Delay characteristics for directional and omni-directional channel in indoor open office and shopping mall environments at 28 GHz

In order to meet the increasing demand on mobile data service, the fifth generation mobile communication systems (5G) expects to operate in high frequency band up to 100 GHz where the spectrum is available for wide bandwidth. Therefore, the channel characteristics and model for high frequency band up to 100 GHz are of great importance for technology evaluation and network deployment of 5G system. In this paper, wideband channel measurements were conducted in open office and shopping mall scenarios at the center frequency of 28 GHz with 800 MHz bandwidth. Channel impulse responses are obtained for directional and omni-directional channel by using horn antennas and biconical antennas, respectively. Delay characteristics are analyzed based on the measurement data. The measured delay spread is found to obey the log-normal distribution in the two indoor scenarios. The delay spread at 28 GHz in LoS case is smaller compared with that of indoor hotspot scenario in ITU-R M.2135 for below 6 GHz. Furthermore, it is found that the delay parameters are much smaller in directional channel than those in omni-directional channel.