Mobile Ad hoc Networking (MANET) J. Haerri
Internet-Draft C. Bonnet
Intended status: Experimental F. Filali
Expires: August 29, 2007 Institut Eurecom, France
February 25, 2007
MANET Position and Mobility Signaling: Problem Statement
draft-haerri-manet-position-problem-statement-00
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Abstract
This document contains a problem statement and justification for
position and mobility signaling in MANET protocols.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Vehicular Ad Hoc Networks . . . . . . . . . . . . . . . . 6
3.2. Wireless Sensor Networks . . . . . . . . . . . . . . . . . 6
3.3. Mobile Wireless Networks . . . . . . . . . . . . . . . . . 7
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Geographical Routing Protocols . . . . . . . . . . . . . . 9
5.2. Routes and Links Instability . . . . . . . . . . . . . . . 9
6. Approach Rationals . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Geographical Routing Protocols . . . . . . . . . . . . . . 11
6.2. Routes and Links Instability . . . . . . . . . . . . . . . 11
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 16
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1. Introduction
In recent months, a growing interest has been observed in position
information for improving routing in mobile ad hoc networks, by
trying to improve links stability, periodic maintenance, power
consumption or even security.
Indeed, by peeking into the recent litterature, we see that between
2004 and 2006, 3 IEEE transactions and 38 IEEE conference proceedings
are related to mobility predictions, while ACM published 11 papers.
The common point of all these new directions is the requirement of
mobile nodes' mobility information. Some proposals need nodes
velocity, others moving directions, or nodes position. The most
complex ones require nodes position and velocity in order to extract
mobility prediction patterns.
The Intelligent Vehicule Community already understood the benefits
safety provisionings could obtain from proactive visions as they
started standardizing the information cars should share. For
example, the VII consortium (Vehicle Infrastructure Integration) is
standardizing the information that should be transmitted between
vehicles. As routing protocols and eventually internet will come on
top of intervehicular communications, a similar and possible
collaborative approach should be undergone within the IETF.
However, we do not know yet what kind of information are required to
be transmitted, and it is quite clear that the community might not
even all agree on a common framework.
The aim of this document is to describe new orientations in network
research that includes localization information and for what purpose
such information is necessary. This document also discusses possible
improvements on regular standardized MANET protocol with the help of
mobility information, and point out possible application beyond the
scope of MANETs.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in [RFC2119].
Additionally, this document introduces the following terminology
GPS - Global Positioning System. A geolocalization system
developped and operated by the US Department of Defense that is
able to provide accurate worldwide coordinates of devices equiped
with GPS receivers. A similar European system is currently under
developpement under the name of Galileo. The GPS system does not
work without a clear access to at least 3 satellites, thus is
inoperable for indoor positioning.
GPS-free Positioning - A set of techniques that has been developped
in order to provide a mean of localization in situation when a
clear access to satellites is not possible. Most of the methods
use multilateration techniques and require either a formal
training, or an anchor node that knows its accurate position.
Time - The universal GPS time expressed in seconds.
Longitude - The longitude describes the location of a place on Earth
east or west of a north-south line called the Prime Meridian
located in Greenwich, UK. Longitude is given as an angular
measurement ranging from 0 degree at the Prime Meridian to +180
degree eastward and -180 degree westward.
Latitude - The latitude gives the location of a place on Earth north
or south of the equator. Latitude is an angular measurement
ranging from 0 degree at the Equator to 90 degree at the poles.
Elevation - The elevation is the altitude of an object from a known
level or datum. Common datums are mean sea level and the surface
of the WGS-84 geoid, used by GPS.
Azimuth - Azimuth is the horizontal component of a direction,
measured around the horizon, from the north toward the east in the
northern hemisphere, and from the south toward the west in the
southern hemisphere.
Mobility - mobility information related to a specific address, which
MAY consist of a longitude, latitude and elevation, a velocity, an
azimuth, or the time this mobility information has been sampled.
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Stability - a measure of the similarity between a node's sampled
(past) mobility parameters and the actual ones.
VANET - Vehicular Ad Hoc Networks. A particular set of MANET where
cars and road infrastructures are equiped with wireless devices.
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3. Use Cases
3.1. Vehicular Ad Hoc Networks
A vehicular ad hoc network (VANET) is a specific case of mobile ad
hoc networks, where vehicules and road infrastructures are equiped
with wireless devices. Accordingly, the vehicles are able to
communicate with each other as well as interacting with the road
infrastructure. One straightforward application of VANETs is safety,
where communications are exchanged in order to improve the driver's
responsiveness and safety in case of road incidents.
A Vehicular ad hoc network is set up between cars and between cars
and road infrastructures. Due to the increased mobility, basic MANET
routing protocols are inefficient. Novel approaches have been
suggested such as state-less geographical routing, where packets are
routed without any specific route setup in the direction of the
maximum progress toward the destination node. This class of routing
protocols require the knowedge of, at least, the destination and the
forwarding node positions. Most of them use GPS-provided
coordinates.
In order to obtain a routing decision, nodes MUST exchange position
data by means of level 3 messages between cars, road infrastructures,
and location servers.
3.2. Wireless Sensor Networks
A Wireless Sensor Network (WSN) is an extreme form of a MANET in
terms of the amount of devices and of their highly limited
capabilities. Sensors can be low cost, mass produced devices
operating for years on a pair of AAA batteries. A sensor dust can be
spread over a monitored location, and from that moment on, the
sensors are fixed and operate for the lifetime of their batteries,
which are their most critical resource.
Around a Sensor Network, sinks are deployed in order to collect the
measurements from the sensors and relay the commands from the
controllers. Thus, sensors automatically form a structure to forward
unicast packets from the sensors to the sinks, and to propagate
broadcast packets across the network from the sinks.
In order to establish a routing infrastructure and scale to a large
geographic area, sensors can be deployed to form a tree, a mesh or
any kind of distributed graph that aims at optimizing communication
and energy consumption.
As sensor may only be aware of their own location, in order to
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improve the creation of a routing topology, position information MAY
be exchanged between sensors and sinks. Moreover, as a mean of
improving the detection and localization of a device moving in a
monitored area, sensors MAY also have to exchanged location or
mobility information between each others.
3.3. Mobile Wireless Networks
A Mobile Wireless Network is a network where at least a group of
nodes are mobile. A Mobile Wireless Network includes infrastructure
and ad-hoc networks, VANETs, WSN, or Mesh Networks.
The mobility of routers or clients involved in a Mobile Wireless
Network is a major source of burden in standard routing protocols,
including hand-overs, route errors, and reduced capacity. In order
to improve this issue, mobility MAY be predicted to some extends,
which could then be used to improve ressource management techniques
and Quality of Service.
In order to predict routers and clients' mobility and thus adapt the
network topology, nodes MUST exchange at least velocity information,
but SHOULD also obtain and share some means of positioning
techniques, either GPS or other GPS-free systems.
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4. Requirements
MANET Position and Mobility Signaling has the following requirements
R1: All nodes requirering position information SHOULD be equipped
with GPS devices. That will allow the network to have a
synchronized time as well as position information.
R2: Location signaling MUST be compatible with non-location
signaling format, more specifically, the generalized packet/
message format [PacketBB]
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5. Problem Statement
All protocols standardized, or currently in the process of being
standardized, do not make any assumption on a positioning system,
which could provide a mean of knowing neighboring nodes' coordinates
and mobility. A node ID is the major (sometimes the only) source of
information about other nodes.
Whereas those protocols have been designed to work perfectly well
without this kind of strong assumption, a growing popularity appeared
in the community for location-enhanced protocols.
The MANET Position and Mobility Signaling Format is possibility
related to the following working groups:
o Existing Routing Protocols (MANET, OSPF)
o Network Mobility Support (NEMO)
5.1. Geographical Routing Protocols
Moreover, the Manet working group within the IETF decided to
standardize two well known protocols, AODV and OLSR. AODV is a
reactive protocol, which opens a route on the specific request from a
source node. On the other hand, OLSR is a proactive, also called
table-driven protocol, which computes all possible routes from and to
any reachable destination. In that perspective, the IETF is
providing the community with two sets of protocols for different
applications, possiblity working together in hybrid configurations.
However, in recent years, a new class of routing protocol appeared.
Geographical Routing Protocols, also called Geographical Fowarding
Protocols as no formal routing techniques are considered, choose the
forwarder based on the "best" progress towards a destination node.
The "best" progess is not only the maximum progress, but includes a
set of heuristics that chooses the optimal forwarder based on
positions, directions, local density, or even interference. The
common point in all those techniques is that they guarantee packet
correct delivery and rely on the knowledge of the destination and the
potential forwarder's locations.
5.2. Routes and Links Instability
In the Mobile Ad Hoc Network community, the major source of
instability in the provided protocols comes from nodes mobility.
OLSR uses periodic topology maintenance, and AODV developped local
route breaches repairing techniques. Moreover, any kind of
optimization based on a fixed topology (even related to a large set
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of nodes), needs to be run again after a couple of seconds when nodes
are moving. However, although those techniques may be appropriate
for low mobility networks, they reach their limit when local mobility
is sudden or lacks any correlation with the neighboring nodes. That
is indeed not a surprise if Geographical Forwarding protocols became
popular in Vehicular ad hoc networks, where maintaining even a single
open route (not mentionning a set of routing tables) is often
impossible.
In order to solve this issue, a growing popularity came from mobility
prediction techniques used as means to not only choose the best
"actual" forwarder, but the best actual AND future forwarder that
will reduce the maintenance burden. Similarly to Geographical
Forwarding Protocols, the common points in all mobility predictions
techniques is a node's access to its own location and a method to
spread it to neighoring nodes. Mobility Predictions has been widely
successfully studied in the last three years, from reactive to
proactive approaches even to geographical routing protocols.
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6. Approach Rationals
MANET Position and Mobility Signaling aims at extending Generalized
MANET Packet/Message Format [PacketBB] to define a standardized
packet format to exchange position and mobility information, and to
improve the stability of Manet routing protocols. This section
covers the rationale behind this approach.
6.1. Geographical Routing Protocols
There is a large source of litterature on Geographic Routing
Protocols. The most widely known is the Greedy Perimeter Stateless
Routing [GPSR] protocol. The major source of burden in geographical
forwarding techniques is to avoid falling into local maxima, which is
when a node cannot find any neighbor providing a better progress than
itself to the destination. In that case, one has to define backoff
techniques, which guarantee to leave the local maximum at a cost of
local detours. This is not the purpose of this paper to be
exhaustive on all geographical routing protocols developped so far.
The German project Networks on Wheels (NoW) [NoW] has been studying
and improving this approach on Vehicular Ad Hoc Networks for the last
3 years and could be a good starting point.
6.2. Routes and Links Instability
It has been shown that a simple single order mobility prediction
model was able to deliver superior routing performances than DSR or
AODV [AGAR]. A similar study has been extended to location services
[KUMAR]. The conclusions were quite similar, by noticing that the
diffusion of predicted future locations of nodes in the network could
improve the performances of location services.
On the other side of the routing techniques, different groups
developped mobility prediction techniques in order to improve
proactive protocols. It has been shown that the choice by OLSR of
nodes moving in similar direction could improve its performance
[MOLSR]. Moreover, an appropriate choice of Multipoint Relays based
on actual and the predicted future topology configuration could
significantly improve the MPR protocol, and accordingly, OLSR [KMPR].
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7. IANA considerations
This document does not require any IANA action.
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8. Security considerations
This document is a problem statement and does not create any security
threat. It discusses the concepts of the use of Position and
Mobility information in Mobile Ad Hoc Networks.
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9. References
9.1. Normative References
[PacketBB]
Clausen, T., "Generalized MANET Packet/Message Format", <
www.ietf.org/internet-drafts/
draft-ietf-manet-packetbb-03.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[AGAR] Agarwal, A. and S. Das, "Dead Reckoning in Mobile Ad-Hoc
Networks", IEEE WCNC 2003, the 2003 IEEE Wireless
Communications and Networking Conference, March 2003.
[GPSR] Karp, B., "Greedy Perimeter Stateless Routing (GPSR)",
<http://www.icir.org/bkarp/gpsr/gpsr.html>.
[KMPR] Harri, J., Filali, F., and C. Bonnet, "On the application
of mobility predictions to multipoint relaying in MANETs:
kinetic multipoint relays", AINTEC 2005, Asian Internet
Engineering Conference, December 2005.
[KUMAR] Kumar, V. and S. Das, "Performance of Dead Reckoning-Based
Location Service for Mobile Ad Hoc Networks", IEEE
Wireless Communications and Mobile Computing Journal,
March 2004.
[MOLSR] Menouar, H., Leonardi, M., and F. Filali, "A movement
prediction-based routing protocol for vehicle-to-vehicle
communications", V2VCOM 2005, 1st International Vehicle-
to-Vehicle Communications Workshop, July 2005.
[NoW] "Networks On Wheels (NoW)",
<http://www.network-on-wheels.de/documents.html>.
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Authors' Addresses
Jerome Haerri
Institut Eurecom, France
Phone: +33 4 93 00 8176
Email: haerri@eurecom.fr
Christian Bonnet
Institut Eurecom, France
Phone: +33 4 93 00 8108
Email: bonnet@eurecom.fr
Fethi Filali
Institut Eurecom, France
Phone: +33 4 93 00 8134
Email: filali@eurecom.fr
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