Should Firefighters Reconsider P25?
By Jim Holthaus
Tuesday, June 28, 2016 | Comments
During the past few years there have been updates to the Project 25 (P25) standards, improvements to the P25 vocoder and new P25 products incorporating these updates and improvements. It is a good time to revisit the use of P25 technologies on the fireground, and this article overviews capabilities of specific interest to the fire community.

Some of the benefits of using P25 mission-critical radio equipment include:
• Improved performance in background noise. P25 equipment achieves 10 to 25 decibel (dB) improvements in background noise reduction.
• Tone signaling. Dual-mode multifrequency (DTMF), Knox and single tone are now supported.
• Paging. P25 paging receivers are available.
• Improved coverage. P25 Phase 1 technology is about +7 dB better than 25-kilohertz (kHz) analog.
• Enhanced signaling. Talking party ID, group calls, unit-to-unit calls, all calls, emergency alerts, emergency calls, call alerts, radio check, radio unit monitoring and others are offered.
• Location services. Integrated GPS receivers provide location information.

A Little History
Early deployments of P25 radio products highlighted the challenges of digital voice compression in high background noise. Equipment noise including fire apparatus, personal alert safety system (PASS) alarms and self-contained breathing apparatus (SCBA) presented unique challenges for the P25 vocoder.

Another limitation of early P25 radio products was compatibility with widely deployed paging and tone-signaling systems. The lack of availability of P25 paging receivers was of primary concern with volunteer departments. Given that the original P25 vocoder is optimized for voice, many tone signals such as DTMF, Knox Box or paging tones were highly distorted over P25 radios.

Coverage was another area of concern. While the P25 Common Air Interface (CAI) was designed to provide equivalent or better radio coverage footprints to analog, differences in real-world operation were noted. The digital air interface maintained excellent intelligibility almost all the way to the limits of coverage, but then dropped off rapidly. Analog maintained some level of intelligibility even beyond the edge of coverage, and the gradual degradation was noticeable.

Testing conducted by the National Telecommunications and Information Administration (NTIA) in 2008 reinforced the anecdotal reports of public-safety practitioners with respect to performance in high background noise and reported range issues.

Digital Voice Systems Inc. (DVSI), working with NTIA and P25 equipment manufacturers, went to work to develop methods to test vocoder and air interface performance, determine baseline performance and then set out to implement critical improvements. This effort was conducted under the standards development process of the Telecommunications Industry Association (TIA).

New Developments
Technology improvements within the P25 vocoder, including noise reduction, automatic gain control and advanced error correction coding, were developed, explored and tested to verify that the changes would translate to improvements in real-world fireground scenarios.

The P25 vocoder was also modified to detect most tone signaling common to public-safety systems including DTMF, Knox Box and paging tones. These signals are now detected and encoded by the vocoder for transmission. At the receiver, the subsequent tones are then regenerated to preserve fidelity of the original tone.

The P25 standard now includes a vocoder performance test that measures noise reduction for 15 noises including vehicles (car, boat, helicopter and firetruck), sirens, alarms (PASS and low air), crowds, saws, water pumps, fog nozzle and pink noise.

In parallel, half-rate vocoder technology was developed to support P25 Phase 2 operation, which delivers double the spectrum efficiency of P25 Phase 1 systems. To support interoperability of Phase 1 and Phase 2 systems, a half-rate/full-rate conversion capability is also available.

Available P25 Products
These vocoder improvements, along with other technology to improve performance in high-noise environments typical to public-safety communications such as enhanced noise-cancellation methods, are now available in products using both the full-rate vocoder (P25 Phase 1) and half-rate vocoder (P25 Phase 2).

In addition to vocoder improvements to two-way radio products, a P25 paging receiver was introduced, allowing many public-safety agencies the ability to use existing P25 infrastructure for paging services.

Integration of GPS receivers into handheld subscriber radio equipment coupled with updates to the P25 location services standards provide opportunity to obtain location data during critical incidents. This provides robust operation for units operating outdoors, for example during wildland fire incidents.

2013 Narrowbanding Effects
One additional development affecting radio users in VHF and UHF spectrum was the requirement to narrowband by January 2013. Analog systems are now required to operate on 12.5-kilohertz (kHz) channels. Testing has shown that narrowbanding can have pronounced effects when RF channel impairments and background noise are considered.

P25 offers better range for the fireground in the required narrowband world. P25 Phase 1 technology is about +7 dB better than 25-kilohertz analog and close to +10 dB better than the newly required 12.5-kilohertz analog for the same delivered audio quality (DAQ).

Although P25 has improved coverage over analog and significantly over narrowband analog, concerns with the difference in real-world operation cannot be ignored. A digital receiver generally will provide a good-quality signal to a greater range than an analog receiver and then effectively stop receiving once the range limits are reached.

Typically, in these conditions, the corresponding analog audio is still detectable but is virtually incomprehensible because of the poor signal-to-noise ratio, and thus, it is of little practical use. Technically, the analog signal may have greater range but may have a significantly smaller useful range. When considering a possible conversion to using P25 for the fireground, it is strongly encouraged to do a detailed evaluation of RF coverage performance on your system to ensure that buildings will be properly covered, especially on the fringe of a system’s operational area.

P25 radios are just one of many communications technologies available to meet the demanding needs for fireground communications. The latest P25 radios are well equipped to address mission-critical communication challenges for fireground operations. If you have not evaluated P25 technology for use on the fireground in the past few years, now may be a good time to take a comprehensive look and see if the performance and features of current P25 equipment are an improvement compared with your current solution.

More information on P25 vocoder and range improvements can be found here.

The Project 25 Interest Group (PTIG) original white paper is here. Visit the PTIG website for more P25 information including a list of P25 systems around the globe.

Would you like to comment on this story? Find our comments system below.


Jim Holthaus is vice president Project 25 (P25) solutions for Relm Wireless. He has been active in the development of LMR products and P25 digital radio standards since 1993. Holthaus is a senior member of the Institute of Electrical and Electronics Engineers (IEEE), a member of the Association of Public-Safety Communications Officials (APCO) International and vice chair of both Project 25 Interest Group (PTIG) and the Telecommunications Industry Association (TIA) private radio section. He’s also a chair of the TIA-TR8.25 Compliance Assessment Formulating Group TIA/APCO P25 Interface Committee (APIC) Vocoder Task Group and has chaired the TIA/TR8.4 Vocoder and TIA/TR8.10 Trunking Subcommittees.



 
 
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Comments
On 6/29/16, Burch Falkner said:
Excellent article by Jim Holthaus. Informative, positive and factually correct. We need more of this kind of information. However, there is always another side to any story.

There is always the overriding issue to any suggestion of advancing technology and that is MONEY. Putting a $2,000 radio on a volunteer firefighter or even paid firefighters just doesn t make economic sense. Most municipalities and virtually all volunteer organizations simply don't have the funds to purchase and maintain P25 radios or $1,000 pagers, which brings me to another point.

Few purchases are made on the basis of cost of ownership. There is a BIG difference between purchase price and cost of ownership. The typical flat rate repair on a P25 radio is close to $500. Batteries can easily cost over $100, and the list goes on. And then there is the issue of managed system infrastructure, whereby the base repeater stations are owned by an equipment provider. Such systems require a monthly subscriber fee ranging from $8 to $42 PER RADIO and the user/subscriber has no alternatives or guarantees that the cost will not increase at the sole discretion of the infrastructure system provider.

While the comments regarding range, audio quality, etc., are all correct, the fact is that most fire communications are conducted on the scene where the range requirement rarely exceeds 1,000 feet. At close range, analog sounds just fine. As a matter of fact it sounds BETTER than any vocoder I've ever heard.

The hard reality is that an excellent high-quality MIL-SPEC analog portable can typically be purchased at one-tenth of the cost of a comparable P25 radio. With this being said, there is a need and a place for both analog and P25. For local area operations, analog is still the best choice. However, there is a need for interoperability using a common standard, which is P25.

Unfortunately there is the question of which P25 is it — Astro25 or open standard P25 — and in what frequency band. 700 MHz is the supposed standard but there are also VHF and UHF P25 systems and then we have to deal with Phase 1 and Phase 2. It gets a little confusing for us common folk.

In my hometown, we have two county municipal public-safety networks. One is 800 MHz analog and the other 700 MHz digital, both provided by the same manufacturer with maintenance required to be performed by a single dealer. One brand, one dealer. That's the way things were intended to be, or is it? Apparently it is as is evidenced in virtually all major cities in Alabama.

So what happened to the dream of interoperability with lower prices brought about by free market competition? THIS is where the problem is. P25 was and is a great technology. Unfortunately, the benefits have been hijacked from those who would have been the beneficiaries. There are exceptions. The state of Mississippi is one. There are others but not enough. That is why I suggest an alternative.

We call it a BlueBox. It costs less than $1,000, and a single BlueBox connected to any P25 vehicle radio provides the ability for ordinary analog radios to communicate on P25 networks just like they are real P25 radios.

On average we assume eight firefighters to be on the scene of a typical event.
Using P25 we would assume one vehicle radio at $2,500 and eight firefighter radios at $2,000 each for a total of $10,500. BlueBox would be about HALF the cost of all P25 radios without even considering the cost of maintenance, batteries or subscriber fees.
This is why P25 is in trouble. Still I enjoyed by the article by Mr. Hilthaus. As our neighbors to the north and the east would say, He is spot on. Unfortunately, other factors are controlling the growth and acceptance of P25, in particular in the firefighting community. There is also the uncertainty of the real impact of Long Term Evolution (LTE) and even technologies not yet public. It's kind of tough to make a long-range decision these days. The best we can hope for is to get the best value for our investment based on present day dollars and technology.

On 6/29/16, Andrew Schwartz said:
Burch hit nail on head. Why can I buy an excellent Digital Mobile Radio (DMR), TETRA or NXDN radio — all robust digital technologies — or an analog radio for $500 that will hold up great and meet the needs of most public-safety first responders. Yet I have to pay $1,000, maybe $2,000 for a Project 25 (P25) radio. Certainly P25 technology is no more difficult to implement than some of the other very robust digital technologies used today. Local public-safety first responders in my area are looking at DMR. It provides the same capacity as P25 Phase 2 plus analog for interoperability. That's what's used — not digital — FOR A FRACTION OF THE PRICE. Something's very wrong with this.

On 6/29/16, Tony Arce said:
Mr. Falkner, with all due respect, these are my points of view in reference to your comments.
Basic Project 25 (P25) handheld radios from most manufacturers average price today is $1,200.
It is understandable that it is still expensive for a volunteer fire department but a way around that expense is that the fire department itself can buy the radios through a grant like UASI, which supports the purchase of P25 radios, or AFG.
If the fire department owns the radio system then there is no per-radio fee unless they want to fund maintenance through fees — that is a different story.
Certainly there are radios that cost even less than one-tenth of a P25 radio like the dual-band Baofeng radios made in China that you can buy on Ebay for about $25 a piece that come with an LED flashlight built in and an emergency beacon. Now the question is, would you put the life of a volunteer firefighter on a $25 disposable radio?
Batteries are not specifically made for P25 radios. The actual chemistry dictates the price of the battery plus the option of being intrinsically safe or standard.
Analog conventional has always been the best way for interoperable communications as long as you are not operating on a trunked propietary format system.
As for P25 which one to use?
The P25 standard is one standard named by one company as Astro25 but still meets all requirements of the standard as long as you don t use ADP encryption, which is not part of the standard. If you choose to use ADP then you are tied to that manufacturer.
All manufacturers make and meet the P25 standards as written, and they are rigorously tested by the CAP.
Which band to use?
VHF and UHF are obviously less expensive than 700/800 MHz.
Which phase to use?
It is always better to have a Phase 2 system rather than having a Phase 1 that you will have to upgrade later.

On 6/29/16, Gerald Marsh said:
Our fire department's 700 MHz digital radios cost more than $3,000 on the bulk order. If the department wants to add a radio, then the cost approaches $8,000 per radio, mobile or portable. Mutual-aid departments are still analog VHF because of the cost and lack of coordination among the four counties. Our radios were funded by a sales tax increase with only one vendor providing sales and service. I question the quality of the Phase 2 700 MHz digital and prefer analog.

On 6/29/16, Janet said:
Great information Jim. Thanks for pulling it all together in an interesting format.

On 6/29/16, Jim202 said:
The post and all the comments are right on. But one down side to using a Project 25 (P25) trunking system on a fire scene can be a major problem with coverage. They just installed a brand new P25 trunking system here on 700 MHz. Street coverage is great. But there are some buildings that the new system will not allow portables to be functional inside of.

Take for instance one of the buildings is the main fire station for one of the district departments. There are other buildings that are commercial use. These metal buildings act like an RF shield. If the tower site isn't really close, you don t get anything inside of them.

So now you are forced into using some kind of building active antenna system like a bidirectional amplifier with internal antennas around the building. This adds considerable cost to the building owner.

If you use some simplex frequencies, you have a much better chance of maintaining communications with the active users inside the building. But in asking various departments in my travels around the country, most fire service people seem to have the idea that changing channels to a dedicated fireground channel is too much of a problem.

I can't change people's ideas or mood but having them take this stand, you're not going to have good on-scene communications between every one there.

As the saying goes, You can lead a mule to the water tank, but you can't make them drink." It seems many in the fire service are acting like a mule and don't want to make any changes.

I would rather stay on a VHF radio system because it doesn't have the problems the higher frequencies have with in-building penetration. How we solve the problem here is a good question. The bottom line is training on the use of the radios and providing a simplex option to be used on scene. Good luck trying to get people to use it.

Bottom line is there are solutions to building penetration. But politics and old habits are hard to break. Then add into that picture the ability to communicate with mutual aid with people that were called to the active scene. Not a good clear picture when the management in many cases take the "not in my back yard" attitude toward communications.

On 6/29/16, KJ Hooper said:
There is now a P25 voice pager available. The G5 voice pager is dual band VHF/700-800 MHz or UHF/700-800 MHz and prices in the $700 range. Made by Unication USA and is being used on MPSCS system in Michigan and the MARCs system in Ohio.

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