Proxim AP-2500 802.11a and 802.11b Networks, Limitations on Roaming

Introduction

802.11a and 802.11b Networks

The AP-2500 supports both the IEEE 802.11a and 802.11b standards. The AP-2500 can be used with the following

combinations of 802.11a and 802.11b radio cards:

• One 802.11b card (second slot empty)

• One 802.11a 5 GHz upgrade kit (second slot empty)

• Two 802.11b cards

• One 802.11b card and one 802.11a 5 GHz upgrade kit

You can have an 802.11a and an 802.11b card present in the AP-2500 at the same time and 2.4 GHz and 5 GHz

clients will be supported simultaneously.

The coverage area achieved with a 2.4 GHz radio is generally larger than that of a 5 GHz radio (this is particularly true

for open spaces but less so for indoor applications). The transmit rate is higher in the smaller (5 GHz) cell than the

larger (2.4 GHz cell). The following diagram illustrates the difference in cell sizes. However, the best way to determine

the AP-2500’s actual coverage area is to test the range of a wireless connection using a client device.

Figure 1-3 802.11a versus 802.11b Coverage Area

Roaming is the ability of a wireless client to move from one Access Point to another while maintaining an uninterrupted

connection to the network. Most traditional Access Points support this feature. While the AP-2500 supports seamless

roaming from a radio perspective, in practice it does not support seamless roaming for subscribers from AP-2500 to

AP-2500 in a hotspot environment. Each AP-2500 maintains its own list of current subscribers that can access the

Internet; this list is not shared between AP-2500s.

Limited roaming can be achieved under the following circumstances:

1. A subscriber can seamlessly roam between two radios installed in the AP-2500. For example, a subscriber

with an 802.11b client can roam between the Access Point’s two 802.11b cells when two 802.11b cards are

installed. (This assumes that the two cells have the same Network Name and Encryption settings.)

2. If you use a RADIUS server to authenticate subscribers, a subscriber can move between multiple AP-2500s

but the user will need to re-login each time he connects to a different Access Point. This solution does not

provide seamless roaming.

NOTE

If you have enabled the Information and Control Console (ICC), a RADIUS user who clicks the Logout button

will not be logged out following a roam from one AP-2500 to another. The user will need to browse new pages

to bring up the login screen for the new AP and re-login when prompted.