Review aggregate throughput for Wi-Fi networks
If your users use an Apple device in class or at work, each user uses bandwidth from your Wi-Fi network, so your Wi-Fi network must be configured properly to support the device.
802.11 is a shared medium and is limited by other devices connected to your wireless network. Therefore it’s important to look at the aggregate throughput.
Device throughput to the internet depends on the following:
Device connection rate to the access points
Bandwidth you have from your internet service provider
Number of devices using the same channel
Interference (radio, physical, electrical) and the distance from client device to the access point are two major factors that affect observed maximum throughput. The half-duplex nature of wireless, combined with other TCP/IP overhead, also means the actual aggregate throughput is typically 65 per cent or less of the data rate.
The chapter describes how to understand expected Wi-Fi usage based on a way to calculate the maximum number of devices that can be used simultaneously in a classroom.
Considerations
Consider these factors when preparing your network for Apple devices:
Physical dimensions of the classroom or work area
Number of users
Number of access points per classroom or work area
Access point and antenna configuration
Channel and co-channel interference
Network security method
Backbone speed from your organisation to the internet
App throughput requirements
Wall material (how well radio frequency propagates, reflects or refracts has an appreciable impact on Wi-Fi signal)
Radio-frequency-emitting items in and around the area (sources of destructive interference could have a large impact on the quality and consistency of Wi-Fi signal in a given space)
Initial network assumptions
The table below contains initial network assumptions. Your network may have different values.
Assumption | Value | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
MAC efficiency (802.11a/b/g/n - no aggregation) | 0.45 | ||||||||||
MAC efficiency (802.11n/ac aggregation) | 0.65 | ||||||||||
Maximum clients per access point | 50 | ||||||||||
Available channel capacity (per cent) | 80 A typical available channel capacity is about 80%. | ||||||||||
ISP/WAN speed (Mbps) | 100 | ||||||||||
App usage values
The following are typical throughput values from three main categories; browsing, streaming and backup of audio-visual data from an Apple device to the cloud.
App usage per device | Minimum throughput requirement (Mbps) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Browsing For example, browsing the internet | 1 | ||||||||||
Streaming For example, streaming a video | 4 | ||||||||||
A/V backup (~2 GB in 5 minutes) For example, copying a large file to iCloud Drive | 6 | ||||||||||
Usage calculations
Below is a sample guideline calculation. This isn’t a replacement for an actual Wi-Fi site survey to deploy the network properly. The browsing, streaming and A/V backup columns show the possible number of simultaneous devices.
This formula calculates the maximum number of clients per access point for three categories of Wi-Fi categories: browsing, streaming and backups. The basic calculation is the total available throughput divided by the minimum throughput requirement for each category. Total available throughput is limited either by the data rate of the Wi-Fi being used or by the ISP/WAN speed, whichever is slowest. Depending on the category, the maximum number of clients per access point, as entered in the assumptions, could be achieved.
Important: Performance may vary due to the network configuration and the radio frequency environment.
Wi-Fi access point configuration | Maximum physical data rate (Mbps) | Aggregate data rate (Mbps) | Browsing (max. number of devices) | Streaming (max. number of devices) | A/V backup (max. number of devices) |
|---|---|---|---|---|---|
802.11a/g | 54 | 19 | 19 | 4 | 3 |
802.11n 1 spatial stream 20 MHz | 72 | 25 | 25 | 6 | 4 |
802.11n 1 spatial stream 40 MHz | 150 | 54 | 50 | 19 | 13 |
802.11n 2 spatial streams 20 MHz | 144 | 51 | 50 | 18 | 12 |
802.11n 2 spatial streams 40 MHz | 300 | 108 | 50 | 25 | 16 |
802.11ac 1 spatial stream 40 MHz | 200 | 72 | 50 | 25 | 16 |
802.11ac 2 spatial streams 40 MHz | 400 | 144 | 50 | 25 | 16 |
802.11ac 1 spatial stream 80 MHz | 433 | 155 | 50 | 25 | 16 |
802.11ac 2 spatial streams 80 MHz | 867 | 312 | 50 | 25 | 16 |