SRG Live Test Shows FDD Massive MIMO and MU‑MIMO Deliver Strong 5G Uplink Gains on Verizon

Signals Research Group ran live‑network tests on Verizon 5G cells in St. Paul, Minnesota. The radio equipment in the tested cells was supplied by Ericsson. The trial focused on FDD (Frequency Division Duplex) Massive MIMO combined with Multi‑User MIMO (MU‑MIMO) in commercial FDD spectrum. Tests compared an earlier 4T4R configuration with a 32T32R Massive MIMO deployment and measured the additional effect of MU‑MIMO.

Uplink performance stood out. After moving to 32T32R Massive MIMO and enabling MU‑MIMO, SRG reported a substantial uplink throughput lift, calling it "simply outstanding." Uplink MU‑MIMO occurred nearly all the time during tests and regularly delivered close to four uplink MIMO layers. That happened even when the two phones were placed only 18 inches apart, a result SRG highlighted because conventional wisdom says close device spacing makes MU‑MIMO harder in FDD.

Downlink behavior was less uniform. SRG found that Massive MIMO already delivered strong downlink performance with single‑user MIMO (SU‑MIMO). In some routes, enabling downlink MU‑MIMO produced solid double‑digit efficiency gains. In other routes, device pairing for MU‑MIMO was unstable and provided limited benefit beyond what Massive MIMO already achieved. SRG described downlink MU‑MIMO as "hit or miss" relative to SU‑MIMO performance in some areas.

FDD spectrum is widely used by operators worldwide. If MU‑MIMO can boost uplink throughput reliably in FDD, operators can increase capacity for uplink‑heavy applications such as VoIP, mobile video sharing, cloud‑based collaboration, and enterprise mobile connectivity without immediately needing new spectrum. Improvements in uplink efficiency could reduce pressure on spectrum expansion and delay costly spectrum acquisitions.

The tests were conducted on unloaded cells with only two devices, so they don't show how FDD MU‑MIMO behaves under real network load with many moving users and varied traffic mixes. SRG's results suggest potential, but operators and planners will need further trials in denser, loaded conditions to assess scalability, pairing stability, and multiuser scheduling under realistic traffic.

For network planners and VoIP/UC vendors, the trial is a practical signal to monitor. Uplink gains in FDD could materially improve real‑time voice and video user experience, but broader deployment decisions should follow larger, multiuser field validations.