Wi-Fi: 802.11 Physical Layer Explained

Find out more about the 802.11 Wi-Fi Physical Layer

This helpful poster created by Tektronix (R) explains key parameters in the WiFi Physical layer, including 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac.

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WiFi Physical Layer Explained

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What Wi-Fi Parameters do we have to consider?

When building a Wireless Network Key parameters include:

  • Channel Allocation
  • Spectral Shape and Mask
  • Packet Information
  • Data rates
  • Modulation types
  • Transmitter Measurements
  • Channel and Centre Frequency

What is Wi-Fi 6? Wi-Fi 5? Wi-Fi 4?

Under its naming convention, the WiFi alliance calls 802.11ax Wi-Fi 6. 802.11ac is now WiFi 5, and 802.11n is WiFi 4. The idea, according to the WiFi Alliance, is to make matching endpoint and router capabilities a simpler matter for the rank-and-file user of WiFi technology.

Meanwhile it’s important to know that the Wi-Fi Alliance has not made up simpler names for all the 802.11 standards, so it’s important to be familiar with the traditional designations. Also, the IEEE, which continues to work on newer versions of 802.11, has not adopted these new names, so trying to track down details about them using the new names will make the task more complicated.

802.11b

Released in September 1999, it’s most likely that your first home router was 802.11b, which operates in the 2.4GHz frequency and provides a data rate up to 11 Mbps. Interestingly, 802.11a products hit the market before 802.11a, which was approved at the same time but didn’t hit the market until later.

802.11a

The first following the June 1997 approval of the 802.11 standard, this standard provided operation in the 5GHz frequency, with data rates up to 54Mbps. Counterintuitively, 802.11a came out later than 802.11b, causing some confusion in the marketplace because customers expected that the standard with the “b” at the end would be backward compatible with the one with the “a” at the end.

802.11g

Approved in June 2003, 802.11g is the successor to 802.11b, able to achieve up to 54Mbps rates in the 2.4GHz band, matching 802.11a speed but within the lower frequency range.

802.11n (WiFi 4)

The first WiFi standard to specify MIMO, 802.11n was approved in October 2009 and allows for usage in two frequencies – 2.4GHz and 5GHz, with speeds up to 600Mbps. When you hear the term “dual-band”, it refers to being able to deliver data across these two frequencies.

802.11ac (WiFi 5)

802.1ac-compliant devices operate in the 5 GHz frequency space. With Multiple Input, Multiple Output (MIMO) – multiple antennas on sending and receiving devices to reduce error and boost speed – this standard supports data rates up to 3.46Gbps. Some router vendors include technologies that support the 2.4GHz frequency via 802.11n, providing support for older client devices that may have 802.11b/g/n radios, but also providing additional bandwidth for improved data rates.

802.11ax (Wi-Fi 6)

Also called High Efficiency WLAN, 802.11ax aims to improve the performance in WLAN deployments in dense scenarios, such as sports stadiums and airports, while still operating in the 2.4GHz and 5GHz spectrum. The group is targeting at least a 4X improvement in throughput compared to 802.11n and 802.11ac., through more efficient spectrum utilization.

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IEEE 802.11ax: The new standard for Wi-Fi

The new standard 802.11ax for Wi-Fi goes beyond 802.11ac wireless

A new standard for high speed multi-gigabit WiFi is emerging.  Current WiFi products use chips based on the IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11 and IEEE 802.11ac standard have really only begun rolling out, an effort to deliver an enhancement called IEEE 802.11ax that promises to deliver faster and longer range Wi-Fi networks.

The up-coming 802.11ax is as an enhancement of 802.11ac in the unlicensed 2.4 and 5GHz bands of spectrum, and should be a natural upgrade. The upgrade will offer significant speed and range improvements.

IEEE 802.11ax Wireless Networking
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Technical Summary

IEEE 802.11 ax is a type of WLAN in the IEEE 802.11 set of types of WLANs. It is designed to improve overall spectral efficiency especially in dense deployment scenarios. It is still in a very early stage of development, but is predicted to have a top speed of around 10 Gb/s, it works in 2.4 and/or 5 GHz, in addition to MIMO and MU-MIMO it introduces OFDMA technique to improve spectral efficiency and also higher order 1024 QAM modulation support for better throughputs. Though the nominal data rate is just 37% higher comparing with 802.11ac, the new amendment will allow achieving 4X increase of user throughput thanks to more efficient spectrum usage. It is due to be publicly released in 2019.

Modulation and coding schemes for single spatial stream
MCS
index
Modulation
type
Coding
rate
Data rate (in Mb/s)
20 MHz channels 40 MHz channels 80 MHz channels 160 MHz channels
1600 ns GI 800 ns GI 1600 ns GI 800 ns GI 1600 ns GI 800 ns GI 1600 ns GI 800 ns GI
0 BPSK 1/2 4 4 8 9 17 18 34 36
1 QPSK 1/2 16 17 33 34 68 72 136 144
2 QPSK 3/4 24 26 49 52 102 108 204 216
3 16-QAM 1/2 33 34 65 69 136 144 272 282
4 16-QAM 3/4 49 52 98 103 204 216 408 432
5 64-QAM 2/3 65 69 130 138 272 288 544 576
6 64-QAM 3/4 73 77 146 155 306 324 613 649
7 64-QAM 5/6 81 86 163 172 340 360 681 721
8 256-QAM 3/4 98 103 195 207 408 432 817 865
9 256-QAM 5/6 108 115 217 229 453 480 907 961
10 1024-QAM 3/4 122 129 244 258 510 540 1021 1081
11 1024-QAM 5/6 135 143 271 287 567 600 1134 1201

Technical improvements

The 802.11ax amendment will bring several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1 GHz and 6 GHz. Therefore, unlike 802.11ac, 802.11ax will also operate in the unlicensed 2.4 GHz band. To meet the goal of supporting dense 802.11 deployments the following features have been approved.

Other up-coming Fast WiFi standards: 802.11ay

IEEE 802.11ax Wireless Networking
IEEE 802.11ax Wireless Networking

Users should not confuse 802.11ax with 802.11ay, which will work in the 60GHz bands.  The lower frequency bands 1-6GHz for 11ax will penetrate walls.  11ay will not.

What will 802.11ax be used for?

802.11ax is an upgrade for existing 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac networks, Many are enthusiastic about 802.1ax’s potential as a fixed point-to-point or point-to-multipoint outdoor backhaul technology, especially in light of scaled back fiber rollout plans by providers like Google and Verizon in the face of extraordinary costs associated with such implementations. Therefore 11ax will find applications outdoors as well as indoors.

Who is behind 802.11ax?

The IEEE task force leading the 11ax work includes representatives from major equipment and chipsets vendors.
In 2012 and 2013, IEEE 802.11 received various submissions in its Standing Committee (SC) Wireless Next Generation (WNG) looking at issues of IEEE 802.11ac and potential solutions for future WLANs.  Immediately after the publication of IEEE 802.11ac in March 2013, the IEEE 802.11 Working Group (WG) established Study Group (SG) High Efficiency WLAN (HEW)

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