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Wireless QOTD April 9th

Discussion in 'Wireless' started by tripwire45, Apr 9, 2004.

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Multipath is a form of interference caused by reflected signals arriving at a receiver out of phase

  1. Downfade

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  2. Corruption

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  3. Near/Far

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  4. Upfade

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  1. tripwire45
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    tripwire45 Zettabyte Poster

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    Last one for the week. Answer later.
     
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  2. SimonV

    SimonV Petabyte Poster Administrator

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    Vote C

    The near/far problem occurs when there are nodes near the access point that have high power settings and other nodes far from the access point with low power settings. The near, high power nodes overwhelm the far, low power nodes. To detect this, check the network design. Look at the power output level of the nodes. Possible solutions to the near/far problem include reducing the power of the nearby nodes, increasing the power of the far-off nodes, moving the far-off nodes closer to the access point, and moving the access point to a more central location.
     
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  3. Jakamoko
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    Jakamoko On the move again ...

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    I guess B - because it sounds right.
     
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  4. tripwire45
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    tripwire45 Zettabyte Poster

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    C'mon, gang. Time's clicking away. Only a few more hours until you all hit the pubs and I won't get another post out of you until Monday. Is this the best you can do??? :eek: :wink:
     
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  5. Jakamoko
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    Jakamoko On the move again ...

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    Oh really, Trip - you just think we're some delinquent bunch of IT weekend, party-type slackers ?!?!? :eek:

    Yeah OK - fair point ! I've got a successful appraisal and pay rise to celebrate for a start (oh, and a birthday on Sunday !!!) :alc
     
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  6. flex22

    flex22 Gigabyte Poster

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    I take it that A, B, C, and D go from top to bottom.

    In that case Upfade will be D.

    My Answer: D
     
  7. Jakamoko
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    Jakamoko On the move again ...

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    You don't seem to have voted, Flex - can you try again ?
     
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  8. flex22

    flex22 Gigabyte Poster

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    AHH yes voting would help wouldn't it :oops:
    :soz
     
  9. tripwire45
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    tripwire45 Zettabyte Poster

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    Sorry to be so late answering. I got busy yesterday afternoon/evening and didn't get back in front of a computer until just now. Correct answer is C. Near/Far. All of the other choices are possible results of multipath, depending on the signal delay and whether the signal is in or out of phase with the main signal.

    Near/Far is a phenomena that occurs when there are several WLAN clients near the AP that are using a high power output and another client further away but still within range of the AP using lower output power. The client further away cannot be heard because the nearer, more powerful clients are "drowning him out". Kind of like being at the other side of a room and still trying to whisper to someone who is surrounded by several people shouting at him.

    Congratulations and Happy Birthday, Gav. Any idea i have that you folks like to "party hardy" on the weekends is your own fault. Don't try to deny it. :D Have a good weekend, all.
     
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  10. flex22

    flex22 Gigabyte Poster

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    Would the solution be to put the lower power outputs nearer to the AP (what does AP stand for :?: )

    If that wasn't possible, is their a way of decreasing the power output of the nearer clients, to allow the further one away to get a "word in edgeways" as it were :!:
     
  11. tripwire45
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    tripwire45 Zettabyte Poster

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    Sorry. AP stands for "Access Point". It's sort of a wireless hub and usually acts as the interface between the wired and wireless network, although an AP can be a stand alone if the Wireless network doesn't need to connect to anything else.

    Yes, the solution to near/far is to increase the power output of the more remote node and to decrease the power of the nearer nodes. This sort of problem usually occurs where all nodes are within the stated range of the AP but for some reason, the radios on the near nodes are set higher than average.

    I only have two wireless computers in my home. The other two communicate via wire through a Layer 2 switch. The AP has an Ethernet port in back and it also is configured with an IP address for my network and connected to the Layer 2 switch so my network is a "hybrid" which is pretty common in most homes and businesses. My wife's computer communicates through a USB wireless NIC. It's in another room and I didn't feel like running cable under the house to her PC. The other wireless node is my laptop. I often go into the living room or out on the back patio to work and can connect to the rest of the network and the Internet from anywhere I want. Makes it very convienent to work.
     
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  12. flex22

    flex22 Gigabyte Poster

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    I'm the same, although my laptop doesn't last very long without the plug attached.Nethertheless, I only need to make sure I am near a power socket, which is more convenient than having being near a phone socket as well.

    I get what the AP is now.My wireless router must be the AP right.It conencts my desktop pc via a cable and connects my laptop via a wireless link.The laptop has a PCMCIA wireless adapter.

    So that's like a hybrid isn't it :?:
    because one's using a cable, and one's using a wireless link to conenct to the internet through one router.

    This is probably obvious, but I've only just got my wireless and am still figuring it out, so am asking plenty of questions.

    Your questions are brilliant Trip, cheers :!:
     
  13. tripwire45
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    tripwire45 Zettabyte Poster

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    Wireless PC Cards eat up a ton of electricity. There's a huge power cost in converting data from electrical to radio wave signals and back again.

    An AP and a Wireless Router are related but not the same thing. My AP is no more intellegent than a Layer 2 switch and not even that. All APs operate at Layer 2 but they also broadcast like crazy and to not create point-to-point links the way a wired Layer 2 switch does. Your wireless router has all the capacities as my AP plus it can do layer 3 routing and do DHCP. If I had a broadband solution for my Internet access, I'd go out and get myself a wireless router then lock down my security as tight as it would go to keep anyone driving by with a wireless device and wireless packet sniffer from piggybacking on my broadband signal.

    Alas, I am still using dial-up. Thanks for the compliments but it's not hard to be "brilliant" when you're studying the material all the time.
     
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  14. flex22

    flex22 Gigabyte Poster

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    I never realised they took up a load of power.Dmmit there's always something isn't there, never quite the perfect solution :x

    Nevermind, it's still good to have internet access on my laptop throughout the house.

    I think my router has a built in firewall.I'm not really sure about all the settings and such.It does give out DHCP, but I'm not sure how this works.

    I mean the router has an IP address, yet doesn't my ISP assign it the IP address.Or is the router address just for the benefit of the internal lan.Probably that's the reason.

    I need to make my router more secure, from the threats you ahve mentioned Trip.Can you or anyone recommend a good article on this.I know for sure that I haven't set it up very securely yet, just not got around to it.Time to sort that out now though.

    Thanks :!:
     
  15. Jakamoko
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    Jakamoko On the move again ...

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    Your router actually has 2 NIC interfaces in it - an internal and external, Flex. The external interface gets the IP add from your ISP, and the internal provides IPs to all PCs on your LAN. The translation and transfer/routing of packets to and from intended recipients is the clever bit that happens in between.

    HTH :)
     
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  16. flex22

    flex22 Gigabyte Poster

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    Aye, I thought it were summit like that.

    So the IP address of my router that came with the product is only like the default gateway address.
    I think I can change this anyway, but don't see any reason to at present.

    Then this address is transferred to my ISP assigned address.

    So the internal clients use the router IP.The router IP uses the external interface IP assigned from my ISP.

    Cool 8)
     
  17. tripwire45
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    tripwire45 Zettabyte Poster

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    NEVER leave your wireless equipment set to the default configuration. Default SSIDs and IP addresses are well known and systems left at their defaults make easy prey for intruders. Always chance those settings. They represent a minimum in terms of security, but making those changes is better than nothing. I know of network admins that have left the default passwords on their Cisco routers and switches and have lived to regret it.
     
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