Capacity Max Fast Start

Fast Start is a new feature in Capacity Max that allows a talkgroup call to start even if a payload channel (a.k.a traffic channel) is not available at all participating sites.

Capacity Max is different to Capacity Plus in that a talkgroup call is only streamed to a RF site if a participating radio is registered there. 

When a radio connects to a Capacity Max system, there is an exchange between the system and radio. Part of this exchange is the radio telling the system which talkgroup(s) is (are) of interest to it. 

Based on this information, the trunking controller will ensure a call is routed to that site.

Prior to M2022.01, if a payload channel was not available at one or more participating sites, the call would be queued - unless the initiating radio used call pre-emption. This would be noticeable if there were sites in the system that have a comparatively low number of channels.

Capacity Max now supports two call setup methods: 

👉 All Start, where a free timeslot is needed at all sites to complete the call.

👉 Fast Start, where a call will go ahead on whichever sites have free slots at that time.

Fast start supports talkgroup call; broadcast call; site-wide and system-wide all call as well as phone patch calls. It works in both Open System and Advantage modes.

The above diagrams show the scenarios with All Start and Fast Start. All the radios are on the same talkgroup. With All Start, if Radio B tries to make a talkgroup call, it will be queued as there are currently no payload channels on Site 1. With Fast Start however, the talkgroup call will go ahead as normal on sites 2; 3 and 4 (with Radios B; C and D). With Fast Start, Radio A may join the call late or may even miss the call.

Remember that with fast start, if the site; where the call initiating radio is located; is busy, the call will still be queued - unless busy call pre-emtion is used. So, for example, if Radio A were to make a talkgroup call, the request would be queued since all the channels at Site 1 are busy.

Fast start is configured in Radio Management. In the Capacity Max System Set, there is a drop-down to select between disabled; site-wide or system-wide. If disabled is selected, All Start is used. If system-wide is selected, fast start is applied to all sites in the system. If site-wide is chosen, then one can choose (tick) which sites will use fast-start in the Sites Table of the Capacity Max System Set.

If a fast start call starts on only some of the participating sites, the radios at the other sites will join the call as soon as a payload channel becomes free. Similarly, if all of the VRC talkpaths are consumed by other calls, the fast start call will be streamed to the dispatcher/application as soon as a talkpath becomes available.

The risk with Fast Start is that if a call goes ahead on sites where a payload channel (timeslot) is available, users who are at sites where there was no payload channel (e.g. Radio A in the above diagram) may miss part, or all, of a talkgroup call. 

In some circumstances, this may be undesirable and so careful consideration must be made before implementing this feature since it is not possible to configure fast start on a by-talkgroup basis.