A modern home network is a complex mechanism where traffic distribution This happens in a split second. When you're watching 4K video on your TV, while someone else is downloading heavy files, and a third party is playing an online shooter, the router is forced to constantly switch between these tasks. It seems like all the processes are happening simultaneously, but at the physical level, the radio channel operates sequentially, transmitting data packets at incredible speeds.
Understanding the principles of operation MAC level and scheduling algorithms allow you to configure your network so that mission-critical applications receive priority. In this article, we'll explore the technologies behind connection stability and why speeds sometimes drop even with a strong signal. The key factor here is not only the bandwidth, but also the queuing algorithm your router uses to process requests.
It's important to remember that wireless is a half-duplex communication channel. This means that a device cannot simultaneously receive and transmit data on the same frequency without special technology. That's why latency In Wi-Fi, the bandwidth is often higher than in wired Ethernet, where the transmit and receive channels are physically separated.
Physical layer: frequencies and channel width
The basis for data distribution is the selected frequency and bandwidth. Routers operate in the 2.4 GHz and 5 GHz (and now 6 GHz) bands, each with its own channelization characteristics. Channel width can be 20, 40, 80, or even 160 MHz, which directly impacts throughput.
When using a wider channel, for example 80 MHz, the router gets more "space" for simultaneous data transmission. However, this also increases the likelihood of interference with neighboring networks. In a crowded airwaves collision avoidance algorithms force devices to wait for a channel to become available, which reduces overall efficiency.
In the 2.4 GHz band, only three non-overlapping channels are available (1, 6, 11). Traffic is distributed extremely inefficiently here if neighboring access points operate on the same frequencies. Devices are forced to constantly "re-request" data if their packet is lost due to interference.
- 📡 2.4 GHz: Narrow channels, long range, but high noise levels and low data distribution speed.
- ⚡ 5 GHz: Wide channels, less interference, the ability to use MU-MIMO technologies for simultaneous operation.
- 🚀 6 GHz (Wi-Fi 6E/7): Huge channel width up to 320 MHz, minimal latency and no legacy clients.
⚠️ Attention: The router's automatic channel width selection isn't always optimal. In apartment buildings, manually setting the channel width to 20 or 40 MHz in the 2.4 GHz band often provides more stable results than the automatic "Auto 20/40" mode.
Medium Access Protocols: CSMA/CA and Queues
The fundamental principle of Wi-Fi is the protocol CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). Before transmitting data, the device "listens" to the air. If the channel is busy, it waits a random amount of time. This mechanism prevents chaos, but creates a waiting queue.
The router manages multiple traffic queues simultaneously. There are four priority categories, known as Access Categories (AC): Voice, Video, Best Effort, and Background. VoIP call traffic is placed in the highest priority queue, while torrent downloads are placed in the lowest.
If the buffer becomes full of low-priority packets, the router begins to discard them first. This phenomenon is called tail dropProperly setting up QoS (Quality of Service) allows you to manually redistribute the weight of these queues, ensuring that your gaming ping doesn't increase while downloading updates.
It's important to understand the difference between bandwidth and latency. Even if the channel is only 50% utilized, poor TXOP distribution can lead to noticeable lag in games.
Multi-user access technologies: MU-MIMO and OFDMA
For a long time, Wi-Fi operated on the principle of "one talks, all listen." The router transmitted data to only one client at a time, quickly switching between them. This created the illusion of simultaneous operation, but with a large number of devices, efficiency dropped. With the advent of the standard Wi-Fi 5 (AC) MU-MIMO technology has arrived.
MU-MIMO (Multi-User Multiple Input Multiple Output) allows the router to form directional beams and transmit data to multiple devices simultaneously. However, this only works for downlink transmission and requires support from client devices.
Standard Wi-Fi 6 (AX) revolutionary technology OFDMA (Orthogonal Frequency-Division Multiple Access). It divides a single channel into multiple small subcarriers. The router can collect small data packets from different devices (for example, an acknowledgment of packet receipt or a short request) and send them all together in a single frame.
| Technology | Operating principle | Effect on the network |
|---|---|---|
| SU-MIMO | One client at a time | High latency on many devices |
| MU-MIMO | Multiple clients at the same time (space) | Increase in overall throughput |
| OFDMA | Channel splitting into subcarriers (frequency/time) | Reduce delays and overhead costs |
The use of OFDMA is especially critical for smart homes, where dozens of sensors and light bulbs transmit tiny amounts of data. Without this technology, they would create a huge queue of service packets, slowing down the main network.
What is the difference between MU-MIMO and OFDMA?
MU-MIMO allows for the simultaneous transmission of different data streams to different users using different antennas. OFDMA allows for the division of a single communication channel into smaller parts to transmit small amounts of data to many users simultaneously, saving time on overhead.
The impact of the number of connected devices
Each connected device isn't just a traffic consumer, but also an active participant in the exchange of service packets. The router must poll each device, confirm data delivery, and maintain the connection. This creates a load on Router CPU and takes up airtime.
There's a concept called "airtime." A slow device running the older 802.11n standard takes significantly longer to transmit the same amount of data than a modern Wi-Fi 6 device. While the "slow" client transmits data, the entire network waits.
If there are many such devices on the network, the effective speed for all the others drops. The router is forced to use more reliable, but slower, signal encoding methods to "reach" the weaker client. This phenomenon is known as Rate Adaptation.
- 📉 Brake effect: One device with a poor signal can reduce the overall performance of the entire Wi-Fi cell.
- 🔄 Retransmissions: When packets are lost, the device requests them again, occupying the channel a second and third time.
- 🔋 Sleep mode: Devices in power saving mode wake up the router with their beacon frames, creating background noise.
⚠️ Attention: Router interfaces and firmware are constantly updated. The location of QoS or Airtime Fairness settings may vary depending on the firmware version. Always check the manufacturer's support section for the latest instructions for your model.
Scheduling and QoS algorithms
Complex scheduling algorithms are used to manage data flows. The most common ones are: Round Robin (cyclic switching) and Weighted Fair Queuing (Weighted Justice). The first simply gives everyone an equal amount of time, the second takes into account priorities.
Modern routers use dynamic QoS, which automatically analyzes traffic types. It recognizes Netflix, Zoom, or gaming packets and prioritizes them. However, manual configuration often yields better results, especially if you know exactly which device requires the maximum speed.
You can configure speed limits for specific MAC addresses or ports. For example, you can limit downloads on a PC to 80% of the bandwidth, leaving a 20% buffer for web surfing and VoIP on phones. This prevents Bufferbloat - buffer overflow leading to increased ping.
☑️ Setting up traffic priorities
Diagnosing speed distribution problems
If you notice uneven speed distribution, start with an airtime analysis. Professional Wi-Fi scanners (e.g., WiFi Analyzer or AirGraph) you can see what percentage of time the channel is busy and what percentage is free.
Check your router's CPU load. If the CPU is at 100%, it physically can't handle packet distribution, regardless of internet speed. This often happens when heavy-duty features like antivirus software or deep packet inspection are enabled.
Use the command line to check for packet loss. Run the command ping -t 8.8.8.8 During periods of intense network load, fluctuations in response time (jitter) or packet loss (request timed out) indicate resource allocation issues.
ping -n 50 8.8.8.8When analyzing the command output, pay attention to the maximum response time. If it deviates significantly from the average, there are delays in the router queue. In this case, disabling unnecessary features or reducing network load will help.
Why does Wi-Fi speed drop when connecting a new gadget?
Each new device contributes its share of service traffic and takes up time in the channel access queue. Furthermore, the router may switch to a more compatible (slower) operating mode to accommodate the new client, which reduces overall network efficiency.
What is Airtime Fairness and should I enable it?
Airtime Fairness is a feature that limits the amount of time a slow device can spend on the air. This prevents a single, old smartphone from slowing down the entire network. It's recommended to enable this feature in mixed networks with devices of different generations.
Does WPA3 encryption affect traffic distribution speed?
WPA3 requires more computing power to encrypt and decrypt packets. On powerful routers, this isn't noticeable, but on budget models with weak processors, enabling WPA3 can reduce the maximum traffic speed through the device.
How often does the router switch between clients?
Switching occurs thousands of times per second. The router allocates a small time slot (a few milliseconds) for data transfer to each device. Due to the high speed of this process, the human eye perceives the internet as being available on all devices simultaneously, without delay.