David Coleman

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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.

Uplink Orthogonal Division Multiple Access (UL-OFDMA) in 802.11ax

As we discussed in a previous blog, an 802.11ax AP must contend for the medium and win a transmit opportunity (TXOP) before multi-user (MU) communications can occur. Once the 802.11ax AP wins a TXOP, it can then coordinate uplink transmissions from 802.11ax clients that support UL-OFDMA. UL-OFDMA is more complex than DL-OFDMA and may require the […]

Uplink OFDMA is not PCF

In the previous blog, we discussed DL-OFDMA and the 802.11 frame exchanges between an 802.11ax AP and multiple 802.11ax clients for multi-user downlink transmissions. In future blogs, we will discuss the necessary UL-OFDMA frame exchanges to achieve synchronized multi-user uplink transmissions. However, there is already some confusion between UL-OFDMA and some legacy RF medium access methods. […]

How Does DL-OFDMA Work in 802.11ax?

You should always remember that multi-user OFDMA communication is only for 802.11 data frame exchanges between an 802.11ax AP and multiple 802.11ax clients. For backward compatibility, management and control frames will still be sent using single-user OFDM. In a previous blog, we mentioned that a series of frame exchanges are used for both DL-OFDMA and […]

What are Cloud Configuration Groups used for?

In an earlier blog, we announced Cloud Configuration Groups, a new HiveManager configuration and network device management feature. Cloud Config Groups is a new form of device classification that adds more flexibility when configuring network policies with HiveManager. Cloud Config Groups solves the management challenge of implementing template-based network policies for network devices that require […]

What are OFDMA Trigger Frames?

In previous blogs, you have learned that an 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. When referencing downlink and uplink OFDMA […]

OFDM and OFDMA Subcarriers – What Are the Differences?

As we continue our 802.11ax blog series, let’s discuss both OFDM and OFDMA technologies used for Wi-Fi communications. 802.11a/g/n/ac radios currently use Orthogonal Frequency Division Multiplexing (OFDM) for single-user transmissions on an 802.11 frequency. 802.11ax radios can utilize Orthogonal frequency-division multiple access (OFDMA) which is a multi-user version of the OFDM digital-modulation technology. OFDMA subdivides a channel […]

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 […]