Ask the Wi-Fi Guru, Episode XXII

By Aaron Weiss

December 04, 2009

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our Guru considers ways to connect to a nearby WLAN from a truck or RV, researches compatibility between a popular Wi-Fi router and DD-WRT, and helps a reader bridge the gap between an Airport Express and another Airport-based network.

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our Guru considers ways to connect to a nearby WLAN from a truck or RV, researches compatibility between a popular Wi-Fi router and DD-WRT, and helps a reader bridge the gap between an Airport Express and another Airport-based network.


Aaron Weiss'tis the season, as they say, when we will appreciate our wireless networks more than ever. Thanks to Wi-Fi, we never need to leave the couch. And thanks to the continual feasting that lasts from approximately November to January, getting off the couch is pretty much impossible anyway. This December, the Guru's stocking is stuffed with a bounty of shiny new questions. Unfortunately it will be impossible to cover them all in one column, so if yours is missing please check back for January's episode. From the couch.

Wi-Fi Connectivity from a Truck or RV?

Q: I work for a technology company with a product that requires a small tablet computer and/or PDA that is resident in the cab of a truck. The problem is that these mobile devices do not have an external Wi-Fi antenna. When the trucks pull in for loading on the loading docks I want to up/down load information to the tablet but the signal in the cabin is weak. Given the distribution of the dock, the signal is inconsistent, even with multiple 'repeaters' dotted around the place. Can I bridge the signal from another repeater on the roof of each truck? If so, what is the implication of 20 trucks each having their own repeater tapping into the single SSID from the central server? – Robert

A: Without more detail about the docking facility, allow me to make an educated guess: Perhaps the weak and erratic wireless signal picked up by these mobile devices is in part because they are inside the cab of the truck. That is to say, the truck itself is a thick metal cage which may be blocking much of the signal. Worse yet, as you say, these mobile devices have only puny internal antennas.

I would not worry too much about the implications of 20 trucks associating with the primary router. Twenty clients is not all that many in a LAN, even if we assume all twenty trucks dock at the facility simultaneously.

The bigger issue is getting good signal into the truck cab. You could install a router modified to behave as a repeater, but we don't know if even that will receive a stable signal from the docking facility since the router will also be inside the cab.

Although my experience in this area is limited, it seems like the key to any repeater setup is to focus on getting a good signal from the facility and that means an external antenna. On that note, I am intrigued by a product like this RV/truck "bridge kit" from EnGenius. The kit seems to include a powerful, weatherized outdoor antenna with a compact bridge to associate with the source signal. You feed the unit with an Ethernet cable which carries both power and data. Although they advertise this as something you would connect to the Ethernet jack on a PC, it seems like you could simply instead connect it to a stock wireless router inside the cab. Configure the stock router as a "dumb" AP (access point) by disabling DHCP and firewall, and it should relay a strong signal to any handheld device inside the cab.

Is the Netgear KWGR614 Supported by DD-WRT?

Q: I just purchased a Netgear KWGR614-100NAR from eCost. It was supposed to come with DD-WRT loaded on it, but it had the regular Netgear interface instead. Also, I noticed KWGR614 was not listed in the DD-WRT.COM database.

My questions:

1. Does the KWGR614 support DD-WRT?

2. What processor chip and how much memory does the KWGR614 have?

-Dennis

A: The KWGR614 is an interesting case, and worth talking about here in case other readers run across it. Although this product is now discontinued, models may still be available through discount and overstock merchants. Netgear marketed the KWGR614 as an "open source" router. It would seem logical to conclude, then, that it could run open source firmware like DD-WRT or Tomato.

But no. The KWGR614 is open source in the sense that Netgear provided the source code to the router, allowing developers the opportunity to customize it much like Linksys' original source code for the WRT54G has evolved into DD-WRT and Tomato, among others. But this hasn't really happened and, furthermore, the KWGR614 uses a Realtek-based chipset which is not supported by DD-WRT or Tomato. In other words, these popular open source firmwares will not run on the open source KWGR614. In principle, somebody might be able to modify these firmwares to work on this router. But to my knowledge, nobody has. It sounds like the vendor may have been misinformed in this case.

That said, there is a small developer community that has enjoyed modifying and customizing the KWGR614, and this unit may still be of interest to hacker-minded folks.

Building a Bridge Between Airport Networks

Q: I live in a building where the landlord has set up a Wi-Fi router for the tenants to share his Internet connection, using his password. I also have an Airport Express to wirelessly connect my printer to my MacBook Pro, and to stream tunes from the MacBook Pro. Currently, I have to switch between the two networks.  I can have Internet, or tunes-and-printing, but not both. I have determined that I need a wireless repeater or analogous functionality, while making sure other folks with the building's router's password are unable to see my personal LAN. - Carl

A: For readers not familiar with the Airport Express, it is a very compact wireless router sold by Apple. The AE is about the size of a wall-wart and features just one Ethernet jack with no LAN ports. The unit provides additional functionality through a USB port and an audio jack, used for sharing a printer and distributing audio via remote iTunes.

Although the Airport Express is not itself a wireless repeater, you should be able to accomplish your goals by simply adding another router configured as a wireless bridge. You can do this using either DD-WRT (using "client bridge" mode) or Tomato (using "wireless Ethernet bridge" mode), although Tomato may be simpler to configure for such a straightforward situation.

Your bridge router would pick up the signal from your landlord, using whatever security protocol and password is in place. You would connect an Ethernet cable from a LAN port on the bridge router into the (only) Ethernet jack on the Airport Express. The Airport will treat this connection as if it were any incoming broadband connection from, say, a cable or DSL modem.

If you configure your Airport to use encryption (WPA2 recommended), neighbors will not be able to connect to your LAN. Your LAN devices, connected to the Airport, will be able to use the Internet.

As an aside, because you would be using two routers in combination to extend your landlord's connection you won't suffer a 50 percent loss in network bandwidth, compared to using a single router as a repeater.



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