In the introduction of our paper "Massive MIMO has Unlimited Capacity" (https://arxiv.org/pdf/1705.00538) you can find a description of different approaches to mitigate pilot contamination.

Pilot contamination is indeed an issue in massive MIMO, but I am not sure if I would call it a major issue.

By increasing the order of massive MIMO system :-).

As the number of antennas increases, signals energy (including the pilot signal) focused more and more and interference goes to its lowest.

In the introduction of our paper "Massive MIMO has Unlimited Capacity" (https://arxiv.org/pdf/1705.00538) you can find a description of different approaches to mitigate pilot contamination.

Pilot contamination is indeed an issue in massive MIMO, but I am not sure if I would call it a major issue.

Yasser F. Al-Eryani and Emil Björnson

thanks for the reply ... really helpful