The Government Emergency Telecommunications Service (GETS) is an organization established to support the United States National Communications System (NCS). The role of GETS is to provide specialized call processing in the event of congestion and/or outages during an emergency, crisis, or war. GETS has already established capabilities to facilitate priority call treatment for wireline/fixed networks, including the local exchange and long distance networks. In the event of an emergency, the authorities would be able to gain faster access to telecommunications resources than the every-day citizen.
GETS in Fixed Networks
To gain special access privileges, government officials and emergency service personnel would utilize a special universal access number and PIN for authentication. Once authenticated by the network, the calling party would be put into a special priority queue.
During an emergency, normal callers would receive a busy tone, announcement (of all circuits busy), or nothing at all. The special access caller would be placed into a queue until a facility is available. Once a facility is available, the network would utilize ISUP to connect the caller. However, the GETS emergency services implementation of ISUP is different than normal ISUP.
In a normal calling scenario, the ISUP portion of the SS7 network searches facilities on an end-to-end to establish overall voice trunk availability.
This means that voice trunks are reserved along the way, but not seized unless there is at least one available circuit along the entire call path to carry the call. This would not bode well in an emergency, as it would take an inordinate amount of time for an entire call path to become free. Therefore, GETS has implemented a different method.
GETS requires implementation of ISUP signaling for all calls for each trunk along a call path to be seized when available. If the entire call path is not available, the system simply seizes a trunk up to a given point. At the last point of seizure, the terminating switch initiates priority queuing once again, starting the process over again. Unless all circuits along a given call path are inoperable or indefinitely held, the caller will eventually be connected from end-to-end reaching the intended call termination point.
GETS in Mobile Networks
The GETS system works well for wireline networks. However, in wireless networks there is the radio interface access port in which to contend. This is an area where mobile IN technologies (WIN and CAMEL) can be of great benefit.
One deployment scenario involves the use of mobile IN to establish a radio port queue.
In this scenario, an MSC equipped with the necessary mobile IN trigger would, upon dialed digit analysis of the special access number and PIN, place an emergency service person in a special queue. The caller would be provided a radio access port as soon as one becomes available. This same queuing process would be utilized to seize a voice channel between the MSC and the PSTN. Once the caller acquires a voice channel and voice circuit to the PSTN, the PSTN switch would recognize the incoming call as a priority call, starting the process described above for wireline calling.
Should the call be destined for another mobile user, the terminating switch could perform similar mobile IN call processing. The terminating call could be placed into queue until a radio channel is available to page the mobile and terminate the call.
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