|Publication number||USRE43293 E1|
|Application number||US 12/542,722|
|Publication date||Apr 3, 2012|
|Filing date||Aug 18, 2009|
|Priority date||Jul 2, 2003|
|Also published as||CA2465139A1, CA2465139C, CN1305331C, CN1578495A, DE602004010575D1, DE602004010575T2, EP1494494A2, EP1494494A3, EP1494494B1, US7382750, US20050003819|
|Publication number||12542722, 542722, US RE43293 E1, US RE43293E1, US-E1-RE43293, USRE43293 E1, USRE43293E1|
|Original Assignee||Htc Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (14), Referenced by (2), Classifications (13), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to cellular networks. More specifically, a method for performing an Inter-RAT handover is disclosed.
2. Description of the Prior Art
Inter system handovers between Global System for Mobile Communications (GSM) and Universal Terrestrial Radio Access Network (UTRAN) are expected to play an increasingly important role, as many 3rd Generation (3G) operators will provide wide-area coverage with the GSM Base Station System (BSS) and use the 3G UTRAN in relatively small traffic hotspots. A dual-system user equipment (UE) is capable of supporting both GSM and UTRAN systems. Each time such a UE moves between the two types of coverage areas, an inter system handover must be performed. Because the 3GPP specifications make wide use of the term “radio access technology (RAT)” when referring to application network technologies, the inter system handover is often called an inter-RAT handover. An inter-RAT handover to UTRAN procedure hands the UE over from a GSM system to a UTRAN system. Similarly, an inter-RAT handover from UTAN procedure hands the UE over from the UTRAN system to a GSM system.
To perform an inter-RAT handover to UTRAN, a large amount of information, such as spreading, channelization codes and frequency information, must be provided to the UE. Relaying so much information to the UE using an extended (and possibly segmented) GSM handover command would be impractical. In particular, segmentation over more than two GSM air interface messages would have an unacceptable impact on handover performance. Consequently, the use of predefined and default Universal Mobile Telecommunications System (UMTS) radio configurations was proposed. This is discussed in detail in the specifications 3GPP 25.331 “Radio Resource Control (RRC) Protocol Specification”, and 3GPP TS 25.922 “Radio Resource Management Strategies”, both of which are included herein by reference. Attention is drawn in particular to clause 184.108.40.206 of 3GPP TS 25.922, which deals with the use of predefined radio configuration during handover from 2G (i.e., GSM) to 3G (i.e., UTRAN). In short, by utilizing default configurations stored in every UE, and up to sixteen predefined configurations that are downloadable from the UTRAN, it is possible to greatly reduce the total amount of information that needs to be sent to the UE to perform the inter-RAT handover to UTRAN procedure, and thus ensure that the handover performance is acceptable.
The UE can support both circuit switched (CS) and packet switched (PS) connections, and both types of connections must be handed over. The handover to UTRAN procedure is quite complex, and a complete description of every aspect of the procedure is quite beyond this background description. However, for more details, in addition to the above-noted specifications, attention is also drawn to 3GPP TS 23.060 “General Packet Radio Service (GPRS); Service description; Stage 2”, and 3GPP TS 24.008 “Mobile radio interface layer 3 specification; Core Network Protocols; Stage 3”, both of which are included herein by reference. Of particular note is clause 220.127.116.11 of 3GPP TS 23.060, which details aspects of the handover to UTRAN procedure for PS services; clause 18.104.22.168 of 3GPP TS 24.008, and, within 3GPP TS 25.331, clauses B.6.2, 8.3.6 and 10.2.16a.
Briefly, though, the above specifications indicate that both PS and CS services are to be handed over concurrently. As it turns out, though, the handover to UTRAN procedure can only utilize the default/predefined UMTS radio configurations for the CS connection, and consequently a great deal of information must be explicitly provided for the PS connection. As indicated above, this can lead to segmentation over more than two GSM air interface messages, which will adversely impact the handover performance. In addition, the above references do not provide a clear method for enabling the UE to determine whether or not a signaling connection exists after the handover to UTRAN procedure. This may cause the UE to subsequently use an incorrect procedure (initial direct transfer or uplink direct transfer) to transfer a message to the UTRAN.
It is therefore a primary objective of this invention to provide an inter system handover to Universal Terrestrial Radio Access Network (UTRAN) procedure that provides for the handing over of both circuit switched (CS) and packet switch (PS) services while keeping the information needed to perform the handover down to a minimum.
It is a further objective of this invention to provide the user equipment (UE) with the ability to determine what signaling connections are handed over during the handover to UTRAN procedure.
Briefly summarized, the preferred embodiment of the present invention discloses a wireless device initially having simultaneous circuit switched (CS) and packet switched (PS) services with a first radio access technology (RAT) system that is not a UMTS (for example, a GSM system). With the CS and PS services ongoing, the first RAT system transmits a HANDOVER TO UTRAN COMMAND message to the wireless device to perform a handover to UTRAN procedure. The HANDOVER TO UTRAN COMMAND message excludes information used for handing over the PS signaling connections to the UTRAN so that only CS signaling connections are handed over. The wireless device receives and parses the HANDOVER TO UTRAN COMMAND message to determine what signaling connections are being handed over. Upon determining that only CS signaling connections are being handed over, a radio resource control (RRC) layer within the wireless device informs an upper layer within the wireless device that no PS radio access bearers or no PS signaling connections are present.
It is an advantage of the present invention that by providing for the handing over of only the CS services, the amount of information needed to perform the handover procedure is reduced, and thus the handover procedure is more likely to be performed successfully. That is, excessive segmentation of the handover information is avoided. Consequently, CS services proceed smoothly around the handover procedure. PS services, which are better able to handle brief suspensions of service without inconvenience to the user, can be re-established later.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
In the following, a GSM system serves as an example of a non-UMTS system with which a handover to UTRAN procedure is performed. The method of the present invention, however, is suitable for other types of non-UMTS systems that support the handover to UTRAN procedure. Adapting the present invention method to such other systems should be clear after reading the following detailed description that is made with specific reference to a GSM system.
Please refer to
Because the UE 100 is a dual-system device, the program code 149 will support both a GSM stack (for communications with the non-UMTS GSM system, as indicated by BSS 20) and a UMTS stack (for communications with the UTRAN, as indicated by the t-RNC 10). It is the RRC layer 142 that is responsible for radio resource management by communicating with the UTRAN and GSM BSS. Relative to the RRC layer 142, there is an upper layer 143 and a lower layer 141. The lower layer 141 may include, for example, a radio link control (RLC) layer. The upper layer 143 may include a mobility management/GPRS mobility management (MM/GMM) layer 143m.
Please refer to
When generating the Relocation request ack 204, the t-RNC 10 may build the embedded Handover to UTRAN command so that only CS connection information is provided, deliberately leaving out information needed to handover any PS connections. This deliberately incomplete Handover to UTRAN command is then sent to the BSS 20 via the CN 11, and thence on to the UE RRC 142 via the Handover command 206. Alternatively, the t-RNC 10 may include a complete Handover to UTRAN command in the Relocation request ack 204, including information for both PS and CS connections. The CN 11, however, may then strip the Handover to UTRAN command of the PS information, and in the Handover Command 205 include only the information needed for handing over CS connections in the Handover to UTRAN command. This stripped Handover to UTRAN command would then be forwarded to the UE RRC 142 via the BSS 20. Finally, it may be the BSS 20 itself that generates an incomplete Handover to UTRAN command in the Handover command 206, insuring that the Handover command 206 contains only enough information to enable the UE 100 to handover the CS connections to the t-RNC 10.
Upon receiving the Handover to UTRAN command, the RRC layer 142 must parse the Handover to UTRAN command to determine what connections are being handed over. This parsing is described later. However, as the Handover to UTRAN command contains only information need to hand over the CS connections, the RRC layer 142 determines that only CS connections are being handed over, and behaves accordingly. The UE 100 thus succeeds in establishing a CS connection (or connections) with the t-RNC 10 to re-establish CS services. This is detected by the t-RNC 10, which notifies the CN 11 with a Relocation detect message 207. At this time as well, the RRC layer 142 informs the upper layer 143 (i.e., the MM/GMM layer 143m) that there are no PS signaling connections and no PS radio access bearers (RABs) Not only does this enable the upper layer 143 to know that the PS services have not been handed over, but it also enables the upper layer 143 to know that the UE 100 is now camped on a UMTS system rather than the non-UMTS system. This is useful information, as the behavior of the MM/GMM layer 143m may change depending upon the type of network upon which the UE 100 is camped.
The RRC 142 sends a Handover to UTRAN complete message 208 to the t-RNC 10 (which establishes the RRC signaling connection), completing the Handover to UTRAN procedure between the UE 100 and the t-RNC 10. The t-RNC 10 correspondingly informs the CN 11 with a Relocation complete message 209, and the CN 11 responds by sending a Clear Command 210 to the BSS 20. The Clear Command 210 is responded to with a Clear Complete message 211. In response to learning that the UE 100 is now camped on the UTRAN, the MM/GMM layer 143m initiates a routing area update procedure by sending a Routing Area Update Request 212 to the CN 11. The purpose of the routing area update procedure is to change from the old 2G-SGSN to the new 3G-SGSN. The CN 11 performs various procedures, which culminate in the sending of a Routing Area Update Accept message 213 to the MM/GMM 143, and whichresponds with a Routing Area Update Complete message 214. Thereafter, the UE 100 can work with the UTRAN to re-establish the PS services. It should be noted that the sequencing of events in the above is preferred, but may be changed. For example, the routing area update procedure may be performed before, or concurrently with, the sending of the Handover to UTRAN complete message 208. Other sequences may also possibly be changed. However, re-establishment of PS services is preferably done after the routing area update procedure.
There are two ways to perform the PS RAB re-establishment procedure. For the first, it is the UE 100 that initiates the PS RAB re-establishment procedure. For the second, it is the UTRAN (by way of the t-RNC 10) that initiates the PS RAB re-establishment procedure. Please refer to
Please refer to
The UE 100 must determine what signaling connections are handed over during the handover to UTRAN command so as to know what sort of procedure to use to transfer messages to the UTRAN (i.e., the t-RNC 10), and does so by parsing the Handover to UTRAN command. Please refer to
The format of the Handover to UTRAN command changes depending upon whether the complete specification, predefined configuration or default configuration is used. If, as shown in
As noted earlier, predefined configurations 147 are downloaded from the UTRAN and stored within the UE 100. With reference to
With reference to
In contrast to the prior art, the present invention does not include PS information in a Handover to UTRAN command when both PS and CS RABs are established with the non-UMTS network at the time of the handover procedure. This helps to ensure that CS services are handed over smoothly and in an uninterrupted manner. PS services are then restored after the CS services are handed over, and ideally after performing a routing area update procedure, as this ensures that packets are properly routed. Additionally, the present invention provides an explicit method that enables a wireless device to determine which services (CS, PS or both) are being handed over during a Handover to UTRAN procedure.
Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
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|U.S. Classification||370/331, 370/352, 370/353, 370/354|
|International Classification||H04W92/10, H04W36/14, H04W88/06, H04W4/00, H04L12/66|
|Cooperative Classification||H04W36/0066, H04W88/06, H04W92/10|
|Aug 18, 2009||AS||Assignment|
Owner name: HTC CORPORATION, TAIWAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:WU, CHIH-HSIANG;REEL/FRAME:023114/0633
Effective date: 20090805
|Dec 3, 2015||FPAY||Fee payment|
Year of fee payment: 8