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802.11ax

Aerohive Special Edition

by David Coleman – CWNE #4

and Lawrence C. Miller

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802.11ax For Dummies®, Aerohive Special Edition

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Table of Contents

INTRODUCTION ............................................................................................... 1

About This Book ................................................................................... 1

Foolish Assumptions ............................................................................ 2

Icons Used in This Book ....................................................................... 2

Beyond the Book .................................................................................. 3

Where to Go from Here ....................................................................... 3

CHAPTER 1: Recognizing the Business Need for

Better Wi-Fi ....................................................................................... 5

Current Wi-Fi Challenges ..................................................................... 5

The 802.11ax Vision — More than Just Speeds and Feeds ............. 7

Wi-Fi Use Cases ..................................................................................... 9

CHAPTER 2: Understanding Key 802.11ax Technologies .......... 11

Multi-User (MU) Defined .................................................................... 11

MU-OFDMA ......................................................................................... 12

Subcarriers ..................................................................................... 13

Resource units (RUs) ..................................................................... 14

MU-MIMO ............................................................................................ 16

Spatial Reuse (BSS Coloring) ............................................................. 18

CHAPTER 3: Looking at Other 802.11ax Enhancements

and Design Considerations ................................................23

Target Wake Time (TWT) .................................................................... 23

1024-QAM............................................................................................ 24

New PHY Headers .............................................................................. 25

Design Considerations ....................................................................... 27

CHAPTER 4: Exploring the Aerohive 802.11ax Family ................. 29

AP630 ................................................................................................... 29

AP650 and AP650X ............................................................................. 30

CHAPTER 5: Ten Things You Need to Know

about 802.11ax .............................................................................33

GLOSSARY ..........................................................................................................37

Table of Contents iii

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iv 802.11ax For Dummies, Aerohive Special Edition These materials are © 2018 John Wiley & Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited.

Introduction

802.11ax is the next fast-approaching Institute of Electrical

and Electronics Engineers (IEEE) standard that addresses

today’s biggest Wi-Fi challenges: high density and perfor-

mance. It addresses those challenges by increasing capacity by up

to four times and improving spectral efficiency to benefit both

2.4 gigahertz (GHz) and 5 GHz bands in a variety of environments.

802.11ax will handle client density more efficiently through a new

channel-sharing capability, improve battery life using negoti-

ated wake-time scheduling between APs and clients to preserve

energy, and deliver efficiency improvements with at least four

times more throughput than 802.11ac.

In this book, you learn about the imminently approaching

802.11ax standard, the key enabling technologies and enhance-

ments in the standard, and Aerohive’s family of 802.11ax access

point solutions.

About This Book

802.11ax For Dummies, Aerohive Special Edition, consists of five chapters that explore:

» The business need for better Wi-Fi and the 802.11ax vision

(Chapter 1)

» Key enabling technologies in 802.11ax (Chapter 2)

» Additional enhancements and design considerations in

802.11ax (Chapter 3)

» The Aerohive family of 802.11ax access points (Chapter 4)

» Ten key things to remember about the new 802.11ax

standard (Chapter 5)

There’s also a convenient glossary at the end of the book in case

you get stuck on any technical terms or acronyms.

Introduction 1

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Foolish Assumptions

It’s been said that most assumptions have outlived their useless-

ness, but we assume a few things nonetheless!

Mainly, we assume that you’re an IT infrastructure professional —

someone with networking, wireless, or cloud in their title — and

that you work for a medium to large organization or enterprise

with robust Wi-Fi business requirements and you’re interested in

what’s next for Wi-Fi.

If any of these assumptions describe you, then this book is for

you! If none of these assumptions describe you, keep reading

anyway. It’s a great book and when you finish reading it, you’ll

know a few things about the next generation of Wi-Fi.

Icons Used in This Book

Throughout this book, we occasionally use special icons to call

attention to important information. Here’s what to expect:

This icon points out information you should commit to your non-

volatile memory, your gray matter, or your noggin — along with

anniversaries and birthdays!

You won’t find a map of the human genome here, but if you seek

to attain the seventh level of NERD-vana, perk up! This icon

explains the jargon beneath the jargon!

Tips are appreciated, never expected — and we sure hope you’ll

appreciate these tips. This icon points out useful nuggets of

information.

These alerts point out the stuff your mother warned you about

(well, probably not), but they do offer practical advice to help you

avoid potentially costly or frustrating mistakes.

2 802.11ax For Dummies, Aerohive Special Edition

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Beyond the Book

There’s only so much we can cover in 48 short pages, so if you

find yourself at the end of this book, thinking, “Where can I

learn more?” just go to www.11ax4dummies.com. You can also read the latest edition of David Coleman and David Westcott’s

CWNA Certified Wireless Network Administrator Study Guide: Exam CWNA-107 (Wiley). You can also download a free 802.11ax poster at

www.aerohive.com/wp-content/uploads/Aerohive_802.11ax_

Poster.pdf.

Where to Go from Here

If you don’t know where you’re going, any chapter will get you

there — but Chapter 1 might be a good place to start! However,

if you see a particular topic that piques your interest, feel free to

jump ahead to that chapter. Each chapter is written to stand on its

own, so you can read this book in any order that suits you (though

we don’t recommend upside down or backwards).

Introduction 3

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4 802.11ax For Dummies, Aerohive Special Edition These materials are © 2018 John Wiley & Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited.

IN THIS CHAPTER

» Understanding current Wi-Fi network

challenges

» Looking ahead to the next Wi-Fi standard

» Considering current and future Wi-Fi use

cases

Chapter 1

Recognizing the Business

Need for Better Wi-Fi

In this chapter, you look back at the evolution of Wi-Fi stan-

dards and the challenges that exist in current Wi-Fi networks,

as well as the next Wi-Fi standard — 802.11ax — and Wi-Fi use

cases.

Current Wi-Fi Challenges

Since the commercial release of the original 802.11 wireless net-

working standard over two decades ago, Wi-Fi has evolved with

each new protocol theoretically achieving successively higher

peak speeds (see the sidebar “Leading up to 802.11ax: a brief

Wi-Fi history and amendment timeline”).

However, in the real world, the problem isn’t how fast Wi-Fi can

go, but whether the Wi-Fi network has enough capacity to handle

the expanding population of client devices as well as numerous

users with diverse networking needs. A Wi-Fi network needs to be

designed to address the growing demand for the high volume and

diversity of connected devices and services and measured based

on the user experience.

CHAPTER 1 Recognizing the Business Need for Better Wi-Fi 5

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LEADING UP TO 802.11ax:

A BRIEF WI-FI HISTORY AND

AMENDMENT TIMELINE

Delivering a quality Wi-Fi experience can often seem like a complex,

ongoing journey through changing standards and emerging

technologies, and the continued promise that the next standard

will be “the one.”

In 1999, wireless was commercially introduced as a “nice to have” with

the 802.11a and 802.11b ratifications. 802.11b, the most commonly

used standard at the time, had very low speeds — only up to 11 Mbps

(much lower than most Ethernet wired networks installed at the

time) — but there were no Wi-Fi mobile devices and very few laptops,

so 11 Mbps was more than enough.

By 2003, Wi-Fi-enabled mobile devices were being introduced in the

market and portable laptops were becoming more standard for both

business and personal use. The 802.11g standard was subsequently

ratified, delivering up to 54 Mbps speeds.

In 2007, Apple introduced the first iPhone and the smartphone

became a modern reality. The 802.11n standard followed in 2009,

delivering 100 Mbps of usable throughput. The 802.11n standard also

brought about faster theoretical data rates of up to 600 Mbps and

supported both 2.4 and 5 GHz devices.

Today, mobile devices are robust enough to replace more expensive

laptops, so Wi-Fi has had to catch up. Introduced in 2013, 802.11ac

brings us into the age of gigabit Wi-Fi. 802.11ac delivers peak data

rates between 433 and 2167 Mbps.

New advances in the basic technologies that underpin Wi-Fi are now

being integrated into the 802.11ax standard, which seeks to reach yet

another milestone: 10 Gbps — or 5,000 to 10,000 times the perfor-

mance of the original Wi-Fi standard! However, 802.11ax is not just focused on speed but is instead focused on efficiency.

The 802.11n and 802.11ac standards introduced some great new

technology, including physical (PHY) and medium access control

(MAC) layer enhancements, that helped achieve higher data rates.

In essence, bigger highways and faster cars were built. But it led

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to a few challenges. The issues facing next generation Wi-Fi systems involve degradation to system efficiency due to a growing

density of Wi-Fi clients and network traffic with lots of small data

frames, such as Voice over Wi-Fi (VoWiFi).

With an ever-growing number of devices using Wi-Fi, along with

the emergence of the Internet of Things (IoT), Wi-Fi networks

need to do a better job of managing today’s wireless environ-

ments, increased data traffic, and a diverse mix of applications and services with differing quality of service (QoS) requirements.

The 802.11ax Vision — More than

Just Speeds and Feeds

The next Wi-Fi standard, 802.11ax, is fast approaching — and it’s

not just about faster Wi-Fi speeds. 802.11ax will bring about a sea change of performance improvements compared to previous

802.11 enhancements. Even the title of the 802.11ax amendment —

“High Efficiency” — hints at its many improvements. Previous

802.11 amendments were identified as “High Throughput.”

The changes in the 802.11ax standard will improve the way

Wi-Fi networks work by leveraging technology that substantially

improves capacity, provides better coverage, and even reduces

congestion, resulting in a far better user experience overall. It’s

Wi-Fi for the real world.

The 802.11ax standard and specifications were originally designed

to improve Wi-Fi for dense usage scenarios; however, all wireless

environments can benefit from 802.11ax enhancements. 802.11ax

offers the ability for dozens of devices to simultaneously communicate with each access point radio. Using proven Wi-Fi techniques

and innovations from the cellular world, the 802.11ax standard

is designed to increase capacity by up to four times, mostly by

improving spectral efficiency. This will provide benefits in both

the 2.4 GHz and 5 GHz bands in a variety of environments includ-

ing enterprises, schools, retail businesses, hotspots, airports, and

even the home.

CHAPTER 1 Recognizing the Business Need for Better Wi-Fi 7

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The goals of the Institute of Electrical and Electronics Engineers (IEEE) 802.11ax task group include:

» Enhancing operation in the 2.4 GHz and 5 GHz band

» Increasing average throughput per station by at least four

times in dense deployment scenarios

» Enhancing in both indoor and outdoor environments

» Maintaining or improving power efficiency in stations

» Improving the efficiency of traffic management in a variety of

environments

802.11ax focuses on nine main components of enhancement:

» Orthogonal frequency-division multiple access (OFDMA)

uplink and downlink (UL/DL) (discussed in Chapter 2)

» Longer orthogonal frequency-domain multiplexing (OFDM)

symbol (discussed in Chapter 2)

» Multi-user multiple-input multiple-output (MU-MIMO) 8×8

and UL/DL (discussed in Chapter 2)

» Spatial reuse, also referred to as BSS Coloring (discussed in

Chapter 2)

» Target Wake Time (TWT) — power saving (discussed in

Chapter 3)

» 1024 quadrature amplitude modulation (1024-QAM)

(discussed in Chapter 3)

» New PHY headers (discussed in Chapter 3)

» Enhanced outdoor robustness (discussed in Chapter 3)

» 5 GHz and 2.4 GHz support (discussed in Chapter 3)

See Table 1-1 for a comparison of 802.11ax to the two previous 802.11 standards.

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TABLE 1-1 802.11ax, 802.11ac, and 802.11n comparison

802.11n

802.11ac

802.11ax

Channel Size

20, 40

20, 40, 80, 80 +

20, 40, 80, 80 +

(megahertz, MHz)

80, and 160

80, and 160

Subcarrier

312.5

312.5

78.125

(kilohertz, KHz)

Symbol Time

3.2

3.2

12.8

(microsecond, µs)

Modulation

Binary Phase-Shift

BPSK, QPSK,

BPSK, QPSK,

Keying (BPSK),

16-QAM, 64-QAM,

16-QAM,

Quadrature Phase-

256-QAM

64-QAM,

Shift Keying (QPSK),

256-QAM,

16-QAM, 64-QAM

1024-QAM

MU-MIMO

N/A

DL

DL and UL

OFDMA

N/A

N/A

DL and UL

Wi-Fi Use Cases

The primary Wi-Fi use case for early 802.11ax standard develop-

ment was for high-density network environments, such as large

public venues. However, high density doesn’t just mean hundreds

or thousands of Wi-Fi-connected devices in a stadium or large

venue. If you need to guarantee an acceptable level of service to all

users on your enterprise Wi-Fi network, twenty or more devices

is high density.

Today’s enterprises are challenged to deal with corporate-owned

wireless devices, employee devices, guest devices, wireless secu-

rity cameras, environmental sensors, and more. These challenges

will become even more complex as IoT has the potential to pro-

vide wireless access for almost everything.

Even within a private home, a family has numerous Wi-Fi devices

including voice-activated smart speakers, laptops, tablets, smart-

phones, and so on. With all these connected devices, your home

can quickly become a Wi-Fi hive of activity!

CHAPTER 1 Recognizing the Business Need for Better Wi-Fi 9

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In addition to the immense growth of client devices, the ever-increasing volume of streaming video is another key use case for

newer Wi-Fi technologies. The Ericsson Mobility Report predicts that worldwide mobile video traffic (currently 14 exabytes per

month) will grow approximately 50 percent annually (to 110 exa-

bytes per month) through 2023, accounting for 75 percent of all

mobile data traffic. The report indicates that mobile users offload

approximately 65 to 95 percent of their mobile traffic to Wi-Fi,

when available. To remain a viable user alternative to cellular

networks, Wi-Fi standards must maintain parity with the rapidly

evolving 5G cellular standard.

Plus, where video traffic was primarily seen as only as wireless

downlink traffic, social network streaming is now generating

enormous uplink traffic loads.

In addition to dealing with video’s large data objects, streaming

video is time-bounded, meaning that latency must be kept low.

Delays in transmission due to network congestion or retransmis-

sions required by problems with prevailing radio conditions can

result in the dreaded “buffering” message, or worse. To be fair,

most high-definition (HD) video traffic only requires between

2 and 20 Mbps, because video can be highly compressed dur-

ing transmission. 4K video represents, of course, a bigger chal-

lenge: Ultra HD Blu-Ray runs at about 82 to 128 Mbps but is still

well within the copious bandwidth provisioned by even low-end

802.11ac. With gigabits of performance instantaneously avail-

able on each Wi-Fi channel and with HD video becoming more

common (or even required in most organizational settings), the

biggest challenge will be handling the growth of the WLAN. The

number of users, devices, and applications will drive the need

for as much throughput and efficiency as possible to address the

aggregate demand.

Finally, according to a report published by PRNewswire.com,

2.4 GHz devices are expected to represent the largest market seg-

ment in wireless mesh networks through 2022. Because 802.11ac

does not support the 2.4 GHz band, a new Wi-Fi standard is

needed to support the expected growth of 2.4 GHz devices, as well

as to provide backward compatibility with 802.11n and older Wi-Fi

devices.

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IN THIS CHAPTER

» Enabling simultaneous communication

with multiple Wi-Fi clients

» Using multi-user OFDMA for high

efficiency

» Making MU-MIMO a reality in 802.11ax

» Addressing OBSS challenges

Chapter 2

Understanding Key

802.11ax Technologies

In this chapter, you learn about three key enabling technologies

in 802.11ax: MU-OFDMA, MU-MIMO, and spatial reuse (basic

service set [BSS] coloring).

Multi-User (MU) Defined

Multi-user (MU) applies to multiple technologies in 802.11ax, so

it’s important to understand that the term multi-user does not

reference a specific technology. Multi-user (MU) means that

transmissions between an access point (AP) and multiple Wi-Fi

clients can occur simultaneously, depending on the supported

technology.

802.11ax defines the use of multi-user orthogonal frequency

division multiple access (MU-OFDMA) and multi-user multiple-

input multiple-output (MU-MIMO) technologies.

CHAPTER 2 Understanding Key 802.11ax Technologies 11

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MU-OFDMA

Orthogonal frequency division multiple access (OFDMA) is arguably the most important new capability in 802.11ax, allowing multiple

users with varying bandwidth needs to be served simultaneously.

OFDMA is a multi-user version of the orthogonal frequency divi-

sion multiplexing (OFDM) digital modulation technology cur-

rently used for single-user transmissions in 802.11a/g/n/ac radios.

For backward compatibility, 802.11ax radios also support OFDM.

OFDMA subdivides a Wi-Fi channel into smaller frequency allo-

cations, called resource units (RUs), thereby enabling an access

point (AP) to synchronize communication (uplink and downlink)

with multiple individual clients assigned to specific RUs. By sub-

dividing the channel, small frames (such as streaming video) can

be simultaneously transmitted to multiple users in parallel (see

Figure 2-1). The simultaneous transmission cuts down on exces-

sive overhead at the medium access control (MAC) sublayer, as

well as medium contention overhead. The AP can allocate the

whole channel to a single user or partition it to serve multiple

users simultaneously, based on client traffic needs.

FIGURE 2-1: OFDMA — Orthogonal Frequency Division Multiple Access.

OFDMA is ideal for most network applications and results in bet-

ter frequency reuse, reduced latency, and increased efficiency.

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Subcarriers

OFDM divides a channel into subcarriers through a mathematical

function known as an Inverse Fast Fourier Transform (IFFT). The

spacing of the subcarriers is orthogonal, so they don’t interfere

with one another despite the lack of guard bands between them.

This creates signal nulls in the adjacent subcarrier frequencies

and prevents intercarrier interference (ICI).

An OFDM 20 MHz 802.11n/ac channel consists of 64 312.5 kHz

subcarriers. 802.11ax introduces a longer OFDM symbol time of

12.8 microseconds, which is four times the legacy symbol time of

3.2 microseconds. As a result of the longer symbol time, the sub-

carrier size and spacing decreases from 312.5 kHz to 78.125 kHz

(see Figure 2-2). The narrower subcarrier spacing allows better

equalization and enhanced channel robustness. Because of the

78.125 kHz spacing, an OFDMA 20 MHz channel consists of a total

of 256 subcarriers.

FIGURE 2-2: OFDM and OFDMA subcarriers.

There are three types of subcarriers for 802.11ax:

» Data subcarriers: These subcarriers will use the same

modulation and coding schemes (MCSs) as 802.11ac as well

as two new MCSs with the addition of 1024 quadrature

amplitude modulation (1024-QAM).

CHAPTER 2 Understanding Key 802.11ax Technologies 13

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» Pilot subcarriers: These subcarriers are used for synchroni-

zation between the transmitter and receiver and don’t carry

any modulated data.

» Unused subcarriers: The remaining unused subcarriers are

mainly used as guard carriers or null subcarriers against

interference from adjacent channels or subchannels.

Resource units (RUs)

When an 802.11n/ac AP transmits to 802.11n/ac clients on an OFDM

channel, the entire frequency space of the channel is used for each

independent downlink transmission. When using a 20 MHz OFDM

channel, all subcarriers are used for each independent transmis-

sion. In other words, the entire 20 MHz channel is needed for

the communication between the AP and a single OFDM client.

The same holds true for any uplink transmission from a single

802.11n/ac client to the 802.11n/ac AP. The entire 20 MHz OFDM

channel is needed for the client transmission to the AP.

As shown in Figure 2-3, an OFDMA channel consists of a total of

256 subcarriers. These subcarriers can be grouped into smaller

subchannels know as resource units (RUs). When subdividing a

20 MHz channel, an 802.11ax AP can designate 26, 52, 106, and

242 subcarrier RUs, which roughly equates to 2 MHz, 4 MHz,

8 MHz, and 20 MHz channels, respectively.

FIGURE 2-3: OFDMA Resource Units – 20 MHz channel.

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The 802.11ax AP dictates how many RUs are used within a 20 MHz channel and different combinations can be used. The AP

may allocate the whole channel to only one client at a time or it

may partition the channel to serve multiple clients simultane-

ously. For example, an 802.11ax AP could simultaneously com-

municate (uplink or downlink) with one 802.11ax client using an

8 MHz subchannel and three other 802.11ax clients using 4 MHz

subchannels.

In addition to 20 MHz channels, 40, 80, and even 160 MHz chan-

nels can also be partitioned into various combinations of RUs as

shown in Table 2-1. For example, if an 80 MHz channel was sub-

divided using strictly 26 subcarrier RUs, 37 802.11ax clients could

theoretically communicate simultaneously using their OFDMA

capabilities.

Most real-world 802.11ax deployments will likely use 20 MHz

channels with a maximum of nine clients participating in multi-

user OFDMA transmissions per transmission opportunity (TXOP).

Remember, the whole point of OFDMA is to make use of smaller

subchannels.

TABLE 2-1 Resource Units and Wide Channels

Resource

20 MHz 40 MHz 80 MHz 160 MHz 80 + 80 MHz

Units (RUs)

channel

channel

channel

channel

channel

996 (2x)

n/a

n/a

n/a

1 client

1 client

subcarriers

996 subcarriers

n/a

n/a

1 client

2 clients

2 clients

484 subcarriers

n/a

1 client

2 clients

4 clients

4 clients

242 subcarriers

1 client

2 clients

4 clients

8 clients

8 clients

106 subcarriers

2 clients

4 clients

8 clients

16 clients

16 clients

52 subcarriers

4 clients

8 clients

16 clients

32 clients

32 clients

26 subcarriers

9 clients

18 clients

37 clients

74 clients

74 clients

Remember that 802.11ax APs can transmit downlink to multi-

ple 802.11ax clients as well as synchronize simultaneous uplink

transmissions from multiple 802.11ax clients. Synchronized

uplink transmission is a capability never seen before with Wi-Fi

CHAPTER 2 Understanding Key 802.11ax Technologies 15

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communications. In both cases, trigger frames are needed to bring about the necessary frame exchanges for multi-user communications. For example, a trigger frame is used to allocate RUs to

802.11ax clients. Trigger frames are also used to query 802.11ax

clients about buffered data and about the quality of service (QoS)

category of data intended for uplink OFDMA transmissions.

802.11ax clients respond with buffer status reports which assists the AP in allocating RUSs for synchronized uplink transmissions.

Also, understand that the rules of medium contention still apply.

The AP still has to compete for a transmission opportunity (TXOP)

against legacy 802.11 stations. Once the AP has a TXOP, the AP

is then in control of up to nine 802.11ax client stations for either

downlink or uplink transmissions within a 20 MHz channel The

number of RUs used can vary on a per TXOP basis.

MU-MIMO

Introduced in 802.11ac, multi-user, multiple-input multiple-

output (MU-MIMO) technology theoretically allows multiple

frames to be transmitted to different receivers at the same time

and on the same channel, using multiple spatial streams to pro-

vide greater efficiency (see Figure 2-4). MU-MIMO provides spa-

tial diversity by transmitting unique modulated data streams to

multiple clients simultaneously. 802.11ac only defined downlink

(DL) MU-MIMO and it is not widely implemented for the follow-

ing reasons:

» Very few MU-MIMO-capable 802.11ac clients exist in the

current marketplace, and the technology is rarely used in the

enterprise. Many client devices are single antenna, and many

dual antenna clients switch to single stream mode for DL

MU-MIMO to protect against interference.

» MU-MIMO requires sizable physical distance between the

clients, as well as the AP, for spatial diversity, which may limit

its usefulness. Most enterprise Wi-Fi deployments involve a

high density of users, which is not conducive to MU-MIMO.

» MU-MIMO requires transmit beamforming (TXBF), which

requires sounding frames. The sounding frames add

excessive overhead, especially when the bulk of data frames

are small, and may negatively impact performance gains.

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FIGURE 2-4: MU-MIMO — multi-user multiple input multiple output.

To address these issues, there are some significant MU-MIMO

enhancements proposed in the 802.11ax draft amendment includ-

ing grouping sounding frames, data frames, and other frames

among multiple users to reduce overhead and increase uplink

response time. Trigger frames would also be used to signal 802.11ax

clients to participate in uplink MU-MIMO communications.

A key difference between 802.11ac MU-MIMO and 802.11ax MU-

MIMO is how many MU-MIMO clients communicate with an

AP at the same time. 802.11ac is limited to a MU-MIMO group

of only four clients. 802.11ax is designed to support up to 8x8x8

MU-MIMO in both downlink and uplink, which allows it to serve

up to eight users simultaneously and provide significantly higher

data throughput. Be aware that support for uplink MU-MIMO will

not be available in the first generation of 802.11ax client radios.

The minimum RU size for MU-MIMO (downlink or uplink) is 106

subcarriers or greater.

802.11ax allows for simultaneous use of both MU-OFDMA and

MU-MIMO, but this is not expected to be widely implemented.

Table 2-2 compares MU-OFDMA and MU-MIMO.

MU-MIMO would theoretically be a favorable option in very low

client density, high-bandwidth application environments where

large packets are transmitted.

CHAPTER 2 Understanding Key 802.11ax Technologies 17

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TABLE 2-2 MU-OFDMA and MU-MIMO Comparison

MU-OFDMA

MU-MIMO

Increased efficiency

Increased capacity

Reduced latency

Higher data rates per user

Best for low-bandwidth applications

Best for high-bandwidth applications

Best with small packets

Best with large packets

Don’t confuse OFDMA with MU-MIMO. OFDMA enables multi-

user access by subdividing a channel. MU-MIMO enables multi-

user access by using different spatial streams.

Spatial Reuse (BSS Coloring)

Wi-Fi uses radio frequency (RF) communication which is a half-

duplex medium — only one radio can transmit on a frequency

domain or channel at any given time. Everyone must take turns

because if everyone “talks” at the same time, no data is commu-

nicated because no one is “listening.”

Carrier sense with multiple access collision avoidance (CSMA/CA) is the method used in Wi-Fi networks to ensure that only one radio can

transmit on the same channel at any given time. An 802.11 radio will

defer transmissions if it hears the physical (PHY) preamble trans-

missions of any other 802.11 radio at a signal detect (SD) thresh-

old of four decibels (dB) or greater. CSMA/CA consumes a lot of

the available bandwidth. This problem is referred to as contention

overhead. Unnecessary medium contention overhead that occurs

when too many APs and clients hear each other on the same chan-

nel is called an overlapping basic service set (OBSS), also commonly referred to as co-channel interference (CCI), shown in Figure 2-5.

For example, if AP-1 on channel 6 hears the preamble transmis-

sion of a nearby AP (AP-2), also transmitting on channel 6, AP-1

will defer and can’t transmit at the same time. Likewise, all the

clients associated to AP-1 must also defer transmission if they

hear the preamble transmission of AP-2. All these deferrals cre-

ate medium contention overhead and consume valuable airtime

because you have two basic service sets on the same channel that

can hear each other, in the manner of OBSS.

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FIGURE 2-5: OBSS — Overlapping basic service set.

In reality, Wi-Fi clients are the primary cause of OBSS interfer-

ence. As shown in Figure 2-6, if a client associated to AP-2 is transmitting on channel 36, it is possible that AP-1 (and any clients associated to AP-1) will hear the PHY preamble of the client

and must defer any transmissions.

FIGURE 2-6: OBSS interference caused by client.

Due to the mobile nature of Wi-Fi client devices, OBSS interfer-

ence isn’t static: It changes as client devices move.

All this congestion and medium contention overhead means that

efficiency at the MAC sublayer drops. This is further exacerbated

by the fact that the bulk of data frames in a network are small (less

than 256 bytes) and OBSS in dense deployments often unneces-

sarily blocks transmissions. Thus, the average transmission con-

trol protocol (TCP) throughput under ideal conditions in legacy

a/b/g networks is roughly 40 to 50 percent of advertised data

CHAPTER 2 Understanding Key 802.11ax Technologies 19

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rates, and 60 to 70 percent of advertised data rates in 802.11n/ac networks. To increase capacity in dense environments, frequency

reuse between basic service sets needs to be increased.

802.11ax was also tasked with addressing the OBSS challenge by

improving spatial reuse, which is often referred to as BSS color-

ing . BSS coloring is a mechanism, originally introduced in 802.11ah, to address medium contention overhead due to OBSS by assigning

a different “color” — a number between 0 and 7 that is added to

the PHY header of the 802.11ax frame — to each BSS in an envi-

ronment (see Figure 2-7).

FIGURE 2-7: BSS coloring.

BSS coloring detects a color bit in the PHY header of an 802.11ax

frame transmission. This means that legacy 802.11a/b/g/n clients

will not be able to interpret the color bits because they use a dif-

ferent PHY header format.

When an 802.11ax radio is listening to the medium and hears the

PHY header of an 802.11ax frame sent by another 802.11ax radio,

the listening radio will check the BSS color bit of the transmitting

radio. Channel access is dependent on the color detected:

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» If the color bit is the same, then the frame is considered an

intra-BSS transmission and the listening radio will defer.

» If the color bit is different, then the frame is considered an

inter-BSS transmission from an OBSS and the listening radio

treats the medium as busy only for the time it took to

determine the color bit was different.

802.11ax radios can adjust the carrier sense operation based on the

color of the BSS to improve spatial reuse efficiency and perfor-

mance. Depending on the BSS from which the traffic is generated,

the station can use different sensitivity thresholds to transmit or

defer. This results in higher overall performance. Using adap-

tive clear channel assessment (CCA), an 802.11ax radio can raise

the SD threshold for inter-BSS frames while maintaining a lower

threshold for intra-BSS frames. BSS coloring can thus potentially

decrease the channel contention problem that is symptomatic of

existing low SD thresholds.

CHAPTER 2 Understanding Key 802.11ax Technologies 21

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IN THIS CHAPTER

» Conserving power with TWT

» Achieving higher data speeds with

1024-QAM

» Defining new frame formats

» Exploring 802.11ax design considerations

Chapter 3

Looking at Other

802.11ax Enhancements

and Design

Considerations

In this chapter, you learn about several other 802.11ax enhance-

ments including target wake time (TWT), 1024 quadrature

amplitude modulation (1024-QAM), and new frame formats,

as well as design considerations when deploying 802.11ax

technology.

Target Wake Time (TWT)

Target wake time (TWT) is a power-saving mechanism originally

defined in the 802.11ah-2016 amendment. A TWT is a negotiated

agreement, based on expected traffic activity between the access

point (AP) and Wi-Fi clients, to specify a scheduled target wake-

up time for clients in power-save (PS) mode. In addition to the

power-saving benefits, the negotiated TWTs allow an AP to man-

age client activity by scheduling client stations to operate at differ-

ent times and therefore minimize contention between the clients.

CHAPTER 3 Other 802.11ax Enhancements & Design Considerations 23

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A TWT reduces the required amount of time that a client in PS

mode needs to be awake. This allows the client to sleep longer and

reduces energy consumption. As opposed to legacy client power-

saving mechanisms, which require sleeping client devices to

wake-up in microsecond intervals, TWT could theoretically allow

client devices to sleep for hours. TWT is thus an ideal power-

saving method for mobile devices and Internet of Things (IoT)

devices that need to conserve battery life.

It remains to be seen if IoT device manufacturers will take advan-

tage of 802.11ax radios in their IoT devices as opposed to other

communication technologies such as Bluetooth Mesh, Thread,

and Zigbee.

TWT setup frames are used between the AP and the client to nego-

tiate a scheduled TWT. For each 802.11ax client there can be as

many as 8 separate negotiated scheduled wake-up agreements for

different types of application traffic. 802.11ax has also extended

TWT functionality to include a non-negotiated TWT capability.

An AP can create wake-up schedules and deliver TWT values to

the 802.11ax clients via a broadcast TWT procedure.

1024-QAM

Although the primary goal of 802.11ax is better efficiency, more

speed isn’t a bad thing. And better efficiency and more speed

aren’t mutually exclusive goals. Quadrature amplitude modulation

(QAM) uses both the phase and amplitude of an RF signal to rep-

resent data bits. 802.11ax will support 1024-QAM and new modu-

lation and coding schemes (MCSs) that define higher data rates.

For comparison, 256-QAM (introduced in 802.11ac) modulates

8 bits per symbol, whereas 1024-QAM modulates 10 bits per

symbol — a potential 20 percent increase in data throughput. This

throughput is achieved using more efficient packaging of data for

the same spectrum — analogous to using a double-decker bus to

make the best use of a bus lane.

802.11ax also introduces two new MCSs: MCS-10 and MCS-11,

which will most likely be optional. 1024-QAM can only be used

with 242-subcarrier resource units (RUs) or larger. This means

that at least a full 20 MHz channel will be needed for 1024-QAM.

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Much like 256-QAM, very high signal-to-noise ratio (SNR) thresholds (35 dB or more) will be needed in order for 802.11ax

radios to use 1024-QAM modulation. Pristine RF environments

with a low noise floor and close proximity between an 802.11ax AP

and 802.11ax client will most likely be needed.

The number of points in the modulation constellation determines

the number of bits conveyed with each symbol. Figure 3-1 shows a

comparison of constellation charts between 256-QAM and 1024-

QAM modulation. As you can see, 1024-QAM has many more con-

stellation points. Error vector magnitude (EVM) is a measure used to quantify the performance of a radio receiver or transmitter in

regard to modulation accuracy. With QAM modulation, EVM is a

measure of how far a received signal is from a constellation point.

802.11ax radios that use 1024-QAM modulation will need strong

EVM and receive sensitivity capabilities.

FIGURE 3-1: 256- and 1024-QAM.

New PHY Headers

Added to all 802.11 frames is a physical (PHY) header that con-

tains a preamble and other information used for initial setup of

communications between two radios. The 802.11ax amendment

also defines four new PHY headers to support high efficiency (HE)

radio transmission, as follows:

» HE SU: The high efficiency single-user PHY header is used for

single-user transmissions.

» HE MU: The high efficiency multi-user PHY header is used for

transmissions to one or more users. This format information

CHAPTER 3 Other 802.11ax Enhancements & Design Considerations 25

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is used for both multi-user multiple-input multiple-output (MU-MIMO) and multi-user orthogonal frequency domain

multiple access (MU-OFDMA), as well as resource unit (RU)

allocation (see Chapter 2).

» HE ER SU: The high efficiency extended-range single-user

format is intended for a single user. Portions of this PHY

header are boosted by 3 dB to enhance outdoor communi-

cations and range.

» HE TB: The high efficiency trigger-based format is for a

transmission that is a response to a trigger frame. In other

words, this PPDU format is used for uplink communications.

The preamble is used for synchronization between transmitting

and receiving radios and consists of two parts: legacy and high

efficiency (HE). The legacy preamble is easily decodable by legacy

stations (STAs) and is included for backward compatibility. The

HE preamble components are used to communicate information

between 802.11ax radios about OFDMA, MU-MIMO, BSS coloring,

and more.

WHY WE CAN’T YET

ABANDON 2.4 GHz

With lots of spectrum at 5 GHz, you may be wondering why 2.4 GHz

has not been abandoned? Yes, it’s crowded, it’s old, and 802.11ac did

not support it. Even 802.11n, which does support 2.4 GHz, is limited

by the availability of only three 20 MHz channels (1, 6, and 11.)

But at the end of the day, it’s still spectrum that can be used for Wi-Fi, and we need to make the most of it.

Consider the following 2.4 GHz realities:

• Range: Due to the wavelength properties of an RF signal, the

effective range of a lower frequency is a greater distance than a

higher frequency.

More importantly, consider rate versus range — how much data

you can send over a given distance per unit of time. This is a factor

of more than just range or frequency alone. You also need to con-

sider transmit power, channel bandwidth, MCS, protocol over-

head, traffic type (class and quality of service), and more.

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• Installed base: There are hundreds of millions of 2.4 GHz Wi-Fi devices still in use today. Many of these are mission-critical, such

as in medical and security applications, and many of these are

expensive and cannot be easily replaced, let alone upgraded to

the latest Wi-Fi standards. You simply need to wait until all these

devices die a natural death before 5 GHz, or at least a more con-

temporary Wi-Fi technology, is an option.

Even today, many new IoT devices and even some new laptops

and smartphones only support 2.4 GHz. Device vendors choose

this option because costs are reduced over dual-band capabilities,

and no one should be surprised at how many price-sensitive users

there are — and always will be — in the world.

• Looking ahead: Even as people eventually realized that 5 GHz was a much larger chunk of spectrum than 2.4 GHz, it was still under-utilized until 802.11n became well-established — and that was

only about five years ago. Adoption has been swift, to the point

that many now have concerns about crowding in the 5 GHz bands.

But 2.4 GHz is still here to relieve the pressure — and good Wi-Fi

infrastructure systems, properly implemented and configured,

can automatically move traffic to an optimal frequency band and

channel.

802.11ax, unlike 802.11ac, will be able to operate at both 2.4 and

5 GHz. Thus, 2.4 GHz remains a vital element in any good long-term

Wi-Fi strategy. The bottom line is that the world can’t abandon

2.4 GHz any time soon, even if a big chunk of new unlicensed spec-

trum became available — which is very unlikely. 2.4 GHz will continue

to provide a highway for tens of millions of devices for the foresee-

able future.

Design Considerations

Some important design considerations for 802.11ax include:

» Power over Ethernet (PoE): Will 802.11ax APs work with

standard 802.3af PoE? Wi-Fi manufacturers will be adding

more radio chains to their 802.11ax access points. Most

802.11ax APs will be dual-band 4x4:4 APs and there will even

CHAPTER 3 Other 802.11ax Enhancements & Design Considerations 27

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be 8x8:8 APs. 802.11ax APs will also require much more

processing power than previous generations of enterprise

APs. The extra radio chains and processor capabilities will

require more power. The 15.4 watts (W) provided by

standard 802.11af PoE will not be adequate. 802.3at PoE

Plus power will be required. PoE Plus requirements for

802.11ax APs should be considered a standard requirement.

This may require upgrades of access layer switches as well as

recalculation of PoE power budgets.

» MultiGig: Will 2.5 Gig Ethernet ports for 802.11ax access

points be needed? The whole point of 802.11ax is to cut

down on medium contention and airtime consumption.

Logic dictates that if Wi-Fi becomes more efficient, the user

traffic generated by a dual-frequency 802.11ax AP could

potentially exceed 1 Gigabit. The fear is that a standard

Gigabit Ethernet wired uplink port could be a bottleneck and

therefore 2.5 Gigabit uplink ports will be needed. However,

in the real-world, we probably will still not exceed 1 Gigabit

until there is a wide proliferation of 802.11ax clients.

Regardless, most WLAN vendor 802.11ax APs will include

at least one 802.3bz MultiGig Ethernet port capable of a

2.5 Gigabit wired uplink.

» Client devices: Will there be any 8x8:8 802.11ax clients?

Most 802.11ax mobile client devices will use dual-frequency

2x2:2 radios because an 8x8:8 radio would drain battery life.

There are currently no 4x4:4 802.11ax clients; however, in

the future, you might see some 4x4:4 client radios in

high-end laptops.

802.11ax clients take full advantage of 802.11ax high

efficiency capabilities such as multi-user OFDMA. Although

there will be no physical (PHY) layer improvements with

legacy clients, there will be performance improvements as a

result of newer hardware capabilities of the new 802.11ax

APs, such as stronger CPUs and better memory handling.

Additionally, as you see more 802.11ax clients mixed into the

client population, the efficiency improvements gained by

802.11ax client devices will free valuable airtime for those

older clients, therefore improving the overall efficiency of the

wireless network.

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IN THIS CHAPTER

» Deploying 802.11ax in high performance

environments

» Looking at 802.11ax for indoor and

industrial environments

Chapter 4

Exploring the Aerohive

802.11ax Family

In this chapter, you learn about Aerohive’s 802.11ax family of

access points which are designed for high performance envi-

ronments and combine the latest in Wi-Fi and Ethernet stan-

dards with Aerohive’s software-defined Wi-Fi architecture.

AP630

The AP630 is designed for high performance environments, com-

bining the latest in Wi-Fi standards (IEEE 802.11ax technology)

with Aerohive’s HiveOS software and HiveManager network man-

agement system.

The AP630 (see Figure 4-1) also enables Internet of Things (IoT)

readiness with built-in Bluetooth Low Energy (BLE) and Univer-

sal Serial Bus (USB) ports.

The AP630 is designed for:

» High performance indoor environments with high definition

(HD) video streaming, large file transfers, and HD video

collaboration applications

CHAPTER 4 Exploring the Aerohive 802.11ax Family 29

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FIGURE 4-1: The AP630.

» High client density environments where most or all clients

are 802.11ac or newer

» Environments expecting to use Voice over Wi-Fi (VoWiFi) in addition to data

» Environments expected to use IoT applications like BLE at deployment or in the future

AP650 and AP650X

The AP650 and AP650X (see Figure 4-2) are designed for high

performance environments, combining the latest in Wi-Fi stan-

dards (IEEE 802.11ax technology), the latest in Ethernet standards

(2.5 Gigabit capability), and Aerohive’s software-defined dual

5 gigahertz (GHz) radios for indoor and industrial environments.

AP650 and 650X have integrated BLE and USB connectivity for

enhanced location-driven services and the capability to provide

additional wireless access options for IoT and other devices.

Dual 5 GHz 4x4:4 software-defined radios (SDRs) in the AP650

and AP650X provide superior flexibility, performance, and return

on investment (ROI) compared to legacy access points with only

a single 5 GHz radio.

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FIGURE 4-2: The AP650 and AP650X.

The AP650 is designed for:

» High performance indoor environments: HD video

streaming, large file transfers, and HD video collaboration

applications

» Very high client density environments: where density and

performance are key requirements

» Environments expecting to use VoWiFi in addition to data

» Environments expected to use IoT applications like BLE at deployment or in the future

The AP650X is designed for:

» Industrial deployments like warehouses running high

bandwidth applications and/or high client densities with

extreme temperature ranges

» Lecture halls or auditorium-like environments requiring

specialized Wi-Fi setup using a mix of omni/sector antennas

See Table 4-1 for a comparison of Aerohive’s 802.11ax family of

access points.

CHAPTER 4 Exploring the Aerohive 802.11ax Family 31

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TABLE 4-1 Aerohive 802.11ax AP Family Comparison

AP630

AP650

AP650X

Environment

indoor – plenum

Radio

Dual frequency

Dual frequency 802.11ax radios;

Technology

802.11ax radios

Dual 5 GHz capability w/software

selectable radio

Performance

4x:4 MU-MIMO & OFDMA UL/DL

Security

Trusted Platform Module (TPM) security chip

Power

802.3at Power over

802.3at Power over Ethernet (PoE+),

Ethernet (PoE+)

direct current (DC)

Interfaces

2 x Gigabit Ethernet

2.5G + 1G (2 x PoE) with link

(2 x PoE) with link

aggregation

aggregation

IoT

USB + BLE

Operating Temp

0°C to 40°C

-20°C to 55°C

(32°F to 104°F)

(-4°F to 131°F)

Deployment

HiveManager cloud and on-premises

Aerohive’s family of 802.11ax access points also features a new

twist mount bracket designed to radically simplify installation.

Traditional mounting brackets are often poorly designed and

cumbersome; the new design from Aerohive makes it easy for

anyone to place and lock an access point in position in a matter of

seconds. See Figure 4-3.

FIGURE 4-3: Aerohive’s mounting bracket.

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IN THIS CHAPTER

» Getting ready for the next Wi-Fi standard

» Supporting legacy Wi-Fi devices

» Looking at high-density use cases

» Achieving high efficiency and high

performance

» Improving Wi-Fi security

Chapter 5

Ten Things You Need to

Know about 802.11ax

I n this chapter, we point out ten key things to keep in mind

about the new 802.11ax Wi-Fi standard.

» It’s a Wi-Fi paradigm shift. The new 802.11ax standard

doesn’t just push the envelope with regard to Wi-Fi speeds —

up to 10 Gbps. It introduces numerous performance

improvements as well. In fact, it’s been dubbed “High

Efficiency” unlike previous 802.11 amendments that were

labeled “High Throughput.” 802.11ax is not just about better

throughput. The 802.11ax standard will substantially

improve capacity, provide better coverage, and reduce

congestion in Wi-Fi networks.

» The standard isn’t yet finalized. Completion of the

802.11ax standard is on the horizon and full certification will

start in 2019. However just like 802.11n and 802.11ac, the

core requirements of the chipsets are defined long before

final certification and commercial 802.11ax products are

now being manufactured. Only the overall process, opera-

tions, and — dare we say — politics are still being debated

and delaying the official certification.

CHAPTER 5 Ten Things You Need to Know about 802.11ax 33

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This is the same process that occurred with 802.11n and

802.11ac. Final approval of the standard usually lags new

prestandard product releases. Once the standard is finalized,

firmware or software updates are typically provided by the

product vendors to achieve full compliance in their early

release products.

» You won’t need to rip-and-replace your existing Wi-Fi

installations. Market dominance for 802.11ax products isn’t

anticipated until late 2020 in terms of total sales. Therefore,

don’t expect to perform a wholesale rip-and-replace of your

existing 802.11ac installations in the near term. However, if

you expect your next upgrade to last 5+ years, it only makes

sense to upgrade with 802.11ax technology. Additionally, if

your organization still has legacy 802.11a/b/g/n APs deployed,

go ahead and consider an enterprise-wide upgrade.

Some organizations will, of course, need the performance

boost embodied in 802.11ax right away because the

demands on their networks are growing at a rapid pace.

Most end-user organizations, however, will follow a pattern

well-established with 802.11n and 802.11ac — augmentation

of existing infrastructure to add new (greenfield) capacity

and planned replacements of older technologies.

» Look forward to a little backward compatibility. Unlike the

802.11ac standard, 802.11ax supports both 2.4 and 5 GHz

wireless devices, so 802.11n (and potentially 802.11g and

802.11b) devices will be able to run on 802.11ax Wi-Fi networks.

This is critical for many legacy specialized devices, particularly in

healthcare and industrial automation, as vendors in these

verticals tend to move slowly to update their devices to the

latest Wi-Fi standards.

» Your smarthome is a high-density Wi-Fi environment.

The primary use case defined for 802.11ax is high density

network environments. But high-density doesn’t just mean

stadiums, hospitals, and warehouses. Today’s smarthomes

quickly become “high density” with 20 or more wireless

devices — anything from smartphones, tablets, laptops,

game consoles, and television receivers to security cameras,

baby monitors, and smart thermostats and appliances —

connecting to a home Wi-Fi network.

» RU ready for simultaneous multi-user Wi-Fi access?

Multi-user orthogonal frequency division multiple access

(OFDMA) is easily the most important new capability in

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802.11ax. It subdivides a channel into smaller frequency

allocations, called resource units (RUs), thereby enabling an

access point (AP) to synchronize communication (uplink and

downlink) with multiple individual clients assigned to the RUs.

» MU-MIMO enhancements are coming. Several enhance-

ments to MU-MIMO proposed in 802.11ax include grouping

sounding frames, data frames, and other frames among

multiple users to reduce overhead and increase uplink

response time. Another key difference is how many MU-MIMO

clients communicate with an AP at the same time: 802.11ac

is limited to a MU-MIMO group of only four clients, whereas

802.11ax supports up to 8x8x8 MU-MIMO in both downlink and

uplink, which allows it to serve up to eight users simultaneously.

» No more OBSSessing over spatial reuse. Basic service set

(BSS) coloring addresses medium contention overhead due to

overlapping basic service sets (OBSS) by assigning a different

“color” to each BSS in an environment to decrease channel

contention with adaptive signal detect (SD) thresholds.

» No qualms about higher data speeds either. Quadrature

amplitude modulation (QAM) effectively doubles bandwidth

by combining two amplitude-modulated signals into a single

channel. 802.11ax will support 1024-QAM and new modula-

tion and coding schemes (MCS) that define higher data rates

providing a potential 20 percent increase in data throughput

over 256-QAM (introduced in 802.11ac).

» Wi-Fi security will be better. Although the 802.11ax

standard itself doesn’t specify any new security enhance-

ments or requirements, it does require WPA3 security as a

prerequisite. As a result, 802.11ax devices will include the

latest security design features and capabilities to address

modern threats that did not exist just a few years ago when

802.11ac was released — not to mention 802.11n and

802.11g (released in 2009 and 2003, respectively). The Wi-Fi

Protected Access Version 3 (WPA3) security protocol,

introduces security enhancements, most importantly,

Simultaneous Authentication of Equals (SAE) as a replace-

ment for WPA2-Personal’s Pre-Shared Key (PSK). WPA3 also

requires Protected Management Frames (PMF) for more

robust protection against brute force attacks. Additionally,

WPA3 provides for an optional 192-bit encryption suite.

CHAPTER 5 Ten Things You Need to Know about 802.11ax 35

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Glossary

802.11ac: The most current IEEE Wi-Fi standard that has been widely adopted. Released in 2013, 802.11ac operates in the 5 GHz frequency

band and supports up to eight spatial streams, 256-QAM, and downlink

MU-MIMO. See also Institute of Electrical and Electronics Engineers (IEEE), gigahertz (GHz), quadrature amplitude modulation (QAM), and

multi-user multiple-input multiple-output (MU-MIMO).

802.11ah: (“Wi-Fi HaLow”): An IEEE Wi-Fi standard that uses 900 MHz license-exempt bands to provide extended range networks and low

energy consumption. See also Institute of Electrical and Electronics Engineers (IEEE) and megahertz (MHz).

802.11ax: The IEEE draft standard that will be the successor to 802.11ac and is focused primarily on high efficiency (HE). See also Institute of Electrical and Electronics Engineers (IEEE) and 802.11ac.

802.3bz: The IEEE standard that defines 2.5 and 5 gigabit per second (Gbit/s) wire speeds in Ethernet wired networks. See also Institute of Electrical and Electronics Engineers (IEEE) and Ethernet.

access point (AP): An RF device that allows wireless devices to connect to a network. An access point usually functions as a wireless portal to

pre-existing network resources. See also radio frequency (RF).

AP: See access point (AP).

basic service set (BSS): A set of APs and clients that can communicate with each other at the PHY layer in a WLAN architecture. See also

access point (AP), physical (PHY) layer, and wireless local area network (WLAN).

BLE: See Bluetooth Low Energy.

Glossary 37

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Bluetooth: A wireless technology standard for data exchange over short distances between fixed and mobile devices using short-wavelength

UHF radio waves in the 2.4 to 2.485 GHz ISM band. See also ultra-high frequency (UHF), gigahertz (GHz), and industrial, scientific, and medical (ISM) band.

Bluetooth Low Energy (BLE): A WPAN technology designed by the

Bluetooth SIG. BLE operates in the classic Bluetooth ISM band (2.4 –

2.4835 GHz) using different channels (40 2-MHz channels compared to

79 1-MHz channels in classic Bluetooth) and provides significantly lower

power consumption and cost than classic Bluetooth for applications

such as healthcare, fitness, security, and home entertainment. See also wireless personal area network (WPAN), Bluetooth Special Interest

Group (Bluetooth SIG), Bluetooth, industrial, scientific, and medical (ISM) band, Gigahertz (GHz), and Megahertz (MHz).

BSS: See base service set (BSS).

carrier sense with multiple access collision avoidance (CSMA/CA):

A Wi-Fi network protocol which checks to ensure no other wireless node

is transmitting before attempting to send a packet across the network.

If another transmitting node is detected, the node waits for a random

period (backoff factor) then checks again to ensure no other wireless

node is transmitting before attempting to send the packet across the

network.

CCA: See clear channel assessment (CCA).

CCI: See co-channel interference (CCI).

clear channel assessment (CCA): A carrier sense mechanism used in

Wi-Fi networks to determine whether a medium is idle or not.

Clear to Send (CTS): An optional flow control mechanism used in 802.11

networks to reduce frame collisions. See also Request to Send (RTS).

CLI: See command-line interface (CLI).

co-channel interference (CCI): See overlapping basic service set (OBSS).

command-line interface (CLI): A text-based console used to interact with a hardware or software device.

CSMA/CA: See carrier sense with multiple access collision avoidance (CSMA/CA).

dB: See decibel (dB).

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decibel (dB): A unit used to measure the intensity of sound or the power level of an electrical signal by comparing it with a given logarith-mic scale.

DL: See downlink (DL).

downlink (DL): The transmission from an AP to a Wi-Fi client device. See also access point (AP) and uplink (UL).

error vector magnitude (EVM): A measure used to quantify the

performance of a radio transmitter or receiver.

Ethernet: A family of technologies commonly used in wired computer networking. Defined in the IEEE 802.3 standard.

gigahertz (GHz): A measure of bandwidth in a digital signal. One

gigahertz is equal to one billion hertz.

GHz: See gigahertz (GHz).

IEEE: See Institute of Electrical and Electronics Engineers (IEEE).

industrial, scientific, and medical (ISM) band: The parts of the RF

radio spectrum that are reserved for industrial, scientific, and medical

requirements. See also radio frequency (RF).

Institute of Electrical and Electronics Engineers (IEEE): A technical professional organization that promotes the advancement of

technology.

Internet of Things (IoT): A system of smart, connected devices.

Internet Protocol (IP): The method by which data is sent between

devices on a network such as the Internet.

Inverse Fast Fourier Transform (IFFT): An algorithm that samples a signal over a period of time (or space) and divides it into frequency

components.

IoT: See Internet of Things (IoT).

IP: See Internet Protocol (IP).

ISM: See industrial, scientific, and medical (ISM) band.

ITU: See International Telecommunications Union (ITU).

kHz: See kilohertz (kHz).

Glossary 39

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kilohertz (kHz): A measure of bandwidth in a digital signal. One kilohertz is equal to one thousand hertz.

LAN: local area network.

MAC sublayer: See medium access control (MAC) sublayer.

MCS: See modulation and coding scheme (MCS).

medium access control (MAC) sublayer: A sublayer defined at the

data link layer that provides flow control and multiplexing for the

transmission medium.

megahertz (MHz): A measure of bandwidth in a digital signal. One

megahertz is equal to one million hertz.

MHz: See megahertz (MHz).

microsecond (μS): One millionth of a second.

modulation and coding scheme (MCS): Describes the combination of

the radio carrier modulation scheme and the coding scheme to

determine the data rate of a wireless network connection.

MU: See multi-user (MU).

multi-user (MU): Transmissions between an AP and multiple Wi-Fi

clients can occur simultaneously, depending on the supporting technol-

ogy. See also access point (AP).

MU-MIMO: See multi-user multiple-input multiple-output (MU-MIMO).

multi-user multiple-input multiple-output (MU-MIMO): Technology

that theoretically allows multiple frames to be transmitted to different

receivers at the same time and on the same channel, using multiple

spatial streams to provide greater efficiency. See also radio frequency (RF).

OBSS: See overlapping base service set (OBSS).

OFDM: See orthogonal frequency-division multiplexing (OFDM).

OFDMA: See orthogonal frequency-division multiple access (OFDMA).

orthogonal frequency-division multiple access (OFDMA): A method

that allows multiple users with varying bandwidth needs to be served

simultaneously by subdividing a channel into smaller frequency

allocations, called RUs. See also resource units (RUs).

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orthogonal frequency-division multiplexing (OFDM): A method that divides a channel into subcarriers through a mathematical function

known as IFFT. See also Inverse Fast Fourier Transform (IFFT).

overlapping basic service set (OBSS): Degenerative medium conten-

tion overhead that occurs when too many APs and clients hear each

other on the same channel.

phase-shift keying (PSK): A digital modulation process used in Wi-Fi networks to convey data by changing (modulating) the phase of a

reference signal (the carrier wave).

PHY: See physical (PHY) layer.

physical (PHY) layer: Refers to the circuitry required to implement physical layer functions and connect a MAC sublayer device to a physical

medium. See also medium access control (MAC) sublayer.

PoE+: See Power over Ethernet plus (PoE+).

Power over Ethernet plus (PoE+): An IEEE standard that provides up to 25 watts of power for “Type 2” devices.

power-save (PS) mode: An optional mode for 802.11 client stations. A wireless client can shut down some of the transceiver components for a

period of time to conserve power.

PS mode: See power-save (PS) mode.

PSK: See phase-shift keying (PSK).

QAM: See Quadrature Amplitude Modulation (QAM).

Quadrature Amplitude Modulation (QAM): A modulation scheme that

conveys data by changing some aspect of a carrier signal or the carrier

wave in response to a data signal.

radio frequency (RF): An electromagnetic wave frequency used in radio communication.

Request to Send (RTS): An optional flow control mechanism used in

802.11 networks to reduce frame collisions. See also Clear to Send (CTS).

resource units (RUs): A frequency allocation that has been partitioned from an OFDMA channel.

RF: See radio frequency (RF).

RTS: See Request to Send (RTS).

Glossary 41

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RUs: See resource units (RUs).

SDR: See software-defined radio (SDR).

SD threshold: See signal detect (SD) threshold.

SFO: See sampling frequency offset (SFO).

signal detect (SD) threshold: A listening threshold used by 802.11

radios to identify any 802.11 preamble transmissions from another

transmitting 802.11 radio.

signal-to-noise ratio (SNR): The ratio of the strength of an electrical or other signal carrying information to that of the ambient noise floor,

generally expressed in dB. See also decibels (dB).

SNR: See signal-to-noise ratio (SNR).

software-defined radio (SDR): A radio communication system where

traditional hardware components are instead implemented in software.

STA: See station (STA).

station (STA): An 802.11 radio. The radio can reside in an AP or be used as a client station.

Target Wake Time (TWT): A function that permits an AP and client

stations to negotiate a specific time or set of times for individual stations to access the medium. See also access point (AP).

TCP: See transmission control protocol (TCP).

TPM: See Trusted Platform Module (TPM).

transmission control protocol (TCP): A standard that defines how to establish and maintain a network conversation.

transmission opportunity (TXOP): A period of time in which an 802.11

radio has control of the RF medium and can transmit. See also radio frequency (RF).

transmit beamforming (TXBF): A method that allows a multiple-input/

multiple-output (MIMO) transmitter using multiple antennas to adjust

the phase and amplitude of the outgoing transmissions in a coordinated

method.

Trusted Platform Module (TPM): A specialized chip on an endpoint

device that stores encryption keys specific to the host system for

hardware authentication.

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TWT: See Target Wake Time (TWT).

TXBF: See transmit beamforming (TXBF).

TXOP: See transmission opportunity (TXOP).

UL: See uplink (UL).

ultra-high frequency (UHF): The ITU designation for RF frequencies between 300 MHz and 3 GHz. See also International Telecommunications Union (ITU), radio frequency (RF), megahertz (MHz), and gigahertz (GHz).

Universal Serial Bus (USB): An industry standard developed to define cables, connectors, and protocols for connection, communication, and

power supply between personal computers and peripheral devices.

Uplink (UL): The transmission from a client Wi-Fi device to an AP. See also access point (AP) and downlink (DL).

Voice over IP (VoIP): A methodology and group of technologies for the delivery of voice communications and multimedia sessions over IP

networks, such as the Internet.

Voice over Wi-Fi (VoWiFi): Commercial telephony services delivered over a Wi-Fi network using VoIP technologies. See also Voice over IP (VoIP).

VoIP: See Voice over IP (VoIP).

VoWiFi: See Voice over Wi-Fi (VoWiFi).

wireless local area network (WLAN): A wireless network that links two or more devices using wireless communication within a limited area

such as a home, school, office building, or warehouse.

WLAN: See wireless local area network (WLAN).

Glossary 43

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Document Outline

- Title Page

- Copyright Page

- Table of Contents

- Introduction

- About This Book

- Foolish Assumptions

- Icons Used in This Book

- Beyond the Book

- Where to Go from Here

- Chapter 1 Recognizing the Business Need for Better Wi-Fi

- Current Wi-Fi Challenges

- The 802.11ax Vision — More than Just Speeds and Feeds

- Wi-Fi Use Cases

- Chapter 2 Understanding Key 802.11ax Technologies

- Multi-User (MU) Defined

- MU-OFDMA

- Subcarriers

- Resource units (RUs)

- MU-MIMO

- Spatial Reuse (BSS Coloring)

- Chapter 3 Looking at Other 802.11ax Enhancements and Design Considerations

- Target Wake Time (TWT)

- 1024-QAM

- New PHY Headers

- Design Considerations

- Chapter 4 Exploring the Aerohive 802.11ax Family

- AP630

- AP650 and AP650X

- Chapter 5 Ten Things You Need to Know about 802.11ax

- Glossary

- EULA

Table of Contents

Title Page

Copyright Page

Table of Contents

Introduction

About This Book

Foolish Assumptions

Icons Used in This Book

Beyond the Book

Where to Go from Here

Chapter 1 Recognizing the Business Need for Better Wi-Fi

Current Wi-Fi Challenges

The 802.11ax Vision — More than Just Speeds and Feeds

Wi-Fi Use Cases

Chapter 2 Understanding Key 802.11ax Technologies

Multi-User (MU) Defined

MU-OFDMA

Subcarriers

Resource units (RUs)

MU-MIMO

Spatial Reuse (BSS Coloring)

Chapter 3 Looking at Other 802.11ax Enhancements and Design Considerations

Target Wake Time (TWT)

1024-QAM

New PHY Headers

Design Considerations

Chapter 4 Exploring the Aerohive 802.11ax Family

AP630

AP650 and AP650X

Chapter 5 Ten Things You Need to Know about 802.11ax

Glossary

EULA