Sunday, May 31, 2009

Broadband Speeds Around the World

No wonder I want to go over to Europe for awhile.
Perhaps I can get some decent Internet speeds while I'm there.

Perhaps the next trip needs to be to Japan and South Korea, eh?

Look how pitiful the US is on this graph. We should be ashamed.
And my Broadband connection at home is even worse that the graph. This is on a Sunday afternoon with little load on the local POP. Usually it's way under 3MB.Here's a link to the BBC article with a supporting map.

Saturday, May 30, 2009

Family Vacation to Europe

I'll be leaving for a two week family vacation to Paris and London. So this blog will be on 'hiatus' for awhile.

In the mean time, my personal blog over at will have the latest on my personal life and vacation.

Looking forward to a bit of a break...


Thursday, May 28, 2009

WiFiJedi's Blog on Pre-Shared Keys

I participated in a virtual roundtable discussion with some other tech savvy minds over at WiFiJedi's (Douglas Haider's) Blog.

The topic was Pre-Shared Keys and some of the new techniques Aerohive and others are bringing to the table. You can find the discussion here.

Thanks to Bruce and Ken for their comments.

Monday, May 25, 2009

Want, Don't Want, Don't Care - Meeting Design Specs

The goal of wireless networks is to provide an appropriate and workable RF implementation for the accurate transmission of data across a wireless medium.

To this end we work hard to get the correct number of access points with the proper power and channel settings using the best antenna patterns to cover the area we are interested in. In the simplest terms, there are three design specs to consider.

First there is the 'Want' - what we are designing for.

Second - the 'Don't Care' - the level of RF that we don't care about.

Third - In between the above two items - 'Don't Want' - where we find same-channel (co-channel) interference.


In the ‘old days’ when we employed the ‘AP on a stick’ method of site surveys in a pre-deployment mode, trying to come up with the best possible design, we’d end the survey with a design showing access points and their ‘coverage’ patterns. (sometimes called a heat map – though it had absolutely nothing to do with heat)

In this ‘AP on a stick’ process, after placing an access point in a temporary position we’d walk away until we reached the lower limit of our design goal. Perhaps -70dB or -67dB… then we’d stop. We met the design goal in that direction, so we’d stop.

But the RF energy projecting from the access point in question did not stop, it kept going. Since we never completed the Site Survey to the end of the radiation pattern, our designs did not, and could not, tell us where we’d run into interference with other access points.

This would give us what we wanted… Thus this is the WANT area.

The want area is normally defined to meet a specific design requirement based on the devices we’re designing for. Perhaps a -67dBm for voice, or a -75dBm for a hand-held scanner device.

This is the ‘easy’ one. Remember “Coverage is Easy”. See other article on “How to Spec your Physical Layer”

Coverage patterns looked something like this, with nice simple circles all lining up in neat rows.

NOTE: the -67dBm, and -86dBm used in the following examples are SAMPLES ONLY - Not indicative of any specific design!!

Don’t Care

Lets talk about the second RF design consideration next. This is the area where there is RF radiation, but at a level that is below the threshold of our device to actually use.

I call it the DON’T CARE area. In the don't care area, there is too little RF to make the client (STA) stop and wait for another client or access point to finish talking.

In other words, the amplitude of RF signals in this area are too low to be considered in the frequency’s collision domain.

With AirMagnet Survey, we can raise the color bar on the right side to make the areas with signals weaker than a given threshold turn grey.

This is usually set to -85dBm, but some devices are more sensitive and you might need to set your Don’t Care to -90dBm.

Don’t Want

Now we get to the difficult one. This is the one we normally don’t even measure in an ‘AP on a Stick’ survey.

This is the one that really causes a lot of problems.

One vendor draws their graphics to explain this, as shown in the following diagram. Note the WANT area is inside the dark circle, and the RF that is less than the desired goal still continues to radiate, causing interference and a large collision domain to all devices within the larger circle.

The trouble isn’t when two access points are next to each other. Since we have channels 1, 6, and 11 to use as non-overlapping channels, we can have a little ‘buffer’ between the same channels.

The problem starts when we don’t ‘look’ to see where the DON’T WANT area is in our survey. We never notice the access point's RF that is less than what we want, which continues all the way past the buffer zone and into the next sam- channel access point's space.

One graphic from a vendor details it like this.

This graphic shows that you must keep at least a 19dBm difference on the same channel from the ‘want’ to the ‘don’t want’ areas.

Another way to look at the situation between same-channel coverage pattern overlaps looks like this.

I ran a little online survey, and folks were just about evenly split between the above graphic and the following graphic.

I think an easier way to explain this situation is to turn the graphic on its side, like this.

Leaving the access point on the left, the RF propagates and looses RF energy along the way until it reaches the design goal, or the want line. We normally stop at this point in our surveys, but you must continue on to see where the RF continues.

The signal degrades and attenuates as we go further to the right, eventually reaching the level at which we no longer care. This is the don’t care line.

In between the access point on the left and the access point on the right is the area that is below the design goal threshold. This area should be covered by the other two access points on channels 6 and 11.

Coming back from the right, we have the same thing. The access point on the right on channel 1 starts strong, and as we move to the left, continues to get weaker until it reaches the design goal (want). After that, there is still RF on channel 1, but it is below our goal, and thus falls into the DON’T WANT area.

Another name for the don’t want is 'Interference.' If the two access points on channel 1 are too close, the signal from the right AP will interfere with the signals from the left AP.

In order to get access points on the same channel closer together (get the angles of the dropping signals to be steeper), you must lower the power.

Higher power gives you a longer ‘tail,’ and lower power give you a shorter ‘tail’.

Setting AirMagnet AirWise Interference Settings

In AirMagnet AirWise, there is a feature that allows you to visually show where interference meets or exceeds the design parameter. Remember, different devices have different design parameters.

To set the Want, Don’t Want, and Don’t Care values in AirWise we need to re-label them to meet the AirMagnet vocabulary.

The end of the want area is the same as your design goal for Minimum AP signal strength required.

The end of the Want value IS the start of the Don’t Want area (if it is below our want, it must be our don’t want) In AirWise, this is labeled with a weird English phrase of “Interfered APs: Exclude APs signal if strength is weaker than.”

The end of interference, where the signal is below the threshold of causing any harm, is called the Don’t Care. In AirWise, this is labeled with a second instance of the phrase “Interfering APs: Exclude APs signal if strength is weaker than.”


So there you go; simple, easy terms to define where you Want RF, where the RF signals on a specific frequency will cause interference -- Don’t Want -- and the area where the signal is too weak to make a difference -- Don’t Care.

Keith Parsons, CWNE #3
The WLAN Iconoclast
keith at
May 24th, 2009
Orem, UT, USA

Additional Article for Support of WLAN Site Surveys
- 7 Rules for Accurate Site Surveys
- How to 'Cheat' Using Survey - Don't be a Victim
- How to Properly Analyze Survey Data
- The Fallacy of Channel Overlap
- Predictive Survey vs Onsite Survey - What's the Big Deal?
- How to 'Spec' your Network's Physical Layer
- Want, Don't Want, Don't Care - Meeting Design Specs
- The Truth about SNR - Where Did that 'N' Come From Anyway?
- What is an Access Point Anyway - Hub, Bridge, Switch or Router?
- Passive vs Active - What's All the Fuss About?
- The False God of dB
- Meeting All Device Design Parameters

Never go network on me, kid...

Monday, May 18, 2009

What plug goes to what country?

Ever have the trouble of remembering which of many power plugs to take depending on what country you are traveling to? Those 'multi-country' ones are so large! I'd rather just take the smaller ones that I need.

I found this
site and graphic that makes it much easier.

Sunday, May 17, 2009

Update on Dell Mini 9 - Hackintosh

I've been quite pleased with my little Dell Mini 9 - loaded with Apple Macintosh OS X.

The couple of little things that bothered me, namely the smaller keyboard, and the lack of the standard Macintosh two-finger scrolling and two-finger right-click.

Well, this week I did an update to the OS X operating system to the latest 10.5.7. It totally crashed the little guy... until I went online and learned a couple of 'tricks' on how to let the software/hardware find itself all over again. Now we're fine!
In addition - and to my great surprise - I also found the latest drivers that allowed me to make the little Hackintosh's trackpad act just like a real Macintosh! I now have two-finger scrolling and two-finger right-clicks working. Yea!

No software is going to make this little keyboard get bigger all of a sudden - so I guess I'm stuck with that.

The little Hackintosh makes a great second computer. I take it on all my trips. I've pre-loaded the 64GB Solid State Drive with a bunch of TED Talks, Movies, etc. so it's a small little lightweight entertainment device for use on the plane.

In addition, it has an SD slot on loaded with even more movies on a 16GB SD card.

This has been a very fun little project!

On her trip to NYC with the High School Fashion Team, my daughter used it as in-flight entertainment, and to check her e-mail and update her facebook page during the trip. (WiFi in the hotel worked great)
Since I've got all my 'important' stuff like Calendar, Contacts, E-mail, etc. all sync'd to Mobile Me - it was a simple exercise to get the Hackintosh to also sync to Mobile Me. Now it is a nice 'backup' laptop if anything happens to the 'big brother' (my main machine - the Macbook 13" Unibody).

And for everyone reading this - Backup your data today!
a quick message brought to you by our sponsor... Your conscience)

If you'd like your own Dell Mini 9 Hackintosh, just drop me a line and I do my best to help out.

From my Twitter posts - or @keithparsons

Dell Mini9 Hackintosh *lives* once again. Just had to do a bit of 'tweaking'. Yea! - Instructions here

Hackintosh is even better than before! Now with 2-finger scrolling, and 2-finger right click! Yea! Instructions here

Saturday, May 16, 2009

Which Graphic Explains Co-Channel Interference Best?

I've been teaching WiFi for many years now. And one concept folks seem to have a hard time with is co-channel interference. Not that there *is* interference, that's pretty obvious, but at what level does co-channel interference actually start to 'hurt' the Wireless LAN?

I've started to call these areas 'Want' - 'Don't Want' - 'Don't Care' - but the concept is still the same.

Question: At what point does another device on the same channel equate to a 'collision domain'?

So I'm asking for the reader's help in deciding which of the following graphics make more sense?

Which should I use in classes?

Thanks for your help!



A - Multiple small circles

B - One large circle

C - Multiple large circles

D - Wedges

Thursday, May 14, 2009

Gap-Minder - World Statistics

I was watching a TED presentation this evening on my computer and experienced a new 'view' of the world's AIDS epidemic, but shown graphically - with animated data. It was very enlightening!

The FULL data set, not just AIDS, but education, life expectancy, income, births per woman, and many many others are all available. But best of all there is an easy-to-use interface that allows one to pic the variables, and then watch how things in the world have changed over the last 200 years.

This is a *fantastic* tool to learn and understand differences in countries, cultures, and how we all fit in this world. It's amazing to see how the world has changed over time.

There is something about having the freedoms, liberty, captialism, etc. that has allowed this 'winning' way. The US is NOT the best at everything - this data from world statistics shows that. We have problems and issues - that's true - but I'm pretty glad to be an American anyway.

spend some time learning - and I mean that - LEARNING from the historical data and statistics at this site. It will be good for you to think about the 'whys' of some of these.

Here's the

A couple of places to start - AIDS -vs- Income, Number of Children per Woman -vs- Income, Life Expectancy over time, just to get you started.

Enjoy - and please share your insight you learn from evaluating this information. Why does the world work like this?

Some TED Talks that might help

Best Stats You Have Ever Seen
Insights on Poverty
Truth about HIV

Saturday, May 2, 2009

The False God of dB

In the Wireless LAN (WLAN) world, we have started to worship in front of the False God of dB.

Books, white papers, study guides, and design manuals have touted the value of the RSSI (dB) so much we have used this as a sole way of designing and evaluating our Wi-Fi Networks. dB is a false god and we need to mature and move past having ‘Signal’ be our main goal in WLAN designs!

Signal is Immensely Important!

I’m not in the least bit saying Signal levels – RSSI – is not terribly important in our WLAN designs. It is critical, required, and even mandatory. But RSSI alone is not sufficient.

To give an analogy of a wired network, consider connectivity. It’s the ability of copper pairs to conduct electricity at a certain level, and it’s paramount in getting wired networks to work.

dBm is to a WLAN what connectivity is to a Cat6 cable. It is a base level requirement. Without it, nothing works.

Compared with Category 6 Cabling

But just as connectivity in a Cat6 cable isn’t the only factor in determining whether or not a cable run meets the design characteristics, RSSI (signal strength) isn’t the only factor in determining whether or not a wireless network meets its design characteristics.

Cat6 cable actually means cable that meets the Category 6 physical requirements as defined by the TIA/EIA organization. These requirements include:
• Connectivity
• near-side crosstalk
• far-side crosstalk
• pin-outs
• cable twist ratios
• and more
Much more than simple connectivity alone!

In a WLAN design, a certain level of signal strength is required, but signal strength alone is not sufficient. We have yet to find a wireless industry group to take on the responsibility of defining the specifications for a ‘voice-grade’ WLAN or a ‘video-grade’ WLAN, let alone even a generic ‘data-grade’ WLAN. We are still in the early stages, and each vendor is still defining their own specifications.

WLAN Design Specifications

I’ve started a new project working with other CWNEs to develop a WLAN Design Matrix to help codify and analyze the various vendor recommendations for design parameters to make their client devices work on WLANs. As an example, VoWiFI devices need specific dB, overlap, jitter, latency, packet loss, DTIM intervals, etc.

In this early stage of the process, we have already defined nearly one hundred unique identifiers and specifications collected from the various WLAN vendors. Of course the first one is always ‘RSSI’ – or Signal Strength defined in dB - but that is merely a baseline. On top of the Signal Strength, there are many more categories of WLAN requirements.

Some vendors require an ‘Overlap’ (see my blog post on the fallacy of channel overlap ). Other vendors specify the co-channel interference at very specific levels. Still others add data rate support, number of devices per AP, minimum MCS requirement, and many more.

Some of the requirements are based on designs for the STAs (clients), and others are specifications for the Access Points and cabling. Together all these requirements must be met in order to deliver a WLAN infrastructure that will work with the vendor’s devices.

Do you know all the design specs for your Wi-Fi enabled client devices?

How can you tell if your WLAN meets those specs?

Car Analogy

In my consulting practice and WLAN training classes, I like to give the following analogy concerning the design of WLANs.

While working with a vendor in the auto industry in Detroit, I was frustrated by their lack of understanding of why their WLAN, which was originally designed for data and was currently working well, was failing so miserably as a VoWiFi network. My explanation led to the following analogy:

You are an automobile designer, and your boss comes to you and asks for a new vehicle design. A vehicle is defined as a system of wheels/tires, engine/transmission, seats, frame, and chassis. They have asked for a vehicle that can carry two adults, travel at freeway speeds, and carry a 2200 lb payload. You might answer, “That’s easy. I’ll build you a truck!” The truck would meet all their design specs, and everyone would be happy.

If, at a later time, your boss asks you to design a vehicle that can do 0—60 mph in less than 5 seconds, with great cornering characteristics and a very low drag coefficient, then you would likely design a small, lightweight, high-powered, sports car. All would certainly be pleased.

Finally your boss requests a vehicle that can comfortably carry seven adults with their luggage, has lots of cup holders, and allows easy entry. You would likely design them a mini-van. Again, all would be pleased.

The problem surfaces when the truck owner thinks to himself, ‘Since my truck is a vehicle, it should go from 0-60 mph in 4.2 seconds.’ Almost as an afterthought the truck owner asks you to make his truck become a fast sports car.

Sure, it’s possible, but at a significant cost. You could take out the old engine and replace it with a much stronger one, but since the truck was originally designed for carrying a heavy payload, it is built with a heavy suspension and dual-I-beam construction. In order to get it to have a fast race time, you’d also have to replace many of the ‘guts’ with carbon fiber composite parts!

Even after all that work, it would no longer be a good truck, nor a fast sportscar.

Certified Magazine Readers

Sometimes our bosses are like the bosses in the above vehicle analogy. They have read something in a magazine about WLANs doing Voice over IP, Video, or even Location Tracking. They come to the IT folks asking to simply ‘add’ this feature to the existing WLAN infrastructure.

Many of the design characteristics of these newly requested services require, indeed demand, mutually exclusive design goals!

For example, the VoWiFi WLAN might be the sports car design since it doesn’t carry a lot of payload. Yet the VoWiFi network needs to have very high tolerance and characteristics for the small set of data it does carry.

For example, VoWiFi vendors define the following detailed specifications:

  • Minimum RSSI >= -65dBm
  • Backup/Second AP at >= -65dBm
  • Signal to Noise Ratio > 19dBm
  • Maximum Noise Floor < -90dBm
  • Maximum Jitter <5 msec
  • Maximum Latency <50 msec
  • Maximum Packet Loss <1%
  • Total End to End Delivery <150 msec
  • DTIM Interval 2
  • Channel Overlap 25%
  • Roaming Time <50 msec
  • Required Data Rate 1Mbs
  • Co Channel Separation > 19dBm
  • Roam to 2nd AP if >= 5dBm higher
  • Roam back to 1st AP if >= 10dBm higher
  • 802.11e QoS Required
  • Fast Roaming Required
  • Multicast Enabled Required
  • Specific Codec Required
  • Maximum Calls per AP <= 7

  • And even more…

Obviously the minimum RSSI in dB must be met, but note all the other detail specifications that also must be met.

Designing networks with just dB in mind will no longer work!

Web Surfing and large file transfers are more concerned with the size of the ‘pipe’ and can easily live with retries and temporary changes in the quality of the pipe. (the Truck)

RFID tagging and location tracking needs to have lots of access points in specific locations to support accurate triangulation, but those extra APs can cause more co-channel interference and make larger collision domains, thus lowering throughput. (the Mini Van)

Just because your boss read in a magazine about another company’s fast sports car, doesn’t mean your company’s truck will be a good vehicle to use in drag racing!

Know Your Design Requirements

My clients constantly amaze me when I ask them to specify (list) the design requirements of their WLAN devices. They rarely know what the design characteristics are for their own devices!

I ask you: If you don’t know what you are designing your WLAN for, how can you know when you’ve achieved the proper WLAN design?

In the automobile industry, no designer would willingly take on the job of designing a ‘vehicle’ without first understanding the detailed characteristics that are being requested.

In the wired network world, no ‘cable-puller’ would start pulling barbed-wire to each desktop! Barbed wire will easily meet the ‘connectivity’ goal, but obviously not any of the other Cat6 specs!

Yet somehow in the wireless LAN world, we allow ourselves to do just that. We design our WLANs without specific design goals, we design for only ‘coverage’ (dB), and then we later wonder why the WLAN doesn’t work…

If you don’t know the specific design parameters your client stations require, your WLAN can NEVER meet those goals!


Yes, Yes, Yes, and Yes… dB is VERY IMPORTANT! But it is NOT the ONLY goal around which you should be designing.

You don’t design wired networks with ‘barbed-wire’; so don’t design your WLANs with ONLY dB!

Keith Parsons, CWNE #3
dThe WLAN Iconoclast
Keith at
May 2nd, 2009
Orem, UT, USA

Additional Articles for Supporting WLAN Site Surveys
- 7 Rules for Accurate Site Surveys
- How to 'Cheat' On A Survey - Don't be a Victim
- How to Properly Analyze Survey Data
- The Fallacy of Channel Overlap
- Predictive Survey vs Onsite Survey - What's the Big Deal?
- How to 'Spec' your Network's Physical Layer
- Want, Don't Want, Don't Care - Meeting Design Specs
- The Truth about SNR - Where Did that 'N' Come From Anyway?
- What is an Access Point Anyway - Hub, Bridge, Switch or Router?
- Passive vs Active - What's All the Fuss About
- The False God of dB
- Meeting All Device Design Parameters

Pronunciation of WLAN Acronyms

OK, I know I'm just being a bit 'picky' here... but I've found a correlation in a variety of industries with respect to how professionals pronounce a 'short-hand' version of an acronym versus the 'layman' way.

My wife is a Labor & Delivery Nurse, and they don't call the OB Docs 'awbzz' ('obs') - they call them 'O', 'B' doctors.

In the old days, when Apple Macintosh computers first came out the SCSI interface wasn't called 'sexy' (like I heard many uniformed people use) - nor was is 'S', 'C', 'S', 'I' either. It was just 'Scuzzy'.

In our industry of Wireless Networks, we too have acronmyns that sometimes get 'shortened' - No one calls the WWW in front of a URL 'wwwwwwaaah' - pronouncing the letters, you call it 'W', 'W', 'W'...

WLAN is 'W', then 'lan' - Get the picture? - you could also say this one as 'Wireless', 'lan'. But never 'wha-lan'.

Now lets go over the ones that the folks who work at Best Buy always seem to get wrong.
If you are using the wrong pronunciation... please stop. That is unless you *want* to work at Radio Shack or Best Buy...

AP - pronounced 'A', 'P'... this is not a 'wap', or an 'app' - an Access Point is NOT an applciation, and it is not the sound of a flag 'wapping' in the wind - wap, wap, wap... An Access Point is an 'A', 'P'.

Wireless Access Point - this is an Access Point (do you know of other networking devices that are Access Points that are not wireless?) - call it an 'A', 'P'. This is NOT a WAP... it is an 'A', 'P'.

VoIP - this one can go two ways. Either 'voip' ('vo ee p') - starting to enter common nomenclature... or just spell it out 'V', 'O', 'I', 'P'.

SSID - a Service Set Identifier - pronounced 'S','S','I','D' - it is not a 'sid' - a 'SID' is a term used to describe the unique identifier on a Windows Hard Drive... it has nothing to do with Wireless LANs. If you want the plural, it is 'S', 'S', 'I', 'Ds' - put the 's' sound after the last 'D'.

MAC Layer broadcast address isn't 'fffffwwff' - but 'F', 'F', 'F'...

Normally when you have to say a MAC Address out loud - just use the last four digits (counting from the right side) - and say them out loud - one letter or number at a time. To be very sure that your recipient heard it correctly - you could also repeat it, but this time use the international phonetic codes for the letters. Something like 'One', 'Foxtrot', 'Alpha', 'Four' for 1F:A4.

(don't know the codes? - spend an free moment sometime just memorizing them. You will sound more professional if you use the correct terms rather than making up some word for the letter 'N' on the fly... "like N as in never")

In the CWNP program we try to use the 'correct' terms for everything. The 'Rosetta Stone' article was one step toward making industry terms shared and to mean a specific thing.

Is there any other terms that you've heard mis-pronounced?

How to find a WiFi Antenna - Bruce Hubbert

Finding the right Wifi Antenna is a pain in the connector. When I meet with WLAN managers the most often asked question about antennas is, "Where can I get one that is camouflaged or hidden in some way?" Most antenna sales or manufacturers websites are really bad. Either these websites haven't been changed since 1997 or the are broken or just plain unusable.

I get a lot of requests for sources of antennas. Not high gain, site to site antennas. Not parabolic or Backfire. Not a 4 foot long ultra-high gain omni.

All the requests I get are for one simple thing. A disguised antenna. This could be an antenna that looks like a smoke detector, an alarm light, a speaker grill or anything except a wifi antenna. In almost every case the antenna must do 2.4GHz and 5GHz. More recently it also must do 802.11n.

How hard is it. I am pretty good at Google but I have a real hard time finding one. Everytime I look I get pages that look like this:

Now why is that? I searched for "camouflaged WLAN antenna" and I get the above. When what I want is this:
Anyway, here a short list of websites I have found for wifi antennas. If you have a better resource, especially for camouflaged antennas, please post a comment.





Pasadena Networks


WiFi Antennas|| RadioLabs