MmWave, short for millimeter wave, refers to radio frequencies between roughly 24 GHz and 100 GHz that carry data at extremely high speeds over short distances. In the context most people encounter it, mmWave is the fastest tier of 5G wireless technology, capable of multi-gigabit-per-second throughput. It gets its name from the physical wavelength of these signals, which measures between 1 and 10 millimeters.
Where MmWave Fits in 5G
5G operates across two broad frequency ranges defined by international standards. Frequency Range 1 (FR1) covers 450 MHz to 6,000 MHz, often called “sub-6 GHz.” This is the 5G most people actually use day to day. Frequency Range 2 (FR2) spans 24,250 MHz to 52,600 MHz, and this is the mmWave band. The higher you go in frequency, the more data you can push through the airwaves, but the harder it becomes to send that signal very far.
Think of it like lanes on a highway. Sub-6 GHz 5G has moderate lane width and covers long distances, similar to a rural interstate. MmWave has an enormous number of lanes, allowing a huge volume of traffic, but the road is short. That tradeoff between speed and range defines nearly everything about how mmWave gets deployed.
How Fast MmWave Actually Is
The 5G specification allows for peak data rates up to 20 Gbps. MmWave is the only part of the 5G spectrum that comes close to those numbers. In real-world conditions, users on mmWave connections commonly see download speeds of 1 to 4 Gbps, which is fast enough to download a full-length HD movie in seconds. Average 5G speeds across all bands sit around 100+ Mbps, so mmWave represents a dramatic jump when you can get it.
Latency, the time it takes for data to make a round trip, is also impressive. Measurements from a 2023 study found that the mmWave physical layer can deliver latency as low as 0.09 milliseconds on the downlink and 0.76 milliseconds on the uplink in the best cases. Those are near-instantaneous response times. In practice, though, those best-case numbers happen rarely. Real-world end-to-end latency is higher once you factor in the rest of the network, but mmWave still offers a meaningful improvement over 4G and sub-6 GHz 5G for latency-sensitive tasks.
Why the Signal Struggles With Obstacles
MmWave’s biggest limitation is that high-frequency signals don’t travel far and are easily blocked. Testing by the National Institute of Standards and Technology at 60 GHz found that even common indoor materials cause significant signal loss. Interior glass reduced the signal by 7.5 to 18.1 dB. Plasterboard walls caused 11.8 to 31.6 dB of loss. A wooden door blocked 25.5 to 40.5 dB. A glass door facing the outside of a building averaged 38.5 dB of loss, and exterior building materials caused losses as high as 52 to 66 dB.
To put those numbers in perspective, every 10 dB of loss cuts the signal strength by 90%. So a plasterboard wall at the high end of that range eliminates over 99.9% of the signal. This means mmWave essentially cannot penetrate buildings from the outside in most cases, and even walls within a building can be enough to kill the connection. Rain, foliage, and even your own hand placed over the antenna on a phone can degrade the signal noticeably.
This is why mmWave coverage on your phone is limited to very specific spots: dense urban areas, stadiums, airports, and transit hubs where carriers have installed small cells with direct line of sight to users.
How Beamforming Makes It Work
MmWave would be nearly unusable without a technology called beamforming. Because the wavelengths are so small, engineers can pack dozens or even hundreds of tiny antennas into a single transmitter. These antennas work together as a “phased array,” coordinating their signals to form a focused, directional beam aimed at a specific device rather than broadcasting in all directions.
This is fundamentally different from how a traditional cell tower works. A conventional tower radiates signal broadly, like a lightbulb filling a room. A mmWave base station acts more like a spotlight, concentrating its energy where it’s needed. The system continuously adjusts the beam’s direction to track moving devices, which is critical for maintaining a connection as you walk or drive. This approach, combined with massive MIMO (using large numbers of antennas simultaneously), is what makes mmWave practical despite its physical limitations.
Where MmWave Gets Used
On consumer phones, mmWave availability is still limited. Only certain flagship devices support it, and coverage maps are small. You’ll find it in parts of downtown cores in major cities, inside select airports, and in some sports venues where tens of thousands of people need connectivity at the same time. If you’ve seen a speed test screenshot showing 2 or 3 Gbps on a phone, it was almost certainly on mmWave.
The more transformative uses are happening in fixed wireless access and enterprise settings. Fixed wireless access uses mmWave to deliver broadband internet to homes and businesses without running physical cables. A small antenna on the outside of a building receives the mmWave signal from a nearby base station, providing speeds that rival or exceed wired fiber in some cases. This approach is particularly valuable for connecting areas where laying fiber is expensive or impractical. The Global mobile Suppliers Association has identified mmWave fixed wireless as one of the top revenue-generating use cases for 5G operators.
In industrial settings, mmWave enables high-speed wireless connections for factory automation, real-time video monitoring, and telemetry in locations that are difficult to wire. Stadiums and convention centers use it to serve dense crowds without the network grinding to a halt. These controlled environments play to mmWave’s strengths: short distances, line of sight, and an enormous appetite for bandwidth.
Safety and Exposure Standards
MmWave frequencies fall well within the range covered by international safety guidelines. The International Commission on Non-Ionizing Radiation Protection updated its exposure limits in 2020 to cover all radiofrequency energy from 100 kHz to 300 GHz, explicitly including 5G mmWave bands. These guidelines set maximum power density levels that devices and base stations must stay below, and they’re based on decades of research into how radiofrequency energy interacts with biological tissue.
At mmWave frequencies, the energy is absorbed almost entirely by the outer layers of skin and doesn’t penetrate deep into the body. The primary biological effect at high exposure levels is heating, similar to other radiofrequency bands. Commercial mmWave devices operate at power levels far below the thresholds where measurable heating occurs. Regulatory agencies in the U.S., Europe, and most other countries require all wireless equipment to comply with these limits before it can be sold.
MmWave vs. Sub-6 GHz 5G
- Speed: MmWave delivers multi-gigabit speeds in ideal conditions. Sub-6 GHz typically ranges from 100 to 900 Mbps.
- Range: A single mmWave small cell covers a few hundred meters at most. Sub-6 GHz towers cover several kilometers.
- Obstacle handling: MmWave is blocked by walls, glass, and even heavy rain. Sub-6 GHz passes through most buildings with moderate loss.
- Availability: Sub-6 GHz 5G is widely deployed. MmWave is concentrated in dense urban spots and specific venues.
- Hardware: MmWave requires dedicated antenna modules in phones, which adds cost and uses more battery. Not all 5G phones include them.
For most people most of the time, sub-6 GHz 5G is what you’re actually connected to. MmWave is the performance ceiling of the technology, deployed strategically where raw speed and capacity matter most.