5G Connectivity Explained: Sub-6GHz vs mmWave and Why Your 5G Speeds Vary So Much

Almost every phone sold today advertises 5G connectivity, yet the real-world experience of 5G ranges from barely faster than 4G to genuinely gigabit-class speeds, depending entirely on which flavor of 5G a phone is actually connected to at any given moment. That inconsistency isn’t a flaw in any specific phone; it’s baked into how 5G networks are built.

Two Very Different Kinds of 5G

5G connectivity isn’t one single technology but a family of network types that share a name while behaving very differently. Sub-6GHz 5G, which includes both low-band and mid-band frequencies, forms the backbone of most carriers’ broad 5G coverage. Low-band sub-6GHz travels long distances and penetrates buildings well, but its speed improvement over strong 4G is often modest. Mid-band sub-6GHz offers a meaningfully better balance, delivering speeds well above typical 4G while still covering reasonably wide areas, and it’s what most people experience as “good 5G” in everyday use.

mmWave, short for millimeter wave, is the flashiest version of 5G, capable of extremely high peak speeds that can rival home broadband. The trade-off is severe: mmWave signals travel only short distances and struggle to pass through walls, windows or even heavy rain, which is why mmWave coverage tends to be limited to dense pockets like stadiums, airports and specific city blocks rather than broad geographic coverage.

Why Your 5G Speed Test Results Are All Over the Place

The wide gap between these network types is the main reason 5G speed tests produce such inconsistent results. A phone showing a “5G” icon could be connected to slow low-band coverage in one location and blazing mid-band or mmWave coverage a few blocks away, with no visual difference in the icon itself to signal which one is active. Carrier network build-out also varies significantly by region and even by neighborhood, since deploying mid-band and mmWave infrastructure is more expensive and slower to roll out broadly than upgrading existing low-band spectrum.

What Actually Determines Your Real-World Speed

Beyond which 5G band a phone connects to, several other factors shape everyday performance: how many other devices are sharing the same cell tower at that moment, the phone’s modem quality and antenna design, physical obstructions between the phone and the tower, and how a carrier prioritizes 5G traffic relative to other users on its network. A flagship phone with a more capable modem can often maintain a stronger connection in marginal coverage areas than a budget phone with a less sophisticated modem, even on the identical network.

5G Standalone vs Non-Standalone

A more technical distinction that increasingly affects real-world experience is whether a carrier runs 5G Standalone (SA) or Non-Standalone (NSA) architecture. Non-standalone 5G still relies on the underlying 4G core network for some functions, which caps certain benefits like ultra-low latency. Standalone 5G runs on an independent 5G core network and unlocks capabilities like network slicing and meaningfully lower latency, which matters more for things like cloud gaming and real-time applications than for typical browsing and streaming.

Sources

• GSMA, 5G network architecture and deployment documentation
• Carrier and equipment manufacturer 5G technical briefings
• Independent mobile network speed testing from major tech outlets
• 3GPP standards documentation on 5G NR frequency bands