SMR - MPT1327 is the favorite choice
An introduction published by the North American MPT1327 Manufacturers Association (www.mpt1327-usa.org)
Abstract
Technology is moving faster than the man in the street can comprehend. Although
the contemporary writers correctly predicted space travel, satellites and
other technical wonders in the 1950’s, the cellular handset was
never foreseen. Some technologies such as VHS, iDEN, have become household
names,
but there
have been many casualties on the way that have been forgotten.
This paper analyses SMR from the user’s perspective, and then describes
a mature Open Standard Protocol for SMR radio networks that is now established
in over eighty five countries of the world.
Introduction
In evaluating the needs of users, the industry must heed that mobile communications
is not the primary business of SMR users. Rather it is just another
tool to help them efficiently and effectively run their company. Equipment
must
be
easy to use at affordable prices. Users do not care about the technology.
The only issues visible to users are reliability, speech quality, size,
price and
battery life. (coverage becomes important after the sale).
The regulator is now mandating that SMR systems are spectrum efficient.
This naturally leads down the path of some kind of trunking for our
modern networks.
The trunking concept is not new: it was first developed in the 1970’s
to improve the use of this finite resource. When channels are scarce and
traffic is high, operators need to maximise the use of the spectrum while
maintaining
a high grade of service. The modern radio trunk technology addresses the
spectrum issue and at the same time provides a platform for a wide range
of facilities
for users. (Spectrum efficiency is of advantage only to the regulator and
the network operator who needs spectrum to offer services to the end user).
Modern
trunked networks accommodate an extensive menu of speech and data call
types, which can be connected over a wider geographical coverage area than
most
conventional SMR mobile radio systems.
The only issues visible to the end-users are reliability, speech quality,
price, battery life, style. (and later coverage) MPT1327 is a radio
trunking open standard developed by the UK radio industry and has become
a de-facto international standard that uses
digital technology
for air interface signalling (such as call set-up), but retains analogue
voice for the speech traffic. The standard may be downloaded from
the North American
MPT1327 manufacturers association website at www.mpt1327-usa.org.
MPT 1327 is now in use in at least 89 countries. It offers fast call
set-up, priority and emergency calls, and is fully scaleable from
one channel to a
national network.
MPT1327 is low cost and simple to operate. In many cases existing
analogue repeaters may be upgraded to MPT1327.
MPT1327 supports conventional SMR markets. Fleets may be radio
to radio or dispatcher based. Dispatchers may be radio or line
connected
Group
Call, Broadcast
Calls, Dynamic Regroup and Late Entry and a range of data transmission
is offered on all modern equipment.
MPT 1327 Trunking Standards MPT trunking is now an established and mature
technology around the world. Manufacturers in this market recovered their
development
costs
at a time
when competition was not so severe. The cost of MPT infrastructure
and terminals can now meet the most stringent financial targets.
The capital
cost for complete
MPT base station site (controllers, R.F base stations, R.F combining,
antennas) currently stands at less than $100 per user. Portable
terminals can be
bought for less than $400. Small private organisations needing
radio communications and only a small chequebook find MPT very
attractive.
Until digital SMR
technology
finds the economy of scale to reduce prices, MPT will continue
to find new markets. Of course if any new technology is highly
complex,
potential
manufacturers
may not be prepared to fund the enormous development costs. If
this restricts the number of global players, competition may
be stifled,
and prices
remain high. This ‘chicken and egg’ situation where
low prices require mass markets, but mass markets require low
prices must be broken by reaching
a critical mass.
MPT1327 boasts a choice of 20 infrastructure manufacturers and
at least 18 terminal manufacturers around the world. Customers
have
choice,
aggressive competition keep prices low and quality high.
In areas of the world where the fixed telecommunications structure
is very limited or non-existent, MPT1327 systems have been a
great success.
Examples
include oil pipelines, rail routes and road transport routes.
Many of the roadside emergency telephones in remote areas in
the Far
East are
in fact modified MPT
terminals.
Data developments in MPT1327
There is a wide difference in the take-up of data around the
world. In some countries such as South Africa, the data transactions
account
for
60% of the
control channel loading. This is a mix of dispatcher forwarding
of jobs and GPS data for vehicle tracking
Taken as a whole, the type of data user that was expected, has
not materialised. What is most popular is the forwarding of small
data
items from units
that collect information remotely. The most widely used application
is GPS vehicle
location. It is possible to procure the MPT radio, GPS receiver
and antenna for less than $500.
What has not significantly materialised is the transmission of
long strings of data. Maybe this situation will change through
new recent
interest
in EMAIL and the Internet.
The MPT1327 standard only prescribes how the data messages are
formatted at the air interface. There was not corresponding access
interface
protocol. In
1994 however an access interface document was produced called
MAP27. This enabled data applications to interface with compliant
radio
terminals independent of
radio manufacturer.
Migrating Users to MPT1327
There are still hundreds of thousands of users in Europe who
use conventional SMR dispatcher radio systems and Community Base
Stations.
There is
a benefit if existing channel resources can be shared during
the transition from conventional
to trunking. At least one MPT manufacturer has a facility whereby
a traffic
channel can be shared with a CBS or conventional channel. The
system can be programmed to statistically favour either the trunking
or
conventional use
of the channel. As users migrate the odds can be adjusted away
from conventional use. The UK regulator now has a policy to migrate
CBS
users to trunking.
Incentives from the regulator include many kinds channel swaps
and bartering.
Providing Bridges to MPT1327
It is very desirable if an MPT network can bridge to other systems.
Bridges and interfaces are known for the following –
• Smartnet Trunking
• DID Exchanges
• Internet EMAIL server
• X25
Conclusion
In evaluating the MPT1327 networks, the public and private networks must
be considered separately. The operation of any public Network is
fundamentally different to a private system. In a public network, priority
or
emergency access is difficult or impossible since relevant users will
demand performance
that
statistically cannot be guaranteed. In addition there is
always an impact on other users who may be the victim of pre-emption. One
of the
first generation
U.K networks failed to restrict emergency access and soon
paid the
price. Users
soon learned that if a call was queued during busy periods,
an emergency call got though. It was not long before the initial step of
a normal
call
was bypassed,
so the whole pre-emptive mechanism was doomed. The operation
of first generation trunked networks have certainly provided the know-how
and experience
that will
have a direct bearing on the topology and management of the
latest generation of SMR networks.
Manufacturers have often been criticised that the styling of traditional
and trunked PMR terminals have always been different (and
substandard) to that
of cellular. This has however differentiated the products.
If the manufacturers adopt ‘cellular’ like styling on public
networks, there is a danger that the users will expect the terminal
to behave like cellular
both
in terms
of operation and coverage.
In recent years, markets for regional systems have been maintained,
and, although MPT1327 was never designed for the emergency
services, some
very successful
networks have been built.
MPT1327 equipment has developed wide and varied applications
through its rich menu of facilities. It is unlikely that
any new large
public networks
will
be installed in Western Europe, but private systems with
a coverage area of a small number of sites are still in the
manufacturer’s
order books, replacing old conventional SMR systems.
Outside Western Europe the market continues to be stable.
Cellular still cannot meet constraints where fast call set-up
and prioritising
of calls
is mandatory.
In many areas of the world, the local environment restricts
choice. Requirements are often –
Lowest cost per user
Restricted or non-existent fixed links to connect the sites
Limited engineering staff/expertise
Varied use including emergency and ‘cellular like’ services
Wide choice of manufacturers equipment
Technology step is modest from conventional systems
Today, only MPT1327 can meet these criteria. Unless digital
trunking reaches the critical mass where the cost of the
equipment will
substantially fall,
MPT1327 will continue to be an important and useful technology
for many years.
APPENDIX
MPT1327 Standards
The MPT1327 specifications actually comprise four documents – MPT1327
defines the message and modulation format: MPT1343 is an access interface document
for terminals: MPT1347 is an access interface for base stations: MPT1352 is
a test document for terminals.
The MPT specifications were not designed as an international standard. They
were developed for the U.K market to make efficient use of a block of spectrum
released from the closure of VHF television transmissions. The British Ministry
of Posts and Telecommunications (now the U.K Radio Agency) sponsored the
drafting of the MPT Standards through the formation of the MPT1327 Drafting
Group. This
group was represented by manufacturers, and other professional bodies representing
particular interests, including transport, fuel and power, and later, Network
Operators. Because MPT1327 is an open standard, equipment from different
manufacturers can operate seamlessly – both terminals and infrastructure.
The fact that this was a truly open standard was a catalyst for its rapid
growth. A variety of manufacturers’ equipment became available for both network
infrastructure and terminals. This competition stimulated quality, functionality
and most importantly, price. As early as 1990, MPT systems had been commissioned
as far as Australia and Siberia. By 1993, regional and national systems were
in place in Europe, including Germany, France, Netherlands, Italy and Spain.
In the global arena, regional networks were installed in most continents. Today,
over 84 countries are known to have installed MPT systems. At least 16 independent
manufacturers offer MPT infrastructure and 18 companies manufacture MPT terminals.
MPT 1327 Features
When the MPT Standards were first published, manufacturers were under pressure
to roll out their networks. The first generation MPT networks offered simple
half duplex speech calls, single site or wide area: single site group calls:
limited PSTN/PABX: and status messaging. Further development followed and
by 1992 most networks and terminals offered a wide range of features including –
•
Call Types
•
Individual Speech Calls to
? Mobile subscribers
? Line connected services – PABX/PSTN
•
Call priorities, normal high, emergency
•
Group Calls
•
Single Site
•
Wide Area Multi-site
•
Call Diversion
•
Pre-emptive emergency calls
•
Late Entry Groups
•
Short Message Service
•
Channel Segregation
The features where MPT trunking can have a strong advantage over other formats
including cellular are –
•
Instantaneous call set-up. (The fastest call set-up speed for MPT is actually
just over 200mS for groups and just over 400mS for single prefix speech calls.
•
Prioritising of calls. (Priority and Pre-emptive emergency access is essential
in security and emergency environments.)
•
Some manufacturers offer sharing of channel resource with other systems. (A
traffic channel can be shared with a conventional channel. (for example such
a channel may already be in use for a community base station).
•
Site backup power. (For Emergency services, 48-hour backup is often essential
)
•
Groups and wide area groups. (Wide area groups encompass a specified number
of sites. Wide area groups allocate a traffic channel on more than one site.
The Network keeps a map in its database of the sites to be allocated.
•
Open Channel Working
•
Dispatcher operation
•
Line connected dispatchers were designed into the first generation MPT networks.
By far the most popular today is radio-connected dispatcher.
•
Virtual User Groups (Virtual user groups are groups of terminals that have
exclusive use of a number of traffic channels. Independent Network Operators
may share a single control channel)
•
Local PSTN. (A PSTN interface at a site (or group of sites) is a very important
feature in countries where fixed telecommunications is sparse or unreliable.
The Network uses some criteria such as number of dialled digits to determine
if the call will be routed to the local connection or the central call router.)
•
Selectable Individual Groups. (The user can enter a group identity into the
terminal to define a new group to which that terminal will belong.)
•
Dynamic Regrouping
•
The Network has the ability to transmit a new group definition to a radio terminal
•
Remote Stun/Unstun (the Network has the ability to disable a radio terminal
remotely)
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