Can You Talk on the Phone Over Wi-Fi? When It Works and When It Doesn't

Wi-Fi in brief

Wi-Fi is a commercial name for a wireless local network technology: instead of a cable, the data travels by radio waves between the device and an access point (Access Point) — the box with the antennas, which is often built into the router.

The waves travel in two main frequency bands, and in newer devices in a third as well:

For calls, 5 GHz is usually better: less crowded and less interference. 2.4 GHz is useful when the device is far away, but that is also where the chance of dropouts is highest.

Why a call is more sensitive to Wi-Fi than browsing

On Wi-Fi, all the devices connected to the same access point share the same air. Only one device "talks" at any moment, and the rest wait their turn. When there are many devices, or one device downloading a video, the wait gets longer.

When browsing, you don't notice it — a page loads in half a second. In a call, every voice packet has to arrive within milliseconds. Short, irregular waits create jitter, and in severe cases packet loss — and the voice sounds "robotic" or cuts out.

In addition, Wi-Fi is affected by things that have nothing to do with the network: concrete and stone walls, metal, mirrors, a refrigerator, a microwave, and the neighbors' networks on the same channel. A network cable is not affected by any of these.

Rule one: if it can be on a cable, put it on a cable

A desk phone stays in one place. There is no reason to connect it over Wi-Fi, and there are many reasons not to. A network cable gives a stable connection, without interference and without competition from other devices, and with PoE it also powers the phone — so there's no need for a power adapter at every desk.

The same is true for the station of a call-center agent or a representative who talks all day: even if they use a softphone, their computer should be connected by cable. The difference is noticeable in every call, all day long.

Wi-Fi is for things that really move: mobile phones, laptops in meeting rooms, and employees who walk between rooms.

A softphone on Wi-Fi

A softphone — an app that turns a mobile or computer into an extension — usually works over Wi-Fi, and that is perfectly fine when the network is well built. A few things greatly improve the experience:

• Connect to 5 GHz when possible, rather than 2.4.
• Stay close to an access point — not two rooms away, behind a stone wall.
• A headset — reduces echo and background noise, and improves the call more than you'd expect.
• Close heavy downloads on the computer during important calls.
• Switching networks — when the mobile switches from Wi-Fi to cellular in the middle of a call, the call may cut out for a moment or disconnect. On a long walk, it's better to decide in advance on one network.

Power saving — the silent enemy of the softphone

Mobile phones try to save battery. When the screen is off, they "put the Wi-Fi to sleep," limit apps running in the background, and sometimes close them entirely. For a softphone this is a problem: it has to stay awake to hear that a call is coming in.

The familiar sign: "When the phone is in my hand, everything works. When it's in my pocket, calls don't arrive, or arrive late." Laptops have a similar phenomenon: the sleep mode or "power saving" of the network card disconnects the softphone.

What to do: in the mobile settings, exempt the softphone app from "battery optimization," allow it to run in the background, and check that Wi-Fi is not set to disconnect when the screen is off. On a computer, turn off power saving for the network card. Many apps today also use push notifications to "wake up" the mobile when there is a call, and that solves a large part of the problem.

Access points: one big one or several small ones

A single router with strong antennas at the end of the office will not cover the whole floor well. The signal weakens at every wall, and in the far room devices will barely connect, and will also slow down everyone else.

The professional solution is several access points, spread out so there is a good signal everywhere, with each one connected by cable to a switch — usually with PoE, so that it gets power from the cable and can be hung on the ceiling. They are managed together, broadcast the same network name, and the device moves between them as you walk.

A cordless phone in the office: Wi-Fi or DECT

Someone who needs to move around with the phone — a warehouse worker, a gabbai, a shift supervisor — doesn't have to use a softphone on Wi-Fi. There is an older technology built specifically for calls: DECT, the technology of the home cordless phone.

With DECT there is a base station connected to the network by cable, and wireless handsets that talk only to it, on a separate frequency with no computers, videos or neighbors on it. The result: more stable calls, a battery that lasts days, and a handset that feels like a regular phone.

A guest network — separating the noise

In an institution where guests, students or suppliers connect to the Wi-Fi, they share the same air and the same line as the office phones. One video downloaded in the waiting room can be felt on a call in the secretary's office.

Most modern access points and routers allow a separate guest network, with a speed limit. That way guests get internet, and the staff's phones and computers get priority. In larger sites the network is also separated at the network level (VLAN) and QoS is configured.

A real-life example: the secretary who moved rooms

At a school (a made-up name: "Talmud Torah Nachalat Yaakov"), the secretary, Rivka, moved to a room on the upper floor, and her desk phone was connected there to the Wi-Fi through a wireless adapter, because there was no network jack in the room. From that day on, parents complained that she "sounds like a robot."

A check showed that the adapter connected at 2.4 GHz, through a concrete ceiling, to the router on the floor below — and during break hours dozens of staff devices connected to the same network. One network cable was run from the communications cabinet to the room, and the phone was connected by cable. The complaints stopped the same day.

How to test Wi-Fi for calls

Before deciding that Wi-Fi is "not suitable," it's worth testing it in an orderly way:

1. Signal strength — most devices show it in bars; apps show it as a negative number (dBm). For calls, the common target is a signal of about -67 dBm or stronger (that is, a number closer to zero).
2. A continuous ping from the device to the router, for a few minutes. On good Wi-Fi it will be low and steady; jumps to hundreds of milliseconds indicate a problem.
3. A test at a busy hour — Wi-Fi at eight in the morning is very different from Wi-Fi at twelve noon.
4. A test call while walking — move between the rooms during a call, and notice where the voice starts to cut out.

The places where the call cuts out are exactly the places where another access point is needed — or a cable.

Wi-Fi at home, for remote workers

An employee working from home with a softphone or a desk phone depends on their home network. There are usually no professional access points there, and everyone in the household shares the same router.

The simplest and most effective step: one network cable from the router to the desk. If that isn't possible, place the router close to the work corner, connect at 5 GHz, and ask the family not to download heavy files during important calls.

For someone who spends a lot of time on the phone from home, it's also worth considering a desk phone connected by cable to the home router — it behaves exactly as it does in the office, as an extension of the phone system.

Channels and neighbors

Every Wi-Fi network broadcasts on a certain channel within the frequency band. In an office building or on a crowded street, dozens of neighbors' networks broadcast on the same channels, and in 2.4 GHz in particular there are only three channels that don't overlap one another.

Most routers choose a channel automatically, and sometimes they choose poorly. Simple scanning apps show which channels are busy in the area, and the network can be moved to a clearer channel. In 5 GHz there are many more channels, and that is another reason it is better suited to calls.