huawei vivaT-Mobile Netherlands and True Thailand choose 8 antennas for FDD spectrum, joining Kuwait in choosing Huawei gear. 8 antennas will rarely deliver twice the throughput of four antennas but will often deliver a 50% increase in capacity. 32/64 antenna Massive MIMO has been chosen by BT, DT, & FT but that is in higher frequencies running TDD.

32 antennas for 700 MHz spectrum would be too large to be practical most places. 256 antennas at mmWave frequencies are the size of a large chip and can go almost anywhere. 64 antennas at mid-frequencies like 2500 MHz need 1.5 to 3 meters, practical on most towers. Antenna size goes up with lower frequencies, making 32 antennas at 700 MHz a challenge and often impractical at 1800 MHz. 

In addition, most frequencies below 2000 MHz all dedicated to FDD transmission, with upstream and downstream in separate bands. This produces problems with upstream signaling for Massive that lets the base know the state of the mobile and other receivers. 

The base needs to know the ever-changing.status of each receiver to perform the MM magic.A truck or even a person passing between the base and receiver can result in a call drop with MM. As Apple discovered in an iPhone model, even a change in how you hold the receiver than cause a problem. 

Professor Erik Larsson believes the FDD problems are unsolvable but all three MM vendors offer an FDD system. One solution is to use a codebook to send upstream just a pointer, reducing congestion. I have several papers with other ingenious approaches. Until we get results from units in the field with numerous connections, we won't have clear answers.

"Don't go beyond 8 antennas for FDD for now," a very senior engineer believes.

dave askFeb 2018 Verizon $20B 5G build is on for adding customers in 2018. Gigabit LTE, 5G Massive MIMO became real in 2017. China, Japan, Korea, and Verizon U.S. 5G are firm, with heavy investment expected 2019-2021. The goal: Closer to the truth. 

Being a reporter is a great job for a geek. I'm not an engineer but I've learned from some of the best, including the primary inventors of DSL, cable modems, MIMO, Massive MIMO, and now 5G mmWave. Since 1999, I've done my best to get closer to the truth about broadband.

Send questions and news to Dave Burstein, Editor. I always want to hear from you, especially if I make a mistake.