This document specifies values for performance parameters defined in a companion TIA standard, Project 25 Inter-RF Subsystem Interface (ISSI) Measurement Methods for Voice Services [1]. The scope of this document is limited to the specification of performance parameter values in the context of the measurement methods standardized by the normative references.

The objective and purpose of this document are to specify minimum levels of performance for ISSI voice services (IVS) that are used in providing P25 wide area voice services.¹ The intended users of this document include P25 voice service providers, equipment manufacturers, and end users. This document may be used (1) by service providers in the planning, development, and assessment of P25 voice services that meet end user performance needs, (2) by equipment manufacturers as performance metrics that will affect equipment design, and (3) by end users in evaluating performance.

Note: The scope of these performance recommendations is limited to systems based on terrestrial IP backbone networks. The scope does not include systems that use satellite links within their IP backbone networks. The use of satellite links is left for further study.

¹In the context of this document, P25 wide area voice services are any SU-to-SU or group PTT call types that invoke ISSI functional services and protocols (i.e., when use of more than one RFSS is required for a particular IVS call scenario of interest). The term P25 wide area voice services (or, in the context of this document, similar terms such as wide area call) is used to emphasize that a principal role of the ISSI is to increase the geographical coverage area for roaming SUs; however, the ISSI more generally enables the interconnection of multi-vendor RFSSs among and within P25 systems.