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CWAP – 802.11 Medium Contention
DCF- Distributed Coordination Function : Non-QoS WLAN HCF with EDCA – Hybrid Coordination Function : QoS WLAN EDCA- Enhanced Distributed Channel Access PCF – Point Coordination Function (not...
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CWAP – 802.11 Data Frame Types
There are 15 different types of Data Frames defined in IEEE 802.11-2007 standard. Data frames with a value of 1 in the QoS subfield of the Subtype field (Bit7) are collectively referred to as QoS data...
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CWAP – 802.11 Power Management
A wireless radio can perform one of the 4 activities. Power consumed by each activity increases in the given order ( 1-4). 1. Asleep 2. Idle & awake 3. Receiving 4. Transmitting There are 3 methods...
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CWAP 802.11 PHY – PPDU
802.11 Physical (PHY) layer is divided into two sublayers 1. PLCP (Physical Layer Convergence Procedure) sublayer 2. PMD (Physical Medium Dependent) sublayer The PLCP prepare the frame for transmission...
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CWAP – 2.4GHz vs 5GHz
2.4GHz (2.4000 GHz to 2.4835 GHz) - 802.11 (FHSS clause 14 or DSS clause 15 radios) – 802.11b (HR-DSSS clause 18 radios) – 802.11g (ERP clause 19 radios) – 802.11n (HT clause 20 radios) In addition to...
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WLC Client Debug – Part 1
When you are troubleshooting wireless client connectivity issues there is a one command you always need to use. “debug client <client_mac_address>” output will tells you what’s going on. To...
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CWAP – Spectrum Analysis
WiFi Spectrum Analyzer considerations – Frequency – Form factor – Price – Hardware Platform – Resolution – Supporting Software – WiFi integration Free Space Path Loss(FSPL) FSPL isthe loss of signal...
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WLC Client Debug – Part 2
In this post we will see how to utilize “debug clinet x.x.x.x” output to understand the process a wireless client go through get connected to WPA2-PSK configured wireless network. Here is the basic...
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CWAP – 802.11n Introduction
802.11n-2009 (HT-Clasue 20) amendment was ratified on September 2009, essentially a list of enhancement to improve the performance & throughput of 802.11a/g standards. PHY Layer enhancements 1....
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CWAP – HT Capabilities IE
802.11n introduces 4 new information elements which can be seen in 802.11n (HT) beacon frames. HT STAs declare themselves as HT STA by transmission of HT Capabilities Element in Beacon, Probe Request,...
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CWAP – HT Control Field
The 802.11n amendment add a 4 byte HT control field to the 802.11 MAC header. With this HT Control field max MAC header length increased to 36 bytes. HT Control Field is always present in a Control...
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Free CCIEW Study Materials
I originally started my blog as a place to keep my CCIEW study notes. Since then I started blogging about the things I am learning in wifi space (though it is not related to CCIEW exam). Since I passed...
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CWAP – MAC Header : Duration/ID
Duration/ID field is 2 bytes(16bits) long field in the 802.11 MAC header. Here is the 16 bit of Duration/ID fieldIn 802.11, Duration/ID field can be used for 3 different reason 1. Virtual Carrier Sense...
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CWAP – 802.11 Ctrl : RTS/CTS
RTS (Request to Send) & CTS (Clear to Send) frames are used to enhance the virtual carrier sense process. It is possible for a client station to be able to communicate with a AP, but not able to...
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CWAP 802.11- Probe Request/Response
Discovering the network by scanning all possible channels & listening to beacons is not considered to be very efficient (passive scanning). To enhance this discovery process, stations often use...
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802.11 Mgmt : Association Req/Response
When 802.11 authentication (not the RSN-WPA/WPA2 authentication) completes, a STA move to Association phase to the BSS. The purpose of this exchange is to join the cell & obtain an Association...
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CWAP – Reassociation Req/Response
Reassociation Request frame sent only by a STA to an AP & used when the STA already associated to the ESS & want to associate to another AP connecting to the same ESS. This frame can also be...
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CWAP- Channel Switch Announcement
The Channel Switch Announcement element is used by an AP in a BSS, a STA in an IBSS, or a mesh STA in an MBSS to advertise when it is changing to a new channel and the channel number of the new...
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CWAP – 802.11 : Block Ack
The Block Ack mechanism improves channel efficiency by aggregating several acknowledgments into one frame. There are two types of Block Ack mechanisms, immediate and delayed. Immediate Block Ack is...
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NBase-T (2.5/5Gbps over Cat5e/6)
There is lot of excitement (read this) about Cisco is leading the way to come up with a new standard to deliver more than 1Gbps data rate using existing cat5e/6 cabling. NBaseT alliance (started by...
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