Cellular Generations
In the field of mobile communications, a "generation" refers to a change in the fundamental nature of the service. Each generation introduces new transmission technology, higher speeds and legislative adoptions to radio frequency spectrum. This article seeks to introduce the technologies behind each generation of mobile technology and provide context to the adoption of mobile technology.

0G


The emergence of personal mobile networks have radically shaped our modes of communication. The early 20th century artists envisioned the impact of mobile communication but it would be many years until there would be widespread adoption by consumers. Early wireless voice communication was made possible with the developments of radio technology in the early 20th century. The first two-way radio is attributed to Frederick William Downie, an Australian policeman who introduced the first mobile radios installed in patrol cars in 1923 [1]. Prior to the invention of radio police had to schedule regular check-ins for updates to their location. The use a two way radio system allowed police to be notified of crimes immediately and rapidly increase their response time. Soon police departments around the world  adopted the communication system and improvements to radio equipment allowed for more compact and portable communication and used extensively in World War II on the frontline.

After the war the Bell Labs, later AT&T, began developing a commercial mobile radio telephone system along commuter routes, introducing the  Mobile Telephone Service in 1946 [2]. The mobile radio telephone system differed from earlier closed radiotelephone system in that it connected to the public switched telephone system. This pre-cellular radio system had its limitations as the service only had limited coverage and constraints of technology. Only 3 radio channels were made available, so only three customers could make mobile telephone calls at a time. 

Development of mobile telephony continued primarily in the commuter industry with mobile radio telephones. The service was made available to customers in St. Louis, Missouri and serviced 5,000 customers. MTS was expensive, costing US$15 per month, plus $0.30–0.40 per local call, equivalent to (in 2012 US dollars) about $176 per month and $3.50–4.75 per call [3]. There was advancements in mobile radio telephones to provide more channels and service and a broader coverage until the cellular networks made them obsolete.


1G

The concept of a cellular network was first proposed in 1947 by Douglas Ring and. Rae Young at the Bell labs. They proposed a hexagonal cellular infrastructure which allow for greater coverage of area using a limited number of frequencies [4]. which would increase Bell Lab engineers would expand on the proposal to create detailed system plans with the proposal of directional antennas. Along with the development of a cellular tower network, key technologies that drive cellular technology are cell handover and frequency reuse. Cell handover is the process of switching between cell towers without interruption during continuous communication. Frequency reuse is a characteristic of cellular networks to re-use frequencies across the cells as long as devices are sufficiently far from each other. Thereby increasing overall coverage and capacity in the network.

The FCC rejected AT&T's 1947 proposal believing that the radio spectrum would be better used by services not "in the nature of convenience or luxury.  As a result of believing that there would be limited adoption, in 1949 FCC allocated only 4.7 percent of the available spectrum to the "land mobile" category whereas broadcast television received 59.2 percent of the spectrum. Television only used a fraction of this bandwidth. In 1952 the FCC authorized 2,002 TV stations, but a decade later there were only 603 television stations broadcasting. [5] The view that cellular technology would only  be a niche service persisted until the 1980's. McKinsey & Company forecasted that cell phone penetration in the U.S. would only be 900,000 subscribers. The regulatory restrictions and business development attitudes toward personal telephones stymied the growth of cellular technology for decades.

AT&T again proposed a modern-day mobile phone system to the FCC in 1958 but the FCC did not approve cellular spectrum until 1970. In 1973 the first cellular call was made by Marty Cooper, the Vice President of Motorola. The first cellular network was launched in Japan by Nippon Telegraph and Telephone in 1979 and the first 1G network in the United States was launched by Ameritech in Chicago in 1983 based on AT&T's Advanced Mobile Phone System (AMPS).

The first generation of cellular networks had some drawbacks. Since 1G was built on an analog system it suffered from similar vulnerabilities of the antecedent radio telephone technology. Primarily analog signals was prone to signal interference. Security was also a concern as anyone with a radio scanner could potentially eavesdrop on 1G devices.

Another cause of limited adoption of early cellular devices was the exorbitant costs. The first commercial mobile phone, Motorola DynaTAC, was made available in 1983 at the price of $4,000, (approximately $9,000 adjusted for 2019). The device became known as a symbol of success, popularized by Gordon Gecko in the 1987 film Wall Street.

2G


The second generation of cellular technology was introduced in the 1990's offering major changes from 1G. Two systems emerged as mobile networks moved from analog  technology to digital technology: the European GSM standard and the CDMA system used primarily in the United States. 2G cellular technology used the same cell infrastructure as the previous generation except it used digital radio signals.

To accomplish digital cellular signaling, three radio access technologies  emerged to facilitate digital signaling: time division multiple access (TDMA) allows for the division of signal into predetermined time slots. While frequency division multiple access (FDM) allows access to the radio spectrum all of the time by allocating different frequencies. Code division multiple access (CDMA) allows devices access to the radio spectrum all of the time by allocating a specific channel for each user through the use of unique codes throughout the duration of a call.  [6] The unique codes used to divide up the radio spectrum in CDMA technology creates built-in encryption, while GSM technologies require additional updates  for encryption. [7]
GSM technology grew in popularity in Europe and around the world. It was the first network to establish international roaming and sms or “text message”. 2G offers a theoretical maximum transfer speed of 64-144 kbit/s using General Packet Radio Service standardized by 3GPP [7]. (Learn more about cellular standardizing bodies.)  This allowed for basic data features such as web browsing, voicemail, email, and navigational maps.


The primary additions to 2G were:
1. Phone conversations were digitally encrypted and could not be eavesdropped 
2. More efficient use of the RF spectrum allowing more users per frequency band
3. Data services for mobile was introduced starting with SMS text messaging

3G


With the development of mobile telephone systems around the world, it became clear that there needed to be an agreement between network carriers to ensure interoperability between their networks. The third generation of cellular technology  was the result of research and development by ITU and 3G technology specifications were set forth under the name of IMT-2000. The  specification stated that the 400MHz and 3GHz spectrum was suitable for 3G technology.  The entire telecommunications industry including industry, national and regional bodies standard bodies had to approve the document for total interoperability. Many bodies collaborated on the agreement both in ITU (ITU-R, ITU-T) and outside of ITU (3GPP, 3GPP2). 

The third generation of wireless technology represented a large shift in the attitudes towards mobile telephones towards a globally connected world. A key vision of IMT-2000 was to allow for global roaming where mobile users can seamlessly move across borders and use the same telephone number and device.  2002 marked a historic landmark in mobile telephone  history as for the first time ever mobile telephone subscribers overtook the fixed telephone subscribers. To accommodate the increased capacity of devices, a number of infrastructural changes had to be made. 

The newly available 3G spectrum had to be allocated to mobile operators, and the method of allocating frequency licenses was subject to debate between telecommunication providers and governments.  There were two methods of allocating frequency: spectrum auctions and so called “beauty contests”. In a spectrum auction the license went to the highest bidder where in a beauty contest the license went to the applicant who best fit the criteria for the license. Generally applicants would be judged on their financial capacity, business plan and technical expertise.