Wednesday, April 2, 2014

10 Wi-Fi Terms You've Probably Been Using Incorrectly

Sometimes we fall into bad habits. Unfortunately, the improper use of terminology is quite common in the Wi-Fi industry. This can cause a great deal of confusion when people discuss technical topics. Therefore, as a Wi-Fi industry, I think we should start referring to the following terms using more accurate terminology so we are all on the same page.

Here goes:

  1. Over-the-Air Rogue APs - if it's not on your wired network, it's NOT a "Rogue AP" so let's start calling them Neighboring APs so we all know what someone is talking about rather than having to inquire each and every time someone mentions a rogue for clarification. And let's reserve using the term Rogue APs for when unauthorized APs are on the internal wired network.
    Correct Term: Neighboring APs

  2. Co-Channel Interference (CCI) - APs and clients that are operating on the same channel don't cause interference with one another, they contend for the same airtime and backoff if another one is transmitting. This is distinctly different from interference where a transmission cannot be properly decoded because the receiver can't distinguish the valid signal from noise.
    Correct Term: Co-Channel Contention (CCC)

  3. Collision - okay, here is one that most of you may not have really thought deeply about. Collisions don't actually happen on wireless networks (not in the traditional wired network meaning of the term 'collision'). Instead, the receiver simply cannot properly decode a valid signal because it can't distinguish it from the surrounding noise with the precision required by the modulation used.
    Correct Term: Interference

  4. Coverage Area - most Wi-Fi professionals refer to an APs coverage area as the physical area in which they intend for clients to connect to the AP, usually with an associated signal strength (such as -67dBm). However, the RF signal actually keeps going and can cause co-channel contention (see what I did there!) over a much larger area (usually out to a signal strength of around -85dBm). So, to refer to the area in which we expect clients to connect to the AP based on an RF design let's start using a different term such as Association Area and leave the term Coverage Area to refer to the area where CCC occurs.
    Correct Term: Association Area

  5. AES versus TKIP - this one is easy to get wrong, even for Wi-Fi professionals! Many times we interchangeably use AES, TKIP, and WEP to refer to the encryption on the wireless network. However, in so doing we confuse encryption protocols with cipher suites. For accuracy we should always mention like for like. CCMP, TKIP and WEP are all encryption protocols that we configure for a wireless network. Each of those protocols use a cipher suite to accomplish the heavy lifting: CCMP uses AES, TKIP uses RC4, and WEP uses RC4. Thanks to George Stefanick for bringing this up.
    Correct Term(s): Reference protocols (CCMP, TKIP, WEP) or ciphers (AES, RC4) but don't use them interchangeably

  6. 802.1x - I see this all the time in written material to refer to the IEEE 802.1X Port Based Network Access Control. Unfortunately, it should be used with capital letter 'X' since it is a (standalone) standard, whereas lowercase letters refer to amendments to standards (see here). So, whenever you reference it use the correct capitalization (802.1X).
    Correct Term: 802.1X

  7. WAP - many people use this term to refer to an access point and it's just annoying. It's just AP people. Referring to it as wireless AP (WAP) is just redundant.
    Correct Term: AP

  8. Antenna Gain in Decibels (dB) - many people refer to antenna gain in dB, which is incorrect. Decibels (dB) alone is a relative measurement and requires a point of reference. Instead, you should refer to antenna gain referencing either an isotropic radiator (dBi) or less commonly referenced to a standard dipole antenna (dBd). This establishes the absolute reference point for the measurement which actually gives it meaning.
    Correct Term(s): dBi or dBd

  9. 802.11b 1 Mbps and 2 Mbps Data Rates - do you reference all of the lower data rates of 1, 2, 5.5, and 11 Mbps as 802.11b? If you do, you've been using this amendment name incorrectly. The original 802.11 standard (802.11-1997) defined the 1 Mbps and 2 Mbps data rates as part of the DSSS PHY, as is generally referred to as 802.11 Prime. Then in 1999, along came the 802.11b amendment which added the 5.5 Mbps and 11 Mbps data rates as part of the HR-DSSS PHY. So, to be correct, when talking about 1 Mbps and 2 Mbps data rates you should reference 802.11-Prime (not 802.11b).
    Correct Term: 802.11 Prime (or 802.11-1997)

  10. 5 GHz Signals Attenuate Faster than 2.4 GHz Signals - it's common for many Wi-Fi professionals and writers to state that 5 GHz signals attenuates faster than 2.4 GHz signals in order to describe the common symptom that 5 GHz has less effective coverage area. However, this too is incorrect in most circumstances. 5 GHz signals attenuate through free space at the same rate as 2.4 GHz signals according to the FSPL (free space path loss) formula; it is not directly dependent on the frequency of the signal. Instead, the construction of the receiving antenna is a fractional multiple of the frequency to which it is tuned. This makes a standard 1/4 wavelength antenna for 2.4 GHz longer than a 1/4 wavelength antenna for 5 GHz, which causes a difference in antenna aperture. To put it simply, a 2.4 GHz antenna has a larger aperture than a similar 5 GHz antenna and can "capture" more of the signal as it passes by the antenna element.
    Correct Term: 5 GHz Antennas Have Smaller Apertures

Do you have any other terms that are misleading or misused and you think should be corrected? Drop a comment below!

Thanks,
Andrew

Monday, March 31, 2014

FCC Eases Restrictions on 5GHz UNII-1 Band

The FCC just made an unofficial news release of pending action that was approved at today's commission hearing which eases restrictions on the existing 5 GHz UNII-1 frequency band (5.150-5.250 GHz, Wi-Fi channels 36-48).

To quote from the news release (emphasis added by me):
By its action the Commission significantly increased the utility of the 100 megahertz of spectrum, and streamlined existing rules and equipment authorization procedures for devices throughout the 5 GHz band.
This ruling makes the following changes to the UNII-1 band:
  • Removes restriction on indoor use. Now the UNII-1 band can be used outdoors as well. This will allow use of the band by WISPs and for outdoor hotspot deployments which are rapidly growing with the support of telecommunications and cable operators.

  • Increases the allowed power output. The power output had been lower in UNII-1 than other 5 GHz UNII bands due to indoor-only use (50mW IR, 200mW EIRP). Exact details of the new power limits have not been released, but it is fair to assume the UNII-1 band will have similarly capable power output as UNII-2/2e bands (250mW IR, 1W EIRP) the UNII-3 band (1W IR, 4W EIRP). (Update after reviewing Commissioner Rosenworcel's statement and Commissioner O'Rielly's statement it appears the new power limits will be higher and align with the existing UNII-3 band).
And an additional change to all UNII bands (particularly UNII-2 with DFS restrictions):
  • Modified equipment authorization rules that requires manufacturers to secure devices against unauthorized software changes and illegal uses. Commissioner O'Rielly's statement makes it pretty clear that this is directed toward manufacturers of outdoor WISP equipment that allowed easy circumvention of DFS radar checks that resulted in several instances of TDWR interference and forced the FCC to restrict all Wi-Fi use in the TDWR band (Wi-Fi channels 120-128 are affected). For those interested, here is a list of Enforcement Actions against TDWR interference. Notable repetitive offending manufacturers include Motorola Canopy and Ubiquity Networks equipment. 
It should also be noted that the the FCC Office of Engineering and Technology (OET) analyzed the UNII-1 changes with stakeholders to come to an acceptable outcome regarding the risk to existing licensed use for Satellite Operators (Globalstar) in the 5.150-5.250 GHz band (see the U.S. Frequency Allocation table).
The aim of today's regulation changes are to streamline the rules surrounding 5 GHz UNII bands to allow easier adoption and integration of all available spectrum into devices. I would anticipate future rulings surrounding DFS bands to make further strides in this area as well, since DFS support and adoption has been lackluster to-date and a hindrance to utilizing all available unlicensed spectrum.

Keep a close eye on future FCC rulings in the 5 GHz band around the end of this year or early 2015, when an ongoing study into adding an 195 MHz spectrum to the unlicensed 5 GHz bands should be completed. You can read more about that initiative in 'Wi-Fi May Get A Capacity Boost, Thanks to the FCC'.

Cheers,
Andrew

Thursday, March 13, 2014

WLAN Professionals Conference Videos Posted

Videos of presentations from the WLAN Professionals Conference that occurred Feb. 10-12th in Austin, TX have now been posted by Keith Parsons and the Prime Image Media team. The conference was chalk-full of great content, both technical and business focused, by some of the best experts in the industry!

I had the honor of presenting a session titled "Going Beyond RF Coverage: Designing for Capacity." The topic is about how to define, measure, and plan for capacity needs for ALL wireless networks (not just high-density environments - for which no commonly accepted definition even exits). I provided a bit of background on why I decided to give my presentation on this topic in my previous blog "Mind the Gap in Your WLAN Design" and you can download the full presentation and related material.

Check it out!


WLAN Pros Summit 2014 | Andrew Von Nagy Beyond RF Coverage 1 from Keith R. Parsons on Vimeo.

Be sure to check out all of the great presentations from the event on the WLAN Pros website and Keith's Vimeo channel!

Cheers,
Andrew