A technique for implementing Special Call Services (SCS) to extend
wireless system functionality to include private emergency or other types
of service-specific special calls in a private network. In a preferred
embodiment, the capability is implemented by taking advantage of certain
service type elements that may be coded in the Radio Resource Management
(RR) functional layer channel request message and/or the Mobility
Management (MM) functional layer call request messages in a Global System
for Mobile (GSM) communication system. Specifically, an establishment
cause field in a RR channel request message and/or a service type field
in a MM request message is used to request such services from the
network. These establishment causes and service types can be defined, but
not limited to, using those codes currently defined as reserved by GSM
Version 4.08, Section 9.1.8 and Section 10.5.3.3. Thus, these newly added
codes do not require any re-programming of the deployed GSM equipment and
impact on their current operation, either. A GSM system that implements
the invention preferably contain a Radio Resource (RR) functional entity
that watches for a newly added SCS causes and takes them into account
when granting physical resources to the requesting unit. Such actions may
include, but are not limited to, dropping a normal call-in-process in
order to accommodate the SCS call if there are no free physical resources
left, prioritizing SCS calls in progress, or other techniques for
allocating a physical channel to the SCS channel request. Such techniques
may include allocating radio resources which are reserved in advance for
the SCS cause.