الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 57 |  |  |
| | | from | 57 | | |
Abstract
A multi-antenna base station (BS) can spatially multiplex many terminals over the same bandwidth at the same time, this is a technique known as multi-user, multiple-input multiple-output (MU-MIMO).A new idea in cellular MU-MIMO is the use of a large excess ofBS antennas to serve several single-antenna terminals simultaneously. This so-called ”massive MIMO” promises attractive gains in spectral efficiency with time-division duplex operation.Within a cell, the BS estimates the channel from mutually orthogonal reverselink pilot sequences to estimate the channel to formulate a receiver for the reverse link and a precoder for the forward link depending on channel reciprocity.The channel coherence is typically constrained in time as well as frequency, leading to a trade-off between the resources spent on pilots and those available for data symbols. This pilot overhead can be reduced by reusing pilot sequences in nearby cells, however this potentially introduces inter cell interference between cells during the channel estimation phase, this is so-called ”pilot contamination” effect.Pilot contamination is the bottleneck in Massive MIMO system, as it affects its performance, so through this research we will discuss the effect of pilot contamination on performance of Massive MIMO & some techniques to mitigate this effect