What is REVOsdr?
REVOsdr is a multicarrier (Orthogonal Frequency-Division Multiplexing, OFDM) Software-Defined-Radio (SDR) wireless technology comprising two dedicated transceivers (modems) at both ends of the data link. It enables fast and reliable Point-to-Point (PTP) data link communication over long distances.
REVOsdr is sold as Firmware Licensing, as an Original Equipment Manufacturer (OEM) PCB, or as ready-to-use standalone Encapsulated Equipment, to support communications under high mobility, subject to low delay/latency and high-bandwidth requirements. It is particularly suitable for applications that require real-time data acquisition/transmission. REVOsdr is ready for integration and operation across multiple frequency bands in a single radio, i.e., with wider and flexible spectrum management.
REVOsdr does not need to rely on deployed infrastructure as in cellular communications, and its design avoids latency and coverage limitations of Wi-Fi implementations.
REVOsdr is a portable SDR solution that is implemented using a baseband programmable FPGA board. It is ready to integrate with other hardware or software stages, e.g. transmitter or receiver RF front-ends, 1×1 or 2×2 simple or adaptive smart antennas, 1×1 or 2×2 MIMO, real-time video processing, adding scalable and flexible possibilities to the REVOsdr family. The standard REVOsdr hardware/software implementations are sold as OEM PCB, but can also be sold as standalone encapsulated equipment.
REVOsdr’s performance was assessed in terms of the Bit Error Rate (BER), which indicates the number of bits negatively affected by noise, interference, distortion or bit synchronization errors. The receiver decoded the received signal, from which the BER values were calculated in the figure below. The Signal-to-Noise-Ratio (SNR) shift between adjacent modulations follows the expected 6dB gap, and the corresponding constellations are depicted for each tested modulation.
OFDM is a multicarrier technology implemented in multiple wireless communication standards. OFDM can deal multipath frequency-selective channels, which means that the distortion of the received signal is mitigated. The parametrization of OFDM or other physical phenomena (e.g. Doppler shift due to mobility) can modify the distance between adjacent sub-carriers. As such a distance get smaller, the mismatches between transmit and receive frequencies result in energy leakage or interference between adjacent sub-carriers and performance degradation occurs. To compensate such a degradation, REVOsdr’s architecture implements joint timing and frequency offset estimation processing, which corrects the Carrier Frequency Offset (CFO).
The performance of REVOsdr can be evaluated in terms of the Error Vector Magnitude (EVM). Such a metric quantifies how noise, distortion, spurious signals and CFO cause deviation of the received constellation points regarding the ideal positions. The figure below shows the EVM of the demodulated and equalized signal as a function of the CFO, which quantifies how REVOsdr handles sub-carriers displacements due to the Doppler shift induced by mobility. The received QPSK constellations and the zoom-in of its upper left point in the following two configurations: first, a bandwidth of 40.96MHz with half the sub-carrier separation of 20kHz; and second a bandwidth of 81.92MHz with half the sub-carrier separation of 40kHz. As the CFO increases the constellation degrades, and yet the receiver can estimate the received data up a CFO value close to half of the sub-carrier separation for both configurations.