New wifi network: Setup questions...

Discussion in 'HyperWRT Firmware' started by mscafidi, Jan 24, 2006.

  1. mscafidi

    mscafidi Network Guru Member

    I need some assistance in setting up a wireless network at my office. Here is a little background:

    Our office is rectangular in shape. The dimensions are 200'x75'. The plan is to install 6 WRT54Gv4's in this building so that we have adequate (and I think that is an understatement) signal strength throughout the building. One router will be installed in each corner of the building. The last two will be centrally located on opposite sides of the building. We have a T1 and Cisco router providing connectivity, so the WRT54G's will be used mainly as an access point. They will all be installed above the drop-down ceiling and are currently running Tofu 6.2 (to be upgraded later today to Tofu 12).

    Now for my questions: Considering that 6 routers will be present... which are the best channels to use? Should we use the same channel, alternate 1, 6, 11 etc etc? One side of the building faces several hotels and as a result is visible to a lot of wifi traffic (mainly on chan 6). Currently, the the tx power is set to 56mw. However, since the signal coverage is so good, I have been contemplating turning tx power back down to default. The plan is also to use the same SSID and WPA key on each router so that wireless users may roam the building. Is this a good practice to follow? Can anyone provide any details on how to better configure or tweak the equipment for the best network coverage possible? Thanks in advance for any help that you can provide.
  2. NateHoy

    NateHoy Network Guru Member

    A few thoughts...

    I'd wire them all together LAN port to LAN port and choose the same channel. Since you have competing traffic on channel 6 from the hotel, I'd avoid that channel, obviously, and probably set up some corner antenna reflectors for those units on the corners to cut down on signal leakage from your WLAN to the hotel patrons to avoid confusion and reduce the risk of hacking.

    (note: correction in previous paragraph based on better information from the next post on the thread - sorry for the confusion).

    I'd also set up reflectors on the walls next to each unit (or directional antennas) to reduce signal leakage as much as possible and keep the signal in your building. Then use the minimum power necessary to cover the entire building in solid signal. With as many routers as you are looking at, you may not need to run at more than 25% (21mW) or so, but it's worth experimenting. Keeping it as low as possible keeps the signal inside your office, or at least minimizes leakage outside.

    You may also set up two independent WDS networks on separate channels, to cut down on channel saturation. Mixing the signals (alternating access points) allows clients to roam on their network but provides two separate and independent networks on separate channels. 1 and 11 are probably good for what you want, if your major source of interference is on 6.

    You may also consider placing the units in a line along the center of the ceiling, or a double line 1/3 of the way in, with directional antennas pointed down. This will further minimize leakage out of the building, and give you really good "flood" coverage inside the building with any leakage going into the ground below you.

    Directional antennas can be as simple as a piece of cardboard folded to 90 degrees and covered in foil.
  3. RonWessels

    RonWessels Network Guru Member

    I'm not sure I agree with using WDS. If you can provide the wiring, connecting all the WRTs together using Ethernet cable will be the most reliable. Make sure to plug them into the LAN ports of the WRTs and leave the Internet port empty. Using the same SSID and security / password will allow free roaming throughout the building.

    Given that you have essentially 3 unique channels to use (1, 6, 11), a layout something like


    would maximize the spacing between identical channels.

    I do agree with at least considering using directional antennas. You can make some rather effective but cheap and easy versions here.

    I also agree that you are going to want to keep the transmit power on the low side to prevent interference. Experiment to find the best settings.
  4. NateHoy

    NateHoy Network Guru Member

    RonWessels -

    Sorry, you are absolutely correct. Ethernet cabled LAN-LAN is the way to go. In my stupidity, I misunderstood the description of WDS. Thanks for the correction.

  5. mscafidi

    mscafidi Network Guru Member

    Thank you for the replies. Just to clarify, currently each unit has a cat5 run to it which terminates at a 24-port 10/100 switch in our server room. I am not set on any particular channel combination. As a matter of fact, I was fishing for advice on channel selection. The interference from the hotel on channel 6 is only present on one side of the building (damn glass windows). The other side of the building did not pick up any other wireless networks in my site survey.

    I am in somewhat of a time limitation, and since the routers already have dedicated cat5 runs, I would probably rather shy away from rewiring for WDS at this point. Any more pearls of wisdom before I put the finishing touches on this network? BTW, thank you for the replies!!!

    You guys should see the way the WRT's are wired up. It's not PPOE, but I think it's cool none-the-less. In addition to a cat5 run for data, each WRT has a cat3 run to it also. Each cat3 run was wired for power. We twised all of the striped wires together into one strand, then twisted the solids together in another strand. We then used the factory transformer, tested for polarity and soldered a power connector to the cat3 cable for each unit. These wires terminate in our server room into an alarm box that has a 12v 4a power supply and a 7ah battery. This way, we eliminated the cost of having an electrician supply power above the ceiling at each location we wanted to place a router. The added benefit is that the 7ah batter will power the routers for about 2 hours in the event of a power outage. Pretty neat stuff, it's up and running as we speak and I'm pretty pleased with the results. It was a heck of a lot cheaper than having an electrician do a bunch of work, or buying all of the doodads assosiated with PPOE.
  6. NateHoy

    NateHoy Network Guru Member

    You can safely ignore my bit about WDS, it was an idiotic bit anyway. ;) The way you have it wired is much better.

    I'd slap together some of the reflectors that RonWessels mentioned to keep signal leakage out of your building at a minimum and signal strength inside at a maximum. They cost nothing to build, and are an easy add-on as they slide right on the existing stock antennae. You can adjust the angle as needed to focus or spread out the signal, and it'll reduce signal leakage to he hotel and reduce your risk of hacking.

    Of course, it goes without saying (right?) that your network is using strong encryption with a long hard-to-guess password or RADIUS or something. Lock that puppy down hard. Wireless is too easy to intercept.
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