4 General

04.933GPPCompletion of Calls to Busy Subscriber (CCBS)Stage 3TS

4.1 Overview

CCBS allows a calling subscriber A, encountering a Network Determined User Busy (NDUB) called destination B, to be notified when destination B is idle and to have the network reinitiate the call to destination B, if subscriber A desires.

All of the radio signalling specific to CCBS is at the subscriber A-side. Each procedure is described in turn. There is no radio signalling specific to CCBS at destination B-side. The radio signalling on the destination B-side uses basic call signalling procedures only.

A mobile station that supports CCBS shall support the requirements of the following options used in GSM 04.08:

1) Prolonged Clearing Procedure;

2) Network Initiated Mobile Originated Connection Management (MO CM) Connection Request;

3) Network initiated MO call.

A network supporting CCBS shall support the requirements of the following options used in GSM 04.08:

1) CCBS Request activation; and

2) Network initiated MO call.

4.2 Activation

When CCBS is allowed the network shall give subscriber A the option of activating a CCBS Request.

The network shall send a DISCONNECT message to MS A (cause #17 (User Busy) or cause #34 (no circuit / channel available)) with diagnostic field indicating CCBS is Possible and allowed actions indicating CCBS is Possible. The network starts the retention timer T1 when it sends the DISCONNECT message. The MS shall not release the connection with the network if allowed actions is present.

If subscriber A attempts to activate a CCBS Request, MS A shall send a RELEASE message, with the Facility information element indicating CCBSRequest and the network shall stop T1. If the subscriber A does not accept CCBS activation, the MS shall send normal RELEASE message and the network shall stop T1 and continue normal call clearing. If the timer T1 expires before the RELEASE message is received from the MS, the network shall continue normal call clearing.

If the network accepts the activation attempt, it shall acknowledge it by sending a RELEASE COMPLETE message containing the Facility information element with the CCBS index and optionally the AddressOfB, SubAddressOfB and the BasicServiceCode. If the network rejects the activation attempt, it shall send a RELEASE COMPLETE message containing the Facility information element with a return error indication.

If a TCH has been allocated for the initial call and there are no further need for this channel configuration, the network may reconfigure the ongoing connection from TCH(s) mode to SDCCH only mode while waiting for further user input activity.

It is a network option to maintain the ongoing connection in TCH mode while waiting for further user input activity.

SS Version Indicator value 3 or above has to be used.

MS A NETWORK
SETUP (Note 1)
——————————————————————————————————————————->
(Bearer capability, CC capabilities, Called party BCD number)

DISCONNECT (Note 2)
<——————————————————————————————————————————
((Cause #17 (User Busy) / Cause #34 (no circuit/channel available)), diagnostic = CCBSPossible,
allowed actions = CCBS Possible)

RELEASE (Note 3)
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

RELEASE (Note 4)
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
((Cause #17 (User Busy) / Cause #34 (no circuit/channel available) ) /
Cause #102 (recovery on timer expiry))

RELEASE COMPLETE
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

RELEASE
———————————————————————————————————————————>
Facility (Invoke = AccessRegisterCCEntry)

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result (CCBS Index, AddressOfB, Sub_AddressOfB, BasicServiceCode)) (Note 5)

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error = (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject = (Invoke Problem))

NOTE 1: The original call set-up is shown for completeness.

NOTE 2: The CCBS activation is possible only when allowed actions field contains CCBS Possible indication

NOTE 3: If Subscriber A rejects the CCBS Possible indication, then the MS shall send RELEASE.

NOTE 4: If T1 (Retention timer) expires then the network shall send a RELEASE message to the MS. The Timer expiry cause may be included.

NOTE 5: AddressOfB, Sub_AddressOfB and BasicServiceCode are optional parameters.

Figure 4.2: Activation of a CCBS Request for supporting MSs

4.3 CCBS Recall and CCBS Call Set-up

When destination B becomes free the network shall offer subscriber A the option of recalling destination B.

The network shall prompt MS A to allocate a Transaction Identifier (TI) and establish the CC connection by sending a CM SERVICE PROMPT message. MS A establishes the CC connection by sending a START CC message to the network. The network shall then send a CC ESTABLISHMENT message to MS A and shall include the Setup container. The Setup container contains information necessary to set-up the CCBS Call. The MS can modify the Bearer Capability (BC), High Level Compatibility (HLC) and Low Level Compatibility (LLC) information within the Setup container provided that the same Basic Service Group is maintained. If MS A is compatible with the basic service group it sends CC ESTABLISHMENT CONFIRMED message to the network. Once the network has received the CC ESTABLISHMENT CONFIRMED message it shall send a RECALL message to MS A, which contains information to be presented to the subscriber. At this stage, if the MS detects that ACM  ACMmax, the MS shall interrupt the recall procedure, shall not alert the user and shall send a RELEASE COMPLETE message with the appropriate cause value to the network. If subscriber A accepts the CCBS recall, MS A shall establish a new call with the SETUP message. MSC A shall maintain the RR connection with MS A throughout the time when acceptance of the CCBS Recall is possible. Once the SETUP message is received, normal call handling continues.

4.3.1 CCBS Call Set-up (MS A idle)

Figure 4.3.1 shows the case where MS A is idle when a CCBS Recall is received by the originating network. The different possibilities for allocating a traffic channel are described in GSM 04.08.

MS A NETWORK
RR CONNECTION ESTABLISHED
<——————————————————————————————————————————–>

CM SERVICE PROMPT
<———————————————————————————————————————————-

START CC
———————————————————————————————————————————>

MM_STATUS
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #32 (Service option not supported) / Cause #34 (Service option temporarily out of order) /
Cause #97 (message type non-existent or not implemented))

CC ESTABLISHMENT
<———————————————————————————————————————————-
(Setup container)

CC ESTABLISHMENT CONFIRMED
———————————————————————————————————————————>
(BC’(s)), (Note 1)

RELEASE COMPLETE
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #29 (facility rejected) / Cause #88 (incompatible destination) / Cause #17 ( User Busy)) (Note 2)

RECALL
<———————————————————————————————————————————-
Facility (Invoke = NotifySS (SS-Code = CCBS, CCBS index, AddressOfB, Sub_AddressOfB, BasicServiceCode,
Alerting Pattern)) (Note 3)

RELEASE COMPLETE
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #21 (call rejected) / Cause #17 (User Busy) / Cause #68 (ACM  ACMmax)) (Note 4)

RELEASE COMPLETE
< – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
(Cause #102 (recovery on timer expiry)) (Note 5)

SETUP
———————————————————————————————————————————->
(Note 6)

NOTE 1: The BC may be modified by the MS as long as the same Basic Service Group is maintained.

NOTE 2: The MS releases the transaction if the BC,HLC,LLC received in the CC ESTABLISHMENT message are incompatible with the MS, the MS cannot decode the contents of the "advanced recall alignment" Facility information element correctly (see GSM 04.10) or the MS responds by indicating UDUB.

NOTE 3: MS shall start CCBS Recall alerting on receiving the RECALL message. The CCBS timer T4 is started when the RECALL message is sent to the MS. Sub_Address information may be included. The Alerting Pattern parameter may be included by the network to give some indication about alerting (category or level). If supported in the MS, this optional parameter is to be used by the MS as specified in GSM 02.07.

NOTE 4: Subscriber A explicitly rejects the CCBS Recall or subscriber A responds to the CCBS Recall by indicating UDUB or ACM  ACMmax.

NOTE 5: The network releases the transaction if CCBS timer T4 expires.

NOTE 6: The information elements within the SETUP message are derived from the Setup container in the CC ESTABLISHMENT Message. The SETUP message must contain the same BC(s) that was (were) sent to the network in the CC ESTABLISHMENT CONFIRMED message.

Figure 4.3.1: CCBS Call Set-up for supporting MSs – subscriber A idle when RECALL arrives

4.3.2 CCBS Call Set-up (MS A not idle)

If a CCBS Recall is offered to MS A and MS A is not idle, subscriber A may accept the CCBS Recall and either release the existing call or put the existing call on hold.

4.3.2.1 Existing call released

MS A NETWORK
CM SERVICE PROMPT
<———————————————————————————————————————————-

START CC (TI = CCBS call) (Note 1)
———————————————————————————————————————————->

MM_STATUS
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #32 (Service option not supported) / Cause #34 (Service option temporarily out of order) /
Cause #97 (message type non-existent or not implemented))

CC ESTABLISHMENT (TI = CCBS call)
<———————————————————————————————————————————-
(Setup container)

CC ESTABLISHMENT CONFIRMED (TI = CCBS call)
———————————————————————————————————————————>
(BC’(s), Cause #17 ( User Busy)) (Note 2)

RELEASE COMPLETE (TI = CCBS call)
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #29 (facility rejected) / Cause #88 (incompatible destination) / Cause #17 (User Busy)) (Note 3)

RECALL (TI = CCBS call)
<————————————————————————————————————————————-
Facility (Invoke = NotifySS (SS-Code = CCBS, CCBS index, AddressOfB, Sub_AddressOfB, BasicServiceCode,
Alerting Pattern)) (Note 4)

RELEASE COMPLETE (TI = CCBS call)
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #21 (call rejected) / Cause #17 (User Busy) / Cause #68 (ACM  ACMmax)) (Note 5)

RELEASE COMPLETE (TI = CCBS call)
< – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
(Cause #102 (recovery on timer expiry)) (Note 6)

DISCONNECT (TI = existing call)
———————————————————————————————————————————->
(Cause #16 (normal clearing)) (Note 1, Note 7)

SETUP (TI = CCBS call)
———————————————————————————————————————————->
(Note 8)

Figure 4.3.2: CCBS Recall arrives while MS involved in a call, the existing call is released on acceptance of the CCBS Recall

Notes to figure 4.3.2:

NOTE 1: A new TI value indicated by "TI = CCBS call" is allocated by the MS for the subsequent CCBS call. The already existing call is referred to by the TI value "TI = existing call".

NOTE 2: The BC may be modified by the MS as long as the same Basic Service Group is maintained. The MS shall indicate "User Busy" if it is not idle.

NOTE 3: The MS releases the transaction if the BC,HLC,LLC received in the CC ESTABLISHMENT message are incompatible with the MS, the MS cannot decode the contents of the "advanced recall alignment" Facility information element correctly (see GSM 04.10) or the MS responds by indicating UDUB.

NOTE 4: MS shall start CCBS Recall alerting on receiving the RECALL message. The CCBS timer T10 is started when the RECALL message is sent to the MS. Sub_Address information may be included. The Alerting Pattern parameter may be included by the network to give some indication about alerting (category or level). If supported in the MS, this optional parameter is to be used by the MS as specified in GSM 02.07.

NOTE 5: Subscriber A explicitly rejects the CCBS Recall or subscriber A responds to the CCBS Recall by indicating UDUB or ACM  ACMmax.

NOTE 6: The network releases the transaction if CCBS timer T10 expires.

NOTE 7: The existing call is released to make resources available for the CCBS call. The existing call is released according to normal call clearing procedures (see GSM 04.08).

NOTE 8: The information elements within the SETUP message are derived from the Setup container in the CC ESTABLISHMENT message. The SETUP message must contain the same BC(s) that was (were) sent to the network in the CC ESTABLISHMENT CONFIRMED message.

4.3.2.2 Existing call placed on hold

If the existing call is a telephony call, subscriber A may place this call on hold in order to accept the CCBS Recall.

MS A NETWORK

CM SERVICE PROMPT
<———————————————————————————————————————————-

START CC (TI = CCBS call) (Note 1)
———————————————————————————————————————————->

MM_STATUS
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #32 (Service option not supported) / Cause #34 (Service option temporarily out of order) /
Cause #97 (message type non-existent or not implemented))

CC ESTABLISHMENT(TI = CCBS call)
<———————————————————————————————————————————-
(Setup container)

CC ESTABLISHMENT CONFIRMED (TI = CCBS call)
———————————————————————————————————————————>
(BC’(s), Cause #17 ( User Busy)) (Note 2)

RELEASE COMPLETE (TI = CCBS call)
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – >
(Cause #29 (facility rejected) / Cause #88 (incompatible destination) / Cause #17 (User Busy)) (Note 3)

RECALL (TI = CCBS call)
<————————————————————————————————————————————-
Facility (Invoke = NotifySS (SS-Code = CCBS, CCBS index, AddressOfB, Sub_AddressOfB, BasicServiceCode,
Alerting Pattern)) (Note 4)

RELEASE COMPLETE (TI = CCBS call)
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->
(Cause #21 (call rejected) / Cause #17 (UDUB) / Cause #68 (ACM  ACMmax)) (Note 5)

RELEASE COMPLETE (TI = CCBS call)
< – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – —
(Cause #102 (recovery on timer expiry)) (Note 6)

HOLD (TI = existing call) (Note 1, Note 7)
———————————————————————————————————————————->

HOLD ACKNOWLEDGE (TI = existing call)
<———————————————————————————————————————————-

SETUP (TI = CCBS call) (Note 8)
———————————————————————————————————————————->

Figure 4.3.3: CCBS Recall arrives while MS involved in a call, the existing call is placed on hold on acceptance of the CCBS Recall

Notes to figure 4.3.3:

NOTE 1: A new TI value indicated by "TI = CCBS call" is allocated by the MS for the subsequent CCBS call. The already existing call is referred to by the TI value "TI = existing call".

NOTE 2: The BC may be modified by the MS as long as the same Basic Service Group is maintained. The MS shall indicate "User Busy" if it is not idle.

NOTE 3: The MS releases the transaction if the BC,HLC,LLC received in the CC ESTABLISHMENT message are incompatible with the MS, the MS cannot decode the contents of the "advanced recall alignment" Facility information element correctly, or the MS responds by indicating UDUB.

NOTE 4: MS shall start CCBS Recall alerting on receiving the RECALL message. The CCBS timer T10 is started when the RECALL message is sent to the MS. Sub_Address information may be included. The Alerting Pattern parameter may be included by the network to give some indication about alerting (category or level). If supported in the MS, this optional parameter is to be used by the MS as specified in GSM 02.07.

NOTE 5: Subscriber A explicitly rejects the CCBS Recall or subscriber A responds to the CCBS Recall by indicating UDUB or ACM  ACMmax.

NOTE 6: The network releases the transaction if CCBS timer T10 expires.

NOTE 7: The existing call is placed on hold to make resources available for the CCBS call. The existing call is placed on hold according to normal call hold procedures (see GSM 04.83).

NOTE 8: The information elements within the SETUP message derived from the Setup container in the CC ESTABLISHMENT Message. The SETUP message must contain the same BC(s) that was (were) sent to the network in the CC ESTABLISHMENT CONFIRMED message.

4.4 Deactivation

Subscriber A can perform the following operations:

– deactivate all outstanding CCBS requests;

– deactivate a specific CCBS request.

MS A shall send a REGISTER message, with the Facility information element, indicating EraseCCEntry.

SS Version Indicator value 3 or above has to be used.

MS A NETWORK
REGISTER
——————————————————————————————————————————–>
Facility (Invoke = EraseCCEntry (CCBS))

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result)

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject (Invoke_Problem))

Figure 4.4.1: Deactivation of all CCBS requests

MS A NETWORK
REGISTER
——————————————————————————————————————————–>
Facility (Invoke = EraseCCEntry (CCBS, CCBS Index))

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result)

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject (Invoke_Problem))

Figure 4.4.2: Deactivation of a specific CCBS request

4.5 Interrogation

Subscriber A can perform an interrogation of the CCBS service, with the three possible outcomes:

– the CCBS service is not provisioned for the subscriber;

– the CCBS service is provisioned for the subscriber, but the queue of requests is empty;

– the CCBS service is provisioned for the subscriber and there are requests in the queue.

MS A shall send a REGISTER message, with the Facility information element, indicating InterrogateSS. SS Version Indicator value 2 or above has to be used. Depending on the outcome of the interrogation, the network shall return:

a) SS-status set to not provisioned when the CCBS service is not provisioned (figure 4.5.1);

b) SS status set to provisioned when the CCBS service is provisioned, but there are no outstanding requests (figure 4.5.2);

c) SS-status set to provisioned and the list of outstanding CCBS requests in the queue (figure 4.5.3).

For each request in the queue, the following data shall be returned:

– CCBS index;

– Address of B;

– Sub-Address of B (optional);

– Basic Service Code.

MS A NETWORK
REGISTER
———————————————————————————————————————————>
Facility (Invoke = InterrogateSS (CCBS))

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result = InterrogateSS (SS-status))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject (Invoke_Problem))

Figure 4.5.1: Interrogation of the CCBS – service not provisioned

MS A NETWORK
REGISTER
———————————————————————————————————————————>
Facility (Invoke = InterrogateSS (CCBS))

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result = InterrogateSS (SS-status))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject (Invoke_Problem))

Figure 4.5.2: Interrogation of the CCBS – the request queue is empty

MS A NETWORK
REGISTER
———————————————————————————————————————————>
Facility (Invoke = InterrogateSS(CCBS))

RELEASE COMPLETE
<——————————————————————————————————————————–
Facility (Return Result = InterrogateSS (SS-status, CCBS index, AddressOfB, Sub-AddressOfB, BasicServiceCode)) (Note)

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Reject (Invoke_Problem))

NOTE: The information for up to five CCBS Requests can be included.

Figure 4.5.3: Interrogation of the CCBS – all existing requests

Annex A (informative):
Operation for Non-Supporting MS’s