I was asked in a work team meeting by one of the network engineers part of the network refresh project about the Mgig interface on the new Wave 2 AP’s and if we should upgrade the switch interface to benefit from the information provided by the vendor data sheets
The below paragraphs is my attempt to explain to him and anyone else that would listen in the meeting that yes upgrading the switch and APs is a great idea, however based on good enterprise wireless design requirements and the nature of 802.11, we would not be able to achieve the theoretical wireless throughput rate of up to 5.2Gbp as per vendors data sheet.
To even come close to achieve this theoretical wireless data rate the AP requires to be configured with dual 5GHz radios (2.6Gbps per radio), both using 160MHz wide channels, and ideal RF conditions (RSSI greater the -48dBm and a Signal to noise ratio of above 40dB).
The major problem with this theoretical data rate is the channel width. In the 5GHz band we only have 25 20MHz wide non overlapping channels to play with (when using DFS Channels), If we where to utilise 160Mhz wide it only leaves us with 2.
Wireless is half duplex and given the mechanisms that an 802.11 device use to determine if the medium is free before sending traffic, having only 2 channels makes avoiding interference issue impossible. Client devices operating in a noise environment reduces the aggregate wireless throughput, due to the excess amount management traffic caused by corrupted frames being retransmitted ( more management traffic equals less data traffic).
When we design Enterprise wireless networks, a major design consideration is how to best design based on the RF spectrum available, frequency reuse, amount/type of client devices and data SLA, with these requirements identified we can determine the number of APs, placement and channel plan in order to avoid or reduce wireless issues such’s as co-channel, adjacent channel and overlapping basic service set interference.
Below are some other reason why 160MHz wide via it not viable and won’t get the benefits of that Mgig interface in Enterprise Wireless deployment.
– Currently no client devices support 160MHz wide channels
– No normal wireless client device requires that amount of data throughput
– Wireless Management and control traffic is sent a legacy data rates
– Wireless is half duplex
– TCP/IP overhead
– Dual 5GHz AP deployments won’t work due to continued support for 2.4GHz clients.
– When using the other radio as a 2.4GHz radio with a max 20MHz wide channel it has a data rate of 288.9Mbps
– Recommendations by a vendor for a dual 5GHz AP is 100Mhz spacing between channels, cannot use dual 160MHz wide channels are not able to be deployed.
– Unrealistic RSSI and SNR values to achieve the MCS9 VHT Data rates
– Multi-user multiple in multiple out (mu-mimo) but device need to capable and its only on the downlink.