WaveCombe project: Characterization and modelling of radio propagation channels at mmW bands
Millimeter wave (mmWave) communication is a key technology for the fifth generation (5G) wireless communications and can be used for fronthaul, backhaul, and fixed link building to building transmission to provide high data transmission rate in indoor and outdoor environments. The electromagnetic wave above 10 GHz suffers more from rain attenuation, which causes the performance reduction and even outage of the communication system at mmWave bands for 5G fixed links. Therefore, rain attenuation effect on mmWave bands becomes an important issue and should not be neglected. The rain attenuation depends on the rain rate, rain drop size distribution (DSD), and complex water refractive index. Several works have been done to study the effect of precipitation on mmWave fixed links, and most of terrestrial link measurements are dedicated for long range and line of sight (LOS) links. The study needs a long term measurement over several years for accurate and useful results which should be qualified for a reliable radio link during precipitation events along the year. At Durham University, to study the rain attenuation on mmWave bands for 5G fixed link, a custom-designed continuous wave (CW) channel sounder is utilized to record channel data at K band (25.84 GHz) and E band (77.52 GHz) for direct and side fixed links with dual polarizations and a high performance PWS100 disdrometer is applied to collect weather data, including rain rate and rain DSD as shown in Fig.1 (a). The setup uses a transmitter (Tx) box shown in Fig.1 (b), a receiver (Rx) box for direct link (c), and receiver box for side link (d). The distance between the Tx and Rx is about 35 m for the direct link. The measurement setup conducts rain attenuation measurements and modeling for short-range building to building transmission scenario. Furthermore, the channel sounder has been updated based on the previous system ,  in order to reduce the system attenuation loss, simplify the system, make it more stable than before, and also study the rain attenuation for both direct and side links simultaneously. Preliminary measurements after the update illustrate the impact of rain on the received signal strength shown in Fig.2. However, the side link has a larger variation due to multipath fading. The rain attenuations for direct and side fixed links are thoroughly compared for the two bands. The ITU-R P.838-3 model and DSD model are applied to rain attenuation modelling.