Title page for ETD etd-09132010-082640

Type of Document Master's Thesis
Author Radhakrishnan, Aravind
Author's Email Address ara254@vt.edu
URN etd-09132010-082640
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Bostian, Charles W. Committee Chair
Pratt, Timothy J. Committee Member
Yang, Yaling Committee Member
  • DSA
  • Cooperative Spectrum Sensing
  • DSA Broker
Date of Defense 2010-09-02
Availability unrestricted
Public Safety Cognitive Radio (PSCR) is a Software Defined Radio(SDR) developed

by the Center for Wireless Telecommunications (CWT) at Virginia Tech. PSCR can

configure itself to interoperate with any public safety waveform it finds during the

scan procedure. It also offers users the capability to scan/classify both analog and

digital waveforms.

The current PSCR architecture can only run on a general purpose processor and

hence is not deployable to the public safety personnel. In the first part of this thesis

an Android based control application for the PSCR on a Beagle Board(BB) and the

GUI for the control application are developed. The Beagle Board is a low-cost, fan-

less single board computer that unleashes laptop-like performance and expandability.

The Android based Nexus One connected to the Beagle Board via USB is used to

control the Beagle Board and enable operations like scan, classify, talk, gateway etc.

In addition to the features that exist in the current PSCR a new feature that enables

interoperation with P25 (CPFSK modulation) protocol based radios is added. In this

effort of porting the PSCR to Beagle Board my contributions are the following (i)

communication protocol between the Beagle Board and the Nexus One (ii) PSCR

control application on the Android based Nexus One (iii) detection/classification of

P25 protocol based radios.

In the second part of this thesis, a prototype testbed of a Dynamic Spectrum Access

(DSA) broker that uses the Beagle Board PSCR based sensor/classifier is developed.

DSA in simple terms is a concept that lets the user without license (secondary user)

to a particular frequency access that frequency, when the licensed user (primary

user) is not using it. In the proposed testbed we have two Beagle Board based sen-

sor/classifiers that cooperatively scan the spectrum and report the results to the

central DSA broker. The DSA broker then identifies the frequency spectrum with-

out primary users and informs the secondary users about the free spectrum. The

secondary users can then communicate among each other using the frequency band

allocated by the DSA broker. When the primary user enters the spectrum occupied

by the secondary user, the DSA broker instructs the secondary user to use a different

spectrum. Based on the experiments conducted on the testbed setup in the CWT

lab environment, the average time taken by the DSA broker to detect the presence of

primary user is 0.636 secs and the average time taken for the secondary user to leave the frequency band that interferes with the primary user is 0.653 secs.

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