ECP3078Apage 3 Contents What is P25? M/A-COM P25 Terminal Equipment Call Types Unit IDs Call Processing Emergency Calls Group Scanning ProScan Terminology
ECP3078Apage 4 What is P25? Interoperable digital radio system standard Intended for all public safety LMR bands (VHF, UHF, and 800 MHz) Developed Jointly by: –TIA –Association of Public-Safety Communications Officials (APCO) –National Association of State Telecommunications Directors (NASTD) –Various agencies of the Federal government (FED) in the early 90s to improve spectral efficiencies. TIA/EIA Standard in 1999. Under TIA/EIA-102
ECP3078Apage 5 Project 25 Benefits Key benefits sought by the user community: –Competitive procurement of equipment –Interoperability of equipment –Spectrum efficiency –User-friendly operation equivalent to today's public safety equipment and common across all bands, system configurations, services, and manufacturers.
ECP3078Apage 6 Project 25 Features Key voice features –IMBE vocoder –Group and Individual calls –Telephone interconnect –Emergency –Encryption (DES, AES) –Console dispatch –Preempt –OTAR (Over-the-Air-Rekeying) Packet switched IP backbone –Full control of the system and radios –Interoperability - network level and radio level –Group, individual, emergency calling
ECP3078Apage 7 Some P25 System Basics Each Radio: –Unique Unit ID –One or More Systems (sites) –One or More Talk Groups (Group ID) Talk Group: –A Logical Collection of Units –Unique Group ID Capacities: –16,777,216 Unit IDs –65,536 Group IDs TRAINING TRNG 1 TRAINING TRNG 1
ECP3078Apage 9 M7100 Mobile Radio System Control Head Scan Control Head Hand-held Controller
ECP3078Apage 10 P25 Terminal Features P25 Group call transmission/reception Talk group identification Group call alert P25 Individual call transmission/reception Individual identification (PTT ID) Emergency and Emergency Indication Priority Scan Carrier control timer (CCT) Transmit lockout Up to 256 conventional channel capacity TRAINING TRNG 1
ECP3078Apage 11 Call Types Voice Calls –Group Calls Normal Emergency Announcement Groups –Individual Call Unit to Unit –System All Call Radio displays Group and Caller ID for each call
ECP3078Apage 12 Unit Identification Unit ID –Uniquely identifies radio to system –24 Bits – 16,777,216 Possibilities (0 - 16,777,215) –Only allow 1 – 9,999,999 –Must be programmed into radio –Allows Individual Calling –Allows Call Tracking TRAINING TRNG 1
ECP3078Apage 13 Conventional vs. Trunked Computerized Assignment of Channels Service Employee Customer Conventional Trunked Service Counter
ECP3078Apage 14 Call Processing Mobiles / Portables continuously monitor Control Channel Operator makes selection, depresses PTT, and transmits a Channel Request message Channel Request received by Control Channel System validates request against the Group and Unit databases Control Channel responds with Working Channel assignment Units switch to the assigned Working Channel –Calling Unit is now ready to talk, caller can be advised by a grant tone beep to start talking –Working Channel adds messages to voice signal that provides for extracting units from calls –Control Channel continues to send update messages to provide late entry for other units
ECP3078Apage 15 Call Processing (cont.) Calling unit releases PTT and sends Channel Release message Working Channel sends Channel Drop message out to all units All units return to Control Channel Channel Access –If Channel Request is valid, Control channel will assign the call to a Working Channel –If Group or Individual ID is not properly programmed into system, Call is denied –Network Switching Server (VNIC) will route the call to other systems as necessary
ECP3078Apage 16 Call Processing Exceptions Call Queued –All channels are assigned to other calls –Automatically placed in queue for next available Working Channel –Queuing priority determines order of channel assignment Call Denied –System programming does not allow request –Out of range of Control Channel –Retry in different location System Busy –System programming can not complete call at present time –Individual call to busy radio –Retry later ? ? ? ? ?
ECP3078Apage 17 Emergency Call Processing Emergency button on mobiles and portables initiates emergency call or emergency alert Elevates talkgroup to emergency status Dispatcher notification through console Other radios listening to talkgroup are notified with an audible alert Group call –Requests access for a high priority Emergency call –Flags Consoles and other units in group with *RX EMER* –Identifies caller Clearing an Emergency –Return group to normal status –Radio must be programmed for Clear Emergency
ECP3078Apage 18 Group Call Scanning Radio is able to monitor multiple groups Radio can only receive one group at a time Responding to a call (programmable) –Selected group –Scanned group (within timer period) Scan groups on Scan List –Fixed list in programming –Programmable by user Scan Control –Fixed in programming –Controlled by user Priority 1 Group Priority 2 Group Group 1 Group 2 ?
ECP3078Apage 19 ??? How Far Does it Cover? Many factors affect coverage: Site Location Urban clutter (+ & -) Reflections / Multipath (+ & -) Ducting over water (+) Wet pine needles (-) Weather (+ & -) Frequency (+ & -) Earth curvature Many others… (+ & -)
ECP3078Apage 20 ProScan Enhanced System Scanning Feature (compared to WASS): –Algorithm Based on Received Signal Strength Indicator and CC Verification –Scans after Signal RSSI Drops below a User Defined Threshold –Searches for new System Based on Defined Adjacent System Scan List –Switches to new System, if User Defined Criteria is Met –Provides Better Audio Quality Site 1 Site 2 Network Switching Center
ECP3078Apage 21 Programming Cables TQ 3392 – P7100, P5100 TQ 3409 – M7100 (Shop) TQ 3410 – M7100 (Field) TQ 3419 – P7100, P5100 (without TQ 3370 interface) TRAINING TRNG 1 Radio Programming Every M/A-COM P25 radio is programmed with a personality. A Data file: –Directs the operating characteristics of the radio –Interfaces the radio to a system This personality is what makes a radio unique to the user of the radio.
ECP3078Apage 22 C3 Maestro IP Dispatch Consoles Purpose: Monitors & controls multiple Groups at a single physical position A single Microphone/PTT and Selected & Unselected Speakers Adds Patch & Simulselect capability to the P25 System Provides EMERGENCY control Physically: Can be programmed with 112 Groups Simultaneous audio based on Talk path licenses –Standard – 4 talk paths –Maximum – 20 talk paths
ECP3078Apage 23 Terminology AESAdvanced Encryption Standard (256 bit encryption) CAICommon Air Interface CNMCentralized Network Manager CTCSSContinuous tone coded squelch system DESDigital Encryption Standard (56 bit encryption) – Type III or DES-OFB DVUDigital Voice Unit FDMAFrequency Division Multiple Access GWBGateway Board; OpenSky term for the Interoperability Gateway DVU board IMBEImproved Multiband Excitation – 3rd generation voice encoder developed by Digital Voice Systems, Inc. IPInternet protocol
ECP3078Apage 24 Terminology KMFKey Management Facility LMRLand Mobile Radio MDISMobile Data Intermediate System; software on the NSS MESMobile End System. Mobile or portable. MMEMiniature Mobility Exchange NASNetwork Administration System NMCNetwork Management Console. Previous name for RNM NOCNetwork Operations Center NSCNetwork Switching Center NSSNetwork Switching Server P25APCO Project 25; a standard Common Air Interface protocol for radio operation and system interface specifications developed by TIA to provide for interoperability of different manufacturers equipment
ECP3078Apage 25 Terminology PSTNPublic Switched (or Service) Telephone Network PTTPush-To-Talk (depressing the radio transmit key) RFRadio Frequency RNMRegional Network Manager RXReceive or Receiver SiteProSitePro Controller (controller for each repeater station) SMISite Management Interface; software installed on the Network Sentry TDMATime Division Multiple Access TXTransmit or Transmitter UASUnified Administration System VESVoice End System. User. VNICVoice Network Interface Controller, software on the NSS VoIPVoice over IP