Many users mistakenly believe that the internet speed shown in online tests is the only indicator of the quality of their wireless network. In fact, local WiFi speed — This is a separate parameter that determines how quickly your devices exchange data with each other, for example, when streaming video from a NAS server or gaming over a local network. If the router is malfunctioning or the communication channel is overloaded with interference, the provider's gigabit plan won't prevent lags when transferring files within the apartment.
Understanding how to properly measure channel throughput without access to the external internet allows you to identify equipment bottlenecks. Often, the problem lies not in the provider's tariff, but in signal interference or an outdated encryption standard that artificially reduces actual performance. In this article, we'll examine professional diagnostic methods used by system administrators to accurately assess the health of their wireless infrastructure.
Before undertaking complex tests, it's important to rule out obvious factors that could affect the results. Ensure the device being tested is in a strong reception area and that background downloads on other devices are stopped. Actual connection speeds in the 5 GHz band can be 3-4 times faster than in the crowded 2.4 GHz band., so the choice of frequency plays a critical role in the final figures.
Factors Affecting Actual WiFi Throughput
The data transfer speed in a local network is affected by many variables, ranging from the physical distance to the router to software settings. Channel width — one of the key parameters: using a 20 MHz bandwidth ensures stability but limits speed, while 40, 80, or even 160 MHz allow for more data transfer but are more susceptible to interference. In multi-apartment buildings, choosing a wide channel often leads to collisions with neighboring networks.
Another important aspect is the security standard and encryption protocol. The use of outdated WEP or early WPA may limit connection speed as modern adapters switch to compatibility mode. For maximum performance, you should use WPA3 or at least WPA2-AES, which guarantees high speeds without hardware limitations.
⚠️ Please note: Having multiple connected IoT devices (smart bulbs, sockets) on the 2.4 GHz frequency can create micro-breaks in the connection that are not visible in the normal network status, but significantly reduce throughput when transferring large files.
It's also worth considering the number of spatial streams (MIMO) supported by your router and client device. If the router has a 4x4 antenna system and the smartphone only supports 1x1, the speed will be limited by the phone's capabilities. Furthermore, channel fill factor (Channel Utilization) shows what portion of the airtime is occupied by data transmission, which directly correlates with ping and connection stability.
Using specialized software for LAN testing
To obtain objective data on network speed, simply copying a file and checking the time is not enough. Professionals use utilities that generate controlled traffic between two nodes. One of the most popular and accurate programs is iPerf3It allows you to run a server on one device (for example, a PC connected via cable) and a client on another (the laptop or smartphone being tested), after which it measures the maximum channel throughput.
The setup process requires minimal command-line knowledge. A listening process is started on the server machine, and the client machine sends data packets of a specified size over a specified period of time. TCP protocol, used by default, simulates real file transfers, taking into account packet loss and retransmissions, which gives the closest picture to reality.
iperf3 -sThis command starts the server in connection-listening mode. To run the test from another device, use the command specifying the server's IP address:
iperf3 -c 192.168.1.105 -t 30Here -c denotes the client mode, followed by the server IP address, and -t 30 Sets the test duration to 30 seconds. The results will show average speed, jitter, and packet loss percentage. It's important to run tests in both directions, as Wi-Fi is often asymmetrical due to antenna operation and traffic prioritization algorithms.
☑️ Preparing for the speed test
Measuring Speed via File Transfer (Practical Method)
If installing console utilities seems too complicated, you can use the operating system's built-in tools. Copying a large file over a local network provides an indication of the actual user speed. To do this, create a shared folder with full access on one computer and place a file of at least 1-2 GB there to eliminate the impact of caching and connection opening time.
When copying a file to the device being tested via WiFi, Windows displays the current transfer speed. However, it's worth remembering that the file system and SMB protocol overhead may slightly lower the final figures compared to a clear connection. For increased accuracy, use NFS protocol or set up an FTP server that has lower overhead when transferring data.
| Parameter | Description of influence | Recommended value |
|---|---|---|
| File size | Small files test IOPS, large files test throughput. | More than 500 MB |
| Disc type | HDD write speed may be a bottleneck | SSD on both ends |
| Protocol | SMBv1 is slower and less secure | SMBv2/v3 or FTP |
| Antivirus | Can scan traffic in real time | Temporarily disable |
Pay attention to the speed behavior during the copy process. If it starts high and then drops sharply and stabilizes at a low level, this may indicate overheating of the router's WiFi module or a buffer overflow. Throttling Equipment failure is a common problem with cheap routers under long-term load.
⚠️ Note: When testing by copying files, make sure that your antivirus software does not scan the transferred data in real time, as this will artificially lower the test result to 10-20 Mbps.
Analysis of signal quality and interference levels
High speed is impossible without a high-quality signal. This parameter is used for diagnostics. RSSI (Received Signal Strength Indicator), which shows the received signal strength in dBm. Values closer to 0 are better: for example, -40 dBm is an excellent signal, -70 dBm is marginal, and -85 dBm and below often lead to connection drops.
However, signal strength alone is not enough. The parameter SNR (Signal-to-Noise Ratio) is the signal-to-noise ratio. If there's a lot of interference in the air from microwaves, Bluetooth devices, or neighboring routers, the SNR drops, and speeds decrease even with full "splitting" on the smartphone screen. For spectrum analysis, apps like WiFi Analyzer or Acrylic Wi-Fi.
Channel visualization helps you choose the least crowded frequency. In the 2.4 GHz band, it's best to use only channels 1, 6, and 11, as they don't overlap. In the 5 GHz band, there's a wider choice, and it's best to use automatic channel selection or manually switch to a clear section of the spectrum.
Why does the speed drop in the evening?
In the evening, when neighbors are actively using the internet (streaming, gaming), the airwaves become saturated with signals. The router is forced to wait longer for the channel to clear before sending packets, which increases latency and reduces overall throughput, even if your signal remains strong.
Comparison of wired and wireless connections
To understand how efficient your WiFi is, you need to compare it to the benchmark—the speed of a wired connection. Connect your laptop directly to the router via cable. Ethernet and run the same test (using iPerf or copying the file). The difference between the resulting numbers will show the losses in the "air" section.
Under ideal conditions, the modern standard WiFi 6 (802.11ax) It can reach 70-80% of the speed of a gigabit cable. If you see rates below 50%, it's time to consider replacing the router, reconfiguring the antennas, or switching to a mesh system. A cable connection typically provides a stable 940+ Mbps on a gigabit port, while WiFi always incurs overhead due to service headers and packet delivery confirmation.
It's also worth checking the negotiated speed (link speed) in the connection properties. In Windows, you can see this in Network Connections → StatusIf the physical connection speed (Link Speed) is low, for example, 54 Mbps or 150 Mbps, then the actual data transfer rate will be even lower. This often happens when the device is located far from the router and switches to an older, but longer-range standard.
Optimizing your router settings for maximum speed
Once you've identified the issues, you can try to improve the situation using software methods. Go to your router's control panel (usually at 192.168.0.1 or 192.168.1.1) and check the wireless network mode. Make sure that the mixed mode is selected, which supports new standards, for example, 802.11 ac/ax mixed, but disable support for very old standards (b/g) if you don't have any old devices in your home, as their presence can slow down the entire network.
Turn on the function MU-MIMO (Multi-User Multiple Input Multiple Output), if available. This technology allows the router to communicate with multiple devices simultaneously, rather than one at a time, significantly improving overall network performance when multiple devices are connected. It also makes sense to separate the 2.4 GHz and 5 GHz networks into different SSIDs (names) to force high-speed devices to connect to the 5 GHz band.
⚠️ Note: Router interfaces are constantly being updated. The location of channel width or MIMO mode settings may vary depending on the firmware version. If you don't see these options, consult the official documentation from the manufacturer of your model.
Don't forget to update your router's firmware to the latest version. Manufacturers frequently release updates that improve radio algorithms and fix WiFi module driver bugs. After changing any settings, be sure to reboot the device for the changes to take effect correctly.
Frequently Asked Questions (FAQ)
Why is the WiFi speed significantly lower than what is stated on the router box?
The speeds of 1200, 1750, or 3000 Mbps indicated on the packaging represent the combined theoretical throughput of all bands and antennas under ideal laboratory conditions. Actual speeds are always lower due to obstacle penetration losses, interference, protocol overhead, and client device limitations.
Does the number of connected devices affect the speed of one client?
Yes, it does. WiFi is a shared medium. The more devices actively transmitting data, the less airtime each one gets. Even if devices are simply browsing the network, they can send out packets, creating contention for the channel.
Can an antivirus slow down the speed of a local network?
Absolutely. If real-time network traffic scanning is enabled in your antivirus settings, every transmitted packet is scanned, creating a delay and straining the device's processor, reducing the overall file copy speed.
Should I buy a WiFi 6 router if I have older devices?
Yes, that makes sense. WiFi 6 (802.11ax) routers have more powerful processors and handle multiple connections better. They also use OFDMA technology, which allocates resources more efficiently even to older clients, although they themselves won't be able to operate at the speeds of the new standard.