Pilot Resource Allocation To Improve Data Rate Of Multicell Massive Mimo System

Abstract

Massive MIMO is being touted as one of the most promising technologies for 5G and beyond cellular networks, with tremendous data rates and capacity. Pilot contamination (PC), however, limits the systems performance that highly reduce data rate. It is formed when the user of home cell and neighboring cell are not orthogonal to each other. To overcome this problem and improve the data rate of multi-cells massive MIMO system, we proposed a new schemes namely modified Soft Pilot Reuse (mSPR). First, the users in a targeted cell are clustered to the center and edge zone based on the signal level they received. On clustered users, an mSPR is applied that allocates the same set of pilot resource to all center zone users that having low PC severity and assign a different set of orthogonal pilots to the user having the highest PC severity. Additionally, it reuses this set of pilots within a grouped cell in a system, also assures that none of the pilot group that is assigned to edge user of the center cell is reused in a single tire. Consequently, pilot overhead and inter cell interference are reduced. For center zone users, a random pilot assignment is applied which assigns pilots from the same group. To do this, first maximum user out of the cell is selected in order to allocate the pilot resource. Then, the users’ pilot in the same cell is orthogonal and this center user is reused in another cell. The simulation results shows the data rate improvement of multi cell multi user massive MIMO system with the proposed modified Soft Pilot Reuse (mSPR) pilot resource allocations. Further, number of orthogonal pilots are reduced and improves the uplink achievable rate and spectral efficiency over pre-existing schemes.