JP2010114660A - Mobile communication system and mobile communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system and a mobile communication method for shortening a time required for CS fall back. <P>SOLUTION: The mobile communication system includes: the base station of a first cellular system, for transmitting a paging request including the identifier of the second cellular system of a reselection destination through the wireless line of the first cellular system; and a mobile station for executing reselection from the base station of the first cellular system to the base station of the second cellular system according to the paging request. The mobile station holds information about the base station of the reselection destination in the second cellular system beforehand and executes the reselection to the base station in the second cellular system identified by the identifier on the basis of the information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to paging delivery between a plurality of cellular systems, and more particularly to a procedure for delivering paging to a circuit switched network to a packet switched network.

  In future mobile communication systems, the adoption of a new network that provides a VoIP service using IMS (IP Multimedia Subsystem) instead of a dedicated voice service network such as a circuit switched (CS) circuit is being considered. Yes. In a case where a newly installed system and a system that provides an existing CS service coexist, it is effective to examine an effective cooperation method of both. One of the cooperation methods is CS fallback (CSFallback).

  The CS fallback is a function that provides voice service by the existing CS network instead of VoIP service by IMS. Since the introduction of CS fallback does not require the introduction of additional IMS infrastructure or the addition of equipment to an existing CS network, the introduction cost can be reduced.

The conventional CS fallback procedure is described in, for example, 3GPP TS 23.272.
3GPP TS 23.272 V8.0.0 (2008-06), Annex B (normal): CS Fallback to 1xRTT, FIG. 2.3-1.

  The conventional CS fallback procedure has a problem that it takes time until a paging response is returned from the mobile station after the paging request is generated at the base station.

  Therefore, an object of the present invention is to provide a mobile communication system and method that can reduce the time required for CS fallback.

  A mobile communication system according to an aspect of the present invention includes a base station of a first cellular system that transmits a paging request including an identifier of a second cellular system that is a reselection destination through a radio link of the first cellular system, A mobile communication system having a mobile station that performs reselection from a base station of the first cellular system to a base station of the second cellular system in accordance with the paging request, wherein the mobile station Information about a reselection destination base station in the cellular system is stored in advance, and reselection to the base station in the second cellular system identified by the identifier is performed based on the information.

  In the mobile communication method according to another aspect of the present invention, the base station of the first cellular system transmits a paging request including the identifier of the second cellular system to be reselected through the radio link of the first cellular system. A mobile communication method in which a mobile station performs reselection from a base station of the first cellular system to a base station of a second cellular system according to the paging request, wherein the mobile station The information regarding the base station of the reselection destination in this cellular system is hold | maintained previously, and the reselection to the base station in the 2nd cellular system identified by the said identifier is performed based on the said information.

  ADVANTAGE OF THE INVENTION According to this invention, the mobile communication system and method which can shorten the time which CS fallback requires can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a mobile communication system according to an embodiment of the present invention. The present embodiment relates to paging distribution between a plurality of cellular systems. For example, one cellular system is configured by E-UTRAN (Evolved Universal Terrestrial Radio Access Network), and the other cellular system is configured by CDMA2000 1xRTT.

  In FIG. 1, a paging request detected in a 1 × RTT MSC (Mobile Switching Center) 1 is transmitted from a base station of the E-UTRAN 4 via a 1 × CS IWS (InterWorking Solution) 2 and an MME (Mobility Management Entity) 3. It is transmitted to a 1xCS CSFB UE (User Equipment, mobile station) 5 via a wireless line. In response to this, the UE 5 hands over to the 1xRTT CS Access 6 and performs 1x incoming call processing.

  2A and 2B show an example of a paging message used in the present embodiment. This paging message is obtained by adding a CS RAT-identity parameter 33 in addition to the ue-Identity field 30, the pagingCause field 31, and the systemInfoModification field 32. The CS RAT-identity parameter 33 is set with a RAT (Radio Access Technology) identifier, which is identification information indicating a CS fallback destination cellular system. That is, the CS RAT-identity parameter 33 indicates to which cellular system the UE 5 should perform reselection.

  Upon receiving the paging message, the UE 5 confirms the CS fallback by looking at the CS identifier set in the pagingCause field 31. Next, the UE 5 falls back to which system by looking at the CS rat-Identity parameter 33 which is the RAT identifier. Confirm whether to do. Then, reselection is executed by referring to the cellular system information stored in advance in the UE 5 corresponding to the CS RAT-Identity parameter 33.

  Here, the cellular system information stored in advance in the UE 5 is the following information. That is, the UE 5 performs location registration processing with the CDMA2000 1xRTT system while intermittently receiving paging in the idle state in the E-UTRAN 4. The UE 5 holds (preferably the best) base station identifier and timing information in the CDMA2000 1xRTT system in the UE 5.

  For this reason, in this embodiment, it is not necessary to transfer the system information of the CDMA2000 1xRTT system from the MME 3 in the reselection.

  Since FIG. 2 (a) is a format showing the structure of a paging message, the format does not need to be exactly as shown in (a), and the CS rat-Identity parameter of the present invention is added according to the conventional message format. It only has to be.

  A processing procedure of CS fallback from E-UTRAN to CDMA2000 1xRTT will be described with reference to FIG.

  (Step S1) The 1xRTT MSC1 transmits a paging request message to the 1xCS IWS2.

  (Step S2) The 1xCS IWS2 transfers a paging request message (1xRTT CS Paging) to the MME 3 through a predetermined procedure.

  (Steps S3 and S4) The paging message shown in FIG. 2 is sent from the MME 3 to the UE 5 through the E-UTRAN 4. The UE 5 refers to the CS RAT-Identity parameter 33 included in this paging message and obtains the RAT identifier. For a system identified by this RAT identifier (for example, “CDMA2000 1 × RTT system”, target base station), UE5 previously obtains and holds the identifier and timing information of the base station by the location registration process. Read this.

  (Step S5) The UE 5 performs cell reselection to the base station existing on the CDMA2000 network (1 × RTT CS) with reference to this timing information.

  (Steps S6 and S7) When the reselection to the target base station is successful, the UE 5 establishes synchronization with the base station in the uplink according to a predetermined access procedure, and returns a paging response on the line.

  As described above, a parameter (CS RAT-identity parameter 33) indicating the CS fallback destination RAT identifier is added to the paging message transmitted in step S4, and the UE 5 transits from the idle state to the active state. Instead, reselection to the base station belonging to the designated wireless access is possible.

  The procedure for setting the CS rat-Identity parameter 33 will be described in more detail.

  When a call is generated in the CDMA2000 1xRTT network, a call request message for the 1xCS IWS2 is transmitted from the 1xRTT MSC1, which has been registered in advance, in a predetermined format. Next, the 1xCS IWS 2 adds a predetermined identifier to the MME 3 that performs the mobility management of the E-UTRAN 4 and sends it out.

  The MME 3 detects the identifier of the received message, and if it is a specific identifier, the MME 3 decodes the data portion of the message to determine that it is a call request from CDMA2000 1xRTT, as shown in FIG. In the Paging field, “CDMA2000 1 × RTT” is described as the CS rat-Identity parameter 33 and transmitted to the radio base station of E-UTRAN4. As can be seen from the reference document “3GPP TS 29.277 V1.1.0 Draft (2008-06)”, the MME does not have a CDMA20001xRTT message decoding function in the conventional example.

  The MME 3 detects paging by CS fallback from the received message, and in the case of CS fallback, from the terminal information such as the identifier of the terminal to be called and the UE Capability of the terminal held in the network It is determined that it is a call request from CDMA2000 1xRTT, and as shown in FIG. 2 (b), “CDMA2000 1xRTT” is entered as CS rat-Identity parameter 33 in the Paging field and sent to the E-UTRAN4 radio base station. Send it out.

  As described above, since the UE 5 according to the embodiment of the present invention does not transition from the idle state to the active state as in the above-described prior art, the UE 5 starts receiving the paging message and starts reselection. You can save time. Accordingly, since the time until the paging response is returned to 1xMSC1 can be shortened, a high-speed paging response can be realized.

(Comparative example)
A processing procedure of CS fallback from E-UTRAN to CDMA2000 1xRTT will be described with reference to FIG. 5 as a comparative example to the embodiment of the present invention.

  (Step S1) The 1xRTT MSC 100 transmits a paging request message to the 1xCS IWS 200.

  (Step S2) The 1xCS IWS 200 transfers the paging request message to the MME 300 through a predetermined procedure.

  (Step S3) When the UE 500 is in the idle state, the MME 300 changes the UE 500 to the active state by executing a paging request procedure.

  (Step S4) The MME 300 transmits a predetermined message (Downlink S1 CDMA2000 Tunneling), and sets tunneling for passing CDMA2000 format packet data between the MME 300, the E-UTRAN 400, and the UE 500. Meanwhile, the E-UTRAN 400 sends a predetermined message (DL information transfer) to the UE 500 in order to connect the downlink with the UE 500 that has transitioned to the active state. As a result, the MME 300 can send a CDMA2000 packet format message to the UE 500. In particular, in step S4, information related to the target base station for supporting celery selection of the UE 500, that is, frequency and timing information is transmitted to the UE 500.

  (Step S5) The UE 500 performs cell reselection to a base station existing on the CDMA2000 network (1 × RTT CS) with reference to this timing information.

  (Step S6) When the reselection to the target base station is successful, the UE executes synchronization establishment in the uplink with the base station according to a predetermined access procedure, and returns a paging response on the line.

  (Step S7) If a paging response is detected in the 1xRTT MSC 100 within a predetermined time, the UE 500 executes a connection procedure of the upper and lower individual lines with the target base station according to a predetermined procedure of the CDMA2000 system, and a voice service is started.

  Here, the processing procedure of step S3 will be described in detail.

  (Step S31) The MME 300 transmits a paging message to the E-UTRAN 400. A CS fallback identifier is set in the paging message.

  (Step S32) The base station on the E-UTRAN 400 that has received the paging message maps it on the physical channel and transmits it in a predetermined procedure.

  (Step S33) When the UE 500 detects the reception of paging and confirms the CS fallback, the UE 500 executes a service request with the CS fallback identifier added to the MME 300, and transitions from the idle state to the active state.

  FIGS. 4A and 4B show information contents of the paging message used in this comparative example. This is a paging message sent from the E-UTRAN 400 to the UE 500, which is transmitted by the base station on the E-UTRAN 400 in step S32 of FIG. 5 and received by the UE 500 in step S33.

  As described above, in the comparative example, a CS identifier is set in a predetermined field (pagingCause) at the time of CS fallback. When the UE 500 refers to this field, the UE 500 interprets that CS fallback is requested. Furthermore, UE500 receives the reselection related information sent in the CDMA2000 format in step S4, executes a transition from the active state to the idle state, and executes intersystem reselection from E-UTRAN to CDMA2000.

  In such a comparative example, during the period from when a paging request is first generated in the 1xRTT MSC 100 to when a paging response from the UE 500 is returned, the UE 500 is once at the base station on the E-UTRAN 400 as described above. It took a long time to return the paging response because it transitioned to the active state.

  On the other hand, in the embodiment of the present invention, the UE starts reselection without transition from the idle state to the active state. Accordingly, since the time required for returning the paging response to the 1xRTT MSC can be shortened, a high-speed paging response can be realized.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the mobile communication system which concerns on one Embodiment of this invention. The figure which shows an example of the paging message used for the said embodiment. The figure which shows the process sequence of CS fallback from E-UTRAN to CDMA2000 1xRTT in the said embodiment. The figure which shows an example of the paging message used in the comparative example with respect to the said embodiment. The figure which shows the process sequence of CS fallback from E-UTRAN to CDMA2000 1xRTT in the comparative example with respect to the said embodiment.

Explanation of symbols

1 ... 1xRTT MSC;
2 ... 1xCS IWS;
3 ... MME;
4 ... E-UTRAN;
5 ... 1xCS CSFB UE;
6 ... 1xRTT CS Access

Claims (4)

A base station of the first cellular system that transmits a paging request including an identifier of the second cellular system to be reselected through the wireless line of the first cellular system;
A mobile communication system comprising a mobile station for performing reselection from a base station of the first cellular system to a base station of a second cellular system according to the paging request,
The mobile station
Holding in advance information about the reselection base station in the second cellular system,
A mobile communication system, wherein reselection to a base station in the second cellular system identified by the identifier is performed based on the information.   The mobile communication system according to claim 1, wherein the paging request includes a RAT (Radio Access Technology) identifier as an identifier of the second cellular system as the reselection destination.   3. The mobile communication according to claim 1, wherein the mobile station acquires and holds in advance a base station identifier and timing information in the second cellular system by executing a location registration process. 4. system. The base station of the first cellular system transmits a paging request including the identifier of the second cellular system to be reselected through the radio link of the first cellular system, and the mobile station follows the paging request according to the first paging request. A mobile communication method for performing reselection from a base station of a cellular system to a base station of a second cellular system,
The mobile station is
Pre-holding information about the reselection base station in the second cellular system,
A mobile communication method, wherein reselection to a base station in the second cellular system identified by the identifier is performed based on the information.

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