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Channel hardening in massive Multiple-Input Multiple-Output (MIMO) systems is a hot research field that needs investigation. As the number of antennas increases, channel starts to behave deterministically and small-scale fading decreases. This is called hardening phenomenon. Since there is a lack of real world study of the hardening effect in massive MIMO channels, this paper aims at investigating channel hardening in an outdoor real-world scenario by using a linear double polarized transmitting antenna array and a cylindrical dual polarized receiving array. Measurements are performed in two different routes and hardening is analyzed in terms of different polarization combinations and different antenna subsets by fixing the transmitter or receiver and using coefficient of variation (CV ² ) as a metric. The results show that in terms of getting more pronounced hardening, it is more beneficial to fix the position of the …