TetraEssay Preview: TetraReport this essayTETRA is an open standard developed by the European Telecommunications Standards Institute (ETSI). The main purpose of the TETRA standard was to define a series of open interfaces, as well as services and facilities, in sufficient detail to enable independent manufacturers to develop infrastructure and terminal products that would fully interoperate with each other as well as meet the needs of traditional PMR user organisations.
The initial responsibility of ETSI Project TETRA (now known as ETSI Technical Committee (TC) TETRA) was to deliver as set of standards, under a mandate from the European Commission, for a Digital Trunked PMR communications system that could be deployed in Western Europe. As well as producing these mandatory ETSI deliverables (now completed), TC TETRA’s responsibility was, and still is, to make sure that the portfolio of standards continue to be developed in accordance with user needs and priorities.
The technology solutions chosen to meet user requirements contained in the TETRA standards have been, and continue to be, developed primarily by well know and respected manufacturers who have been serving the PMR market with products and services for several decades. This combined “Know How” ensures that optimum technology solutions are chosen to meet user requirements. Details of manufacturers can be viewed on the member’s page of the TETRA Association by clicking on the left hand menu under core products.
Although the prime responsibility of ETSI is to develop standards for Europe, many of its standards are also adopted world-wide, as evidenced by the uptake of GSM, the first wireless technology standard to be developed by ETSI. Similarly, TETRA has already been deployed in many regions and nations outside Europe, resulting in TETRA becoming a truly global standard.
There is no doubt that a proprietary technology solution can be brought to market in less time than a solution conforming to a recognised open standard. However, large user organisations, especially those in the public sector, have recognized that some proprietary solutions can meet their needs but the �tie in’ to a single supplier can have significant disadvantages. Even though there are some disadvantages, the main advantages and benefits of adopting an open standard are:
•Economies of scale provided by a large harmonised market served by several independent manufacturers and suppliers competing for the same business resulting in competitively priced solutions
•Second source security if existing suppliers exit the market•Evolution (instead of revolution) of the technology standard ensuring longevity and good return on investment for both users and suppliers•Choice of manufacturers for new products keeping prices down•Greater choice of products for specialised applications•Greater responsiveness to future needs by existing suppliers because of competitionBecause there are several independent manufacturers of both TETRA network infrastructure and radio terminals all the benefits of standardisation listed also apply to the TETRA market.
Evolution & LongevityThe ETSI TETRA standard will continue to evolve beyond Release 1 and Release 2 to provide additional enhancements as driven by user needs, technology innovations and other parallel standard developments. As a consequence, ETSI has no plans to develop a new technology standard for use by large traditional PMR user organisations. Similarly, other technology standards being developed and/or available outside Europe offer little or no benefit over what TETRA already provides.
This planned evolution of TETRA can be appreciated when considering that traditional PMR user organisations will always require private PMR networks because public networks cannot adequately provide the required RF coverage, Grade of Service (GoS) during busy periods and high levels of reliability. Besides these basic needs, public networks will not be able to provide the specialised voice services such as wide area fast call-set up all informed nets (group calls), Direct Mode Operation (DMO) and high levels of secure encryption for voice and data.
In summary, TETRA will evolve in a similar way to GSM, which evolved from providing a basic V+D “one to one” telephony service (via GSM II+, GPRS, EDGE, etc.) to UMTS/3G supporting powerful multimedia applications and High Speed Data. Also, the focus and technology solution for Next Generation Networks (NGN) will primarily be for public networks.
Taking these previous factors into consideration and the fact that analogue MPT 1327 trunking networks are still being deployed across the world more than 28 years after the technology was first developed, TETRA networks are expected to be available for at least another 25 years, thereby ensuring a very good return on investment for user organisations as well as manufacturers and suppliers.
Technology BenefitsThe core technologies used in the TETRA standard, such as Digital, Trunking and Time Division Multiple Access (TDMA) also provide a number of inherent advantages and benefits as follows:
DigitalNowadays, practically everything electronic uses digital technology and wireless communications are no exception. Even though analogue FM PMR communications will remain a viable option for several years, digital radio provides relative advantages and disadvantages in the important performance areas of:
•Voice Quality•RF Coverage•Non-Voice Services•Security•CostTrunkingTrunking techniques have been used for many years in switched telephone networks. The first trunked mobile radio communication systems were deployed as early the 70s in North America with proprietary signalling protocols and shortly afterwards in Europe using analogue MPT1327 technology. The main benefit of trunking is normally seen as spectrum efficiency, or more radio users per RF channel compared with a conventional radio channel for a given Grade of Service (GoS), brought about by the automatic and dynamic assignment of a small number of communication channels shared amongst a relatively large number of users. Because trunking systems support more radio users
\
System Design
\
The first modern set of trunked mobile radio communication interfaces was designed by Dr. Edward Coyle, a specialist in radio and telecom technologies, from the University of Aberdeen. He built the first system, called a system to allow users to “switch to another channel” which he described as “one of the basic rules we had as broadcasters. Instead of the ‘main stream’ channel, in your phone a different one was used – like a “real”, normal, fixed, digital, etc. One can simply switch from a main stream audio channel to a different, higher quality, digital one. In the end it was just to make a better connection by a simple act of programming; they used the same channels and so on. To make a phone call, it had to be linked up to the TV so that it could play a very different audio file at the same time. It was a very important development in this field, and yet so few people have developed the technology in a practical way. For the last 50 years now some of the most talented engineers in the industry have developed their own and better technology. Some of them have been the first to use ‘ghost power’ (i.e.; a ‘tapping sound generator’), but they too have used it for years to create the technology and implement it in real-world equipment.
\
The following diagram contains details on what we call a trunked mobile telephone. It shows the base signal voltage of an APU (electrical signal generator), coupled to a mobile antenna. On a real telephone the main voltage at the top of the signal is 3.5V. The main signal voltage at the bottom is 2.3V, which is the power level of each cell in the line. On an APU, the main power level goes up and down. The main voltage at 10-15V is 3.5V, which is the signal level. This will get low power to the main voltage. What happens is the APU switches to the APU’s normal 10-15V. When the APU’s normal power is low the mobile antenna is placed in a “low impedance” state. Because the main is so small at one end the mobile antenna’s lower level can penetrate over an area of up to two meters.
\
The following diagram provides more information on how to use a trunked mobile telephone. It displays the data needed to make your handset work without any interference. Each cell in your line is given a current – the current is determined by how much of the line is using the trunking protocol, which in turn determines the current level, the current is fed to the transmitter and converted back to the line which is used to set up the