Cognitive Radio PHY/MAC for wireless sensor
networks
Lead: Luo Ling
Due to the rapidly increasing demands of wireless bandwidth, available spectral resources become
scarce. Moreover, current fixed spectral allocation suffers from underutilization as in the case of TV bands. These are the motivations of
Cognitive Radio (CR) network, which is defined as a radio that makes secondary users actively search for the idle channels NOT used by the
primary users by scanning the whole spectrum. Our current research mainly focuses on channel modeling, search algorithm analysis and
channel detection in CR network. Currently we are investigating the following:
- The channel availability models for secondary users (conventional random i.i.d model, non-identical but identical distribution model, and
correlated Markov model);
- The development and characterization of effective search algorithms for idle channels with trade-offs among mean search time, power consumption and achievable Pd-Pfa performance;
- The reliable and energy-efficient detection method characterized by the receiver operation properties like Pd
and Pfa;
The adaptive strategy of scanning for spectral opportunities in a dynamic scenario, where the usage pattern of primary users change is also
included in potential directions to extend our work. The modelling of channel state information using correlated Markov model is expected to be utilized to design such a strategy.
Adaptive Mesh Networks
Lead: Rohit Gupta, Hui Ma
802.11 wireless LANs for broadband wireless access
constitute a growing success story. Their deployment in
single-cell (i.e. single AP) scenarios (homes, small
business and hotspots) is well-supported by current .11
technology. However scaling such networks to the enterprise
environment to serve a large number of simultaneous users
with voice and data services while providing coverage
remains a challenge. A promising architectural solution
consists of a two-tier multi-cellular, multi-hop approach to
WLAN network design whereby an AP mesh provides the
infrastructure for communication between mobile clients.
Implicit in this is a direct wireless inter-connection
between mesh nodes which all route traffic (only some of
which are APs with associated clients, and a very small
fraction act as gateways to the wired Internet).
Our research seeks to advance the
state-of-art of such .11 based multi-hop mesh networks by
undertaking an integrated cross-layer approach to
innovations at Layers 1-3 (joint PHY/MAC/Network).
Optimizing of such networks will require on-line
tuning of key protocol parameters at various layers (hence
leading to an Adaptive Mesh). Currently we are investigating
- The impact of Physical
Carrier Sensing (determined by carrier sensing
and/or receiver sensitivity threshold) on MAC
performance as a function of network topology
- The impact of
Multi-radio/node Mesh nodes on network performance,
particularly the new degrees of freedom that it offers
for joint channel assignment and link-aware routing
as components of an optimized .11 AP
mesh. Our approach combines protocol/algorithmic innovation
supported by OPNET simulations and experimental results from
a
StarEast based MESH network in a laboratory setting.
For more information check
http://commnet.ee.washington.edu/funlab/
Underwater Acoustic Networking
Lead: Nathan Parrish, Leonard Tracy
Underwater acoustics has been a topic of research for decades. However, the
idea of deploying networked teams of underwater vehicles for both deep and
shallow water ocean exploration is a more recent topic of interest. The
Seaglider, developed at the University of Washington, is one such vehicle.
FUNLab along with the Applied Physics Lab (APL) are exploring physical and
MAC layer protocols to provide robust, low power, efficient networking
solutions to the Seaglider.
The underwater acoustic channel has properties that make it a very difficult
medium for communications. For instance, the long propagation delay of
sound, multi-path spread of the medium, frequency selective attenuation,
shadowing zones, and other factors make this channel extremely hard to
characterize. A commonly used approach for determining the acoustic
propagation of sound in the underwater channel is to use ray tracing
techniques based on Snell's Law. Members of the FUNLab are investigating
ways to statistically characterize the underwater channel using techniques
similar.
MAC protocols in the underwater environment must be designed with different
considerations than those in the terrestrial environment. The long
propagation delays of sound make carrier sensing and acknowledgment packets
impractical. Additionally, autonomous underwater vehicles (AUVs) are
extremely energy-constrained. These and other design considerations,
including the lack of position information from GPS, necessitates new MAC
design for AUV deployment, which is also an ongoing topic of research
between the FUNLab and the APL.
For more information see the UAN Projects page
ns-3: Next
Generation Open Source Network Simulator
Principal Investigators:
Tom Henderson (Boeing), Sumit Roy (UW),
George Riley (Georgia Tech) and Sally Floyd (ICSI, UC Berkeley)
Contributor: Ilango Purushothaman(UW)
ns-2 is a discrete-event network simulator
that is being used extensively in network research circles. It has been
funded by a number of previous research projects, but none directly as an
infrastructure project since 2000. A clear need exists for additional
focused development work to occur on ns. The ns-3 project seeks to do just
that and is the next major revision of the ns-2 simulator.
ns-3 is
a managed software development program to comprehensively re-design, enhance
and maintain the popular ns-2, to address research and educational
challenges for next generation of data networks. This four-year project will
i)
refactor the simulator's architecture
ii) develop new networking protocol models for wireless
iii) provide new opportunities for software encapsulation, and
iv) integrate the tool with virtual network testbeds.
For details on this project, check
http://www.nsnam.org/.
To download the latest 802.11 infrastructure mode patch for ns-2,
Click here.. The changes made to the ns-2 module are described in
this report.