PROGRESS BEYOND THE STATE-OF-THE-ART
CURRENT PPDR COMMUNICATION NETWORK ARCHITECTURE
LANDSCAPE
PPDR organizations currently use a range of different communications networks to
meet their operational needs. In Europe, the majority of their personnel now use
dedicated networks to provide narrowband mobile communications using TETRA
or TETRAPOL technologies operating in the 380-400 MHz band. This spectrum al-
location is based on the harmonization of spectrum for public safety that was put in
place by the ECC in 1996 and provides recommendations on the harmonization of
additional frequency bands for digital PPDR within the 380-470 MHz range. There
are significant barriers to the implementation of this decision as the same spectrum
is also identified for narrowband and wideband digital land mobile (PMR/PAMR).
264
CHAPTER 18
Evolution of TETRA
In nearly 20 countries, the presence of CDMA 450 networks will impact on the
availability of this spectrum for PPDR organizations. Interest is also emerging in the
commercial deployment of LTE technology in this band.
Recent years have seen increasingly rapid progress in the capability of technolo-
gies deployed in the commercial electronic communications sector, particularly with
regard to over the air data rates and the spectrum efficiency that can be achieved. For
example, when the first 3G technology standards were agreed in 1999 the maximum
bit rate realizable over a 3G mobile network was 2 Mbps, though in practice most
users experienced speeds in the range 64-384 kbps. By comparison the digital tech-
nology mainly deployed by the PPDR sector (TETRA) could deliver up to 28 kbps.
Many of today’s 3G networks have been upgraded to the latest High Speed Packet
Access (HSPA, HSPA
+
) technology and can theoretical peak bit rates of up to 21
Mbps (one user per cell only, best case channel, no error protection), with actual
user bit rates of 1 Mbps or more in case of several users relatively commonplace
in some networks in high density traffic areas, using a 5 MHz bandwidth channel.
Newer systems employing such standards as the TETRA Release 2 TEDS compo-
nent are capable of supporting more advanced data communications, with a theoreti-
cal maximum IP throughput of up to 500 kbps in a 150 kHz channel; however there
is an increasing gulf between the capabilities of commercial networks and dedicated
PPDR networks, as the increasing demands to support broadband data require more
spectrally efficient technologies to be developed and implemented faster for the com-
mercial sector.
Despite improvements in spectral efficiency through the deployment of new tech-
nologies which will yield some relief to the spectrum shortage, demand growth for
frequencies is likely to outstrip growth of supply into the foreseeable future. The
spectrum available to existing PPDR operations will not satisfy future needs for these
essential services. One example of this is the current situation with TETRA TEDS in
that not all EU Members States are able to identify radio channels. Therefore, com-
munications policy must evolve to empower new systems by reallocating spectrum
from the Digital Dividend to PPDR mission critical communications. This decision
is not to be taken lightly since it sits on the critical path for numerous other deci-
sions necessary before deploying next-generation PPDR networks. Historically, it
has been the usual practice to identify suitable spectrum well in advance because of
the timescales for releasing the spectrum, development of standards and equipment.
It may require as long as 10 years to plan and deploy such networks. Adding to the
urgency of the matter is the growing need for new services to emerge due to the in-
crease in terrorist threats, frequency of natural environmental disasters, and normal
population growth. The 450-470 MHz band is also widely used in Europe by analog
private mobile radio services which in some cases (notably UK and Ireland) are not
aligned with relevant CEPT recommendations and it seems unlikely that sufficient
harmonized spectrum to support broadband mobile operation could be made avail-
able in a reasonable time frame.
In practice, many PPDR users already make use of commercial 3G networks
alongside their own dedicated networks; however, the coverage of the commercial
Do'stlaringiz bilan baham: |