Abstract

The fifth-generation (5G), now being developed for use in the millimeter-wave (mm-wave) frequency bands, would enhance the Quality of Service (QoS) for the Mobile User (MU) in the near future. Despite the advantages of using mm-wave communications that are attained through the large bandwidth available in this band, it suffers from high penetration loss and low diffraction, which causes very high signal attenuation in free space. The signal's attenuation can also be due to the blockages, such as buildings, human presence, vehicles, etc. As a result, the signal propagation path could be interrupted by those blockages causing significant fluctuation in the handover (HO) probability. Thus, the foreseen mm-wave communication gains are achieved at the expense of varying HO probability. Therefore, the impact of blockages on the HO probability for a user with mobility is a crucial performance factor that needs to be analyzed and addressed in mm-wave cellular communication systems. This thesis analyzes the impact of different types of blockages on the HO probability for a MU with mobility in the 5G mm-wave cellular network, and it shows how blockages affect the resource allocation in mm-wave cellular system.

Firstly, we obtained the effect of a single static blockage with a fixed location in the 2-D plane on the HO probability for a MU moving radially away from the mm-wave base station (BS) at a certain speed. The mm-wave BSs, are assumed to be distributed according to a homogeneous Poisson Point Process (PPP). We considered the MU is moving at a uniform angle with a certain speed in the mm-wave cellular network. The results show that the blockage has a remarkable impact on the HO probability, depending significantly on its location and length, and MU direction and speed.

Secondly, we analyzed the impact of multiple static blockages, with a certain density, distributed according to PPP. The results show in this scenario that the density of the blockages plays a significant role in the HO probability for a user with mobility in a 5G mm-wave cellular system.

Thirdly, we presented an analysis of the impact of self-blockage on HO probability in 5G mm-wave cellular networks. As expected, the results showed that self-blockage has a notable effect on the HO probability. The results show that the HO probability where self-blockage is incorporated in the system is different from the HO probability in case no blockages are incorporated in the system model.

Fourthly, we analyzed the impact of dynamic blockages on the system's performance in the mm-wave cellular network. The blocking probability of the link between the mm-wave BS and the MU due to dynamic blockages is calculated. We consider blockages and mm-wave BSs are distributed according to PPP, while the MU is assumed to make a displacement from the origin to another position. The arrival process of the blockages crossing the link between the tagged mm-wave BS and the MU is assumed to be Poisson with a certain density. The blockage duration is assumed to be independent of the blockage arrival process with exponential distribution. The results showed that the blocking probability gets higher when the blockages are moving at a high speed, and the density of the blockages gets higher as well.

Fifthly, we apply a classical HO scheme in mm-wave cellular networks to show how blockages affect resource allocation. We apply an adjustment of the number of reserved channels reserved exclusively for the HO requests based on a predefined threshold of the probability of blocking HO calls, to ensure the requirement of the QoS and hence the resource allocation is managed efficiently.
The results show that a higher number of reserved channels is required to satisfy the minimum threshold of the blocking probability of HO calls. As a result, an optimized and balanced scheme between the blocking probability of HO calls and the blocking probability of originating calls in the mm-wave BS is required.

We conclude our research by providing the future plans of our research and the conclusion.