Wireless apt building - 900 Mhz Feasable?

[vkolas]

Hi,

I'm asking for advice on implementing wireless internet in an apartment complex (about 50 units) sharing a T1 line.

I have extensive computer/networking background, but I'm new to the wireless arena - so please bear with me.

I did a bit of research and what I learned isn't very reasurring.

From what I learned, apartment buildings are an interference nightmare for 802.11b because of 2.4 Ghz cordless phones, wood, water, and i'm not even mentioning the vertical aspect of the apartment building itself (2 stories).

I recently heard that 900 Mhz is making a comeback because of its NLOS capability, and the dropping usage of the frequency. I do understand its drawbacks (1.5Mbits limitation).

If someone could point me in the right direction as far as AP placement (client & host), antenna placement ideas, and any advice/tips that will make my life easier.

Any help would be greatly appreciated.

Thank you in advance!
-Vic

[lwheeler]

Site Survey, site survey and then again site survey. The next thing is physical security of your devices. Better find a nice in-expensive enclosure for AP's and Antenna's.
Oh yeah, did I say site survey?
Larry

[jatkins679]

Originally posted by lwheeler
Site Survey, site survey and then again site survey. The next thing is physical security of your devices. Better find a nice in-expensive enclosure for AP's and Antenna's.
Oh yeah, did I say site survey?
Larry

I don't think Larry mentioned this, but doing a site survey is vital to figuring out what will and will not work for you. Your plan is big enough and you'll be laying out so much money for equipment that you really should do one because it may very well save you money and time later.

Just like any other WLAN, the use of directional antennas, proper AP placement, and proper number of APs can often do wonders (along with educating your users as to what to reasonably expect). But you really need a site survey to tell you what to do.

Did Larry or I mention the importance of doing a site survey? If Larry did allude to doing a site survey, I couldn't agree more.

[BER_vs_SNR]

Something that the previous answers ...surprisingly seem to underemphasize is the idea of a thorough site RF survey.

On top of that however I would like to add that you may want to lalso ook into deploying 802.11a instead of 802.11b. The absorption characteristics (from walls, doors, carpets, etc.) are different for instance from the ones obtained with either 802.11g (which albeit working in the 2.4GHz band attains in principle the same high bit rates but with different carrier frequencies and different encoding schemes for the subsequent modulation) or 802.11b which works in the same dreaded 2.4GHz band but is completely differently encoded.

If your site survey shows you can get by with acceptable reception everywhere when installing 802.11a APs the advantage is that you won't have the interference with applicances and cordless phones to hassle with and your devices will be faster to access the shared T1, hence you can support more devices per site (in terms of locally usable bandwidth) although the aggregate bandwidth they can use upstream to and from the Internet is of course bound by your T1 rate. It will be a simple calculation to see how many 802.11a APs beat the site survey constraints (due to increased absorption) at what cost to see if it is an economically viable alternative. Technically it willmake your life much easier.

For your information in case you are not aware of it, 802.11a has been found to perform better than 802.11g (at high bit rates) from a transmission range (at a given level of received power) point of view in empty spaces, down long hallways or corridors, etc. which may be for your apartment building may be a natural fit.

Good luck!

[HITMONEY]

I am going to come at you from a different angle.

Are you trying to become an WISP? Charging money for those units who wish to get there internet from you?

There are some impressive solutions now available for these applications.

Oh and do a site survey. :D

[vkolas]

I'm planning on building a niche doing wireless implementation/WISP for small to medium community enclosures such as apartment buildings, business parks, etc..

I would be interested to learn about different solutions available.

[vkolas]

Is there still hardware vendors selling 802.11a equipment?

regarding sight surveys - I'm definitely willing and able to do one. However, I am more interested in the theory of implementing wireless in a medium-to-large apartment building - assuming that murphy's law comes into play and interference is brutal - is 802.11b feasable? How about 900 Mhz? Someone mentioned 802.11a - that actually sounds more realistic.

Thanks!
-Vic

[BER_vs_SNR]

I did. The reason as I had explained is that the appliances won't go away and the interference in your targeted market will be real in the 2.4 GHz band.

Regarding transmission losses for 802.11a compared to other 802.11 flavors for starters take a look at a nice article by a couple of Intersil engineers at

http://www.commsdesign.com/design_center/wireless/design_corner/OEG20030114S0008

That will help you clarify some thoughts in your mind.

Your WISP idea is nice but I believe you will have a harder time to ultimately please customers with 802.11b or g for that matter.

By even thinking about 900MHz you are pushing yourself to the GSM/GPRS realm where things are rather kludgy for what you are trying to do, and where you are really trying to squeeze a square peg into a round hole, not to mention (i) that your work will be truly cut if you want to combine the two realms and (ii) that achievable bit rates are 2 whopping orders of magnitude (not just two factors, two orders of magnitude) below what 802.11a offers you.

I don't think you will end up having that many choices if you want to please customers. You can certainly deploy 802.11b or g but the problem isn't going to go away and in an apartment block even if one tenant is willing to forego heating up some popcorn if it means keeping the microwave oven idle and not disrupting the network, some others are bound to use it instead.

[BER_vs_SNR]

I don't know why the URL I gave you appears shortened, maybe for simple legibility. In any event igf you have a problem locating it, you can find the article at the CommsDesign.com site under Design Centers, Wireless LANs & PANs; it appeared on January 14, 2003 if you check their archive.

Another idea is to use an 802.11b outdoors-switch (like Vivato for example) with directional antennas back and forth to and from the T1 or whatever you will use for Internet access from the site. The directional antennas downstream to the apartments will be illuminating the building where you can use an array of gateways/bridges to connect the external 802.11b with the internally deployed 802.11a, which is precisely chosen to help you manage if not outright mitigate the domestic interference problem. Of course you will have to check the overall cost of this approach versus an all-802.11a solution but to my knowledge there are no outdoors 802.11a switches as of yet (I may be wrong), something that is probably not more than about one year away from market reality.

This in fact may actually give you a transition roadmap and path for the offerings to your first customers and a more stable solution as you evolve.

Hope this helps!