Why is pilot contamination considered as a more evident problem in the case of massive mimo although it can appear as intercell interference problem between any ordinary interfering base stations of mobile network not employing massive mimo tech ?
Pilot contamination occurs when two terminals use the same pilot sequence (also known as reference signal). It can be suppressed by using different pilots in adjacent cells - for example, by having a large number of pilots sequences and switching randomly between them. Conventional systems can afford to have many more pilot sequences than active terminals, which makes the risk of pilot "collision" rather small. In contrast, massive MIMO cannot afford that since it is supposed to have 20-40 times more active terminals on the same time/frequency resource than conventional systems. Simply speaking, if you have 30x more terminals the pilot contamination will be 30x more severe.
You can read more about pilot allocation and how to avoid it in my new paper:
Massive MIMO for Maximal Spectral Efficiency: How Many Users and Pilots Should Be Allocated? (http://arxiv.org/abs/1412.7102)
hi dear all. massive mimo is based on channel estimation (too much) to accurate beamforming due to accurate received pilots I think.regards
Adding to the colleagues,
The massive MIMO system needs to estimate all existing channels between the transmitter and the receivers. The number of these channels is much larger than in case of conventional MIMO. The pilots are used to estimate the channels and they must be orthogonal and their set numbers are limited. So because of this one has to reuse the pilots more in massive MIMO systems which causes more interference between the pilots as their reuse distance is smaller in case of MIMO.
Pilot reuse schemes must be devised to reduce this interpilot interference which is called pilot contamination.
Best wishes
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