Our On-Line School of Network Science Glossary of Telecommunications Terms and Acronyms

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  • a.k.a. ESS 1, No. 1 ESS
  • ESS = Electronic Switching System
  • developed by AT&T
  • electronic switching but analog circuits


First-generation of wireless telephone technology, mobile telecommunications

These are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications. The main difference between two succeeding mobile telephone systems, 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G networks are digital. Although both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system, the voice itself during a call is encoded to digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150 MHz and up.

The inherent advantages of digital technology over that of analog meant that 2G networks eventually replaced them almost everywhere. One such standard is NMT, used in Nordic countries, Switzerland, Netherlands, Eastern Europe and Russia. Others include AMPS used in the North America and Australia, TACS in the United Kingdom, C-450 in West Germany, Portugal and South Africa, Radiocom 2000 in France, and RTMI in Italy. In Japan there were multiple systems. Three standards, TZ-801, TZ-802, and TZ-803 were developed by NTT , while a competing system operated by DDI (Daini Denden Planning, Inc.) used the JTACS standard. 1G speeds vary between that of a 28k modem (28kbit/s) and 56k modem (56kbit/s), meaning actual download speeds of 28kbit/s to 56kbit/s.



2nd Generation (Wireless)

Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by Radiolinja (now part of Elisa Oyj) in 1991. Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages. 2G technologies enabled the various mobile phone networks to provide the services such as text messages, picture messages and MMS (multi media messages). All text messages sent over 2G are digitally encrypted, allowing for the transfer of data in such a way that only the intended receiver can receive and read it. After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.



Triple Data Encryption Standard


3rd Generation (Wireless)

This is based on a set of standards used for mobile devices and mobile telecommunication use services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union.  3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV. 3G telecommunication networks support services that provide an information transfer rate of at least 200 kbit/s. Later 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop computers. This ensures it can be applied to wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV technologies. A new generation of cellular standards has appeared approximately every tenth year since 1G systems were introduced in 1981/1982. Each generation is characterized by new frequency bands, higher data rates and non-backwards compatible transmission technology. The first release of the 3GPP Long Term Evolution (LTE) standard does not completely fulfill the ITU 4G requirements called IMT-Advanced. First release LTE is not backwards compatible with 3G, but is a pre-4G or 3.9G technology, however sometimes branded 4G by the service providers. Its evolution LTE Advanced is a 4G technology. WiMAX is another technology verging on or marketed as 4G.


Third Generation Partnership Project

A collaboration between groups of telecommunications associations, known as the Organizational Partners. The initial scope of 3GPP was to make a globally applicable third-generation (3G) mobile phone system specification based on evolved GSM specifications within the scope of the International Mobile Telecommunications-2000 project of the ITU. The scope was later enlarged to include the development and maintenance of:

  • the Global System for Mobile Communications (GSM) including GSM evolved radio access technologies (e.g. General Packet Radio Service (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE))
  • an evolved third Generation and beyond Mobile System based on the evolved 3GPP core networks, and the radio access technologies supported by the Partners (i.e., UTRA both FDD and TDD modes). 
  • an evolved IMS developed in an access independent manner 3GPP standardization encompasses Radio, Core Network and Service architecture.

The project was established in December 1998 and should not be confused with 3rd Generation Partnership Project 2 (3GPP2), which specifies standards for another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000. The 3GPP support team (also known as the "Mobile Competence Centre") is located at the ETSI headquarters in Sophia-Antipolis (France).



4th Generation (Wireless)

This is a successor to the 3G mobile systems.  A 4G system, in addition to usual voice and other services of 3G system, provides mobile ultra-broadband Internet access, for example to laptops with USB wireless modems, to smartphones, and to other mobile devices. Even though 4G is a successor technology of 3G, there can be signification issues on 3G network to upgrade to 4G as many of them were not built on forward compatibility. Conceivable applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing, 3D television, and cloud computing. Two 4G candidate systems are commercially deployed: the Mobile WiMAX standard (first used in South Korea in 2006), and the first-release Long Term Evolution (LTE) standard (in Oslo, Norway and Stockholm, Sweden since 2009). It has however been debated if these first-release versions should be considered to be 4G or not.



  • a.k.a. ESS 5, No. 5 ESS
  • ESS = Electronic Switching System
  • full digital switch
  • run by the UNIX operating system


Fifth Generation Mobile Networks or Wireless Systems

The next major phase of mobile telecommunications standards beyond the current 4G/IMT-Advanced standards. 5G is also referred to as beyond 2020 mobile communications technologies. 5G does not describe any particular specification in any official document published by any telecommunication standardization body.

A new mobile generation has appeared approximately every 10th year since the first 1G system, Nordic Mobile Telephone, was introduced in 1981. The first 2G system started to roll out in 1992, the first 3G system first appeared in 2001 and 4G systems fully compliant with IMT-Advanced were standardized in 2012. The development of the 2G (GSM) and 3G (IMT-2000 and UMTS) standards took about 10 years from the official start of the R&D projects, and development of 4G systems started in 2001 or 2002. Predecessor technologies have occurred on the market a few years before the new mobile generation, for example the pre-3G system CdmaOne/IS95 in the US in 1995, and the pre-4G systems Mobile WiMAX in South-Korea 2006, and first release-LTE in Scandinavia 2009.  Mobile generations typically refer to non–backwards-compatible cellular standards following requirements stated by ITU-R, such as IMT-2000 for 3G and IMT-Advanced for 4G. In parallel with the development of the ITU-R mobile generations, IEEE and other standardization bodies also develop wireless communication technologies, often for higher data rates and higher frequencies but shorter transmission ranges. The first gigabit IEEE standard was WiGig or IEEE 802.11ac, commercially available since 2013, soon to be followed by the multi gigabit standard IEEE 802.11ad


Number 5 Cross Bar (for local switching; Number 4 was for toll-tandem use)

  • a telephone switch employing a huge matrix of connected crossbar switches (which are also matrices of contacts)
  • typically, each crossbar switch was composed of twenty vertical paths "in" and ten horizontal paths "out". If you wanted a more orthogonal matrix, you could stack (electrically speaking) a second one on top of the first making it 20h x 20v.
  • To close a set of contacts, one of ten select magnets operated one of five horizontal bars either up or down (the center position was neutral) which moved a metal enabler spring into position. This action was followed by the operation of one of twenty vertical hold magnets which forced the metal spring to close three, or more, contacts. Now the select magnet is released (to set up the next connection) while the hold magnet maintains the existing connection until the customer disconnects.
  • the crossbar switches were controlled by an electro-mechanical computer known as a marker (named because they "marked out a path" through the central office)
  • most of these systems supported both touch-tone and dial phones
  • North American average installed life: 20 years
  • http://en.wikipedia.org/wiki/Crossbar

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