There are some network devices such as SpectraLink NetLink phones requires long preambles. In such cases, unchecking short preamble enables long preamble to achieve interoperability with Spectralink Netlink phones and other network devices that supports long preamble.
In the Instant 184.108.40.206-220.127.116.11 release, the IAP CLI allows you to enable or disable the transmission and reception of short preamble frames. By default, short preamble frames are enabled for all WLAN SSID clients, The wlan ssid-profile command now includes short-preamble-disable command to disable short preamble frames. The function only takes effect on 2.4G band and configuration only supports on wlan-ssid-profile.
•Disable short preamble (will start using long preamble)
IAP (config) # wlan ssid-profile test IAP (SSID Profile "test") # short-preamble-disable
•Enable short preamble
IAP (config) # wlan ssid-profile test IAP (SSID Profile "test") # no short-preamble-disable
WLAN administration can look-up running configuration to understand if short preamble is disabled or not. By default it is enabled.
IAP#show running-config | begin "wlan ssid-profile" wlan ssid-profile test enable index3 essid test opmode opensystem short-preamble-disable ⇒ Currently short preamble is disabled in the SSID profile called test.
Same can be verified from OTA captures as shown below,
- Bit is set to 0, when short preamble is disabled.
- Bit is set to 1, when short preamble is enabled.