HK1097684A

HK1097684A - Method and system for switching a radio access technology between wireless communicaiton systems with a multi-mode wireless transmit/receive unit

Info

Publication number: HK1097684A
Application number: HK07105198.2A
Authority: HK
Inventors: 卡梅尔．M．沙恩; 史蒂芬.E.泰利; 布莱恩．格列格里．基尔南
Original assignee: 美商内数位科技公司
Priority date: 2004-03-12
Filing date: 2005-03-11
Publication date: 2007-06-29

Description

Method and system for switching radio access technology between wireless communication systems by using multi-mode wireless transmit/receive unit

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to a method and system for switching Radio Access Technologies (RATs) between wireless communication systems connected to each other when the different RATs are implemented by a multi-mode wireless transmit/receive unit (WTRU).

Background

Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Network (WLAN) technologies are widely used in current wireless communication systems. Since the coverage areas of the umts and wlan are usually overlapped, the interworking between the umts and wlan is developed. An inter-working wireless local area network (I-WLAN) is a WLAN with a core network for the UMTS so that services provided by the UMTS can be relayed through the inter-working WLAN.

Currently, the network selection for interconnecting wlans requires wtrus to scan for available wlan systems using their Service Set Identifiers (SSIDs). The scanning of the ssids may be done passively or actively. During passive scanning, the wtru observes information broadcast from each wlan and determines its availability based on signal strength. In active scanning, the wtru sends a probe request including a specific wlan ssid and waits for an acknowledgement of availability from the wlan.

However, these techniques do not provide any indication of a wireless local area network (ssid) that can access umts based services. Several solutions are designed to include the dissemination of home Public Land Mobile Network (PLMN) identification over a dissemination channel on a wlan. However, this technique is easily emulated because the wlan ssid is not unique (disruptive wlan operators can propagate the same ssid and plmn ids).

Therefore, the selection of a umts based inter-wlan for connecting to umts based services can be problematic due to the large number of wlans (ssids) that wtrus must select from and use similar ssids by disruptive operators to direct traffic towards their networks. Thus, there is a need for a wlan (ssid) indication that provides access to umts based services.

Disclosure of Invention

The present invention is a method and system for switching radio access technologies between wireless communication systems connected to each other when different radio access technologies are implemented with a multi-mode wtru. Multiple wireless communication systems are deployed in overlapping coverage areas, where each wireless communication system implements a different radio access technology and is connected to one another so that services provided by one wireless communication system can be provided via the other wireless communication system. Each wireless communication system transmits an indication of the existence of an inter-working wireless communication system in the coverage area of each wireless communication system. The wtru receives indications and information regarding the inter-working wireless communication system. The wtru then initiates a handover to the inter-working wireless communication system using the received information, whereby the wtru continues to receive the same services as the wtru receives from the currently connected wireless communication system via the inter-working wireless communication system. The present invention helps reduce the time required for a multi-mode wtru to select and authenticate an inter-working wireless communication system.

Drawings

The invention will be understood in more detail from the following description of preferred embodiments and the accompanying drawings, in which:

FIG. 1 is a block diagram of a wireless communication system in accordance with the present invention;

FIG. 2 is a flow chart of a process for switching radio access technologies in accordance with the present invention; and

FIG. 3 is a signaling diagram of a handover message between a WTRU, a universal mobile telecommunications system terrestrial radio access network (UTRAN) and a WLAN for a handover from the UTRAN to the WLAN in accordance with the present invention.

Detailed Description

The term "wtru" hereinafter includes, but is not limited to, a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terms "base station" and "access point" include but are not limited to a node-B, site controller, or any other interfacing device in a wireless environment.

Fig. 1 is a block diagram of a wireless communication system 100 in accordance with the present invention. The system 100 includes at least two different types of wireless communication networks 110, 120 that implement different radio access technologies. For example, as shown in fig. 1, one type of wireless network is a umts terrestrial radio access network (utran), which preferably operates under the third generation partnership project (3GPP) standard (see utran cell 110), and another type of wireless network is a wlan 120, which preferably operates under the IEEE 802.11 standard. For purposes of illustrating the present invention, only one umts utran cell 110 is shown. It should be noted, however, that umts utran is well known to those skilled in the art and typically comprises a plurality of cells.

For convenience, the present invention is described with reference to umts terrestrial radio access networks and wlans. It should be noted, however, that a skilled artisan would appreciate that the present invention may be applied to any type of wireless communication system, and additionally may have more than two different types of wireless communication systems.

The coverage areas of the wireless communication systems 110, 120 overlap with each other. As used herein, in the case of a umts-utran-wlan example, the coverage area of the wlan 120 is typically located within the larger coverage area of the umts terrestrial radio access network cell 110. The wlan 120 is connected to the utran cell 110 such that services provided in the utran cell 110 can be relayed to the multimode wtru 102 via the wlan 120. Therefore, as mentioned above, wlan 120 is also referred to as an inter-wlan. The multi-mode wtru 102 placed in the overlapping area may be simultaneously dedicated to both types of wireless communication systems and may receive services provided by one network via the other network.

According to the present invention, the umts terrestrial radio access network cell 110 sends an indication of the presence of any inter-working wlan or, alternatively, a list of ssids of inter-working wlans located within the umts terrestrial radio access network cell 110 to the wtru 102. The indication or list of sdds may be transmitted as desired. For example, they may be propagated via a propagation control channel (BCCH) or transmitted via a Dedicated Control Channel (DCCH). Wherein the system 100 is configured to transmit the indication or list on a propagation control channel, the wtru may, but need not, provide its wlan capability (i.e., whether it is operable in a wlan or not) when connected to a utran cell 110 or when establishing a radio bearer.

According to the first embodiment, only an indication of the presence of any inter-working wlan within the umts terrestrial radio access network cell 110 is transmitted. As noted above, the indication may be transmitted as expected, but is preferably transmitted on the propagation control channel or dedicated control channel of the cell 110. The wtru 102 receives the indication and if predetermined criteria for inter-system handover (i.e., predetermined criteria for handing over the wtru 102 from the umts terrestrial radio access network cell 110 to the wlan 120) are met, the wtru 102 requests a list of ssids from the umts terrestrial radio access network cell 110. Of course, it should be appreciated that the predetermined criteria may be any type of criteria, and that the evaluation of whether to actually perform an intersystem handover may be evaluated by the wtru 102 or any network component of the network from which the handover may occur, which in this example is the umts terrestrial radio access network. Once the list of ssids is received by the wtru 102, the ssids are either passively or actively used to scan, associate and authenticate with the appropriate aps in the inter-wlan 120. This scheme ensures that the wtru 102 has access to provide connectivity to the umts terrestrial radio access network cell 110 and its third generation partnership project based services. The inter-system handoff criteria are met and with the appropriate aps within the inter-wlan 120 to handoff, the wtru 102 is handed off to the inter-wlan 120 and begins operating in between.

Alternatively, the wtru 102 may request the list of ssids before evaluating the inter-system handover criteria to confirm whether there are applicable aps before performing the evaluation.

According to the second embodiment, the system 100 operates as described above, but in this embodiment, the umts terrestrial radio access network cell 110 transmits only the ssid list, with the exception of an indication that there is any inter-working wlan within the first umts terrestrial radio access network cell 110. This provides enhanced performance without the high pin count list. Whether the first or second embodiment is implemented is operator preference.

Fig. 2 is a flow diagram of a process 200 for switching radio access technologies in accordance with the present invention. Multiple wireless communication systems are configured with overlapping coverage areas. Each wireless communication system implements a different radio access technology and is configured such that services provided by one wireless communication system can be provided via the other wireless communication system.

Each wireless communication system transmits an indication of the existence of an inter-working wireless communication system, and information (including identification number, frequency, etc.) of alternative wireless communication systems that selectively and implement different radio access technologies within the coverage area of each wireless communication system (step 202). The indication and/or information may be propagated to the wtru or may be transmitted to the wtru via a dedicated channel. The wtru may receive the indication and/or information via the currently connected wireless communication system (i.e., the wireless communication system to which the wtru is currently connected) (step 204).

Alternatively, the indication and/or information may be sent a request message in response to the information or a function report from the wtru. In response, the currently connected wireless communication system sends an indication of the availability of the inter-working wireless communication system and/or an indication of the associated wireless communication system to the wtru. In this example, the indication and/or information may be sent to the wtru via a dedicated control channel.

After receiving the indication and/or information, a determination is made whether to initiate a handoff to the inter-working wireless communication system (step 206). As described above, this determination may be made at the network or the wtru, and may be based on any predetermined criteria as desired. The handover may be initiated by a request from the user or may be initiated independently based on a service request. The wtru may display the availability of the interconnected wireless communication systems on its display screen or provide an alert to alert the same user. If a determination is made to handover the wtru to the inter-working wireless communication system and only if the indication is sent, the wtru requests information about the inter-working wireless communication system and receives it from the currently connected wireless communication system (step 208). If the message is sent with the indication or no indication is automatically sent, step 208 is skipped. The wtru then initiates a handover procedure using the received information (step 210).

As used herein in the case of the umts-utran-wlan example, the information may be the service set identifiers of the inter-working wlans, and optionally may further include the corresponding plmn identifiers and the corresponding coordinates (i.e., locations) of each of the service set identifiers. The wtru may initiate an active or passive scan for the identified wlan after receiving the ssid of the inter-working wlan. The scanning of the wireless local area network may be limited to the wireless local area network identified by the received service set identification number.

The association with a particular wlan ap may be based on channel quality measurements. If the channel quality measurements from all of the WLANs are below a predetermined threshold, the initial UMTS UTRAN connection is maintained. If an acceptable wlan ap is found, the umts terrestrial radio access network can be notified of the cell change on the dedicated channel of the cell change. Connection security can be actuated by information such as Wired Equivalent Privacy (WEP) information. The wtru continues scanning for wlan links and aps with a common ssid to cancel the links. If an acceptable ap is not found, the wtru may scan for an alternate wlan identified by a known ssid or revert to a utran connection. In this case, an inter-rat cell change indication may be sent. The selection of the handover rab may be controlled automatically based on quality measurements within a predetermined threshold or manually by user input. After the rat cell is changed, the wtru continues to receive the same services as the wtru receives from the currently connected wireless communication system via the alternate wireless communication system.

Fig. 3 is a signaling diagram of an example of a process 200 for handover of messages between a umts utran cell 110 and a wlan 120 for handover from the umts terrestrial radio access network cell 110 to the wlan 120 according to the present invention for the wtru 102. The umts utran cell 110 transmits an indication of the availability of any inter-working wlans (and/or optionally together with a list of identifiers of available wlans) (step 302). The transmission may be initiated by a report from the wtru 102 indicating the wlan capabilities of the wtru 102. The wtru 102 receives the list of inter-wlan available indicators and/or ssids (step 304). Indicating that it is to be transmitted, the wtru 102 transmits a request for an ssid of the wlan (step 306). In the case where the ssid list is transmitted with the indication or the list is not transmitted with any indication alone, step 306-310 is eliminated. Upon receiving the request, the umts utran cell 110 retrieves the ssid information (step 308). The umts utran cell 110 transmits a list of wlan ssids and optionally its associated location and plmn id (step 310). After receiving the list of ssids, the wtru 102 stores it in memory and uses the list to actively or passively scan for an appropriate ap (step 312). If the wtru 102 is within the coverage of the wlan, the wtru 102 initiates inter-wlan selection (step 312). The wtru 102 initiates wlan service with the selected wlan (step 314). As explained in more detail below (step 316), the wlan 120 may authenticate the wtru 102 and, if desired, may assign a new ip address, typically depending on the type of interconnection plan being implemented. After authentication is complete in step 318, access to the wlan is guaranteed for the wtru 102 (step 320).

As described above, different interworking schemes may be used to interconnect the wlan to the utran. For example, under current wireless communication standards, the interworking wlan may be connected to the third generation partnership project system via a core network, such as a packet-switched gateway (PDG), or via a umts terrestrial radio access network as a pipe. In the latter case, no new ip address is unassigned to the wlan re-selection (from the third generation partnership project system handoff to the wlan). In the previous case (i.e., packet-based gateway-based interconnect), a new procedure is used to assign an ip address to a wtru operating in an inter-wlan. These procedures are different from those used in third generation partnership project systems and may result in the assignment of new internet protocol addresses to wtrus.

Although depicted as separate elements, these elements may be implemented as a single Integrated Circuit (IC), such as an Application Specific Integrated Circuit (ASIC), multiple ICs, separate elements, or a combination thereof. Although features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. Furthermore, the present invention may be implemented in any type of wireless communication system.

Claims

1. A method of switching radio access technologies between wireless communication systems in an area where the wireless communication systems are configured to have overlapping coverage areas for multi-mode wtrus configured to support more than one radio access technology, wherein each wireless communication system implements a different radio access technology and is configured such that services provided by one wireless communication system can be provided via another wireless communication system, the method comprising:

each wireless communication system transmitting an indication of the existence of an inter-working wireless communication system implementing a different radio access technology available in a coverage area of each wireless communication system;

the wtru receiving the indication via a currently connected wireless communication system;

the wtru receiving information regarding the inter-working wireless communication system and determining to handover the wtru to the inter-working wireless communication system; and

the wtru uses the received information to initiate a handover to the inter-working wireless communication system,

whereby the wtru continues to receive the same services as the wtru receives from the currently connected wireless communication system via the inter-working wireless communication system.

2. The method of claim 1 wherein the indication is broadcast to the wtru.

3. The method of claim 1 wherein the indication is sent to the wtru via a dedicated control channel for the wtru.

4. The method of claim 3 wherein the indication is in response to a report specifying the performance of the wtru to support the transmission to interconnect the rat of the wireless communication system.

5. The method of claim 4 wherein information about the inter-working wireless communication system is transmitted with the indication.

6. The method of claim 1 wherein the wireless communication system is a wireless local area network and a universal mobile telecommunication system terrestrial radio access network.

7. The method of claim 6 wherein the WTRU establishes a connection with the UTRAN and receives indications of WLAN availability within the coverage of UMTS terrestrial radio access network cells.

8. The method of claim 7 wherein the indication comprises a serving set identity of a wireless local area network available to the UMTS terrestrial radio access network cell.

9. The method of claim 7 wherein the information includes the wlan location and plmn identity.

10. The method of claim 7 wherein the link to the wlan is based on channel quality measurements.

11. The method of claim 7, wherein the connection security is activated by private information such as a wired connection.

12. The method of claim 1 wherein the handoff is initiated automatically.

13. The method of claim 1 wherein the availability of the inter-working wireless communication system is alerted to the user.

14. The method of claim 13 wherein the handoff is initiated upon a user request.

15. The method of claim 1 wherein the new ip address is provided after the handoff.

16. A system for inter-wireless communication system handover of a radio access technology, comprising:

a plurality of wireless communication systems, each wireless communication system implementing a different radio access technology and having at least partially overlapping coverage areas, each wireless communication system comprising:

means for transmitting an indication of the presence of an available interconnected wireless communication system in an overlapping coverage area of the wireless communication system, wherein the system is configured such that services provided by one wireless communication system can be provided via another wireless communication system; and

means for transmitting information about the inter-working wireless communication system; and

a wireless transmit/receive unit (wtru) for supporting multiple radio access technologies, comprising:

means for receiving the indication via a currently connected wireless communication system;

means for receiving information regarding the inter-working wireless communication system to which the wtru is to be handed off; and

means for initiating a handover to the inter-working wireless communication system using the received information;

17. The system of claim 16 wherein the indication is broadcast to the wtru.

18. The system of claim 16 wherein the indication is sent to the wtru via a dedicated channel for the wtru.

19. The system of claim 18 wherein the indication is transmitted in response to the wtru performance report supporting the rat of the inter-working wireless communication system.

20. The system of claim 18 wherein information about the inter-working wireless communication system is transmitted with the indication.

21. The system of claim 16 wherein the wireless communication system is a wireless local area network and a universal mobile telecommunication system terrestrial radio access network.

22. The system of claim 16 wherein the wtru establishes a connection with the umts terrestrial radio access network and receives an indication of wlan availability via the umts terrestrial radio access network.

23. The system of claim 22 wherein the indication comprises a service set identity applicable to a wireless local area network in a umts terrestrial radio access network.

24. The system of claim 22 wherein the information includes the wlan location and plmn identity.

25. The system of claim 22 wherein the link to the wlan is based on channel quality measurements.

26. The system of claim 22, wherein the connection security is enabled by private information such as a wired connection.

27. The system of claim 16 wherein the handoff is initiated automatically.

28. The system of claim 16 wherein the warning to the user is provided with an indication of the availability of the inter-working wireless communication system.

29. The system of claim 28 wherein the handoff is initiated upon a user request.

30. The system of claim 16 wherein the new ip address is provided after the handoff.

31. In an area where a plurality of wireless communication systems are configured with overlapping coverage areas, a method for switching radio access technologies between the wireless communication systems by a multi-mode wtru configured to support more than one radio access technology, wherein each wireless communication system implements a different radio access technology and is configured such that services provided by one wireless communication system can be provided via another wireless communication system, comprising:

each wireless communication system transmitting information regarding the interconnected wireless communication systems implementing the different radio access technologies available in the coverage area of each wireless communication system;

the wtru receiving the information via a currently connected wireless communication system;

the wtru uses the information to initiate a handover to the inter-working wireless communication system,

32. The method of claim 31 wherein the information transmitted about the inter-working wireless communication system is a list of ssids.

33. The method of claim 32 wherein the inter-working wireless communication system information is a wireless local area network.

34. A system for inter-wireless communication system handover of a radio access technology, comprising:

means for transmitting information regarding available interconnected wireless communication systems in overlapping coverage areas of the wireless communication systems, wherein the system is configured such that services provided by one wireless communication system can be provided via another wireless communication system; and

means for receiving the indication via a currently connected wireless communication system; and

means for initiating a handover to the inter-working wireless communication system using the received information,

35. The system of claim 34 wherein the transmitted information regarding the interconnected wireless communication system is a list of ssids.

36. The system of claim 35 wherein the inter-working wireless communication system information is a wireless local area network.

37. The system of claim 34 wherein the wtru only receives the information determining that the wtru is to be handed off to the inter-working wireless communication system.