Massive MIMO will come into its own in 5G deployments, but some operators plan to use it to bolster their 4G macro networks too. One of those is Sprint, which said it could boost sector capacity in its 2.5 GHz LTE network to 6Gbps using 64×64 MIMO antenna arrays combined with other technologies such as 256QAM modulation. Shortly before his resignation was announced last month, Sprint’s first ever COO, Günther Ottendorfer, told the Next-Gen Wireless Networks Summit: “We are investing a lot of work into massive MIMO.” Currently Sprint reaches gigabit LTE speeds, he said, by using about 60 MHz of spectrum with 2×2 MIMO and 64QAM across three sectors. Using 120 MHz of 2.5 GHz spectrum together with 64×64…