Abstract:
The present invention relates to a method, device, instruction set, and signal for communicating the availability of additional information in access points relevant for determining in a mobile station which access point to connect to. An information tag is inserted into a beacon signal alerting of the additional information available; mobile stations not implemented with the present invention may operate as if the information tag was not present and thus ensuring compatibility between systems.

Description:
TECHNICAL FIELD 
     The present invention relates to wireless signalling and in particular to a method of extending information exchange in wireless communication. 
     BACKGROUND OF THE INVENTION 
     Currently in Wireless LAN (WLAN) setups mobile stations select the access point based on radio link parameters and the network identity broadcasted in special signalling messages, so called beacons. This information is, however, in some cases inadequate to base the selection on of which access point to connect to. The user of the mobile station may have other preferences, such as price, while the applications need to know the available QoS (Quality of Service) etc. 
     WLAN access points broadcast beacons on a regular basis, normally every 100 milliseconds. Extending the beacons with extra information increases their size and thus wastes the available bandwidth on the channel. Including all desired information into the beacons would therefore not be desirable. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method, device, and signal for interchanging information between a mobile station and an access point. 
     Wireless LAN signalling can be used to automatically obtain network characteristic parameters prior to when the node establishes a connection to the network. Network characteristic parameters in this context refer to information such as price, network utilization and network access provider information that may affect the user&#39;s selection of a preferable network. 
     The present invention may in a first aspect be realized as a method of communicating information to a mobile station in a wireless network, comprising the steps of:
         broadcasting a signal with an information tag alerting mobile stations that additional information is available from an access point to listening mobile stations within communication range;   receiving the beacon at a mobile station arranged to interpret the information tag;   sending an information request from the mobile station to the access point; and   sending the additional information from the access point to the mobile station.       

     The additional information may be at least one of access point ownership, network load status, cryptographic network identities, roaming related information, available services, routing information, geographical location information, commercial information and any other relevant information. 
     The additional information may be cached in the access point or may be collected from network connected to the access point. 
     The signal may be a beacon message prepared in the access point. 
     Another aspect of the present invention, an access point in a wireless network is provided, comprising
         a wireless communication interface for communicating with mobile stations;   a communication interface for communicating with a network;
 
wherein the access point is arranged to prepare a beacon with an information tag alerting the mobile stations that additional information is available.
       

     The additional information may be at least one of access point ownership, network load status, cryptographic network identities, roaming related information, available services, routing information, geographical location information, and commercial information. 
     Yet another aspect of the present invention, a mobile station in a wireless network is provided, comprising a wireless-communication interface for communicating with at least one access point, wherein the mobile station is arranged to interpret an information tag present in a beacon signal sent from the access point; the information tag alerting of additional information available in the access point, arranged to send a request for the additional information and further arranged to decide which access point to connect to based on the additional information. 
     Still another aspect of the present invention, a beacon signal in a wireless network is provided, comprising a type-length-value (TLV) tagged parameter list comprising at least information about transmitter identity and an information tag alerting of additional information available at the transmitter, wherein the flag comprise two bytes of information; a tag number and a tag length. 
     The present invention may also be realized as an instruction set in a mobile communication device for deciding a gateway to connect to, comprising;
         an instruction set for receiving a beacon including an information tag alerting of additional information available in a gateway;   an instruction set for sending a request for the additional information to the gateway;   an instruction set for receiving the additional information;   an instructions set for using the additional information in the decision of which gateway to connect to.       

     DEFINITIONS 
     RA—Router advertisement 
     WLAN—Wireless Local Area Network 
     QoS—Quality of Service 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be described in a non-limiting way and in more detail with reference to exemplary embodiments illustrated in the enclosed drawings, in which: 
         FIG. 1  is a schematic illustration of a network according to the present invention; 
         FIG. 2  is a schematic illustration of communication messages in the network from  FIG. 1 ; 
         FIG. 3  is a block diagram of a device according to the present invention; and 
         FIG. 4  is a block diagram of a method according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a network topology wherein the present invention may find application. A mobile station  1  desires to connect to a network  4  or  5  via one connection point  2  or  3  using a wireless interface  6  or  7 . In order to establish the best connection, the mobile station  1  may use a number of different parameters in a decision process for deciding which connection to use. Therefore it is of interest to obtain adequate information about the connection points, for instance information relating to the decision about which connection point to use. 
     Connection points may be for instance an access point in a wireless local area network (WLAN), a master in Bluetooth network, a base station in a mobile phone network, or a gateway in other wireless based communication networks. Below, an example of the present invention in a WLAN network will be given. 
     In the solution according to the present invention, a beacon signal is first extended with a flag which indicates that the access point  2  or  3  is capable of delivering extra information before standard WLAN (Wireless Local Area Network) attachment frames are interchanged. If the mobile station supports using this extra information, it may send a special information request frame to the access point. The access point can then send the requested extra information in one or more special information reply frames. These information reply frames may contain any information that can help the mobile station to select the access point. The actual attachment process with the access point follows the normal WLAN procedure. 
     The access point constructs the beacon according to standard format; however, it also inserts a new TLV-encoded (Type Length Value) tagged parameter into a tagged parameters list part of the beacon signal. This tagged parameter is, for example 2 bytes long, comprising a tag number (1 byte long) and a tag length (1 byte long). 
     Referring to  FIG. 2 , when the mobile station  1  receives a beacon, it examines whether it contains this tagged parameter. If the mobile station  1  doesn&#39;t recognize the new tagged parameter or the received beacon doesn&#39;t contain it, the WLAN access selection and attachment process continues according to standard procedures, for instance according to standard specifications according to IEEE 802.11 family protocol (i.e. all IEEE 802.11 protocol members, e.g. 802.11a, b, g, n and so on). Other standard protocols may be IEEE 802.15 and IEEE 802.16 families. 
     If the tagged parameter is detected, the mobile station  1  can send an information request frame  10  or  11  to the access point  2  or  3 . Upon receiving the information request frame the access point  2  or  3  can reply with the information reply frame  20  or  22 . It should be noted that this frame is sent only to the requesting mobile station  1  (i.e. unicasted) unlike the beacon, which is sent to all mobile stations on the channel (i.e. broadcasted) within the range of the access point. 
     The information sent in the information reply frames  20  or  22  may be collected from any number of information sources. This information may optionally be cached by the access point until it is expired. 
     An example, illustrated in  FIG. 2 , of such an information source is a IPv6 (Internet Protocol version 6) neighbour discovery message, namely Router Advertisement messages (RA)  31  or  41 , which are sent by routers  30  or  40  connected to the same network  4  or  5  as the access point  2  or  3 . The access point may cache the contents of these RA messages  31  or  41  so that it can reply immediately. The RA message contains e.g. the IPv6 network prefixes, but it may also contain additional information (such as price), as RA options. New RA options can easily be defined without affecting the interoperability of the existing IPv6 implementations. 
     It should be noted, however, that the invention is not IPv6-specific. Information sent in the information reply messages may contain any type of information, such as access point ownership, network load status, cryptographic network identities, roaming related information, available services, routing information, geographical location information, and commercial information. Access point ownership may be of importance for billing purposes, the user may want to connect to a “home” based access point as a first choice in order to receive as low costs as possible for the connection; with “home” based is meant either the users own access point located at home or in an office part of a company or institution to which the user has relation to, or it may mean a commercial network operator to which the user has business relation to, such as for instance a hot spot network of access points installed at various places to which the user may roam to due belonging to the operator owning the hot spot network. Network load status may be important in order to receive as reliable and high quality connection as possible, which may be important for a VoIP (Voice over Internet Protocol) connection. The user may be interested in specific available services within a network and may desire to primarily connect to networks with these specific services available. Commercial information may for instance be advertisements for available shops or business operations within a certain area. 
     The invention makes it possible to acquire network characteristic information as part of the existing process which takes place automatically when a WLAN mobile station is discovering the access points. The solution can be implemented in a way that it will be compatible with legacy nodes and rest of the network. A legacy node is a node which does not implement the teachings of the present invention. 
     In addition, the information can be obtained without the need to apply network settings of the network being connected to. In this way the user doesn&#39;t have to go through possible authentication and configuration processes in order to obtain the information that may affect the way the user uses the network. 
       FIG. 3  illustrates a mobile station  300  according to the present invention, comprising a computational unit  301 , storage unit  302 , and communication unit  305 . It may also comprise further functionality in the form of further storage units  303  and user interface units  304 . However, the list of functionality and units is not complete since the invention may be utilized in a number of different devices communicating according to the present invention. This may be appreciated by the person skilled in the art. Other forms of devices where the present invention may find applicability are: in mobile phones, in stand alone measurement devices, personal digital assistants (PDA), and MP3 players or similar music or video storage units adapted for communicating with a network. The access point has a similar structure with a processing unit controlling the essential features of the access point and in connection with other functional units in the access point, e.g.; storage unit(s), at least one communication unit for communicating with mobile stations  1 , and at least one communication unit for communicating with an external network (e.g. Internet)  4 ,  5 . 
     The computational unit may be any type of suitable computational unit, including, but not limited to, a microprocessor, an FPGA (field programmable gate array), an ASIC (application specific integrated circuit) or similar devices. The storage unit may be any volatile or non-volatile memory type, e.g. RAM (random access memory), ROM (read only memory), hard disk, flash disks and so on as understood by the person skilled in the art. 
     Communication from the access point to the external network  4 ,  5  may be of either wired or wireless type, e.g. Ethernet, ATM (Asynchronous Transfer Mode), LMDS (Local Multipoint Distribution System), DSL (Digital Subscription Line), PTSN (Public Switched Telephone Network), WLAN, GPRS (General Packet Radio System), UMTS (Universal Mobile Telephony System), or backbone systems for mobile telephony systems. 
     The present invention may be realized as instruction sets in a software code run in the computational unit  301  and for instance stored in the storage unit  302 . 
     Turning now to  FIG. 4 , a method of interchanging communication will be discussed. An access point transmits a beacon including a flag indicating that additional information is available ( 401 ). A mobile station receives this beacon and interprets the flag correctly ( 402 ). The mobile station then sends a request to the access point, asking the access point to transmit the additional information ( 403 ). The access point receiving the request sends a response to the mobile station with the requested information ( 404 ). Steps  401  to  404  may not be repeated for all access points within the communication range of the mobile station. When a suitable access point is found, the station can then proceed to step ( 406 ) without repeating the steps for remaining access points. This is due to the fact that there are two options, whether to collect all information before doing the selection (as described in the current application) or to do selection after each response, e.g. the station may search for an access point with certain characteristics. 
     If all access points are searched and when all access points have sent their respective information, the mobile station decides on which access point to connect to ( 405 ) and then initiates normal-connection procedures ( 406 ). 
     It should be noted that the word “comprising” does not exclude the presence of other elements or steps than those listed and the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the invention may be implemented at least in part by means of both hardware and software, and that several “means”, “units” or “devices” may be represented by the same item of hardware. 
     The above mentioned and described embodiments are only given as examples and should not be limiting to the present invention. Other solutions, uses, objectives, and functions within the scope of the invention as claimed in the below described patent claims should be apparent for the person skilled in the art.