Results 1 to 7 of 7

Thread: Why you may be having Wi Fi problems- it may not be hardware or software

  1. #1

    Why you may be having Wi Fi problems- it may not be hardware or software

    Many or most of wireless networking problems are not hardware or software related, but due to the nature of wireless radio-frequency (RF) signals. Wireless internet signals are microwave energy at about 2.54 GHz (giga hertz) and are EXTREMELY sensitive to interference. Even worse, since the wireless signal is carrying (or supposed to carry) very high speed data, the connection is even more critical as a bad wireless connection corrupts the data being sent or received. A wireless system is a set of RF receivers and transmitters, one on each end. The computers wireless card has a receiver, transmitter and one or two antennas, as does the router. This system sends data at many kilo or mega-bits per second through the air. Its critical to understand that the slightest "path interference" (any condition that damages the RF signal) will corrupt the wireless networks data communications. Whats worse is that high speed computers dont have much time to sit and wait for endless re-transmissions to get the data right. They have too much else to do. These RF signals are at 2.45 GHz which is the same frequency as a microwave oven, and also the same frequency as the vibrational frequency of WATER MOLECULES which is how a microwave oven works, the RF frequency causes the water molecules to vibrate and make heat. Thus, water, water molecules, water vapor, water in or on the ground or walls of the house can do immense damage to a weak wireless signal. Or, water vapor might HELP your wireless connection, its difficult to tell and you cant do anything to change it. Even moisture content in the air can help, or destroy a Wi Fi connection. It can literally change the signal path from something as simple and invisible as the wind blowing. I have seen weak network signals which became corrupted just because the sun came up in the morning - implying the moisture in the air changed and affected the wireless signal path. Maybe the water will ruin the signal by absorbing it? Or, maybe it will HELP your wireless network by absorbing the energy from another Wi Fi network nearby. Unfortunately, its likely that your router and wireless card are on the same channel as several other wireless systems nearby for other users. This leads to a condition called "collision" where several network signals and their data collide together and end up a jumbled mass of useless energy. Its not even "data" at that point, its useless to the computer(s). Many or most wireless users simply buy a router, plug it in and expect instant internet that works perfectly. Yes, that will happen if there is not another network nearby on the same channel, but its common to find 2 or more networks all on the same Channel 6, which is a default channel in many routers. If two or more wireless signals appear at the router at the same time, how does it sort them out? It cant. It ignores both of them. It takes only a poor signal to establish a "wireless connection" which basically means an IP address has been worked out and agreed upon by both ends, the computer and router. that absolutely DOES NOT mean there is a data communications path. It just means the router had a brief window of time in which to know a connection is requested, it DOES NOT mean that the path is suitable for sending and receiving high speed data. As I type this, my wireless card has an IP address with a remote router but is completely unable to send or receive data, because there is another distant router that is the same signal strength and none of the network nodes (either router or wireless card) has any idea of what to do with the scrambled signals. There is no valid data being sent or received, just garbage. Wireless data is data bits at micro-second speeds and wireless networks, especially microwave networks such as Wi-Fi systems use are EXTREMELY sensitive to RF reflections. RF microwave energy can reflect off very small metal surfaces or even off of moisture on the ground. Also, the ground radiates microwave energy that can cause interference. If a Wi Fi signal has a direct path to the router, and also has a reflection, the reflection of its own signal can corrupt the received signal at the router and destroy any chance of sending and receiving data. Again, its purity of data that is critcal NOT just that there is a "connection." Assume the direct path is sending a "1" data bit followed by a "0". Assume the "1" bit is reflected off a nearby automobile body and is delayed by a time of one bit. Instead of the router seeing a "10", it might see a "11" where the first "1" is the direct (intended signal) and the second "1" (which should be a "0") is the reflected data. Thus, no useful data is received, although valid data was sent. It is impossible for the router to sort the signals out as they are a function of what the routers receive antenna picks up, not a function of data transmission. Think of this as shining a flashlight inside a hall of mirrors. You could end up shining the flashlight beam out and seeing your own beam coming back! Or, two people can shine lights, the beams mix and its impossible to tell which beam is which. Since most wireless equipment uses omni-directional antennas (receive and transmit in all directions equally in one plane) it is impossible for the router or antenna to ignore reflected signals, or to ignore another router nearby on a diferent system but which is on the same RF channel (say channel 6, Ive seen networks where there are 5 signals on channel 6 all colliding with each other). Some wireless adapters have antennas which are marginally directional such as the D-Link N card which can be plugged into a USB extension cable and pointed in various directions. This is vaguely directional. Programs such as Wi Fi signal sniffers can be used to see (do a "site survey"), on the computer screen, readouts of various network Wi fi signals, what channel they are on and their signal strength in dB (decibels, a unit of electrical power). This is mandatory to resolve many wirelss collision problems although without the ability to change channels, or computer location, or without a directional antenna, the information is nice, but useless. A directional antenna such as a patch or Yagi is critical to making and keeping a wireless connection where collision is a problem, or where there is a large distance between Wi Fi card and router. Such an antenna can electrically tune out signals that it is not directly pointed towards. The way to resolve whether collision is the issue is to use a site survey to discover if a nearby Wi fi signal is likely the cause, meaning another Wi Fi device on the same channel. Some routers have site survey capabilities built it, accessible by logging into the router and seeing the site survey data from the router. If there is another signal then two things might correct the problem: 1.) changing the router Wi Fi channel so both Wi fi systems are on different channels. 2.) Moving the router closer to the intended Wi Fi client so the intended signal is greater than the undesired one. The signal strengths in dB are INVERSE (a lower number is a better signal i.e. a -90 dBm signal is WEAKER than a -75 dBm signal) Microwave devices are EXTREMELY sensitive to things like just placing a hand on the router cabinet, or running the power cord near the router antenna. Just moving the router a few cm or rotating it a few degrees might help or make the problem worse. I have placed USB Wi Fi cards on top of my head to tune out interfering signals and establish a connection with the desired router. The proximity of the head, and the water it contains, disturbs the signals. If omni directional antennas are used, both must be in the same orientation (polarization) or communications will be damaged. It might help in the case of collision to rotate both antennas to horizontal, if the other interfering systems are vertical. Where these dont work, it may be necessary to use a directional antenna, change router or client transmit power levels or both. It may be that a lower transmit power and weaker signal helps, not due to distance, but to reduce the transmitted signal and reduce a reflected signal appearing on the router antenna. It is somewhat a trial and error problem. Collision, which may make Wi Fi communications poor for any or all networks in the same area, might be improved by a user logging into another systems router which has been left un-locked, and changing its Wi Fi Channel. This should not harm their network as the client Wi Fi card can automatically lock in on its routers channel- its automatic as is IP address assignment. If the router is unlocked (using default user name and PW) then its likely the user knows nothing about setting up the Wi Fi network, you might actually be doing them a favor by changing their routers channel and making Wi Fi comms better for all users. Wi Fi collision can actually lead to hardware or software problems on the computer, although there is no direct link. I have experimented with connecting to very weak signals, where the Wi Fi path is very unreliable, made numerous setting changes to the Wi fi system and software, only to crash the Wi Fi card software or even the browser. Iceweasel is particularly sensitive to this, it seems to crash easily. Even a router can be hung up by changing too many settings too quickly, I have no idea why, but Ive seen it happen many times - a hard reset was needed to solve the problem. The easiest way to rule out transmission path problems is to eliminate the path, place the computer and Wi fi card right beside the wireless router. This guarantees a very strong Wi Fi signal between computer and router and should eliminate the communications path as a source of problems. that is, unless there is another unwanted router nearby with a very strong signal, and a site survey will tell.

  2. #2
    Senior Member registered user
    Join Date
    May 2006
    Location
    Columbia, Maryland USA
    Posts
    1,631
    @ daveca

    I suspect the whitespace goblin has been working on your text.
    Anyway, here's some data from DD-WRT which goes along with
    what you are saying:

    http://www.dd-wrt.com/wiki/index.php..._connection.3F

    Data Rate...Minimum SNR
    6 Mbps..........8 dB
    9 Mbps..........9 dB
    12 Mbps........11 dB
    18 Mbps........13 dB
    24 Mbps........16 dB
    36 Mbps........20 dB
    48 Mbps........24 dB
    54 Mbps........25 dB

  3. #3
    Senior Member registered user
    Join Date
    May 2006
    Location
    Columbia, Maryland USA
    Posts
    1,631
    Some fresh data from my own kitchen:

    I'm on Channel 1; three neighbors: one each on channels 6, 9 & 11.
    My SNR ~18 dB thats 2 or 3 bars on NM applet.
    Neighbors are 1 or 2 bars on NM applet.
    All are using g.
    My download speed at SpeedTest.net is 10.6 Mbps.

  4. #4
    Senior Member registered user
    Join Date
    May 2006
    Location
    Columbia, Maryland USA
    Posts
    1,631
    @ daveca

    The information theory I learned years ago was not the same as yours.
    Yours has a definite James Joyce lilt to it which I find enjoyable.

    Quantification isn't everything.

  5. #5
    This board has a habit of eating whitespace, I put properly formatted text in and it trashes it. O well...

  6. #6
    Senior Member registered user
    Join Date
    May 2006
    Location
    Columbia, Maryland USA
    Posts
    1,631
    If you have an AdBlocker, disable it on knoppix.net.

  7. #7
    Senior Member registered user
    Join Date
    Mar 2004
    Posts
    1,516
    if you put the text inside [-code-] and [-/code-] (no "-" between bracket and code) you
    can have loads of whitespace

    Code:
    if you put the text inside       [-code-   and      [-/code-]  (no "-" between bracket and code)        you
    can                   have                         loads        of
    whitespace as whitespace is often important in coding.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •