Using a GPS to perform a Wi-Fi survey

It is important to perform a wi-fi survey so that you can determine not only the perfect place to locate your access point or bridge but to gain an understanding of the channel co-existence challenge you may face.  With wireless access points in surrounding neighborhoods and businesses, you will need to  perform a survey by walking around and mapping out the BSAs (Basic Service Area) of wireless that surrounds you and your organization.

Below is an example of our school’s perimeter.  Matt, Chris and James, students in the Computer Information Technology, class performed a survey using a Microsoft GPS and Vistumbler.  This survey revealed access points and their channels of current wireless at our institution and  includes APs in surrounding businesses and neighborhoods.  These were mapped using Google Earth after exporting their KML file from Vistumbler.

This type of survey allows IT professionals to analyze data exported to ensure the correct channels can be used at their organization.

Miller Goodroe Felts

After exporting the wireless information, you can analyze each access point or wireless device by clicking on it.  Below is an example of the information exported into Google Earth.   Each device shows SSID, Network Type, Mac Address, Channel, Security, Encryption Type, Data Rates, Latitude, Longitude and Manufacturer information.   Analyst using this information can also determine the best placement of wireless devices along with channel information.

ESSID Expanded

Channel co-existence is when access points share channels that are very close to one another.

802.11 wireless on 2.4 Ghz has three non-overlapping channels.  These channels are 1, 6 and 11.  The closer channels are, the more likely interference will take place.  With the amount of wi-fi in use today, IT professionals have to chose between 2.4 Ghz and 5 Ghz and and try to select channels that are not in use if possible.   Professional access points and bridges can also adjust power as necessary.   A dense population can make this very challenging.

If you look at the students’ survey by zooming out to see how many access points can be seen, this is what you are looking at!  Now you can see why site surveys are important at your organization.

Exploded

In addition to this survey, a secondary survey using a spectrum analyzer is very important to search for interference from other sources.  (See our review of the Airview Spectrum Analyzer)

analyzer-software

Channel information (Chart from Wikipedia)

NonOverlappingChannels2.4GHzWLAN-en.svg

Here’s another look at a wireless survey showing vertical lines and signal strength.  (James M. KML survey)

Another view James Miller KML

Add GeGeek Toolkit to Hiren’s CD/DVD for the ultimate troubleshooting tool

One of the best sites on the web is GeGeek.  GeGeek has over 300 tools (freeware) that you can download for troubleshooting any computer.   How can it possibly get more powerful?

Use Rufus USB to create a bootable ISO of Hiren’s CD/DVD’s ISO.  See our other article – link.  Once you create the bootable flash drive, copy the GEGeek folder to

Now when booting to your USB drive, you can boot into Windows XP mini and navigate to the flash drive.  Navigate further into the Prorams folder and then into the GEgeek folder.  You can now use any tool you need to troubleshoot or diagnose your computer.

GEGeek Toolkit

Network Switches – Avoid Daisy-Chains

When you are networking computers, wireless access points, printers and other nodes in multiple rooms, try to avoid daisy-chaining switches or using small 4-8 port switches when you are in a hurry.  Replace any hubs on your network as soon as you can.

With a hub, collisions can be >20% and utilization can stand at >50%.   By replacing a hub alone, you can reduce collisions to 5% on switches in rooms and <1% in the server room.  Switches help to isolate traffic, relieve congestion, separate collision domains (reduce collisions), segment and restart distance/repeater rules.

Daisy Chaining Switches -what not to do

Real world scenarios may require you to temporarily daisy chain switches.  If you do, test the network and run additional backbones or replace core switches to accommodate more nodes as soon as you can. (remember, replace any hubs in your network)

Daisy chaining

One of many solutions is to run independent lines to the core switch

alternative

Basic tips on optimization of your network -

  • Use stackable managed switches
  • Purchase switches that support
    IEEE 802.1D , IEEE 802.1p , IEEE 802.1Q , IEEE 802.1s , IEEE 802.1w , IEEE 802.1x , IEEE 802.3 , IEEE 802.3ab , IEEE 802.3ad (LACP) ,
    IEEE 802.3ae , IEEE 802.3u , IEEE 802.3x , IEEE 802.3z
  • Use a battery backup on the switches

This is the very basics behind network switch infrastructure.  Managing switches and using the IEEE standards above along with optimizing your network and managing the network infrastructure is important.

Excellent articles on Networking Infrastructure

http://www.lantronix.com/resources/net-tutor-switching.html

http://www.techrepublic.com/blog/it-consultant/only-novices-daisy-chain-switches/

Best Free Wi-Fi Tools

One of the best wi-fi tools you have on your Windows based computer is netsh.   Netsh can be used to find out information about wi-fi.

Open a command prompt and you can use these tools…

netsh wlan show networks

Netsh One

netsh wlan show networks mode=bssid

Netsh Two

inSSIDer

- Uses your current wireless card and connection software
– Works with Windows XP, Vista and 7 (32 and 64 bit)
– Compatible with most GPS devices
– Track the strength of received signals in dBm over time
– Sort by MAC address, SSID, Channel, RSSI, and Time
– Export Wi-Fi and GPS data to a KML file in Google Earth

Inssider

Vistumbler  (GPS Capable)

  • Find Wireless access points
  • GPS Support
  • Export/Import access points from Vistumbler TXT/VS1/VSZ or Netstumbler TXT/Text NS1
  • Export access point GPS locations to a google earth kml file or GPX(GPS eXchange format)
  • Live Google Earth Tracking – Auto KML automatically shows access points in google earth.
  • Speaks Signal Strength using sound files, windows sound api, or MIDI

Vistumbler

NetSurveyor

  •  6 graphical, diagnostic views:
    *Timecourse of Beacon Qualities For Each Access Point
    * Differential Display of Beacon Qualities for Each Access Point
    * Usage of Each of the 802.11 Channels
    * Timecourse of the Usage of Each of the Channels
    * Heatmap / Waterfall Chart of the 802.11 Channels
    * Channel Spectrogram of the 802.11 Channels. The more (and different) ways you have at looking at data then the greater the chance something will catch your eye that you might otherwise miss if only a single type of chart were used.
  • Generates reports in Adobe PDF format
  • Powerful and innovative logging and recording capability.NetSurveyor’s playback mode is unique in that it shows you all the recorded data

NetSurveyor

Xirrus

  • Find Wi-Fi networks
  • Managing and troubleshooting Wi-Fi connections
  • Verifying Wi-Fi coverage
  • Locating Wi-Fi devices
  • Detecting rogue APs

Xirrus

What GPS have we used successfully and easily installs in Windows for the GPS Wi-Fi finders above?  The Microsoft GPS Receiver.   The receiver is small, light weight and installs easily.

Microsoft
Our class uses a scientific method of studying wireless and security.  With hands-on during every term (not in a closed lab like a majority of higher-ed institutions), the classes we teach really enjoy the study of wireless and analyzing signals.   During a recent study we found over 380 access points of which 50% were unsecure.

WiGLE has a global map drawn up by wardrivers.   Viewing the maps is scary – really, really scary.  These online GPS maps show secured and unsecured networks.

How to secure your access point- Linksys Belkin Netgear 2wire DLink

Attaching to unknown networks that are unsecured and not public is both dangerous and illegal.   Actually connecting to wireless  hotspots can be dangerous (See our article on attaching to HotSpots).   You should always use a vpn when connecting to a hotspot.   There are now applications that allow laptops, netbooks and droids to be setup as hotspots.  With packet capturing software, your data can be intercepted if you don’t use a vpn.

Improving your wireless signal is actually is easy.  For as little as $40, you can gain (from 30mw) to 1000mw or even 2000mw with the Alpha Antenna.  With a standard laptop, we see approximately eight access points.  With the Alpha we see approximately 14, and with a large antenna we were able to see 44 access points.

So what if you get a larger antenna?  There is a balance of antenna type vs. antenna gain.  A larger antenna can be better,  if it is not too large.


Decibels in relation to power gain:

20 dB is an increase of 100X in power
10 dB is an increase of 10X in power
6 dB is an increase of 4X in power
3 dB is an increase of 2X in power
2 dB is an increase of 1.6X in power
1 dB is an increase of 1.25X in power
0 dB is no increase or decrease in power

Decibels/dB, how to understand their relationship to power loss:

1 dB loss: 80% of power remains.
2 dB loss: 63% of power remains.
3 dB loss: 50% of power remains.
6 dB loss: 25% of power remains.
9 dB loss: 12.5% of power remains.
10 dB loss: 10% of power remains.
12 dB loss: 6.25% of power remains.
20 dB loss: 1 percent of power remains.
(Therefore professional wireless cards have to be used for larger antennas)

(Calculators)

If you add an antenna (yagi, omnidirectional) and need to add cable, make sure the total attenuation or loss is no more than about 3 db at 2.4 GHz or you could lose half of your total transmit power before it even reaches the antenna.

Specs on the Alfa Antenna ~

* Compatible with IEEE 802.11n, 802.11b/g/n wireless standards
* 2.4GHz frequency band, MIMO (Multiple Input Multiple Output)
* Complies with Universal Serial Bus Rev. 2.0 specifications
* High speed transfer TX data rate up to 150 Mbps
* Supports WPS by S/W
* Supports wireless data encryption with 64/128-bit WEP, WPA, WPA2, TKIP, AES
* Wide Range coverage
* Compliant with FCC Part 15.247 for US, ETS 300 328 for Europe
* Works with Windows 2000, XP 32/64, Vista 32/64, Windows 7 32/64.

Specifications:

- IEEE 802.11b/g/n standard
– USB 2.0 standard
– Up to 150Mbps for 802.11n connections
– Frequency Range: 2.412~2.483 GHz
– Receive sensitivity 11b: -92dBm, 11g: -76dBm, 11n: -73dBm@HT20, -70dBm@HT40

Want to further analyze signals? Use a Spectrum Analyzer ($40+).

If you are looking for an economical solution the 2.4 Ghz Spectrum Analyzer by  Ubiquiti  is an excellent buy and is around $40+ – with an external antenna (AirView software is free)  My recent purchase for our class (personal purchase) is an excellent production and teaching tool.

A Spectrum Analyzer normally cost several hundred dollars.  This solution is an excellent solution for viewing the distribution of RF energy in the 2.4GHz band.   By viewing the analyzer, you can determine which channel has the least interference and select an appropriate channel for maximum performance.

See How it works- Link

Product Information

You must purchase the hardware in order to use the software.

Excellent Product for the money.

Configuring WDS to extend your wireless network

Want to extend your network and make it more reliable and robust?   

Here’s what you will need -

  • Two routers with the same firmware
    • Preferably Tomato or DD-WRT

Login to the first router.  

In this example, the static number 192.168.1.1 is the Main router.

  • Enable the WAN to match your ISP  
  • Enable DHCP
  • Enable Access Point + WDS  (Picture two below)
    • You must have the same wireless configuration on both routers
      • Enter the MAC address of router two under WDS Link with.

Router 1 no 1

Router 1 no 2

Login to the second router

  • Disable the WAN
  • Disable DHCP
  • Assign the router a static IP address (Below we have given the router .250)
  • Enter Router One’s IP Address for the Gateway
  • Enter a DNS of your choice
  • Make the wireless configuration the same as the first router.  Under WDS, change the drop down to automatic.

Router 2 no 1

Router 2 no 2

With the same settings, you can now extend your network several hundred feet under the right conditions.  Because the SSIDs are the same, once you join one of the routers with a smartphone or laptop, it will seamlessly change to the stronger signal.

With Tomato, you can chain together approximately 12 devices.

Links-

Tomato RAF

Shibby’s Tomato

DD-WRT

Note; The IP addresses and MAC addresses are in a lab environment.

How does it look on a network map?  The two routers are actually connected together.  The switch is the four ports on the back of the router closest to the internet.

Map

Wi-fi takes a long time to find network after computer sleeps

After your computer goes to sleep, do you notice it takes a long time to connect to your wireless router?
slow
There can be several reasons for this.

Here are some tips~

  • Power management on the adapter is enabled
    • Disable in the Device Manager
  • Advanced Power Management
    • Disable under Power Options (Advanced)
  • Bluetooth Interference
    • Disable under the advanced tab on the wireless network card properties
  • Outdated Driver
    • Updated the driver from the manufacturer of the wirelesss chip and not from the computer’s support site
  • Disable the Virtual Wi-fi under the device manager if you don’t use Adhoc

Advanced Power options – Set to Max Performance

advanced wifi

Disable Bluetooth settings

 

Bluetooth

Disable Power Management

 

network power device manager

 

Use the following freeware to see if you have channel interference and to analyze the power in each room of your home or business:

Vistumbler
NetSurveyor
Xirrus

 

Ultimately, reset your network by going to a command prompt as an administrator and type the following:

netsh int ip reset reset.log
netsh int ipv6 reset reset.log
netsh winsock reset catalog
nbtstat -r
nbtstat -RR
ipconfig /flushdns

Restart your computer

Going to take a certification that involves binary?

Going to take a certification that involves binary?

Here’s a quick tutorial~

Let’s say you are given an IP address of 192.168.1.135 in an answer.

What is this number in binary?

Here’s what you do.

Take a simple key to convert the numbers in the octets into binary.
The key is this:

128   64   32   16   8   4   2  1

Now let’s take the first octet of 192 and let’s see how many times the numbers above (the key) go into the given octet.

How many times does 128 go into 192?     192 – 128        1 time
This will leave us 64.
Next, how many times will 64 (your remaining number) go into the next number in the key(64)?

64 -64       1 time

Now the remaining number is 0.   So if you subtract 32 from 0 the number will be 0.  16 from 0 is 0, 8 from 0 is 0, 4 from 0 is 0, 2 from 0 is 0 and finally 1 from 0 is 0.

Look at your answers. 11000000 -This will represent 192.

Now let’s do the 168 octet.

128 goes into 168 – 1 time.   The remaining number is 40.   64 goes into 40 – 0 times.    32 goes into 40 – 1 time.  This gives you a remainder of 8.   16 (the next number in the key) goes into 8 how many times? 0 . 8 goes into 8 – 1 time.  The remainder is now 0.    4 goes into 0 – 0 times.   2 goes into 0 – 0 times.  1 goes into 0 – 0 times.   Look at your answers (bold).

168 will be 1010100

Of course the next number (third octect) which is 1 will be 00000001.

If you use the above key for 132, along with the subtraction method, 132 will be 10000100.

Your final answer is 11000000.1010100.00000001.10000100

 

Try a these yourself using the subtraction method above -

192.168.1.32
192.168.1.111

 

Flip over and see the answers

11110110˙10000000˙00010101˙00000011
01100100˙10000000˙00010101˙00000011
:ɹǝʍsuɐ