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Genuine P25 Interoperability: Tips and Traps When Moving to Digital Radio. www.taitradio.com. Scott Skibness Tait Communications. Learning Objectives. An update on the latest standards, interfaces and certification bodies and their implications for procurement decisions - PowerPoint PPT Presentation
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Genuine P25 Interoperability: Tips and Traps When Moving
to Digital Radio
www.taitradio.comScott Skibness
Tait Communications
2
Learning Objectives
1. An update on the latest standards, interfaces and certification bodies and their implications for procurement decisions
2. Understand why the P25 Compliance Assessment Program matters to you
3. 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 safetyDeveloped 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 forsome features that are:a) Mandatoryb) Standard options: where if
offered they must follow the standard
c) 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
5
Inter RF Inter RF SubSystemSubSystem
Interface Interface (ISSI)(ISSI)
Telephone Telephone InterconnectInterconnect
(PSTN)(PSTN)
Data Data InterfaceInterface
e.g. Databasese.g. DatabasesGateway
NetworkManager
Consoles
P25Portables
P25 Repeaters
PSTNPSTN
Other P25Systems
Other P25Systems
Common Air Common Air Interface (CAI)Interface (CAI)FDMA & TDMAFDMA & TDMA
ConsoleConsoleSubSystemSubSystem
InterfaceInterface(CSSI)(CSSI)
Fixed StationFixed StationInterface Interface
(FSI)(FSI)
P25 RF SubSystem(RFSS)
Subscriber Subscriber Data Data
Peripheral Peripheral Interface Interface e.g. MDTe.g. MDT
MDT
P25 Mobiles
GatewayFunctionality*
*Not all manufacturers will require a separate gateway device.
Project 25: More Than An Air Interface
6
Project 25 Standards: Roll-out Phases
Phase 1• 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
6.25 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
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?
8
P25 Compliance Assessment Program (CAP)
Supplier’s Declaration of Compliance (SDoC)Summary Test Reports (STR)SDoCs/STRs on the Responder Knowledge Base (RKB)
CAP Test Bulletins
Lab Assessments
Multi-Vendor CAP Testing
Suppliers Declaration of Compliance
Responder Knowledge Base Posting
9
Responder Knowledge Base (RKB) Website
www.rkb.us → Other Content → Certifications and Declarations → P25 SDoCs
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 optionsSecurity to buyers•The CAP offers a formal assurance program•Confidence in interoperabilityP25 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
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)
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
13
Trade-offs
Interoperability ≠ Total Interoperability- Proprietary extensions
Performance ≠ Coverage Guarantees- Testing- Culpability
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
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
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.
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
18
User Misunderstandings About the Standard
VendorProprietaryFeatures
StandardOptions
Core Features
P25 Feature Sets User P25 Experience
P25Air Interface& Signaling:ID, Alarms,Features,etc.
Defined by the P25 Feature Sets At the 3
levels
Largely defined by the individual vendors, or the user when programming. Therefore NOT uniform.
User ProgrammingInterface:channel lists, pull down menus, Etc..
User Programming:Tones, Channels,Features, etc.
User Interface:Tones, Display,Lights, Knobs, etc.
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
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
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
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.
Test failures are not just a failure for a vendorThey are a failure for the P25 standard and interoperability.
Genuine P25 Interoperability: Tips and Traps When Moving
to Digital Radio
www.taitradio.comScott Skibness
Tait Communications
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