Alexander W Layton

Implementation and Analysis of Energy Detection-Based Sensing Using USRP/SBX Platform

The performance of a spectrum sensing algorithm is dependent on many factors such as total detection time, radio noise floor, and carrier frequency. In order to maximize detection capability, the radio platform for which the spectrum sensor is implemented must be sufficiently configurable. An appropriate platform to address such a problem is the Universal Software Radio Peripheral (USRP) with a SBX daughterboard as it is software configurable and capable of wideband reception over a large range of carrier frequencies. Motivation for characterizing the sensing limits of the USRP/SBX radio was the DARPA Spectrum Challenge (DSC) cooperative event. The DSC cooperative event simulated the scenario where multiple users must share the same channel and each user is not supplied with prior information of strategies employed by the other users. Solutions to this problem typically include spectrum sensing. This paper provides the data necessary to design energy detection based spectrum sensing for the USRP/SBX radio. The sensing capability of the USRP/SBX radio is determined via analysis of the receiver noise floor with respect to carrier frequency, sample rate, and detection time. Performance of the energy detection function is stated in closed form and provided with respect to parameters of the detector.

Wireless Load Weight Monitoring Via a Mobile Device Based on Air Suspension Pressure

A system was designed and tested to measure pressure in the airbag suspension components of an over-the-road tractor trailer and use those signals to wirelessly display load weight. Three subcomponents (a HID -- human interface device and two DPUs -- digital processing units) were required and communicated using Zigbee wireless devices. Except for a region directly in front of the cab, the unit transmitted weights up to 45 m. Effect of number of calibration points on system accuracy was evaluated.

Low SINR Synchronization for the DARPA Spectrum Challenge Scenario

The DARPA Spectrum Challenge (DSC) established a problem space that created a need for radio synchronization algorithms functional in environments with low signal-to-interference-plus-noise ratio (SINR). For the final DSC competitive event, forward link receiver SINR was commonly less than 0 dB and feedback link receiver SINR could be less than 5 dB, both in a 5 MHz channel. For the preliminary DSC competitive event, both forward and feedback link receiver SINR could be much less than 0 dB. Additional constraints led to the implementation of synchronization algorithms in accordance with the GNU Radio framework. As a result, the algorithms are written in software that executes on general-purpose Intel processors and requires minimal computational complexity. Additionally, the synchronization should not limit system error rate performance to ensure that the capability of implemented receiver signal processing is fully realized (e.g. Error control coding). A possible solution for the DSC competitive event includes time division duplexing (TDD) for channel access with a high data rate forward link and robust feedback link for automatic repeat request (ARQ). In support of this approach, multiple synchronization techniques were implemented. In this work, we present one of our implementations, a non-data aided symbol synchronization method that can be employed for both links. This paper includes a description of the synchronization algorithm along with its simulated and implemented performance for scenarios applicable to the DSC.