INCOMPATIBILITY

TECHNICAL FIELD

Aspects of this disclosure relate to handling NAS incompatibility. BACKGROUND 3 GPP networks are beginning to support devices and customers with very different

characteristics, such as machine type devices, mobile virtual network operator (MVNO), data usage, etc. These classes of devices and customers may have different requirements from the core network (CN) in terms of optional feature support, traffic characteristic support, availability, congestion management, ratio of signaling to user plane traffic, etc. As we move forward the classes of devices/customers will continue to increase. One cost effective mechanism for operators to support these different classes of devices and customers is to create separate dedicated core networks (DCNs) consisting of specialized core network elements that are designed and deployed to meet the requirements of these different devices and customers. It is cost-effective as the network availability or redundancy requirements may be easier to meet with different hardware and/or software than the existing core network. Also, creating separate core networks enables independent scaling or specific feature provisioning for specific user or traffic types and isolating specific users and traffic from each other.

SUMMARY

One way to determine which DCN should be used to provide a service to a wireless

communication device (WCD) (e.g., smartphone, tablet, phablet, machine type communication device, etc.) is for the WCD to provide to a base station that can serve the WCD information identifying a requested non-access stratum (NAS) type (e.g., a NAS type identifier). For example, the WCD can include in a request message, such as a connection request (e.g., an Radio Resource Control (RRC) Connection Request) or other request, information identifying a requested NAS type.

The various NAS types that a WCD may request indicates a variant or version of the NAS protocol (or equivalent protocol), which is terminated by the UE and a core network node (e.g., the Mobility Management Entity (MME) or the Serving GPRS Support Node (SGSN)) and which is used to support functionality such as authentication, admission control, mobility handling, and similar. The information identifying a requested NAS type may be a protocol version indicator, a compatibility indicator, or other indicator which enables a RAN node to select a matching core node which is able to terminate the NAS signaling matching the requested NAS type.

However, a problem arises because, if the requested NAS type is not supported, then the request will fail and the WCD will not be informed as to why the failure occurred, which can lead to the WCD re-sending the request message. This, in turn, leads to an increase in radio access network (RAN) network signaling load and potentially also signaling to a core network (CN).

What is desired, therefore, are systems and methods to overcome these disadvantages. This disclosure provides such system and methods.

Some of the disadvantages are at least mitigated by a first aspect of the present solution directed to a method performed by a WCD. The method comprising: receiving at the WCD, a message transmitted by a base station of a RAN; and determining by the WCD, whether the transmitted message includes information indicating that NAS type requests are supported.

Some of the disadvantages are at least mitigated by another aspect of the present solution directed to a method performed by a WCD. The method comprising: the WCD transmitting to a base station a request message comprising information identifying a requested NAS type;

receiving, at the WCD, a response message transmitted by the base station in response to the request message, the response message indicating whether or not the requested NAS type is supported. Some of the disadvantages are at least mitigated by still another aspect of the present solution directed to a method performed by a base station. The method comprising: generating, by the base station, a message comprising system information; transmitting, by the base station, the message comprising the system information, wherein the system information comprises information indicating that NAS type requests are supported.

Some of the disadvantages are at least mitigated by still another aspect of the present solution directed to a method performed by a base station. The method comprising: receiving, at the base station, a request message transmitted by a WCD, the request message comprising information identifying a requested NAS type; in response to receiving the request message, the base station determining whether the identified requested NAS type is supported; and the base station transmitting to the WCD a response message in response to the request message, wherein the content of the response message depends on whether the identified requested NAS type is supported.

The above and other aspects and embodiments are described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments. FIG. 1 illustrates a wireless communication system 100 according to some embodiments. FIG. 2 is a flow chart illustrating a process according to some embodiments.

FIGs. 3, 4 and 5 are message flow diagrams illustrating one or more processes according to some embodiments.

FIG. 6 is a flow chart illustrating a process according to some embodiments.

FIG. 7 is a flow chart illustrating a process according to some embodiments. FIGs. 8, 9 and 10 are message flow diagrams illustrating one or more processes according to some embodiments.

FIGs. 11, 12, 13, 14 and 15 are flow charts illustrating various processes according to some embodiments.

FIG. 16 is a block diagram of a WCD according to some embodiments.

FIG. 17 is a block diagram of a base station according to some embodiments.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system 100 according to some embodiments. As shown in FIG. 1, system 100 includes a WCD 101 that is able to send to a base station 105 (e.g., an evolved NodeB (eNodeB), a radio network controller (RNC), a base station system (BSS), or other base station) of a radio access network (RAN) 102 (e.g., a UTRAN, EUTRAN, GERAN, etc.) a message comprising information indicating a requested non-access stratum (NAS) type. As shown, the base station 105 is connected (directly or indirectly) to one or more core networks 104.

FIG. 2 is a flow chart illustrating a process 200 performed by WCD 101 (e.g. a user equipment (UE) or similar. The process 200 may be used, for example, in an attempt by the WCD to use a particular one of several different predefined types of NAS protocols. Here, the NAS may be seen as the highest stratum of the control plane between the WCD and a mobility management entity (MME) or similar entity in the CN. Main functions of a NAS protocol may e.g. be the support of mobility of the WCD and session management procedures etc. to establish and maintain IP connectivity between the WCD and a packet data network gateway (PDN GW) or similar gateway in the CN. For example, a NAS control protocol may support various tasks such as e.g. EPS bearer management; Authentication; ECM-IDLE mobility handling; Paging origination in ECM-IDLE and Security control etc. The NAS is defined in contrast to the Access Stratum which is responsible for carrying information over the wireless portion of the network. In an embodiment, process 200 begins at step 201, in which WCD 101 receives a message 302 (see figure 3) transmitted by base station 105 of a RAN 102 (message 302 may be broadcast by the base station). In some embodiments, message 302 may include one or more System

Information Blocks (SIBs) or similar that includes information indicating that non-access stratum (NAS) type requests are supported. While several of the figures illustrate Radio Resource Control (RRC) signaling (see e.g., figures 3-5 and 8-10) related to UTRAN and E-UTRAN environments, this disclose is not so limited since it applies to other RANs, such as GERAN, that do not use RRC signaling.

In step 203 (see figure 2), the WCD determines whether the message 302 includes the information indicating that NAS type requests are supported.

Steps 201 and 203 are further illustrated in the message flow diagrams shown in FIGs. 3-5, which show, among other things, WCD 101 receiving a broadcast SIB.

FIG. 3 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

In action 301a the WCD 101 is searching for a cell with support for new NAS type, e.g.

expecting to receive a message 302 that may include one or more System Information Blocks (SIBs) or similar that includes information indicating that NAS type requests are supported.

Action 301b corresponds to step 201 in figure 2 wherein the WCD 101 receives the message 302 as described above with reference to figure 2, wherein the message 302 includes information indicating that NAS type requests are supported.

In actions 303a-303b the indication in the received message 302 informs the WCD that the base station 105 understands the concept of NAS types and will process a requested NAS type if it's indicated in an RRC Connection Request message. As a consequence, the WCD continues with a connection request for a specific NAS type. Action 305 corresponds to step 602 in figure 6, as will be described in more detail below, wherein the WCD 101 transmits to the base station 105 a request message 304 (e.g., an RRC Connection Request in the UTRAN/E-UTRAN environments) comprising information identifying a requested NAS type (e.g., a NAS type identifier).

In action 307 the base station 105 determines, as a response to receiving message 304, that the requested NAS type is supported by an evolve packet core (EPC) serving the base station 105 and the base station continues to process the connection request normally. In action 309a the WCD 101 receives a response message 306 (e.g., an RRC Connection Setup message or other acknowledgment message acknowledging the request message 304) transmitted by the base station 105 in response to the request message 304 sent in step 305 above.

In action 309b the WCD 101 then respond to message 306 by transmitting to the base station 105 an RRC Connection Setup Complete message 308, which message may include a NAS Attach request or other NAS message (e.g., Routing Area Update, Tracking Area Update, Service Request, etc.).

FIG. 4 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

In action 401 the WCD 101 is searching for a cell with support for new NAS type, e.g. expecting to receive a message 302 that may include one or more System Information Blocks (SIBs) or similar that includes information indicating that NAS type requests are supported.

Action 403 corresponds to step 201 in figure 2 wherein the WCD 101 receives the message 302 as described above with reference to figure 2, where the message 302 doesn't include any information indicating that NAS type requests are supported. In Actions 405a-405b the absence in the received message 302 of information indicating that NAS type requests are supported informs the WCD that the base station 105 doesn't understand the concept of NAS type. The WCD may determine that the cell is a not suitable cell and as a consequence not initiate a connection request in the cell.

FIG. 5 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

Action 501 corresponds to step 201 in figure 2 wherein the WCD 101 receives a message 302 as described above with reference to figure 2, wherein the message 302 includes information indicating that NAS type requests are supported.

In actions 503a-503b the indication in the received message 302 informs the WCD that the base station 105 understands the concept of NAS types and will process a requested NAS type if it's indicated in an RRC Connection Request message. As a consequence, the WCD continues with a connection request for a specific NAS type.

Action 505 corresponds to step 602 in figure 6 as will be described in more detail below, wherein the WCD 101 transmits to the base station 105 a request message 304 (e.g., an RRC Connection Request in the UTRAN/E-UTRAN environments) comprising information identifying a requested NAS type (e.g., a NAS type identifier).

In action 507 the base station 105 determines, as a response to receiving message 304, that the requested NAS type is supported by any evolve packet core (EPC) serving the base station 105 and the base station rejects the connection request. In actions 509a-509b, after transmitting the request message 304 to the base station 105, the WCD 101 may receive a reject message (e.g., message 501a or 501b) transmitted by the base station in response to the request message. The reject message can include information indicating that requested NAS type identified in the request message 304 is not supported (see e.g., message 501a). In some embodiments, the request message 304 includes information identifying a public land mobile network (PLMN), and the reject message comprises information indicating that requested NAS type identified in the connection request is not supported by the identifying PLMN (see e.g., message 501b).

FIG. 6 is a flow chart that illustrates example steps that WCD 101 may take in response to the determination made in step 203, also shown in e.g. fig. 2.

For instance, in step 602, as a result of determining that the message 302 includes information indicating that NAS type requests are supported, the WCD transmits to the base station 105 a request message 304 (e.g., an R C Connection Request in the UTRAN/E-UTRAN

environments) comprising information identifying a requested NAS type (e.g., a NAS type identifier). This feature is further shown in message flows shown in FIG. 3 and FIG. 5. In a GERAN environment, request message 304 may be the first RLC data block used to transfer an LLC PDU (i.e. including the mobility message on the NAS layer) once a temporary block flow (TBF) has been established.

In step 604, as a result of determining that the message does not include information indicating that NAS type requests are supported, the WCD refrains from initiating a connection request in a cell in which the WCD is located, where the base station serves the cell. That is, for example, WCD 101 refrains from transmitting the request message 304.

If the requested NAS type identified in the request message is supported, then the base station may accept the request. Thus, after transmitting the request message 304 to the base station, the WCD 101 may receive a response message 306 (e.g., an RRC Connection Setup message or other acknowledgment message acknowledging the request message 304) transmitted by the base station 105 in response to the request message (see e.g. FIG. 3). The WCD may then respond to the RRC Connection Setup message 306 by transmitting to the base station an RRC Connection Setup Complete message 308, which message may include a NAS Attach request or other NAS message (e.g., Routing Area Update, Tracking Area Update, Service Request, etc.) In some embodiments, the WCD may include such NAS messages in the request message 304. If the requested NAS type identified in the request message is not supported, then the base station 105 may reject the request. Thus, after transmitting the request message 304 to the base station, the WCD 101 may receive a reject message (e.g., message 501a or 501b, see FIG. 5) transmitted by the base station in response to the request message. The reject message can include information indicating that requested NAS type identified in the request message is not supported (see e.g., message 501a). In some embodiments, the request message 304 includes information identifying a public land mobile network (PLMN), and the reject message comprises information indicating that requested NAS type identified in the connection request is not supported by the identifying PLMN (see e.g., message 501b).

FIG. 7 is a flow chart illustrating another example process 700 performed by WCD 101. The process may be used, for example, in an attempt by WCD 101 to use a particular one of several different types of NAS protocols. In an embodiment, the process begins at step 702, in which WCD 101 transmits to base station 105 a request message 802, such as a connection request (e.g., an RRC Connection Request) (see FIG. 8). The request message comprises information identifying a requested NAS type. In some instances, the WCD performs step 702 without having previously received any message from the base which indicates whether NAS type requests are supported. For example, step 702 may be performed as a result of WCD 101 selecting a cell served by base station 105, wherein the selection of the cell occurs after WCD 101 receives information (e.g., one or more SIBs 801) broadcast or otherwise transmitted by base station 105, wherein the information transmitted by base station 105 does not include information indicating that NAS type requests are supported. This feature is illustrated in FIG. 8, which shows base station 105 broadcasting a SIB 801, which is received by WCD 101.

In step 704, the WCD 101 receives a response message (e.g., message 804, 901, 1001a, or 1001b - see figures 8-10) transmitted by the base station 105 in response to the request message 802, the response message indicates at least whether or not NAS type requests are supported. For example, if NAS type requests are supported and the particular NAS type requested is supported, then the base station will respond to the request message 802 by transmitting response message 804, which includes information indicating that NAS type requests are supported. More specifically, in some embodiments, the response message 804 indicates that the specific requested NAS type is supported. On the other hand, if NAS type requests are not supported, the base station may transmit a R C Connection Setup message 901 (see FIG. 9), which does not include information indicating that NAS type requests are supported (this feature is shown in message flow shown in FIG. 9). For example, a base station which does not understand and ignores a received NAS type request, responds without indicating that NAS type requests are supported. In this case, the WCD aborts the connection request since the base station is unable to process a NAS type request. As another example, if NAS type requests are supported but the particular NAS type requested is not supported, then the base station may respond to the request message 802 by transmitting an acknowledgment message rejecting the request message (e.g. reject message 1001a or reject message 1001b).

FIG. 8 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

In action 810 the WCD 101 is searching for a cell with support for new NAS type, e.g. expecting to receive a message 801 that may include one or more System Information Blocks (SIBs) or similar that includes information indicating that NAS type requests are supported.

Action 812 the WCD 101 receives information (e.g., one or more SIBs 801) broadcast or otherwise transmitted by base station 105, wherein the information transmitted by base station 105 does not include any information indicating that NAS type requests are supported. In action 814 the WCD 101 transmits to base station 105 a request message 802, such as a connection request (e.g., an RRC Connection Request). The request message comprises information identifying a requested NAS type.

In action 815 the base station 105 determines, as a response to receiving message 802, that the requested NAS type is supported by an evolve packet core (EPC) serving the base station 105 and the base station continues to process the connection request normally. In action 816 the WCD 101 receives a response message 804 transmitted by the base station 105 in response to the request message 802. The response message indicates at least whether or not NAS type requests are supported. For example, if NAS type requests are supported and the particular NAS type requested is supported, then the base station will respond to the request message 802 by transmitting response message 804, which includes information indicating that NAS type requests are supported. More specifically, in some embodiments, the response message 804 indicates that the specific requested NAS type is supported. In actions 818a-818b the indication in the received message 804 informs the WCD that the base station 105 understands the concept of NAS types and will process a requested NAS type if it's indicated in an RRC Connection Request message. As a consequence, the WCD continues with a connection request for a specific NAS type. In action 820 the WCD 101 then respond to message 804 by transmitting to the base station 105 an RRC Connection Setup Complete message 308, which message may include a NAS Attach request or other NAS message (e.g., Routing Area Update, Tracking Area Update, Service Request, etc.). FIG. 9 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

In action 910 the WCD 101 is searching for a cell with support for new NAS type, e.g. expecting to receive a message 801 that may include one or more System Information Blocks (SIBs) or similar that includes information indicating that NAS type requests are supported.

Action 912 the WCD 101 receives information (e.g., one or more SIBs 801) broadcast or otherwise transmitted by base station 105, wherein the information transmitted by base station 105 does not include any information indicating that NAS type requests are supported. In action 914 the WCD 101 transmits to base station 105 a request message 802, such as a connection request (e.g., an R C Connection Request). The request message comprises information identifying a requested NAS type. In action 916 the base station 105 determines, as a response to receiving message 802, that the requested NAS type is supported by the base station 105 and the base station continues to process the connection request normally.

In action 918 the WCD 101 receives a response message 901 transmitted by the base station 105 in response to the request message 802. The response message indicates, since NAS type requests are not supported, the base station transmits a message 901 (e.g. a RRC Connection Setup message), which does not include information indicating that NAS type requests are supported. For example, a base station which does not understand and ignores a received NAS type request, responds without indicating that NAS type requests are supported.

In Actions 920a-920b the absence in the received message 901 of information indicating that NAS type requests are supported informs the WCD that the base station 105 doesn't understand the concept of NAS types. The WCD may determine that the cell is a not suitable cell and as a consequence not initiate a connection request in the cell.

FIG. 10 is a message flow diagram illustrating a processes according to some embodiments comprising a number of actions as follows:

In action 110 the WCD 101 is searching for a cell with support for new NAS type, e.g. expecting to receive a message 801 that may include one or more System Information Blocks (SIBs) or similar that includes information indicating that NAS type requests are supported.

Action 112 the WCD 101 receives information (e.g., one or more SIBs 801) broadcast or otherwise transmitted by base station 105, wherein the information transmitted by base station 105 does not include any information indicating that NAS type requests are supported. In action 114 the WCD 101 transmits to base station 105 a request message 802, such as a connection request (e.g., an RRC Connection Request). The request message comprises information identifying a requested NAS type. In action 116 the base station 105 determines, as a response to receiving message 802, that the requested NAS type is not supported by any evolve packet core (EPC) serving the base station 105 and the base station rejects the connection request.

In actions 118a-118b, after transmitting the request message 802 to the base station 105, the WCD 101 may receive a reject message (e.g., message 1001a or 1001b) transmitted by the base station in response to the request message. The reject message can include information indicating that requested NAS type identified in the request message 802 is not supported (see e.g., message 1001a). In some embodiments, the request message 802 includes information identifying a public land mobile network (PLMN), and the reject message comprises information indicating that requested NAS type identified in the connection request is not supported by the identifying PLMN (see e.g., message 1001b).

FIG. 11 illustrates an example process 1100 that WCD 101 may perform in response to receiving in step 704 the response message transmitted by the base station 105. As mentioned above and as shown in FIG. 8, the request message transmitted by the WCD in step 702 may be a connection request (e.g., RRC Connection Request message), and the response message received in step 704 may be a connection setup message (e.g., an RRC Connection Setup message 804, 901) or a reject message (e.g., an RRC Connection Reject message 1001a, 1001b). In some embodiments, if NAS type requests are supported, but the particular requested NAS type identified in request message 802 is not supported, then base station may transmit to the WCD a reject message 1001a or 1001b (e.g., an RRC Connection Reject message) in response to the request message 802. The reject message may comprise information indicating that the requested NAS type identified in the request message is not supported (see e.g., reject message 1001a shown in FIG. 10). In an embodiment, the request message includes information identifying a PLMN, and the RRC Connection Reject message comprises information indicating that the requested NAS type identified in the request message is not supported by the identifying PLMN (see e.g., reject message 1001b shown in FIG. 10).

In step 1101, the WCD determines whether the base station transmitted a reject message. If so, the process proceeds to step 1106.

In step 1102, the WCD determines whether the response message includes information indicating that the requested NAS type is supported. If the response message includes information indicating that the requested NAS type is supported, then the process proceeds to step 1104, otherwise the process proceeds to step 1106.

In step 1104, as a result of determining that the response message includes information indicating that NAS type requests are supported, the WCD may transmit to the base station another message (e.g., an RRC Connection Setup Complete message 806 in response to the RRC Connection Setup message 804).

In step 1106, as a result of determining that the RRC Connection Setup message does not include information indicating that NAS type requests are supported or determining that a reject was transmitted, the WCD refrains from transmitting to the base station the RRC Connection Setup Complete message 806.

FIG. 12 provides a flow diagram that illustrates an example process 1200 performed by a base station 105. The process may be used, for example, by the base station to allow WCD 101 to use a particular one of several different types of NAS protocols. In an embodiment, process 1200 begins at step 1202, in which the base station generates a message (e.g., message 302) comprising system information.

In step 1204, the base station transmits the message comprising the system information (e.g., broadcasts the message or uses dedicated signaling to send the message only to WCD 101). The system information comprises information indicating that non-access stratum (NAS) type requests are supported. FIG. 13 illustrates additional steps that the base station 105 may perform. For instance, in step 1302, the base station receives a request message transmitted by WCD 101 (e.g., request message 304), where the request message comprises information identifying a requested NAS type. In response to the request message, the base station transmits to the WCD a response message, where the content of the response message depends on whether the identified requested NAS type is supported.

For example, in step 1304, the base station, in response to receiving the request message, determines whether the identified requested NAS type is supported. If the requested NAS type is supported, the process proceeds to step 1308, otherwise the process proceeds to step 1306. In step 1308, as a result of determining that the requested NAS type is supported, the base station transmits to the WCD a connection setup message (e.g., an RRC Connection Setup message). And in step 1306, as a result of determining that the requested NAS type is not supported, the base station transmits to the WCD a response message in which the content of the response message is a reject message indicating that the connection request is rejected.

FIG. 14 provides a flow diagram that illustrates an example process 1400 performed by the base station 105. The process may be used, for example, by the base station to allow WCD 101 to use a particular one of several different types of NAS protocols.

In an embodiment, process 1400 begins at step 1401, in which the base station receives a request message transmitted by WCD 101 (e.g., request message 802), wherein the request message comprises information identifying a requested NAS type. In some instances, the base station performs step 1401 without having previously broadcasted (or transmitted to the WCD) any message that comprises system information that indicates that NAS type requests are supported (this feature is further shown in FIG. 8).

In step 1403, in response to receiving the request message, the base station determines whether the identified requested NAS type is supported. In step 1405, the base station transmits to the WCD a response message (e.g., setup message 804 or reject message 1002) in response to the request message. The content of the response message depends on whether the identified requested NAS type is supported. For example, as shown in FIG. 15, if the base determines that the requested NAS type is not supported, then the base station transmits to the WCD a reject message (step 1502) (e.g., message 1001a or 1001b) otherwise, when the base station determines that the requested NAS type is supported, the base station transmits to the WCD a connection setup message (step 1504) (e.g. message 804). In some embodiments, The WCD is configured to respond to the connection setup message 804 by transmitting to the base station a setup complete message (e.g., message 806).

FIG. 16 is a block diagram of an embodiment of WCD 101. As shown in FIG. 16, WCD 101 may include: a data processing system (DPS) 1602, which may include one or more processors 1655 (e.g., a general purpose microprocessor and/or one or more other data processing circuits, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); a radio transceiver 1605 coupled to an antenna 1622 for use wirelessly transmitting data; and a data storage system 1612, which may include one or more non- volatile storage devices and/or one or more volatile storage devices (e.g., random access memory (RAM)) for storing data. In embodiments where WCD 101 includes a general purpose microprocessor, a computer program product (CPP) 1641 may be provided. CPP 1641 includes a computer readable medium (CRM) 1642 storing a computer program (CP) 1643 comprising computer readable instructions (CRI) 1644. CRM 1642 may be a non-transitory computer readable medium, such as, but not limited, to magnetic media (e.g., a hard disk), optical media (e.g., a DVD), memory devices (e.g., random access memory), and the like. In some

embodiments, the CRI 1644 of computer program 1643 is configured such that when executed by data processing system 1602, the CRI causes the WCD 101 to perform steps described above (e.g., steps described above with reference to the flow charts). In other embodiments, WCD 101 may be configured to perform steps described herein without the need for code. That is, for example, data processing system 1602 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software. FIG. 17 is a block diagram of an embodiment of base station 105. As shown in FIG. 17, base station 105 may include: a data processing system (DPS) 1702, which may include one or more processors 1755 (e.g., a general purpose microprocessor and/or one or more other data processing circuits, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); a radio transceiver 1705 coupled to an antenna 1722 for use wirelessly transmitting data; a network interface 1007 for connecting the base station to a network; and a data storage system 1712, which may include one or more non-volatile storage devices and/or one or more volatile storage devices (e.g., random access memory (RAM)). In embodiments where base station 105 includes a general purpose microprocessor, a computer program product (CPP) 1741 may be provided. CPP 1741 includes a computer readable medium (CRM) 1742 storing a computer program (CP) 1743 comprising computer readable instructions (CRI) 1744. CRM 1742 may be a non-transitory computer readable medium, such as, but not limited, to magnetic media (e.g., a hard disk), optical media (e.g. , a DVD), memory devices (e.g. , random access memory), and the like. In some embodiments, the CRI 1744 of computer program 1743 is configured such that when executed by data processing system 1702, the CRI causes the base station 105 to perform steps described above (e.g. , steps described above with reference to the flow charts). In other embodiments, base station 105 may be configured to perform steps described herein without the need for code. That is, for example, data processing system 1702 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

Some embodiments described above may be summarized in the following manner:

A first embodiment is directed to a method performed by a WCD. The method comprises:

receiving, at the WCD, a message transmitted (e.g., broadcast) by a base station of a RAN; and determining, by the WCD, whether the transmitted message includes information indicating that NAS type requests are supported. As a result of determining that the transmitted message includes information indicating that NAS type requests are supported, the WCD may transmit to the base station a request message (e.g., an R C Connection Request or a GERAN message) comprising information identifying a requested NAS type.

After transmitting the request message to the base station, receiving, at the WCD, a reject message (e.g., an RRC Connection Reject or a GERAN message) transmitted by the base station in response to the request message, the reject message comprising information indicating that the requested NAS type identified in the request message is not supported.

The request message may include information identifying a PLMN, and the reject message may comprise information indicating that the requested NAS type identified in the request message is not supported by the identifying PLMN. The method may further comprise the WCD refraining from transmitting a request message, as a result of determining that the transmitted message does not include information indicating that NAS type requests are supported.

The base station may serve a cell in which the WCD is located, and the method may further comprise the WCD refraining from initiating a connection request in the cell as a result of determining that the transmitted message does not include information indicating that NAS type requests are supported.

Some other embodiments described above may be summarized in the following manner:

One other embodiment is directed to a method performed by a WCD. The method comprises: the WCD transmitting to a base station a request message comprising information identifying a NAS type; receiving, at the WCD, a response message transmitted by the base station in response to the request message, the response message indicating whether or not the requested NAS type is supported. The request message may be an RRC Connection Request message, the response message may be an RRC Connection Setup message, and the method may further comprise: the WCD, in response to receiving the RRC Connection Setup message, determining whether the RRC Connection Setup message includes information indicating that the requested NAS type is supported; and the WCD, as a result of determining that the RRC Connection Setup message includes information indicating that the requested NAS type is supported, transmitting to the base station an RRC Connection Setup Complete message in response to the RRC Connection Setup message.

The request message may be an RRC Connection Request message, the response message may be an RRC Connection Setup message, and the method may further comprise: the WCD, in response to receiving the RRC Connection Setup message, determining whether the RRC Connection Setup message includes information indicating that NAS type requests are supported; and the WCD, as a result of determining that the RRC Connection Setup message does not include information indicating that NAS type requests are supported, refraining from transmitting to the base station an RRC Connection Setup Complete message in response to the RRC Connection Setup message. The response message may be an RRC Connection Reject message transmitted by the base station in response to the request message, the RRC Connection Reject message comprising information indicating that the requested NAS type identified in the request message is not supported. The request message may include information identifying a PLMN, and the RRC Connection Reject message may comprise information indicating that the requested NAS type identified in the request message is not supported by the identifying PLMN. Some other embodiments described above may be summarized in the following manner:

One other embodiment is directed to a method performed by a base station, the method comprising: generating, by the base station, a message comprising system information;

transmitting, by the base station, the message comprising the system information, wherein the system information comprises information indicating that NAS type requests are supported.

The method may further comprise: receiving, at the base station, a request message transmitted by a WCD, the request message comprising information identifying a requested NAS type; in response to receiving the request message, the base station determining whether the identified requested NAS type is supported; and the base station transmitting to the WCD a response message in response to the request message, wherein the content of the response message depends on whether the identified requested NAS type is supported. The response message may comprise information indicating that the identified requested NAS type is not supported if the base station determines that the identified requested NAS type is not supported.

The response message may be an RRC Connection Reject message.

The response message may comprise information indicating that the identified requested NAS type is supported if the base station determines that the identified requested NAS type is supported. The response message may be an RRC Connection Setup message.

Some other embodiments described above may be summarized in the following manner:

One other embodiment is directed to a method performed by a base station, the method comprises: receiving, at the base station, a request message transmitted by a WCD, the request message comprising information identifying a requested NAS type; in response to receiving the request message, the base station determining whether the identified requested NAS type is supported; and the base station transmitting to the WCD a response message in response to the request message, wherein the content of the response message depends on whether the identified requested NAS type is supported.

The response message may comprise information indicating that the identified requested NAS type is not supported if the base station determines that the identified requested NAS type is not supported. The response message may comprise information indicating that the identified requested NAS type is supported if the base station determines that the identified requested NAS type is supported.

While various embodiments of the present disclosure are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is

contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.