Within the 3GPP specifications the CS video call is regarded as a Bearer Service and not a Teleservice. Annex A of TS 22.004 defines the applicability of supplementary services to both "Telephony" (a Teleservice) and "cct data" (Bearer Services). Most supplementary services are applicable to both the voice and video calls. For this 'redial' solution to function effectively, the user and operator needs to configure supplementary services and network features (such as ODB and Roaming Restrictions) in a sensible manner (e.g. avoid barring voice calls but permit video calls). Sensible configurations do not seem to be prohibited by the standard. It is worth noting that some supplementary services cannot be used while in the video component of a call (e.g. Call Hold; Multiparty; Explicit Call Transfer and Calling Name Presentation).

To make this feature work smoothly, CLIs should not be restricted by the user, and, CLIs should be transferred by the networks. In addition, single numbering schemes should be used (i.e. the user's videophone and telephone numbers need to be the same). When detecting that a redialled call is the same as the original, the terminating UE should be aware that the number format might change from, for example, national to international format. This could be because the networks route the voice and video calls differently, or, because the terminating UE was the original A party. The impacts of CAMEL based number translation services, e.g. for office VPNs are for further study.

Release of the call can trigger other services, for example, voice mail delivery attempts and/or Call Completion to a Busy Subscriber. These services should have been designed to permit customers to make 'one call followed by another', however, increased usage of closely coupled calls might mean that these other services need re-tuning.

When initiating a video call, the terminating network might provide "multi-media" content to the A party while attempting to contact the B party. In order to achieve this, a bi-directional user plane is needed between the A party and the terminating network, i.e., the Connect message must have been sent. In this situation, the original video call establishment has been successful, and, as such, there is no need to "redial as a voice call". How the terminating network transfers the established video call to the "real B party" is a matter for the terminating network (e.g. with regard to H.324 codec negotiation matters).

With this redial mechanism, the voice and video calls are totally separate. Hence each should be able to use the existing CDR and billing machinery without modification. However, it is worth noting that the billing system will probably not be able to provide any correlation between video and voice components of the same call. The easy ability to switch between voice and video calls may have an impact on, for example, calculations of 'mean call holding time' if this is calculated from CDRs. As a consequence there may be a need to add extra information onto the CDRs to indicate the reason for release/reason for establishment of a call. In particular, it would be valuable to know the proportion of redial attempts that were successful. The addition of "reason for establishment" requires extra TS 24.008 signalling from the mobile. It is recommended that such changes to the TS 24.008 signalling should be made in this release of the specification. An MSC generates call statistics information from its locally available release information. Some of the abnormal releases on the B party side may be seen only as normal releases on the A party side as some problems of B party side are not signalled between MSCs. Therefore, the probability of the different B party problems has to be taken into account when the statistics for A party side is evaluated. An MSC may collect call statistics information from video calls for:

• unsuccessful mobile originating video call setup because 64 kbit/s RAB is currently not available;
• unsuccessful mobile terminating video call setup because 64 kbit/s RAB is currently not available;
• unsuccessful mobile originating video call setup because of lack of video service support by the UE;
• unsuccessful mobile terminating video call setup because of lack of video service support by the network;
• unsuccessful mobile originating video call setup because UE or network do not support video call;
• disrupted video calls because of loss of the radio connection;

and, if TS 24.008 is upgraded, the MSC can collect statistics for:

• the number of mobile originating video call attempts indicating redial;
• the number of mobile originating voice call attempts indicating redial.

Additionally, it is recommended that a "redial flag" is an optional parameter in the CDR produced for Mobile Originated calls as specified in TS 32.205.

With this redial mechanism, the voice and video calls are totally separate. Hence each should be able to use the existing pre-pay mechanisms without modification.

With this redial mechanism, each call will be subject to its own tariffs. If 'per second' charging is in operation this should not matter. However if "per minute" billing is used, a customer might be slightly disappointed with the charge raised following 20 seconds of voice communication and 40 seconds of video communication.

With this redial mechanism, the voice and video calls are totally separate. Hence there should be no impact on existing inter-operator agreements for either voice or for video calls.

With this redial mechanism, the voice and video calls are totally separate. Hence there should be no impact on existing roaming agreements for either voice or for video calls.

The functionality that is described in this TR is based on the R'99 core specifications, plus, some additional CRs already agreed in later releases, plus, some CRs that have yet to be drafted and/or agreed by TSG Plenaries.

These CRs are believed to include (and believed to be limited to):

1. From release 6, CR 287r3 to TS 44.018 (see GP-040518) and CR 198r4 to TS 45.008 (see GP-040542). These are the CRs that permit the BSC to "release the mobile and ask the mobile to camp on 3G" (re: clause 4.2.1, step 5).
2. From release 6, CR 133 to TS 48.008 (see GP-041421). This CR relates to "Service handover for services not supported in GERAN" (re: to clause 4.2.1, step 8 and clause 4.4.1, step 2).

The drafting of the following CRs is believed to be useful:

1. To TS 24.008, a CR for the inclusion of "redial attempt" information in the Setup messages sent by a UE (re: clause 4.2.1 step 7 and clause 6.1).
2. To TS 23.009 and TS 48.008, to provide additional clarification on service based handover from GERAN (re: clause 4.2.1, step 8 and clause 4.4.1, step 2).
3. To TS 32.205 to add a "redial flag" to the MSC CDR for Mobile Originated calls (re: clause 6.1).