The served mobile subscriber can request a different forwarded-to number for each Basic service group containing a basic service to which he has subscribed.

The applicability of this supplementary service is defined in TS 22.004.

A served mobile subscriber is a mobile subscriber of a particular PLMN access who is requesting that calls to his number be forwarded. This subscriber may also be referred to as the forwarding subscriber or the called subscriber. A forwarded-to subscriber is a subscriber to whom the call shall be forwarded.

The supplementary service will be provisioned for all Basic Services subscribed to and to which it is applicable. The service can be offered with several subscription options. Options apply to all Basic service subscribed to. For each subscription option only one value can be selected.

The service will be withdrawn at the subscriber's request or for administrative reasons.

The following information has to be registered in the network:

1. the forwarded-to number, which may be accompanied by a forwarded-to sub-address;
2. information as to whether all calls or all calls of one (or several) specific Basic service group(s) should be forwarded.
   If no Basic Service Code is inserted by the user this is interpreted as All Basic Services.

Registration can take place either by the service provider or with an appropriate control procedure by the subscriber. Verification, where possible, of the forwarded-to number should be accomplished before accepting the call forwarding request. This verification is done by a simple check of the forwarded to number to see if the number is within the allowed number range. When the mobile subscriber so registers call forwarding on mobile subscriber not reachable the network will return notification of acceptance or rejection of the request. This notification will include the forwarded-to number to which call forwarding on mobile subscriber not reachable is registered.

A previous registration can be erased in either of three ways: Firstly, the subscriber can specifically erase a previous registration with an appropriate control procedure. Secondly, the subscriber can register information for call forwarding on mobile subscriber not reachable for the specific Basic service group to another directory number, thus causing the previous registration of call forwarding on mobile subscriber not reachable to be overridden. Thirdly, all information is erased as a result of withdrawal of the service.

The user shall be allowed to activate Call Forwarding on mobile not Reachable (CFNRc) by e.g. using the MMI command described in TS 22.030. This activation request may include information of which Basic Service Group(s) it shall apply to. If no such information is included the Activation applies to all Basic Service Groups against which CFNRc data (forwarded-to-number) is registered. When receiving an activation request the network shall activate CFNRc for the Basic Service Groups comprised in the BS group information given by the user and against which a CFNRc forwarded-to-number is registered. The Activation(s) shall be in accordance with the rules set out in TS 22.004. The user shall receive a notification that CFNRc has been activated. The supplementary service is also activated for a Basic service group as a result of registration for that Basic service group.

An active CFNRc can be deactivated in either of two ways:

• The user may deactivate CFNRc by means of an appropriate control procedure (e.g. as described in TS 22.030). An explicit deactivation request may contain information of which Basic Service Group(s) it shall apply to. If no such information is included the Deactivation applies to all Basic Service Groups.
  When receiving a deactivation request the network shall deactivate CFNRc for the Basic Service Groups comprised in the BS group information given by the user and against which a CFNRc forwarded-to-number is registered. However, the registered information shall not be erased. The Deactivation(s) shall be in accordance with the rules set out in TS 22.004.
  Even if there is no data stored against a particular Basic Service group comprised in deactivation request, the request shall be accepted by the network for the other Basic Service groups included in the information given by the user.
• The service is deactivated as a result of Erasure.
  In the former case, and also in the latter if Erasure is user controlled, the user shall receive a notification of whether her request was accepted or rejected in accordance with the rules set out in TS 22.004.

If the supplementary service is activated for a Basic service incoming calls for the specified Basic service when the mobile subscriber is not reachable, will be forwarded by network invocation.

When call forwarding on mobile subscriber not reachable is active and operative, all incoming calls for the specified Basic Service(s) when the mobile subscriber is not reachable, will be forwarded without being offered to the served mobile subscriber. The forwarded-to subscriber will receive an indication that the call has been forwarded with the cause. The cause, when available, will be the appropriate forwarding condition. Depending on the value of the served subscribers subscription option, the forwarded-to subscriber may also receive the MSISDN of the served subscriber. When multiple forwarding occurs the reason for forwarding and the MSISDN given to the forwarded-to subscriber should relate to the last forwarding subscriber in the chain. When call forwarding on mobile subscriber not reachable is active and operative, the ability of the served mobile subscriber to originate calls is principally not affected, but practically it is affected if the mobile subscriber is de-registered, on radio congestion or on no paging response. However, an indication that the call forwarding service is currently active and operative on a number will be given to the forwarding party each time an outgoing call is made. As a subscription option, the served mobile subscriber can request that the calling subscriber receives a notification that the call has been forwarded.

Data request The data request procedure enables the mobile subscriber to obtain information about the data stored in the PLMN. After having requested this procedure the network shall return the following information:

• in response to a general data request the served mobile subscriber should be given a list of all Basic service groups to which call forwarding on mobile subscriber not reachable is registered, including information whether it is active and if so, whether it is operative or quiescent, and the associated forwarded-to numbers;
• in response to a specific request concerning one particular Basic service group, the served mobile subscriber should be informed whether or not call forwarding on mobile subscriber not reachable is registered, including information whether it is active and if so, whether it is operative or quiescent for that Basic service group. If CFNRc is registered, the associated forwarded-to number shall be given.

The forwarding subscriber may be charged for the forwarded part of the call.

If the system cannot accept a registration request, the served mobile subscriber should receive a notification that call forwarding on mobile subscriber not reachable registration was not successful. Possible causes are:

• service not subscribed to;
• forwarded-to number is invalid directory number;
• use of an operator access prefix;
• insufficient information;
• forwarded-to number is a special service code (e.g. police);
• forwarded-to number is the directory number of the mobile subscriber herself;
• conflicting situation with other supplementary services (e.g. incoming call barring has been activated);
• no basic service provisioned within the basic service group(s).

The network is not required to validate information related to the forwarded-to number.

If the network cannot accept a mobile subscriber's request for erasure, cause will be returned to the subscriber, such as:

• insufficient information;
• inconsistent with registration.

If the subscriber does not completely specify which call forwarding on mobile subscriber not reachable request is to be erased, the network will reject the erasure request with appropriate cause. If no Basic Service Code is inserted by the user, CF will be erased from all Basic Services.

If there is no CFNRc forwarded-to-number registered against a Basic Service group, the activation request for that Basic Service group shall be denied. Examples of causes for a not accepted activation request:

• service not provisioned;
• conflicting situation with other supplementary services;
• service not registered.

If the network cannot accept a deactivation request, an appropriate cause will be returned to the user, e.g. Service not Active.

Within a PLMN or different PLMNs the number of tandem forwarding connections should be limited. The maximum number of tandem forwarding connections should be limited to a value between 1 and 5. This is to prevent infinite looping. If the limit of successive forwardings of a call has already been reached, an unsuccessful call set up indication is sent backwards. If the forwarded call cannot be completed to the forwarded-to destination, then the network will clear the forwarded part of the call and an unsuccessful call set up indication is sent backwards.