Nordic Mobile Telephone

Nordic Mobile Telephone

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NMT is the first fully automatic cellular phone system. It was specified by Nordic
Nordic countries
The Nordic countries make up a region in Northern Europe and the North Atlantic which consists of Denmark, Finland, Iceland, Norway and Sweden and their associated territories, the Faroe Islands, Greenland and Åland...

 telecommunications administrations (PTTs) and opened for service in 1 October 1981 as a response to the increasing congestion and heavy requirements of the manual mobile phone networks: ARP
Autoradiopuhelin
ARP was the first commercially operated public mobile phone network in Finland. The technology is zero-generation , since although it had cells, moving between them was not seamless. The network was proposed in 1968 and building began in 1969. It was launched in 1971, and reached 100% geographic...

 (150 MHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

) in Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 and MTD
MTD (mobile network)
MTD was a manual mobile phone system for the 450 MHz frequency band. It was introduced in 1971 in Sweden, and lasted until 1987, when it was made obsolete by the NMT automatic service...

 (450 MHz) in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 and Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

. The Swedish
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 electrical engineer Östen Mäkitalo
Östen Mäkitalo
Östen Mäkitalo was a Swedish electrical engineer. He is considered to be the father of the Nordic Mobile Telephone system and many times the father of cellular phone.-Education and occupation:...

 is considered as the father of this system, and of the cell phone.

NMT is based on analog technology (first generation or 1G
1G
1G refers to the 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...

) and two variants exist: NMT-450 and NMT-900. The numbers indicate the frequency bands uses. NMT-900 was introduced in 1986 because it carries more channels than the previous NMT-450 network.

The NMT specifications were free and open, allowing many companies to produce NMT hardware and pushing the prices down. The success of NMT meant a lot to Nokia
Nokia
Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...

 (then Mobira) and Ericsson
Ericsson
Ericsson , one of Sweden's largest companies, is a provider of telecommunication and data communication systems, and related services, covering a range of technologies, including especially mobile networks...

. First Danish implementers were Storno (then owned by General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...

, later taken over by Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

) and AP (later taken over by Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

). Initial NMT phones were designed to mount in the trunk of a car, with a keyboard/display unit at the drivers seat. "Portable" versions existed: one could definitely move them, but they were bulky, and battery lifetime was a big problem. Latter-day models (such as Benefon
Benefon
GeoSentric is a mobile telecommunications company founded in 1988 and headquartered in Salo, Finland. Benefon specialises in the manufacture of mobile phones with inbuilt GPS navigation.- History :...

's) were as small as 100 mm and weighed only about 100 grams.

History


The NMT network was opened in Sweden and Norway in 1981, and in Denmark and Finland in 1982. Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

 joined in 1986. However, the first commercial service was introduced in Saudi Arabia
Saudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...

 on September 1, 1981 to 1200 users, one month before Sweden. By 1985 the network had grown to 110,000 subscribers in Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

 and Finland, 63,300 in Norway alone, which made it the world's largest mobile network at the time.

The NMT network has mainly been used in the Nordic countries, Latvia
Latvia
Latvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...

, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

, the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

, the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

, Slovakia
Slovakia
The Slovak Republic is a landlocked state in Central Europe. It has a population of over five million and an area of about . Slovakia is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south...

, Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...

, Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...

, Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

, Croatia
Croatia
Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...

, Bosnia
Bosnia and Herzegovina
Bosnia and Herzegovina , sometimes called Bosnia-Herzegovina or simply Bosnia, is a country in Southern Europe, on the Balkan Peninsula. Bordered by Croatia to the north, west and south, Serbia to the east, and Montenegro to the southeast, Bosnia and Herzegovina is almost landlocked, except for the...

, Baltic countries
Baltic countries
The term Baltic states refers to the Baltic territories which gained independence from the Russian Empire in the wake of World War I: primarily the contiguous trio of Estonia, Latvia, Lithuania ; Finland also fell within the scope of the term after initially gaining independence in the 1920s.The...

 and Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 and in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

. The introduction of digital mobile networks such as GSM has reduced the popularity of NMT and the Nordic countries have suspended their NMT networks. In Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 TeliaSonera
TeliaSonera
TeliaSonera AB is the dominant telephone company and mobile network operator in Sweden and Finland. The company has operations in other countries in Northern, Eastern Europe, Central Asia and Spain, with a total of 150 million mobile customers...

's NMT network was suspended on December 31, 2002. Norway's last NMT network was suspended on December 31, 2004. Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

's TeliaSonera
TeliaSonera
TeliaSonera AB is the dominant telephone company and mobile network operator in Sweden and Finland. The company has operations in other countries in Northern, Eastern Europe, Central Asia and Spain, with a total of 150 million mobile customers...

 NMT network was suspended on December 31, 2007. The NMT network (450 MHz) however has one big advantage over GSM which is the range; this advantage is valuable in big but sparsely populated countries such as Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

. In Iceland, the GSM network reaches 98% of the country's population but only a small proportion of its land area. The NMT system however reaches most of the country and a lot of the surrounding waters, thus the network is popular with fishermen and those traveling in the mountains. In Iceland NMT service was stopped on the 1st of September 2010, when Síminn
Síminn
Síminn, previously named Landssíminn, is an Icelandic telecommunications company. It was acquired by Exista in 2008.-History:Telecommunications play a vital role in Iceland. Although the country's population is relatively small , its penetration rates for network-related products and services are...

 closed down its NMT network.

In Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 the NMT-450 frequencies has been given to Swedish Nordisk Mobiltelefon (Sweden)
Nordisk Mobiltelefon (Sweden)
Nordisk Mobiltelefon was a Nordic operator of a digital CDMA2000 450 MHz mobile telephone network in Sweden, Norway and Denmark. Company was initially co-founded by . During 2008, the company introduced Ice.net which is the brand name that was used commercially.In February 2009 Nordisk Mobiltelefon...

 that later became Ice.net and renamed to Net 1
Nordisk Mobiltelefon (Sweden)
Nordisk Mobiltelefon was a Nordic operator of a digital CDMA2000 450 MHz mobile telephone network in Sweden, Norway and Denmark. Company was initially co-founded by . During 2008, the company introduced Ice.net which is the brand name that was used commercially.In February 2009 Nordisk Mobiltelefon...

 that built a digital network using CDMA 450.
The permission for TeliaSonera
TeliaSonera
TeliaSonera AB is the dominant telephone company and mobile network operator in Sweden and Finland. The company has operations in other countries in Northern, Eastern Europe, Central Asia and Spain, with a total of 150 million mobile customers...

 to continue operation of NMT-450 ended on December 31, 2007.

In Russia Uralwestcom shut down their NMT network on September 1, 2006 and Sibirtelecom on January 10, 2008.

Technology


The cell sizes in an NMT network range from 2 km to 30 km. With smaller ranges the network can service more simultaneous callers; for example in a city the range can be kept short for better service. NMT used full duplex transmission, allowing for simultaneous receiving and transmission of voice. Car phone versions of NMT used transmission power of up to 15 watt (NMT-450) and 6 watt (NMT-900), handsets up to 1 watt. NMT had automatic switching (dialing) and handover
Handover
In cellular telecommunications, the term handover or handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another...

 of the call built into the standard from the beginning, which was not the case with most preceding car phone services, such as the Finnish ARP
Autoradiopuhelin
ARP was the first commercially operated public mobile phone network in Finland. The technology is zero-generation , since although it had cells, moving between them was not seamless. The network was proposed in 1968 and building began in 1969. It was launched in 1971, and reached 100% geographic...

. Additionally, the NMT standard specified billing as well as national and international roaming
Roaming
In wireless telecommunications, roaming is a general term referring to the extension of connectivity service in a location that is different from the home location where the service was registered. Roaming ensures that the wireless device is kept connected to the network, without losing the...

.

Signaling


NMT voice channel is transmitted with FM-modulation and NMT signaling transfer speeds vary between 600 and 1200 bits per second, using FFSK (Fast Frequency Shift Keying) modulation. Signaling between the base station and the mobile station was implemented using the same RF channel that was used for audio, and using the 1200 bit/s FFSK modem. This caused the periodic short noise bursts, e.g. during handover, that were uniquely characteristic to NMT sound.

Security


A disadvantage of the original NMT specification is that voice traffic was not encrypted
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...

, therefore it was possible to listen to calls using e.g. a scanner
Scanner (radio)
A scanner is a radio receiver that can automatically tune, or scan, two or more discrete frequencies, stopping when it finds a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases....

. As a result, some scanners have had the NMT bands "deleted" so they could not be accessed. Later versions of the NMT specifications defined optional analog scrambling
Scrambler
In telecommunications, a scrambler is a device that transposes or inverts signals or otherwise encodes a message at the transmitter to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device...

 which was based on two-band audio frequency inversion. If both the base station and the mobile station supported scrambling, they could agree upon using it when initiating a phone call. Also, if two users had mobile stations (=mobile phones) supporting scrambling, they could turn it on during conversation even if the base stations didn't support it. In this case audio would be scrambled all the way between the two mobile stations. While the scrambling method was not at all as strong as encryption in newer digital phones, such as GSM, it did prevent casual listening with scanners. Scrambling is defined in NMT Doc 450-1: System Description (1999-03-23) and NMT Doc 450-3 and 900-3: Technical Specification for the Mobile Station (1995-10-04)'s Annex 26 v.1.1: Mobile Station with Speech Scrambling - Split Inversion Method (Optional) (1998-01-27).

Data transfer


NMT also supported a simple but robust integrated data transfer mode called DMS (Data and Messaging Service) or NMT-Text, which used the network's signaling channel for data transfer. Using DMS, also text messaging was possible between two NMT handsets before SMS service started in GSM, but this feature was never commercially available except in Russian, Polish and Bulgarian NMT networks. Another data transfer method was called NMT Mobidigi with transfer speeds of 380 bits per second. It required external equipment.