Overview of P25 ISSI Documentation Suite
The documentation suite which defines Scope One of the P25 ISSI consists of five standards.
- ISSI Messages and Procedures for Voice Services
- ISSI Measurement Methods for Voice Services
- ISSI Performance Recommendations for Voice Services
- ISSI Conformance Testing for Voice Services
- ISSI Interoperability Testing for Voice Operations in Trunked Systems
A brief overview of each of these standards is provided in the subsections that follow.
ISSI Messages and Procedures for Voice Services
Scope One of the ISSI Messages and Procedures for Voice Services specifies the functional services of mobility management, call control and transmission control to provide trunked voice services for SU-to-SU and Group PTT calls involving multiple RFSSs.
Mobility management uses the SIP protocol and describes the messages and procedures necessary for RFSSs to perform registration, and affiliation across the ISSI for roaming SUs.
Call control also uses the SIP protocol and describes the messages and procedures necessary for RFSSs to set up and tear down a call, and manage RTP resources.
Transmission control uses the RTP protocol and describes the messages and procedures necessary for RFSSs to convey voice information, and manage voice call requests.
The functional service responsibilities of an RFSS in a call are dependent upon the type of call and also on the role of the RFSS in a call.
The specifications developed in the ISSI Messages and Procedures for Voice Services standard provide the fundamental starting point for the remaining standards in the ISSI suite of standards.
ISSI Measurement Methods for Voice Services
The ISSI Measurement Methods for Voice Services is based on the functional services and protocols defined in the ISSI Messages and Procedures for Voice Services standard.
Scope One of the ISSI Measurement Methods for Voice Services provides detailed measurement procedures to measure the ISSI Voice Service (IVS) Call Set-Up Delay (CSD) and IVS Message Transfer Delay (MTD) performance for SU-to-SU and Group calls.
IVS-CSD and IVS-MTD performance parameters are used to evaluate the delay associated with successful packet transfers across RFSSs and across the IP backbone connections that link adjacent RFSSs.
The ISSI Performance Recommendations for Voice Services is a companion standard to the ISSI Measurement Methods for Voice Services standard. Scope One of the ISSI Performance Recommendations for Voice Services provides agreed upon (by manufacturers and end users) average and maximum values for the IVS-CSD and IVS-MTD performance parameters described in the ISSI Measurement Methods for Voice Services standard.
The ISSI Conformance testing for Voice Services defines a set of procedures to test the conformance between two RF Sub-systems using an IP backbone network. The procedures define reference-signaling sequences for SU-to-SU and Group call scenarios.
ISSI Interoperability Testing for Voice Operations in Trunked Systems
The ISSI Interoperability testing for Voice Operations in Trunked Systems defines procedures to test the interoperability of SUs, and RFSSs from different manufacturers while performing trunked voice operations in configurations that use the ISSI.
The trunked voice operations include registration of subscriber units, affiliation of subscriber units to the Subscriber Group Home, initiation of an SU-to-SU call, and initiation of a Group call.
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E.164 is an international standard, titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services over the Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS).
An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking: the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different.
Message-oriented middleware (MOM) is software or hardware infrastructure supporting sending and receiving messages between distributed systems. MOM allows application modules to be distributed over heterogeneous platforms and reduces the complexity of developing applications that span multiple operating systems and network protocols. The middleware creates a distributed communications layer that insulates the application developer from the details of the various operating systems and network interfaces. APIs that extend across diverse platforms and networks are typically provided by MOM.
HCL Sametime is a client–server application and middleware platform that provides real-time, unified communications and collaboration for enterprises. Those capabilities include presence information, enterprise instant messaging, web conferencing, community collaboration, and telephony capabilities and integration. Currently it is developed and sold by HCL Software, a division of Indian company HCL Technologies, until 2019 by the Lotus Software division of IBM.
Project 25 is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. P25 radios are a direct replacement for analog UHF radios, but add the ability to transfer data as well as voice, allowing for more natural implementations of encryption and text messaging. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with handheld walkie-talkie use.
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ASTRO 25 is the next generation of ASTRO digital two-way radio communications by Motorola Solutions. Motorola first introduced digital two-way radio in the U.S. in 1991 under the name ASTRO Digital Solutions.
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Iristel is a Canadian provider of Voice over Internet Protocol services (VoIP), and is designated as a competitive local exchange carrier (CLEC). The company was founded in 1999, and is headquartered in Markham, Ontario.
Digital mobile radio (DMR) is a limited open digital mobile radio standard defined in the European Telecommunications Standards Institute (ETSI) Standard TS 102 361 parts 1–4 and used in commercial products around the world. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.
AES67 is a technical standard for audio over IP and audio over Ethernet (AoE) interoperability. The standard was developed by the Audio Engineering Society and first published in September 2013. It is a layer 3 protocol suite based on existing standards and is designed to allow interoperability between various IP-based audio networking systems such as RAVENNA, Livewire, Q-LAN and Dante.
