METHOD FOR SETTING UP A CALL

FIELD OF THE TECHNOLOGY

The present invention relates in general to telecommunication techniques, and more particularly, to a method for setting up a call in a radio communication system like a Universal Mobile Telecommunications System (UMTS) from a CELL PCH state.

BACKGROUND OF THE INVENTION

Figure 1 illustrates a message flow for setting up a call in a UMTS in the prior art when a user equipment (UE) is called, which includes the following steps:

Step 101: the Universal Terrestrial Radio Access Network (UTRAN) of the UE sends a paging message to the UE on a Common Control Channel (CCCH) of the system.

Upon receiving the paging message, the UE transfers from an IDLE state, a CELL_PCH state to a CELLJ ⁷ ACH state to decode a Fast Access Channel (FACH).

Step 102: the UE returns a CELL UPDATE message as a response to the received paging message to the UTRAN on a Random Access Channel (RACH) of the system.

Step 103: the UTRAN then sends a CELL UPDATE CONFIRM message to the UE on a FACH, in which dedicated radio resources allocated to the UE are carried.

Step 104: the UE synchronizes to the dedicated radio resources received to establish a radio link so as to establish the Radio Resource Control (RRC) connection between the UE and the UTRAN.

And after this step, a dedicated channel is established between the UE and the UTRAN. And after the dedicated channel is established, the UE transfers from the CELL_FACH state to the CELLJDCH state.

Step 105: the UE returns a CELL UDATE COMPLETE message to the UTRAN on the dedicated channel established between the UE and the UTRAN.

This CELL UDATE COMPLETE message indicates that the procedure of setting

up a call for the UE is completed. And later on, the UE can communicate with the UTRAN through the dedicated channel established.

It can be seen from the above description that the call setup procedure firstly requires a paging to occur, and then the UE is required to respond to the paging and transfers to the CELLJ ⁷ ACH state, where it is required to decode a FACH channel. It is on this FACH channel that the message allocating the dedicated channel is sent, and this message is integrity protected. Since there are so many steps in the existing call setup procedure, much time is needed to set up a call.

SUMMARY

In order to speed up the call setup procedure, the present invention provides methods for setting up a call from CELL PCH state.

According to one aspect of the present invention, the method of setting up a call includes: a UTRAN of a UE sending a call setup request, which carries dedicated radio resources allocated to the UE, to the UE on a CCCH; and upon receiving the call setup request, the UE synchronizing to the dedicated radio resources received to establish a dedicated channel between the UE and the UTRAN, in which communication between the UE and the UTRAN is conducted.

In view of the above method, since the dedicated radio resources allocated to the UE are carried in the call setup request sent on the CCCH rather than in the CELL

UPDATE CONFIRM message sent on the FACH, and there is no need for the UE transferring to the CELLJFACH state before the call is set up, the call setup procedure is simplified, and moreover the time for setting up a call is greatly reduced.

According to another aspect of the present invention, the method of setting up a call includes: at a UTRAN side of a UE, sending a call setup request, which carries dedicated radio resources allocated to the UE, to the UE on a CCCH; and

sending a confirmation message to the UE upon receiving a response message from the UE; and at the UE side, synchronizing to the dedicated radio resources received to establish a dedicated channel between the UE and the UTRAN upon receiving the call setup request; returning a response message to the UTRAN confirming the reception of the dedicated radio resources allocated to the UE after the dedicated channel between the UE and the UTRAN is established; starting a timer at the time of sending the response message; if no confirmation message is received before the timer expires, releasing the dedicated channel established; otherwise, making a integrity test to the received confirmation message, if the integrity test is successful, continue communication with the UTRAN through the dedicated channel established; and if the integrity test is failed, releasing the dedicated channel established.

In view of the above method, since the dedicated radio resources allocated to the UE are carried in the call setup request sent on the CCCH, the call setup procedure is simplified and the time for setting up a call is greatly reduced. Moreover, since the UE defers the integrity protection procedure till the time point of receiving an integrity protected RRC message, by which the network can be checked. Thus, the security of the system can be guaranteed.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a signaling flow chart for setting up a call in the prior art;

Figure 2 is a signaling flow chart for setting up a call according to a first embodiment of the present invention;

Figure 3 is a signaling flow chart for setting up a call according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and within which are shown by way of illustration specific embodiments by which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention.

In order to speed up the call setup procedure, a first embodiment of the present invention provides a method for setting up a call in a UMTS system. The message flow of this method is illustrated in Figure 2, which includes the following steps: Step 201: the UTRAN sends a call setup request to the UE on a CCCH, which carries the dedicated radio resources allocated to the UE.

Here, the call setup request may also carry the radio network identities. The radio network identities may include a Cell Radio Network Temporary Identity (C-RNTI) and a UTRAN Radio Network Temporary Identity (U-RNTI). And in this step, preferably, the call setup request refers to a paging message, which can be either a paging type 1 message or a paging type 2 message. And those skilled in the art would understand that any other message sent on the CCCH can be considered as the call setup request to carry the dedicated radio resources allocated to the UE, without departing the spirit and the protection scope of the present invention. Since a paging message can not carry the dedicated radio resources information according to the existing protocol specification, the paging message has to be extended in order to carry the dedicated radio resources allocated to the UE. To be specific, the dedicated radio resources allocated to the UE can be carried in an extended field or a reserved field of the paging message or any other message which is associated to the paging message sent to the UE.

Step 202: upon receiving the call setup request, the UE synchronizes to the dedicated radio resources received to establish a radio link, so as to establish an RRC connection between the UE and the UTRAN.

Since the dedicated radio resources allocated to the UE are carried in the call setup request, such as the paging message or any other message sent on the CCCH, the

UE can establish a dedicated channel between the UE and the UTRAN after receiving the paging message, and then transfers from any states such as an IDLE state, a CELLJPCH state or a URA_PCH state directly to a CELLJDCH state.

Step 203: the UE returns a response message, confirming the reception of the dedicated radio resources and radio network identities allocated to the UE, which indicates that the procedure of setting up a call for the UE is completed.

Preferably, the response message may be the CELL UDATE COMPLETE message.

It should be noted that the present embodiment does not limit the executing order of the above Step 202 and Step 203, that is, the Step 203 can be performed before the Step 202, or these two steps can be performed simultaneously.

According to the above procedure, since the dedicated radio resources (and radio identity) allocated to the UE are carried in the call setup request, such as the paging message or any other message sent on the CCCH, rather than in the CELL UPDATE CONFIRM message sent on the FACH, and the UE can transfer directly from the idle state, the CELLJPCH state or the URA_PCH state to the CELLJDCH state, that is, there is no need for the UE transferring to the CELL_FACH state before the call is set up, so the call setup procedure is simplified, and the time for setting up a call is greatly reduced. However, since ciphering and integrity protection are used in the UMTS on dedicated channels, the system can protect itself from intrusion and eaves dropping. But the ciphering and integrity protection are not used on broadcast channels such as the CCCH or the shared channel. Thus, according to the above embodiment, since the dedicated radio resources allocated to the UE are carried in the paging message or any other message sent on the CCCH, which is neither ciphered nor integrity protected, a security risk to the system will be caused, as it would be easy to "hi-jack" a UE, i.e. pretend to be the Public Land Mobile Networks (PLMNs) infrastructure and steal the UE from the system, which scenario is commonly known as the man in the middle scenario. In order to prevent the system from intrusion or eaves dropping, a second embodiment of the present invention provides a method for setting up a call, which

allows the UE to defer the integrity protection procedure till a point in time to be specified in the radio protocol specification. At the time point, the UE may check the network to ensure that it applies security mechanisms, and in the case the network doesn't comply, the UE will release the connections it has established to the network, assuming that it has been pirated. And in order to assure the continuity of the service, the UE then may re-establish a radio connection.

Figure 3 illustrate a message flow of a call setup procedure according to the. present embodiment. As shown in Figure 3, the method includes:

Step 301 : the UTRAN of the UE sends a call setup request to the UE on a CCCH of the system, which carries the dedicated radio resources allocated to the UE.

As mentioned in the first embodiment, in this step, the call setup request may refer to a paging message or any other message sent on the CCCH. And the paging message can either be a paging type 1 message or a paging type 2 message. And in order to carry the dedicated radio resources allocated to the UE in an existing paging message, the paging message has to be extended by means of carrying the dedicated radio resources allocated to the UE in an extended field or a reserved field of the paging message.

Step 302: the UE synchronizes to the dedicated radio resources received to establish a radio link, in order to establish an RRC connection between the UE and the UTRAN. As mentioned in the first embodiment, since the dedicated radio resources allocated to the UE are carried in the call setup request, such as the paging message or any other message sent on the CCCH, after receiving the paging message, the UE can establish a dedicated channel between the UE and the UTRAN, and then transfers directly from any state such as an IDLE state, a CELLJPCH state or a URA_PCH state to a CELLJDCH state.

Step 303: the UE returns a response message, confirming the reception of the dedicated radio resources allocated to the UE.

For example, this response message can be a CELL UPDATE COMPLETE message. It should be noted that the present embodiment does not limit the executing order

of the above Step 302 and Step 303, that is, the Step 303 can be performed before the Step 302, or these two steps can be performed simultaneously.

Step 304: at the time of sending the response message, the UE starts a timer, which counts for the waiting time of receiving a confirmation message from the UTRAN.

In this step, the time length of the timer can be pre-configured.

Step 305: upon receiving the response message, the UTRAN sends a confirmation message on the established dedicated channel, which is integrity protected, to the UE.

Step 306: if the UE receives the confirmation message before the timer expires, proceeds to step 307; and otherwise, the UE releases the RRC connection established and transfer to the IDLE state.

Step 307: the UE make an integrity test to the received confirmation message, if the integrity test of this message is successful, the UE stops the timer, and continues communication with the UTRAN with the RRC connection established; and otherwise, the UE releases the RRC connection established and transfers to the IDLE state.

It should be noted that, Figure 3 only illustrates a normal signaling procedure as that the UE receives the confirmation message before the timer expires and the integrity test to the received confirmation message is successful. The signaling procedures in other cases, such as that no confirmation message is received before the timer is overtime or the integrity test of the confirmation message is failed, are not illustrated in Figure 3.

Preferably, the confirmation message can be a new RRC message introduced in the protocol as a confirmation to the call setup request sent on the CCCH. This new introduced RRC message is integrity protected as required in the presently requirements, and the checking of which is necessary to complete the procedure and acceptance of the call setup request sent on the CCCH.

Alternatively, the confirmation message can be any integrity protected RRC message sent next to the call setup request by the UTRAN to the UE after the establishment of the RRC connection. As mentioned above, in the case that no confirmation message is received before

the timer is overtime or the integrity test of the confirmation message is failed, the UE will releases the RRC connection and transfers to the IDLE state. In this way, the system would be protected from intrusion or eaves dropping. Thus, the security of the system would be guaranteed. In order to assure the continuity of the service, in the case that the dedicated channel is released, the UE should be allowed to re-establish an RRC connection later and thus remove the possibility for the UE to have a denial of service attack.

It should be noted that the present invention is applicable to any protocol where security procedures are applied, such as integrity protection and ciphering, as in a Wideband Code Division Multiple Access (WCDMA) system or a GSM system.

Preferred embodiments have been given in the above to further describe the objective, solution and merits of the present invention. It should be noted that the foregoing is only preferred embodiments of the invention and is not for limiting the invention. Any modification, equivalent substitution, and improvement without departing from the spirit and principle of the present invention should be covered in the protection scope of the invention.