MPT-1327
Encyclopedia
MPT 1327 is an industry standard for trunked radio communications networks.
First published in January 1988 by the British Radiocommunications Agency, and is primarily used in the United Kingdom, Europe, South Africa, New Zealand, Australia and even China. Many countries had their own version of numbering/user interface, the most notable being MPT1343 (UK), Germany – Chekker (Regionet 43), France – 3RP (CNET2424), Belgium
& The Netherlands – Entropia Networks (MPT1343), Australia
– Multiax, China -Gong An.
MPT systems are still being built in many areas of the world, due to their cost-effectiveness. The equipment is cheap and performs very well.
trunked radio standard was developed by the European Telecommunications Standards Institute
(ETSI), as a digital alternative to analogue trunked systems. However, TETRA, with its enhanced encryption
capability, has developed into a higher tier (public safety
) product, currently mainly used by governments, some larger airports and government-owned utilities. TETRA equipment is getting cheaper all the time and may eventually compete with MPT 1327 at the same price-point, but this has not yet happened. DMR (digital mobile radio
), and dPMR (digital private mobile radio) are more recent ETSI-standards for digital mobile radio using two-slot TDMA
and FDMA respectively. The Tier 3 standard for these systems defines a trunking protocol very similar to MPT1327 and is intended as a potential migration path for existing and perhaps future trunking customers. Tier 3 equipment is (late 2011) now becoming available, so the impact on TETRA and MPT 1327 is yet to be seen, but may well be significant.
scheme that requires a far higher Signal to Noise ratio to function than 1200bit/s FFSK signalling.
Systems based on MPT 1327 only require one, but usually use two or more radio channels per site. Channels can be 6.25 (Entropia Networks in BeNeLux) 12.5 or 25kHz bandwidth. At least one of these channels is defined as the control channel (CCH) and all other channels are traffic channels (TCs) used for speech calls.
A typical installation will have around 6-10 channels. A 7 channel trunk, correctly engineered, is capable of handling in excess of 3000 mobile units. The capacity of the system increases dramatically with the number of traffic channels. For example, 1 traffic channel with queuing can not handle many customers, perhaps 2 minicabs with 20 mobiles. In effect this would be a CBS with queuing. However, a 7 channel trunked system can handle 40 minicabs with 20 mobiles with ease. The Erlang
formulas are typically used for calculating system capacity.
A spectrum efficiency advantage over a 4-slot TDMA system like TETRA is in areas where a low-traffic network is required. The absolute minimum TETRA installation would require one carrier, carrying one CCH and three traffic channels, using up 25kHz of bandwidth. The absolute minimum MPT1327 assignment is a single non-dedicated control channel, utilising 12.5kHz, in most cases.
A non-dedicated control channel can be used as a traffic channel when all the other traffic channels are busy. This can be useful if the site is part of a multi-site network and has a very low traffic profile as the site could have a single channel rather than at least two freeing up one channel for use elsewhere. The disadvantage is loss of queuing, and data cannot be sent on the control channel whilst it is in traffic mode. A non-dedicated CCH should not be used as a "reserve tank" for a busy site as the lack of signalling will seriously affect the operation of the site.
frequency modulation
. Data messages between mobiles and the network are exchanged on the control channel at 1200 bits per second using FFSK signalling, or a specific "modem call", known as "non-prescribed data" can be established, whereby free-form 1200 baud data can be exchanged on a traffic channel without tying up the control channel. With the use of special modems, the speed can be 19,200 bit/s. This, along with Short Data Messaging and Status Messaging via the control channel makes an MPT1327 network ideal for managing AVL for asset management
, meter reading
and SCADA
networks, the advantage being that the network can be used for this sort of application whilst still carrying voice traffic.
For the duration of his call a subscriber is exclusively allocated a traffic channel from the available pool. If all channels are occupied, the call will be queued. If the control channel has become a traffic channel, like in the case of a non-dedicated control channel, the call will be queued in the radio, although radio queuing loses the first come, first served effect, so if there are seven units queuing, the last unit to queue may get a traffic channel first.
Broadcast calls can be used to make announcements to the entire customer base on a trunked system. For example, if work is to be carried out on the trunked system, the owner of the system can initiate a Broadcast Call which calls every mobile on the system. However, the mobiles may not have talk entitlement, so the PTT may not work. By this means the owner can announce to all customers a short period of inoperation due to maintenance.
First published in January 1988 by the British Radiocommunications Agency, and is primarily used in the United Kingdom, Europe, South Africa, New Zealand, Australia and even China. Many countries had their own version of numbering/user interface, the most notable being MPT1343 (UK), Germany – Chekker (Regionet 43), France – 3RP (CNET2424), Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
& The Netherlands – Entropia Networks (MPT1343), Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
– Multiax, China -Gong An.
MPT systems are still being built in many areas of the world, due to their cost-effectiveness. The equipment is cheap and performs very well.
Digital alternatives
The TETRATetra
thumb|right|250px|Pristella tetra — [[Pristella maxillaris]].thumb|right|250px|Golden Pristella tetra, a [[morph |morph]] of [[Pristella maxillaris]].thumb|right|250px|[[Silvertip tetra]] — Hasemania nana....
trunked radio standard was developed by the European Telecommunications Standards Institute
European Telecommunications Standards Institute
The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...
(ETSI), as a digital alternative to analogue trunked systems. However, TETRA, with its enhanced encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
capability, has developed into a higher tier (public safety
Public Safety
Public safety involves the prevention of and protection from events that could endanger the safety of the general public from significant danger, injury/harm, or damage, such as crimes or disasters .-See also:* By nation...
) product, currently mainly used by governments, some larger airports and government-owned utilities. TETRA equipment is getting cheaper all the time and may eventually compete with MPT 1327 at the same price-point, but this has not yet happened. DMR (digital mobile radio
Digital Mobile Radio
Digital mobile radio is an open digital radio standard for professional mobile radio users specified in the European Telecommunications Standards Institute Standards TS 102 361 parts 1 to 4 and used in products sold in all regions of the world. The applicable ETSI compliance standards are EN 300...
), and dPMR (digital private mobile radio) are more recent ETSI-standards for digital mobile radio using two-slot TDMA
Time division multiple access
Time division multiple access is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This...
and FDMA respectively. The Tier 3 standard for these systems defines a trunking protocol very similar to MPT1327 and is intended as a potential migration path for existing and perhaps future trunking customers. Tier 3 equipment is (late 2011) now becoming available, so the impact on TETRA and MPT 1327 is yet to be seen, but may well be significant.
MPT1327 advantages and features
The advantage of MPT 1327 over TETRA is the increased availability, lower cost of equipment, the ease of installation, the familiarity with the equipment, and many believe that MPT 1327 is superior to TETRA, due to its uncompressed FM audio, and greater receiver sensitivity. MPT1327 control channel signalling is more resilient, since the TETRA protocol uses a complex modulationModulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
scheme that requires a far higher Signal to Noise ratio to function than 1200bit/s FFSK signalling.
Systems based on MPT 1327 only require one, but usually use two or more radio channels per site. Channels can be 6.25 (Entropia Networks in BeNeLux) 12.5 or 25kHz bandwidth. At least one of these channels is defined as the control channel (CCH) and all other channels are traffic channels (TCs) used for speech calls.
A typical installation will have around 6-10 channels. A 7 channel trunk, correctly engineered, is capable of handling in excess of 3000 mobile units. The capacity of the system increases dramatically with the number of traffic channels. For example, 1 traffic channel with queuing can not handle many customers, perhaps 2 minicabs with 20 mobiles. In effect this would be a CBS with queuing. However, a 7 channel trunked system can handle 40 minicabs with 20 mobiles with ease. The Erlang
Erlang
Erlang may refer to:* Agner Krarup Erlang , a mathematician and engineer after whom several concepts are named** Erlang , a unit to measure traffic in telecommunications or other domains...
formulas are typically used for calculating system capacity.
Spectrum efficiency
Whilst MPT 1327 systems do not employ digital speech processing to allow some Spectral Efficiency (voice channels per 6.25kHz), there are several methods used that increase the Spectrum Efficiency (Erlangs per square kilometre, per 6.25kHz).A spectrum efficiency advantage over a 4-slot TDMA system like TETRA is in areas where a low-traffic network is required. The absolute minimum TETRA installation would require one carrier, carrying one CCH and three traffic channels, using up 25kHz of bandwidth. The absolute minimum MPT1327 assignment is a single non-dedicated control channel, utilising 12.5kHz, in most cases.
A non-dedicated control channel can be used as a traffic channel when all the other traffic channels are busy. This can be useful if the site is part of a multi-site network and has a very low traffic profile as the site could have a single channel rather than at least two freeing up one channel for use elsewhere. The disadvantage is loss of queuing, and data cannot be sent on the control channel whilst it is in traffic mode. A non-dedicated CCH should not be used as a "reserve tank" for a busy site as the lack of signalling will seriously affect the operation of the site.
Time-shared control channels and channel pooling
Some MPT 1327 networks can also time-share control channels, which can be useful if the network has limited frequency availability as it frees up channels for use as traffic channels, which can also be pooled across sites so the network capacity follows the traffic. This is another advantage of MPT 1327 (and dPMR) over TDMA-based systems such as TETRA and DMR, who cannot pool traffic channels so efficiently (if at all). The disadvantage of using a Ttme-shared CCH is that it slows down registration and calls and requires some customization of the registration process, so is only useful if the network has a patient user community!Control channel cycling
The control channel can also be set to cycle, so each channel in turn becomes a control channel, say every ten minutes it will change. The advantage of this is that the base does not have to be rated at 100% duty cycle and does not get so hot. However, this can cause problems with queuing, affects registration and control channel acquisition times. Most base stations have a 100% duty-cycle rating, but this function can be useful if local Regulatory rules do not permit Continuous CCH operation. In countries where dedicated channels for trunked systems are not possible or availability is limited it is also possible to actively manage the use of traffic channels based on co-channel use, i.e. to avoid interfering with other users by using "friendly" channel acquisition protocols.Speech and data
Speech is sent as narrowbandNarrowband
In radio, narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. It is a common misconception that narrowband refers to a channel which occupies only a "small" amount of space on the radio spectrum.The opposite of...
frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
. Data messages between mobiles and the network are exchanged on the control channel at 1200 bits per second using FFSK signalling, or a specific "modem call", known as "non-prescribed data" can be established, whereby free-form 1200 baud data can be exchanged on a traffic channel without tying up the control channel. With the use of special modems, the speed can be 19,200 bit/s. This, along with Short Data Messaging and Status Messaging via the control channel makes an MPT1327 network ideal for managing AVL for asset management
Automatic vehicle location
Automatic vehicle location is a means for automatically determining the geographic location of a vehicle and transmitting the information to a requester....
, meter reading
Automatic meter reading
Automatic meter reading, or AMR, is the technology of automatically collecting consumption, diagnostic, and status data from water meter or energy metering devices and transferring that data to a central database for billing, troubleshooting, and analyzing.This technology mainly saves utility...
and SCADA
SCADA
SCADA generally refers to industrial control systems : computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:...
networks, the advantage being that the network can be used for this sort of application whilst still carrying voice traffic.
Numbering
Each subscriber in an MPT-1327 trunked radio network has a unique call number. This call number (address) is a compound number consisting of a prefix (three digits), the fleet number and the subscriber's call number within the fleet. Different numbering schemes work differently, for example Zetron uses the first two digits of the Ident as the fleet number, and the last two digits as the unit number. Idents in the 6000-6999 range are typically used to establish group calls. After it has been entered the call number will be converted in the mobile to a 20-bit address. The numbering rules are clarified and expanded by supplementary standards such as MPT-1343.For the duration of his call a subscriber is exclusively allocated a traffic channel from the available pool. If all channels are occupied, the call will be queued. If the control channel has become a traffic channel, like in the case of a non-dedicated control channel, the call will be queued in the radio, although radio queuing loses the first come, first served effect, so if there are seven units queuing, the last unit to queue may get a traffic channel first.
Traffic types
- Mobile-mobile in a cell
- Mobile-mobile in different cells
- Mobile-line access unit via landlineLandlineA landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline refers to a telephone line which travels through a solid medium, either metal wire or optical fibre, as distinguished from a mobile cellular line, where transmission is via radio waves...
or radio - Mobile-dispatcherDispatcherDispatchers are communications personnel responsible for receiving and transmitting pure and reliable messages, tracking vehicles and equipment, and recording other important information...
station via landline or radio - Mobile-PABX, Mobile-PSTN
Data communication
- Status messages on the control channel (5-bit data length)
- Short data messages on the control channel (186-bit data length)
- Transparent data transmission on the TC (data communication).
Calls
- Point to point connections
- Group calls with talk entitlement
- Group calls without talk entitlement (broadcast calls)
Broadcast calls can be used to make announcements to the entire customer base on a trunked system. For example, if work is to be carried out on the trunked system, the owner of the system can initiate a Broadcast Call which calls every mobile on the system. However, the mobiles may not have talk entitlement, so the PTT may not work. By this means the owner can announce to all customers a short period of inoperation due to maintenance.