Mission Critical organizations around the world have
P25 PHASE 1 OR P25 PHASE 2?
been upgrading to P25 for more than two decades.
But there remain some big questions: 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 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 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 6.75kHz equivalence.
P25 Phase 1 is available as both a conventional network and
a trunked network, but 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
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 Over-the-air programming (OTAP).
Trunking can be initially frustrating for users, who need to wait
for permission to talk. On busy networks however, wait time is
shorter than conventional because they have access to more
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
• 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
• During an emergency you can stop radios from transmitting
to free up channels.
Interoperability with neighboring
Efficient use of frequencies
Digital audio quality, to the edge
Encryption for protected
Specific Public Safety features
Open standards that promote choice
and price competition from different
6GOOD REASONS TO MIGRATE TO P25