Mobile
Ad Hoc Networks (MANETs)
Index of Contents
Background
on MANET
DARPA Project
ATP Project
NCS Project
Background on MANET
In the next generation of wireless
communication systems, there will be a need for the rapid deployment of
independent mobile users. Significant examples include establishing survivable,
efficient, dynamic communication for emergency/rescue operations, disaster
relief efforts, and military networks. Such network scenarios cannot rely
on centralized and organized connectivity, and can be termed as wireless
mobile ad hoc networks (MANETs). A MANET is an autonomous collection of
mobile users that communicate over relatively bandwidth constrained wireless
links. Since the nodes are mobile, the network topology may change
rapidly and unpredictably over time. The network is decentralized, where
all network activity including discovering the topology and delivering
messages must be executed by the nodes themselves, i.e., routing functionality
will be incorporated into mobile nodes.
The set of applications for
MANETs is diverse, ranging from small, static networks that are constrained
by power sources, to large-scale, mobile, highly dynamic networks.
The design of network protocols for these networks is a complex issue.
Regardless of the application, MANETs need efficient distributed algorithms
to determine network organization, link scheduling, and routing. However,
determining viable routing paths and delivering messages in a decentralized
environment where network topology fluctuates is not a well-defined problem.
While the shortest path (based on a given cost function) from a source
to a destination in a static network is usually the optimal route, this
idea is not easily extended to MANETs. Factors such as variable wireless
link quality, propagation path loss, fading, multiuser interference, power
expended, and topological changes, become relevant issues.
Research in the area of ad
hoc networking is receiving much attention from academia, industry, and
government. Since these networks pose many complex issues, there are many
open problems for research and significant contributions.
We are currently involved
with three MANET projects:
We work closely with other organizations - DARPA,
SAIC,
CECOM,
MITRE,
SRI,
and SAINC - on this project.
Since NIST is a neutral government agency, we have been tasked to provide
an unbiased technical evaluation of (1) MANET technologies being developed
in DARPA's Global
Mobile Information Systems (GloMo) program, and (2) MANET protocols
proposed in the Internet
Engineering Task Force (IETF) MANET Working Group in the military
SEAMLSS
environment. [SEAMLSS is
a simulation and emulation environment developed in DARPA's GloMo program.
It provides the capability to test, demonstrate, and evaluate the scalability
of GloMo communications technology for realistic military usage scenarios.
DARPA's goal is to introduce SEAMLSS to the military community as a tool
for modeling and simulating military network.]
This project has two main components - verification/validation of SEAMLSS
and evaluation of protocols in the SEAMLSS environment.
I. PROJECT TASKS and MILESTONES
A. Verification/Validation
of SEAMLSS
-
Conduct DARPA/NIST workshop on model validation - In May 1999, NIST together
with DARPA conducted the DARPA/NIST
Network Simulation Validation Workshop on simulation model validation
for large scale networks. Researchers from the community were brought
together for a three day workshop to present results on model validation
and discuss further ideas in break-out sessions.
-
Devise detailed verification plan (set of verification tests) for SEAMLSS
- The SEAMLSS simulation environment is being developed by SAIC.
NIST is providing a solid verification plan to determine if the implementation
of SEAMLSS accurately represents specification. [POWERPOINT
Presentation on SEAMLSS Verification Plan]
-
Execute verification plan to verify/validate SEAMLSS simulation environment
- NIST is working closely with SAIC on the verification process of
SEAMLSS. NIST is providing continuous and timely feedback to SAIC
on test results and analysis of verification procedure.
B. Evaluation of Protocols
-
Identify metrics to be used in evaluation - NIST is working with service
representatives (DARPA,
SAIC,
CECOM,
MITRE,
SRI,
and SAINC) to identify metrics
needed for evaluating MANET protocols.
-
Devise Standard Evaluations - NIST is collaborating with service representatives
(DARPA, SAIC,
CECOM,
MITRE,
SRI,
and SAINC) to devise a set of
Standard Evaluations to be used in assessing the GloMo and MANET protocols.
An example of a Standard Evaluation is "Network Join" - which consists
of a series of test cases to determine how long it takes for a node or
a group of nodes to fully integrate into an existing network.
-
Comprehensive evaluation of protocols - Together with SAIC and CECOM,
NIST is developing a testbed using SEAMLSS and the Standard Evaluations.
The next phase is to conduct a thorough evaluation of the GloMo protocols
and MANET protocols proposed in the IETF using the testbed.
-
Report results to IETF and DARPA - NIST will make recommendations to IETF
MANET Working Group and DARPA based on the results of the evaluations.
NIST is also working with the IETF MANET Working Group to introduce the
Standard Evaluations as a means of evaluating other MANET protocols.
II. PROJECT GOALS and FINAL "PRODUCTS"
-
Provide unbiased feedback to ensure reliability of
SEAMLSS
-
Build confidence in the SEAMLSS environment within
the DARPA GloMo community
-
Substantiate SEAMLSS for use beyond DARPA GloMo community,
e.g., possibly other military agencies including Army
-
Provide set of Standard Evaluations and metrics for assessing decentralized
MANET technologies
-
Provide unbiased evaluation of GloMo/candidate MANET technologies based
on simulation in SEAMLSS
-
Recommendations to DARPA based on results of protocol evaluation study
-
Recommendations to IETF for adoption of MANET standards
In a MANET, power may be supplied to static nodes through a generator,
while mobile nodes operate off a battery supply. Clearly, a vital
issue for MANETs then is to conserve power while still delivering messages
reliably since the life of the network is determined by the power sources.
In this project, we focus on the issue of power conservation in routing
for decentralized MANETs.
I. PROJECT TASKS and MILESTONES
-
Investigate importance of power expended on routing in MANETs - The focus
of this task is to look at the benefits of power consciousness in making
routing decisions at the network layer.
-
Develop an efficient, dynamic, power conscious routing concept for MANETs
- The benefits of power conservation/control for MANETs prompt the important
question: What is the most power efficient way to route a packet from a
source to a destination such that the packet is received with an acceptable
packet success rate?
-
Design a simulation test environment - This task involves constructing
models for network structure, wireless link quality, multiuser interference,
and radio communication environment, and building a simulation model using
OPNET. We have incorporated the IEEE
802.11 MAC layer protocol in our simulation environment. We have
run various simulations looking at the performance of the power conscious
routing concepts.
-
Extend power conscious principles to other distributed routing algorithms
- Since MANETs have various applications and network configurations, it
is unlikely that one routing algorithm will obtain the best performance
in all situations. Hence, it is important to be able to apply the
power conscious concepts to other distributed MANET algorithms. [POWERPOINT
Presentation on ATP Project]
II. PROJECT GOALS and FINAL "PRODUCTS"
-
Power conscious concepts at the network layer to enhance the performance
of distributed MANET routing protocols
-
Publication - M.W. Subbarao, "Dynamic Power-Conscious Routing for
MANETs: An Initial Approach," Proceedings of IEEE VTC Fall 1999, Amsterdam,
The Netherlands, Sept. 1999. [POSTSCRIPT
VERSION] [PDF VERSION]
-
Publication - J.S. Pegon and M.W. Subbarao, "Simulation Framework
for a Mobile Ad Hoc Network," Proceedings of OPNETWORK 1999, Washington
DC., Sept. 1999. [MS WORD VERSION]
National
Communication Systems (NCS): Mobile Ad Hoc Data Networks for Emergency
Preparedness Telecommunications
This project focuses on investigating specific emergency preparedness requirements
for emergency/rescue and disaster relief MANETs for survivable and efficient
execution. Examples of emergency networks include the disaster relief
efforts after the bombing of the Oklahoma City Federal Building or the
aftermath of a hurricane where cellular/PCS service may not be available.
The project has three main components which focus on (1) power conservation,
(2) efficient and appropriate use of the bandwidth limited channel in an
emergency situation, and (3) reliable and robust communication.
I. PROJECT TASKS and MILESTONES
A. Dynamic Power Conservation
-
Dynamic transmitter power adjustment - The focus
here is on devising dynamic power conscious concepts to be used in making
routing decisions at the network layer. Possible approaches include
adjusting the transmitter power according to the channel characteristics
and routing messages on the path requiring the least amount of power expended.
The aim is to improve system performance and extend network life.
-
Survey of wireless radios - We will provide a survey
of wireless radios and their respective power adjustment capabilities.
This will aid in determining which wireless radios are better suited for
power adjustment in emergency preparedness telecommunications.
B.
Emergency Channel Access and Priority Messaging
-
MAC layer protocols - This portion focuses on investigating
different existing MAC layer protocols for MANETs, e.g., FAMA,
CAMP,
etc., and evaluating their ability to provide multiplexing for different
priority classes (adapted use in an emergency situation):
-
Admission control - if a transmission request
should be accepted into the network given the class of priority, delay
requirements, and available resources of the systems, e.g., bandwidth and
buffer space.
-
Scheduling - appropriate traffic offered to the channel
from the different priority classes.
-
Recommendations - We will recommend which MAC layer
protocol for MANETs is best suited for emergency communication. If
necessary, we will propose modifications to existing protocols or propose
new techniques.
C. Robust Emergency Communication
-
Clustering for large networks - Due to complexities involved in maintaining
routing tables for large networks, it is typically more efficient to divide
the network into a set of smaller subnetworks, i.e., clustering.
We will evaluate existing clustering algorithms (e.g., CBRP)
and techniques for flat emergency networks, i.e., networks without predetermined
hierarchical structure with respect to the following:
-
Scalability - determine if the protocol performs efficiently as the number
of nodes in the network increases.
-
Nodal mobility - determine the sensitivity of the protocol to changes in
node locations.
-
Reliable and robust message delivery - assess how the protocol handles
messages destined for a node that has since departed the network.
-
Inter-group communication - It is important to ensure communication between
several deployed emergency groups. Thus, we will identify and investigate
protocols for heterogeneous inter-group communication with respect to scalability,
nodal mobility, and reliable and robust message delivery as defined above.
This will include investigating inter-operability issues between heterogeneous
groups.
-
Recommendations - We will recommend which clustering protocols and inter-group
algorithms are best suited for emergency preparedness telecommunication.
If necessary, we will propose modifications to existing protocols or propose
new techniques.
II. PROJECT GOALS and FINAL "PRODUCTS"
-
Power conscious concepts at the network layer to enhance the performance
of emergency preparedness MANET routing protocols
-
Survey of wireless radios for power adjustment capabilities
-
Thorough investigation of MAC layer protocols for emergency preparedness
MANETs and recommendations by NIST
-
Thorough investigation of clustering and inter-group communication algorithms
and recommendations by NIST
-
Publication - Interim project report on dynamic power conservation
submitted to NCS [POSTSCRIPT VERSION]
[PDF VERSION]
-
Publication - Interim project report on emergency channel access
and priority messaging in preparation
-
Publication - Interim project report on robust emergency communication
Last updated on February 16, 2000.