Francois Quitin

One of the important tasks of national regulators is to detect abusive usage of the radio-frequency (RF) spectrum. This talk presents the implementation of an opportunistic spectrum scanner on a software-defined radio platform, whose aim is to continuously scan the RF spectrum and to detect whether any signals are present. The implementation is done on a USRP-N210 software-defined radio, a popular and cheap model. One major bottleneck of USRP-based implementations is the limited CPU computation power, which does not allow to process RF signals at high sample rates continuously. In the proposed implementation, most computation is done on the USRP FPGA, such that the host CPU is relieved and is only used to store data and coordinate the scanning. We present the details of the FPGA and the software architecture, as well as some experimental results that show the efficiency of the proposed spectrum scanner.

This talk will present a new method to estimate the bearing of a radio transmitter with a mobile, single-antenna receiver, and its implementation on a software-defined radio (SDR) testbed. The bearing estimation method relies on the following principle: by considering the signal received at several points along its trajectory, the receiver implicitly creates a virtual multi-antenna array (similarly to synthetic aperture radar systems) that can be used to estimate the bearing of the radio transmitter. Virtual multi-antenna arrays have two major differences with conventional multi-antenna arrays: 1) the position and orientation of each antenna in the virtual array depends on the movement of the receiver and must be estimated; and 2) the local oscillator (LO) offset between transmitter and receiver adds a phase offset to the signal received by each “virtual” antenna, which must be estimated and compensated for. The first problem is solved by using an inertial measurement unit (IMU), which can provide the relative position and orientation of the receiver for short time periods. The second problem is solved by expanding the signal model that is used in bearing estimation algorithms (such as MUSIC) to account for LO offset. The proposed system is implemented on a USRP-N210 SDR with an external high-end IMU and tested in an anechoic chamber. The SDR implementation is a mixture of FPGA and software development, while some parts of the data are processed off-line. The results show that our method is indeed feasible, with bearing estimation errors of only a few degrees. We then present the first efforts of an implementation on a USRP-E310 SDR which has an integrated, lower-quality IMU.

The state of SDR, and free/open SDR in particular, is interesting. In some cases, SDR research and progress has been declared dead, implying that there is nothing left to research or develop. Practical usage of SDR tells a different story, though, and users of SDR products run into all sorts of issues every day.

In this panel, we would like to discuss with the audience what the top issues are that SDR frameworks need to solve in the near future -- be they technical, legal, political or anything else.

What are the top 3 items that the realm of Software Defined Radio needs to figure out? In this panel, we invite some experts as well as the entire audience to discuss this question. We shall discuss technical challenges (if there are any) as well as legal and political challenges. Does free/open software radio have any different questions to tackle? If we were to attend a technical conference in the near future, what would be the most mind-blowing thing we could present? Will there be more, competing frameworks going forward, or will they consolidate? These and many more questions shall be the topic of this year's SDR panel.

Other people: Martin Braun Tom Rondeau Bastian Bloessl Ben Hilburn