how Nokia optimizes massive MIMO deployment in both rural and urban settings balancing spectral efficiency & coverage

Thank you for the query. Massive MIMO systems leverage spatial multiplexing techniques to serve multiple users on the same time-frequency resource. Urban environments usually have a higher concentration of users, leading to a more significant demand for network capacity. Massive MIMO systems can serve many users simultaneously by utilizing a large number of antennas, thereby improving spectral efficiency and capacity in dense urban environments.

In rural areas, where cell sizes are typically larger and coverage requirements are broader and hence lower order MIMO techniques such as 2x2, 4x2,4x4, etc. may be more suitable. However, Massive MIMO can still provide benefits in rural areas, such as improved coverage and capacity in hotspot areas.

I hope this clarifies.

I wish you the best.

Thanks Dharmendra for your good answer.
If more technical details and study are of interest especially considering what is and should come next with for instance 6G, Nokia Bell Labs has had a good white paper (already from 2021) on the topic: https://www.bell-labs.com/institute/white-papers/extreme-massive-mimo-for-macro-cell-capacity-boost-in-5g-advanced-and-6g/
The chapter on Coverage starting from page 8, would be of relevance.