(19)
(11)EP 1 493 249 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
05.01.2011 Bulletin 2011/01

(21)Application number: 03721539.9

(22)Date of filing:  04.04.2003
(51)Int. Cl.: 
H04L 12/28  (2006.01)
(86)International application number:
PCT/US2003/010476
(87)International publication number:
WO 2003/088585 (23.10.2003 Gazette  2003/43)

(54)

METHOD FOR ACCESS POINT MANAGEMENT OF MESSAGES FOR POWERED OFF STATIONS IN WIRELESS LAN

VERFAHREN FÜR ZUGANGSPUNKTSVERWALTUNG VON NACHRICHTEN FÜR AUSGESCHALTETE STATIONEN IN EINEM DRAHTLOSEN LOKALEN NETZWERK

PROCEDE DE GESTION D'UN POINT D'ACCES DES MESSAGES POUR DES STATIONS HORS TENSION DANS UN RESEAU LOCAL D'ENTREPRISE SANS FILS


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR

(30)Priority: 11.04.2002 US 121952

(43)Date of publication of application:
05.01.2005 Bulletin 2005/01

(73)Proprietor: Intel Corporation
Santa Clara, CA 95052 (US)

(72)Inventors:
  • TONSE, Sudhir
    Bangalore, KK 560070 (IN)
  • KP, Sameer
    Nagar Post Bangalore, KK 560032 (IN)
  • MISHRA, Meeta
    New Thippasandra, Bangalore, KK 560075 (IN)
  • DEGWEKAR, Anila
    Airport Road, Bangalore, KK 560017 (IN)
  • RAJAGOPAL, Sridhar
    Bangalore, KK 560080 (IN)

(74)Representative: Dunlop, Hugh Christopher et al
R.G.C. Jenkins & Co. 26 Caxton Street
London SW1H 0RJ
London SW1H 0RJ (GB)


(56)References cited: : 
  
  • DIEPSTRATEN, ENNIS: "Distributed Access WMAC Synchronization and Power management mechanisms" IEEE, [Online] July 1993 (1993-07), XP002248693 Retrieved from the Internet: <URL:http://grouper.ieee.org/groups/802/11 /Documents/DocumentArchives/1993_docs/> [retrieved on 2003-07-23]
  • "IEEE standard Part 11: wireless LAN medium access control (MAC) and physical layer (PHY) specification. (ISO/IEC 8802-11, ANSI/IEEE Std 802.11-1999) Chapter 11: MAC sublayer management entity" ISO/IEC 8802-11 ANSI/IEEE STD 802.11, XX, XX, 20 August 1999 (1999-08-20), pages 123-137, XP002207975
  • DIEPSTRATEN: "the provisions required for handoff." IEEE, [Online] January 1994 (1994-01), XP002248694 Retrieved from the Internet: <URL:http://grouper.ieee.org/groups/802/11 /Documents/DocumentArchives/1993_docs/> [retrieved on 2003-07-23]
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

BACKGROUND



[0001] Wireless Local Area Networks (LAN) have become a popular alternative to wired LANs, especially at locations where wiring is difficult or costly. For example, a warehouse or a hospital that was not built to include a wiring infrastructure for the LAN may have great difficulties to accommodate a wired network. The cost for adding the wiring infrastructure into such a building may be prohibitively higher than deploying a wireless LAN.

[0002] Stations or devices in a wireless LAN may communicate with each other directly over wireless channels, or indirectly through a wireless Access Point (AP). A wireless AP may act as a hub to provide connectivity for the devices associated with the AP, or may serve as a bridge to connect a wireless LAN to a variety of wired networks, e.g., Ethernet and Token Ring networks. A number of wireless APs may be interconnected to provide an extensive coverage area for a wireless LAN.

[0003] There are several approaches to implementing an AP. An AP may be implemented as an embedded hardware product, or as a software product that may be run on a general-purpose computer. The APs that are implemented in software may be called soft APs.

[0004] One widely-accepted industry standard for wireless LANs is the IEEE 802.11 standard published in 1997. The IEEE 802.11 standard specifies that a device in a wireless LAN enter a power-saving state after being inactive for a pre-determined period of time. The device may periodically wake up from the power-saving state to receive beacon signals from the AP with which the device is associated. The beacon signals may indicate whether there are messages waiting for the device at the AP.
US 6,091,947 discloses a method and apparatus for accepting and conveying a voice mail message to a mobile unit in a wireless telephone system comprising user interaction wherein the user may refuse to receive incoming calls or voice mails, whereby the user is then re-presented with the same request at a certain time delay thereafter, thus requiring a further user interaction to refuse, for example, the same message.
"Distributed Access WMAC Synchronization and Power Management Mechanisms" IEEE, [Online] July 1993 (1993-08), XP0022486983 by Wim Diepstraten and Greg Ennis describes a proposed Medium Access Control protocol for a wireless local area network (the Wireless MAC, or WMAC). The protocol is based on a distributed access mechanism called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The protocol allows stations to operate with receivers powered off for much of the time while still ensuring that frames will be received by a station informing an access point if they wish to enter a power-conserving mode. If this is the case, the access point will buffer frames and will only transmit them at designated times.

BRIEF DESCRIPTION OF THE DRAWINGS



[0005] FIG. 1 illustrates an embodiment of a system including an AP according to the present disclosure; and

[0006] FIG. 2 illustrates a flow diagram of a message-managing process carried out by the AP.

DETAILED DESCRIPTION



[0007] FIG. 1 shows an embodiment of a wireless LAN 110 including wireless devices 11, 12, and 13, that may be connected to a computer 16 on which a wireless AP 19 is installed. In this embodiment, the AP 19 may be implemented as a soft AP that resides on a computer-readable medium 17 accessible by the computer 16. Alternatively, the AP 19 may be implemented as an embedded hardware device. The devices 11, 12, and 13 may be computers or mobile stations with wireless LAN cards, and may communicate with each other through the AP 19 over wireless channels.

[0008] The wireless network 110 may be connected to a wired network 140 through the AP 19. The AP 19, in this embodiment, serves as a bridge between the two networks 110 and 140, performing appropriate address and format translations. Although only one device 14 is shown in the wired network 140, a plurality of devices may be included in the wired network 140, connecting to a hub 15. Through the AP 19 and the hub 15, the devices 11, 12, and 13 may communicate with any of the devices in the wired network 140.

[0009] When the AP 19 receives a message destined for a device in the wireless LAN 110, e.g., the device 11, the AP 19 may send a beacon signal notifying the device 11 of the incoming message. If the device 11 is accessible and ready to receive the message, the AP 19 forwards the message to the device 11. Otherwise, the AP 19 may hold the message until the device 11 is ready to receive the message.

[0010] If the device 11 temporarily leaves the wireless network 110, the AP 19 may hold the messages addressed to the device 11, thereby maintaining a virtual connectivity for the device 11. This may happen, for example, when the device 11 goes into an inactive mode, e.g., a power down mode or a hibernate mode, or when the device 11 roams beyond the communication range of the AP 19. Before the device 11 leaves the network 110, the device 11 may notify the AP 19 of the inaccessibility. Once the AP 19 receives this notification, the AP holds all the incoming messages addressed to the device 11 until the device 11 becomes accessible and ready to receive messages again, although the scope of the invention is not limited in this respect.

[0011] If the device 11 leaves the wireless network 110 due to a sudden loss of connection to the AP 19, the device 11 may not be able to notify the AP 19 prior to losing the connection. In this scenario, when the AP receives a message addressed to the device 11, the AP 19 may attempt to deliver the message by querying whether the device 11 is ready to receive messages. The AP 19 waits for a pre-determined period of time but no response from the device 11 is detected. The AP 19 may then determine that the device 11 has become inaccessible and start holding messages for the device 11.

[0012] When the device 11 is inaccessible, the incoming messages bound for the device may be held in storage media 18, e.g., memory or hard disks, which is accessible by the AP 19. The storage media 18 may reside locally in computer 16, as shown in FIG. 1, or reside in a remote location. The size of the storage media 18 allocated to store the messages can be determined based on the following factors including, but not limited to, the number of devices connected to the wireless LAN 110, and the duration of time for which the AP 19 holds the messages. To avoid these messages from overflowing the allocated space, the AP 19 may discard some of the messages, such as the messages that have stayed in the storage media 18 longer than an age limit, to make room for the more recent messages.

[0013] After the device 11 returns to the wireless network 110, the device 11 sends an "I am back" message to the AP 19 to indicate the accessibility. The AP 19 then sends a beacon signal to determine whether the device 11 is ready to receive messages. If the device 11 is ready, the AP 19 forwards all the messages addressed to the device 11 that are held in the storage media 18 to the device 11. Otherwise, the AP 19 continues to hold the messages until the device 11 is ready or the age limit for holding the messages is exceeded.

[0014] If the AP 19 is implemented as a soft AP, the capacity of the AP 19 for holding messages may be increased without significant increase in cost. For example, the capacity can be increased by adding more hard disks to the computer 16.

[0015] In contrast to the standard specified by the IEEE 802.11, the device 11 is not required to wake up periodically to receive beacon signals from the AP 19. Rather, the device 11 only sends a signal to the AP 19 before it goes off-line, and sends another signal to the AP 19 after the device become accessible again. This allows the device 11 to save a significant amount of power compared to a device implementing the IEEE 802.11 standard.

[0016] FIG. 2 illustrates a message-managing process 20 carried out by the AP 19. The process 200 determines when to hold a message for an associated device and when to forward the message to the device. The process 200 begins at a start state 201. Proceeding to state 205, the AP 19 receives a message. The message includes an address field, which has a destination address indicating to which device the message should be forwarded. Proceeding to state 210, the AP 19 determines which device to send the message based on the destination address. Here, assume the message is addressed to the device 11.

[0017] Proceeding to state 215, the AP 19 determines if the device 11 is accessible. The AP 19 keeps status information for the associated devices in a memory location. Once the AP 19 detects, or is notified of, a device's inaccessible status, the AP 19 stores the status information in the memory location until the device 11 notifies the AP 19 of a change of status. If the device 11 is accessible, the process 200 proceeds along the YES branch to state 220 to further determine if the device 11 is ready to receive messages. If the device 11 is not accessible, the process 200 proceeds along the NO branch to state 240 to buffer the message to the storage media 18.

[0018] In state 220, if the device 11 is ready to receive messages, the process 200 proceeds along the YES branch to state 230 to stream the message to the device 11. If the device 11 is not ready to receive any messages, the process 200 proceeds along the NO branch to state 240 to buffer the message to the storage media 18.

[0019] After the AP 19 buffers the message to the storage media 18, the process 200 proceeds to state 250. In state 250, the AP 19 determines if any message in the storage media 18 has passed the age limit for holding the messages. If the AP 19 finds a message that has passed the age limit, the process 200 proceeds along the YES branch to state 260. The message is discarded from the storage media 18, and the process 200 returns to state 210. If the AP 19 does not find a message that has passed the age limit, the process 200 proceeds along the NO branch back to state 210. The AP 19 then continues to process the next received message.

[0020] The process 200 may be used for devices that typically do not roam between different APs, but remain associated with a single AP. By carrying out the process 200, the AP 19 enables a virtual connectivity for devices associated with the AP 19 by forwarding and holding messages for the devices at appropriate times. Thus, the devices can be turned off for a prolonged time period without losing connectivity to other devices in the network. This allows power-limited devices, e.g., cellular phones or Personal Digital Assistants (PDAs), to preserve battery power.

[0021] Devices that are less limited by battery power, e.g., in-home devices, can also benefit from the present disclosure. For example, a device may not wish to be interrupted while engaging in a computing task. During the time when the device is busy, the AP 19 may treat the device as inaccessible. The AP 19 may hold the messages addressed to the device until the device completes the task. The AP 19 may then forward the messages in a batch to the device.

[0022] Other embodiments are within the scope of the following claims.


Claims

1. A method performed at an access point comprising:

receiving a notification from a device (11) on a wireless network, the notification indicating that the device has become inaccessible;

after receipt of the notification, receiving (205) a message addressed to the device (11);

storing (240) the message in storage media (18);

after receipt of the message, receiving a signal from the device (11) indicating that the device has become accessible;

in response to receipt of the signal indicating that the device has become accessible, sending a beacon signal to the device (11) to determine whether the device is ready to receive messages; and

forwarding (230) the message to the device after the device has become ready to receive messages.


 
2. The method of claim 1 further comprising: discarding (260) the message if the message has been stored in the storage media (18) longer than an age limit.
 
3. The method of claim 1 further comprising receiving, storing, and forwarding multiple messages.
 
4. A system comprising:

storage media (18);

an access point (19) that is coupled to a plurality of devices (11, 12, 13), the access point being adapted to:

receive a notification from one of the devices (11), the notification indicating that the device is becoming inaccessible;

after receipt of the notification, receive a message addressed to the one of the devices (11);

buffer the message to the storage media;

after receipt of the message, receive a signal from said device indicating that the device has become accessible;

in response to receipt of the signal indicating that the device has become accessible, send a beacon signal to the device to determine whether the device is ready to receive messages; and

forward the message to the device if the device (11) has become ready to receive messages; and

a wireless network (110) to connect the access point to the plurality of devices.


 
5. The system as in claim 4, wherein the access point (19) is a software application executable by a computer.
 
6. The system as in claim 4 further comprising a memory location accessible by the access point (19), the memory location keeping a status of accessibility for each of the plurality of devices (11, 12, 13).
 
7. The system as in claim 4, wherein the size of the storage media (18) allocated to the access point is adjustable based on the number of devices (11, 12, 13) connected to the access point.
 
8. The system as in claim 4, wherein the size of the storage media (18) allocated to the access point (19) is adjustable based on a time period for which the access point holds the messages.
 
9. The system as in claim 8, wherein the access point (19) discards a buffered message if the buffered message has been stored in the storage media (18) longer than the time period.
 
10. A computer program product residing on a computer-readable medium comprising instructions for causing the computer to perform the method of any one of claims 1 to 3 when executed.
 


Ansprüche

1. Verfahren, das an einem Zugangspunkt ausgeführt wird, Folgendes aufweisend:

Empfangen einer Benachriclatigung von einer Vorrichtung (11) auf einem drahtlosen Netzwerk, wobei die Benachrichtigung anzeigt, dass die Vorrichtung unzugänglich geworden ist;

nach dem Empfangen der Benachrichtigung, Empfangen (205) einer Nachricht, die an die Vorrichtung (11) gerichtet ist;

Speichern (240) der Nachricht in dem Speichermedium (18) ;

nach dem Empfang der Nachricht, Empfangen eines Signals von der Vorrichtung (11), das anzeigt, dass die Vorrichtung zugänglich geworden ist;

als Reaktion auf den Empfang des Signals zum Anzeigen, dass die Vorrichtung zugänglich geworden ist, Senden eines Bakensignals zu der Vorrichtung (11), um zu bestimmen, ob die Vorrichtung zum Empfangen von Nachrichten bereit ist; und

Weiterleiten (230) der Nachricht an die Vorrichtung, nachdem die Vorrichtung zum Empfangen von Nachrichten bereit geworden ist.


 
2. Verfahren nach Anspruch 1, das ferner Folgendes aufweist: Entfernen (260) der Nachricht, wenn die Nachricht in dem Speichermedium (18) länger als ein Alterslimit gespeichert wurde.
 
3. Verfahren nach Anspruch 1, das ferner das Empfangen, Speichern und Weiterleiten mehrerer Nachrichten umfasst.
 
4. System mit Folgendem:

einem Speichermedium (18) ;

einem Zugangspunkt (19), der mit mehreren Vorrichtungen (11, 12, 13) gekoppelt ist, wobei der Zugangspunkt:

eine Benachrichtigung von einer der Vorrichtungen (11) empfangen kann, wobei die Benachrichtigung anzeigt,

dass die Vorrichtung unzugänglich wird;

nach dem Empfangen der Benachrichtigung, eine Nachricht empfangen kann, die an eine der Vorrichtungen (11) gerichtet ist;

die Nachricht zu dem Speichermedium pufferspeichern kann;

nach dem Empfang der Nachricht ein Signal von der Vorrichtung empfangen kann, das anzeigt, dass die Vorrichtung zugänglich geworden ist;

als Reaktion auf den Empfang des Signals, das anzeigt, dass die Vorrichtung zugänglich geworden ist, ein Bakensignal an die Vorrichtung senden kann, um zu bestimmen, ob die Vorrichtung zum Empfangen von Nachrichten bereit ist; und

die Nachricht zu der Vorrichtung weiterleiten kann, wenn die Vorrichtung (11) zum Empfangen von Nachrichten bereit geworden ist; und

einem drahtlosen Netzwerk (110), um den Zugangspunkt mit der Vielzahl von Vorrichtungen zu verbinden.


 
5. System nach Anspruch 4, wobei der Zugangspunkt (19) eine durch einen Computer ausführbare Softwareanwendung ist.
 
6. System nach Anspruch 4, das ferner einen Speicherplatz aufweist, der für den Zugangspunkt (19) zugänglich ist, wobei der Speicherplatz einen Status der Zugänglichkeit für jede der Vielzahl von Vorrichtungen (11, 12, 13) führt.
 
7. System nach Anspruch 4, wobei die Größe des Speichermediums (18), die dem Zugangspunkt zugewiesen ist, auf der Grundlage der Anzahl von Vorrichtungen (11, 12, 13), die an den Zugangspunkt angeschlossen sind, einstellbar ist.
 
8. System nach Anspruch 4, wobei die Größe des Speichermediums (18), die dem Zugangspunkt (19) zugewiesen wird, auf der Grundlage einer Zeitspanne, während der der Zugangspunkt die Nachrichten behält, einstellbar ist.
 
9. System nach Anspruch 8, wobei der Zugangspunkt (19) eine gepufferte Nachricht entfernt, wenn die gepufferte Nachricht in dem Speichermedium (18) länger als die Zeitspanne gespeichert wurde.
 
10. Computerprogrammprodukt auf einem computerlesbaren Träger, das Anweisungen enthält, um den Computer zu veranlassen, das Verfahren nach einem der Ansprüche 1 bis 3 umzusetzen, wenn es ausgeführt wird.
 


Revendications

1. Procédé réalisé à un point d'accès comprenant :

la réception d'une notification depuis un dispositif (11) sur un réseau sans fil, la notification indiquant que le dispositif est devenu inaccessible ;

après réception de la notification, la réception (205) d'un message adressé au dispositif (11) ;

le stockage (240) du message dans un support de stockage (18) ;

après réception du message, la réception d'un signal du dispositif (11) indiquant que le dispositif est devenu accessible ;

en réponse à la réception du signal indiquant que le dispositif est devenu accessible, l'envoi d'un signal de balise au dispositif (11) pour déterminer si le dispositif est prêt à recevoir des messages ; et

l'envoi (230) du message au dispositif après que le dispositif est devenu prêt à recevoir des messages.


 
2. Procédé selon la revendication 1 comprenant en outre :

le rejet (260) du message si le message a été stocké dans le support de stockage (18) plus longtemps qu'une limite d'âge.


 
3. Procédé selon la revendication 1 comprenant en outre la réception, le stockage, et l'envoi de multiples messages.
 
4. Système comprenant :

un support de stockage (18) ;

un point d'accès (19) qui est couplé à une pluralité de dispositifs (11, 12, 13), le point d'accès étant adapté pour :

recevoir une notification d'un des dispositifs (11), la notification indiquant que le dispositif est devenu inaccessible ;

après réception de la notification, recevoir un message adressé à l'un des dispositifs (11) ;

mettre en mémoire tampon le message sur le support de stockage ;

après réception du message, recevoir un signal dudit dispositif indiquant que le dispositif est devenu accessible ;

en réponse à la réception du signal indiquant que le dispositif est devenu accessible, envoyer un signal de balise au dispositif pour déterminer si le dispositif est prêt à recevoir des messages ; et

envoyer le message au dispositif si le dispositif (11) est devenu prêt à recevoir des messages ; et

un réseau sans fil (110) pour raccorder le point d'accès à la pluralité de dispositifs.


 
5. Système selon la revendication 4, dans lequel le point d'accès (19) est une application logicielle exécutable par un ordinateur.
 
6. Système selon la revendication 4, comprenant en outre un emplacement de mémoire accessible par le point d'accès (19), l'emplacement de mémoire maintenant un état d'accessibilité pour chacun de la pluralité de dispositifs (11, 12, 13).
 
7. Système selon la revendication 4, dans lequel la taille du support de stockage (18) alloué au point d'accès est ajustable sur la base du nombre de dispositifs (11, 12, 13) raccordés au point d'accès.
 
8. Système selon la revendication 4, dans lequel la taille du support de stockage (18) alloué au point d'accès (19) est ajustable sur la base d'une période de temps pour laquelle le point d'accès maintient les messages.
 
9. Système selon la revendication 8, dans lequel le point d'accès (19) rejette un message mis en tampon si le message mis en tampon a été stocké dans le support de stockage (18) plus longtemps que la période de temps.
 
10. Produit de programme informatique résidant sur un support lisible par ordinateur comprenant des instructions pour conduire l'ordinateur à réaliser le procédé d'une quelconque des revendications 1 à 3 lorsqu'elles sont exécutées.
 




Drawing









REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description