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 […]

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 […]

Cloud-Managed Branch Routing: Policy-Driven WANs

“Our Tokyo branch just went dark…” “Did you make a configuration change?” “I just updated the router with the same configuration as our Frankfurt office.” Router(config)#help To say enforcing a consistent network and security policy across a multi-branch WAN with traditional routing technologies is a challenge would be an understatement. It’s very easy to mistype […]

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 […]

What Benefits Does Dual 5 GHz Bring To 802.11ax?

Last week we discussed the 4×4:4 vs 8×8:8 debate with 802.11ax. This week I want to wrap up that debate and also highlight the benefits of dual 5 GHz support in 802.11ax APs. The Aerohive 802.11ax chipset provides for a 2.4 GHz (4×4:4) radio and a 5 GHz (4×4:4) radio. However, one of the radios […]

Does The Number of Spatial Streams in 802.11ax Really Matter?

802.11ax has arrived, and with that, you will see many vendors announcing their 802.11ax access points in the coming months. We have discussed numerous capabilities of 802.11ax on this blog, however, there is one question that has come up recently. What is the difference between a 4×4:4 AP and an 8×8:8 AP? Which do I […]

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.