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The Wireless Networking Question Roundup...
Which 802.11b-enabled PDA?
Kent Brewster asks: "I've retired my Palm 7 due to sudden lack of all-you-can-eat service and lots of free WiFi in the area. Right now, I'm looking at HP's iPAQ h5455, Toshiba's e750, Palm's Tungsten C, and Sharp's as-yet-to-ship Zaurus 5600. What I'm after is the best possible mobile Web experience first and PDA functions second. Opinions, please?"
802.11b Issues for Apartment Complexes? (Revisited)
johaninroseville asks: "I am in the planning stages to build a wireless network to provide an apartment complex with last mile Internet access. There are about six hundred units, but only one to two hundred interested people. For those curious as to the general layout of the apartments, here is an overhead picture.
My experience with radio frequencies, antennas, and especially how well radio waves can penetrate walls etc is rather limited. My game plan is to get a feed into the POP / MDF, and have a rather strong omni antenna mounted on the roof of that building. The coverage of that omni antenna will provide the links to the seven APs that will probably be needed, mounted on the rooftops around the complex. The seven IDFs, (or APs or what ever you want to call them) will each have a Point-to Point connection to the big omni antenna. Hardware used for the seven IDFs is planned to be: directional antenna (for link to omni in POP) connected to bridge, bridge connected to AP, AP connected to a sectored panel antenna that will provide end-user access (to their PCMCIA/PCI/CF/USB Cards, or to their access point).
My biggest questions are what antennas to use? What strength? How well can the radio waves from an omni antenna and/or a sector antenna penetrate multiple walls, if at all? How far can one of these antennas cover, and then penetrate walls?
I would appreciate any help at all in this matter. Maybe somebody has done something similar, or have some useful links."
Ask Slashdot last covered wireless apartment complexes about a year ago, and it would be interesting to note if any of the new technologies, introduced in the interim, will make this job any easier.
Outdoor Enclosures for 802.11b Equipment?
And finally, this question from ETEQ: "I need to operate a small amount of networking and wireless equipment (Router, Cable Modem, and 802.11 access point) in an outdoor setting, but the problem is that I live in Minnesota, where temperatures can drop far below freezing and stay that way for weeks (not to mention frequent heavy snow)... Are there any outdoor enclosures that can be purchased on a Home or SOHO budget?"
Many apartments have pretty thick ceilings and floors so the signal shouldn't get too far vertically, though the neighbor on the other side of the wall might want to bum some free internet and pr0n downloads on your expense. Solution: secure that network.
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Free your mind.
couple things to consider:
the main problem in my experience is wall penetration. Don't count on more than 3 walls (and this is stretching it if they are concrete). Consider mounting the antenna outside a bit away from the building, essentially hitting the outside wall. This will give you only one wall for all apartments.
Don't forget about accountability and security. Even if billing is not an issue, you don't want someone in your building to go wild and start a hacking crew. Static IPs are a bit accountability help, NAT is though
---- join dshield.org Distributed Intrusion Detec
... it won't work. At least, it won't work very well.
There are only 3 non-overlapping 802.11b channels, or 4 if you do it right. Either way though, that isn't 7.
However, if you can get it down to 3 or 4 links, don't use omnis anyway - use some little 8dBi-14dBi patch antennas, and do highly directional links to the radios you're bridging to. You only want to use omnis for client (think people moving around, unknown target direction) access.
The above is what the traditional thinkers would say. And what you were probably thinking, given the fact you said "point to point" link for the omni -> client links.
You can get around that barrier, however, if you do a single AP at your POP, and the bridged radios are simply looking to the AP for client access. The downside to this is that all the bridged radios will be sharing the bandwidth of a single channel, but you can have 7 (or more) links from your central antenna this way.
And if you're going to do it that way, get two 15dBi 180-degree sector antennas (cell-site quality), put them back-to-back, and do a combiner feed to your AP box.
You'd better let the residents know that they shouldn't be using 2.4 GHz cordless phones on the premises, or they'll be knocking out the wireless connections for computers in the area.
Here is a link to acompany that proved useful that last time I was installing wireless LAN's.
http://www.hyperlinktech.com/index.html. They have a full assortment including heated outdoor enclosures and antennas and amplifiers and AP's and more!
I had the "pleasure" of using the 5455 and I found it to be completely useless. Unless you are somehow attached to the ipaq style or whatever (and you come from Palm) I would not suggest this as the Wifi Pocket PC of choice.
I would suggest the Tungsten C. I borrowed it from a friend for a day and was utterly impressed. The Palm OS 5 is very peppy with the new processor and the battery life is simply amazing. Most Pocket PC devices can only last about 7-10 hours, and only 2-3 with wifi on. However, the C can last up to a week, or a good 11 hours with Wifi. Not only that, but it does a better job rendering. Considering you are coming from a Palm device, I would recommend this C because programs will also be compatible.
This is my digital signature. 10011011001
Here is a great node on SeattleWireless.net's wiki that details the construction of an outdoor wireless access point, using relatively cheap equipment found at a hardware and/or electrician's store.
o fBoxes
http://www.seattlewireless.net/index.cgi/WaterPro
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And the Angel said unto me, "These are the cries of the carrots! The cries of the carrots!"
I wouldn't consider it a PDA actually. The Zaurus 5500 is more like a real computer, just small and less powerful (less upgradable too). But nonetheless, it is very powerful and you can have pretty much anything that's compilable.
:) Or watch movies from my NFS server, etc. I don't use other features like agenda or address book so I can't say about those. On the wireless side though, it's excellent. I guess it also depends on the type of card you have. Just make sure you have one that's supported under either the "stock" Zaurus ROM or OpenZaurus (which is way better)
:)
I'm a linux freak (and admin) so this is a nice tool for me. I can ssh to work from my living room and fix stuff at home
Also, since it's Linux based, things like Kismet are ported and work real nice. The only drawback is the battery and I consider buying a less powerful 802.11b card as mine is not power-friendly. Other than that, I get good milage with a base at work and at home. I rarely use it for more than 1-2 hours. I can't wait for the Sharp "C" series to be available as it will have a bigger keyboard. Until then, I'm glad I ditched my Palm Vx, it was useless
-- Leeeter than leet
If you don't mind Sony and all the baggage that comes with them, their clamshell PDA's are outstanding wireless PDA's. They have a CF slot dedicated to just being used for 802.11b cards (though if you buy a 3rd party driver you can also use CF memory cards in it), and they have the best screen bar none on PDA's to date. 320x480 of web-browsing pleasure (well, relative to other PDA's anyways). That's twice the resolution of any PPC-based handheld.
The ones you'd want to look at if you're interested are the NX60, NX70V (same as NX60 with a crappy camera), and the NZ90 (only if you're really into getting a gigantic PDA with an actually decent digital camera built-in).
Back in the early nineties I spent some months doing indoor radio propagation measurements in the 2 GHz band. Basicly there are a few rules to observe when designing a wireless link:
1: In free space the signal strength is inversively proportional to the square of the distance. Double the distance and the signal drops by 6 dB. Increase the distance by 10 times and the signal drops by 20 dB.
2: Walls, buildings and trees attenuate the signal. As a rule of thumb a concrete wall attenuates the signal by 20 dB. Transmitting around a corner attenuates the signal by 10 dB. Wooden doors and windows will let the signal pass through with a typical attenuation of 10 dB.
3: Big flat surfaces reflect the signal. This means that you might be able to connect to a friend in the same appartment block by "reflecting" off the building on the other side of the road, even if the direct line between you is obstructed by several concrete walls.
Let us assume that the coverage of your wireless link in free space is 500 meters when using omnidirectional antennas. If you increase the antenna gain by 20 dB the coverage will increase to 5 km. If on the other hand you have to pass through a concrete wall then the original 500 meters will be decreased to 50 m. Add another concrete wall and we are down to 5 meters!
As I understand your apartment complex project the users should be able to use their WLAN cards in all rooms of the flats. To be on the safe side you need line-of-sight between the access point and the facade of each flat. This of cause would require quite a lot of access points.
Alternatively you might be able to use a few access points located at high points even if there is not line of sight to each flat. The signal would then be scattered and reflected of the neighboring buildings. This however would attenuate the signals, and your poor users might have to stand by the windows to get a good connection.
To solve the channel problem, consider this:
.11a gear with directional panels pointed back at the master. Set them to bridge the wireless side to their ethernet jacks. Now you've essentially got "wire" to all your locations, without stepping on the 2.4GHz spectrum.
Use a single 802.11a AP on the roof above the MDF with a decent omni on it. Then, at your other locations around the complex, use more
Then at each location, connect one or more 802.11b/g APs to the ethernet. I say "or more", because you may wish to use several APs with narrow sector antennae, to provide stronger signal to a broad area.
Another poster pointed out, you'll have to make people swear not to use 2.4GHz cordless phones. Since 802.11b isn't really spread spectrum, it doesn't handle interference well.
People in their apartments will need to realize, they're not aiming for the AP on their own building, they're aiming for the building across the way. Explain that 2.4GHz is line-of-sight, so if they can't visually see the AP, they might have problems. Consider marking the rooftop locations with flags.