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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?"
make a waveguide antenna with a coffee can. it should last ok, and if it rusts, it is easy to replace.
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
for wireless pdas, the ipaq 5455 is really the way to go. wifi, bluetooth and finger print recognition. add to that, the ipaqs have tons of accessories, so you can even use a gsm card and use the ipaq a cell phone (and gprs / gsm data services). also, the ipaq along with a t68 or nokia 3650 is a pretty good combo too.
cheers,
pt
... 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 have built two splashproof computers for marine surveying on small boats. Pelican cases are what I used. You only need to seal the one or two through-case holes that you will need to run your wires.
I would post a link to some pics, but my home server can't handle the Slashdot effect.
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
I've tried browsing through Pocket IE on a Dell Axim...and man does it suck. It is basically IE 3.02 or some ancient crap like that, modified and stripped down to work on a PDA.
I can't wait for the day that Opera runs on a PocketPC.
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
for wireless pdas, the ipaq 5455 is really the way to go.
It's likely to take the best part of a year (going on past experience) for HP to get Linux working on this model as well as it does on the 3[68]00s. Also bear in mind that there will probably never be native support for SD cards, though MMC cards do instead.
You really, really want to avoid being stuck with PocketPC for any length of time, trust me.
# init 5
Connection closed.
Oh...
the first Airport products? Because they are selling 802.11g products now so it's quite likely that their cards will continue to be supported wherever 802.11g eventually ends up.
As for browsing from a PDA, I've found Thunderhawk from Bitstream invaluable. I've found it to render pages in about the same time, sometimes even a little faster, although there are delays when scrolling up/down on a page. The big advantage is that it is able to scale a page, rendering it at the equivalent of up to 800x600 on a pocket pc PDA. I can view slashdot, as it looks on a PC, from my iPaq. There is a yearly fee of $50.00, but you can get a one month free trial if you're interested in it.
http://www.bitstream.com/index.html
My $0.02.
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).
I'll second that. APs to APs as distribution is unworkable. There are only 3 channels you can use on 802.11b which don't overlap, and you can't have an AP retransmitting on those or nearby frequencies without dropping your transmission speed to modem levels (or worse).
/. ;-), I'm also going to post my real world experience under the also realistic post by JWB
If you can't pull/hijack some wire pairs from the PoP to outlying buildings, then you will have to go to an 802.11a distribution backbone, with the APs routing/repeating the signals onto 802.11b. That means the APs will be even more expensive with 2 sets of wireless cards and 2 antenna fixtures. Even with a dual system, you still have the problem of 200+ apartments trying to suck up 1.5MBytes/sec of bandwidth divided by 7 APs. Dialup modems will be faster. Your APs most likely will need to have copper connections back to your routing closet/MDF, to keep the airwaves clear for APapartment signals.
If you really want to do this correctly, hire a networking expert to calculate the bandwidth needed for 200+ apartments at peak usage (7:00 PM), and distribute that with a multiport router and 100Mbit/sec switches. Or start with a single set of buildings and a single AP, and grow from there.
Then google up wireless authentication projects, like NoCatAuth, to install on a server between your APs and the internet. You must have authentication, otherwise how can you bitchslap some idiot who continuously DLs the latest linux ISOs? You will almost certainly need to enable WEP or promote cards/drivers that support WPA or newer security protocols to protect neighbors transmissions. There is a lot of security things to consider if you don't want to be on the receiving end of lawsuit happy ex-resident for allowing his precious kiddiepr0n DLs to be intercepted by the nosy lady in apartment 27b.
My normal advice would be to talk to the local telco and see if they would put a DSLAM into the PoP for your complex and then they could sell DSL service. But if Roseville is in SBC territory, then keep dreaming about making a wireless system, its your only chance.
After all the professional sounding advice (you get what you pay for on
the AC
Hemos is like...sci-fi fans;he thinks technology is cool, but he hasn't bothered to understand the science it's based on
Ok, so now you are probably more confused than when you started. People are bombarding you with stuff like "use different channels", "why not cable each AP" etc. Your basic idea is to avoid ethernet cables to the APs and personally I think this is a good idea, as you may find you have to stick extra APs in all sorts of out-of-the-way places to cover black spots. I'll continue this post on the assumption that you are going to stick with this plan and use radio to feed the APs rather than cable.
(note: your biggest issue in this is going to be which access points to use - more on this later)
Different channels? - This WOULD be an issue if you were cabling each AP to a network behind. But since your APs must talk to each other then ALL your APs must be on the same channel. Now I'll have to start with a couple of disclaimers before everyone jumps on me. This means that your overall bandwidth will be reduced. In an office environment this type of scenario of having many APs sharing the same bandwidth is not acceptable. HOWEVER in your case most of your traffic is going to the internet, and your pipe to the internet is limited anyway. Therefore this isn't a big issue for you. There is an alternative design where you use one set of APs on one channel for your feeder network, and a different set on a different channel for your access network. This doubles the amount you have to spend on APs, and won't make a huge difference in your setup anyway (more later when I talk about APs and their limitations).
Now when your APs talk to each other they are using bridging mode. Many manufactures support bridging mode. When clients talk to the AP they are using what I'll call client access mode. Pretty much all the manufactures support this (naturally). So fine, everything sounds good right?
Well if you really read the fine print (assuming it even exists on the website of the manufacturer) you'll see that there are almost no manufacturers that support both bridging mode and client access mode AT THE SAME TIME IN THE SAME AP. Usually the vendor will propose a design where one AP handles the bridging to the central AP, and this AP is then connected via an ethernet cable to the back of a second AP which provides the client access on a different channel.
But there is good news, there are some APs that can do both modes at the same time.
They are (as far as I know - happy to be corrected here): Cisco 350 (and probably the more expensive ones), a HP model (can't remember the model number), the Apple Airport Extreme, and the Meshbook.
The Cisco 350 is a little pricey but will give you better range due to the fact that it can output the full 100mW. It also supports power over ethernet natively (not an issue in your config though), and is available in a rugged outdoor version. http://www.cisco.com/en/US/products/hw/wireless/ps 458/index.html
I'm not familiar with the HP one, so I won't talk about it here.
The apple airport extreme is very interesting because of its low cost. It is the only AP in the low end price range which can do client access and bridging at the same time. You'll have to use an external antenna with it because the internal antenna will not be powerful enough for your needs. It won't output the same power as the Cisco though. If cost is an issue this is the one you want, though with the Cisco you may end up with less access points and therefore save money. http://www.apple.com/airport/
Something that is very interesting is the meshbook at http://www.meshbook.com it is an AP running linux and some open source software which solves a lot of the problems of community networks. When you use a Cisco or Apple AP you are going to be able to use only a single exit point to the internet, but the meshbook is much smarter and a collection of these in a network together will be able to load share to multiple exit points. This way you could get two feeds in at either end of the complex, and if you placed a few extra meshbooks into the design for
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.