the dwelling time is relatively shorter than that of other vehicles.
For cases of airborne vehicles, considering a higher flying speed and a
higher altitude, the dwelling time can be much shorter.
This section discusses the internetworking between the moving
networks of two neighboring vehicles via V2V communication.
(*)
(2001:db8:1:1::/64) | |
+------------------------------+ +------------------------------+
| v | | v |
| +-------+ +-------+ | | +-------+ +-------+ |
| | Host1 | |IP-OBU1| | | |IP-OBU2| | Host3 | |
| +-------+ +-------+ | | +-------+ +-------+ |
| ^ ^ | | ^ ^ |
| | | | | | | |
| v v | | v v |
| ---------------------------- | | ---------------------------- |
| 2001:db8:10:1::/64 ^ | | ^ 2001:db8:30:1::/64 |
| | | | | |
| v | | v |
| +-------+ +-------+ | | +-------+ +-------+ |
| | Host2 | |Router1| | | |Router2| | Host4 | |
| +-------+ +-------+ | | +-------+ +-------+ |
| ^ ^ | | ^ ^ |
| | | | | | | |
| v v | | v v |
| ---------------------------- | | ---------------------------- |
| 2001:db8:10:2::/64 | | 2001:db8:30:2::/64 |
+------------------------------+ +------------------------------+
Vehicle1 (Mobile Network1) Vehicle2 (Mobile Network2)
<----> Wired Link <....> Wireless Link (*) Antenna
]]> shows the internetworking
between the mobile networks of two neighboring vehicles. There
exists an internal network (Mobile Network1) inside Vehicle1.
Vehicle1 has two hosts (Host1 and Host2), and two routers
(IP-OBU1 and Router1). There exists another internal network
(Mobile Network2) inside Vehicle2. Vehicle2 has two hosts
(Host3 and Host4), and two routers (IP-OBU2 and Router2).
Vehicle1's IP-OBU1 (as a mobile router) and Vehicle2's IP-OBU2
(as a mobile router) use 2001:db8:1:1::/64 for an external link
(e.g., DSRC) for V2V networking. Thus, a host (Host1) in Vehicle1
can communicate with another host (Host3) in Vehicle2 for a vehicular
service through Vehicle1's mobile network, a wireless link between
IP-OBU1 and IP-OBU2, and Vehicle2's mobile network.
As a V2V use case in ,
shows the
linear network topology of platooning vehicles for V2V communications
where Vehicle3 is the leading vehicle with a driver, and Vehicle2 and
Vehicle1 are the following vehicles without drivers.
From a security point of view, before vehicles can be platooned,
they shall be mutually authenticated to reduce possible security risks.
(*)<..................>(*)
| | |
+-----------+ +-----------+ +-----------+
| | | | | |
| +-------+ | | +-------+ | | +-------+ |
| |IP-OBU1| | | |IP-OBU2| | | |IP-OBU3| |
| +-------+ | | +-------+ | | +-------+ |
| ^ | | ^ | | ^ |
| | |=====> | | |=====> | | |=====>
| v | | v | | v |
| +-------+ | | +-------+ | | +-------+ |
| | Host1 | | | | Host2 | | | | Host3 | |
| +-------+ | | +-------+ | | +-------+ |
| | | | | |
+-----------+ +-----------+ +-----------+
Vehicle1 Vehicle2 Vehicle3
<----> Wired Link <....> Wireless Link ===> Moving Direction
(*) Antenna
]]>
As shown in ,
multihop internetworking is feasible among the mobile networks of
three vehicles in the same VANET. For example, Host1 in Vehicle1 can
communicate with Host3 in Vehicle3 via IP-OBU1 in Vehicle1, IP-OBU2 in
Vehicle2, and IP-OBU3 in Vehicle3 in the VANET, as shown in
the figure.
In this section, the link between two vehicles is assumed to be stable
for single-hop wireless communication regardless of the sight relationship
such as line of sight and non-line of sight, as shown in
.
Even in , the three
vehicles are connected to each other with a linear topology, however,
multihop V2V communication can accommodate any network topology (i.e.,
an arbitrary graph) over VANET routing protocols.
(*)<..................>(*)
| | |
+-----------+ +-----------+ +-----------+
| | | | | |
| +-------+ | | +-------+ | | +-------+ |
| |IP-OBU1| | | |IP-RSU1| | | |IP-OBU3| |
| +-------+ | | +-------+ | | +-------+ |
| ^ | | ^ | | ^ |
| | |=====> | | | | | |=====>
| v | | v | | v |
| +-------+ | | +-------+ | | +-------+ |
| | Host1 | | | | Host2 | | | | Host3 | |
| +-------+ | | +-------+ | | +-------+ |
| | | | | |
+-----------+ +-----------+ +-----------+
Vehicle1 EN1 Vehicle3
<----> Wired Link <....> Wireless Link ===> Moving Direction
(*) Antenna
]]>
As shown in ,
multihop internetworking between two vehicles is feasible via
an infrastructure node (i.e., IP-RSU) with wireless connectivity
among the mobile networks of two vehicles and the fixed network of
an edge network (denoted as EN1) in the same VANET. For example,
Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via
IP-OBU1 in Vehicle1, IP-RSU1 in EN1, and IP-OBU3 in Vehicle3 in
the VANET, as shown in the figure.
For the reliability required in V2V networking, the ND optimization
defined in MANET improves the classical IPv6 ND in terms
of tracking neighbor information with up to two hops and introducing
several extensible Information Bases, which serves the MANET routing
protocols such as the different versions of Optimized Link State
Routing Protocol (OLSR) , Open Shortest Path First (OSPF) derivatives
(e.g., ), and Dynamic Link Exchange Protocol (DLEP)
with its extensions .
In short, the MANET ND mainly deals with
maintaining extended network neighbors to enhance the link reliability.
However, an ND protocol in
vehicular networks shall consider more about the geographical mobility
information of vehicles as an important resource for serving various
purposes to improve the reliability, e.g., vehicle driving safety,
intelligent transportation implementations, and advanced mobility
services. For a more reliable V2V networking, some redundancy
mechanisms should be provided in L3 in cases of the failure of L2.
For different use cases, the optimal solution to improve V2V networking
reliability may vary. For example, a group of vehicles in platooning may
have stabler neighbors than freely moving vehicles, as described in
.
In order to specify protocols using the architecture mentioned in
,
IPv6 core protocols have to be adapted to overcome certain
challenging aspects of vehicular networking. Since the vehicles are
likely to be moving at great speed, protocol exchanges need to be
completed in a relatively short time compared to the lifetime of a
link between a vehicle and an IP-RSU, or between two vehicles.
In these cases, vehicles may not have enough time either to build
link-layer connections with each other and may rely more on
connections with infrastructure.
In other cases, the relative speed between vehicles
may be low when vehicles move toward the same direction or
are platooned.
For those cases, vehicles can have more time to build and maintain
connections with each other.
For safe driving, vehicles need to exchange application messages
every 0.5 second to let drivers
take an action to avoid a dangerous situation (e.g., vehicle collision),
so the IPv6 control plane (e.g., ND procedure and DAD) needs
to support this order of magnitude for application message exchanges.
Also, considering the communication range of DSRC (up to 1km) and
100km/h as the speed limit in highway (some countries can have much
higher speed limit or even no limit, e.g., Germany),
the lifetime of a link between
a vehicle and an IP-RSU is in the order of a minute (e.g., about
72 seconds), and the lifetime of a link
between two vehicles is about a half minute.
Note that if two vehicles are moving in the opposite directions in
a roadway, the relative speed of this case is two times the relative
speed of a vehicle passing through an IP-RSU. This relative speed leads
the half of the link lifetime between the vehicle and the IP-RSU.
In reality, the DSRC communication range is around 500m, so the link
lifetime will be a half of the maximum time.
The time constraint of a wireless link between two nodes (e.g., vehicle
and IP-RSU) needs to be considered because it may affect the lifetime
of a session involving the link.
The lifetime of a session varies depending on the session's type
such as a web surfing, voice call over IP, DNS query, and
context-aware navigation (in ).
Regardless of a session's type, to guide all the IPv6 packets to
their destination host(s), IP mobility should be supported for the
session. In a V2V scenario (e.g., context-aware navigation), the IPv6
packets of a vehicle should be delivered to relevant vehicles efficiently
(e.g., multicasting).
With this observation, IPv6 protocol exchanges need to be done as
short as possible to support the message exchanges of various
applications in vehicular networks.
Therefore, the time constraint of a wireless link has a major impact on
IPv6 Neighbor Discovery (ND). Mobility Management (MM) is also
vulnerable to disconnections that occur before the completion of
identity verification and tunnel management. This is especially
true given the unreliable nature of wireless communication.
Meanwhile, the bandwidth of the wireless link determined by the
lower layers (i.e., link and PHY layers) can affect the transmission
time of control messages of the upper layers (e.g., IPv6) and the
continuity of sessions in the higher layers (e.g., IPv6, TCP, and UDP).
Hence, the bandwidth selection according to Modulation and Coding Scheme
(MCS) also affects the vehicular network connectivity. Note that usually
the higher bandwidth gives the shorter communication range and the
higher packet error rate at the receiving side, which may reduce the
reliability of control message exchanges of the higher layers (e.g.,
IPv6). This section presents key topics such as neighbor discovery and
mobility management for links and sessions in IPv6-based vehicular
networks.
Note that the detailed discussion on the transport-layer session
mobility and usage of available bandwidth to fulfill the use cases
is left as potential future work.
IPv6 ND
is a core part of the IPv6 protocol suite. IPv6 ND is designed
for link types including point-to-point, multicast-capable (e.g.,
Ethernet) and Non-Broadcast Multiple Access (NBMA).
It assumes the efficient and reliable support of multicast and
unicast from the link layer for various network operations
such as MAC Address Resolution (AR), DAD, MLD and Neighbor
Unreachability Detection (NUD).
Vehicles move quickly within the communication coverage of any
particular vehicle or IP-RSU. Before the vehicles can exchange
application messages with each other, they need IPv6 addresses
to run IPv6 ND.
The requirements for IPv6 ND for vehicular networks are efficient
DAD and NUD operations. An efficient DAD is required to reduce
the overhead of DAD packets during a vehicle's travel in a
road network, which can guarantee the uniqueness of a vehicle's
global IPv6 address. An efficient NUD is required to reduce the
overhead of the NUD packets during a vehicle's travel in a road
network, which can guarantee the accurate neighborhood information
of a vehicle in terms of adjacent vehicles and RSUs.
The legacy DAD assumes that a node with an IPv6 address can reach any
other node with the scope of its address at the time it claims its address,
and can hear any future claim for that address by another party within
the scope of its address for the duration of the address ownership.
However, the partitioning and merging of VANETs makes this assumption
be not valid frequently in vehicular networks.
The merging and partitioning of VANETs frequently occurs in vehicular
networks.
This merging and partitioning should be considered for the
IPv6 ND such as IPv6 Stateless Address Autoconfiguration (SLAAC)
.
SLAAC is not compatible with merging and partitioning, and additional
work is needed for ND to operate properly under those circumstances.
Due to the merging of VANETs, two IPv6 addresses may conflict with
each other though they were unique before the merging. An address
lookup operation may be conducted by an MA or IP-RSU (as Registrar in
RPL) to check the uniqueness of an IPv6 address that will be
configured by a vehicle as DAD.
Also, the partitioning of a VANET may make vehicles with the same
prefix be physically unreachable. An address lookup operation may be
conducted by an MA or IP-RSU (as Registrar in RPL) to check the
existence of a vehicle under the network coverage of the MA or IP-RSU
as NUD.
Thus, SLAAC needs to prevent IPv6 address duplication due to the
merging of VANETs, and IPv6 ND needs to detect unreachable neighboring
vehicles due to the partitioning of a VANET. According to the merging
and partitioning, a destination vehicle (as an IPv6 host) needs to be
distinguished as either an on-link host or a not-onlink host even
though the source vehicle can use the same prefix as the destination
vehicle .
To efficiently prevent IPv6 address duplication due to the VANET
partitioning and merging from happening in vehicular networks, the
vehicular networks need to support a vehicular-network-wide DAD by
defining a scope that is compatible with the legacy DAD. In this case,
two vehicles can communicate with each other when there exists a
communication path over VANET or a combination of VANETs and IP-RSUs,
as shown in .
By using the vehicular-network-wide DAD, vehicles can assure that
their IPv6 addresses are unique in the vehicular network whenever
they are connected to the vehicular infrastructure or become
disconnected from it in the form of VANET.
For vehicular networks with high mobility and density, DAD
needs to be performed efficiently with minimum overhead so that
the vehicles can exchange driving safety messages (e.g.,
collision avoidance and accident notification) with each other
with a short interval suggested by
NHTSA (National Highway Traffic Safety Administration)
.
Since the partitioning and merging of vehicular networks may
require re-perform DAD process repeatedly, the link scope
of vehicles may be limited to a small area, which may delay
the exchange of driving safety messages. Driving safety
messages can include a vehicle's mobility information (i.e.,
position, speed, direction, and acceleration/deceleration)
that is critical to other vehicles. The exchange interval of
this message is recommended to be less than 0.5 second, which is required
for a driver to avoid an emergency situation, such as a rear-end crash.
ND time-related parameters such as router lifetime and Neighbor
Advertisement (NA) interval need to be adjusted for vehicle speed
and vehicle density. For example, the NA interval needs to be
dynamically adjusted according to a vehicle's speed so that
the vehicle can maintain its neighboring vehicles in a stable way,
considering the collision probability with the NA messages sent
by other vehicles. The ND time-related parameters can be an operational
setting or an optimization point particularly for vehicular networks.
Note that the link-scope multicast messages in ND protocol may cause
the performance issue in vehicular networks.
suggests several optimization approaches for the issue.
For IPv6-based safety applications (e.g., context-aware navigation,
adaptive cruise control, and platooning) in vehicular networks,
the delay-bounded data delivery is critical. IPv6 ND needs to
work to support those IPv6-based safety applications efficiently.
introduces
a Vehicular Neighbor Discovery (VND) process as an extension of IPv6 ND
for IP-based vehicular networks.
From the interoperability point of view, in IPv6-based vehicular
networking, IPv6 ND should have minimum changes with the legacy
IPv6 ND used in the Internet, including DAD and NUD operations,
so that IPv6-based vehicular networks can be seamlessly connected
to other intelligent transportation elements (e.g., traffic signals,
pedestrian wearable devices, electric scooters, and bus stops) that
use the standard IPv6 network settings.
A subnet model for a vehicular network needs to facilitate the
communication between two vehicles with the same prefix regardless
of the vehicular network topology as long as there exist
bidirectional E2E paths between them in the vehicular
network including VANETs and IP-RSUs.
This subnet model allows vehicles with the same prefix to
communicate with each other via a combination of multihop V2V and
multihop V2I with VANETs and IP-RSUs.
introduces other issues in an IPv6
subnet model.
IPv6 protocols work under certain assumptions that do not necessarily
hold for vehicular wireless access link types
.
For instance, some IPv6 protocols such as NUD and MIPv6
assume symmetry in the connectivity among neighboring interfaces.
However, radio interference and different levels of transmission power
may cause asymmetric links to appear in vehicular wireless links
.
As a result, a new vehicular link model needs to consider the asymmetry
of dynamically changing vehicular wireless links.
There is a relationship between a link and a prefix, besides the
different scopes that are expected from the link-local, unique-local,
and global types
of IPv6 addresses. In an IPv6 link, it is defined that all interfaces
which are configured with the same subnet prefix and with on-link bit
set can communicate with each other on an IPv6 link. However, the
vehicular link model needs to define the relationship between a link
and a prefix, considering the dynamics of wireless links and the
characteristics of VANET.
A VANET can have a single link between each vehicle pair within
wireless communication range, as shown in
. When two vehicles
belong to the same VANET, but they are out of wireless communication
range, they cannot communicate directly with each other. Suppose that
a global-scope IPv6 prefix (or an IPv6 ULA prefix) is assigned to
VANETs in vehicular networks.
Considering that two vehicles in the same VANET configure their IPv6
addresses with the same IPv6 prefix, if they are not in one hop (that is, they have the
multihop network connectivity between them), then they may
not be able to communicate with each other.
Thus, in this case, the concept of
an on-link IPv6 prefix does not hold because two vehicles with the
same on-link IPv6 prefix cannot communicate directly with each other.
Also, when two vehicles are located in two different VANETs with the
same IPv6 prefix, they cannot communicate with each other. When these
two VANETs converge to one VANET, the two vehicles can communicate with
each other in a multihop fashion, for example, when they are Vehicle1
and Vehicle3, as shown in .
From the previous observation, a vehicular link model should consider
the frequent partitioning and merging of VANETs due to vehicle mobility.
Therefore, the vehicular link model needs to use an on-link prefix and
not-onlink prefix according to the network topology of vehicles such as
a one-hop reachable network and a multihop reachable network (or
partitioned networks). If the vehicles with the same prefix are
reachable from each other in one hop, the prefix should be on-link.
On the other hand, if some of the vehicles with the same prefix are not
reachable from each other in one hop due to either the multihop
topology in the VANET or multiple partitions, the prefix should be
not-onlink. In most cases in vehicular networks, due to the partitioning
and merging of VANETs, and the multihop network topology of VANETS,
not-onlink prefixes will be used for vehicles as default.
The vehicular link model needs to support multihop routing in a
connected VANET where the vehicles with the same global-scope IPv6
prefix (or the same IPv6 ULA prefix) are connected in one hop or
multiple hops. It also needs to support the multihop routing in
multiple connected VANETs through infrastructure nodes (e.g., IP-RSU)
where they are connected to the infrastructure. For example, in
, suppose that
Vehicle1, Vehicle2, and Vehicle3 are configured with their IPv6
addresses based on the same global-scope IPv6 prefix. Vehicle1 and
Vehicle3 can also communicate with each other via either multihop
V2V or multihop V2I2V. When Vehicle1 and Vehicle3 are connected in
a VANET, it will be more efficient for them to communicate with each
other directly via VANET rather than indirectly via IP-RSUs. On the
other hand, when Vehicle1 and Vehicle3 are far away from direct
communication range in separate VANETs and under two different
IP-RSUs, they can communicate with each other through the relay of
IP-RSUs via V2I2V.
Thus, two separate VANETs can merge into one network via IP-RSU(s).
Also, newly arriving vehicles can merge two separate VANETs into
one VANET if they can play the role of a relay node for those VANETs.
Thus, in IPv6-based vehicular networking, the vehicular link model
should have minimum changes for interoperability with standard IPv6
links efficiently to support IPv6 DAD, MLD and NUD
operations.
For the protection of drivers' privacy, a pseudonym of a MAC
address of a vehicle's network interface should be used, so that
the MAC address can be changed periodically. However, although
such a pseudonym of a MAC address can protect to some extent the
privacy of a vehicle, it may not be able to resist attacks on
vehicle identification by other fingerprint information, for example,
the scrambler seed embedded in IEEE 802.11-OCB frames
.
Note that
discusses more about MAC address randomization, and
describes several use cases
for MAC address randomization.
In the ETSI standards, for the sake of security and privacy, an
ITS station (e.g., vehicle) can use pseudonyms for its network
interface identities (e.g., MAC address) and the corresponding
IPv6 addresses . Whenever
the network interface identifier changes, the IPv6 address based
on the network interface identifier needs to be updated, and the
uniqueness of the address needs to be checked through DAD
procedure.
For multihop V2V communications in either a VANET or VANETs via
IP-RSUs, a vehicular Mobile Ad Hoc Networks (MANET)
routing protocol may be required to support both unicast and
multicast in the links of the subnet with the same IPv6
prefix. However, it will be costly to run both vehicular ND
and a vehicular ad hoc routing protocol in terms of control
traffic overhead .
A routing protocol for a VANET may cause redundant wireless
frames in the air to check the neighborhood of each vehicle
and compute the routing information in a VANET with a dynamic
network topology because the IPv6 ND is used to check the
neighborhood of each vehicle. Thus, the vehicular routing
needs to take advantage of the IPv6 ND to minimize its control
overhead.
RPL defines a routing protocol for low-power
and lossy networks, which constructs and maintains Destination-Oriented
Directed Acyclic Graphs (DODAGs) optimized by an Objective Function (OF).
A defined OF provides route selection and optimization within an RPL
topology.
The RPL nodes use an anisotropic Distance Vector (DV) approach to
form a DODAG by discovering and aggressively maintaining the upward
default route toward the root of the DODAG. Downward routes follow
the same DODAG, with lazy maintenance and stretched Peer-to-Peer
(P2P) routing in the so-called storing mode.
It is well-designed to reduce the topological knowledge and routing
state that needs to be exchanged.
As a result, the routing protocol overhead is minimized, which allows
either highly constrained stable networks or less constrained, highly
dynamic networks. Refer to
for the detailed description of RPL for multihop V2X networking.
An address registration extension for 6LoWPAN (IPv6 over Low-Power
Wireless Personal Area Network) in can
support light-weight mobility for nodes moving through different parents.
, as opposed to , is
stateful and proactively installs the ND cache entries, which saves
broadcasts and provides deterministic presence information for IPv6
addresses.
Mainly it updates the Address Registration Option (ARO) of ND defined in
to include a status field that can indicate the
movement of a node and optionally a Transaction ID (TID) field, i.e., a
sequence number that can be used to determine the most recent location of
a node.
Thus, RPL can use the information provided by the Extended ARO (EARO) defined in
to deal with a certain level of node mobility.
When a leaf node moves to the coverage of another parent node, it should
de-register its addresses to the previous parent node and register itself
with a new parent node along with an incremented TID.
RPL can be used in IPv6-based vehicular networks, but it is primarily
designed for low-power networks, which puts energy efficiency first.
For using it in IPv6-based vehicular networks, there have not been
actual experiences and practical implementations, though it was tested in
IoT low-power and lossy networks (LLN) scenarios.
Another concern is that RPL may generate excessive topology discovery
messages in a highly moving environment such as vehicular networks.
This issue can be an operational or optimization point for a practitioner.
Moreover, due to bandwidth and energy constraints, RPL does not suggest
using a proactive mechanism (e.g., keepalive) to maintain accurate routing
adjacencies such as Bidirectional Forwarding Detection
and MANET Neighborhood Discovery Protocol .
As a result, due to the mobility of vehicles, network fragmentation may
not be detected quickly and the routing of packets between vehicles
or between a vehicle and an infrastructure node may fail.
The seamless connectivity and timely data exchange between
two end points requires efficient mobility management
including location management and handover.
Most vehicles are equipped with a GNSS receiver as part of
a dedicated navigation system or a corresponding smartphone
App. Note that the GNSS receiver may not provide vehicles with
accurate location information in adverse environments such as
a building area or a tunnel. The location precision can be
improved with assistance of the IP-RSUs or a cellular system
with a GNSS receiver for location information.
With a GNSS navigator, efficient mobility management can
be performed with the help of vehicles periodically reporting
their current position and trajectory (i.e., navigation path) to
the vehicular infrastructure (having IP-RSUs and an MA in TCC).
This vehicular infrastructure can predict the future positions
of the vehicles from their mobility information (i.e., the current
position, speed, direction, and trajectory) for efficient mobility
management (e.g., proactive handover). For a better proactive
handover, link-layer parameters, such as the signal strength of a
link-layer frame (e.g., Received Channel Power Indicator (RCPI)
), can be used to determine the
moment of a handover between IP-RSUs along with mobility
information.
By predicting a vehicle's mobility, the vehicular infrastructure
needs to better support IP-RSUs to perform efficient SLAAC, data
forwarding, horizontal handover (i.e., handover in wireless links
using a homogeneous radio technology), and vertical handover
(i.e., handover in wireless links using heterogeneous radio
technologies) in advance along with the movement of the vehicle.
For example, as shown in ,
when a vehicle (e.g., Vehicle2) is moving from the coverage of an
IP-RSU (e.g., IP-RSU1) into the coverage of another IP-RSU (e.g.,
IP-RSU2) belonging to a different subnet, the IP-RSUs can
proactively support the IPv6 mobility of the vehicle, while
performing the SLAAC, data forwarding, and handover for the sake
of the vehicle.
For a mobility management scheme in a domain, where the
wireless subnets of multiple IP-RSUs share the same prefix,
an efficient vehicular-network-wide DAD is required.
On the other hand, for a mobility
management scheme with a unique prefix per mobile node (e.g., PMIPv6
),
DAD is not required because the IPv6 address of a vehicle's external
wireless interface is guaranteed to be unique. There is a trade-off
between the prefix usage efficiency and DAD overhead. Thus, the IPv6
address autoconfiguration for vehicular networks needs to consider
this trade-off to support efficient mobility management.
Even though the SLAAC with classic ND costs a DAD during mobility
management, the SLAAC with and/or AERO/OMNI
do not cost a DAD. SLAAC for vehicular networks needs to consider the
minimization of the cost of DAD with the help of an infrastructure
node (e.g., IP-RSU and MA). Using an infrastructure prefix over VANET
allows direct routability to the Internet through the multihop V2I toward
an IP-RSU. On the other hand, a BYOA does not allow such direct
routability to the Internet since the BYOA is not topologically
correct, that is, not routable in the Internet. In addition, a
vehicle configured with a BYOA needs a tunnel home (e.g., IP-RSU)
connected to the Internet, and the vehicle needs to know which
neighboring vehicle is reachable inside the VANET toward the tunnel
home. There is non-negligible control overhead to set up and
maintain routes to such a tunnel home over the VANET.
For the case of a multihomed network, a vehicle can follow the
first-hop router selection rule described in .
For example, an IP-OBU inside a vehicle may connect to an IP-RSU that
has multiple routers behind. In this scenario, because the IP-OBU
can have multiple prefixes from those routers, the default router
selection, source address selection, and packet redirect process
should follow the guidelines in .
That is, the vehicle should select its default router for each prefix
by preferring the router that advertised the prefix.
Vehicles can use the TCC as their Home Network having a home agent
for mobility management as in MIPv6 ,
PMIPv6 , and NEMO , so the TCC (or an MA inside the
TCC) maintains the mobility information of vehicles for location
management. Also, in vehicular networks,
asymmetric links sometimes exist and must be considered for
wireless communications such as V2V and V2I.
discusses
a Vehicular Mobility Management (VMM) scheme to proactively do handover
for vehicles.
Therefore, for the proactive and seamless IPv6 mobility of vehicles,
the vehicular infrastructure (including IP-RSUs and MA) needs to
efficiently perform the mobility management of the vehicles with
their mobility information and link-layer information.
Also, in IPv6-based vehicular networking, IPv6 mobility management
should have minimum changes for the interoperability with the
legacy IPv6 mobility management schemes such as PMIPv6, DMM, LISP,
and AERO.
This section discusses security and privacy for IPv6-based vehicular
networking. Security and privacy are paramount in V2I, V2V, and V2X
networking along with neighbor discovery and mobility
management.
Vehicles and infrastructure must be authenticated to each other by
a password, a key, and/or a fingerprint
in order to participate in vehicular networking.
For the authentication in vehicular networks, vehicular cloud
needs to support a Public Key Infrastructure (PKI) efficiently, as either
a dedicated or a co-located component inside a TCC.
To provide safe interaction between vehicles
or between a vehicle and infrastructure, only authenticated
nodes (i.e., vehicle and infrastructure node) can participate
in vehicular networks.
Also, in-vehicle devices (e.g., ECU) and a driver/passenger's mobile
devices (e.g., smartphone and tablet PC) in a vehicle need to
communicate with other in-vehicle devices and another
driver/passenger's mobile devices in another vehicle, or other
servers behind an IP-RSU securely.
Even though a vehicle is perfectly authenticated by another entity
and legitimate to use the data generated by another vehicle,
it may be hacked for running malicious applications to track and
collect its and other vehicles' information. In this case, an
attack mitigation process may be required to reduce the aftermath of
malicious behaviors.
Note that when driver/passenger's mobile devices are connected to a
vehicle's internal network, the vehicle may be more vulnerable to possible
attacks from external networks due to the exposure of its
in-flight traffic packets.
discusses several types of threats for Vehicular Security and Privacy (VSP).
For secure V2I communication, a secure channel (e.g., IPsec) between
a mobile router (i.e., IP-OBU) in a vehicle and a fixed router
(i.e., IP-RSU) in an EN needs to be established, as shown in
.
Also, for secure V2V communication, a secure channel (e.g., IPsec)
between a mobile router (i.e., IP-OBU) in a vehicle and a mobile
router (i.e., IP-OBU) in another vehicle needs to be established, as
shown in .
For secure V2I/V2V communication, an element in a vehicle (e.g., an
in-vehicle device and a driver/passenger's mobile device) needs to
establish a secure connection (e.g., TLS) with another element in
another vehicle or another element in a vehicular cloud (e.g., a
server).
Note that any key management approach can be used for the secure
communication, and particularly for IPv6-based vehicular networks,
a new or enhanced key management approach resilient to wireless
networks is required.
IEEE 1609.2 specifies
security services for applications and management messages, but this
WAVE specification is optional.
Thus, if the link layer does not support the security of a WAVE frame,
either the network layer or the
transport layer needs to support security services for the WAVE
frames.
For the classical IPv6 ND (i.e., the legacy ND), DAD is required
to ensure the uniqueness of the
IPv6 address of a vehicle's wireless interface. This DAD can be
used as a flooding attack that uses the DAD-related ND packets
disseminated over the VANET or vehicular networks.
introduces threats enabled by IP source address spoofing.
This possibility indicates that vehicles and IP-RSUs need to filter
out suspicious ND traffic in advance.
introduces a mechanism that protects
the ownership of an address for 6loWPAN ND from address theft
and impersonation attacks.
Based on the SEND mechanism, the
authentication for routers (i.e., IP-RSUs) can be conducted
by only selecting an IP-RSU that has a certification path toward
trusted parties. For authenticating other vehicles,
cryptographically generated addresses (CGA) can be used to
verify the true owner of a received ND message, which requires
using the CGA ND option in the ND protocol.
This CGA can protect vehicles against DAD flooding
by DAD filtering based on the verification for the true owner
of the received DAD message.
For a general protection of the ND mechanism, the RSA Signature
ND option can also be used to protect the integrity of the
messages by public key signatures. For a more advanced
authentication mechanism, a distributed blockchain-based
approach can be used.
However, for a scenario where a trustable router or an
authentication path cannot be obtained, it is desirable to find
a solution in which vehicles and infrastructures can
authenticate each other without any support from a third party.
When applying the classical IPv6 ND process to VANET, one of
the security issues is that an IP-RSU (or an IP-OBU) as
a router may receive deliberate or accidental DoS attacks from network
scans that probe devices on a VANET. In this scenario, the IP-RSU can be
overwhelmed for processing the network scan requests so that
the capacity
and resources of IP-RSU are exhausted, causing the failure of receiving
normal ND messages from other hosts for network address resolution.
describes more about the operational problems
in the classical IPv6 ND mechanism that can be vulnerable to deliberate
or accidental DoS attacks and suggests several implementation guidelines
and operational mitigation techniques for those problems.
Nevertheless, for running IPv6 ND in VANET, those issues can be
more acute
since the movements of vehicles can be so diverse that it leaves a large
room for rogue behaviors, and the failure of networking among vehicles
may cause grave consequences.
Strong security measures shall protect vehicles roaming in road
networks from the attacks of malicious nodes, which are controlled
by hackers. For safe driving applications (e.g., context-aware
navigation, cooperative adaptive cruise control, and platooning),
as explained in , the
cooperative action among vehicles is assumed. Malicious nodes may
disseminate wrong driving information (e.g., location, speed, and
direction) for disturbing safe driving. For example, a Sybil attack,
which tries to confuse a vehicle with multiple false identities,
may disturb a vehicle from taking a safe maneuver.
Since cybersecurity issues in vehicular networks may cause physical
vehicle safety issues, it may be necessary to consider those physical
security concerns when designing protocols in IPWAVE.
To identify malicious vehicles among vehicles, an authentication
method may be required.
A Vehicle Identification Number (VIN) (or a vehicle manufacturer
certificate) and a user certificate (e.g.,
X.509 certificate ) along with an in-vehicle
device's identifier generation can be used to efficiently
authenticate a vehicle or its driver (having a user certificate)
through a road infrastructure node (e.g., IP-RSU) connected to an
authentication server in the vehicular cloud.
This authentication can be used to identify the vehicle that will
communicate with an infrastructure node or another vehicle.
In the case where a vehicle has an internal network (called Moving
Network) and elements in the network (e.g., in-vehicle devices and
a user's mobile devices), as shown in
, the elements in the
network need to be authenticated individually for safe
authentication.
Also, Transport Layer Security (TLS) certificates
can be used for
an element's authentication to allow secure E2E vehicular communications
between an element in a vehicle and another element in a server in a
vehicular cloud, or between an element in a vehicle and another
element in another vehicle.
For mobility management, a malicious vehicle can construct
multiple virtual bogus vehicles, and register them with IP-RSUs
and MA. This registration makes the IP-RSUs and MA waste their
resources. The IP-RSUs and MA need to determine whether
a vehicle is genuine or bogus in mobility management.
Also, the confidentiality of control packets and data packets
among IP-RSUs and MA, the E2E paths (e.g., tunnels) need to be
protected by secure communication channels.
In addition, to prevent bogus IP-RSUs and MA from interfering with
the IPv6 mobility of vehicles, mutual authentication among them
needs to be performed by certificates (e.g., TLS certificate).
For the setup of a secure channel over IPsec or TLS, the multihop V2I
communications over DSRC or 5G V2X (or LTE V2X) is required in
a highway. In this case, multiple intermediate vehicles as relay
nodes can help to forward association and authentication messages
toward an IP-RSU (gNodeB or eNodeB) connected to an authentication
server in the vehicular cloud. In this kind of process, the
authentication messages forwarded by each vehicle can be delayed or
lost, which may increase the construction time of a connection or some
vehicles may not be able to be authenticated.
Even though vehicles can be authenticated with valid certificates by
an authentication server in the vehicular cloud, the authenticated
vehicles may harm other vehicles. To deal with this kind of security
issue, for monitoring suspicious behaviors, vehicles' communication
activities can be recorded in either a centralized approach through a
logging server (e.g., TCC) in the vehicular cloud or a decentralized
approach (e.g., an edge computing device and blockchain
) by the help of other vehicles and
infrastructure.
There are trade-offs between centralized and decentralized approaches
in logging for vehicles' behaviors (e.g., location, speed, direction,
acceleration, deceleration, and lane change) and communication
activities (e.g., transmission time, reception time, and packet types
such as TCP, UDP, SCTP, QUIC, HTTP, and HTTPS).
A centralized approach is more efficient than a decentralized
approach in terms of logging data collection and processing in a
central server in the vehicular cloud.
However, the centralized approach may cause a higher delay than a
decentralized approach in terms of the analysis of the logging data
and counteraction in a local edge computing device or a distributed
database like a blockchain.
The centralized approach stores logging data collected from VANET into
a remote logging server in a vehicular cloud as a central cloud, so it
takes time to deliver the logging data to a remote logging server.
On the other hand, the decentralized approach stores the logging data
into a nearby edge computing device as a local logging server or a
nearby blockchain node, which participates in a blockchain network.
On the stored logging data, an analyzer needs to perform a machine
learning technique (e.g., Deep Learning) and seek suspicious behaviors
of the vehicles. If such an analyzer is located either within or near
the edge computing device, it can access the logging data with a short
delay, analyze it quickly, and generate feedback to allow for a quick
counteraction against such malicious behaviors. On the other hand,
if the vehicular cloud with the logging data is far away from a
problematic VANET with malicious behaviors, the centralized approach
takes a long time with the analysis with the logging data and the
decision-making on malicious behaviors than the decentralized approach.
If the logging data is encrypted by a secret key, it can be protected
from the observation of a hacker. The secret key sharing among legal
vehicles, edge computing devices, and vehicular clouds should be
supported efficiently.
Logging information can release privacy breakage of a vehicle.
The logging information can contain the MAC address and IPv6
address for a vehicle's wireless network interface. If the unique
MAC address of the wireless network interface is used, a hacker
can track the vehicle with that MAC address, so can track the
privacy information of the vehicle's driver (e.g., location
information). To prevent this privacy breakage, a MAC address
pseudonym can be used for the MAC address of the wireless network
interface, and the corresponding IPv6 address should be based on
such a MAC address pseudonym.
By solving a privacy issue of a vehicle's identity in logging,
vehicles may observe activities of each other to identify any
misbehavior without privacy breakage. Once identifying a
misbehavior, a vehicle shall have a way to either isolate itself
from others or isolate a suspicious vehicle by informing
other vehicles.
For completely secure vehicular networks, we shall embrace the concept
of "zero-trust" for vehicles in which no vehicle is trustable and
verifying every message (such as IPv6 control messages including ND,
DAD, NUD, and application layer messages) is necessary. In this way,
vehicular networks can defense many possible cyberattacks. Thus, we
need to have an efficient zero-trust framework or mechanism for
the vehicular networks.
For the non-repudiation of the harmful activities from malicious
vehicles, which it is difficult for other normal vehicles to identify them,
an additional and advanced approach is needed. One possible
approach is to use a blockchain-based approach
as an IPv6 security checking framework.
Each IPv6 packet from a vehicle can be treated as a transaction and the
neighboring vehicles can play the role of peers in a consensus
method of a blockchain . For a blockchain's efficient
consensus in vehicular networks having fast moving vehicles,
a new consensus algorithm needs to be developed, or an existing
consensus algorithm needs to be enhanced.
In addition, a consensus-based mechanism for the security of
vehicular networks in the IPv6 layer can also be considered.
A group of servers as blockchain infrastructure can be part of
the security checking process in the IP layer.
To prevent an adversary from tracking a vehicle with its MAC
address or IPv6 address, especially for a long-living transport-layer
session (e.g., voice call over IP and video streaming service),
a MAC address pseudonym needs to be provided to each vehicle;
that is, each vehicle periodically updates its MAC address and
its IPv6 address needs to be updated accordingly by the MAC
address change .
Such an update of the MAC and IPv6 addresses should not
interrupt the E2E communications between two vehicles (or
between a vehicle and an IP-RSU) for a long-living transport-layer
session. However, if this pseudonym is performed without strong
E2E confidentiality (using either IPsec or TLS), there will be no
privacy benefit from changing MAC and IPv6 addresses, because an
adversary can observe the change of the MAC and IPv6 addresses and
track the vehicle with those addresses. Thus, the MAC address
pseudonym and the IPv6 address update should be performed with strong
E2E confidentiality.
The privacy exposure to the TCC and via V2I is mostly about the
location information of vehicles, and may also include other
in-vehicle activities such as transactions of credit cards.
The assumed, trusted actors are the owner of a vehicle, an
authorized vehicle service provider (e.g., navigation service provider),
and an authorized vehicle manufacturer for providing
after-sales services.
In addition, privacy concerns for excessively collecting
vehicle activities from
roadway operators such as public transportation administrators and
private contractors may also pose threats on violating privacy rights
of vehicles. It might be interesting to find a solution from a
technology point of view along with public policy development for the
issue.
The "multicasting" of the location information of a VRU's smartphone
means IPv6 multicasting. There is a possible security attack related
to this multicasting. Attackers can use "fake identifiers" as source
IPv6 addresses of their devices to generate IPv6 packets and multicast
them to nearby vehicles in order to make a confusion that those
vehicles are surrounded by other vehicles or pedestrians. As a result,
navigation services (e.g., Google Maps and Waze )
can be confused with fake road traffic by those vehicles or smartphones
with "fake identifiers" .
This attack with "fake identifiers" should be detected and handled by
vehicular networks. To cope with this attack, both legal vehicles and
legal VRUs' smartphones can be registered with a traffic control center
(called TCC) and their locations can be tracked by the TCC. With this
tracking, the TCC can tell the road traffic conditions caused by those
vehicles and smartphones. In addition, to prevent hackers from
tracking the locations of those vehicles and smartphones, either a MAC
address pseudonym or
secure IPv6 address generation
can be used to protect the privacy of those vehicles and smartphones.
This document does not require any IANA actions.
Standard Specification for Telecommunications and Information Exchange Between Roadside and Vehicle Systems - 5 GHz Band Dedicated Short Range Communications (DSRC) Medium Access Control (MAC) and Physical Layer (PHY) Specifications
ASTM International
Commission Decision of 5 August 2008 on the Harmonised Use of Radio Spectrum in the 5875 - 5905 MHz Frequency Band for Safety-related Applications of Intelligent Transport Systems (ITS)
European Union
Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications - Amendment 6: Wireless Access in Vehicular EnvironmentsPart 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) SpecificationsIEEE Guide for Wireless Access in Vehicular Environments (WAVE) - ArchitectureIEEE Standard for Wireless Access in Vehicular Environments - Security Services for Applications and Management MessagesIEEE Standard for Wireless Access in Vehicular Environments (WAVE) - Networking ServicesIEEE Standard for Wireless Access in Vehicular Environments (WAVE) - Multi-Channel OperationIntelligent Transport Systems - Communications Access for Land Mobiles (CALM) - IPv6 NetworkingIntelligent Transport Systems - Communications Access for Land Mobiles (CALM) - IPv6 Networking -
Amendment 1Architecture Enhancements for V2X Services
3GPP
Study on Enhancement of 3GPP Support for 5G V2X Services
3GPP
Architecture Enhancements for 5G System (5GS) to Support
Vehicle-to-Everything (V2X) Services
3GPP
VIP-WAVE: On the Feasibility of IP Communications in 802.11p Vehicular NetworksCross-layer Identities Management in ITS StationsSAINT: Self-Adaptive Interactive Navigation Tool for Cloud-Based Vehicular Traffic OptimizationSAINT+: Self-Adaptive Interactive Navigation Tool+ for Emergency Service Delivery OptimizationSANA: Safety-Aware Navigation Application for Pedestrian Protection in Vehicular NetworksCASD: A Framework of Context-Awareness Safety Driving in Vehicular NetworksCooperative Adaptive Cruise ControlAutomated Truck PlatooningFirst Responder Network Authority (FirstNet)Public Safety Communications Europe (PSCE)FY 2017: ANNUAL REPORT TO CONGRESS, Advancing Public Safety
Broadband Communications
First Responder Network Authority
SignalGuru: Leveraging Mobile Phones for Collaborative
Traffic Signal Schedule AdvisoryFuel-Efficient En Route Formation of Truck PlatoonsMillimeter-Wave Vehicular Communication to Support Massive Automotive SensingFinal Report of Automotive Collision Avoidance Systems (ACAS) Program
National Highway Traffic Safety Administration (NHTSA)
CBDN: Cloud-Based Drone Navigation for Efficient Battery Charging
in Drone NetworksLow Human-Effort, Device-Free Localization with
Fine-Grained Subcarrier InformationDFC: Device-free human counting through WiFi
fine-grained subcarrier informationChallenges in a Future IP/Ethernet-based In-Car Network for Real-Time ApplicationsThe Scrambler Attack: A Robust Physical Layer Attack on Location Privacy in Vehicular NetworksBitcoin: A Peer-to-Peer Electronic Cash SystemBlockChain: A Distributed Solution to Automotive Security and PrivacyUse of the 5.850-5.925 GHz Band, First Report and Order,
Further Notice of Proposed Rulemaking, and Order of Proposed
Modification, FCC 19-138
Federal Communications Commission
German man fools Google Maps' traffic algorithmGoogle MapsGoogle Maps
Vehicular networks may consist of multiple radio technologies such as
DSRC and 5G V2X. Although a Layer-2 solution can provide support for
multihop communications in vehicular networks, the scalability issue
related to multihop forwarding still remains when vehicles need to
disseminate or forward packets toward multihop-away destinations. In
addition, the IPv6-based approach for V2V as a network layer protocol can
accommodate multiple radio technologies as MAC protocols, such as DSRC and
5G V2X. Therefore, the existing IPv6 protocol can be augmented through the
addition of a virtual interface (e.g., OMNI
and DLEP ) and/or
protocol changes in order to support both wireless single-hop/multihop V2V
communications and multiple radio technologies in vehicular networks.
In such a way, vehicles can communicate with each other by V2V
communications to share either an emergency situation or road hazard
information in a highway having multiple kinds of radio technologies.
The multihop V2X networking can be supported by
RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks)
and Overlay Multilink Network
Interface (OMNI) with
AERO .
RPL defines an IPv6 routing protocol for low-power and lossy
networks (LLN), mostly designed for home automation routing,
building automation routing, industrial routing, and urban
LLN routing. It uses a Destination-Oriented Directed Acyclic
Graph (DODAG) to construct routing paths for hosts
(e.g., IoT devices) in a network. The DODAG uses an objective
function (OF) for route selection and optimization within the
network. A user can use different routing metrics to define an OF
for a specific scenario. RPL supports multipoint-to-point,
point-to-multipoint, and point-to-point traffic, and the major
traffic flow is the multipoint-to-point traffic. For example, in
a highway scenario, a vehicle may not access an IP-RSU directly
because of the distance of the DSRC coverage (up to 1 km). In
this case, the RPL can be extended to support a multihop V2I
since a vehicle can take advantage of other vehicles as relay
nodes to reach the IP-RSU. Also, RPL can be extended to support both
multihop V2V and V2X in the similar way.
RPL is primarily designed to minimize the control plane activity,
which is the relative amount of routing protocol exchanges versus data
traffic; this approach is beneficial for situations where the power
and bandwidth are scarce (e.g., an IoT LLN where RPL is typically
used today), but also in situations of high relative mobility between
the nodes in the network (also known as swarming, e.g., within a variable set of
vehicles with a similar global motion, or a variable set of drones flying
toward the same direction).
To reduce the routing exchanges, RPL leverages a Distance Vector (DV)
approach, which does not need a global knowledge of the topology,
and only optimizes the routes to and from the root, allowing
Peer-to-Peer (P2P) paths to be stretched. Although RPL installs its
routes proactively, it only maintains them lazily, that is, in
reaction to actual traffic, or as a slow background activity.
Additionally, RPL leverages the concept of an objective function
(called OF), which allows adapting the activity of the routing
protocol to use cases, e.g., type, speed, and quality of the
radios. RPL does not need converge, and provides connectivity to
most nodes most of the time. The default route toward the root is
maintained aggressively and may change while a packet progresses
without causing loops, so the packet will still reach the root.
There are two modes for routing in RPL such as non-storing mode
and storing mode. In non-storing mode, a node inside the
mesh/swarm that changes its point(s) of attachment to the graph
informs the root with a single unicast packet flowing along the
default route, and the connectivity is restored immediately; this
mode is preferable for use cases where Internet connectivity is
dominant. On the other hand, in storing mode, the routing stretch
is reduced, for a better P2P connectivity, while the Internet
connectivity is restored more slowly, during the time for the DV
operation to operate hop-by-hop. While an RPL topology can
quickly scale up and down and fits the needs of mobility of
vehicles, the total performance of the system will also depend on
how quickly a node can form an address, join the mesh (including
Authentication, Authorization, and Accounting (AAA)), and manage
its global mobility to become reachable from another node outside
the mesh.
OMNI defines a protocol for the transmission of IPv6 packets over
Overlay Multilink Network Interfaces that are virtual interfaces
governing multiple physical network interfaces.
OMNI supports multihop V2V communication between vehicles
in multiple forwarding hops via intermediate vehicles with OMNI links.
It also supports multihop V2I communication between a vehicle and an
infrastructure access point by multihop V2V communication.
The OMNI interface supports an NBMA link model where multihop V2V and
V2I communications use each mobile node's ULAs without need for any DAD
or MLD Messaging.
In OMNI protocol, an OMNI virtual interface can have a ULA
indeed, but wireless physical interfaces
associated with the OMNI virtual interface are using any prefix.
The ULA supports both V2V and V2I multihop forwarding within the
vehicular network (e.g., via a VANET routing protocol) while each
vehicle can communicate with Internet correspondents using global
IPv6 addresses via OMNI interface encapsulation over the wireless
interface.
For the control traffic overhead for running both vehicular ND and a VANET
routing protocol, the AERO/OMNI approach may avoid this issue by using
MANET routing protocols only (i.e., no multicast of IPv6 ND messaging) in
the wireless underlay network while applying efficient unicast IPv6 ND
messaging in the OMNI overlay on an as-needed basis for router discovery
and NUD. This greatly reduces the overhead for VANET-wide multicasting
while providing agile accommodation for dynamic topology changes.
The seamless application communication between two vehicles or
between a vehicle
and an infrastructure node requires mobility management
in vehicular networks.
The mobility management schemes include a host-based mobility scheme,
network-based mobility scheme, and software-defined networking scheme.
In the host-based mobility scheme (e.g., MIPv6), an IP-RSU plays a role
of a home agent. On the other hand, in the network-based mobility scheme
(e.g., PMIPv6, an MA plays a role of a mobility management controller
such as a Local Mobility Anchor (LMA) in PMIPv6, which also serves
vehicles as a home agent, and an IP-RSU plays a role of an access router
such as a Mobile Access Gateway (MAG) in PMIPv6 .
The host-based mobility scheme needs client functionality in
IPv6 stack of a vehicle as a mobile node for mobility signaling
message exchange between the vehicle and home agent.
On the other hand, the network-based mobility scheme does not
need such a client functionality for a vehicle because the network
infrastructure node (e.g., MAG in PMIPv6) as a proxy mobility agent
handles the mobility signaling message exchange with the home agent
(e.g., LMA in PMIPv6) for the sake of the vehicle.
There are a scalability issue and a route optimization issue in the
network-based mobility scheme (e.g., PMIPv6) when an MA covers a
large vehicular network governing many IP-RSUs. In this case, a
distributed mobility scheme (e.g., DMM )
can mitigate the scalability issue by distributing multiple MAs in
the vehicular network such that they are positioned closer to
vehicles for route optimization and bottleneck mitigation in a
central MA in the network-based mobility scheme.
All these mobility approaches (i.e., a host-based mobility scheme,
network-based mobility scheme, and distributed mobility scheme) and
a hybrid approach of a combination of them need to provide an
efficient mobility service to vehicles moving fast and moving along
with the relatively predictable trajectories along the roadways.
In vehicular networks, the control plane can be separated from
the data plane for efficient mobility management and data forwarding
by using the concept of Software-Defined Networking (SDN)
.
Note that Forwarding Policy Configuration (FPC) in ,
which is a flexible mobility management system, can manage the
separation of data-plane and control-plane in DMM.
In SDN, the control plane and data plane are separated for the
efficient management of forwarding elements (e.g., switches and
routers) where an SDN controller configures the forwarding elements
in a centralized way and they perform packet forwarding according to
their forwarding tables that are configured by the SDN controller.
An MA as an SDN controller needs to efficiently configure and
monitor its IP-RSUs and vehicles for mobility management,
location management, and security services.
The wireless and/or wired-line links in paths between both mobile
nodes and fixed network correspondents may configure a variety of
Maximum Transmission Units (MTUs), where all IPv6 links are required
to support a minimum MTU of 1280 octets and may support larger MTUs.
Unfortunately, determining the path MTU (i.e., the minimum link MTU
in the path) has proven to be inefficient and unreliable due to the
uncertain nature of the loss-oriented ICMPv6 messaging service used
for path MTU discovery. Recent developments have produced a more
reliable path MTU determination service for TCP
and UDP however the MTUs discovered are
always limited by the most
restrictive link MTU in the path (often 1500 octets or smaller).
The AERO/OMNI service addresses the MTU issue by introducing a new
layer in the Internet architecture known as the "OMNI Adaptation Layer
(OAL)". The OAL allows end systems that configure an OMNI interface
to utilize a full 65535 octet MTU by leveraging the IPv6 fragmentation
and reassembly service during encapsulation to produce fragment sizes
that are assured of traversing the path without loss due to a
size restriction. (This allows end systems to send packets that are
often much larger than the actual path MTU.)
Performance studies over the course of many decades have proven that
applications will see greater performance by sending smaller numbers
of large packets (as opposed to larger numbers of small packets) even
if fragmentation is needed. The OAL further supports even larger packet
sizes through the IP Parcels construct
which provides "packets-in-packet" encapsulation for a total size up
to 4MB. Together, the OAL and IP Parcels will provide a revolutionary
new capability for greater efficiency in both mobile and fixed networks.
On the other hand, due to the high dynamics of vehicular networks,
a high packet loss may not be able to be avoided. The high packet
loss on IP parcels can simultaneously cause multiple TCP sessions
to experience packet re-transmissions, session time-out, or
re-establishment of the sessions. Other protocols such as MPTCP and
QUIC may also experience the similar issue. A mechanism for
mitigating this issue in OAL and IP Parcels should be considered.
This work was supported by Institute of Information &
Communications Technology Planning & Evaluation (IITP) grant funded by
the Korea MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based
Security Intelligence Technology Development for the Customized
Security Service Provisioning).
This work was supported in part by the MSIT, Korea, under the ITRC
(Information Technology Research Center) support program
(IITP-2022-2017-0-01633) supervised by the IITP.
This work was supported in part by the IITP (2020-0-00395-003, Standard
Development of Blockchain based Network Management Automation Technology).
This work was supported in part by the French research project DataTweet
(ANR-13-INFR-0008) and in part by the HIGHTS project funded by the
European Commission I (636537-H2020).
This work was supported in part by the Cisco University Research Program Fund,
Grant # 2019-199458 (3696), and by ANID Chile Basal Project FB0008.
This document is a group work of IPWAVE working group, greatly benefiting
from inputs and texts by Rex Buddenberg (Naval Postgraduate School),
Thierry Ernst (YoGoKo), Bokor Laszlo (Budapest University of Technology
and Economics), Jose Santa Lozanoi (Universidad of Murcia), Richard Roy (MIT),
Francois Simon (Pilot), Sri Gundavelli (Cisco), Erik Nordmark, Dirk von Hugo
(Deutsche Telekom), Pascal Thubert (Cisco), Carlos Bernardos (UC3M),
Russ Housley (Vigil Security), Suresh Krishnan (Kaloom), Nancy Cam-Winget
(Cisco), Fred L. Templin (The Boeing Company), Jung-Soo Park (ETRI), Zeungil
(Ben) Kim (Hyundai Motors), Kyoungjae Sun (Soongsil University), Zhiwei Yan
(CNNIC), YongJoon Joe (LSware), Peter E. Yee (Akayla), and Erik Kline.
The authors sincerely appreciate their contributions.
The following are co-authors of this document:
Nabil Benamar -
Department of Computer Sciences,
High School of Technology of Meknes,
Moulay Ismail University,
Morocco,
Phone: +212 6 70 83 22 36,
Email: benamar73@gmail.com
Sandra Cespedes -
NIC Chile Research Labs,
Universidad de Chile,
Av. Blanco Encalada 1975,
Santiago,
Chile,
Phone: +56 2 29784093,
Email: scespede@niclabs.cl
Jerome Haerri -
Communication Systems Department,
EURECOM,
Sophia-Antipolis,
France,
Phone: +33 4 93 00 81 34,
Email: jerome.haerri@eurecom.fr
Dapeng Liu -
Alibaba,
Beijing, Beijing 100022,
China,
Phone: +86 13911788933,
Email: max.ldp@alibaba-inc.com
Tae (Tom) Oh -
Department of Information Sciences and Technologies,
Rochester Institute of Technology,
One Lomb Memorial Drive,
Rochester, NY 14623-5603,
USA,
Phone: +1 585 475 7642,
Email: Tom.Oh@rit.edu
Charles E. Perkins -
Futurewei Inc.,
2330 Central Expressway,
Santa Clara, CA 95050,
USA,
Phone: +1 408 330 4586,
Email: charliep@computer.org
Alexandre Petrescu -
CEA, LIST,
CEA Saclay,
Gif-sur-Yvette, Île-de-France 91190,
France,
Phone: +33169089223,
Email: Alexandre.Petrescu@cea.fr
Yiwen Chris Shen -
Department of Computer Science & Engineering,
Sungkyunkwan University,
2066 Seobu-Ro, Jangan-Gu,
Suwon, Gyeonggi-Do 16419,
Republic of Korea,
Phone: +82 31 299 4106,
Fax: +82 31 290 7996,
Email: chrisshen@skku.edu,
URI: https://chrisshen.github.io
Michelle Wetterwald -
FBConsulting,
21, Route de Luxembourg,
Wasserbillig, Luxembourg L-6633,
Luxembourg,
Email: Michelle.Wetterwald@gmail.com