Channel modelling for 5G radio networks
Future 5G networks are expected to provide high data rates by using high frequencies in the bands up to 100 GHz. To this end, the world radiocommunications conference in 2015 identified several bands in the range 24-86 GHz for possible allocation for future radio networks. This has prompted research across the world to study the radio propagation characteristics in these bands for line of sight and non-line sight for both fixed links and mobile links. In the Centre for Communications Systems we have carried out innovative research into the radio channel characteristics for small cells in suburban environments and residential areas for line of sight and non-line of sight for below the rooftop and above the rooftop.
On body networks at mm waves
The availability of broad blocks of spectrum in the 60 GHz band provides the opportunity to support very high data rate systems. This includes in-flight entertainment content delivery to the seat-back in high capacity passenger aircraft. In addition, the 60 GHz band is attractive for on-body networks since antennas can be physically small and the excess absorption assists covert operation of equipment for military applications.
To enable on-body measurements, a state of the art channel sounder with multiple band capability was designed and developed under EPSRC funding. The new sounder provides an unambiguous Doppler measurement across a specified band. With the addition of signal conditioning and data acquisition the sounder has been used in a number of field trials for wireless sensor networks, and for on body measurements in the 60 GHz band.
Relay links combat the effects of path loss in wireless links. To study relay links two radio channel measurement systems were developed to set up a base station, relay link and mobile user and used in various environments such as inside buildings, indoor to outdoor and outdoor to outdoor. Figures 1 and 2 show an experimental set up on the Science site. In Figure 1 the base station is set up inside the School of Engineering and Computing Sciences and the relay is outside the building relaying the signal to the mobile station which was moved around the Science site. In Figure 2 the Base station and the Relay station are both outside the buildings and the mobile is moved around the site.
Wall reflections compromise the through-wall detection of possible targets in active radar systems. Wall reflections can appear far stronger than the echoes from actual targets which are overshadowed and difficult to detect, especially in case of walls with air gaps or hollow structures, which tend to trap the electromagnetic waves.
A wall removal technique has been investigated and successfully validated at the Centre. This uses suitable complementary patterns to switch on and off the transmitter and the receiver, providing listening intervals which attenuate or completely remove the undesired wall reflections from the received signal. A novel patch-like antenna for TTWI applications in the frequency range 0.5-2 GHz has also been developed, in collaboration with the Fraunhofer Institute für Zuverlässigkeit und Mikrointegration (IZM) in Berlin.