22 | 03 | 2018

HD Wi-Fi Scenario-Hall

A middle size hall may consists of 500 seats. Imagine 500 Wi-Fi devices connecting to the network at the same time in a relatively small space, it will be a mess. Still, we assume 70% of devices are 2.4GHz only.

Capacity - Without calculation, there is no doubt that single AP can't solve the problem. Before calculate how many AP we need, we must minimize the interference between AP  and between clients that running at the same frequency. RF propagation helps by using antennas. The idea is separate the space(seats) into different sectors and avoid frequency overlap. Also, we must use all available frequencies, include 5GHz. The density of the AP highly related to the applications running.

Applications (general purpose) - If there is no target application that the Wi-Fi is up to, we consider a average  bandwidth calculation, let's say 5Mbps for each client(2Mbps for web browsing, 10Mbps for video streaming). You need 2.5Gbps/0.7=3.5Gbps (assume at least 30% loss by noise correction) throughput:

3.5Gbps x 70%=2.45Gbps for 2.4GHz only devices, 2.45Gbps x 1024 / 90Mbps = 27 channel space. We need 14 AP if each has two radios.
3.5Gbps x 30%=1.05Gbps for 5GHz devices, 1.05Gbps x 1024 / 240Mbps= 5 channel space. We need 3 AP if each has two radios.

Applications (dedicate purpose) - If there is a special application for all clients to run at the same time, heavy as HD streaming, will require a throughput about 14Gbps. It is impossible to implement at mostly 2.4GHz device environment unless using 802.11AC. This is theoretic because 802.11AC requires higher SNR (signal noise ration) to run higher modulation rate. The RF propagation planning is so important.

14Gbps x 1024 /750Mbps = 19 channel space, 10 AP if each has two radios.

Mobility - The roaming between APs and between radios must include for balancing and maximize performance. This is more important if QoS must applied.


No. of Device Throughput@20MHz
2.4GHz 350 10Gbps 20Gbps
5.8GHz 150 40Gbps


Access Point Radio Type (802.11n) Throughput
2.4GHz 3x3 20MHz 90Mbps
5GHz 3x3 40MHz 240Mbps
5GHz 3x3 80MHz (802.11AC) 750Mbps


Channel Space 2.4GHz
20MHz 3
40MHz 1 12
80MHz (AC) 6
160MHz (AC) 2