Deploying Wi-Fi in the Enterprise
By Chris De Herrera, Copyright 2003
 Version 1.00  Revised 10/29/2003

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Introduction

Recently, I was asked about my experience deploying Wi-Fi for events like the Pocket PC Summit. At the Pocket PC Summit, I deployed up to 20 access points and had approximately 500 simultaneous Wi-Fi connections.  This article assumes that the reader is an experienced network engineer.

Items to Consider

I've summarized a list of my thoughts on deploying Wi-Fi below:

1. There is no perfect network � the Wi-Fi experience is very dynamic so do your best to get the settings right on the access points. Make sure that they all have the same revision and it�s current. I�ve found that Symbol�s APs have worked really well when I�ve deployed up to 20 of them.
2. Make sure you broadcast the SSID, use DHCP (check it with the Pocket PC too � not all DHCP servers work them them! � for example Cisco router�s DHCP do not). Also, use long headers for sending as well.
3. I suggest using an Ethernet switch or series of Ethernet switches to connect the Access Points (APs)  together. That way the maximum bandwidth can be provided to each AP. Also, I would use only ONE IP address scheme and subnet mask for the whole event. DHCP is great but most of these devices when roaming do not switch IP addresses automatically. I�ve used a Windows 2000 server configured with NAT so all clients used a 10.0.0.0 address with a subnet of 255.0.0.0 so there was the possibility of about 16 million clients. That way you don�t care if a user holds and address or not. (at CES in Las Vegas this year (2003) they limited the number of clients to 255 due to poor planning in this area!)
4. Watch out for overlapping channels � only channels 1, 6 and 11 are not overlapping in spectrum. If you have overlapping channels see if you can reduce the power of one of the APs that has that problem. I suggest testing at 11 mb/s which will reduce the distances covered significantly.
5. Find out the maximum number of expected visitors and the expectations for the number of Wi-Fi clients. Basically each AP can only handle up to 50 clients at once. The APs have to store the mac address of the client to know where to send info to them so there is a table built into them. This is the same info you will need to size the IP address scheme
6. Get a floorplan with distances so you can identify where you think the APs should go � keep in mind they should be about 100 meters (300) feet apart. When installing the APs use a program to check the noise levels in each area before installing the APs. You need to know if there�s a particular conflict in frequencies before getting started. Symbol has a survey program for the PC that works well for this. Also, after the APs are installed walk around the area and check for dead zones. Things like elevator shafts and pillars act like obstacles to the signal.
7. I would not buy 802.11g APs right now � they will not operate faster since they have to operate at 11mb/s to handle existing Wi-Fi clients even if you have 802.11g clients as well. If you do buy them, then make sure they are upgradeable from a reputable vendor.
8. One other bug I�ve found is that some vendors at locations want you to use their equipment. I have yet to find a hotel or venue that was doing a good job configuring and maintaining their network so be careful! In some cases they block certain TCP/IP ports with their internet connectivity or they do not allow local switch ports to communicate together.