Wired Versus WiFi: Why This Decision Matters More Than You Think

Your Office Network: Part 2 of 10

In the previous post, we walked through every piece of equipment between your internet connection and your desk. Now we are going to focus on the single decision that has more impact on VoIP call quality than almost anything else in your office: whether your voice devices are connected with a cable or over Wi-Fi.

This is not a nuanced, "it depends" kind of answer. For voice traffic specifically, wired Ethernet is better. Meaningfully, measurably, consistently better. The rest of this post explains why, puts real numbers on the difference, and then addresses what to do when running a cable genuinely is not an option.

How wired Ethernet works

An Ethernet cable between your phone and a switch is a dedicated, point-to-point connection. The phone has the full bandwidth of that link available to it at all times. No other device shares it. No other device can interfere with it. The signal travels over copper (or fiber, in some cases) in a controlled, shielded environment.

When your phone sends a packet, it goes directly to the switch with no contention, no waiting, no retransmission. The switch reads the destination and forwards it, typically in under a microsecond. The round-trip time for a packet to travel from your phone to the switch and back is measured in fractions of a millisecond.

The result is consistency. A wired Ethernet connection delivers the same performance at 9 AM on a quiet Monday morning as it does at 2 PM on a busy Thursday afternoon. Measure the jitter, which is the variation in packet arrival times, on a healthy wired access link and you will typically see well under 1 millisecond. Packet loss on that link is effectively zero unless there is a hardware problem or a cable issue.

This consistency is exactly what voice traffic needs. As we covered in why voice is hard, the human ear is extraordinarily sensitive to irregularity. It is not the average latency that kills call quality; it is the spikes. And a wired access link simply does not produce spikes under normal operation.

One important caveat: this describes the link between your device and its switch. Wired traffic can still queue further along the path: at an oversubscribed uplink between switches, or at the WAN egress where a gigabit LAN funnels into a much smaller internet connection. Going wired removes the shared-medium problem at the access layer; it does not exempt you from congestion at the bottlenecks, which is why QoS still matters even on an all-wired network.

How Wi-Fi works and why it is different

Wi-Fi seems like the same thing without the cable. Your device sends data, the access point receives it, and it reaches the network. But the underlying mechanics are fundamentally different, and those differences have consequences that matter for real-time audio.

It is a shared medium

A wired connection is a private conversation between your device and the switch. A Wi-Fi connection is more like a conference call where everyone has to take turns talking.

Every device connected to the same access point shares the same radio channel. The Wi-Fi protocol (technically, CSMA/CA) requires each device to listen before transmitting. If the channel is busy, the device waits. If two devices transmit at the same time and collide, both back off for a random interval and try again. The more devices on the channel, the more waiting, the more collisions, the more retransmissions.

This means that even if your phone only needs a tiny amount of bandwidth for a voice call, it still has to wait its turn when 25 other devices are also trying to send data. That waiting time is variable and unpredictable, which is the definition of jitter.

The air is noisy

The radio frequencies that Wi-Fi uses, particularly the 2.4 GHz band, are shared with an enormous number of other devices and technologies. Bluetooth headsets, wireless mice and keyboards, microwave ovens, baby monitors, cordless phones (the old kind), wireless security cameras, and your neighbors' Wi-Fi networks are all operating in or near the same frequency range.

Interference from these sources corrupts packets in transit. When a Wi-Fi packet is corrupted, the receiving device does not get it and does not send an acknowledgment back. The sending device waits, times out, and retransmits. This adds latency that varies depending on the radio environment at that particular moment, which is, again, jitter.

Signal strength varies constantly

Wi-Fi signal strength depends on distance, obstacles, and the physical environment. A phone sitting three feet from an access point with clear line of sight gets an excellent signal. The same phone on a desk 40 feet away, on the other side of two walls and a filing cabinet, gets a much weaker signal.

Weaker signal means lower data rates and higher error rates. The Wi-Fi system adapts by dropping to a lower modulation scheme that is more resilient but slower. And the signal strength is not static. People walking through the office, doors opening and closing, even changes in humidity can cause the signal to fluctuate. Each fluctuation can cause a momentary increase in errors and retransmissions.

Roaming disruptions

In offices with multiple access points, devices sometimes switch from one access point to another as you move around or as signal conditions change. This handoff takes time. With older Wi-Fi standards, it can cause a disruption of several hundred milliseconds. With modern fast roaming (802.11r fast transition, assisted by 802.11k neighbor reports and 802.11v steering), the disruption is shorter, but it is not zero.

If a roaming event happens during an active call, you get a brief audio dropout. Most people experience this as a momentary gap in the conversation. It is not catastrophic, but it is the kind of thing that wired connections simply never produce.

The numbers

The figures below are representative measurements from typical office networks during business hours: the kind of results you should expect to see when you measure your own, not thresholds from a standard. Your environment will produce its own numbers, which is exactly why measuring beats quoting: run a VoIP quality test on both a wired and a Wi-Fi device and compare.

Jitter

Measured on a wired Ethernet connection to a managed switch, jitter typically comes in at 0.5 to 1 millisecond. It stays in that range almost all the time, regardless of how busy the network is, because the access link is not shared. (What test tools report is the RFC 3550 interarrival jitter estimate, a running statistical average, not a worst-case spike, which is worth remembering when comparing numbers.)

On Wi-Fi under normal load (10-15 devices per access point, moderate traffic), measurements commonly show 10 to 30 milliseconds. Most VoIP playout buffers can absorb this, so calls usually sound okay; the audible impact of jitter always depends on how much delay the jitter buffer adds and how many late packets it has to discard, not on the raw number crossing some universal line.

On Wi-Fi under heavy load (25+ devices, video calls, file transfers, people streaming), measured jitter regularly spikes to 50 milliseconds or higher. At these levels, typical jitter buffers start discarding packets because they arrive too late to play back. The result is choppy, robotic audio.

The difference between 1 millisecond of jitter and 50 milliseconds of jitter is the difference between perfect call quality and a conversation that is frustrating to have.

Packet loss

On a healthy wired access link, measured packet loss is effectively 0%. If you are measuring loss on the link between a device and its switch, something is wrong with the cable, the switch, or the device; it is not a characteristic of the technology. (Wired traffic can still be dropped further along the path when a congested uplink or WAN egress queue overflows, but that is a congestion problem QoS addresses, not a property of the wire.)

On Wi-Fi under good conditions, measured packet loss runs 0.1% to 0.5%. That sounds negligible, but it means one to five out of every thousand packets do not arrive. For a voice call sending 50 packets per second, that is occasional brief gaps in the audio. Most codecs can conceal occasional isolated losses at this level reasonably well.

On Wi-Fi under stress, measured loss can spike to 2% or higher during interference events or heavy congestion, and Wi-Fi loss tends to come in bursts, which is harder on concealment than the same percentage spread evenly. Around that level, packet loss concealment audibly breaks down. This is the kind of thing you hear on that afternoon call that sounds terrible even though the morning calls were fine.

Latency

Wired connections add less than 1 millisecond of latency between the device and the switch. Measurements on Wi-Fi typically show an added 3 to 10 milliseconds under light load and 20 to 50 milliseconds under heavy load. This is on top of the latency from the rest of the network path (router, internet, VoIP provider).

By itself, an extra 10 or 20 milliseconds of latency might not be a deal-breaker. But latency compounds. If Wi-Fi adds 20 milliseconds, and your router adds 5 milliseconds because it is not prioritizing voice, and the internet path adds 40 milliseconds, and the far end has a similar setup, you are approaching 150 milliseconds of one-way mouth-to-ear delay, the planning boundary ITU-T G.114 cites for conversational speech. That is a transmission-planning guideline, not a cliff where audio suddenly fails, but as total one-way delay climbs into that territory people increasingly start talking over each other because the delay is perceptible. We covered this pattern in audio delay and talking over each other.

The recommendation

If a device is used for voice calls, it should be on a wired Ethernet connection if at all possible. This includes desk phones, computers running softphone applications, and headsets that connect to a computer which is itself on the network.

This is not about being anti-wireless. Wi-Fi is great for laptops, tablets, and phones that need to move around. It is great for email, web browsing, and even video streaming, because those applications can tolerate jitter and brief interruptions without the user noticing. Real-time voice is different. It has no tolerance for inconsistency, and wired Ethernet delivers consistency that Wi-Fi cannot match.

The cost difference is negligible. A Cat 6 Ethernet cable from the wall jack to a phone costs a few dollars. Running a new cable from the network closet to a desk, if one does not already exist, costs more, but it is a one-time investment that eliminates the Wi-Fi variable permanently.

In most offices, the infrastructure for wired connections already exists. The building has cable runs to the desks, there are wall jacks, there is a patch panel in the closet. The phones just need to be plugged in. The problem is usually not that wired is impossible, it is that someone set up the phones on Wi-Fi because it was easier at the time and nobody realized the trade-off they were making.

When Wi-Fi is unavoidable

Sometimes running a cable genuinely is not practical. Historic buildings where you cannot open walls. Temporary offices. Shared coworking spaces. Employees who move between desks regularly. There are legitimate reasons why some voice devices end up on Wi-Fi.

If that is your situation, here is how to make the best of it.

Use 5 GHz or 6 GHz, never 2.4 GHz

The 2.4 GHz band has three non-overlapping channels. In any urban or suburban environment, those three channels are saturated with signals from neighboring networks and other devices. The 5 GHz band has over 20 non-overlapping channels, far less interference, and higher throughput. The 6 GHz band (Wi-Fi 6E) is even better, with more channels and virtually no legacy device interference today.

The trade-off is range. 5 GHz and 6 GHz signals do not penetrate walls as well as 2.4 GHz. But for voice quality, the reduction in interference far outweighs the reduction in range. If range is a problem, the answer is more access points, not falling back to 2.4 GHz.

Configure your access points and voice devices to prefer 5 GHz. Many access points have a band steering feature that nudges dual-band devices toward 5 GHz automatically.

Enable WMM (Wi-Fi Multimedia)

WMM is a Wi-Fi Alliance specification that provides basic traffic prioritization over the air. It defines four access categories: voice, video, best effort, and background. When WMM is enabled, voice-tagged traffic gets priority access to the wireless medium, reducing the wait time caused by contention.

Most modern access points support WMM and have it enabled by default. Verify that it is on and that your VoIP devices are correctly tagging their traffic so it lands in the voice category: in practice that means marking voice packets with DSCP EF (46), the RFC 4594 telephony class, and then confirming the access point actually maps EF to the WMM voice category. That mapping is not the default: the common shortcut of taking the DSCP's top three bits lands EF in the video category instead, and RFC 8325 on mapping DSCP to 802.11 exists precisely to recommend the corrected EF-to-voice mapping.

WMM helps, but it is not magic. It reduces contention delay but cannot eliminate the fundamental variability of a shared radio medium. Think of it as the difference between bad and less bad, not between bad and good.

Limit clients per access point

The more devices sharing an access point, the more contention and the more jitter. For environments where voice quality matters, aim for no more than 15 to 20 devices per access point, and fewer if those devices are generating heavy traffic like video calls.

This usually means deploying more access points at lower power rather than fewer access points at high power. Each access point covers a smaller area but serves fewer clients with better performance.

Ensure strong coverage

A voice device with a weak Wi-Fi signal is a voice device with unreliable audio. Conduct a basic site survey to identify dead spots and weak areas. Every location where someone might take a call should have strong, stable signal from at least one access point.

Consider Wi-Fi 6 (802.11ax) or Wi-Fi 6E

Wi-Fi 6 introduced several technologies that specifically help in dense environments. OFDMA (orthogonal frequency-division multiple access) allows an access point to communicate with multiple devices simultaneously rather than one at a time. Target wake time reduces contention from idle devices. BSS coloring helps manage interference from neighboring networks.

These improvements reduce jitter and contention meaningfully compared to Wi-Fi 5 (802.11ac). If you are stuck with Wi-Fi for voice and your access points are older than Wi-Fi 6, upgrading them is one of the highest-impact changes you can make.

Wi-Fi 6E adds the 6 GHz band, which is currently uncrowded and provides the best wireless experience available. If your voice devices support 6 GHz, this is the best wireless option.

The "it works fine on Wi-Fi" trap

You will hear people say their VoIP works perfectly on Wi-Fi. And they might be right, in their specific situation. A home office with one person, one access point, and a handful of devices on a 5 GHz channel will produce excellent Wi-Fi performance. A single user in a quiet part of the office near an access point will have a good experience.

The problem is that these conditions do not represent the worst case. They represent the best case. Wi-Fi performance degrades as load increases, as interference increases, and as environmental conditions change. The call that sounds great at 9 AM when the office is half empty may sound terrible at 2 PM when everyone is back from lunch and running video calls and syncing files.

When people say "Wi-Fi works fine," what they often mean is "I have not noticed a problem yet." The problems tend to surface gradually, as the office grows, as more devices are added, as usage patterns shift. By the time the afternoon call quality problem is obvious, the root cause is buried under months of incremental changes.

Testing under realistic conditions, during peak load, over a meaningful time period, is the only way to know whether your Wi-Fi can actually handle voice traffic reliably. Running a VoIP quality test from a WiFi-connected device during your busiest hours will show you exactly what your calls are experiencing.

The bottom line

Wired Ethernet gives you consistency. Wi-Fi gives you convenience. For voice, consistency wins.

If you are setting up a new office, experiencing call quality problems, or just want to eliminate variables, plug your voice devices into the wall. Use Wi-Fi for everything that does not need real-time, low-latency delivery. This simple division solves more VoIP quality problems than any other single change.

What comes next

Now that we have covered the connection between your device and the network, the next post dives into the equipment that ties everything together: the network switch. Switches are the unsung heroes of your network, and understanding the difference between a basic unmanaged switch and a properly configured managed switch can transform your network's ability to handle voice traffic.

This is Part 2 of the Your Office Network series. Part 3: Switches: The Unsung Hero of Your Network explains why the right switch makes all the difference.