P25 Vendors Offer Informal Reports on P25 ISSI/CSSI Tests
By Stephen Nichols
Monday, March 18, 2019 | Comments

The Project 25 (P25) Technology Interest Group (PTIG) posted a template for reporting Inter-RF Subsystem Interface (ISSI) or Console Subsystem Interface (CSSI) interoperability test results obtained outside the DHS P25 Compliance Assessment Program (CAP). PTIG also posted the first report using the template, which outlines recent Motorola Solutions and Avtec CSSI Interoperability testing results.

Although informal ISSI and CSSI testing has been conducted among suppliers for years, sometimes with user involvement, the information has not been made publicly available although it is beneficial to the P25 market. PTIG does not have a testing program and does not sponsor product testing. This article explains the background of the ISSI/CSSI reporting template and the reason for posting the information.

The CAP publishes manufacturer’s documents that describe the results of performing tests identified by CAP in compliance assessment bulletins (CABs). CAP prescribes that testing be performed by DHS-recognized laboratories, and officials submit test results using the prescribed format for summary test reports (STRs) and accompanying suppliers declaration of compliance (SDoC). The test documentation is reviewed, and following DHS approval, is posted on the CAP website to ensure that test results are legitimately obtained, reproducible and consistently reported.

In 2010, the CAP published a CAB identifying a set of conformance and interoperability tests for the ISSI. This CAB referenced two conformance and interoperability test standards published by the Telecommunications Industry Association (TIA): TIA-102.CACC: P25 ISSI Conformance Test Procedures and TIA-102.CACD-A: P25 ISSI Interoperability Test Procedures for Trunked Voice Operation Involving the ISSI.

In 2016, the CAP published a revision of the ISSI CAB, identifying a set of conformance and interoperability tests for the ISSI. This CAB referenced the conformance and interoperability test standards published by TIA.

To date, there are no labs recognized for ISSI or CSSI CAP testing; therefore no ISSI or CSSI SDoCs/STRs are available on the CAP website. The CAP is revising its ISSI/CSSI testing documentation and standing up a government laboratory to conduct the testing. Conformance testing documents are undergoing a public review period with comments requested by March 31. At the March 5 CAP advisory panel meeting, officials reported that drafting of ISSI/CSSI interoperability testing documents is in progress. Once the revised CAP documents are published, labs will have the opportunity to seek CAP recognition and manufacturers can begin testing per the requirements of the CAP.

Even though ISSI or CSSI SDoCs/STRs are not available on the CAP website, manufacturers have been performing ISSI and CSSI testing outside the CAP. Some P25 users and customers have been provided with non-CAP manufacturer test reports upon request, and the P25 community determined that collecting and publishing non-CAP testing reports would benefit more P25 users.

In 2018, the Association of Public-Safety Communications Officials (APCO International P25 Interface Committee’s (APIC) Compliance Assessment Process and Procedures Task Group (CAPPTG) created an Excel template to provide a consistent method for reporting ISSI or CSSI testing performed outside the CAP. Unlike CAP, this template does not require testing any particular set of standard features and does not require particular test procedures. The template only intends to define a consistent method for reporting what has been tested. Also unlike CAP, the testing may or may not be performed in an ISO-recognized lab.

The aim of the CAPPTG template is to enable P25 equipment providers or users to report on interoperability testing that they performed. This testing would identify the common set of standard ISSI or CSSI features that both end point manufacturers support, the versions of products tested, some basic testing configuration information and the contact information for the manufacturer representatives who could answer questions about the testing. The information was intended to help other P25 users.

In 2018, and in parallel with the CAPPTG effort, the TIA TR-8.19: Wireline Interfaces Engineering Subcommittee revised the ISSI/CSSI interoperability testing standard to clarify how ISSI or CSSI testing could be consistently performed between two end points, using a single “hop” of the interface under test and recommended how the results of testing in such a configuration could be consistently reported. This revision, TIA-102.CACD-C: P25 ISSI Interoperability Test Procedures for Trunked Voice Operation Involving the ISSI, was published in November. The revision made no changes to the standard tests previously published.

The CAPPTG template was endorsed by the P25 Steering Committee, and after discussions with CAP and PTIG officials, PTIG agreed to post the template, making it available to equipment manufacturers and users. While ISSI and CSSI interoperability testing between manufacturers has been going on for several years, Motorola Solutions and Avtec filed the first report that used the template. This report covers non-CAP CSSI interoperability testing that was performed by product engineers from the two manufacturers using a virtual private network (VPN) connection between the companies’ development test labs.

The P25 community plans to make more test reports available to benefit P25 users.

Stephen Nichols is director of the P25 Technology Interest Group (PTIG). For more information, visit the group’s website.

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