Start any video training course for FREE. More than 500 to choose from. Learn more
802.11ac: A Survival Guide

Errata for 802.11ac: A Survival Guide

Submit your own errata for this product.


The errata list is a list of errors and their corrections that were found after the product was released. If the error was corrected in a later version or reprint the date of the correction will be displayed in the column titled "Date Corrected".

The following errata were submitted by our customers and approved as valid errors by the author or editor.

Color Key: Serious Technical Mistake Minor Technical Mistake Language or formatting error Typo Question Note Update



Version Location Description Submitted By Date Submitted Date Corrected
PDF
Page 5
last paragraph

in the paragraph with the title "The Many Faces of Beamforming" , the 5th sentence is "the characteristics of the radio channel to wring out maximum performance " The sentence should be : "the characteristics of the radio channel to bring out maximum performance " that is "wring" is printed instead of "bring"

Note from the Author or Editor:
This is in the sidebar in chapter 1 titled "The Many Faces of Beamforming." Change the introductory clause in the identified sentence to: "Explicit beamforming is based on the transmitter and receiver exchanging information about the characteristics of the radio channel to extract the maximum performance from the radio channel based on channel quality measurements,..."

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 18
2nd paragraph

the second paragraph is "One of the ways that 802.11ac simplifies the selection of modulation and coding is that the modulation and coding are no longer tied to the channel width, as they were in 802.11n. To determine the link speed, knowledge of the MCS must be combined with the channel width to produce an overall data rate.". The error is in the line : "coding are no longer tied to the channel width" I think this should be like: "coding are no longer tied to the number of spatial streams"

Note from the Author or Editor:
This report is in the section in Chapter 2 titled "Transmission: Modulation, Coding, and Guard Interval", subheading titled "Modulation and Coding Set (MCS)", subheading, first paragraph. Rewrite paragraph following Table 2-3 to read: "One of the ways that 802.11ac simplifies the selection of modulation and coding is that the modulation and coding are no longer tied to the number of spatial streams, as they were in 802.11n. To determine the link speed, knowledge of the MCS must be combined with both the number of streams to produce an overall data rate."

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 23

The line with error is "the number of required symbols is rounded up to the next highest value" This should be like "if the number of streams is odd, then the number of required symbols is rounded up to the next highest even number value" If the word "odd" is not used then the people may take it in a wrong way.

Note from the Author or Editor:
In the section "VHT Long Training Field (VHT-LTF)', change "the number of required symbols is rounded up to the next highest value, so a link with five streams would require six symbols" to "the number of required symbols is rounded up to the next highest even numbered value, so a link with five streams would use six symbols" (There are situations in which the standard has corner cases that are not important to the overall understanding of how the number of symbols in this field are selected, and I am trying to keep that long discussion out of the book.)

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 27
figure 2-9

There are 4 blocks in figure distinguished using a,b,c,d. The mistake is in C. The diagram has "2x" copy ..but it should be "3x copy" . Only then the total number of message bits become 117 ..that is (23+6)*4 + 1pad . Then the coded bits becomes 234. May refer figure 22-20 of standard "Draft P802.11ac_D5.0.pdf"

Note from the Author or Editor:
The commenter is correct. Change Figure 2-9(c) from being: 23 bits | 6 bit tail | 23 bits | 6 bit tail | 23 bits | 6 bit tail | Pad bit to be 23 bits | 6 bit tail | 23 bits | 6 bit tail | 23 bits | 6 bit tail | 23 bits | 6 bit tail | Pad bit where the first (23 bits | 6 bit tail) is white, and the 3 remaining (23 bits | 6 bit tail) are shaded, and each labeled with a copy. Since this involves a new figure, I will proofread a new figure from the art department.

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 27
figure 2-9

As I have already mentioned, block C of the figure 2-9 has mistake . This should given as 3x but in the picture it is "2x" copy. The block D is just a repetition of block C two times. So the mistake has just propagated to block D.

Note from the Author or Editor:
The commenter is correct. Once 2-9(c) is fixed, then 2-9(d) will need to change as well. The essence of 2-9(d) is that it is two copies of 2-9(c) back to back, but, as the erratum observes, 2-9(c) is wrong.

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 29
29

the error is in figure 2-11. the diagram contains : phy padding -> scrambler -> BCC encoder parser -> encoders -> segment parser -> segment parsers This should be like : phy padding -> scrambler -> BCC encoder parser -> encoders -> encoder parser -> segment parsers May refer figure 22-11 of standard "Draft P802.11ac_D5.0.pdf"

Note from the Author or Editor:
Change figure Figure 2-11 from PHY padding -> scrambler -> BCC encoder parser -> BCC encoders -> segment parser -> segment parser -> segments -> ... to PHY padding -> scrambler -> BCC encoder parser -> BCC encoders -> stream parser -> segment parser -> segments -> ... That is, change the long vertical "segment parser" to "stream parser"

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 42
heading of last paragraph

the heading is "Rx and Tx VHC-MCS Map (16 bits each)" this should be like "Rx and Tx VHT-MCS Map (16 bits each)"

Note from the Author or Editor:
The erratum is correct: "VHC-MCS" should be "VHT-MCS"

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 67
last paragraph (note number 6)

the error is in sentence "the NDPA and NDP frames require about 100 ms" I think, it is not 100 milli sec ..it is 100 micro seconds

Note from the Author or Editor:
In chapter 4 footnote beginning "Timing for a sounding exchange is determined mainly ...": Change sentence reading "After gaining control of the channel, the NDPA and NDP frames require about 100 ms." to read "After gaining control of the channel, the NDPA and NDP frames require about 100 microseconds."

Murali  Sep 22, 2013  Jul 17, 2015
PDF
Page 72
Last paragraph

The maximum transmission length is defined by time, and is a little less than 5.5 milliseconds; The original text states that it is ...less than 5.5 microseconds.

Note from the Author or Editor:
Change sentence in chapter 3, section "The MAC" reading "The maximum transmission length is defined by time, and is a little less than 5.5 microseconds." to be "The maximum transmission length is defined by time, and is a little less than 5.5 milliseconds"

Anonymous  Jun 17, 2013  Jul 17, 2015
Printed
Page 120-1

Comment from a reader that requires clarification: pages 120-1 state that 11ac does not provide the capability to control data rates in the same way that 802.11a/b/g/n did, stating that "[t]he 802.11ac protocol does not provide the capability to control individual data rates. The only choices available in the protocol are supporting MCS 0–7, MCS 0–8, or MCS 0–9." Readers have taken "MCS" to refer to the MCS code used in both 11n and 11ac, though the two are different. This paragraph should clarify that it is referring only to 11ac data rates, not earlier (a/b/g/n) rates. Products will give you control over older data rates, but not 11ac data rates.

Note from the Author or Editor:
Change text of warning box from "The 802.11ac protocol does not provide the capability to control individual data rates. The only choices available in the protocol are supporting MCS 0–7, MCS 0–8, or MCS 0–9." to "Unlike 802.11n, the 802.11ac protocol does not provide the capability to control individual data rates. In 802.11n, all 76 MCS rates could be individually selected. 802.11ac uses a different method of determining data rates and has a much smaller MCS set. In 802.11ac, only three choices are available: MCS 0–7, MCS 0–8, or MCS 0–9."

Matthew Gast  Aug 22, 2014  Jul 17, 2015
PDF
Page 999
not sure...online version

In the section 802.11ac Data Rate Matrix (not sure of the page no, read the online version) it is mentioned that "MCS 9 is not allowed for 20 MHz channels, as will be described in the next section." while the description is correct in the next section, as per 802.11ac-draft 5.0 MCS 9 is valid for 20MHz only for 3 spatial streams.

Note from the Author or Editor:
The location of the report is a footnote to Table 2-4. Change table footnote to read: "MCS 9 is not allowed for a single stream using a 20 MHz channel, as will be described in the next section."

Chaitanya T K  Aug 14, 2013  Jul 17, 2015
Other Digital Version
1870
table 5-1

*For Kindle Version, Table 5-1. Under column Wave 1, different datarate are listed for "Typical 11ac speed" as well as "Maximum 11ac speed"; however, they're both listed with the same condition "80Mhz, 3stream, 256 QAM". Looks like one of them is clearly wrong.

Note from the Author or Editor:
Change wave 1 typical 11ac speed from "867 Mbps (80 MHz, 3-stream, 256-QAM)" to "867 Mbps (80 MHz, 2-stream, 256-QAM)" -- that is, change "3-stream" to "2-stream"

Frank Seto  Nov 17, 2014  Jul 17, 2015