David Coleman


David Coleman is a wireless mobility consultant, public speaker, and trainer. For the last twenty years, David has instructed IT professionals from around the globe in enterprise WLAN design, WLAN security, WLAN administration and WLAN troubleshooting. In his spare time, David writes white papers, blogs, and books about enterprise Wi-Fi networking. David is the co-author of Sybex Publishing’s Certified Wireless Network Administrator (CWNA) Study Guide and numerous other books about Wi-Fi. David is the Senior Product Evangelist for Aerohive Networks and is CWNE #4.

CWNA Study Guide – 5th Edition is Now Available!

After many months of work, the 5th edition of the Sybex Publishing Certified Wireless Network Administrator (CWNA) Study Guide is available. Writing a book is a time-consuming and often aggravating process. However, whenever the finished edition arrives at my doorstep, I always react like Steve Martin does in this movie clip. The CWNA book is a […]

How Does an 802.11ax AP Allocate OFDMA Resource Units?

In the previous blog, you learned that 802.11ax access point uses OFDMA technology to partition a channel into smaller sub-channels called resource units (RUs) so that simultaneous multiple-user transmissions can occur. The AP mandates the RU allocation of a 20 MHz for multiple clients for both downlink and uplink OFDMA. RU allocation information is communicated to […]

What are OFDMA Resource Units in 802.11ax?

In our last 802.11ax blog, we discussed how OFDMA is the main 802.11ax enhancement that offers the biggest bang for the buck. Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of OFDM digital-modulation technology. OFDMA subdivides a channel into smaller frequency allocations. By subdividing the channel, parallel transmissions of small frames to multiple clients can […]

The Main Ingredient of 802.11ax: OFDMA

In previous blogs, we have discussed many 802.11ax PHY and MAC enhancements including BSS color, spatial reuse, Multi-TID AMPDU, 20 MHz-only clients and more. However, we have not yet dedicated a lot of blog discussion about the main 802.11ax enhancement that offers the biggest bang for the buck: OFDMA. 802.11a/g/n/ac radios currently use Orthogonal Frequency […]

Will 802.11ax Make 80 MHz and 160 MHz Channels Usable in the Enterprise?

A question that I keep getting asked about 802.1­­­1ax technology is: “Will 802.11ax make 80 MHz and 160 MHz channels usable in the enterprise?” In theory, BSS color combined with the spatial reuse operation could provide the capability to take advantage of 80 MHz channels in the enterprise. However, this would be practical only if legacy […]

Dueling NAVs in 802.11ax

Wi-Fi radios use two methods of carrier sense to determine if the RF medium is busy and possibly defer transmissions. The clear channel assessment (CCA) is a physical carrier sense mechanism which works together with MAC layer virtual carrier sense. Virtual carrier sense uses a timer mechanism known as the network allocation vector (NAV). In previous […]

What is PoE (Power Over Ethernet) Budgeting?

Chris and I talk about PoE (power over ethernet) budgeting in this latest video.

How Does BSS Coloring Work in 802.11ax?

A basic service set (BSS) is the cornerstone topology of any 802.11 network. The communicating devices that make up a BSS consist of one AP radio with one or more client stations. In the last blog, we discussed how BSS color is a numerical identifier of a BSS. BSS color, also known as BSS coloring, […]

What is BSS Color in 802.11ax?

As we discussed in the last few blogs, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) dictates half-duplex communications, and it says only one radio can transmit on the same channel at any given time. An 802.11 radio will defer transmissions if it hears the PHY preamble transmissions of any other 802.11 radio. Unnecessary medium contention […]

What’s The Biggest Cause Of Co-Channel Interference?

In my last blog, What is a Clear Channel Assessment?, we discussed the difference between the signal detect (SD) threshold and the energy detect (ED) thresholds used by Wi-Fi radios to determine if the RF medium is busy. The ED threshold is used to detect any non-Wi-Fi transmissions while the SD the threshold is used to […]