Abstract
Massive MIMO technique offers significant performance gains for the future of wireless communications via improving the spectral efficiency, energy efficiency and the channel quality with simple linear processing such as maximum-ratio transmission (MRT) or zero-forcing (ZF) by providing each user a large degree of freedom. In this paper, the system performance gains are studied in a multi-cell downlink massive MIMO system under the main considerations such as perfect channel estimation, imperfect channel estimation and the effect of interference among cells due to pilot sequences contamination. Then, mathematical expressions are derived for these gains i.e., spatial multiplexing gain, array gain and spatial diversity gain. After that, essential tradeoffs among these gains are considered under the effect of non-orthogonal interference, these tradeoffs are: spatial diversity gain vs. spatial multiplexing gain and array gain vs. spatial multiplexing gain. Simulation results show that the unbounded number of base station antennas boosts the array gain through concentrating the energy to spatial directions where users are sited, hence diminishing loss in array gain due to pilot contamination. The simulation results reveal also that massive MIMO strengthens the spatial multiplexing gain through increasing the number of served users via the same system resources in spite the effect of inter-cell interference. Finally, the spatial diversity gain is measured in term of outage probability and the simulation results show that raising the number of antennas will improve the outage probability. Meanwhile increasing the number of served users will lead to degrade the outage probability per user due to non-orthogonal interference from other cells.
Highlights
Communication in wireless channels is affected by multipath fading which causes a random fluctuation in the received signal power
The spatial diversity gain is measured in term of outage probability and the simulation results show that raising the number of antennas will improve the outage probability
The work of our paper considers the downlink massive system and the system performance gains are discussed and their mathematical expressions are derived for multi-cell massive MIMO system under the effect of non-orthogonal pilot sequences on them, we study the main important tradeoffs among these gains under the effects of pilot contamination
Summary
Communication in wireless channels is affected by multipath fading which causes a random fluctuation in the received signal power. This random fluctuation in signal level is known as fading, which affects the quality and reliability of wireless communication. The leverages of MIMO are achieved through utilizing the spatial dimensions (submitted by the multiple antennas at the transmitter and the receiver) [1], where it was first investigated in point to point MIMO or single user MIMO which is called (SU-MIMO). The conventional MIMO system needs more effort to exploit the spatial multiplexing gains due to signal levels are exposed to the attenuation at cell edges as compared to interference levels there. A substitute for a point-to-point MIMO system is a multiuser MIMO system (MU-MIMO) in which an antenna array simultaneously serves multiple
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
