![]() Our ground station radio system implements an FSK transmitter and two parallel BPSK receivers, operating at different data rates to support the two main operational modes of the satellite we are developing at Skybox. The combination of the USRP and GNU Radio proved to be an excellent solution to our problem, allowing us to experiment with many configurations before ultimately settling on our final design. Moreover, because of our constantly evolving design specifications and need for rapid prototyping and testing, a suitable commercial hardware solution did not exist. Satellite modems typically cost anywhere from a few thousands to tens of thousands of dollars. The motivation for this was twofold: cost and flexibility. During our initial design phase, one of the major decisions made with regards to our Communications system was to use a software-defined-radio architecture for our ground stations' Telemetry, Tracking and Control (TT&C) radios. ![]() Skybox Imaging is a satellite imaging startup located in Mountain View, California. Finally we discuss opportunities for collaboration between the open-source development and academic research communities to make this goal a reality. We also discuss directions for future work – our ultimate goal is to develop an open-source library of synchronization primitives to enable the implementation of MIMO techniques in a distributed fashion using the virtual array concept in WiFi, Zigbee and other real-world wireless networks. We report some initial results which demonstrate the increase in the received signal strength (RSS) at the receiver due to beamforming. The relatively large frequency offsets, significant phase noise and drifts in the LOs on the USRPs and large gnuradio/kernel latencies make this synchronization problem particularly challenging. ![]() In our experiment setup, the receiver periodically broadcasts short feedback packets to all the cooperating transmitters which use a combination of an extended Kalman Filter and a simple 1-bit beamforming algorithm to achieve the RF signal synchronization in a completely distributed fashion. Beamforming, however, requires very precise synchronization of the transmitted radio frequency (RF) signals of the cooperating transmitters. In this talk, we discuss the key ideas behind our recent all-wireless open-source implementation of distributed beamforming on GNU-radio/USRP-based SDR platform.ĭistributed beamforming is a cooperative transmission scheme whereby a number of transmitters in a wireless ad-hoc network organize themselves into a virtual antenna array and focus their transmission in the direction of the intended receiver, potentially achieving orders of magnitude improvements in energy efficiency. GNU-radio/USRP-based software-defined radio testbed for distributed beamforming ![]()
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