Beyond Listen-Before-Talk: Advanced Cognitive Radio Access Control in Distributed Multiuser Networks
This project designs advanced cognitive radio access and
power control algorithms that can achieve better spectrum efficiency while
limiting interference to primary communications. Moving beyond the more
traditional access strategies that rely only on secondary user (SU) spectral
sensing to avoid collision with primary users (PUs),
this research exploits various levels of primary network’s data link control (DLC) signaling and feedback information. Such DLC information is available in many practical wireless
systems, such as transmission profile, receiver ACK/NACK,
channel quality indicator, and power control information. Utilizing such
information elevates the level of SU cognition. It provides more efficient
spectrum sharing, better PU protection (especially in
the presence of multiple distributed SUs), and
multiple levels of SU and PU interaction. The major
outcomes include:
1) Distributed multi-SU cognitive access and power control
based on PU receiver feedback information;
2) Optimal algorithms for distributed multi-SU access
control in multi-channel cognitive environments;
3) Cognitive radio access robust to PU
behavioral changes and incomplete PU feedback
information; and
4) Hierarchical cognitive radio networks of users with
varying degrees of cognition.
This significantly broadens the future applications of
wireless services in areas with limited open spectrum. The plan recruits
students, especially from under-represented groups, and integrates the results
into the classes for computer science and electrical engineering majors.
[More
information]
Related publications (click here for a complete
list):
Distributed Power Control for Cognitive User Access based
on Primary Link Control Feedback, Senhua Huang, Xin
Liu, and Zhi Ding.
Infocom 2010. [pdf]
Feedback-based access and power
control for distributed multiuser cognitive networks. Fabio E. Lapiccirella, Senhua Huang, Xin Liu, and Zhi
Ding. Information Theory and Applications Workshop, 2009. [pdf]
Non-intrusive Wireless Networks for Opportunistic Spectrum Access
This NeTS project studies non-intrusive means of opportunistic access in spectrum-agile communication networks. A number of research activities in the area of spectrum-agile communications and cognitive radio are motivated by the need for more efficient spectrum utilization, facilitated by regulatory policy movements, and enabled by advances in hardware technologies. The investigators focus on sensing-based secondary networks to achieve non-intrusiveness since such networks require low infrastructure support, are broadly deployable, and can also adapt to changing environments.
The following
fundamental issues are under investigation: 1) capacity-interference tradeoff
between primary and secondary users (with preliminary results); 2) evacuation
protocols for secondary users upon the return of primary user activities (with
preliminary results); and 3) compatibility with CSMA-based primary users (in initial phase). We are also
collaborating with the subaward PI’s
at APL (
The overall research project involves theoretical analysis, system modeling, protocol design, and experimental evaluation. An integrated approach is taken that involves physical layer, MAC layer, and network layer. The investigators exploit tools from estimation and detection, graph theory, and optimization theory for analyzing, modeling, and designing cognitive radio networks via performance evaluation and model validation. The goals are to develop feasibility and capacity analysis of sensing-based approach that can interact with both non-interactive (e.g., TDMA/CDMA-based) and interactive (e.g., CSMA-based) primary systems, and to develop protocol suites that evacuate secondary users according to the interference tolerance of primary users.
A short summary of the project and current progress can be found here [ppt].
CAREER:
Smart-Radio-Technology-Enabled Opportunistic Spectrum Utilization
Preliminary study and general observations have indicated that it is spectrum access, instead of true spectrum scarcity, that limits the potential growth of versatile wireless services. Therefore, in this project, we focus on the opportunistic exploration of the white space by secondary users (who are users other than the primary licensed ones) on a non-interfering or leasing basis. The following issues are being studied.
- What are the impacts and properties of the white space and how can we quantify them?
For instance, one experiment shows 62% of white space in spectrum under 3GHz at a certain location. Is exploiting this white space equivalent to gaining 0.63*3GHz bandwidth? The answer is that it depends and the gain could be even higher. We have proposed a new metric, named equivalent non-opportunistic bandwidth, to quantify the benefit of opportunistic spectrum access. The effects of spectrum availability pattern, network topologies, and other factors are being studied. We are also working on analytical models to capture the spatial and temporal characteristics of white space.
- How should secondary users share the white space dynamically and efficiently?
We have proposed a graph-based model to capture the heterogeneity of spectrum availability at users, and developed preliminary algorithms for spectrum sharing. We plan to further study centralized and distributed opportunistic algorithms with and without information exchange among secondary spectrum users. We also like to consider fairness and power control in the corresponding algorithm designs.
A short summary of the project and current progress can be found here [ppt].