Advertising Support For A Plurality Of Service Networks By A Wireless Access Point
Technical Field
[0001 ] The invention relates generally to advertising that a wireless access point
supports a plurality of service networks.
Background
[0002] Wireless access networks are increasingly becoming popular as the preferred
technique for performing communications and/or accessing online resources, .such as
informational websites, online stores, and so forth. One popular type of wireless access
network is the Wi-Fi network (also referred to as the wireless local area network or WLAN),
as defined by various IEEE (Institute of Electrical and Electronics Engineers) 802.11
standards. Wi-Fi networks can be provided in airports, hotels, stadiums, retail outlets, and so
forth.
[0003] A Wi-Fi network is made up of a collection of access points with corresponding
coverage areas. A user terminal within a particular one of the coverage areas is able to
perform wireless communication with the corresponding access point, which enables the user
terminal to establish communications sessions or to access network resources, such as
resources available on the Internet. Traditionally, such a wireless access network is
connected to a single service network managed by a service provider. Users can subscribe to
services provided by the service network, such as by entering into long-term subscription
agreements or by paying for short-term (e.g., 24-hour) subscriptions. According to the
802.11 standards, service networks are referred to as subscription service provider networks
(SSPNs). An SSPN is a network controlled by a subscription service provider (SSP) with
which a user of a user terminal has an established relationship. The SSPN maintains user
subscription information.
[0004] More recently, efforts are underway to define mechanisms to allow an access
point, and by extension an entire wireless access network, to support multiple service
networks (e.g., multiple SSPNs). However, conventional solutions do not address how

information relating to the multiple service networks supported by any wireless access point
can be efficiently advertised to user terminals.
Summary
[0005] In general, according to an embodiment, a method to advertise capabilities of a
wireless access point includes communicating, from the wireless access point to a mobile
station, messages at plural levels of detail to advertise that the wireless access point supports
a plurality of service networks.
[0006] Other or alternative features will become apparent from the following
description, from the drawings, and from the claims.
Brief Description Of The Drawings
[0007] Fig. 1 is a block diagram of an exemplary communications network in which
some embodiments of the invention can be incorporated.
[0008] Fig. 2 is a flow diagram of a process of advertising information relating to
multiple service networks supported by a wireless access point to a mobile station, in
accordance with an embodiment.
[0009] Fig. 3 is a block diagram of a wireless access point according to an embodiment.
Detailed Description
[0010] In the following description, numerous details arc set forth to provide an
understanding of some embodiments. However, it will be understood by those skilled in the
art that some embodiments may be practiced without these details and that numerous
variations or modifications from the described embodiments may be possible.
[0011] In accordance with some embodiments, a mechanism or technique is provided to
efficiently advertise that a wireless access point of a wireless access network is able to
support multiple service networks. A "service network" refers to a network to which a user
can subscribe (cither on a long-term or short-term basis) to access services provided by the
service network. For example, once the user has subscribed to the service network, the user
will be able to access network resources (e.g., Internet websites, online stores, etc.) and/or to

perform network communications (e.g., e-mail, text chat, etc.)- Note that user subscription is
not the only basis for access to a particular network—it is just one example. Another
example involves a wireless access network located in an airport. The wireless access
network may deliver, for example, four service networks: below the floor operations (e.g.,
luggage handling), airline gate terminal operations, retail establishment operations, and
public access. Within the latter category, the public access may embody several service
networks with corresponding service subscription providers. For the other service network
categories, the user terminals will typically/primarily select the appropriate service network
based on its wireless network ID (identifier) string (called the Service Set Identifier, SSID).
However, that does not eliminate the potential need for such service networks to advertise
additional information to its service users. Current access points advertise the characteristics
of the wireless access network itself. However, some embodiments of the invention allow
characteristics of the service network to be advertised. For example, a dedicated service
network may benefit from low duty cycle advertising of security information necessary for
the corresponding user terminals to have available and decode prior to use of the network.
[0012] The service network can maintain credentials of a user such that the user can be
authenticated prior to providing access of services to the user. Multiple service networks can
be associated with multiple service providers, A user may be a subscriber of just one of the
service networks, but not of the other service networks. Alternatively, a user may be a
subscriber of multiple service networks. By advertising the service networks supported by a
wireless access point, a user terminal is able to obtain information about what service
networks are available, and the user terminal can select an appropriate one of the service
networks to access.
[0013] The mechanism to efficiently advertise multiple service networks according to
some embodiments involves use of messages at multiple levels of detail to advertise the
service networks supported by the wireless access point. The messages at the multiple levels
of detail can include a first message containing a short indicator (e.g., a one-bit flag)
indicating that the wireless access point supports multiple service networks, and a second
message containing more detailed information identifying the multiple service networks that
are supported by the wireless access point. The first message having less detail (and
therefore having a smaller size) is transmitted more frequently than the second message.

which is transmitted less frequently. By transmitting the second message (which is larger in
size) less frequently, more efficient usage of the wireless bandwidth between wireless access
points and mobile stations can be achieved.
[0014] In another embodiment, instead of advertising multiple service networks al
multiple levels of detail, "enhanced capabilities" of a wireless access point can be advertised.
"Enhanced capabilities" refers to capabilities of a wireless access point other than services
provided by the wireless access point to enable wireless attachment by mobile stations and
communications between the mobile stations and a network connected to the wireless access
point. Examples of enhanced capabilities include web services, location services, emergency
services, and so forth. A first message at a first level of detail can specify that the wireless
access point supports multiple enhanced capabilities, and a second message at a second level
of detail can describe the details of the multiple enhanced capabilities.
[0015] Fig. 1 illustrates an exemplary communications network 100 that includes a
wireless access network 102 that has a collection of access points 104,106, a distribution
system 116, and aportal 118. Although just two access points 104, 106 are depicted as being
part of the wireless access network 102, it is contemplated that the wireless access network
102 can include more access points. A "wireless access point" or "access point" refers to a
device having wireless {e.g., radio) transceivers that enable wireless mobile stations to
wirclcssly connect to the device for the purpose of accessing a network resource.
[0016] Each access point 104, 106 delivers wireless access service to a respective
coverage area 108, 110. A mobile station within a particular coverage area is able to
wirelessly communicate with the corresponding access point. For example, a mobile station
112 is located in the coverage area 108 of the access point 104, while a mobile station 114 is
located in the coverage area 110 of the access point 106. A "mobile station" refers to any
user terminal that is able to wirelessly communicate with a wireless access point. Examples
of mobile stations include computers, personal digital assistants (PDAs), mobile telephones,
and so forth. Alternatively, the stations 112, 114 can be fixed rather than mobile station.
[0017] In some embodiments, the wireless access network 102 can be a Wi-Fi network
(also referred to as a wireless local area network or WLAN), which is defined by various
IEEE (Institute of Electrical and Electronics Engineers) 802.11 standards, including 802.1 la.

802.1 lb. 802.1 Ig, 802.1 la, 802.1 lu, and 802.1 lv. In accordance with some embodiments,
reference to "Wi-Fi'1 or "WLAN" or "wireless local area network" refers to any wireless
access network that employs any of the IEEE 802.11 standards, including currently existing
standards as well as future standards that evolve from the current standards. Although
reference is made to "Wi-Fi" or "WLAN" in some embodiments, it is noted that the same or
similar techniques can be applied to other wireless access technologies.
[0018] According to the IEEE 802.11 standards, an access point (such as access point
104 or 106) together with its associated stations (including mobile stations) is referred to as a
basic service set (BSS). An extended service set (ESS) is a set of one or more interconnected
BSSs. Thus, in the example of Fig. 1, the basic service sets created by access points 104 and
106 together are part of an ESS.
[0019] Fig. 1 also shows a distribution system (DS) 116, which refers to a component
(which can be the physical infrastructure and/or a virtual implementation) for connecting
multiple access points together. The wireless access network 102 is able to connect through a
portal 118 to an external network 120, which can be the Internet, a local area network, a wide
area network, or other type of network.
[0020] Service networks 122 and 124 are accessible by the wireless access network 102
over the network 120. In one embodiment, the service network 122 is referred to as SSPN #1
(subscriber service provider network #1), and service network 124 is referred to as SSPN #2
(subscriber service provider network #2). Each service network 122 and 124 includes an
authentication server 126 and 128, respectively, to store user credentials and other
subscription information for authenticating users and to indicate what services users have
subscribed to.
[0021 ] Although just two service networks arc depicted in Fi g. 1, it is noted that in
other implementations, additional service networks can be accessible by the wireless access
network 102.
[0022] Each access point 104 or 106 is configured with information about the service
networks 122 and 124, such that each access point 104 or 106 is able to advertise information
regarding the service networks that the access point is able to support. The access point is

able to advertise information regarding service networks supported by the access point by
sending messages at multiple levels of detail, where less detailed messages (messages of
smaller size) are sent more frequently, while more detailed messages (messages of larger
size) are sent less frequently.
[0023] The arrangement of network nodes depicted in Fig. 1 is provided for purposes of
example. In other implementations, other arrangements can be employed.
[0024] In accordance with some embodiments, a mobile station is able to learn
information about service networks supported by an access point in a passive manner (i.e.,
the mobile station does not have to first transmit a query to the access point to obtain
information about service networks supported by the access point). By not requiring mobile
stations to issue queries to obtain information regarding supported service networks, more
efficient utilization of the wireless bandwidth is provided. For example, in a stadium
environment where there can be tens of thousands of users, requiring each user to submit
queries to obtain information about supported service networks would result in a large
amount of traffic just for the purposes of determining service network availability and/or
characteristics.
[0025] A further enhancement provided by some embodiments is that detailed
messages that are large are sent less frequently. To accomplish this, a wireless access point
can send a first message that contains a simple indicator of whether or not the access point
supports multiple service networks. The indicator can be a single-bit flag, for example,
where a first value indicates support for multiple service networks, while a second value
indicates no support for multiple service networks. The first message can also contain time
information to indicate when the mobile stations associated with the access point can expect
to receive a second, more detailed message, which contains information regarding the
supported service networks. The second message is sent less frequently than the first
message. Each time the first message is transmitted, the time information can be iteratively
decremented until such time as the second message is actually sent, after which the time
information can be reset to its initial value.
[0026] Although reference is made to messages at two levels of detail, it is noted that in
other embodiments, messages at three or more levels of detail can be employed

[0027] Fig. 2 shows a process performed by an access point, according to an
embodiment. The access point initially determines (at 202) the service networks that are
supported by the access point. In one example, the access point can be programmed with
configuration information regarding the service networks that are supported by the access
point. Alternatively, the access point can retrieve such information from a remote source,
[0028] Next, the access point periodically sends (at 204) the first message containing a
multi-service network indicator (to indicate whether or not the access point supports multiple
service networks) and time information to indicate when mobile stations can expect to
receive the more detailed second message containing detailed information regarding
supported service networks. The time interval at which the first message is periodically sent
can be predefined.
[0029] In some implementations, the time information contained in the first message
can be in the form of a time interval value. The second message would be sent at that precise
time interval after the first message. Note that the first message can be a broadcast message,
such as part of a beacon frame. In other implementations, the time information can have
other formats.
[0030] The access point also periodically sends (at 206) the second message (also
referred to as a "full advertisement message") containing detailed information regarding
service networks (including identification information of the service networks). The full
advertisement message is sent less frequently, and the time interval at which the full
advertisement message is periodically sent can be predefined to be larger than the time
interval at which the first message is periodically sent. The full advertisement message can
also be sent as part of a beacon frame.
[0031 ] The periodically sent full advertisement messages arc sent at time points
indicated by the periodically sent first messages. In response to each first message, a mobile
station knows exactly when the mobile station needs to listen for the full advertisement
message. The mobile station can then optionally enter a sleep or power saving mode, and
then wake up just in time to receive the full advertisement message. As a result, battery life
of the mobile station can be saved, while at the same time, the mobile station can relatively
quickly and efficiently learn about available service networks in a passive manner. The full

advertisement message can contain information for multiple service networks in one
message, and since that message is sent at a low rate, the message can be quite large,
containing much detail, and in some cases can include everything the mobile station would
ever want to know about the service network. This enables the mobile station to avoid
requesting additional information later.
[0032] In some embodiments, the full advertisement message can be in the form of a
Generic Advertisement Service (GAS) query response, as defined by IEEE 802.1 lu.
[0033] Although Fig. 2 depicts just two levels of detail for messages sent by the access
point to advertise supported service networks, it is noted that alternative embodiments can
employ more than two levels of detail. In such other embodiments, a message having an
intermediate detail level (between the detail levels of the first and full advertisement
messages) can be sent at another rate that is less than the rate at which the first messages aTe
sent but greater than the rate at which the full advertisement second messages are sent.
[0034] The tasks performed in Fig. 2 by the wireless access point can be performed by
a wireless access point 300 depicted in Fig. 3. The wireless access point 300 can be one of
the access points 104 and 106 depicted in Fig. 1. The wireless access point 300 includes
software 302 that is executable on one or more central processing units (CPUs) 304 to
perform tasks of the access point 300, including the tasks discussed above. The one or more
central processing units 304 are connected to a storage 306, where the storage can contain
information relating to the service networks supported by the access point 300, for example.
[0035] The wireless access point 300 also includes network interfaces 308, including a
wireless interface and an interface to a backbone network or other construct that
interconnects multiple access points.
[0036] The above has described mechanisms and techniques to more efficiently
advertise information regarding service networks supported by an access point. In another
aspect according to some embodiments, sizes of messages (such as beacon frames, including
any of the beacon frames discussed above) can be reduced by compressing portions of such
messages. One portion of a message sent between mobile stations and access points that can
be compressed is an SSID (Service Set Identifier) field, which is used to identify a particular

virtual wireless access network. The compression of the SSID can be accomplished by
hashing the SSID to produce a hash value that is smaller than the SSID. Hashing effectively
converts an SSID string into a hash value that has a shorter length.
[0037] For example, an SSID string can be 32 bytes long. Hashing the SSID can
produce a hash value that is 2 or 4 bytes in length. Note that hash values are not unique such
that there is a possibility of two SSIDs hashing to the same hash value. This is referred to as
a hash collision, which requires a follow-up procedure to resolve the hash collision. When a
mobile station detects a hash value in a message that matches a hash value of interest to the
mobile station, the mobile station can perform a follow-up procedure to resolve whether or
not an actual match has occurred.
[0038] For example, upon detecting a matching hash value, the mobile station can send
a query (e.g., a probe request) to the access point, where the query contains the actual SSID
of interest to the mobile station. The access point can then send a response to indicate
whether or not an actual SSID match has occurred. If a match is indicated, then the original
message (e.g.. beacon frame) received by the mobile station is of interest to the mobile
station. However, if a match is not indicated, then the mobile station can discard the original
message.
[0039] In an alternative embodiment, instead of using hashes, fingerprints can be used
instead, where SSIDs are mapped to corresponding fingerprints. A benefit of fingerprints is
that they are unique-however, the uniqueness comes at the expense of the fingerprints being
longer in length than hash values.
[0040] Instructions of software (e.g., software 302 in Fig. 3) for performing various
tasks above can be loaded for execution on a processor (e.g., one or more CPUs 304 in Fig.
3). The processor includes microprocessors, microcontrollers, processor modules or
subsystems (including one or more microprocessors OT microcontrollers), or other control or
computing devices. A "processor" can refer to a single component or to plural components.
[0041] Data and instructions (of the software) are stored in respective storage devices,
which arc implemented as one or more computer-readable or computer-usable storage media.
The storage media include different forms of memory including semiconductor memory

devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable
and programmable read-only memories (EPROMs), electrically erasable and programmable
read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy
and removable disks; other magnetic media including tape; and optical media such as
compact disks (CDs) or digital video disks (DVDs).
[0042] In the foregoing description, numerous details are set forth to provide an
understanding of the present invention. However, it will be understood by those skilled in the
art that the present invention may be practiced without these details. While the invention has
been disclosed with respect to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is intended that the appended
claims cover such modifications and variations as fall within the true spirit and scope of the
invention.

What is claimed is:
1. A method to advertise capabilities of a wireless access point, comprising:
communicating, from the wireless access point to a mobile station, messages at plural
levels of detail to advertise that the wireless access point supports a plurality of service
networks,
wherein the messages at the plural levels of detail include a first message indicating
that the wireless access point supports multiple service networks, and a second message
containing information identifying the plurality of service networks.
2. The method of claim 1, further comprising communicating, between the wireless
access point and the mobile station, time information indicating when the second message
will be communicated.
3. The method of claim 2, wherein communicating the time information comprises
communicating the time information in the first message.
4. The method of claim 1, wherein the first message is communicated more frequently
than the second message, and wherein the first message is smaller in size than the second
message.
5. The method of claim 1, wherein the messages at the plural levels of detail further
include a third message at a detail level between detail levels of the first and second
messages.
6. The method of claim 5, wherein the third message is sent more frequently than the
second message but less frequently than the first message.
7. The method of claim I, wherein communicating the messages comprises
communicating a hashed value of a service set identifier in one of the messages.
8. The method of claim 1. wherein communicating the messages comprises the wireless
access point sending the messages to the mobile station.

9. The method of claim 1. wherein communicating the messages comprises the mobile
station receiving the messages from the wireless access point.
10. The method of claim 1, wherein communicating the second message comprises
communicating a Generic Advertisement Service (GAS) query response.

11. The method of claim 1, wherein communicating the messages comprises
communicating the messages from a Wi-Fi access point to the mobile station.
12. The method of claim 1, wherein the mobile station is able to learn about information
of the plurality of service networks in a passive manner.
13. A wireless access point, comprising:
a wireless interface to communicate wirelessly with a mobile station;
a processor to:
determine service networks supported by the wireless access point;
send, to the mobile station, messages at plural detail levels to advertise that the
wireless access point supports the service networks,
wherein the messages at the plural detail levels include a first message
indicating that the wireless access point supports multiple service networks, and a second
message containing information identifying the service networks.
14. The wireless access point of claim 13, wherein the processor is configured to send the
messages at the plural detail levels without requiring any query from the mobile station such
that the mobile station is able to learn about the service networks in a passive manner.
15. The wireless access point of claim 14, wherein the first message contains time
information indicating when the second message will be sent.
16. The wireless access point of claim 15, wherein the first message is smaller in size than
the second message.

17. The wireless access point of claim 16, wherein the first message is seat more
frequently than the second message.
18. An article comprising at least one computer-readable storage medium containing
instructions that when executed cause a mobile station to:
receive, from a wireless access point, messages at plural detail levels to advertise that
the wireless access point supports a plurality of enhanced capabilities,
wherein the messages at the plural detail levels include a first message indicating that
the wireless access point supports multiple enhanced capabilities, and a second message
containing detailed information about the plurality of enhanced capabilities
19. The article of claim 18, wherein the instructions when executed cause the mobile
station to receive, from the wireless access point, time information indicating when the
second message will be communicated
20. The article of claim 18, wherein the first message is smaller than the second message,
and the first message is sent more frequently than the second message.

(57) Abstract To advertise capabilities of a wireless
access point, the wireless access point communicates,
to a mobile station, messages at plural
levels of detail to advertise that the wireless access
point supports a plurality of service networks.
The messages at the plural levels of detail
include a first message indicating that the wireless
access point supports multiple service networks,
and a second message containing information
identifying the plurality of service networks.