BY: Mark E. Brady, Chief Spokesperson, 240-508-7930
The word on the street is that no one will be able to monitor the transmissions involving the Prince George's County Fire/Emergency Medical Services (EMS) Department when we move to the new radio system. This could not be farther from reality. The main dispatch frequency and many operational channels will be able to be monitored with current scanner technology. Prince George’s County Executive Jack Johnson announced in December 2009 that the county officially launched the new 700 MHZ public safety communications radio system. “During my time as County Executive I have made many important announcements, but none as are important as the one I’m making today,” Johnson said. “After being known as the communication gap in the region for many years, today we are closing that gap by launching a new state-of-the-art radio system.”
To accommodate the new system, the county built 21 new radio towers, partnering with the state to build five of those. The total cost of the system is approximately $76 million, with $14 million in federal and state grants.
The new system will allow the county to maximize use of its public safety network by increasing capacity, expanding coverage and enhancing interoperability. With the new technology, all public safety agencies in the county will be able to communicate with each other and they will also be able to communicate with public safety agencies in surrounding jurisdictions.
The Police Department is the first agency to come online with the new system. They will be followed by the Department of Corrections, Sheriff and Court House security. The Fire/EMS Department is scheduled to come online in November 2010 to coincide with the opening of the new public safety communications center.
Fire/EMS Department radio transmissions will continue to operate and be heard on scanners as they are today for at least another year and the main dispatch channel will be heard on a frequency currently available for the foreseeable future. The same can not be said of the Police Department transmissions. A concern was raised by some that access to the public safety radio transmissions will not be able to be heard with current available technology. While the County Police Department is in the midst of training and installation of the new radio system, the Fire/EMS Department will not go on-line with the new radio system fully until April/May 2011. With current technology, scanners will still be able to monitor the main dispatch channel of the Fire/EMS Department. The main dispatch channel will be broadcast over a VHF frequency capable of being picked up by current scanners. This same VHF frequency will be delivering the transmission to all Fire/EMS Stations for the foreseeable future.
Operational channels will be able to be monitored on an 800 MHz radio on a percentage of incidents, depending on where that is located and if mutual aid companies are involved. Within six to eight months of full implementation by the Fire/EMS Department there will be a “standards migration” whereas scanner companies will be able to research and develop new technology capable of monitoring our new radio system, other then encrypted channels. This should occur during early 2012.
Another option is to purchase a Motorola Apex radio, model 1.5, which will be
programmed by Public Safety Communications personnel with receive only frequencies
to monitor all non-encrypted channels. A Memorandum of Understanding most likely
will have to be executed before radios are programmed.
There is a possibility that pertinent operational radio channels could be available by audio streaming over the internet. A feasibility review will be conducted to see if this option is even possible.
During this brief period of installation and initial implementation there will be times when a particular channel or incident will not be able to be monitored. The transition period will be a challenge for everyone from users to listeners and I’m confident that technology will catch up with the state-of-art radio system quickly. For those veteran scanner listeners you can relate this time to the first 800 MHz radio system. It was not long before technology allowed those channels to be monitored. I believe the same apprehension about our new radio system is occurring.
I have attached the following article by Alan Henney that describes in technical detail what is occurring with the radio system in Prince George's County.
This article is reprinted with permission by the author: Alan Henney
PRINCE GEORGE’S CO FINALLY GOES TRUNKED! SCANNER LISTENERS COULD BE SHUT-OUT FROM MUCH OF NEW RADIO SYSTEM
It will probably go down as the most costly project in county history. During January, Prince George’s County and its municipalities will start migrating police and fire/EMS radio communication to the county’s newly built $80 million Motorola 700 MHz trunked network.
Prince George’s County, the region’s last jurisdiction to vacate analog conventional channels to dispatch police and firefighters, becomes the region’s first jurisdiction to build on the recently vacated analog TV channels.
While the county’s new system offers improved audio quality for police and firefighters, for scanner listeners, this could mark the beginning of the end.
The county’s system use two digital formats – FDMA (frequency division multiple access), which is what most digital public safety radio networks currently use, and TDMA (time division multiple access), which doubles the capacity of each voice channel.
The problem for scanner listeners is that no scanner currently decodes TDMA. To further complicate matters, it may take years before one does! The public safety TDMA standards have not yet been adopted, so it is unlikely a scanner manufacturer will commit to a TDMA scanner at this point.
Prince George’s County’s system will mix FDMA and TDMA formats. We are told that some talkgroups, such as those used by fire/EMS personnel, will remain in FDMA mode to allow for easy interoperability. This gives other jurisdictions capability to monitor and communicate with PGFD if they have 700 MHz-capable digital radios such as the Motorola XTS 5000.
The police will primarily use the “unmonitorable” TDMA format. Adam and Charlie sectors, however, will supposedly use FDMA so those talkgroups may be monitored by Montgomery County police. As of this writing, however, they transmit in TDMA mode, along with the other PGPD talkgroups that are simulcast from the UHF-T band.
The other PGPD dispatch talkgroups will supposedly stay in TDMA mode, unless an older FDMA-only radio is monitoring the talkgroup. In that case, the transmissions will revert to FDMA mode, which will allow scanner listeners to monitor. Alternate/tactical PGPD channels will be TDMA only.
The county has 21 antenna sites (see map in page 8). The county’s system is divided into two tiers (or subsystems), one for the north, and one for the south. The dividing line is roughly Pennsylvania Avenue.
If you have a digital scanner that can receive 700 MHz, such as the BCD396T/996T, BCD396XT/996XT, PSR-500/600 or PRO-106/197, you can try to monitor the FDMA portion of the county’s new system.
Program your radio with two new systems (or sites), one for the north and one for the south. Set your scanner to P25 trunking and enter each set of the control channels as separate systems. You may ignore the TDMA ranges since the scanner cannot decode them!
North: 774.68125, 774.20625, 774.15625, 773.63125
South: 773.88125, 773.23125, 772.90625, 772.48125
Position Frequency Spacing Format
00 851.00625 6.25 FDMA
01 762.00625 6.25 FDMA
02 851.01250 12.5 TDMA
03 762.00625 12.5 TDMA
The county is using Motorola’s “Apex” series radios which include the APX 7000 for handheld use and the APX 7500 mobile radios.
The system will also employ GPS-tracking technology. Fire/EMS units will be tracked in realtime, while police officers will be polled as needed or when an officer presses the radio’s emergency button. The locations will appear on a map display in the dispatch center.
As for the public's inability to monitor the TDMA talkgroups, the county may offer a media plan. No announcement has been made. The radio would cost about $5000, perhaps as much as $6000.
In addition to the privacy TDMA currently offers, about 450 of the system’s 7000 radios will have encryption modules which cost about $1000 more per radio.
The county will retain a few public safety channels such as 155.685 and 155.79. One will simulcast the fire dispatch talkgroup and the other will be a telemetry circuit for firehouse alerting. The majority of the county’s VHF and UHF frequencies will be returned to the FCC for re-licensing.
The current UHF-T band police dispatch channels simulcast the corresponding trunked talkgroups. The police are making the transition to the new system during January. Clinton sector has been selected as the first district to make the switch. Other police districts will follow along with corrections, sheriff and court house security and various municipalities, on their own schedule.
Analog police radios will remain in use as a back-up and the county simulcasts will continue until the county’s new 9-1-1 call center is completed in Bowie in November 2010. At that point, the fire/EMS radio users will switch to the new system as well.
The trunked system is intended for use by public safety agencies only. Schools, public works, etc. will remain on existing radio systems.
Rep. Steny Hoyer, Co. Exec. Jack Johnson, PSC Dep. Dir. Wayne McBride, and Pub. Safety Dir. Vernon Herron were among many officials who attended the official launch of the county’s new public safety radio network on Dec. 7, 2009 (photo by Tom Yeatman).
# # #
THE T-D-M-A DILEMMA!
Loudoun and P.G. shutting-out
scanner radio listeners!
Loudoun and Prince George’s counties became the first jurisdictions to deploy new digital radio technology in the Washington area for use by police and firefighters. Prince George’s County officially launched its new system on Dec. 7. The next day, Loudoun County sheriff switched, followed by the county’s firefighters a week later. Although Prince George’s County already launched its system, the county will start migrating police and then firefighters to the system during 2010.
Scanner listeners, who are unable to monitor the new digital format, most of whom were caught off guard, have expressed concern in online forums such as Scan-DC, RadioReference and thewatchdesk.com.
Unlike the older FDMA (Frequency Division Multiple Access) technology which has been used by public safety for years, TDMA (Time Division Multiple Access) allows for two simultaneous conversations per channel. TDMA has been used by the cellular industry for years, but it is new to public safety. FDMA is commonly known as APCO Project 25 Phase 1 while TDMA is Project 25 Phase 2. But digital scanners only decode FDMA (Phase 1) -- not TDMA (Phase 2).
The Department of Homeland Security has advocated adoption of the Project 25 Phase 2 technology for all state-of-the-art first responder communications systems, says Charles Bryson, director of RCC Consultants. He adds that TDMA technology used in Project 25 Phase 2 is mandated by FCC rules for users of the new 700 MHz spectrum (47 CFR §90.535). Users of 700 MHz must employ TDMA no later than December 31, 2014. There is no current FCC rule requiring users of the 800 MHz band to eventually meet similar TDMA requirements.
In addition to Loudoun and Prince George’s counties, Stafford County plans to deploy a 700 MHz TDMA system and the State of Maryland is accepting proposals for a statewide 700 MHz TDMA network as well.
The standards body developing Project 25 is the Telecommunications Industry Association (TIA).
The Association of Public-Safety Communications Officials (APCO) is the liaison between the public safety community and the manufacturers and is the organization that gave birth to “Project 25.”
Many scanner listeners have expressed concern and are wondering when they can expect a TDMA-capable scanner on the market. Paul Opitz, Uniden product manager, says the current TDMA systems are not confirmed to conform to any standard (other than the proposed Project 25 Phase 2 standard). He says Uniden has no plans to support non-standard systems (unless they happen to be supported as an unintended consequence of providing support for some standard kind of system).
“I think it isn't so much proprietary,” Opitz writes in regard to Motorola’s X2 TDMA technology, as “it’s built around an unratified proposed standard. It [Motorola’s TDMA format] may very well conform to Project 25 Phase 2 in the end, but basing development conditions on that chance could be an expensive dead end.”
There is no guarantee that Motorola’s X2 TDMA will be equivalent to the Phase 2 TDMA standard, and that standard is still a few years away.
What are Uniden's plans regarding Phase 2 system support, once the standard is ratified and systems operating under the standard become operational?
Opitz says Uniden has not announced any plans as of yet. “We typically study operational systems and released standards and then alpha/beta test engineering solutions before making any such announcement,” Opitz noted. He says such efforts typically require three to 18 months, depending on the engineering solution required, noting that firmware-only updates are shorter while firmware with hardware upgrades take longer.
When can scanner listeners expect something to happen? “Once other jurisdictions switch to Project 25 [Phase 2] systems, we will covert to full TDMA/Phase 2,” says Mary Maguire, Loudoun County fire-rescue spokeswoman. “This will also depend on the national finalization and acceptance of the Project 25 standard which is anticipated by 2012,” she added.
As there are no operational systems conforming to the Phase 2 standard which technically only exists as a proposal at this time, Opitz says Uniden is with much of the industry at the “pre-evaluation stage.”
There is one anomaly that may allow at least some scanner listening of the new systems. In an effort to support interoperability, these systems are configuring selected channels to support both TDMA and FDMA. The radio conversations will remain in TDMA mode, unless an older FDMA-only radio is monitoring the talkgroup. In that case, the transmissions will remain in FDMA mode which will allow scanner listeners to monitor. TDMA is preferable for these systems since it doubles the capacity of each voice channel.
Alan Henney may be contacted at email@example.com
# # #