Some portions of the 5 GHz WLAN band is used by Radar, Weather satellites and other sensitive applications. The regulatory authorities of different countries determine on how transmission is to be attempted on these channel by WLAN devices. If transmission of any sensitive application is detected, the WLAN device should not attempt further transmission on […]

The current article tries to elaborate on how the Access Point notifies client stations on the presence of radar and the steps it employs to detect radar An access Point will periodically quiet the entire BSS to scan for radar. This is achieved by transmitting the quiet element in the beacon The quiet element can […]

The Extended channel switch element is used when dot11ExtendedChannelSwitchActivated is true. The Extended channel switch element can be transmitted in an Extended Channel switch announcement frame by the Access point or in a beacon. In addition to the regular Channel switch announcement Element parameters, the extended channel switch announcement element provides the operating class of […]

Radar signals can broadly be classified as Pulse signal Chirp signal Frequency-hopping signal The FCC/ETSI/JP and other regulatory bodies define their own version of the above signals. Below is given an overview of FCC signals and their widths and also provide minimum percentage number of successful detection of the radar signal for the FCC to […]

As seen in the Previous article — <Radar Signals and it’s signatures>, The different radar signals have a repetition rate. The number of successful detection is based on the 802.11 PHY layer detecting the signal (such as a pulse/chirp/frequency-hopping radar signal) and providing the input to the upper layer driver (via a phy error – […]

802.11n introduced channel bonding. An 802.11n station/AP will indicate the support for 40 MHz operation in the HT capabilities Information element. The information element and the particular bit that indicates 40 MHz support is shown below  Fig Courtesy: 802.11 standard The Wireless Capture below shows the Supported channel width setting The Access point in the […]

The 802.11ac wireless LAN standard provided additional channel bonding capabilities for 80 MHz/160 MHz and a split mode 80+80 MHz. The channel bonding capabilities build upon the channel bonding capabilities of 802.11n. The HT capability/Operation elements provided the primary channel information and the secondary channel information in the case of 40 MHz channel bonding as […]

If Multiple Mac Protocol Data units are aggregated to form one frame – then the aggregation is termed as A-MPDU aggregation. The A-MPDU aggregation is depicted pictorially below Fig Courtesy: 802.11-2012TM Standard As defined in the standard – the MPDU delimiter is used as below The purpose of the MPDU delimiter is to locate the […]

If the frame aggregation is carried out prior to MAC layer encapsulation – then the aggregation is termed as Aggregated MAC Service Data Unit (A-MSDU). The A-MSDU frame format is provided below Fig Courtesy: 802.11-2012TM Standard As is seen from the figure, each A-MSDU sub-frame consists of a Destination Address (DA), Source Address (SA), Length […]

The WLAN standard body defined how the channel centre frequency would be computed and provided formulae to compute the centre frequency for various channel bonding operations. The below tabular column and examples from the 802.11ac standard depict this operation. For a more detailed explanation – refer channelization section (22.3.14 Channelization) in the 802.11ac standard. Fig […]