For an 802.11 station to send a Contention Free Burst – it needs to negotiate a Block ACK Session for whichever particular Traffic Identifier (tid) class of packets that intends to use the Block ACK mechanism. The frame that are part of the Block ACK mechanism are ADDBA Request    – ADD Block ACK Request – […]

ADDBA response frame format The Frame is shown pictorially below The Category field is set to 3 – indicating Block Ack Block Ack Action field is set to 1 – representing ADDBA Response Dialog token is the same as the non-zero value that is sent in the ADDBA request Status code – indicates whether the […]

After a Block ACK Session is negotiated between an Access Point and a WLAN station connected to the Access Point, the AP and the WLAN station can partake in a Contention Free Burst within the scope of the block ACK session. After the Frame burst is complete, the WLAN station would send a Block ACK […]

DELBA Frame format The DELBA frame is depicted below Fig Courtesy: 802.11 Standard The Category field is set to 3 – indicating Block Ack Block Ack Action field is set to 2 – representing DELBA The DELBA Parameter set contains the below The initiator subfield – indicates who is sending the DELBA frame – the […]

We will now take a look at the frame formats of the different frames that are transmitted in a Block ACK session negotiation and termination.  The Three frames that are used in the Block Ack session negotiation setup and termination are ADDBA Request frame ADDBA Response frame DELBA frame All three frames are action frames […]

To understand the Block ACK Request frame – kindly refer here — <Block ACK Request Frame>. Block Ack Frame The Block Ack frame is shown below The Duration ID is set to the time required to transmit one ACK frame + a SIFS duration The RA field incorporates the address of the recipient station which […]

WLAN devices need to conform to Regulatory domain or country requirements for Transmit power/spectral mask and channel allocation. A regulatory domain might be a country or a set of countries which might follow similar laws for channel utilization. For e.g. The EU regulatory domain is for Europe (a set of countries) The US regulatory domain […]

The Country Information element is shown below Fig Courtesy: 802.11 Standard where dot11OperatingClassesRequired is False and the First Channel Number/Operating Extension Identifier octet has a positive integer value of less than 201, then the  Country Information element is shown as below Country String – indicates the country of operation. It also indicates Indoor/Outdoor operation (e.g […]

The Country Information element is shown below Fig Courtesy 802.11-2012 standard where dot11OperatingClassesRequired is true and the First Channel Number/Operating Extension Identifier octet has a positive integer value of 201 or greater, then that triplet comprises the Operating Extension Identifier, Operating Class, and Coverage Class fields Operating Extension Identifier – indicates whether the Sub-band triplet […]

An 802.11 Station on entering a new regulatory domain will not initiate an active scan (i.e. send probe requests). It will passively listen till it receives a beacon which contains the Country Information element. On reading the Country Information element and ascertaining the country of operation – the device can later scan actively for an […]