To address the challenges of 5G wireless communication, the Internet of Things (IoT), new applications such as car-to-car communication, researchers from KU Leuven have created a network of software defined radios. These SDR’s can simultaneously transmit data and detect the presence of harmful interference using a technique called in-band full duplex.
Currently, wireless devices listen first to check if the spectrum is free and then transmit their data. This works well in normal situations where there are few devices. However, in dense networks there is a high probability that two or more devices may decide simultaneously that the spectrum is free and transmit over one another other, essentially corrupting each other’s data.
Figure 1. If two devices decide to transmit at the same moment, the receiver gets a superposition of the two signals, causing a collision and corrupting the packet.
Using a FPGA USRP RIO in conjunction with the LabVIEW Communications System Design Suite, the team at KU Leuven created a solution that relies on in-band full duplex. By continuously sensing for neighboring transmitters and aborting the transmission if one is detected, corruption-causing collisions can be eliminated.
Simulations show the result to be an ultra-efficient network which can double the throughput by using a wireless listen-and-transmit scheme.
Figure 2. The in-band full-duplex prototype uses a USRP RIO with Xilinx Kintex 7 FPGA connected to an electrical balance duplexer to enable simultaneous transmit and sense.
Figure 3: The networked prototype setup at KU Leuven uses six USRP RIO devices with in-band full-duplex capabilities connected to a grid of 20 USRP RIO devices in a half-duplex configuration.
Current experiments already show the benefit of sensing while transmitting. However, the team wants to scale these experiments up to a network that comprises more than 40 SDRs that can all run the novel technology for dense network testing. The potential for future work is huge.