The Move to 4x2 MIMO in Wireless Networks

Wireless data demands continue to grow as consumers drive usage levels ever higher. Given constraints on operating and capital budgets, every effort is being made to utilize existing assets more efficiently. Mohamed Hamdy recently wrote about one of the options that network operators have – using multibeam antennas to add more sectors at macro sites. His white paper “Multibeam antennas planning—limitations and solutions” explores some of the technical challenges and solutions to multibeam antenna deployments.

Multibeam antennas make it possible to reconfigure a 3-sector site to have 4 to 6 sectors, thus increasing the capacity of the site. These “higher orders of sectorization” are often used in specific, high traffic areas, and in some cases, even more than 6-sectors can be deployed, if needed.

Another technique that wireless operators utilize for adding capacity is MIMO (multiple input/multiple output). MIMO systems are already commonplace for LTE networks with 2x2 MIMO being table stakes now. (2x2 MIMO is essentially two streams of data for transmit and receive pathways; 4x4 MIMO is four streams).

Many operators are in the midst of evolving to the next level of sophistication in antenna configuration, planning the move from 2-way receive to 4-way receive. With 4-way receive, the connection from the mobile unit to the base station is improved, which gives a primary benefit that the user can experience better call quality when they are far from the site. This is especially important for technologies like Voice over LTE (VoLTE).

4X2 MIMO will further improve the traffic carrying capability of the RF path and increase the capacity of the link from the base station to the mobile. The 4-way receive configurations will also ease the transition to 4X2 downlink MIMO because the same number of antenna ports are needed for 4-way receive as are needed for 4X2 MIMO. Going to 4X2 MIMO often also requires additional equipment to share paths and keep the number of antennas on the tower to a minimum number.

These methods of improving the capacity of a wireless network improve spectral efficiency without adding more sites. They are one tool in the toolkit of the radio engineer working to efficiently add more data handling capability.

What challenges are you dealing with as you transition your network to 4X2 MIMO? Leave me a comment if you want to discuss.

Article was originally published on April 18, 2016