There are undoubtedly some very strong reasons why mission critical organizations should migrate to P25, but the many options can make it difficult to know which route to go. In this article, Tait Architectural Design Engineer Steve Penny discusses the differences between these standards, helping you to decide what’s right for your organization.
Mission Critical organizations around the world have been upgrading to P25 for more than two decades. But there remain some big questions to answer: Should we choose P25 Phase 1 or Phase 2? Trunked or Conventional? Do we really need P25, or should we stick with Analog?
P25 Phase 1 or P25 Phase 2?
P25 Phase 1 was the original P25 standard, and while it may be older than P25 Phase 2, that doesn’t mean it’s the wrong choice. It all depends on what you need.
The biggest difference between Phase 1 and Phase 2 is that Phase 1 uses Frequency Division Multiple Access (FDMA), where the channel efficiency comes from dividing the frequencies. Phase 2 uses Time Division Multiple Access (TDMA) which divides the channel into two timeslots. Phase 1 bandwidth is 12.5kHz. But if you choose P25 Phase 2 and TDMA, then there will be two voice channels for every 12.5 kHz of spectrum – effectively giving you 6.25kHz equivalence.
P25 Phase 1 is available as both a conventional network and a trunked network, but P25 Phase 2 is trunked only. So if you are committed to a digital conventional solution, Phase 1 is the way to go. But before making that decision, let’s compare P25 Phase 1 Conventional and P25 Phase 1 Trunked.
P25 Phase 1 Conventional
- P25 Conventional offers the benefits of digital radio with the simplicity of conventional operation. Upgrading to Phase 1 gives you the security of digital encryption, and voice quality right to the edge of coverage.
But the big benefit of conventional radio is that it costs less than trunked and is easier to operate. However, if your organization is approaching 100 or more radio users, a conventional network can quickly become too congested, and you will want to consider a trunked network.
P25 Phase 1 Trunked
FDMA means each trunked channel uses the full 12.5 kHz spectrum, but trunking has some serious benefits that P25 conventional cannot offer:
- Fewer channels can support the same number of users
- Person-to-person calls are private
- IP interface on the infrastructure – ease of data integration such as OTAP
Trunking can be initially frustrating for users, who need to wait for permission to talk. However, for busy networks, wait time is shorter than conventional because they have access to more channels.
P25 Phase 2 Trunked
The primary reason you should migrate to P25 Phase 2 is for spectral efficiency. If you need more channels, but don’t have the spectrum available, then you can take advantage of the TDMA technology in P25 Phase 2.
Time Division provides two virtual channels for each 12.5 kHz logical channel. While this adds some complexity, it delivers some real benefits.
- Effective double channel capacity from P25 Phase 1 future-proofs you against loss of spectrum
- Because the control channel is a 12.5kHz FDMA channel, Phase 2 is backwards compatible with P25 Phase 1
- You can stop radios from transmitting to free up channels during an emergency
For many mission critical organizations, this could still be your best choice. Undoubtedly, P25 is more advanced, but there is no point in paying for more features if you simply don’t need them.
Here are some reasons to consider Analog Conventional:
- Analog Conventional costs less than P25 Digital,
- If paging system is essential to your operation, this functionality works better with analog conventional,
- Neighboring agencies have analog mutual aid channels,
- Your users are familiar with analog conventional.
If you’re leaning towards an analog conventional system, your best option is to select one that is future proof. TaitNet Analog Simulcast-over-IP hardware is P25-capable, so if you need to migrate to P25 in the future, it will be a very simple upgrade. All you’ll need to do is upgrade the software and feature licenses. One solution may be some analog channels and some P25 conventional channels to get the best of both worlds
Which is right for your organization?
Capacity remains the biggest issue for many operators, and the highest capacity solution is a digital one, that being P25 Phase 2 Trunked. Beyond that, the decision becomes more complex. P25 Phase 1 – conventional or trunked – remains the best option for most organizations looking to go digital. Unless you are dramatically short of capacity (and additional channels in your frequency range are unavailable), any other argument for choosing Phase 2 is outweighed by the complexity and cost.
On the other hand, if you are already using P25 Phase 1 Trunked and you need more capacity, then Phase 2 is the best way to achieve it.
As always, whatever you choose, we recommend selecting a solution with a clear and easy migration path. For instance, the Tait 9400 series is capable of Analog, P25 Phase 1, and P25 Phase 2, so whatever you choose today, you’ll be ready for tomorrow’s changes.
Each organization has unique needs and wants, and at the end of the day, you need to do what is best for your staff and community. So it’s wise to seek the advice of a trusted consultant or communications provider.
This article is taken from the latest issue of Connection Magazine. Read the full piece here. And if you like our articles, subscribe to Connection to be the first to know when new issues are released!