HK1176208B - Method for use in wireless communications for switching a wireless technology - Google Patents

Abstract

The present invention provides a method for use in wireless communications for switching a wireless technology, the method comprising: receiving a first message from a wireless transmit/receive unit (WTRU) via a first wireless network, wherein the first wireless network is based on a first wireless technology, the first message indicates a request for information related to wireless networks that are based on a second wireless technology, and the second wireless technology and the first wireless technology are different; and sending a second message to the WTRU via the first wireless network in response to the first message, wherein the second message includes identifiers of one or more wireless networks that are based on the second wireless technology.

Description

Method for switching wireless technology used in wireless communication

The present application is a divisional application of chinese patent application 200580007899.9 entitled "method and system for switching radio access technology between wireless communication systems using a multimode wtru", filed on 12.09/2006.

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. The interworking of umts and wlan is being developed because the coverage areas of umts and wlan are typically overlapping. An inter-working wireless local area network (I-WLAN) is a wireless local area network having access to a core network of a umts system so that services provided by the umts system can be relayed via the inter-working wireless local area network.

Currently, the network selection of the inter-working wlan requests the 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 containing a specific wlan ssid and waits for an acknowledgement of the wlan availability.

However, these techniques do not provide any indication of a wireless local area network (ssid) that is accessible to umts based services. Several solutions are designed to include broadcasting home Public Land Mobile Network (PLMN) identification on a broadcast channel on a wireless local area network. However, this technique is easily emulated because the wlan ssid is not unique (a disruptive wlan operator may broadcast the same ssid and plmn id).

Therefore, umts based inter-wlan selection for connecting to umts based services can be problematic due to the large number of wlan networks (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 wireless local area network (ssid) indication that provides access to umts based services.

Disclosure of Invention

The present invention provides a method for switching radio technologies for use in wireless communications, the method comprising: receiving a first message from a wireless transmit/receive unit (WTRU) via a first wireless network, wherein the first wireless network is based on a first wireless technology, the first message indicates a request for information related to a wireless network based on a second wireless technology, and the second wireless technology is different from the first wireless technology; and sending a second message to the WTRU via the first wireless network in response to the first message, wherein the second message includes identifiers of one or more wireless networks based on the second wireless technology.

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 are connected to one another such that services provided by one wireless communication system may be provided via the other wireless communication systems. Each wireless communication system transmits an indication of the existence of an interconnected wireless communication system in the coverage area of each wireless communication system. The wtru receives indications and information regarding the interconnected 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 to reduce the time required for a multi-mode wtru to select and authenticate an interconnected 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 handover information between a WTRU, a universal mobile telecommunications system terrestrial radio access network (UTRAN) and a WLAN for handover from the UTRAN to the WLAN in accordance with the present invention.

Detailed Description

Hereinafter, the term "wtru" 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 implementing different radio access technologies. For example, as shown in fig. 1, one type of wireless network is a umts terrestrial radio access network (umts terrestrial radio access network) (see umts terrestrial radio access network cell 110) that preferably operates under the third generation partnership project (3GPP) standard, and another type of wireless network is a wlan 120 that preferably operates under the IEEE802.11 standard. For the purpose of illustrating the present invention, only one umts terrestrial radio access network cell 110 is shown. It should be noted, however, that it is well known to those skilled in the art that universal mobile telecommunications system terrestrial radio access networks typically comprise a plurality of cells.

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

In accordance with the present invention, the umts utran cell 110 transmits an indication of the presence of any inter-working wlans, or alternatively a list of ssids of inter-working wlans located within the umts utran cell 110, to the wtru 102. The indication or list of service group identification numbers may be transmitted as expected. For example, they may be broadcast via a Broadcast 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 broadcast control channel, the wtru may, but need not, provide its wlan capability (i.e., whether it is operable in a wlan or not) when connecting to the umts utran cell 110 or establishing a radio bearer.

According to the first embodiment, only an indication of any inter-working wireless local area network presence within a universal mobile telecommunications system terrestrial radio access network cell 110 is transmitted. As described above, the indication may be transmitted as expected, but is preferably transmitted on a broadcast control channel or a dedicated control channel of the cell 110. The wtru 102 receives the indication and if the predetermined criteria for inter-system handover (i.e., the predetermined criteria for handing over the wtru 102 from the umts terrestrial radio access network cell 110 to the wlan 120) is 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 a universal mobile telecommunications system terrestrial radio access network. Once the wtru 102 receives the list of ssids, the ssids are either passively or actively used to scan, associate with, and authenticate the appropriate aps within 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 handover criteria are met and with the appropriate access point within the inter-wlan 120 to handover, the wtru 102 is handed over to the inter-wlan 120 and begins operating in between.

Alternatively, the wtru 102 may request a list of ssids before evaluating the inter-system handover criteria to determine whether there are any suitable 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 only transmits the list of ssids, except for an indication that there is any inter-wlan within the first umts terrestrial radio access network cell 110. This provides enhanced performance with a less expensive list of sdds. 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 interconnected 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 broadcast 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 transmitted a request message in response to the information or a function report from the wtru. In response, the currently connected wireless communication system transmits an indication of the availability of the interconnected 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 handover 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 user request or independently based on a service request. The wtru may display on its display screen the availability of the interconnected wireless communication system or provide an alert to alert the same user. If it is determined to switch 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-wlan 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 access point is found, the umts terrestrial radio access network can be notified of the cell change on a dedicated channel for the cell change. Connection security may be enabled by information such as Wired Equivalent Privacy (WEP) information. The wtru continues scanning for wlan connections and for the common ssid aps to cancel connections. If an acceptable ap is not found, the wtru may scan for an alternative wlan identified by a known ssid or revert to a utran connection. In this example, an inter radio access technology cell change indication may be transmitted. The selection of the handover radio access technology 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 service as the wtru receives from the currently connected wireless communication system via the alternative wireless communication system.

Fig. 3 is a signaling diagram of an example of a process 200 for handover of information between a umts terrestrial radio access network cell 110 and a wlan 120 for handover from the umts terrestrial radio access network cell 110 to the wlan 120 in accordance with the wtru 102 of the present invention. The umts terrestrial radio access network cell 110 conveys an indication of the availability of any inter-working wlan (and/or optionally together with a list of service group 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 an inter-wlan availability indication and/or a list of ssids (step 304). Only in the example where the indication is transmitted, the wtru 102 transmits a request for a service set identifier of the wlan (step 306). In the case where the list of sdds is transmitted with the indication or where the list is not transmitted with any indication alone, step 306 and 310 are deleted. Upon receiving the request, the umts terrestrial radio access network cell 110 retrieves the ssid information (step 308). The umts utran cell 110 transmits a wlan service set identifier list and optionally its associated location and plmn identity (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 appropriate aps (step 312). If the wtru 102 is within the coverage of the wlan, the wtru 102 initiates an 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 the authentication is completed in step 318, access to the wireless local area network is guaranteed for the wtru 102 (step 320).

As mentioned above, different interworking plans can be used to connect the interworking wlan to the umts terrestrial radio access network. For example, under current wireless communication standards, an interworking wlan may be connected to a third generation partnership project system via a core network, such as a packet-defined 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 reselection case (handover from the third generation partnership project system to the wlan). In the previous example (i.e., packet-based interworking), a new procedure is used to assign an ip address to a wtru operating in an interworking wlan. These procedures differ from those used in third generation partnership project systems and may result in the assignment of new internet protocol addresses to wtrus.

Although the components are depicted as separate components, these components may also be implemented as a single Integrated Circuit (IC), such as an Application Specific Integrated Circuit (ASIC), multiple integrated circuits, separate components, 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 (4)

1. A method for use in wireless communications for switching wireless technologies, the method comprising:

receiving a first message from a wireless transmit/receive unit (WTRU) via a first wireless network, wherein the first wireless network is based on a first wireless technology, the first message indicates a request for information related to a wireless network based on a second wireless technology, and the second wireless technology is different from the first wireless technology; and

sending a second message to the WTRU via the first wireless network in response to the first message, wherein the second message includes identifiers of one or more wireless networks based on the second wireless technology.

2. The method of claim 1, wherein the first wireless technology is a cellular technology.

3. The method of claim 1, wherein the second wireless technology is a Wireless Local Area Network (WLAN) technology, and wherein the identifier of the one or more wireless networks is a service set identification number (SSID).

4. The method of claim 1, wherein the second message comprises location information of the one or more wireless networks.