SMR - MPT1327 is the favorite choice
An introduction published by the North American MPT1327 Manufacturers Association (www.mpt1327-usa.org)
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
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.
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
easy to use at affordable prices. Users do not care about the technology.
The only issues visible to users are reliability, speech quality, size,
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
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.
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)