Method and apparatus to prevent denial of call transfer

1 . A method for a first user equipment (UE), the method comprising:

indicating, by the first UE, that a call pull is initiated based on determining that the call pull is initiated to pull, to the first UE, a call from a second user equipment (UE);

categorizing, by the first UE, an access attempt occurred for the call pull as a mobile-terminated access attempt;

causing, by the first UE, the access attempt to be considered not barred in response to the access attempt being categorized as the mobile-terminated access attempt; and

performing, by the first UE, the access attempt to a network by transmitting a message to enable a process for the call pull,

wherein the message includes a cause value set according to the categorization of the access attempt, and wherein the cause value is set a value representing the mobile-terminated access attempt.

2 . The method of claim 1 ,

wherein the cause value is set to the value if the first UE is in an NG-RAN cell.

3 . The method of claim 1 ,

wherein the message further includes a call type.

4 . The method of claim 3 ,

wherein the cause value comprises an RRC establishment cause value indicating the mobile-terminated access attempt and/or the call type comprises a call type indicating terminating calls, if the first UE is in an E-UTRAN cell.

5 . The method of claim 1 ,

wherein indicating that a call pull is initiated comprises indicating, from an upper layer of the first UE to lower layers of the first UE that the call pull is initiated.

6 . The method of claim 5 ,

wherein categorizing the access attempt comprises categorizing, at the lower layers, the access attempt and making the access attempt comprises making, at the lower layers, the access attempt.

7 . The method of claim 6 ,

wherein the lower layers comprise a first lower layer at which to categorize the access attempt and a second lower layer at which to make the access attempt, and

wherein the method further comprises providing, from the first lower layer to the second lower layer, the access attempt categorized as the mobile-terminated access attempt.

8 . The method of claim 7 ,

wherein the upper layer comprises an application layer with an IP Multimedia Subsystem (IMS) client, the first lower layer comprises a Non-Access Stratum (NAS) layer and/or the second lower layer comprises an Access Stratum (AS) layer.

9 . A non-transitory computer-readable medium comprising a computer program encoded thereupon, the computer program comprising instructions that, when executed in hardware, perform the method of claim 1 .

10 . A method for an apparatus, the method comprising:

receiving, from a user equipment, a message to enable a process for a call pull based on determining that the call pull is initiated to pull, from the apparatus, a call to the user equipment including a cause value set according to categorization of an access attempt; and

performing an access control based on the cause value,

wherein:

the access attempt is for a call pull; and

the access attempt is categorized as a mobile-terminated access attempt.

11 . A non-transitory computer-readable medium comprising a computer program encoded thereupon, said computer program comprising instructions that, when executed in hardware, perform the method of claim 10 .

12 . A first user equipment (UE), the first UE comprising:

at least one processor; and

at least one memory storing computer program code that, when executed with the at least one processor, causes the first UE at least to:

indicate that a call pull is initiated based on determining that the call pull is initiated to pull, to the first UE, a call from a second user equipment (UE);

categorize an access attempt occurred for the call pull as a mobile-terminated access attempt;

cause the access attempt to be considered not barred in response to the access attempt being categorized as the mobile-terminated access attempt; and

perform the access attempt to a network by transmitting a message to enable a process for the call pull,

wherein the message includes a cause value set according to the categorization of the access attempt, and wherein the cause value is set to a value representing the mobile-terminated access attempt.

13 . The first UE of claim 12 ,

wherein the cause value is set to the value if the first UE is in an NG-RAN cell.

14 . The first UE of claim 12 ,

wherein the message further includes a call type.

15 . The first UE of claim 14 ,

wherein the cause value comprises an RRC establishment cause value indicating the mobile-terminated access attempt and/or the call type comprises a call type indicating terminating calls, if the first UE is in an E-UTRAN cell.

16 . The first UE of claim 12 ,

wherein the computer program code further causes the first UE, when executed with the at least one processor, at least to:

indicate, from an upper layer of the first UE to lower layers of the first UE that the call pull is initiated.

17 . The first UE of claim 16 ,

wherein the computer program code further causes the first UE, when executed with the at least one processor, at least to:

categorize, at the lower layers, the access attempt and perform, at the lower layers, the access attempt.

18 . The first UE of claim 17 ,

wherein the lower layers comprise a first lower layer at which to categorize the access attempt and a second lower layer at which to make the access attempt, and

wherein the computer program code further causes the first UE, when executed with the at least one processor, at least to:

provide, from the first lower layer to the second lower layer, the access attempt categorized as the mobile-terminated access attempt.

19 . The first UE of claim 18 ,

wherein the upper layer comprises an application layer with an IP Multimedia Subsystem (IMS) client, the first lower layer comprises a Non-Access Stratum (NAS) layer and/or the second lower layer comprises an Access Stratum (AS) layer.

20 . An apparatus comprising:

at least one processor; and

at least one memory storing computer program code that, when executed with the at least one processor, causes the apparatus at least to:

receive, from a user equipment, a message to enable a process for a call pull based on determining that the call pull is initiated to pull, from the apparatus, a call to the user equipment including a cause value set according to categorization of an access attempt; and

perform an access control based on the cause value,

wherein:

the access attempt is for a call pull; and

the access attempt is categorized as a mobile-terminated access attempt.

21 . The method of claim 1 , wherein the value is 0.