Sunday, January 9, 2011

Improving Wireless Reception - Part 1

This article is targeted at the non-technical or semi-technical user trying to improve their wireless reception at home.  Many people in my family and neighborhood ask me how to resolve poor (wifi) wireless reception in their homes so I thought I would share some tips and techniques I have suggested.  For clarity sake, what I am referring to is network wireless access as defined in 802.11a/b/g/n specifications and I am not talking about cell phone reception.

What is the difference between 802.11a/b/g/n
802.11b was defined and implemented first for the consumer back in late 90's.  This provided a transmissions speed of 11 Mbits per second in best conditions.  11 Mbits per second equates to about 1 MByte/second in ideal conditions.  Note:   for the more familiar with networking, I am NOT getting into packet overhead intentionally.  This specification used 2.4 Ghz frequencies.  This implementation of  wireless access was widely accepted and was a huge step into wireless networking that had useful speeds.

Next 802.11a came out for the consumer and used 5 Ghz frequencies.  It never really took off but is still available today.  5 Ghz frequencies are less crowded.  However 2.4 Ghz frequencies go through walls/floors much better than 5 Ghz frequencies.  Having not used 802.11a I am going to keep my discussion short on this specification.  However, I will mention, don't pursue setting up an 802.11a network.  There are better options.

Following 802.11a, 802.11g hit the consumer market and is still the most common wireless access method today based on my scans in public spaces and neighborhoods.  No, I am not a hacker, I just "listen" to see what is broadcast.  The FCC permits anyone to listen to any frequency barring cell phone frequencies.

802.11g goes through walls/floors even better than 802.11b and allowed speeds up to 54 Mbits which equates to about 6 MBytes/second in perfect conditions.  Like 802.11b, 802.11g used 2.4 Ghz frequencies in 11 channels described well on wikipedia here.

Some issues with 802.11g include crowded space since other devices like cordless phones, microwave ovens, baby monitors, IP video monitors, and other devices also use 2.4 Ghz frequencies.  Needless to say, your neighbors are also using 802.11g and you may get interference from them depending on where you live.

I am going to discuss 802.11n in part 2.  But in essence it is the next generation of wireless access after 802.11g.

Improving your wireless signal
Here are the steps I would follow to improve wireless access in your home.

1.  Create a baseline!  We need a metric to work against to see if we are improving the signal.  Download and install inSSIDer on your wireless laptop .  This simple, open source free tool will allow you to actually measure your signal and, more importantly, tell you what channels are in use.  Screenshot below:

Figure 1:  inSSDer screen shot
2.  Some notes on inSSDer.  Your have to select your interface and click Start in the top right hand corner.    This tool reports what wireless networks are in the area, what channels they are using, and the access status (open/encrypted).  Click on the RSSI column and sort the data so the highest number is at the top.  Note the numbers are in negative numbers so -52 is higher than -100.

3.  Now, the screen maybe overwhelming but we need just a little bit of information from it for our efforts.  Identify your network SSID, in other words, the network you connect to at home.  I will use CALLISTO in our discussion.  CALLISTO has an RSSI (will explain what this is later) of -72 and is on channel 1.  That's all you need to note now.

4.  Now take your laptop and go to places in your home where you like to work and have wireless access, e.g. kitchen, living room, etc.  For each room note the RSSI number for your network (write it down please!).  Note:  spend at least 1 minute at each location for the RSSI number to "settle down", then record the number.

5.  Now the work begins.  If your router/access point does not have external antennas go to step 6 below.  Make sure all connections to the router/access point are plugged in snugly.  Sometimes cables slide out.  Tighten the antenna connections, and put the antenna(s) straight up.  If they were already straight up, just tighten the antenna connection(s).  Next, repeat step 4 and take measurements and record them!.

6.  Make sure all connections to the router/access point are plugged in snugly.  If any connections were loose, repeat step 4 and record the measurements!.

7.  The biggest boost in reception is the next step.  Many people put their router/access point under a desk or table.  You cannot do that!  You lose about 25% of your signal strength if you bury your router/access point under a desk/table.  Put your router/access point in a high place in the clear.  What I mean is like on top of a shelf.  If you have no shelf nearby, consider mounting the router/access point on the wall up high.  Buy longer cables if it cannot reach your top shelf or ideal location.  Normally this would just be a longer ethernet cable available at Microcenter, Frys, Best Buy, Office Depot, Staples, etc...  Once you have moved the router/access point to the higher location, repeat step 4 and record the measurements!

We want the RSSI number to be as high as possible.  Again think negative numbers so -30 is higher than -80.  Ideally you want your RSSI number to be higher than -60.  You can still get connections between -60 and -70 but the connection will be very poor and intermittent.  I aim for RSSI of -50 and higher for my home network.

Your Homework
The location of your router and antenna position will directly influence your wireless reception.  Continue to re-position your router/access point and repeat step 4.  Again you are aiming for a high location that is clear of obstacles.  Ideally, router should be in the middle of the house.  If you have a router/access point without external antennas, turn the router in 90 degree steps and repeat step 4.  Find the position that provides the best reception for your house.

You have more influence on the radiated wireless signal if you have external antenna(s).  To find the best position for the antennas start with them straight up and record your RSSI at different locations.  Then, change the angle of the antenna(s) in small increments, 45 degrees, one antenna at a time and repeat step 4.  If you can visualize, each antenna normally radiates a doughnut shaped signal perpendicular to the antenna.  The important aspect to note here is there is almost no signal coming off the top or bottom of the antenna.

End of part 1
This is the end of part 1.  However, we still have more options for improving wireless reception.  I will try to get part 2 out in the next few days.

I'd really appreciate some comments, good or bad on this posting so I can improve it.  Questions are welcome too!

1 comment:

  1. Thanks for the great post John. I hadn't thought much about this topic, though I face signal issues here just as most people. I especially liked the doughnut comment.