(19) & (11) EP 2 254 370 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 24.11.2010 Bulletin 2010/47 H04W 36/14 (2009.01) (21) Application number: 10163065.5 (22) Date of filing: 18.05.2010 (84) Designated Contracting States: (72) Inventor: Wu, Chih-Hsiang AL AT BE BG CH CY CZ DE DK EE ES FI FR GB 330, Taoyuan City Taoyuan County (TW) GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR (74) Representative: 2K Patentanwälte Blasberg Designated Extension States: Kewitz & Reichel BA ME RS Partnerschaft Corneliusstraße 18 (30) Priority: 21.05.2009 US 180138 P 60325 Frankfurt am Main (DE) (71) Applicant: HTC Corporation Taoyuan County 330 (TW) (54) Method of handling Single Radio Voice Call Continuity (SRVCC) handover in wireless communication system (57) A method of handling at least a call in handover cation network. Further, the wireless communication de- in a wireless communication system and a communica- vice sets a stream identifier of each of the CS calls to an tion device using the same are proposed. The wireless identifier value. The method enables smooth single radio communication system includes at least a wireless com- voice call continuity (SRVCC) handover from the PS call munication network and a wireless communication de- in one wireless communication network to the CS call in vice. The method includes the following steps. First, a another wireless communication network. In addition, the wireless communication device receives a message for method also enables SRVCC multicall handover from switching at least a packet-switched (PS) call to at least the PS call in one network operation mode to the CS call a circuit-switched (CS) call from the wireless communi- in another wireless communication network. EP 2 254 370 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 2 254 370 A1 2 Description [0004] Moreover, if the UE supporting the multicall, the UE has to include the SI information element in the SET- BACKGROUND OF THE INVENTION UP message. For the first call (i.e., when there is no other ongoing call), the SI may initially start from 1. Usually the Field of the Invention 5 SI value may have three bits. However, if the UE does not set the SI value for the CS call but the network sets [0001] The present invention relates to a method of it to 1, later on when the UE initiates a CS streaming call handling at least a call in handover in a wireless commu- and the UE sets the SI value to 1 for the CS streaming nication system and a wireless communication device call, it may cause the streaming CS call setup failed since using the same, and more particularly, to a method of 10 the UTRAN (or the GERAN) considers the SI = 1 already handling at least a packet-switched (PS) call handover been set for one CS voice call. Beside, the UTRAN or to at least a circuit- switched (CS) call in different wireless the GERAN cannot use the traffic channel configuration communication networks and a wireless communication of the CS voice call for the CS streaming call since radio device using the same. access bearer (RAB) identifier or the traffic channel iden- 15 tifier is required to be identical to the SI. In addition, it is Description of Related Art also currently not clear how to handle multicall in hando- ver from the E- UTRAN to either the UTRAN or the GER- [0002] Currently, evolved Universal Telephone Sys- AN. tem Terrestrial Radio Access Network (E- UTRAN) is de- [0005] Therefore, how to handle calls or multicall in signed to have only packet-switched (PS) connections, 20 handover in wireless communication systems and relat- and voice call applications in the E-UTRAN have to be ed communication devices becomes an important issue provided in a form of voice over Internet Protocol (VoIP) to be researched and discussed. application or an IP multimedia subsystem (IMS) voice call. However, most operators runningthe E- UTRAN may SUMMARY OF THE INVENTION still have other types of networks based on other wireless 25 communication technologies, and the operators would [0006] Accordingly, the present invention proposes a like to have a seamless and smooth handover of the VoIP method of handling at least a PS call handover to at least call or the IMS voice call from the UTRANE- to other a CS call in different wireless communication networks networks. For example, one of the operators running the and a wireless communication device using the same. E-UTRAN may have an UTRAN and a Global System 30 The method enables a smooth single radio voice call con- for Mobile communications (GSM) Enhanced data rate tinuity (SRVCC) handover from at least a PS call in one for GSM evolution radio access network (thereafter ab- network operation mode to at least a CS call in another breviated as GERAN). When a user equipment (UE) with network operation mode. In addition, the method also multicall capability has the IMS voice call under one of enables a SRVCC multicall handover from at least a PS the PS domain connections in the E-UTRAN and the E- 35 call in one wireless communication network to at least a UTRAN initiates a single radio voice call continuity CS call in another wireless communication network. (SRVCC) handover correspondingly, the UE may trans- [0007] The present invention proposes a method of fer the IMS voice call to a CS call in either the UTRAN handling at least a call in handover in a wireless commu- or the GERAN since the CS call has better quality of nication system. The wireless communication system in- service (QoS) capabilities such as low latency, low bit 40 cludes at least a wireless communication network and a error rate, and low timing jitter. wireless communication device. The method includes [0003] It is currently not clear on whether the UE and the following steps. First, the wireless communication de- the UTRAN (or the GERAN) sets the identical stream vice receives a message for switching at least a PS call identifier (SI) for the CS call. Usually, the UE supporting to at least a CS call from the wireless communication multicall (i.e. having multicall capability) includes the SI 45 network. Further, the wireless communication device in a SETUP message which is to be sent to the UTRAN sets a stream identifier to at least the CS call to an iden- or the GERAN. The networks (e.g., the UTRAN or the tifier value. GERAN) which support multicall may interpret the SI val- [0008] The present invention also proposes the wire- ue after receiving the SETUP message from the UE as less communication device for handling at least a call in the following. If the UE generates a new SI value at an 50 handover in the wireless communication system. The initiation of an originating call, then a new traffic channel wireless communication device includes a message re- has to be assigned to the originating call. On the contrary, ceiving module, a stream identifier configuration module, if the UE just indicates an existing SI value, then the in- a transceiver module, a memory module, and a proces- dicated traffic channel has to be used for the originating sor. The message receiving module receives a message call. The UE supporting multicall shall never send an ad- 55 for switching PS calls to CS calls from a wireless com- ditional SETUP with indication that a new traffic channel munication network. Besides, the stream identifier con- is requested to a wireless communication network that figuration module sets a stream identifier of each of the does not support multicall. CS calls to an identifier value. Further, the transceiver 2 3 EP 2 254 370 A1 4 module transmits information to and receives information emplary embodiment of the present invention. from the wireless communication network, wherein the [0016] FIG. 4 is a flow diagram illustrating an exem- information received includes the message for switching plary process of handling at least a call in handover in a the PS calls to the CS calls from the wireless communi- wireless communication system according to a fourth ex- cation network. The memory module stores at least the 5 emplary embodiment of the present invention. message for switching the PS calls to the CS calls from [0017] FIG. 5 is a flow diagram illustrating an exem- the wireless communication network. In addition, the plary process of handling at least a call in handover in a processor executes the message receiving module and wireless communication system according to a fifth ex- the stream identifier configuration module, and controls emplary embodiment of the present invention. the transceiver module. 10 [0018] FIG. 6 is a schematic block diagram illustrating [0009] The present invention proposes a method of a structure of a wireless communication device for han- handling at least a call in handover in a wireless commu- dling at least a call in handover in a wireless communi- nication system and a wireless communication device cation system according to a sixth exemplary embodi- for handling at least a call in handover in a wireless com- ment of the present invention. munication system. The wireless communication device 15 sets the stream identifier of at least the CS call to the DESCRIPTION OF EMBODIMENTS identifier value after receiving a message for switching at least the PS call in one operation mode to at least the [0019] Reference will now be made in detail to the CS call in another operation mode, wherein the message present embodiments of the invention, examples of is sent from the wireless communication network.