What Is Channel Utilization?
Channel utilization is the percentage of time a channel is occupied over the total time in a measurement period. It is an important metric for measuring Wi-Fi network performance.
How Is Channel Utilization Calculated?
Channel utilization is calculated using the following formula:
Channel utilization on a wireless local area network (WLAN) is usually detected by the hardware of access points (APs). In this formula, the channel busy time is the total duration in which an AP detects signals on a channel. It includes not only the time for the AP to send and receive valid signals, but also the transmission time for interference signals in the environment. This means an increased volume of services or signal interference will increase channel utilization.
Is Higher Channel Utilization Indicative of Better Performance?
Channel utilization is not a "higher-is-better" metric. It can be evaluated based on user experience or resource allocation.
From the perspective of user experience, when channel utilization is lower than 60%, users can enjoy a good Internet access experience in the majority of cases. An increase of channel utilization implies that the channel becomes busier where data needs to be queued for processing. This may cause network congestion and increase the latency. Therefore, lower channel utilization can ensure a better user experience.
From the perspective of resource allocation, low channel utilization implies that there is an insufficient use of channel resources. As a result, network performance is underutilized, wasting network construction costs.
Therefore, channel utilization is a metric that network construction and maintenance engineers need to monitor, so that they can properly allocate network resources to meet actual service requirements.
How Can I Handle the High Channel Utilization Issue?
Network administrators can take different network optimization measures to handle the high channel utilization issue based on its root causes.
Measure 1: Configuring Dynamic Rate Limiting
STAs on a WLAN contend with each other for bandwidth resources. If there are a large number of STAs with high-volume traffic of services, network congestion may easily occur on the air interface. For example, downloading or uploading large files on a STA will occupy excessive bandwidth resources, which may affect network access of other STAs. Dynamic rate limiting can be configured to prevent this issue.
With dynamic rate limiting enabled, a device determines whether to rate limit service traffic of STAs based on the congestion status of the air interface, improving network experience of STAs. Specifically, the device implements the dynamic rate limiting function by calculating channel utilization at an interval of 2 seconds. If channel utilization exceeds 80% for five consecutive intervals (10 seconds), the device determines that congestion occurred and enables rate limiting. If channel utilization is lower than 70% for 30 consecutive intervals (1 minute), the device determines no congestion on the air interface and disables rate limiting.
Measure 2: Checking for Signal Interference
The air interface environment is prone to external interference, which severely affects user experience. Such interference predominately includes Wi-Fi interference and non-Wi-Fi interference. Wi-Fi interference includes co-channel and adjacent-channel interference between APs and interference from other Wi-Fi networks. Non-Wi-Fi interference is mainly caused by devices such as microwave ovens, Bluetooth devices, wireless audio and video devices, baby monitors, wireless cameras, infrared sensors, and cordless phones.
During fault locating, if an AP with a small traffic volume has high channel utilization (> 60%), the air interface interference is severe. In this case, network administrators need to properly plan AP channels to reduce interference, for example, by manually switching the AP to a channel with low channel utilization, or performing radio calibration that will not affect services.
Measure 3: Checking Whether Multicast or Broadcast Packets Are Flooded to the Air Interface
No retransmission mechanism is available for multicast and broadcast packets on a WLAN. Therefore, these packets are sent at low rates so that they can successfully reach the receiver. However, if a large number of multicast or broadcast packets are sent to the air interface, air interface resources will be wasted and channel utilization will keep increasing. This can cause long delays and packet loss, affecting user experience.
During fault locating, if the interference rate is low, the high channel utilization issue is caused by the local AP. In this case, it is recommended that network administrators check the increase rates of multicast and broadcast packets received on the AP. If the increase rate of broadcast or multicast packets exceeds 100 pps, the air interface has received a large number of broadcast or multicast packets. In this case, network administrators can enable Layer 2 network isolation on the upper-layer switch or AC, or enable rate limiting for broadcast and multicast packets.
- Author: Liu Jiayu
- Updated on: 2024-08-01
- Views: 2285
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