7 Management functionality

3GPP43.318Generic Access Network (GAN)Release 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

7.1 State diagram for Generic Access

Figure 8: State diagram for Generic Access in the MS

Notes:

1) The following cases are possible when switching the serving RR to GAN Iu mode:

a) Transition to GA-RRC-IDLE for both CS and PS domains (i.e., idle mode transition from GERAN/UTRAN/E-UTRAN)

b) Transition to GA-RRC-IDLE (PS domain) and GA-RRC-CONNECTED (CS domain) (i.e., due to CS handover from GERAN/UTRAN)

c) Transition to GA-RRC-IDLE (CS domain) and GA-RRC-CONNECTED (PS domain) (i.e., due to PS handover from GERAN/UTRAN)

d) Transition to GA-RRC-CONNECTED (CS domain) and GA-RRC-CONNECTED (PS domain) (i.e., due to combined CS handover and PS handover from GERAN/UTRAN)

2) The following cases are possible when switching the serving RR from GAN Iu mode:

e) Transition from GA-RRC-IDLE for both CS and PS domains (i.e., idle mode transition to GERAN/UTRAN/E-UTRAN)

f) Transition from GA-RRC-IDLE (PS domain) and GA-RRC-CONNECTED (CS domain) (i.e., due to CS handover to GERAN/UTRAN).

g) Transition from GA-RRC-IDLE (CS domain) and GA-RRC-CONNECTED (PS domain) (i.e., due to PS handover to GERAN/UTRAN)

h) Transition from GA-RRC-CONNECTED (CS domain) and GA-RRC-CONNECTED (PS domain) (i.e., due to combined CS handover and PS handover to GERAN/UTRAN)

3) There is no requirement for the MS to support both GAN Iu mode and GAN A/Gb mode.

7.2 GA-RC (Generic Access Resource Control)

7.2.1 General

The GA-RC protocol provides a resource management layer, with the following functions:

– discovery and Registration with GANC, including GAN mode selection (GAN A/Gb mode or GAN Iu mode);

– registration Update with GANC;

– application level keep-alive with GANC; and

– support for identification of the AP being used for GAN access.

7.2.2 States of the GA-RC sub-layer

The GA-RC sub-layer in the MS can be in one of two states – GA-RC-DEREGISTERED or GA-RC-REGISTERED – as illustrated in figure 8.

In the GA-RC-DEREGISTERED state, the MS may be in a GAN coverage area; however, the MS has not registered successfully with the GANC and cannot exchange GA-CSR and GA-PSR signalling messages (GAN A/Gb mode) or GA-RRC messages (GAN Iu mode) with the GANC. The MS may initiate the GAN Registration procedure when in the GA-RC-DEREGISTERED state. The MS returns to GA-RC-DEREGISTERED state on loss of TCP or IPsec connection.

In the GAN A/Gb mode GA-RC-REGISTERED state, the MS is registered with a GANC, has an IPsec and an TCP connection established to the Serving GANC, through which the MS may exchange GA-CSR or GA-PSR signaling messages with the GANC, and the SAP between the GA-CSR and MM entity and the GA-PSR and the GMM entity are not active. In the GA-RC-REGISTERED state, the MS may be camped on GERAN or UTRAN, active in GERAN or UTRAN (e.g. a GSM RR or a UTRAN RRC connection may be established) or may have no GERAN or UTRAN service while still maintaining the registration in the GAN.

In the GAN Iu mode GA-RC-REGISTERED state, the MS is registered with the Serving GANC. The MS has an IPsec tunnel and a TCP connection established to the Serving GANC through which the MS may exchange GA-RC or GA-RRC signaling messages with the GANC. The SAP between the GA-RRC and MM entity and the GA-RRC and the GMM entity are not active. In the GA-RC-REGISTERED state, the MS may be camped on GERAN or UTRAN, active in GERAN or UTRAN (e.g. a GSM RR or a UTRAN RRC connection may be established) or may have no GERAN or UTRAN service while still maintaining the registration in the GAN.

7.3 GA-CSR (Generic Access Circuit Switched Resources)

7.3.1 General

The GA-CSR protocol provides a resource management layer, which is equivalent to the GSM-RR and provides the following functions:

– setup of bearer for CS traffic between the MS and GANC;

– handover support between GERAN and GAN; and

– functions such as GPRS suspension, paging, ciphering configuration, classmark change.

7.3.2 States of the GA-CSR sub-layer

The GA-CSR sub-layer in the MS can be in two states -GA-CSR-IDLE or GA-CSR-DEDICATED as illustrated in figure 8.

The MS enters GA-CSR-IDLE state from GA-RC-REGISTERED state, when the MS switches the serving RR entity to GA-CSR and the SAP between the MM and the GA-CSR is activated. Simultaneously, the GA-PSR acquires the control of the RLC GRR and GMMRR SAPs and transitions to GA-PSR- STANDBY state. While the MS remains in GAN A/Gb mode it performs registration Update and application level keep-alive with the GANC as per the GA-RC-REGISTERED state.

The MS moves from the GA-CSR-IDLE state to the GA-CSR-DEDICATED state when the GA-CSR connection is established and returns to GA-CSR-IDLE state when the GA-CSR connection is released. Upon GA-CSR connection release an indication that no dedicated resources exist is passed to the upper layers.

The MS may also enter GA-CSR-DEDICATED state from GA-RC-REGISTERED state of GERAN/UTRAN mode when Handover to GAN is being performed. In the same way, the MS enters GA-RC-REGISTERED state of GERAN/UTRAN mode from GA-CSR-DEDICATED when Handover from GAN is being performed.

7.4 GA-PSR (Generic Access Packet Switched Resources)

The GA-PSR protocol provides the following services:

– delivery of GPRS signalling, SMS messages over the secure tunnel;

– paging, flow control, GPRS transport channel management;

– PS handover support between GERAN/UTRAN mode and GAN A/Gb mode; and

– transfer of GPRS user plane data.

The GA-PSR Transport Channel (GA-PSR TC) provides the association between the MS and GANC for the transport of GPRS user data over the Up interface. Given that the GAN user data transport is UDP based, the GA-PSR Transport Channel is associated with corresponding MS and GANC IP addresses and UDP ports used for GPRS user data transfer. The MS and GANC manage the GA-PSR Transport Channel based on the requests for data transfer and the configurable GA-PSR Channel Timer.

7.4.1 States of the GA-PSR sub-layer

The GA-PSR sub-layer in the MS can be in two states – GA-PSR-STANDBY or GA-PSR-ACTIVE – as illustrated in figure 8.

– GA-PSR-STANDBY: This is the initial/default state of the mobile station in GAN A/Gb mode. The MS is not able to send or receive GPRS user data to and from the GANC. The GA-PSR Transport Channel does not exist when the MS is in GA-PSR-STANDBY state. The GANC or the MS needs to activate the GA-PSR Transport Channel before sending any GPRS user data. When the MS GA-PSR successfully establishes a GA-PSR Transport Channel, it transitions to the GA-PSR-ACTIVE state.

– GA-PSR-ACTIVE: The MS is able to send and receive GPRS user data to and from the GANC. The corresponding GA-PSR Transport Channel exists.

Upon a successful switch to GAN A/Gb mode as a result of rove-in, the MS GA-PSR acquires the control of the RLC GRR and GMMRR SAPs, and transitions to GA-PSR-STANDBY state and GA-PSR TC activation may then be triggered.

After successful GA-PSR TC activation when in GAN A/Gb mode, the MS GA-PSR transitions to GA-PSR-ACTIVE state. The following are the possible triggers for GA-PSR TC activation when the MS is in the GA-PSR-STANDBY state in GAN A/Gb mode:

– The MS LLC entity initiates the uplink data transfer using LLC SAPI 3, 5, 9 or 11 and the GA-PSR sub-layer is in the GA-PSR-STANDBY state.

– The GANC initiates GA-PSR TC activation; i.e. the MS receives a GA-PSR-ACTIVATE UTC REQ message from the GANC (see sub-clause 8.16.4).

As described in 3GPP TS 43.129 [44], the MS and GANC establish a GA-PSR TC during the PS handover preparation phase which results in MS enabling the reception of downlink LLC PDUs. Upon a successful switch to GAN A/Gb mode as a result of receiving the PS Handover Command, the MS transitions to GA-PSR-ACTIVE state, the MS GA-PSR acquires the control of the RLC GRR and GMMRR SAPs and enables the transmission of uplink LLC PDUs on the allocated GA-PSR TC.

Upon the successful GA-PSR TC activation and in parallel with transition to GA-PSR-ACTIVE state, the MS GA-PSR starts the GA-PSR Channel Timer. When the GA-PSR Channel Timer expires, the MS sends a message to the GANC to initiate GA-PSR TC deactivation. Upon successful GA-PSR TC deactivation, the MS GA-PSR transitions to GA-PSR-STANDBY state.

At any time, while in GAN A/Gb mode, if the serving RR entity is switched to GERAN-RR, UTRAN RRC or E-UTRAN RRC, the GA-PSR is disconnected from GPRS SAPs and the MS enters GERAN/UTRAN/E-UTRAN mode. Simultaneously, the MS will release the associated GA-PSR TC regardless of the GA-PSR Channel Timer status.

The MS GA-PSR maintains one GA-PSR TC for all active user data flows; i.e. if the GA-PSR is in GA-PSR-ACTIVE state, any uplink user data packet is transferred using the active GA-PSR TC regardless of the associated PFC and LLC SAP. The GA-PSR Channel Timer is restarted whenever any uplink user data packet is sent or downlink user data packet received regardless of the associated PFC and LLC SAP.

7.4a GA-RRC

7.4a.1 General

The GA-RRC protocol provides a resource management layer which is equivalent to UTRAN-RRC and supports the following functions:

– setup of transport channels for CS and PS traffic between the MS and GANC;

– CS and PS handover support between GERAN/UTRAN and GAN;

– direct transfer of NAS messages between the MS and the core network; and

– other functions such as CS and PS paging and security configuration.

7.4a.2 States of the GA-RRC sub-layer

The GA-RRC sub-layer in the MS contains two entities, the CS domain GA-RRC sublayer entity and the PS domain GA-RRC sublayer entity (as illustrated in Figure 8). These entities operate independently and in parallel; e.g., two GA-RRC connections are established in the case of simultaneous CS and PS services, one GA-RRC connection for each domain.

Each GA-RRC sub-layer entity in the MS can be in one of two states, GA-RRC-IDLE or GA-RRC-CONNECTED as illustrated in figure 8.

Both the CS GA-RRC sub-layer entity and the PS GA-RRC sublayer entity in the MS enters the GA-RRC-IDLE state when the MS switches the serving RR entity to GA-RRC and the SAP between the NAS and the GA-RRC is activated. This switch may occur only when the GA-RC is in the GA-RC-REGISTERED state.

The CS/PS GA-RRC sublayer entity in the MS moves from the GA-RRC-IDLE state to the GA-RRC-CONNECTED state when the CS/PS GA-RRC connection is established and returns to the GA-RRC-IDLE state when the CS/PS GA-RRC connection is released. Upon CS/PS GA-RRC connection release, an indication that no dedicated resources exist for the domain is passed to the upper layers.

The CS/PS GA-RRC sublayer entity in the MS may also enter the GA-RRC-CONNECTED state while in the GA-RC-REGISTERED state in GERAN/UTRAN mode when CS/PS handover to GAN is being performed.

7.5 Security Mechanisms

GAN supports security mechanisms at different levels and interfaces as depicted in figure 9.

Figure 9: GAN Security Mechanisms

1. The security mechanisms over the Up interface protect signalling, voice and data traffic flows between the MS and the GANC from unauthorized use, data manipulation and eavesdropping; i.e. authentication, encryption and data integrity mechanisms are supported.

2. Authentication of the subscriber by the core network occurs between the MSC/VLR or SGSN and the MS and is transparent to the GANC – however, there is a cryptographic binding between the MS-CN authentication and the MS-GANC authentication to prevent man in the middle attacks. GPRS ciphering is the standard LLC layer ciphering that operates between the MS and the SGSN (not applicable to GAN Iu mode). These mechanisms are out of scope of the present document.

3. Additional application level security mechanisms may be employed in the PS domain to secure the end-to-end communication between the MS and the application server. For example, the MS may run the HTTP protocol over an SSL session for secure web access. These mechanisms are out of scope of the present document.

All signalling traffic and user-plane traffic sent between MS and GANC over the Up interface is protected by an IPsec tunnel between the MS and GANC-SEGW, that provides mutual authentication (using SIM credentials), encryption and data integrity using similar mechanisms as specified in 3GPP TS 33.234 [9]. The exact mechanisms for the purposes of the current specification are defined in Annex A.