Wireless LAN Project

[gavin.mckee]

Hi there,

I'm hoping that someone with experience in 802.11 can give me some help. I've just been asked to look into the fesability of replacing the wired infrastructure in one of our offices with wireless technology. The office would have approx 40 workstations Windows,Sun + some laptops. We would aslo be providing wireless for Clients who come into the office for meeting presentations etc. The dual band access points seem to be the best option but I am wondering how many access points I would need to provide an excellent service to the user base. Would I need to use a wireless LAN controller? Maybe is it just better to use a wired infrastructure?

[scottmac]

For the foreseeable future, wired networks will always outperform wireless (at least in an office / inside scenario.

Wireless is subject to interfering signals on either band (though 802.11a is much cleaner, and has many more non-overlapping channels).

Security, if properly implemented, is roughly the same ... some caveats, some wrinkles, but generally equal.

You can, with extremely rare exception (these days) connect pretty much anybody's Ethernet NIC into your network, and it'll connect, and you'll get pretty good performance.

Wireless is still having some interoperability issues, even among WIFI-compliant components (scan the wireless forums here ... look for "Symbol", "Intel", "Centrino" ...)

Wireless is great for the laptops & portable devices, it's convenient for your guests (assuming compatibility, reasonable security , etc... see above).

Depending on your flavor of Sun, you may or may not find a reasonable wireless solution, outside of a wireless bridge ... even today, there can be problems between (SOME) Sun equipment and Cisco switches.

For my two cents, I'd recommend you wire / re-wire the office and stay connected when possible. Provide wireless (it truely is a wonderful thing), but don't bet the business on it.

Good Luck

Scott

[ethiel]

Here are my thoughts on your questions:

You mention replacing a wired network with the wireless. For laptops this adds mobility, but workstations will generally have more reliable and faster connections via wire than wireless. If it is a new environment, the cost avings of wireless would be the main reason to consider it over hard wiring all of your computers. For laptops, most of my customers add wireless to an existing wired network, but many keep wires at their desks for when their laptops are docked. Again, you gain a little performance with wired in general.

For vendors and conference rooms wireless is a great idea. It allows mobility and saves you from having to wire ports for vendors to use when on site.

The last question is not possible to answer based on the information you gave us. To answer that question properly you should perform a site survey. That would determine optimal placement of APs based on wall composition and required uses (VoIP requires more dense deployment than data).

As for wether you need a controller, it might depend on how many APs you want. If you just want an AP in each of 3 conference rooms, it may make sense to stick with autonomous APs which do not require a controller. However, if you want to do your entire building, controllers offer many benefits. They make administration far easier, and offer features like auto-rf which allows the controller to manage power levels and channels for the APs. If one AP dies, it can turn the power up on surrounding APs to compensate.

Eric

[johnruffing]

I am in agreement with the earlier comments. However, the real consideration has to do with how much bandwidth your applications require.

After you determine the amount of bandwidth the applications on your wireless clients will require, you have to consider the useable bandwidth available by a wireless infrastructure. Please note that, even at a 54 Mbps data rate, actual throughout is going to be somewhere in the mid-20 Mbps range (per radio) - and that assumes that there is only one wireless client connected to the AP.

Since it would be very unusual to see an AP dedicated to a single wireless client, you can safely assume that you will have multiple wireless clients per access point.

As you add more wireless clients to an access point, throughput for each individual client goes down since the mid-20 Mbps (per AP radio) of available bandwidth must now be shared among all the other wireless clients that are connected to that access point. This is because the wireless domain acts effectively like an old-fashioned hub (aka. Shared Ethernet) where RF clients can hear other RF clients (if they are close enough) and where one RF client will have to wait for the other RF clients connected to that access point to stop transmitting before it can transmit.

While it is true that all workstations may not be transmitting/receiving large amounts of data all at the same time, you will likely find that, due to the limitations discussed above, wireless is probably not going to be a viable replacement for a traditional wired infrastructure in most cases. However, it can provide a terrific overlay (where workers need to move around into conference rooms, Voice over WiFi, barcode scanning, etc.)

When determining how many access points you will require, part of the process includes a wireless survey helps you understand how wireless will perform in your building. But again, also make sure you understand how many clients will be attached to an AP and the bandwidth that their applications will require.

As far as using a WLC, you need to evaluate the features that the WLC gives you (additional security features, manageability, support for limiting guest user accounts, automatic RF adjustment, etc.) and determine if those features make sense for your application.

Hope this helps.

- John

[gavin.mckee]

Excellent information from all that posted. Thank you very much! Note the rating :)

[zappolinom]

Hi Gavin,

i could give you following way to think.

Put the laptops definetely to WiFi.

Look at how many square meters you want to cover especialliy trhe areas where the people tends to work(mmeting rooms hallway coffee/Break room).

Keep in mind if you want to use VoIP (WiFi) in Future, so you need perhaps additional coverage. The Workstations needs to be investigated, what apps they are running. If you use CAD for example or large files then you need to tend to a wire that Workstation.

I calculate that a 802.11b/g AP covers nearly 400-500 m2 in best conditions. Look at the AP as a shared Hub and attach between 15-25 Users simultaneously (conservative). So in your case i would use a a Switch with PoE Ports and dual Power Supplys. In this case you don't need to cable the electrical power to the AP.

[t8z5h3]

the only thing is that you will need a active type of varus/spywere software or hardwere so the netwoked computers /router switch ect... it not effected by a person that take there laptop home to do work.