The core trade-off
Indoor units are easier to install and need no external work. Outdoor units deliver better performance. The right choice depends on your coverage quality, building construction, and how much performance matters relative to installation simplicity.
Indoor CPE: pros and cons
Pros: No external work, no drilling or cable runs, no need for a ladder or roof access. Plug in and configure. Can be repositioned easily if you move or if signal conditions change. No weatherproofing concerns. Lower installation cost if you are using an installer.
Cons: The 5G signal must pass through the building fabric before reaching the antennas. Brick walls typically attenuate signal by 10-15 dB. Concrete and metal-clad structures attenuate more. Double glazing with a metallic coating can attenuate the signal by 20-30 dB. On marginal sites, the attenuated indoor signal may not support stable 5G connectivity.
Outdoor CPE: pros and cons
Pros: Antennas are outside the building, receiving the full signal before any building attenuation. On a marginal site, an outdoor unit often means the difference between a working and non-working 5G connection. On a good site, an outdoor unit delivers noticeably better sustained throughput than an indoor equivalent.
Cons: Requires mounting on an exterior surface. Needs a PoE cable run from the outdoor unit through or around the building fabric to the indoor PoE injector. Requires access for installation. More complex to reposition if needed. Slightly higher upfront cost than an indoor unit in the same tier.
The hybrid option: indoor router with external antenna
A third option is an indoor router fitted with an external MIMO antenna on a coaxial cable, mounted outside or in a window. This is more flexible than a dedicated outdoor CPE because the router is easily accessible indoors for maintenance and configuration, while the antenna captures signal outside the building.
Performance is slightly below a purpose-built outdoor CPE (due to cable losses and the difference between a modem board designed for outdoor use versus indoor), but often significantly better than an indoor-only antenna. This approach suits buildings where mounting a full outdoor CPE is difficult or where the cost of a dedicated outdoor unit is a constraint.