Many users experience internet speeds significantly higher via cable than via wireless. This phenomenon raises numerous questions and is often attributed to equipment malfunction or provider greed. However, the reality lies in the physics of radio waves and the operating principles of network equipment. A router doesn't simply transmit a signal; it encodes the data, packages it into packets, and coordinates transmission between multiple devices.
The reduction in speed is an inevitable tradeoff for portability and convenience. Under ideal laboratory conditions, losses are minimal, but in a real apartment with concrete walls and a working microwave, the figures can vary significantly. It's important to understand that provider speed — this is just an incoming flow that the router must distribute correctly.
In this article, we'll examine the technical reasons why your router throttles your speed and determine whether this is a critical issue or normal operation. You'll learn how Wi-Fi standards affect throughput and why the 1200 Mbps advertised on the box doesn't necessarily translate to the same speed on your smartphone.
The Physics of Loss: Why Wi-Fi Is Always Slower Than Cable
The main reason for the decline is the half-duplex mode of wireless network operation. Unlike an Ethernet cable, where data can be transmitted simultaneously in both directions (full-duplex), Wi-Fi operates like a walkie-talkie: only one participant can speak at a time. This automatically divides the available bandwidth in half, as the router must first receive the packet, verify it, and then send an acknowledgment.
Furthermore, a significant portion of airtime is taken up by overhead data. Security protocols, packet headers, acknowledgement signals (ACK), and collision avoidance can consume up to 40% of the theoretical link speed. If you see a 100 Mbps rate, the actual (useful) speed over the air will be significantly lower due to overhead. TCP/IP protocol.
⚠️ Attention: Don't confuse connection speed (link) with actual file download speed. The link shows the theoretical maximum agreed upon by the devices, but actual data transfer is always lower due to service traffic.
The situation is exacerbated by interference. Radio waves are subject to attenuation when passing through obstacles, reflection from metal surfaces, and interference with neighboring routers. Each signal distortion forces the equipment to request a packet retransmission, which directly reduces overall network performance.
The Impact of Wi-Fi Standards on Real-World Throughput
The speed you get directly depends on the wireless standard supported by your router and client device. Older standards like 802.11n (Wi-Fi 4) have strict speed limits even under ideal conditions. Modern standards Wi-Fi 6 (802.11ax) Routers are capable of delivering speeds comparable to gigabit cable, but only if your smartphone or laptop also supports this standard.
It's important to note that manufacturers often list the combined speed for all bands and antennas. For example, "AC1200" means the router can deliver up to 300 Mbps in the 2.4 GHz band and up to 867 Mbps in the 5 GHz band. However, a single device is typically connected to only one frequency and uses one or two antennas, so the actual speed will be a fraction of the stated figure.
Below is a table showing the approximate ratio of theoretical and actual speed for various standards in conditions of average air noise:
| Wi-Fi standard | Theoretical maximum | Actual speed (one lane) | Efficiency |
|---|---|---|---|
| 802.11n (Wi-Fi 4) | 150 - 300 Mbps | 70 - 130 Mbps | ~45-50% |
| 802.11ac (Wi-Fi 5) | 433 - 867 Mbps | 250 - 500 Mbps | ~55-60% |
| 802.11ax (Wi-Fi 6) | 1200+ Mbps | 700 - 900 Mbps | ~60-70% |
| Gigabit Ethernet | 1000 Mbps | 940 - 980 Mbps | ~95% |
As the data shows, wireless technologies are constantly evolving, narrowing the gap between cable and air. However, even top-end models can't completely overcome the physical limitations of radio waves. When choosing equipment, consider performance headroom, especially if your plan exceeds 100 Mbps.
Frequency Bands: The Battle of 2.4 GHz vs. 5 GHz
Choosing a frequency is a trade-off between range and speed. Range 2.4 GHz This band is the busiest. It's used not only by neighbors' routers, but also by Bluetooth headsets, wireless mice, baby monitors, and even microwave ovens. In an apartment building, the airwaves in this range are literally clogged with noise, forcing the router to constantly switch channels and reduce speed to ensure stability.
The 5 GHz band offers many more open channels and lower noise levels. This is where maximum speeds are achieved, close to those of cable. However, these waves have a shorter wavelength, are less able to bend around obstacles, and attenuate faster in walls. If you are in the same room as your router, the speed on 5 GHz can be 3-4 times faster than on 2.4 GHz.
Why is 2.4GHz so slow?
The 2.4 GHz band has only three non-overlapping channels (1, 6, 11). In an apartment building, each of these channels can be used by dozens of neighboring routers, creating constant collisions and forcing your device to wait its turn to transmit data.
Modern dual-band routers can automatically switch devices to the best frequency (Band Steering), but they don't always do it correctly. Sometimes it makes sense to manually separate networks by giving them different names (SSIDs) to force high-speed devices to connect to the 5 GHz band while keeping smart home devices on the 2.4 GHz band.
⚠️ Attention: Router settings interfaces are regularly updated by manufacturers. The layout of menu items may differ from what's described. If you can't find a specific setting, check the instructions for your model on the vendor's official website.
Processor power and router load
A router is a fully-fledged computer with a processor (CPU) and RAM. At high internet speeds (over 300-500 Mbps), budget models may struggle to handle the data flow. The processor simply can't process packets, resulting in increased ping (latency) and a drop in speed. This is especially noticeable when security features or torrents are enabled.
Load on NAT table The connection also plays a role. Every open connection (browser tab, background app refresh) creates an entry in the router's memory. Cheap devices have limited memory and a weak CPU, so when multiple devices are connected simultaneously, they begin to choke, dropping packets and reducing overall throughput.
If you use additional features such as a built-in VPN client, antivirus traffic scanning, or parental controls with deep filtering, the processor load increases exponentially. In such cases, speed can drop by 50% or more, as every byte of data must be scanned or encrypted in real time.
☑️ Router load diagnostics
Impact of interference and equipment placement
The physical location of the router critically impacts signal quality. Metal structures, mirrors with amalgam coatings, aquariums, and thick concrete walls with rebar are serious obstacles to radio waves. Placing the router in an alcove, behind a TV, or on the floor negates the effectiveness of even the most powerful antennas.
The optimal location is the center of the apartment, 1.5–2 meters above the floor, in an open area. Antennas should be positioned vertically. If the router has internal antennas, it's important to follow the instructions for orientation (usually vertical). It's also a good idea to stay away from sources of electromagnetic interference, such as microwaves, cordless phones, and high-power power supplies.
Interestingly, neighboring routers can interfere even on different channels if they operate in close proximity. In apartment buildings, the Wi-Fi "carpet" can be so dense that even modern equipment struggles to penetrate it. In such cases, the only solution is switching to 5 GHz or using a wired connection for stationary devices.
How to check and minimize speed loss
First, you need to take some measurements. Connect your computer to the router with a cable and measure your speed using a reliable service (such as Speedtest). Record the results. Then, without moving, connect via Wi-Fi and repeat the test. The percentage difference will indicate the effectiveness of your wireless network.
If loss exceeds 30-40% in the 5 GHz band with line of sight, it's worth checking your settings. Make sure the channel width is set to maximum (80 MHz or 160 MHz for Wi-Fi 6). Check if the operating mode is set to compatibility with older devices (e.g., b/g/n only), which may limit the speed of newer devices.
It's also a good idea to update your router's firmware. Manufacturers frequently release updates that improve the stability of the radio module and traffic management algorithms. In some cases, a factory reset and reconfiguration can help resolve software errors that accumulate over time.
Why does Wi-Fi speed drop in the evening?
In the evening, the load on not only your home network but also your provider's lines increases, and the number of neighboring routers increases. This leads to signal interference and a reduction in the available bandwidth from your service provider.
Can an old router cut the speed of a new plan?
Yes, absolutely. If a router has Fast Ethernet ports (100 Mbps), it physically won't allow speeds higher than that, even if your plan allows 500 Mbps. Also, older Wi-Fi standards won't be able to provide higher speeds.
Does the number of connected devices affect the speed?
Yes, it does. Wi-Fi is a shared medium. The more devices actively transmitting data, the less airtime each one gets. Passive devices (in idle mode) have virtually no impact on speed.