WDS/Bridges with WRT54G's, Yagi Directional Antennas and maybe a Linksys E4200

Discussion in 'Cisco/Linksys Wireless Routers' started by jgutz20, Aug 11, 2011.

  1. jgutz20

    jgutz20 Network Guru Member

    Wow, its been a while since i've been on this site! glad to be back.

    Alright so i've got 4 early WRT54G routers (2x v1, v2 and a v4) all having DD-WRT running on them from a couple of years ago, i had WDS set up at the in-laws place and just left everything running over there (i used the WDS as a wireless bride for a physical port on a slingbox and the another on a DVD player etc) So i've got them set up with a single router now and took the wrt team back with me and i'm trying to connect a couple locations.

    --The Layout/Situation--
    *I have a garage about 60' from my house with an IP Security camera. I do have an extra conduit run under ground (seperate to the power conduit) and could easily run CAT Cabling out there but for this one camera, The wireless G throughput would easily be enough with the signal i can receive here, The camera i have is a Vivotek IP8332 so it needs a physical plug.
    *Going from the garage behind the house to a house across the street (distance = ??, a couple hundred feet for sure), i've got another WRT running over there with a Directional Yagi 16db antenna and i am getting 3/5 bars which is effective but i'm curious about how to strengthen this.

    --Possible Solution ideas--
    *One thing i've never really been able to find much on when dealing with directional antennas, if i hook one up, utilizing only 1 of the 2 TNC ports, does leaving the "normal/omni" antenna in there mess up the wireless signal as they are made to work together?
    **Since there are dual antenna ports, and i do have another Yagi antenna (identical), is it best/necessary to have both directional antennas hooked up on the one client router facing back to my house?
    **Does it make the most sense to use the second directional antenna at my house so both of these are facing each other directly?
    *I have been seriously contemplating grabbing a Linksys E4200 router to use as my "Main" WDS router (With DD_WRT) and having the WRT's simply as the client/end routers. That way i can still use this single Wifi connection for clients to connect to instead of having a cheap Netgear N router sitting on the other side of the house for laptops etc, and then a series of WRTs for everything else.
    *Would the WRT routers be able to benefit from the stronger signal of the E4200?
    *Money is not a major concern (to an extent obviously) but i do have the resources to purchase other hardware if it makes sense.

    --Other notes--
    I've also got a sonicwall firewall/router with wireless that is strictly acting as that, a firewall. I have a Domain with multiple servers (i host a few websites for friends/small businesses just for kicks), the PDC is also a DHCP server for the addressing, everything is running under a single subnet (10.10.20.x/ but i am capable/willing to create a seperate subnet for these "remote" (but local) parts of the network. I have a CAT-6 cable running up into an unfinished attic (Not insulated), with open slats on the gable end with a clear line of sight to the neighbors, so i could very easily get the second directional antenna connected and mounted up here. I do plan on having the router sitting up here as the alternative would be very much an eye sore and in an annoying location if on the main level.

    Any other recommendations? suggested setups? i would love to hear them.
  2. jgutz20

    jgutz20 Network Guru Member

    Bump... Hey Toxic, Do you have any ideas for this setup? I just ordered a TNC female to SMA male adapter so that i can hook my 2nd antenna into the WTR54G router.
  3. howardp6

    howardp6 Network Guru Member

    I doubt you would get a benefit from the E4200. Most of the benefits of the E4200 is from the 802.11n dual channel for both 5GHz and 2.4Ghz. Your WRT54G routers are incapable of using dual channel and both frequency ranges, since they are restricted to the 2.4GHz and only single channel. The WRT52Gs only use one antenna for transmitting and receiving. They also only have one radio. The main avanatage of the E4200 is it has two radios one for each frequency and the wireless 80211n. You wold only benefit if you replaced the WRT54G with a 802.11N bridge and I doubt you want to spend that much money.
  4. HennieM

    HennieM Network Guru Member

    Further to what howard says: The WRT54 routers use antenna diversity, which means it uses only one antenna at a time. Which antenna to use, is, AFAIK, determined by which one gets the strongest signal from peer/client when receiving. Therefore, in your setup where one is connected to a Yagi, that antenna will mostly be used.

    You will have no improvement from a second Yagi on that WRT54, but you might force the router to only use the antenna with the Yagi, so you are sure it uses only that one all the time. If your across-the-street link is point-to-point, i.e. router-to-router only, you will definately gain a lot of signal strength by putting a Yagi (or any directional antenna) on whatever the WRT54 talks to across the street. A stronger antenna boosts both transmit and receive signal - nothing, no tweaks with signal strength or any such thing - beats a better antenna. However, if your current signal (you mention 3/5) already gives you a continuous 54Mbps link, then there's no speed to gain as that's the WRT54's max speed.

    I know just about nothing about the 4200 and such (newer) routers, but as they seem to use MIMO, which means they use, on the G radio, a number of the channels, be careful that you set it up so they play nice with your existing G-only devices, as the G-only devices may be subject to interference from the MIMO signals and vice versa.
  5. howardp6

    howardp6 Network Guru Member

    The E4200 uses two channels and MIMO on both the 2.4GHz and 5.2 GHz band. There are only three non-interfering changes on 802.11G, there are more channels on the 5.2 GHz bands. In addition the maximum rate is 450 Mbs with a three antenna wireless NIC, which unfortunately are a very few.
  6. jgutz20

    jgutz20 Network Guru Member

    So i get that i would get no benefit to the 5ghz frequency band on the E4200, but i was just curious if this router actually has a more powerful 2.4ghz band signal that would benefit me at all in my situation with the WRT54G's or if i may as well get a single channel "N" router.

    So i just now ran over and hooked in a WDS router across the street to my neighbors house, the signals are at about 40% right now.

    SO a few years back i posted my modded WRT54G, i installed a couple fans inside the housing, one pulling air in, and the other exhaust and they were side by side also controlled by a switch to turn them off. Point being, that i can jack up the TX power on this one, but need to find a happy medium where the power is high enough without too much noise to negate that power. I have the second router without the fans loaded up with some RamSinks so they will be able to withstand a little increase. Has anyone done this sort of research and found a solid number where you get a good signal with minimal noise??

    Currently i have only the 2 WRT54G's in WDS, i have a 3rd one for my detached garage but its not currently on while i make this connection the best it can be. They each have DDWRT v24 SP2 running, Both have the Yagi 15dbi directional antenna aimed at each-other. Then the other antenna has one of the Linksys 9dbi antennas that they used to sell. So from what you said:
    Is it pointless to use this second 9dbi antenna?
    Should i put the original stock 6dbi antenna on it? or should i use no antenna at all?

    I also saw that in the firmware i can choose to dedicate one antenna to send and one to receive or "Auto". Should these routers be communicating with only the Yagi antennas then?

    On the client side of the WDS bridge, I was trying to decide the best way to connect my neighbors computers. Should i allow them to connect to this network setup for the bridge? or should i connect their Router behind this one and let them connect as they did previously? Im not sure what type of router they have, if it is a router capable of the DD-WRT firmware, would you recommend adding this router to making the WDS mesh much larger? I was kind of thinking that i would either have this WDS SSID strictly for the network bridge, and then at each end of this network, there would be another wireless network for clients to connect to using another frequency.

    I'm going to quickly run the second Yagi over across the street to see if using them both, one for transmit and one for receive and simply use the 9dbi linksys antennas at my house.
  7. HennieM

    HennieM Network Guru Member

    Jgutz, you lost me. Maybe a picture will help... Anyhow, here a few things that might help:

    1) As mentioned above, the G routers use only one antenna at a time, and that antenna is used for both transmit (Tx) and receive (Rx).

    2) A router that is Tx-ing, is also Rx-ing at just about the same time, as it gets back acknowledgements etc. from the device it is talking to. Wireless is ALWAYS a 2-way street, and your signal strength, and consequently your speed, is only whatever the weakest direction in the 2-way communication allows.

    3) If you have only 2 devices talking wirelessly to one another, your best signal comes from a weak Tx signal strength and a strong antenna. Increasing Tx power is rarely a symbiotic solution:

    Ex.: If you have 2 routers, A and B, both with normal 2dBi antennas, and both set to a Tx strength of 10dB (or 10mW) you get say -70dB Rx strength on both routers.

    3.1) If you now replace the 2dBi antenna on router A with a a 10dBi Yagi pointed at router B, you should get an increase, on both routers, of about 8dB (to -62dB Rx strength). That is because (i) A is Tx-ing at 8 dB more to B, but also because (ii) A is "amplifying" via the Yagi the received signal from B by 8dB, so both the 2-way communication paths get stronger. If you put Yagis on both routers, you should see a 16dB increase in Rx strength (to -54dB) on both routers.

    3.2) Compare (3.1) with keeping the 2dBi antennas, but increasing the Tx strength on router A to say 18dBi: Now router B should Rx at 8dB more (-62dB), but router A still Rx at -70dB, so there's no speed gain, as your weakest of the 2-way communication paths is still at -70dB. On top of this, the noise generated by the higher Tx strength on A, generates noise for router A, B, and any other devices around, so you may even see a drop in Rx strength on A. If you increase also B's Tx strength, you will now get only -62dB on both routers. Compare to the double that gain in (3.1).

    Now, in the real world, it does not quite work like that, so the increase in Rx strength will probably not be 8 or 16dB, but the example illustrates the point.
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