Browse Prior Art Database

Enhanced WLAN Broadband Beacon Format

IP.com Disclosure Number: IPCOM000131209D
Original Publication Date: 2005-Nov-09
Included in the Prior Art Database: 2005-Nov-09
Document File: 3 page(s) / 53K

Publishing Venue

Motorola

Related People

John Buchalo: AUTHOR [+3]

Abstract

In an urban environment, a highly concentrated number of IEEE802.11-based broadband access points (APs) may exist within a small geographic region. To enhance station mobility, all of these APs can be placed on the same network. This is typically advertised by broadcasting the same service set identification (SSID) field within the beacon of each AP.

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Enhanced WLAN Broadband Beacon Format

By John Buchalo, Michael Reuter, Tim Sherburne

Statement of Problem


In an urban environment, a highly concentrated number of IEEE802.11-based broadband access points (APs) may exist within a small geographic region.  To enhance station mobility, all of these APs can be placed on the same network. This is typically advertised by broadcasting the same service set identification (SSID) field within the beacon of each AP.

The problem addressed by this paper is that in this type of deployment the mobile user cannot differentiate among the APs based upon unique services hosted by each AP.  For example, the mobile user may want to connect to an AP that is hosting a particular video camera within a bank.   However, there is no way to distinguish between that AP and the one in the bank across the street.

One approach to solve this problem is to append a unique identifier to the SSID of each AP such that the first N bytes of the SSID signify the network and the remaining bytes uniquely identify the AP [1].  However, this method is limited because the maximum length of the SSID field is 32 bytes.  Also, because this approach violates the concept that the SSID is a network identifier, there is an interoperability issue because clients that do not support this feature cannot identify correctly the wireless network.

Proposed Solution

The proposed solution adds a new location specific identifier (LSI) information element (IE) to the beacon that advertises unique services offered by the AP as shown in Figure 1.

This IE will be indexed with an Element ID currently unused in the IEEE802.11 standard.  Then there is no interoperability issue because according to the standard, legacy clients will ignore this field.

The length of the LSI in bytes is given by the one-byte Length field in Figure 1. So in principle the LSI can be up to 256 bytes, although in practice it will be shorter. As with the SSID, the LSI consists of a null-terminated string of ASCII characters.

Figure 2 displays the sequence of messages at multiple layers that are involved with service-based connectivity.  The sequences can be divided up into three stages: Service discovery, network connection, access of services.  In the first stage, the client listens for beacons from APs within range and transfers AP identifier information including the LSI back to the host for display to the user via the GUI.  In the second stage the user selects an AP for connection based upon this information. And in the third, the user access the services offered by the AP.

Use Cases

One “application enabler” use case for this proposal is the selection of APs hosted by various “high risk buildings” suc...