1. Genuine P25 Interoperability: Tips and Traps When Moving to Digital Radio
Scott Skibness
Tait Communications

2. Learning Objectives
An update on the latest standards, interfaces and certification bodies and their implications for procurement decisions
Understand why the P25 Compliance Assessment Program matters to you
With all of this why don’t all P25 radios work on all P25 networks?

3. Project 25: History Designed for public safety by public safety
Developed in partnership between APCO and TIA
Initial P25 standards were released in 1995
P25 is a suite of mobile radio standards and bulletins which define interoperable communications for emergency services
They are continuing to evolve; Phase 2 trunking is in progress
The result?
True multi-source procurement and interoperability
Smooth migration from analog

4. Project 25/TIA 102 Standards Suite
The standards suite allows for
some features that are:
Mandatory
Standard options: where if offered they must follow the standard
Manufacturer’s extensions to the standard: these can fit within the framework of the standard
Caveat: watch out for manufacturer extensions that are similar to standard options 4

5. Project 25: More Than An Air Interface

6. Project 25 Standards: Roll-out Phases
P25 requirements and standards for a digital Common Air Interface (CAI) using FDMA 12.5 kHz channels and for the supporting system
Must be backwards compatible with FM analog
Phase 2
P25 requirements and standards for a digital CAI using kHz channels or equivalent and for the supporting system
Must be backwards compatible with Phase 1 digital only The primary improvement in Phase 2 is spectral efficiency
Note: Phase 2 is sometimes interpreted as referring to P25 requirements and standards supporting both Phase 1 and Phase 2 systems, such as the ISSI, Fixed Station, and Console Interfaces
Spectral efficiency is primarily a focus for US. Currently there is no good reason for TAP to move to Phase 2 6

7. Project 25 Standards Status: Phase 2
Most vendors are offering P25 Phase 2 upgradable equipment today
A number of test documents are still to be started
Uses half rate vocoder in 2-slot TDMA
Conventional Phase 2: work will commence on conventional 2-slot TDMA
What does this mean for you?
People are only now starting to understand Phase 1!!
There is no need/regulatory push for Australia to adopt Phase 2.
We do not know of any vendor publically committing to availability dates for Phase 2
What does this mean for you?
Phase 2 standards are currently being worked on, but the equipment is a way off… 7

8. P25 Compliance Assessment Program (CAP)
CAP Test Bulletins
Lab Assessments
Multi-Vendor CAP Testing
Suppliers Declaration of Compliance
Responder Knowledge Base Posting
Department of Homeland Security (DHS)
DHS recognised manufacturers’ & independent test laboratories
Equipment tested against the specifications
Assurance of interoperability between manufacturers’ equipment
DHS recognised manufacturers’ test laboratories
Interoperability testing between vendor’s subscribers and infrastructure – Strongest test around: Competitor tested for P25!
User has the freedom to choose in a multi-vendor environment (many systems have more than one vendor on the system)
Buyers of Phase 1 P25 equipment can be certain they will work seamlessly with other equipment and conform to P25 standards
Proof that Phase 1 P25 is a good long-term investment
Performance specs: type approval tests ++
The Project 25 Compliance Assessment Program (P25 CAP)
A voluntary program that allows P25 equipment suppliers to formally demonstrate their products’ compliance with a select group of requirements within the suite of P25 standards
Purpose: is to provide emergency response agencies with proof that their equipment meets P25 standards for performance, conformance and interoperability
Supplier’s Declaration of Compliance (SDoC)
Summary Test Reports (STR)
SDoCs/STRs on the Responder Knowledge Base (RKB) 8

9. Responder Knowledge Base (RKB) Website
Who is FEMA?
Benefit to the customer is that they can choose a selection of products that will work together. They are no longer tied to just one manufacturer. Benefit is choice.
→ Other Content → Certifications and Declarations → P25 SDoCs 9

10. Why Do We Need The CAP? Choice for buyers
Multiple users on a single network can use the P25 technology and various vendors’ P25 products on that network
Users can purchase the right fit for their needs with more options
Security to buyers
The CAP offers a formal assurance program
Confidence in interoperability
P25 equipment meeting the CAP standards
Federal grant money in the US is dependant on interoperable products … but the CAP is still of interest in other regions
P25 CAP - consistency of technology
Emphasis on Tait’s laboratory as the first outside US
Phase 1 only currently: many people are only starting to understand Phase 1 – only USA has the push to go to Phase 2
No room for proprietary signalling at the moment
What does this mean for you? Implications = potential for no interoperability
User has the freedom to choose in a multi-vendor environment (many systems have more than one vendor on the system)
P25 CAP tests are still evolving and the focus is more on Phase 1 (with mature products) as opposed to Phase 2 which is not till later
The main benefit for people in the US to worry about Phase 2 is spectral efficiency. If this issue doesn’t concern you, neither should Phase 2.
Multiple vendors with mature Phase 1 products
Few vendors with Phase 2 products (not mature) – there is lots of testing to come behind the CAP testing
Phase 2 standards are still evolving: they are close to defining the standards, but the compliance standard has not even begun yet.
Caution that Phase 2 products released now may not be interoperable once the standards are defined.
No strong reason to use Phase 2 in TAP as there is no mandate from regulators for narrowbanding here (unlike the FCC in the US) 10

11. Who Defines The CAP? Approved by the CAP Governing Board
Comprised of representatives from US Government agencies
Generally follows the TIA recommendations for compliance assessment tests
References standard tests
Published in Compliance Assessment Bulletins (CAB)
********* Be aware of the following***********
Disagreements between the manufacturers and NIST, re performance tests.
NIST want to add conformance tests, but manufacturers want to test against themselves, not against a stub (test protocol vs test stub?). This allows room for interpretation says NIST and possible un- interoperability if interpretations exist between manufacturers
No manufacturers on CAP governing board 11

12. Four Vendors with P25 CAP Recognized Labs Worldwide
Standard test process to become recognized
Vendor hosted CAP interoperability testing in a recognized lab
Tait, Motorola, EF Johnson and Harris
Other CAP testing such as performance testing is also completed
After testing, SDoCs and STRs are published to the RKB website
Goal: cooperation between P25 vendors for interoperability
Vendor hosted CAP testing events: Motorola, EFJ, Tait, Harris have hosted… Motorola twice (evolving the process – not all manufacturers need to retest if changes are minimal – can claim “interoperability” based on minor changes not affecting test outcomes.
APCO 25 Interface Committee (APIC):
A P25 committee, comprised of P25 users and equipment manufacturer representatives, which develops initial drafts of P25 standards.
2.4.3 Compliance Assessment Bulletin:
A Compliance Assessment Bulletin is the primary product created by the P25 CAP/GB. The scope of a CAB can range from policy to guidance, covering issues such as specific test standards to be used for a particular P25 interface, guidelines for the creation of an SDoC, P25 LMR RFP Guidance, etc.
2.4.4 Compliance Assessment Process and Procedures Task Group (CAPPTG):
A subcommittee of the APCO 25 Interface Committee, or APIC. The mission of the CAPPTG is to ensure that P25 equipment and systems comply with P25 standards for interoperability, conformance, and performance, regardless of equipment supplier, and in accordance with the User Needs Statement of Requirements.
2.4.5 Declared Equipment:
A P25 product which: 1) has been tested at a P25 CAP-recognized laboratory; 2) has been determined by the equipment supplier to be compliant with all current requirements of the P25 CAP; 3) possesses a Supplier’s Declaration of Compliance (SDoC); and 4) has a summary test report that has been reviewed for accuracy and completeness by the P25 CAP Laboratory Program Manager.
4.2 Demonstration of Compliance
The test methods used in the program are chosen from P25-approved standards that are customarily drawn from the TIA-102 suite of standards. The intention is for the suite to contain performance, conformance, and interoperability test standards for each interface or major service. A variety of test methods are contained within each test standard. Many but not all of these test methods will be included in the minimal set of tests required for compliance demonstration in this program. A joint group of users and equipment suppliers, in the P25 Compliance Assessment Process and Procedures Task Group (CAPPTG), evaluates each test method within a test standard for suitability and inclusion within the program. CAPPTG then compiles a list of the required test methods drawn from each test standard, and releases them in the form of a draft compliance related Telecommunications Systems Bulletins (TSB). The compliance related TSB is approved by the P25 Steering Committee, and routed to the TR-8 for final editing and publication. The P25 CAP/GB uses these TSBs as the basis for the creation of CAB’s with regard to required testing, but is not limited to the material in the compliance related TSB’s. 12

13. Trade-offs Interoperability ≠ Total Interoperability
Proprietary extensions
Performance ≠ Coverage Guarantees
Testing
Culpability 13

14. Why don’t all P25 radios work on all P25 networks?
Different interpretation of the standards
Different implementation of the standards
Usability of the radio
Requirement for non-standard functionality 14

15. Interpretation of the P25 standards
Different interpretations of the standard
Features outlined in the standard that WILL work
group calls
registration
affiliation
unit to unit calls
However… on most networks there are other features required.
Patch Calls
Dynamic Regrouping
Failsoft 15

16. Differences in Implementation
Not all standards are clearly defined
Many of the items in the standards are open to interpretation
Control Channel Hunt – items like acquisition, retention, what is a valid CC, and when to leave are detailed but how to find one and select which to use or keep are not.
Or deployed with additional capabilities
Radio inhibit and uninhibit – The standard defines how this will work but the data is unencrypted as defined so vendors add encryptions within the system for these which limits the functionality to others. 16

17. Usability of the Radio Differences in features and operation.
‘Usability’ is one of the major obstacles for having multiple vendors on a state-wide network.
Acceptance or certification testing is based on an existing terminal and how it operates and not the P25 standard
Scan configuration
Programming Units
Alert sounds and configuration 17

18. User Misunderstandings About the Standard
Largely defined by the individual vendors, or the user when programming. Therefore NOT uniform.
Vendor
Proprietary
Features
Defined by the P25 Feature Sets At the 3 levels
User
Interface:
Tones,
Display,
Lights,
Knobs,
etc.
User
Programming:
Tones,
Channels,
Features, etc.
Standard
Options
User
Programming
Interface:
channel
lists, pull
down menus,
Etc..
P25
Air Interface
& Signaling:
ID, Alarms,
Features,
etc.
Core
Features
P25 Feature Sets
User P25 Experience 18

19. Non-Standard Functionality
Adding functionality that is not available to other suppliers
Network suppliers add services that help make its terminals function more efficiently.
Dynamic Power Control
Providing functionality that limit interoperability with other vendors radios on the network.
Non-standard Encryption – insist on AES or DES
OTAP
Limit what is granted in a license to a few features 19

20. Lesson Learned Examples from past systems
Non-standard frequency splits
Failsoft function with unique code words where in some cases it included a specific manufactures ID
Unused bits that change states from system to system.
Lack of testing on the system means some conditions are not found out until the units are deployed 20

21. Lessons Learned Limit testing of “proprietary” features
Vendors need more than the minimum information to work effectively
Willingness of the network owners to work with the other vendors
Not all users will need or want the same functionality so make sure you are not limiting their choices with the certification process
Test failures are not just a failure for a vendor
They are a failure for the P25 standard and interoperability.
SAVINGS – customers have seen a 30% to 40% savings or more in the cost of subscriber units when multiple vendors radios are offered on a system. 21

22. Genuine P25 Interoperability: Tips and Traps When Moving to Digital Radio
Scott Skibness
Tait Communications