Download NSF_Vehicles_and_Internet_role-jan_16_Claudio

NeTs-FIND Collaborative Research:
Emerging Vehicle Networks: new roles for the Internet
Team: UCLA, Rutgers, UA
Deadline Jan 22, 2007
1
Summary
Vehicle communications are becoming increasingly popular, propelled by navigation safety requirements and by the
investments of car manufacturers and Public Transport Authorities. As a consequence many of the essential vehicle
grid components (radios, Access Points, spectrum, standards, etc.) will soon be in place (and paid for) paving the
way to unlimited opportunities for car-to-car applications. In this study, we take a visionary look at these emerging
applications and examine the role of the Internet infrastructure in their support. The type and level of support will
vary depending on the application. For instance, during e-mail downloading the vehicle is just a one hop wireless
extension of the Internet. While, during Katrina type emergencies that knock out the infrastructure, the vehicular net
will operate like a pure ad hoc network, yet, other applications such as location sensitive content sharing (eg,
advertisements) rely on both Internet access and on Peer to Peer, “opportunistic” networking. It is conceivable that
in the future most access will be from mobile (or at least portable) terminals. Thus, it is important to understand
what new requirements are posed to the Internet by “mobile” applications.
The main goal of this project is to identify the urban Internet infrastructure role in the support of the emerging
vehicular applications. In fact, the ubiquitous presence of the infrastructure sets the vehicle grid apart from
traditional, instantly deployed ad hoc nets, even when the vehicle network is operated in ad hoc mode. As the
vehicular applications range from e-mail and voice over IP to emergency operations (natural disaster, terrorist
attack, etc), the services requested from the infrastructure will vary. We investigate the impact of the Internet
infrastructure in the following areas: (a) addressing – namely, geo addressing versus more traditional hierarchical
addressing; (b) directory service support, service discovery, mobile resource monitoring, and mobility management;
(c) congestion management; (d) path quality monitoring and QoS support; (e) privacy, anonymity, incentives; (f)
smooth transition to fully independent, emergency mode operation (eg, fall back directory service in case the
infrastructure fails).
The required Internet services span the network and transport layers. The network services will be implemented via
overlays or in Planet Lab.
To achieve our goal, a critical task of this project will be to identify and characterize the vehicle applications, and
in particular their Internet services needs. We will select a set of representative vehicular applications that have
appeared in the literature and will analyze their performance requirements in the very challenged urban
environment. These applications are supported by a variety of network and transport protocols that include network
coding, epidemic dissemination, geographic routing, TCP, UDP, etc. The novel security issues posed by the mobile
nature of the applications will also be considered, and representative solutions will be selected for this study. Since
mobility plays a key role, a substantial effort will go into the development of realistic motion models. An
overarching goal of this task is to define guidelines for the design of new applications so that they can best exploit
the Internet infrastructure while being capable of fully autonomous operation in case of total Internet failure.
A key component of this project is a Campus vehicular testbed that implements the above mentioned vehicle
protocols. The testbed will support P2P vehicle communications in a pure ad hoc, multihop fashion. It will also
interface to the Internet interconnection. The Campus testbed will interface with Internet overlays and with
PlanetLab. In addition to the physical Campus tesdbed, we will use a simulation testbed and hybrid emulation
testbed. The latter test facilities will heavily leverage existing equipment and tools developed at UCLA under the
NSF sponsored WHYNET project.
The intellectual merits of the project are: the identification, implementation and evaluation of critical Internet
services required by the emerging vehicular environment, and; the definition of guidelines for the design of new
applications that can smoothly interface with the Internet. The study will characterize the vehicle performance
requirements and will generate benchmarks for evaluating and comparing new Internet services. This project will
have an important educational impact. The Campus testbed experiments will be integrated into class projects,
encouraging U/G individual study and graduate level research into vehicular communication, routing and security
issues. As for broader impact on Society, car manufacturers will use our findings to develop safer cars and more
productive mobile-offices. Transport Authorities will manage vehicle traffic more efficiently with reduced transfer
delays for the benefit of the urban population at large.
Prior Research results
Mario Gerla has been the PI on “Scalable Routing and Multicast in Mobile Ad Hoc Wireless Networks” (NSF
9814675, 2000-2002, $300K), which led to the design of the scalable routing protocol LANMAR and the very
robust multicast protocol ODMRP. Both protocols have been presented at MANET IETF working group meetings.
Project papers and results are found in www.cs.ucla.edu/NRL.
OPTIONAL: Additional prior results by Ray, Marco , Giovanni, Xiao Yan
1. Introduction and Project Overview (2 pages)
Safe navigation support through wireless car to car and car to curb communications has become an important
priority for Car Manufacturers as well as Municipal Transportation Authorities and Communications Standards
Organizations. New standards are merging for car to car communications (DSRC and more recently IEEE 802.11p).
There have been several well publicized testbeds aimed at demonstrating the feasibility and effectiveness of car to
car communication safety. For instance, the ability to rapidly propagate accident reports back to oncoming cars on
the highway, the awareness of unsafe drivers in the proximity and the prevention of intersection crashes.
The availability of powerful radios on board of vehicles, and of abundant spectrum (when not used for emergencies)
will pave the way to a host of new applications for the “vehicle grid”. These emerging applications span many
fields: extended office (e-mail, file transfers, group work), entertainment (mobile internet games, multimedia, news),
e-commerce (mobile shopping), crime investigation, civic defense, etc. Some of these applications are just mobile
extension of fixed internet applications (eg, e-mail, games). Others are location “aware”, ie, correlated to
neighborhood resources and services (ex, restaurants, movie theaters, etc). Others yet involve not only “awareness”
of the environment but also a close “cooperation” among cars, leading for instance to maintenance of distributed
indices, creation, “temporary” storage and “epidemic” distribution of sharable content. Examples of the latter class
include the collection of “sensor data” by cars acting as “mobile sensor platforms”; the sharing and streaming of
files using “Car-torrent” P2P software, and; the creation/maintenance of massively distributed commercial,
entertainment and culture information data bases.
How can the Internet better support the vehicles? This is a legitimate question since the Internet was originally
designed for fixed Hosts. Today, the great majority of Hosts are movable, if not moving. One expects that because
of mobility some additional network services will be required. Let us consider for example the most basic vehicular
applications that are a simple, one hop mobile extension of conventional fixed Internet applications, eg e-mail. In
this case, the vehicle initiates the connection, thus simplifying the addressing and mobility management issue. An
extension of the DHCP model can be used. If the urban cell is small and the vehicle speed is high, it may be
necessary to use address tunneling (or IPV6) to maintain the connection during the handoff from one cell to another.
Soft handoff becomes critical if the car is downloading real time video (eg. video conference, or news clip
downloading, etc). The server may also wish to “probe” capacity to mobile, to determine the current allowed data
rate. Moreover, the user may wish to conceal its location from the server, thus, there is the additional anonymity
requirement.
Consider now another application, this time inspired to civilian protection. Suppose there has been a bomb threat,
and a number of police vehicles are dispatched to patrol an area of the city a few miles in diameter. Agents need to
exchange with each other multimedia data picked up by their vehicles (video, sensor data, position, etc). Moreover,
they need to contact possible witnesses and download multimedia data from them. This operation requires vehicle to
vehicle connections over multiple hops. If the distance is significant, the Internet may used as a shortcut for part of
the path, exploiting integrated routing via the ad hoc net and the infrastructure.
From these simple examples we note that the Internet services must be extended to provide: (a) addressing – namely,
geo addressing versus more traditional hierarchical addressing; (b) directory service support, service discovery,
mobile resource monitoring, and mobility management; (c) path quality monitoring and QoS support; (d) security
support (anonymity). We will see later that other important requirement will emerge including: congestion
management, and; smooth transition to fully independent, emergency mode operation (eg, fall back directory service
in case the infrastructure fails).
In this project, we will address the interaction and synergy of the vehicle applications and protocols with the Internet
infrastructure. In particular, we will investigate the issue of addressing (eg transparent geo-routing) across the
Internet. Related to addressing is the maintenance of a vehicle location service both in the Internet and in the
vehicular grid. Most of the Internet services in our study will be supported by a “vehicle overlay” that, among other
functions, will offer the ability to estimate the (continuously changing) path quality to vehicles. These results will
provide useful inputs to the design of the future Internet architecture based on vehicle needs. Our plan is to exploit
our existing WHYNET testbed (separately funded by NSF), properly augmented with a physical Campus Vehicle
Testbed (C-VET) in order to evaluate the vehicle P2P protocols and their interworking with the infrastructure
Internet protocols. Likewise we will leverage WHYNET and on ongoing NSF and PATH funded projects for
physical and MAC layer designs required for the vehicular testbed implementation. The collaboration with Rutgers
will also open the opportunity to use the Rutgers ORBIT emulation platform as well as the Rutgers Vehicle Testbed
currently under development.
The rest of this proposal is organized as follows. Section 2 reviews related work and recent trends in vehicular
network and transport protocols. Section 3 reviews vehicle applications and defines a representative set, to serve as
starting point for our research. Section 4 describes the three main research directions of this project, namely: (1)
vehicular protocol and architecture extensions that relate to Internet interfacing; (2) vehicle oriented Internet
services, and; (3) vehicular test-bed and related experiments.
2. Related work in vehicle networks (1-2 pages)
Note: more work needed about previous research (including ours in WICON 06) on interaction
of VANET with Internet Infrastructure; also, security, incentives etc. Uichin Lee, Claudio
Palazzi, JS Park, Alex,
Much of the literature on Inter-Vehicle Communications (IVCs) is navigation safety related. A good survey on
recent physical layer technologies for IVCs can be found in [Luo04]. At the network layer, the most common way to
broadcast safety messages is via reliable, robust flooding. However, the efficiency of flooding quickly decreases
with the number of nodes; thus, flooding must be scope-limited. For scalable delivery, researchers have proposed
georouting and further, have focused on exploiting innate characteristics of vehicular networks such as high, but
restricted mobility. For example, Urban Multi-hop Broadcast (UMB) [Korkmaz04] features a form of redundant
flood suppression scheme where the furthest node in the broadcast direction from a sender is selected to forward and
acknowledge the packet. The scheme alleviates broadcast storm and hidden terminal problems. In [Wischhof05],
vehicles collect only the information relative to a given locality (i.e., a road segment). The paper further investigates
the influence of broadcast rate on data propagation taking mobility into account and adapting the rate to traffic
conditions. In this field, we have proposed a scheme by which each vehicle is able to estimate its transmission range
and to put it to good use to reduce redundant transmissions and the number of hops a broadcast message has to
traverse to cover a certain area of interest or reach a certain geographical location. As a result, broadcasting traffic
and delays are reduced thus allowing efficient delivery of, for instance, alert messages for traffic safety applications
and video triggering messages for entertainment and first responders operations [PFRPG07] [RGPFP07].
and in the and redundant transmissions the time required to broadcast a certain message over a certain area of
interest. Inumber of hops
For point to point unicast communications, geo-routing has been extensively investigated. A critical issue is the
relaxing of beacon message requirements (and associated overhead). [Füßler03] proposed Contention-Based
Forwarding (CBF). This scheme does not require proactive transmission of beacon messages for current location
advertisements; instead, data packets are broadcast to all direct neighbors and the neighbors themselves decide if
they should forward the packet based on a distributed timer-based contention process. A similar approach was
proposed by Zorzi in GeRAF[Zorzi03] exploiting staggered MAC inter-segment intervals. In [LeBrun05], the
authors proposed a set of knowledge-based opportunistic forwarding protocols that use geographic information such
as motion vectors. [Zhao06] proposes to reduce the delay to a known destination through mobility prediction.
Finally, geocasting services were proposed to disseminate messages to all nodes within a target region. MDDV
[Wu04] aims to support geocast by forwarding a packet along a predefined trajectory geographically. It works even
with intermittent connection; intermediate vehicles must buffer and forward messages opportunistically, exploiting
mobility. Abiding Geocast [Maihöfer05] features a lifetime constraint; namely, it restricts the delivery of messages
to all the nodes that are in the geocast region “sometime” during the geocast lifetime.
At the applications level, several cooperative peer to peer type schemes have been proposed for vehicular
environments. TrafficView[Nadeem03] disseminates (through flooding) and gathers information about the vehicles
on the road, thus providing real-time road traffic information to drivers. To alleviate a broadcasting storm problem,
this work focused on data aggregation based on distance from the source. EZCab [Zhou05] is a cab booking
application that discovers and books free cabs through vehicle multi-hopping. Free cabs are discovered with
probabilistic flood search (static or decreasing probability as hop count increases). After discovery, georouting is
used to negotiate the fare etc. [Xu04] proposed an opportunistic resource discovery protocol with a finite-buffer
space model. The resource is a spatio-temporal resource, e.g., the availability of parking in a parking lot. A vehicle
either “senses” the resources or obtains new resources from passing vehicles. Nodes exchange local databases and
each keeps a fixed number (the size of buffer) of relevant resources. In PeopleNet [Motani05], a wireless virtual
social network is used to support searching for spatio-temporal information, yet it exchanges resources by random
swapping. Vehicular Information Transfer Protocol (VITP) [Dikaiakos05] provides on-demand, location-based,
traffic-oriented services to drivers using information retrieved from vehicular sensors. A user “location-aware”
query is forwarded to the target location where virtual ad hoc servers (VAHS), i.e., collection of private vehicles,
resolve the query.
3. Proposed Research (7 pages)
3.1 Vehicular Applications and internet requirements (2pages)
Note: this section must be reduced and better focused (Mario to take a crack at this Monday
PM)
3. 1.1 Vehicle Protocol Requirements and challenges
Vehicular networks provide a promising platform for future deployment of large-scale and highly mobile ad hoc
network applications. With the increasing deployment of urban wireless access points, the application domain of
traditional mobile and ad hoc networks (MANET) is giving way to wireless mesh networks that extend wireline
connectivity to the Internet. Vehicular ad hoc networks (VANET), however, remain a largely unexplored platform
for a class of compelling applications. Given the automobile’s role as a critical component in peoples’ lives,
embedding software-based intelligence into them has the potential to drastically improve the user’s quality of life.
This, along with significant market demand for more reliability, safety and entertainment value in automobiles, has
resulted in significant commercial development and support into deployment of vehicular networks and applications.
In this section, we outline key differences that distinguish the vehicular platform, introduce applications by their
interactions with data, and describe a number of constraints and challenges for the vehicular application
infrastructure.
In designing protocols for the next generation vehicular network, we recognize that nodes in these networks have
significantly different characteristics and demands from those in traditional wireless ad hoc networks deployed in
infrastructureless environments (e.g. sensor field, battlefield, etc). We identify several key differences from
traditional ad hoc networks with significant impact on application infrastructures. First, automobiles have much
higher power reserves than a typical mobile computer. Power can be drawn from large on-board batteries, and
recharged as needed from a gasoline or alternative fuel engine. Second, automobiles are orders of magnitude larger
in size and weight compared to traditional wireless clients, and can therefore support significantly heavier
computing (and sensorial) components. This combined with plentiful power means vehicular computers can be
larger, more powerful, and support components such as large capacity secondary storage (up to Terabytes of data),
as well as powerful wireless transceivers capable of delivering wire-line capacities to mobile peers and satellite
access points. Third, automobiles travel at speeds up to one hundred miles per hour, making sustained vehicle-tovehicle communication difficult. However, existing statistics of vehicular motion, such as traffic patterns during
commute hours, can be used to develop sophisticated mobility models much more realistic than the current random
waypoint models. By accurately characterizing vehicles’ tendencies to travel together, these models can help
maintain connectivity across mobile vehicular groups.
In addition, vehicles’ extremely high rates of mobility reduce the reliability of hardware components. Networking
and storage components are particularly vulnerable. The large storage capacities mean the loss of data availability is
higher for each storage or network component failure. Finally, vehicles in a grid are always a few hops away from
the Infrastructure (WiFi, cellular, satellite, etc). Thus, network protocol and application design must account for easy
access to the Internet during normal operation. In our project, we also consider the value of the vehicle grid as
emergency network when all else fails. We must therefore design protocols and applications that survive (with
possible degraded performance) when isolated from the Internet.
3.1.2 Innovative Applications
Another important departure of vehicle networks from conventional ad hoc networks is the opportunity to deploy, in
addition to traditional applications, a broad range of innovative content sharing applications (typically referred to as
Peer-to-Peer applications). While their popularity has been well documented, they have been thus far confined to the
fixed Internet (e.g., Bit Torrent, etc). The storage and processing capacity of VANET nodes make such applications
feasible. Moreover, the fact that car passengers are a captive audience provides incentive for content distribution and
sharing applications that would be unsuitable to other ad hoc network contexts.
One of the key goals of this project is to understand the role of the vehicle in these applications, that is, to determine
what VANET applications, both conventional and peer-to-peer, need from their infrastructure. Here, we describe a
representative set of VANET P2P applications and classify them by the vehicle’s role in managing data: as a data
source, data consumer, source and consumer, and intermediary.
First, the vehicle provides an ideal platform for mobile data gathering especially in the context of monitoring urban
environments. Each vehicle can sense events (e.g., images from streets or the presence of toxic chemicals), process
sensed data (e.g., recognizing license plates), and route messages to other vehicles (e.g., forwarding notifications to
other drivers or police officers). Because vehicular sensors have few constraints on processing power and storage
capabilities, they can generate and handle data at a rate impossible for traditional sensor networks. We can also
exploit mobility to opportunistically diffuse concise summaries or metadata of sensor data. These can be harvested
by other agents to construct a low-cost, distributed and scalable data index. Finally, vehicular sensors augmented
with remote control are ideal for monitoring inhospitable environments such as unexplored battlefields or scenes of
disasters. These applications all require persistent and reliable storage of data for later retrieval.
Second, the vehicles can be significant consumers of content. Their local resources are capable of supporting high
fidelity data retrieval and playback. Since drivers and passengers are stationary for the duration of each trip, they
make up a captive audience for large quantities of data. Examples include locality-aware information (map based
directions) and content for entertainment (streaming movies, music and ads). These applications require high
throughput network connectivity and fast access to desired data.
In a third class of compelling applications, vehicles are both the producers and consumers of content. Examples
include services that report on road conditions and accidents, traffic congestion monitoring, and emergency neighbor
alerts, e.g. my brakes are malfunctioning. We note that their direct relevance to road safety makes them a high
priority for commercial entities. These applications require real-time and location-aware data gathering and
dissemination. Finally, all of the above applications will need to rely on vehicles in an intermediary role. Individual
vehicles in a mobile group setting can cooperate to improve the quality of the applicant experience for the entire
network. Specifically, vehicles will provide temporary storage (caching) for others, as well as forwarding of both
data and queries for data. In this capacity, they require reliable storage as well as efficient location of and routing to
data sources and consumers.
The demands of these applications give us a list of requirements and challenges for vehicular applications. Note that
we can leverage them to simplify the applications infrastructure.

Time sensitivity: Time-sensitive data must be retrieved or disseminated to the desired location within a given
time window. Failure to do so renders the data useless. This mirrors the needs of multimedia streaming across
traditional networks, and we can leverage relevant research results from the related areas.

Location awareness: Both data gathered from vehicles and data consumed by vehicles are highly locationdependent. This property has direct implications on the design of data management and security components.
Data caching and indexing should focus on location as a first order property; while data dissemination must be
location-aware in order to maintain privacy and prevent tampering.
A number of significant research challenges remain:

Time-sensitive dissemination of data to and from vehicles

Efficient data indexing and query mechanisms using location and secondary characteristics

Reliable and persistent network-based storage in the presence of node churn (movement in and out of local
mobile groups) and unreliable hardware

Reliable location-based communication in the presence of high vehicular mobility, intermittent connectivity
and lossy channels
As we focus on addressing these challenges, we will integrate a number of existing tools, including geo-routing
protocols, network coding and realistic mobility models. We will examine the problem from a number of different
perspectives, including those of security, interactions with the infrastructure, and overall impact on the Internet
architecture.
3.1.3 Representative VANET applications
The vehicle grid applications pose new challenges on the ad hoc vehicle network. They can benefit from the design
and development of new protocols. This section covers the main research directions in the applications and protocols
area
3.1.3.1 Content downloading
Please revise and update, with the network layer impact in mind JS Park, Uichin
As we discussed in the previous section, several emerging applications involve peer to peer content distribution.
Content is distributed in the vehicle grid in different ways and for different purposes: (a) the car explicitly requests
(pulls) segments of a “popular” multimedia file, from an access point or from neighbors (eg, car torrent); (b) the
access point and the cars “push” location relevant content using epidemic dissemination and “data muling” (ad
torrent) ; drivers in turns “opportunistically” request specific data items when they need them (eg, ad torrent); (c)
multimedia data is streamed from cars on the scene of an accident (eg, collision slide, flood, fire, etc) back to the
oncoming cars, as a warning and to allow them to take diverse routes.
The above applications are very different in nature. However, they share a common model. The data files are
downloaded from one or more sources to one or more receivers, using intermediate store and forward nodes. In CarTorrent for example [wons 05], a car decides that it can cooperatively assemble the desired file using P2P content
sharing. One option is for the car to query the neighborhood (say up to K hops deep) for the missing segments. The
car selects the “best” peer for download. Simulation experiments[NDPG05] shows that the best strategy combines
closeness and rarity of the “piece” (while Bit Torrent generally selects the “rarest” piece). This however involves
quite a bit of O/H. There is first the selection of the peer (one query and several response); then, the TCP transfer of
the multi-piece segment (typically, with several retransmissions). Another way to download pieces exploits network
coding [GKANMR06]. The K-hop query goes out as before. However, there is no selection. Each peer with
”pieces” of the requested file delivers a random XOR combination of its current pieces (we assume each piece is
exactly one packet long). Intermediate nodes also participate in the “random” mixing of pieces. A prefix in the
packet tells the weights of the linear combination. If the car requests 5 missing pieces, then peers will deliver as
many as 5 packets (if they have all those missing pieces). The receiver then can recover the pieces by solving a
linear system of equations. The network coding scheme offers several advantages. It drastically reduces the number
of messages and thus the overhead. One request is sufficient to collect multiple pieces, as opposed to one request per
piece. No TCP is required; just UDP. In fact, TCP will not work with multiple simultaneous sources. If the receiver
does not have enough packets to solve the equations (some packets may have been lost), it simply requests more
random combinations, as opposed to requesting specific packets.
Another application that features downloading from multiple neighbors is “Ad Torrent” [ mobiquitous 05]. Say, a
driver needs to find out which movies are playing in a particular neighborhood, along with videoclips. Also, the
driver wants to dine at an Italian restaurant after the movie. Videoclips, menus, restaurant reviews and address
must be acquired within latency constraints. Driving to the access point each time is too time consuming. Multihop
downloading from a remote access point may not be practical and may create excessive load on the system. As an
alternative, in Ad Torrent the access point feeds passing cars with randomly selected “ad segments”. Next, each car
probabilistically disseminates the pieces using an epidemic ( “gossip”) scheme (we later review the effectviness of
epidemic dissemination in the vehicular context). As a result the neighborhood becomes populated with ads. Again,
there are different neighbor download strategies. One method [Nandan06] is to query the neighborhood and
selectively download pages using Bloom Filters. Another approach is to query the neighbors and solicit network
coding downloads of whatever useful pieces they have. The main difference from Car Torrent is that Ad Torrent
epidemically disseminates segments (to increase the hit ratio of even not so popular files); also, it downloads
from”3rd party” peers who are not trying to assemble the information themselves. This may have impact on tit-for-tat
bookkeeping.
There is also content distribution related to navigation safety. Suppose that a critical traffic/safety situation occurs on
a higway, say, major traffic congestion, weather condition, fire, act of war or natural disaster. In such cases,
multimedia content, say, video, could be streamed from one or more lead cars to the vehicles following several miles
behind – to “visually” inform them of the problem and allow them to decide if they should turn around.
Conventional ad hoc broadcast (eg, via ODMRP or MAODV) may introduce excessive loss and severely impair
video reception. This is a situation where network coding can enhance stream reliability. To this end, we have
recently developed an ad hoc Network Coded broadcast scheme called CodeCast that improves reliability through
localized neighbor recovery and path diversity. The following graphs show preliminary results of CodeCast in a 100
node ad hoc network with random way-point mobility. CodeCast yields 100% delivery ratio as compared to 98% by
ODMRP. Such accomplishment is achieved with less overhead. The end-to-end delay is increased, but yet within
acceptable stream quality constraints.
In the proposed project, we will extend CodeCast to vehicle networks.We will evaluate and compare traditional
distribution schemes versus Network Coding under different car density, speed, file popularity and motion pattern.
Performance measures are the delay to assemble the file and the total traffic O/H. Both analytic and simulation
models will be developed [Nandan06].
CodeCast vs ODMRP: Normalized Overhead
1.02
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Packet Delivery Ratio
CodeCast vs ODMRP: Packet Delivery Ratio
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3.1.3. 2 Vehicular sensor platforms and Epidemic dissemination
Please revise and update, with the network layer impact in mind Uichin
Vehicular networks are emerging as a new network paradigm of primary relevance, for example for proactive urban
monitoring using sensors and for sharing and disseminating data of common interest. Each vehicle can sense one or
more events (e.g., imaging from streets and detecting toxic chemicals), process sensed data (e.g., recognizing license
plates), and route messages to other vehicles (e.g., diffusing relevant notification to drivers or police agents).
Opposed to traditional wireless sensor platforms, vehicles can generate such a large volume of data that can hardly
be handled by traditional sensor network approaches (eg, periodic reporting to sinks). In this proposal, building upon
previously proposed techniques for epidemic information dissemination in mobile ad hoc networks with pedestrian
mobility [PS01], [LW04], we explore alternative lightweight strategies for proactive urban monitoring. The basic
idea is to exploit vehicle mobility and limited broadcast to opportunistically diffuse concise summaries (meta data)
of the sensor inputs or some general kind of lookup information for data stored in cars. Note that such lookup
information is typically only valid within a short time lapse and, thus, may well require some mechanisms for
coherency.
As a first application scenario, similar to [Xu04] parking lot model, consider the very time consuming problem of
finding a parking spot in a large urban area. Suppose cars are equipped with street maps; moreover, parking slots at
curbside advertise when they are free via beacons. Then, the cars that are driving through downtown (and most
likely looking for parking) can share this information in a sort of distributed directory. As a second scenario,
consider that police agents harvest sensor inputs and lookup information, and build a low-cost, distributed, scalable
index [PerSense]. This forensic data can be very valuable in many ways: from identification of communing patterns,
to rush hour traffic behavior, to crime investigations.
To support commercial applications, a vehicular network must provide basic services widely deployed in the
Internet. Examples include communication utilities like email and instant messaging as well as services like web
caching and content delivery. In a vehicular network, it is not clear which node (a wired node, a wireless proxy or a
redundant set of nodes) should provide server-like functionality due to intermittent connectivity. In many cases, the
only feasible approach for implementing a client-server application consists in the distribution of the server
functionality among all participating nodes. Namely, Internet client-server applications require P2P cooperation
when moved to the vehicular network. This leads to the third application scenario, instant messaging (IM) for a
vehicular network. As a difference from previous services, this is a “delay sensitive“ application. “Presence”
technology enables users of an IM system to determine if their contacts are online, signed onto the IM application,
and ready to communicate. The protocol design for disseminating presence information in the Internet has been
matured and organizations such as the IETF and the Jabber software foundation have developed protocol standards.
However, due to the dynamic network topology and the lack of fixed infrastructure the dissemination of presence
information in vehicular network poses a challenging research problem.
In the area of vehicular dissemination several research issues will be addressed. First, how should epidemic
information dissemination be tailored to application constraints (ie delay sensitive or delay-insensitive, coherency
required or not, etc.), and to network constraints such as node density and mobility pattern (group mobility or
individual mobility). Secondly, we will compare the performance of pure epidemic methods with hybrid methods
based on epidemic dissemination and controlled flooding. Thirdly, we will investigate hierarchical schemes
combining epidemically generated indexes with higher level structured indices (eg GHTs and DHTs). Finally,
building up on [LW05] we will develop models that characterize the dynamics of gathered data with their coherency
and real-time constraints.
3.1.3.2 Urban mobility models
Please revise and update, with the network layer impact in mind Kelvin
The Random Waypoint (RWP) mobility model with pauses [Johnson96], [LeBoudec05] is widely used in the
literature. In RWP, a mobile device starts at a random position drawn from a uniform distribution and moves to a
destination position also drawn from by a uniform distribution. The device speed is chosen uniformly from (0,vmax].
When the mobile device reaches the destination position, it holds for an amount of time chosen uniformly from
(0,Thold], before choosing a new destination position and continuing the process. Unfortunately, the RWP model in
its original definition [Johnson96] did not posses a steady-state node distribution and led to a non-uniform
distribution of mobile devices while they are moving [Bettstetter03], [LeBoudec05]. Even the improved definition
of [LeBoudec05] posses the latter shortcoming.
The Obstacle Mobility model proposed in [Jardosh03] extends the RWP model through the incorporation of
obstacles restricting node movement as well as wireless transmissions. The Obstacle Mobility model also bears the
intrinsic shortcomings of the RWP model. In the Manhattan mobility model proposed in [Bai03], the mobile node is
allowed to move along the horizontal or vertical streets. At an intersection of a horizontal and a vertical street, the
mobile node can turn left, right or go straight with certain probabilities.
All these mobility are inadequate to model the motion correlation among vehicles. Nodes in vehicle networks tend
to move in “convoys” along freeways/local streets. In such networks there is some random movement, but there are
also factors that tend to introduce correlation between individual trajectories, for example: group merge/split,
obstacles, traffic accidents, traffic lights, etc. To cope with these issues, we introduced reference point group
mobility (RPG, [Hong99]): In RGP, the mobile devices move in G groups that cover each a circular area with radius
rg. Groups move according to the random waypoint model with Thold = 0. Each mobile device is associated with a
reference point uniformly chosen from the area covered by the group. The mobile devices are placed at positions
that are randomly chosen from a circular area with radius rn around their reference point.
To capture the most representative features of a urban motion, building upon RGP, we propose a “track” based
group motion model. The track model is based on a continuous-time Markov Chain. The tracks are represented by
freeways and local streets. The nodes must move following the tracks. At each intersection (switch station) a group
can be split into multiple smaller groups; or may be merged into a bigger group. The track model allows also
individually moving nodes as well as static nodes. Such non-grouped nodes are not restricted by switch stations and
by real tracks. Instead their movements are modeled as random moves in the whole field. An important research
issue constitutes the derivation of a proper mathematical definition of the track model, so that the corresponding
continuous-time Markov chain possesses a steady-state (ie is ergodic).
The proposed track model will be tested with real freeway/street maps from the US census bureau. The results will
be verified with real urban traffic data from sigalert.com which monitors live traffic for big cities in California. The
model will then be integrated in our simulator and will be used in the experiments to investigate the impact of
motion on routing, TCP, index disseminations, etc. Preliminary results obtained with an early Track Model version
have shown orders of magnitude higher delay in epidemic dissemination convergence than the RWP model!
3.1.3.4. Robust transport (probably omit)
Please revise and update, with the network layer impact in mind JiWei
Most of the exchanges in the vehicle grid (for navigation safety or content sharing/dissemination) are broadcast or
many-to-one cast. Thus, they run on UDP. There are however occasional unicast file (data or multimedia) transfers.
The issue then arises of TCP efficiency over a mobile, multihop path. Unfortunately, performance and fairness of
TCP is poor over multihop wireless networks [FZL03]. This because wireless networks possess several properties,
which are different to the wired Internet for which the widely deployed TCP NewReno implementation has been
optimized. [XGQ03], [EKL05] proposed modifications to TCP for improving performance and fairness of TCP over
wireless multihop networks without mobility.
For vehicular networks route breakage due to the high mobility constitutes an additional major problem for TCP.
Fortunately, Geo-routings are more robust to highly dynamic route changes than conventional MANET routing
protocols considered in [HV99], [Xu04]. For best performance, however, several georouting parameters must be
carefully tuned (eg, hello message exchange rate, delay timer in TCP for out-of-order delivery, etc) [CG06].
We plan to apply the lessons learned from [CG06], [XGQ03], [EKL05] to the vehicle grid environment. To improve
hello efficiency in Georouting, we propose an adaptive hello exchange scheme based on node mobility. Then, we
propose to fix the out-of-order problem by using a receiver-side out-of-order detection and by properly calibrating
the parameters. Building upon [XGQ03], [EKL05], we will integrate an adaptive scheme into the TCP sender for
achieving almost optimal fairness among competing TCP flows. Subsequently, we will evaluate the impact of these
adjustments to vehicle unicast applications for various degrees of mobility.
3.2 Security considerations (1.5 pages)
Note: this section must be refocused to privacy and anonymity guarantees, and the assistance
from Internet (Xiao Yan)
Alex to overview the editing
Xiao Yan, if you can generate say, one page based on the bullets below, it would be great!
Roles of Internet in Vehicular Network Security (Xiaoyan)
New roles in security and privacy
Provide security infrastructure support
Opportunistic
Privacy-preserving
Provide VANET security surveillance
Provide additional VANET anonymity and privacy
I will need comments here for the following reasons:
(a) addressed privacy issues in the role 1,
(b) may contradict to geo addressing and routing
(c) if not (b), we achieve location privacy with sensitivity and performance tradeoff. (see the last
slide)
Task 1
To address: new roles to provide security infrastructure support
Opportunistic
Privacy-preserving
Proposed research:
Loosely coupled authentication
Defend DDoS (false/stale data injection in content distribution applications)
Enable security and privacy in network topology construction
Dual-mode authentication architecture
to support privacy-preserving authentication
task 2
To address: new roles in providing VANET security surveillance
Proposed research
Mobile DDoS attacker tracing
Scenarios: attackers surface at different APs to launch attack.
Extend traditional traffic analysis techniques to the vanet
Task 3
To address: new roles to provide additional VANET anonymity and privacy
Proposed research:
Builds on top of multi-resolution distributed location-service, perform fuzzy geo forwarding.
Note: the location-service can be provided jointly by Internet and VANET.
Note, the privacy is achieved with tradeoff of sensitivity (how fuzzy) and performance (delivery
ratio)
General vehicular network security is supported by security primitives like key distribution and message
authentication through Public Key Infrastructure [ZMTV02] [MBG05] [ABDF][HCL04] [D05]. Drivers can obtain
and update (say, annually) their pubic key certifications from registration authorities like
DMV[PP05][RH05][SHLP05]. Messages propagated within the network must be authenticated to prevent external
attackers from injecting, altering and replaying old messages (messages in vehicular grid are stamped with location
and time). One outstanding security problem is the location verification and bogus data detection[CH05][GGS04].
However, these general security measures do not solve many security issues regarding to the new applications
foreseen in the proposal. Our research tasks are to identify the security requirements for various applications, to
investigate the new security issues and to deal with the limitations of the vehicular networks in supporting security.
Two very critical issues we discuss here are the security of network coding and the security of content distribution.
Content distribution serves a variety of goals, ranging from traffic monitoring, hazard detection, to forensic
investigation. One critical security problem is to prevent, identify and reject false data in the distribution process.
More specifically we study the security of location and timestamp data that are very important parts of any record.
Bogus location information and/or wrong time stamps can cause huge disruption to queries and to decision making
over data collected from mobile sensor platforms. Sybil attack that counterfeits multiple identities [D02] to weaken
defenses built based on majority rule is mostly impossible since a malicious node cannot counterfeit a valid
certificate without the CA’s private key. Related secure data dissemination problem has been studied in sensor
networks. Solutions include preventing through secure aggregation [PSP03], detecting and filtering when packets
are en route[YLLZ04] [ZSJN04][V05]. All these schemes are based on static distributed symmetric secure key
sharing, which is not applicable in the highly mobile vehicular networks.
In vehicular networks, due to the lack of pair wise trustiness, secure locations and timestamps have to rely on a
collection of witnesses and use majority rule. To elude such a security testing system, a group of malicious nodes
must collude and generate witnesses for each other. In a dynamic vehicular network, excluding all good nodes from
the witness database will be very hard to sustain over a period of time. Thus such a validation system will be very
effective. Specifically, location can be verified through multilateration among base stations given the distance
bounding information [CH05]. However, the scheme relies on densely deployed roadside base stations. An
alternative way is to construct a graph with all the observations and mark the links according to assertions calculated
from the observations [GGS04]. A failed assertion could generate a label of “spoof” or “malicious”. This approach
applies to timestamps as well with a certain threshold to tolerate drifts among different clocks. The success of the
approach relies on rich inputs of observations. A third method is actually combining reputation methods [MGLB00]
with the above approach. Using matrix operation as presented for p2p network ranking incentive algorithm Tit-for-
Tat [LPYZ06], we will be able to evaluate both the data and the nodes. After all, these schemes have to be
integrated with epidemic dissemination scheme or CodeCast scheme. Evaluations must pay attention to impact from
possible insufficient observation inputs since the network is dynamic and highly mobile. We will also exploit
locality in motion to improve the success rate of detection and filtering.
Also, a section on incentives to be produced by JS Park, using CS 218 project results as basis
3.3 Network and Internet services (3.5 pages)
3.3.1 Address conventions + GLS (1.5)
Mario to edit this section, using inputs from Claudio, with advise from Marco.
A major challenge in the management of vehicular network mobility and interconnection to and through the Internet
is addressing. Let us begin by defining:
(a) Unique car name - Several options are possible here: license plate#; Vehicle-ID#; owner’s name. IP address can
occasionally be used an stored as temporary “unique” ID
(b) Routable car address: geo-coordinates; specific attribute (as in “attribute based” routing - eg, car torrent
membership); unique ID (typically IP address) for some type of routing , eg AODV
As earlier discussed, the most prominent routing in the vehicle grid is geo-routing. AODV may also be used over
short paths (few hops). (Note: AODV currently uses IP addresses to set up/maintain on demand routes). Thus, geoaddress is the dominant routable address in the vehicle grid. Internet type IP routing (ie, prefix routing etc) is
meaningless in an ad hoc network such as the vehicle grid. Yet, the IP address will still be useful as identifier in
AODV routing and in TCP connections. For this reason, we propose to maintain in the vehicle grid a “unique” IP
address for cars. The car IP address can be initialized for example (after a long inactive period) by hashing the Vehic
#, owner # and license #. Clearly, the result may not be unique. If address conflicts ever happen (during TCP
connection set up, or AODV routing), the tie is broken by re-hashing the IP address (ie, the IP address of a car may
change during lifetime). To avoid collisions in a proactive way, IP uniqueness within a local scope (say, 3-4 hops)
may be constantly verified and enforced by an elected IP master node. We assume there will no DHCP for cars
when they pass by Access Points. A DHCP address would be useless given the high car mobility.
We envision that the addressing scheme should support the following services:
(a) a car must be able to efficiently address any other car in the urban grid;
(b) an Internet server must be able to address any vehicles in the grid
One can easily show that geo-routing fits these requirements. More precisely, geo-routing takes a packet “in the
neighborhood” of the target destination. Once the packet is within radio reach, any unique node identifies (eg IP
address, or license number) can be used to deliver the packet to the node.
A critical component of the geo-routing address structure is the Geo Location Service (GLS) - a distributed service
that maps any car name to the set of most recent geo locations. We propose to implement two “parallel” version of
GLS, namely: OLS (Overlay Location Service) and VLS (Vehicle Grid Location Service). OLS is maintained within
the Internet infrastructure; VLS is maintained entirely in the vehicle grid. The two services are synchronized, but are
independently maintained to provide fault tolerance (one of the tenets of our proposed architecture)
Let us illustrate a possible OLS implementation. An overlay structure is established in the urban Internet. Each car,
whenever it passes by an AP, registers its ID (license#, IP address(es), time, owner name, owner IP address billing
address, etc) and the current geo-location. OLS maintains an index of IDs. Each ID is mapped to the geo
coordinates. The index is distributed. It may be managed via DHT (Distributed Hash Tables). Suppose now Host A
(fixed or mobile) wants to establish a TCP connection to mobile B. Host A first queries OLS with:
[email protected]
starting from the nearest server of the OLS “overlay”; it gets back the “most recent” geo-locations, the IP address,
etc of Car B. It predicts from recent locations the best current estimate for access point AP. Host A sends the msg to
the AP closest to the geo-destination (the overlay can perform the mapping); the message is encapsulated in an IPv6
network envelope that contains the geo address in the extended header. Routing in the Overlay is based on geo
address. Namely, the geo address determines the AP at the end of the Internet path. At destination, the AP georoutes the packet to the ad hoc net; the car responds with own IP and directs the response (encapsulated in the
overlay envelope) to the sender IP. Note that the encapsulation into a geo routed network envelope is identical
regardless whether the sending Host A is fixed or mobile.
In principle, one geo location server, say OLS, would be sufficient. However, since the urban Internet infrastructure
(or wireless access to it) may fail, we maintain also VLS in the Urban Grid. Considerable amount of research has
been done on VLS design. One must minimize registration overhead with minimizing at the same time index search
– two conflicting requirements. We propose to explore a new solution, based, like the others [GLS ] on a hierarchy.
At the lowest level, there is a unique (mobile) server – eg, a CalTran truck- that roams in a cell (1 km x 1 km),
periodically advertising its coordinates. Cars register locally with the truck. Periodic advertising precludes the well
known dead-ends of conventional geo routing. [Directional forwarding; Landmark assisted Geo Routing]. At the
higher level of the hierarchy, there may be as many as 1000 cells in a large metropolitan area (say 33 km x 33 km).
A car will geo-hash its license # in one of these cells (the permanent home cell, say). As the car moves from one cell
to another, it must update the pointer in its home cell. This is quite a bit of overhead, due to the inefficiency of geo
routing. During normal operations, when the infrastructure is up, home cell updating can be done through the
Internet overlay, at the same time when the OLS updating takes place. Least cost routing (via vehicle grid or
Internet) will also be explored.
In this project, we will explore the effectiveness of coordinated VLS and OLS structures. We will investigate
various hierarchic solutions for scalability. We will also implement OLS in the GRIDO testbed.
3.3.2Routing in the vehicle grid (1.5 pages)
Marco, can you please review the geo routing considerations?
Kelvin, please look at this as well
Most of vehicle grid applications we described so far require exchange of unicast or broadcast messages between
neighbors. For this type of proximity routing, on demand schemes such are AODV, ODMRP or even flooding are
adequate [aodv], [odmrp]. Some applications require unicast routing to destinations several hops away. If geocoordinates of the destination vehicle are obtained from a Geo Location Service, the “routable address” is the geoaddress and the packet is routed using geo-routing (eg, greedy forwarding). If instead the destination (eg, a web
server) is found using scoped flood search a la AODV, say, then the route to the server can be supported by routing
table entries, like in AODV (geo routing may also be used once the server coordinates are learned). As another
option, the destination might periodically advertise its presence (ie, proactive routing); then proactive table driven
forwarding is used.
From the above we note that the vehicle grid must support many routing options, the selection depending on the
name/address map scheme. The prominent scheme, especially to remote destinations, will be geo-routing. The
georouting implementation in vehicular grids still poses research challenges. The first issue is vulnerability to “dead
end” traps. Vehicle grids are full of such traps. Once GPSR falls in a trap, the recovery must be done with time
consuming “perimeter routing” schemes. One research issue on our agenda is to investigate schemes that
prevent/recover form traps. To this end, landmark assisted geo routing (GeoLanmar) can be used to warn nodes
when the direction “as the crow flies” leads to a trap. This is done by comparing the “Euclidian” direction with the
Landmark advertised direction. The advertised routes, however, may become stale if the refresh period is slow (to
keep O/H low). To achieve more durable routes, we recently proposed to use not the advertised next node (on the
route) but the advertised direction, ie “Direction Forwarding” [ad hoc net journal]. In this project, we plan to
examine the tradeoffs between increased route robustness and additional control traffic overhead for Landmark
Assisted Geo-routing and for Direction Forwarding, in typical urban grid topologies, motion behavior and traffic
patterns.
3.3.3 IP address auto-configuration (1.5 pages)
As already mentioned, any networking session (eg TCP) and application requires unique identifiers for peer
communications nodes (eg Vehicle ID No). Needless to say, this remains true even in the considered scenario of
urban vehicular grids. Historically, in the Internet, the IP address scheme was designed to represent both a unique ID
and a routable address. However, at that time the Internet and its hosts where far from being mobile. Nowadays,
instead, communication capabilities can be easily found on lightweight mobile devices and, very soon, even on cars.
The very high and fast mobility that characterizes this emerging scenario changes the initial design assumption at the
basis of the IP address. Indeed, major problems with maintaining sessions arise when routable address changes - ie
during handoff. To this aim, specific solutions have been proposed such as Mobile IP, IPv6, tunneling, etc. The
importance of the IP address with the new mobile scenario as not been weakened, as demonstrated also by its
utilization in MANETs as “unique” ID (for TCP, UDP, and at times even for routing, eg, AODV). On the other
hand, some tasks that have been successfully implemented in traditional networking systems require now the
development of new solutions aimed at implementing them even in vehicular or, more in general, mobile scenarios.
A prominent example of these tasks is represented by the IP address auto-configuration of nodes that leads to unique
IP addresses and that has to be performed even when employing IPv6 in place of the traditional IPv4 [RFC2462].
Auto-configuration of IP addresses, such that the assignment results unique, requires specific investigation for the
vehicle grid scenario. Indeed, the direct employment of solutions developed for regular ad hoc networks cannot be
directly applied to a vehicular scenario due to the peculiar characteristics of the latter: high density of nodes (many
cars in few meters on a highway or in town); high absolute speed (20-80mph) but low relative speed with respect to
other cars traveling in the same direction (3-20 mph); and practically “infinite” network diameter (millions of cars
could be present in a large metropolis).
The problem we need to address is hence that of creating an auto-configuration service able to efficiently support
vehicular networks guaranteeing the following properties:

high reliability (ie, low ID collision rate) of the address configuration;

low signal overhead generated by the system;

low configuration time (especially important traffic safety and real-time applications).
To this aim, typical decentralized approaches requires that all nodes in the network are involved in the address
configuration task by maintaining and exchanging a list of addresses which are currently in use or that are going to
be assigned to new nodes. [MP02], [NP02]. Obviously, distributing the information to all the nodes in the network
represents a solution that does not scale as it would generate a very high volume of control traffic to keep the
information updated and consistent if employed in large networks.
As an alternative, best effort approaches provide correct routing with a limited control traffic, yet, without ensuring
unique node addresses and thus generating serious delays when address duplications have to be solved among
sessions (say at TCP level, for instance). Probabilistic algorithms such as [Weniger2005] belong to this class. Their
aim is that of minimizing the address duplication probability and performing DAD (Duplicate Address Detection)
procedure when two nodes with duplicate addresses start to communicate.
A better solution is represented by leader based approaches. Solutions belonging to this hybrid class generally
implement a hierarchical structure to configure nodes and perform the DAD procedure only within a cluster
[Sun04], [Toner03]. Then, when leaders pass by the coverage area of an AP it could transfer to it information about
the addresses utilized by vehicles within its control range. In this way, georouting could be exploited to deliver
message to the right AP (when communications with the Internet are involved), whereas ongoing sessions (eg, TCP)
between cars or between a car and the Internet will be feasible thanks to the presence of the unique IP address.
We deem, and are aimed at demonstrating, that this kind of leader based approach represents an efficient scheme for
IP address auto-configuration. In particular, we envision a scheme that will work with leaders proactively organized
in a chain and work like DHCP servers to dispense (and manage) unique IP addresses to vehicles within the range
(scope) of that leader chain. Since relative speeds among vehicles are limited if compared to absolute ones, having
leader vehicles managing IP addresses within the vehicle grid would ensure a longer longevity to those IP addresses
with respect to utilizing traditional DHCP servers on fixed APs placed along the roadside. Moreover, our scheme
would avoid that routing, TCP and thus ad-hoc networking services may fail if an area is not covered by at least one
AP. We have already proven that this scheme is effective in a highway scenario [FPSG06a], [FPSG06b], [FPSG07];
we need now to adapted it to operate even in an urban context.
Main tasks of the proposed approach that need to be addressed in an efficient way are:

The construction and maintenance of the leader chain. Due to different mobility patterns among vehicles,
leaders may join/leave the chain or get too close/far to each other to appropriately cover all the vehicles
within the scope. Therefore, fast reconfiguration of the leader chain (and of the regular vehicles relying on
it) has to be provided.

The configuration of nodes’ addresses. This represents the core task of the scheme and is composed of a
module for assigning/managing addresses and another one for performing the DAD procedure. Focusing on
the former, the address space is partitioned in sets of addresses and each leader in a scope manages a
different set. The synchronization of address information among leaders is performed by exploiting hello
packets and addresses within each set are assigned to vehicles through a modified DHCP protocol. Instead,
the DAD procedure is in charge of verifying whether an address among those in use within the considered
scope has ceased to be unique due to vehicles’ mobility and restore the uniqueness of all addresses. As
vehicles in a scope are proactively organized to be all covered by the leader chain, the DAD procedure is
performed requiring only single-hop communications (between regular vehicles and leader ones).
The scheme will be evaluated to understand its effectiveness in a vehicular grid scenario in order to support all the
possible applications that will be run in such a context. To this aim various metrics will be considered, eg, the
configuration time of each node, the introduced control overhead, the longevity of an address assignment. The
investigation could be run either via simulations (QualNet, NS2), or real testbed experiments (see Section
“TESTBEDS”), or both. Achieved performances will be assessed and compared by considering different
configurations of the scenario (eg, vehicle density, speeds, scope width).
3.3.4. Traffic & capacity management tools (.5)
Mario will work on this
Traffic and capacity measurement are fundamental for computer network management. In C2C scenarios, new
challenges are posed by the management of mobile users and shared wireless communication channels. First, in C2C
networks, the capacity of a path from Internet server to mobile can vary dynamically and rapidly due to changes in
wireless hop count, interference and mobility; so, timely path capacity tracking is the key to efficient routing, traffic
management and multimedia stream rate and format adaptation. We have developed a packet-pair based technique
called AdHoc Probe that estimates end-to-end path capacity on a mixed Internet and ad hoc path [Chen:05]. It
converges fast, thus proving adequate for mobile, rapidly changing scenarios such as vehicular grids. We propose to
evaluate AdHoc Probe to support representative vehicular network applications (eg, seamless handoff from one
media to another).
Residual Capacity or equivalently, the load on a path is also of great interest. The challenge stems from the
fluctuation of the load on a path. Residual capacity is less stable and much more difficult to estimate than path
capacity. Existing methods such as pathload [Jain:03] rely on increasing a probing rate until a link is saturated. They
requires relatively long time to converge. Besides, they only work for the Internet, while, in vehicle networks the
wireless ad hoc portion of a path is more likely to become the bottleneck for residual capacity. This calls for
research in “fast” residual capacity estimation in multi-hop wireless paths. Related to path characteristics estimation
is motion and location prediction. Even a coarse mobility prediction could help estimate future load patterns and
capacity changes and apply such knowledge to anticipatory routing and congestion control actions.
The relationship of buffer size at the forwarding nodes to the bandwidth delay product of the path, has a significant
impact on TCP performance such as delay and packet loss, and particularly impact how different TCP and other
protocols share a path. Buffer size estimation is especially needed for C2C networks, since there can be multiple
bottlenecks on both Internet portion and on C2C portion of a path. Buffer size estimation also enables a more
accurate estimation of congestion, which was put to good use in TCP Westwood BBE [Shimonishi:05]
Path persistence is an important cross traffic characteristic. The cross traffic is called path persistent if it shares
much of the same end-to-end path with a flow of interest. When the cross traffic exist only on a small portion of the
path, it is called path non-persistent. Path persistence affects the accuracy of residual capacity estimation tools (e.g.,
Spruce [Strauss:03]) as well as fairness among TCP flows. We propose to investigate cross traffic path persistence
behavior and its efficient estimation in the hybrid wire/wireless context. Responsiveness refers to the ability of a
flow to adjust its rate based adapting to network condition. TCP traffic is responsive in that it will reduce its rate in
the presence of congestion, while UDP traffic is non-responsive. Knowing traffic responsiveness in vehicular
networks will assist when downloading continuous media from a server. The path can be chosen based on residual
capacity and cross traffic responsiveness.
3.4 TESTBEDS – testing the applications and the Internet services (3 pages)
Marco, can you please add ORBIT and Rutgers vehicle testbed contribution to this
research?
We plan to study the interaction of vehicular applications with the Internet through the Campus Vehicular Testbed at
UCLA (C-VeT) and the GRIDO overlay implementation [DNPP05][CVET]. The C-VeT testbed has been designed
to study the behavior of network protocols and applications for various urban scenarios and mobility patterns. In
particular, C-VeT exploits the mobility of the UCLA facility management vehicles and the regional mobility of the
UCLA VAN commuter fleet to build a networked facility that can be shared by other users and can provide realistic
motion benchmarks.
Each C-VeT node consists of a vehicle equipped with a compact size industrial PC, 2 IEEE 802.11n interfaces, a
GPS, and a ham radio interface (to be used as control channel). In the future we will also introduce more advanced
radios as they are made available from other programs such as the MIMO radios designed in the DARPA MNM
program at UCLA [REF] and the cognitive radios produced by the current NSF FIND program at Kansas University
[REF]. At steady state, C-VeT will include 30 facility management cars and 30 regional VANs thus providing 60
mobile nodes. The facility management cars run mainly in campus. Their mobility is driven by the daily
maintenance schedule and by the on-demand department and campus logistic requests. The UCLA regional VANRIDE provides a door-to-door shared ride for UCLA students and employees covering the whole greater Los
Angeles area. The Van mobility is driven by the needs of its users and can change every day according to the user
requests. The C-VeT vehicular testbed has been designed to be shared through the Internet in a “Planetlab” fashion.
Users will be able to book testbed resources in advance or share them through virtualization. Each node, indeed, is
equipped with the XEN virtual machine technology developed at University of Cambridge, UK thus offering the
users an insulated virtual sandbox for their experiments [XEN]. A specifically designed web interface will allow
researchers to interact with the whole or part of the network. We will also develop and expose a set of API suitable
to interconnect the C-VeT testbed to other wireless testbeds such the Orbit testbed developed at Rutgers University
or, in the future, to the GENI infrastructure [ORBIT]. In its initial phase the C-VeT vehicular testbed will be
interconnected to the campus wide UCLA Wireless LAN infrastructure thus allowing the vehicles to access the
Internet directly or through an optimized overlay such as the GRIDO testbed developed at UCLA [CDKL04].
The C-VeT Snbapshot of the Control Center showing
an area of the campus experiments. The links represent
the OLSR routing table.
The UCLA Van fleet
In addition to enabling protocol prototyping and performance evaluation in a realistic enviroment the C-VeT fleets
will allow the collection of a large amount of data about the vehicular traffic in the Los Angeles area thus enabling
the creation of realistic mobility models that can be compared with those generated by microscopic traffic simulators
such CorSim or TransitSim.
The C-VeT testbed is connected to a control center. The control center reports statistics on each vehicle such
position, routing information, network load information etc. Additionally it manages and provides the access to the
testbed and to the wide area connectivity through GRIDO or the Internet.
The UCLA facility management carts.
Node Equipment: an industrial PC, a GPS unit, and
a MIMO IEEE802.11n card by Linksys.
The GRIDO testbed has been designed to provide the backbone overlay for the WHYNET project. It is suited to
serve as the Vehicle Overlay to support the Vehicle Grid. It can be used to store the DHT based Geo Location
Server. GRIDO tools can also be leveraged to provide a bandwidth-latency optimized overlay for data streams of
varying kinds: multimedia, file transfer, content replication etc. GRIDO features a WS-Agreement based negotiation
interface complying with the current Global Grid Forum (GGF) standards. In GRIDO we use a virtual-coordinatesassisted overlay construction and maintenance protocol to construct and maintain an optimal backbone structure
[CDKL04].
The GRIDO/C-VET compound will enable realistic in field studies of a new generation of mobile applications and
protocols including scalable location services and wireless content distribution. For example, a provider of wireless
connectivity to various freeways in the US wants to set up a certain number of popular feeds to some freeway
segments in Florida, in New Jersey and in California, respectively. GRIDO automatically geo-locates the segment
addresses and sets up the content delivery points near those locations. In concert with car-to-car optimized datadelivery schemes like CarTorrent [NDPS05] and AdTorrent [NDZP05], GRIDO distributes pervasive content and
applications close to where it will be used, reducing the load on servers and increasing the response time as
perceived by the users.
GRIDO overlay on Planetlab
Grido and CarTorrent at work
We plan to study the interaction of vehicular applications with the Internet through C-VeT and GRIDO [DNPP05].
GRIDO has been developed on top of the “Click Modular Router Project” thus allowing fast implementation,
flexibility and reconfigurability [KMCJ00]. One plan currently coordinated via WHYNET is to use the GRIDO
infrastructure to interconnect vehicular testbed islands that are emerging on the WHYNET project and beyond (see
the schematic overlay in the figure above).
We already have collaboration plans with the ORBIT testbed at the Rutgers University and with international
facilities in Nijgata Japan and Leipzig, Germany. This vision will lead to a unique geographically distributed
vehicular testbed that will include a wide variety of vehicle grid technologies, architectures, and mobility models. It
will be and ideal observatory for heterogeneous vehicle technology interconnection.
[ORBIT]
http://www.orbit-lab.org/
[CVET]
http://www.C-VeT.org/
[XEN]
http://www.cl.cam.ac.uk/research/srg/netos/xen/
4 Plan of Work (.5)
More work needed after the research section is finalized (Mario)
Year 1: extend target applications (Car Torrent, Ad Torrent, etc) with Network Coding; begin development of the
Campus testbed C-VET; extend current simulator and emulator testbeds (Qualnet, PeerKit ); develop realistic
mobility models; begin GRIDO overlay implementation; protocol/applications testing via simulation; verification
schemes for content distribution, performance evaluation through simulation.
Year 2: develop, simulate and test epidemic dissemination protocols (both flat and hierarchical); test robust
georouting and robust TCP protocols in simulation. Implementation of network coding security scheme in testbed.
Year 3: Implementation of GRIDO overlay and of OLS and VLS geo-servers in the testbed; demonstrate
transparent geo-addressing in the infrastructure; demostrate simple C2C applications (Car Torrent; messaging) with
real vehicles on the UCLA campus; carry out vehicle grid interconnection experiments with WHYNET partners and
with our international collaborators in Japan and Germany.
5
Broader Impact and Educational Activities (.5)
More work needed (Mario)
Integration into Educational Activities: All of the member institutions offer regular graduate courses on Advanced
Networks and Mobile and Wireless Networking. The artifacts produced by this research will be integrated into class
projects, and encourage further research into vehicular communication and security issues. Simulations and test-bed
experiments will offer hands-on experience in protocol engineering and network systems. This project will foster the
collaboration and student exchange between international research institutions in Germany and Japan.
Support for under-represented groups and states: The University of Alabama (UoA) is an EPSCoR state with
75% of the undergraduate students coming from the state of Alabama. Among them, 13% are African-American, 1%
Hispanic-American, 1% Asian-American and 53% women students. The project will provide opportunities for both
senior undergraduate and graduate students to participate in research activities including simulation and testbed
experiments during summers. Separate NSF REU grants are in our plan for additional support for exchange students
in the summers. Through this opportunity, we will be able to encourage students from Alabama to engage in science
and technology.
Broader Impact: We anticipate the proposed work to advance the state of the art in several research areas,
including vehicular networking, peer-to-peer networks, and wireless security. The application infrastructure
developed can encourage rapid prototyping of novel and innovative applications. Our strong ties to industrial
partners can lead to adoption and distillation of these infrastructure designs into real software products. There will
be also significant society impacts. Car manufacturers will exploit our findings to develop safer cars and more
productive mobile-offices, with enormous impact on social welfare. Transport Authorities will be able to manage
vehicle traffic more efficiently with reduced transfer delays and again substantial benefits to society. Police
Departments and Civilian Defense Agencies will have at their disposal new extremely powerful forensic
investigation, prediction and terrorist attack prevention tools
The intellectual merits of the project are: the identification, implementation and evaluation of critical Internet
services required by the emerging vehicular environment, and; the definition of guidelines for the design of new
applications that can smoothly interface with the Internet. The study will characterize the vehicle performance
requirements and will generate benchmarks for evaluating and comparing new Internet services. Original
contributions will be made in the areas of Network Coding, Geo-routing, robust TCP and Epidemic
Dissemination, both in terms of performance models and implementations. Within the C-VET testbed, the synergy
of vehicle grid with the Internet infrastructure will be enabled by a robust overlay and redundant Geo Location
Servers.
6
Budget (Giovanni)
7
Current and pending support (Giovanni)
8
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