Easy way to mount a Cisco 3602 to the wall with off the shelf materials

Here is an option on how to Cisco AIR-CAP3602I-A-K9 access point to a wall from materials you can easily purchase from Home Depot.  (ie, I have done all the homework already)  All for under six dollars.  Check out last screen capture for the receipt.

The access point was designed to be ceiling mounted in carpeted office environments, ten feet above the finished floor.  That said, there are areas that we to provide Wi-Fi coverage to that do not fit the above mentioned description – such as manufacturing, warehouses and older buildings.

In these cases, we have nowhere to mount the access point.  Ceilings may be 30 feet, which is not where we want to install the AP.  In these cases we need to install the AP on a wall, approximately ten feet above the floor.  The AP does not come with a wall mount bracket that will mount it parallel to the floor, so I have come up with an off-the-shelf solution from Home Depot.

The two things from the hardware section.  The first is a 6” Corner Brace bracket, the second is a bag of 8-32x1/2 screws.

The bracket has some holes that almost line up perfectly with a few of the pre-drilled screw holes.  It isn’t perfect, as you can see there is a slight angle, however it fits and looks fine when the AP is installed.

 

Aligning a P2P Wi-Fi bridge link

I was recently called out to investigate a Wi-Fi bridge link that was being accused of being the culprit of a myriad of network problems.

Upon arrival on site, I noticed that the main site’s Wi-Fi bridge was sitting on channel 161, and that channel was overpopulated since there were two access points in the building, both on channel 161.  I moved the building’s access points to the UNII-1 band, and changed the bridge’s channel  to help alleviate some of the congestion since there was another access point on that channel across the street.  These three screenshots are  before I made any changes:

Note that the bridge is capable of achieving a 54 mb/s data rate, however only 3% of all the packets are traveling at that rate – and 92% of them are data packets.  The busiest data rate is the lowest data rate – with 72% of the traffic at that rate.  Hmmm….

Also, a quick screenshot as a baseline..

 

After coming up with a channel/power plan, I made the necessary changes.  The following three screenshots are post channel plan change.  I saw immediate improvement after my change.  The first screenshot is of the devices now on their newly assigned channels.

With the bridge’s new channel assignment, there is far less noise in the environment and the SNR increases.  This allows the bridge to negotiate a higher data rate.  On channel 153, the bridges are now able to send 78% of the data at 18 mb/s.  A dramatic increase over what I saw when sharing the same channel with other 802.11 devices.

 

Now that we have some of the low hanging fruit taken care of, it is time to check the out the line of site between the two dish antennas that are making this 2.79 mile Wi-Fi link.

When I did the calculations for this link, I discovered this link should easily handle 54 mb/s since it is less than three miles and it is using high gain antennas.   But it wasn’t, and here I am… (onsite)

I went up on the roof to take a look and here is what I found:

 

Physically, everything looked good.  But distance from the ground was only 16 feet.  The calculations from two online calculators both agreed these antennas should be ~35 feet above the ground.  Now to take a look at what the antenna sees:

I have centered the antenna’s “target” in this picture.  There is a “V” between those two trees you see in the middle, and a little white speck centered in the V.  That’s our target!  As you can see, we don’t have a clear line of site, which means the antenna does not either.

Fortunately the Electricians came to the rescue with an extension of ten feet.  After the extension had been fabricated, a bucket truck was used to move the antenna up ten feet.

Here’s the antenna’s new view:

Now that’s more like it.  The target is the white blur you see in the middle of this view.  There’s nothing we can do about the metal electrical pole in the middle, which I am told was not there when the link was initially designed.

Now what?  Well, we moved it up, but dishes are not easy to align because they don’t come with any type of sight, and when you are standing behind one (or sitting in the bucket of a bucket truck 30 feet above the ground) you can’t really see what you are doing.

We decided to use the RSSI port on the Cisco bridge to align it.  The first thing you need to do is identify the BNC connector on the unit, which is #2 on the graphic below.

And in “real life”…

Next, you’ll need a length of RG-6 or other 75 ohm coaxial cable with a BNC connector on it.  I bought my raw cable at Home Depot and the BNC cable at Radio Shack.  I stripped both ends with my coaxial cable stripper (I just happen to have one of those) and screwed one end into the BNC connector.  The other end I left raw – that’s the end I connected to my multimeter.  When I was at Radio Shack, I also bought a pair of alligator clips for my test leads – see photo of meter below.  These little gems allow you to clip the meter’s probes to the coaxial wire – connect the red to the center conductor, and the black to the shield.  It is a lot easier than trying to hold the test lead directly to the conductor – especially if you are by yourself.  For a myriad of reasons, I do not recommend doing this alone. 

Connect the BNC cable to the port and measure the voltage with a multimeter.  I snagged this little multimeter at Home Depot for twenty bucks on the same trip when hunting the RG-6.  The other things are in my toolkit – a pair of radios for communicating with someone at the other end of the link, a flexible mirror, and some rubber tape.  The rubber tape is used for weatherproofing cables and connectors, and the mirror for reflecting light.  It sometimes works, sometimes doesn’t.  Don’t try  it at night… it won’t work.  A road flare, on the other hand…

With the connector on the bridge, simply connect the meter and read the voltage using the vdc scale.   I measured the voltage before we raised the antenna so we would have a baseline, and it was .78 vdc.

With the antenna now raised, we simply moved the antenna back and forth, from left to right and then up and down until we reached the highest voltage we could achieve.  We did read 1.43 vdc once, and then tried to find that again but could not and finally settled with 1.35 vdc.  I was happy with that and we decided that we should lock it down and be done with it.

I am also going to mention the length of the coaxial cable.  You may be tempted to use/purchase a short piece of cable.  If you are up in a bucket truck and someone else is there, it is nice to be able to have someone call out the voltage levels to you while you do the antenna adjustment.  A long cable is your friend sometimes.  It isn’t expensive or heavy, so why not get 10 feet or more.  You’ll thank me later.

For those of you who are curious, here’s what the scale looks like when trying to align a Wi-Fi link:

 

We went from somewhere around -70 dBm (we were at .78 vdc) to approximate -55 dBm.  In my book, that is phenomenal.  We gained at least 10 dB – those of you who are knowledgeable in RF math know what that means!

I will also mention there is another way to align the antennas if you don’t have a meter, etc.  I have not done it this way, however I will include the directions here anyway.  I clipped this information from the hardware installation guide.

“Aligning the Antenna Using LED Indications” (from the Cisco manual)

 

You can align the integrated antenna using LEDs after the bridge successfully associates with a remote  bridge. In the installation mode before association to another bridge, the Install LED blinks amber. If the bridge associates to a root bridge, the Install LED turns continuous amber. If the bridge does not associate to a root bridge in the first 60 seconds, the Install LED blinks green to indicate beacons are being transmitted and the bridge is waiting for another non-root bridge to associate. After association, the Install LED turns into continuous green and the Ethernet, status, and radio LEDs then display signal strength as shown below.  When using LEDs to maximize the signal, adjust the antenna until as many LEDs as possible are turned on and the rest are blinking as fast as possible.

 

Here’s the equivalent scale to the RSSI voltage method.

This is a real world example of what the LEDs look like on the back of the bridge.  As you can probably guess,  trying to watch these LEDs and aim an external antenna might be a challenge in the afternoon sun.

 

Now the antenna has been raised and aligned, I want to see what the traffic looks like with a protocol analyzer.  Looks 98% of the traffic is traversing the Wi-Fi link at 54 mb/s.

I confirmed with a console connection to each bridge that the signal is now in the -55 dBm range, just as the bridge RSSI voltage table depicted.  The SNR was now in the 35-40 dB, much higher than earlier reports of it being in the 10-15 dB range.

What a difference ten feet makes!  Mission successful…

One of my lessons learned on this expedition was the fact that I forgot to grab some screenshots of the console output BEFORE I did my work.  I have a protocol analysis of what it looked like before I started, however I don’t have any CLI.  I would love to have a “before and after” – I’ll just have to settle for that screenshot above.  Next time I won’t forget.

BTW, thanks to all who helped me out with blogging.  I appreciate all the input.  You know who you are.

 

 

 

 

So, you want to do an outdoor WLAN site survey with AirMagnet Survey & Microsoft MapPoint software.  You will need to have MapPoint installed on your machine – I installed Microsoft MapPoint North America 2010 for my configuration.

First, you’ll need a GPS receiver.  I found the following GPS devices have been tested to work with AirMagnet Survey:

1. DeLorme Earthmate GPS LT-20

2. DeLorme Earthmate GPS LT-40

3. Garmin eTrex

4. Garmin eTrex Legend

5. Garmin GPS 18 Deluxe (Use with GPSGate conversion software)

6. Magellan eXplorist XL

7. Magellan eXplorist 500

8. Pharos iGPS-180

When I first started out on this project, I did not have a GPS receiver.  I simply browsed eBay and searched the list I provided above.  I wanted a USB flavored receiver, so I chose the DeLorme Earthmate GPS LT-20.  It came with software, which immediately made its way into the recycle bin.  It cost less than 20 bucks with shipping.

I went through the standard installation of any USB device.  I plugged it into my laptop and let it go out and download the drivers and install them.  It shows up here as the USB Human Interface Device:

You’ll also need serial emulator software.  I went online and downloaded the DeLorme Serial Emulator version 1.09, and installed it.  The file I downloaded and installed was named “InstallSerialEmulator.exe”

Next, configure the serial emulation software with the following parameters: 4800, 8/N/1, no flow control.  You should see a little satellite dish icon on the bottom right of your screen.  Right click it, select ports, and as you can see here, I am using Com 2.  Don’t be fooled into thinking you are to select NMEA.  I was, and it did not work.  I finally stumbled into using my Com 2 port, and using the “Raw” setting. 

When you select the port, only use ports 1 – 9.  Don’t use any others!

To test the serial emulation softwarae, I used Tera Term.  I started Tera Term, chose Com 2, and then went to Setup à Serial Port and set it up with the same parameters I used with the serial emulation software.

At first, I did not see any data scrolling by.  Even though when I right click on the serial emulator software and it shows that Auto-Start is checked, I had to click start.

When I clicked OK, I started to see data scroll past me.  Now I know my GPS is working properly.  I will also state that during the making of this document, I went back and forth quite a few times, taking screenshots and I ended up rebooting this machine to get it working.  Your mileage may vary.

Now you are ready to configure AirMagnet Survey Pro and start your survey.

Step 1. Create a new project, name it, select the directory and select the GPS option and click next.

Next you will import the map from MapPoint.  You will have to be connected to the Internet when you set your project up, so do it from somewhere with connectivity.  Iif you are not connected to the Internet, this is the message you will recieve when you choose MapPoint from the Import Outdoor Street/Campus Map:

Choose MapPoint from the Import Outdoor Street/Campus Map (GPS) Image

Microsoft MapPoint will automatically start, and bring up a window for you to zoom in and select the outdoor area you are going to survey.  Zoom in to the area that you want and press OK.

You’ll see the GPS coordinates of the top left and bottom right of the box you selected as your survey area.  Click next.

I’m going to choose an outdoor residential area.  Notice how it sets my propagation assessment to 300 feet.  I set my power to 30 milliwatts since I am guessing that is the output power of most access points in the neighborhood. Click Next, and then click Finish.

Before you can start surveying, you need to configure AirMagnet Survey to that it knows about your GPS receiver.  From Survey mode, select File > Configure > Settings. Check the “Enable GPS port” box.  Then click on the Configure button and configure the Com port – I am using Com 2 for my configuration.  When complete, click OK twice.

You should test to make sure your GPS is configured correctly in AirMagnet Survey.  Select the “Tools” tab from the bottom right portion of the toolbar on the bottom of your survey.  Click on the GPS Information tab, and you should see GPS coordinates.  If you do not see anything, your AirMagnet Survey application is not seeing your GPS receiver.  The first time I used the GPS receiver I did not see anything, and I needed to go back and set up my com ports correctly.

I went outdoors, waited for my GPS receiver to get a fix, and then walked down the street.  I walked down one side of the street, down a little path at the end, and then back on the other side of the street.  I would estimate the survey was accurate most of the time, and when it wasn’t, it was about 20 feet away from where I was really standing.  Pretty good if you ask me.

One thing to note – I did lose my GPS fix when I was under some very large Oak trees.  If you think you might lose reception, keep an eye on your screen.  You may see a message like this:

Overall, I’m pretty happy with AirMagnet’s GPS functionality.  It all went together relatively quickly and painlessly.  Remember to configure your serial emulation properly and you’ll do fine.

For those of you who are wondering what the final product looks like, here it is:

Is evaluating every device on your WLAN necessary? Yes!

I was recently tasked with assisting in the wireless configuration of an evaluation/demo unit that was going to be on-site for a few days. The device was a portable x-ray machine with a remote plate that communicates with the portable unit.

After assisting with the configuration of the portable unit, I inquired as to how the remote plate communicates with the portable. I was told it had an 802.11n bridge built in and that is how it communicated. Since I could not access the configuration of the portable or the plate, I used my protocol and spectrum analyzer to see how it was communicating.

As soon as the main unit was turned on, I noticed an access point on channel five.  The technicians ran a test of the portable x-ray and the remote plate for me and this is what I saw when the unit took the picture and transferred it over the “bridge link”.

As the saying goes, the packets never lie. Here are a few screen captures from my protocol analyzer.

From all the evidence here, knowing those packets never lie, is this configuration really a bridge?  I discovered that it is not a bridge - it is really an access point and the panel is a client.

Is the channel set up properly? No. It is set to channel 5, which is not a best practice in the 2.4 GHz range.

What is your opinion of the Channel Bonding?   I do not believe in channel bonding in the 2.4 GHz range.

Would you allow this device in your environment?

For those of you like me who always want to know what’s under the hood – here’s what I found: