What Do You Know About WLAN Data Rates?

I’m doing a talk in a few weeks about Wi-Fi data rates and how they affect WLAN performance.  Since I am still in the research stage, I’d like to ask my blog readers to answer a few questions below about data rates?   To respond, use “Leave a Reply” below or you can DM me on Twitter (@grcate) and we can exchange email addresses.

Data rates can really improve (or degrade) a wireless network and understanding them is a key feature in Wi-Fi technology.  I appreciate your feedback and look forward to your answers to these data rate questions.  Thank you for your input!

Wi-Fi Data Rates:

  1. What you would say in a twenty second elevator speech to answer the question, “What is a data rate”?
  2. What do most WLAN engineers NOT understand about data rates?
  3. You are designing a network and have freedom to set data rates. What rates do you set and why?
  4. When do you think it is good to keep low data rates supported (viz 6 Mbps for 5 GHz or 11 Mbps for 2.4 GHz—or even 1 or 2 Mbps) ? Why?
  5. If you set your AP at higher data rates (e.g. 24 Mbps), have you ever seen or heard of a client that can ‘force’ the AP to transmit at a lower rate? (I don’t think that can happen, but I have heard that it can occur.)
  6. What terms do vendors use for basic rates and supported rates. Example: some vendors use basic and mandatory rates as synonymous.  Some vendors say supported and optional rates are the same term.  Also, what do you normally set as basic and supported rates?
  7. What other areas in a WLAN do data rates greatly affect? QoS?  High capacity?  Mesh APs? Specific verticals?  Airtime fairness?  Others?
  8. A good reason to use higher data rates is to help get the user on and off the medium faster, which helps keep utilization lower. What is(are) another good reason(s) for using higher data rates?
  9. From what you know about 802.1ax, how will data rates be affected by this new PHY?
  10. What questions have I missed that I SHOULD be asking about data rates?

** Bonus question:  If you had to choose only one URL that really has helped you understand data rates, which one would that be?  (Yes, only one URL allowed—thank you!)










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4 responses to “What Do You Know About WLAN Data Rates?

  1. 1. data rate is the rate (and corresponding modulation) that AP and client agrees to communicate (keep it that simple for the audience)
    2. most people forget that a data rate corresponds to specific modulation. Lower data rate= lower modulation
    3. at least eliminate 1 and 2 Mbps, preferably disable 802.11b rates and set minimum to 12 Mbps
    4. in private Wi-Fi, I prefer to just eliminate 1 and 2 Mbps
    5. no
    6. –
    7. CCI will be reduced by removing lowest basic rates, it reduces airtime needed to transmit management frames, increasing data throughput.
    SSID overhead will be globally reduced, see http://www.revolutionwifi.net/revolutionwifi/2013/10/ssid-overhead-how-many-wi-fi-ssids-are.html?rq=overhead
    8. it is also good fo analyse the data rate selection algorithm of client devices. Sometimes, client devices are too conservative and tend to fall back immediately to the lowest data rate while it might be not necessary.
    9. no idea yet, not enough time spent on 802.11ax but it’s worthwhile looking at it.
    10. explain definitely the difference between management and control frames and which data rate each frame type uses.

  2. 1: speed at which the communications takes pace
    2: Modulation
    3: Depends ( based on your scenario in my opinion). If AP density is there to meet ‘nice’ cells then remove all below 12 in both bands. If not, then work around AP placement and RF coverage. Why -> air time efficiency
    4. Never seen lower OFDM rates hurt the over the air retry rate as much as not having it.
    5. Have not
    6.Unless AP deployment is sparse: Basic = 12Mbps @ 2.4 & 5
    7.QoS,HDX,ATF in my experience. Office spaces with lots of WVoIP and Video.
    8. still learning so my comments would be out of place.

    Bonus: http://www.revolutionwifi.net/revolutionwifi/

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