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.
- August 14th, 2018
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 […]
- August 1st, 2018
Chris and I talk about PoE (power over ethernet) budgeting in this latest video.
- July 23rd, 2018
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, […]
- July 17th, 2018
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 […]
- July 9th, 2018
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 […]
- July 5th, 2018
The CSMA/CA protocol utilizes a line of defense to ensure that any Wi-Fi radio does not transmit while another is already transmitting on the same channel. The 802.11-2016 standard defines a physical carrier sense mechanism to determine if the radio frequency (RF) medium is busy. Physical carrier sense is performed constantly by all Wi-Fi radios […]
- June 27th, 2018
As many of you might already know, a key efficiency enhancement for 802.11ax will be the use of OFDMA by Wi-Fi radios. Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the OFDM digital-modulation technology and is used in other wireless technologies such as LTE. OFDMA subdivides a channel into smaller frequency allocations, called […]
- June 21st, 2018
Chris and I discuss how many devices a single access point can provide access to along with design and configuration best practices for enterprise Wi-Fi.
- June 18th, 2018
Much of the 802.11ax draft amendment has been written with Internet of Things (IoT) devices in mind. The radio chipsets used for IoT devices generally need to be low-cost and consume very little power. Traditionally, Bluetooth and Zigbee chipsets have been cheaper to manufacture for IoT devices than Wi-Fi radio radios. However, 802.11ax lays the […]
- June 12th, 2018
The term multi-user (MU) simply means that transmissions between an AP and multiple clients can occur at the same time dependent on the supported technology. However, the MU terminology can be very confusing when discussing 802.11ax. MU capabilities exist for both OFDMA and MU-MIMO. 802.11ax defines the use of two multi-user technologies, OFDMA and MU-MIMO. But please […]