Link quality analysis in the presence of blockages for analog beamformed mm-wave channel

Future systems of the 5
^th
generation are slated to use the mm-wave bands due to the large slices of bandwidth available at those frequencies. Relative to the contemporary microwave bands, to compensate for the harsh propagation conditions, highly directional communication using beamforming methods is necessary to achieve a level of reliable communication, however minimal. Due to the fragile nature of directional communication (especially in dense urban environments or high mobility environments), there is a need to understand the effect of blockages on the system performance. Blockages on links (post beamforming) necessitate time and power expensive mechanisms such as beam adaptation or even re-training the beam setup. In systems aiming for less than 1ms latency, this can be impracticable. While the channel modeling effort for mm-wave bands is underway, the nature of environmental blockages for outdoor cellular communications is still not well understood. In this paper, to study the impact of blockages, in addition to the real-world challenges of mm-wave communications, we propose a hierarchical blockage model where, an arbitrary path (LOS or NLOS) undergoes a blockage with probability p (model parameter) independent of the other paths. Our results show that, even in the event of an unblocked LOS, there is a notable degradation in the received SNR. We also show that the increase in the path loss due to a severe level of environmental blockages is about 15dB relative to environments with a low level of blockages, for a distance of 150m which is approximately the envisioned cell radius for 5G cellular systems. Thus implying that, the range of reliable communication shrinks in the presence of environmental blockages.