Jukka Talvitie, Toni Levanen, Mike Koivisto, Tero Ihalainen, Kari Pajukoski, and Mikko Valkama
Beamforming is one of the key technologies for achieving the high performance criteria in various modern and future wireless communications systems, in particular at the millimeter wave frequencies. In order to avoid or reduce the large signaling overhead and corresponding latency related to beam-training procedures, location-based beamforming utilizing available position information has been proposed. In this paper, by using the available position probability density function (PDF) of a receiving device, we derive and analyze the capacity of a beamformed radio link, without and with beam-sweeping based beam training. Through the analysis, we show that by adjusting the beamforming and/or beam-training parameters appropriately, the radio link capacity can be optimized with respect to the prevailing positioning accuracy, and thus optimal utilization of radio resources is achieved with minimal radio access latency.
IEEE Transactions on Vehicular Technology
Videos and Demonstrations
Obtaining position PDFs using an EKF-based approach at 3.5 GHz carrier frequency
In this realistic positioning example, a user equipment (UE) is moving along a pre-defined trajectory on top of the METIS Madrid grid with a varying speed of 15-45km/h. The UE, deployed with a single omnidirectional dipole antenna, transmits uplink (UL) sounding reference signals (SRS) every 100 ms using 50 MHz bandwidth at 3.5 GHz carrier frequency. These signals are then received at several access nodes (ANs) which are equipped with uniform rectangular arrays with beamforming capabilities. In particular, the ANs are adjusting their received beamformers such that they are pointing towards a priori UE position estimate obtained from the exploited extended Kalman filter (EKF). At each time-instant, the EKF fuses ToA estimates (obtained using a simple maximum likelihood estimation) from five closest line-of-sight (LoS)-ANs, and the acquired position PDF is then utilized in capacity evaluations at a higher mmWave carrier frequency.