A cellular network or mobile network (sometimes known as cellular communication network or mobile communication network) is a telecommunications network where the link to and from end nodes is wireless and the network is distributed over land areas called cells, each served by at least one fixed-location transceiver (such as a base station). These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content via radio waves. Each cell's coverage area is determined by factors such as the power of the transceiver, the terrain, and the frequency band being used. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell.
When joined, these cells provide radio coverage over a wide geographic area. This enables numerous devices, such as mobile phones, tablets, laptops equipped with mobile broadband modems, and wearable devices such as smartwatches, to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the devices are moving through more than one cell during transmission. The design of cellular networks allows for seamless handover, enabling uninterrupted communication when a device moves from one cell to another.
Modern cellular networks utilize advanced technologies such as Multiple Input Multiple Output (MIMO), beamforming, and small cells to enhance network capacity and efficiency.
Cellular networks can offer a number of desirable features: More capacity than a single large transmitter, since the same frequency can be used for multiple links as long as they are in different cells Mobile devices use less power than a single transmitter or satellite since the cell towers are closer Larger coverage area than a single terrestrial transmitter, since additional cell towers can be added indefinitely and are not limited by the horizon Capability of utilizing higher frequency signals (and thus more available bandwidth / faster data rates) that are not able to propagate at long distances With data compression and multiplexing, several video (including digital video) and audio channels may travel through a higher frequency signal on a single wideband carrier Major telecommunications providers have deployed voice and data cellular networks over most of the inhabited land area of Earth. This allows mobile phones and other devices to be connected to the public switched telephone network and public Internet access. In addition to traditional voice and data services, cellular networks now support internet of things (IoT) applications, connecting devices such as smart meters, vehicles, and industrial sensors.
The evolution of cellular networks from 1G to 5G has progressively introduced faster speeds, lower latency, and support for a larger number of devices, enabling advanced applications in fields such as healthcare, transportation, and smart cities.
Private cellular networks can be used for research or for large organizations and fleets, such as dispatch for local public safety agencies or a taxicab company, as well as for local wireless communications in enterprise and industrial settings such as factories, warehouses, mines, power plants, substations, oil and gas facilities and ports.
Concept
In a cellular radio system, a land area to be supplied with radio service is divided into cells in a pattern dependent on terrain and reception characteristics. These cell patterns roughly take the form of regular shapes, such as hexagons, squares, or circles although hexagonal cells are conventional. Each of these cells is assigned with multiple frequencies (f1 – f6) which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the same frequencies are not reused in adjacent cells, which would cause co-channel interference.
The increased capacity in a cellular network, compared with a network with a single transmitter, comes from the mobile communication switching system developed by Amos Joel of Bell Labs, issued 16 May 1972. that permitted multiple callers in a given area to use the same frequency by switching calls to the nearest available cellular tower having that frequency available. This strategy is viable because a given radio frequency can be reused in a different area for an unrelated transmission. In contrast, a single transmitter can only handle one transmission for a given frequency. Inevitably, there is some level of interference from the signal from the other cells which use the same frequency. Consequently, there must be at least one cell gap between cells which reuse the same frequency in a standard frequency-division multiple access (FDMA) system.
Consider the case of a taxi company, where each radio has a manually operated channel selector knob to tune to different frequencies. As drivers move around, they change from channel to channel. The drivers are aware of which frequency approximately covers some area. When they do not receive a signal from the transmitter, they try other channels until finding one that works. The taxi drivers only speak one at a time when invited by the base station operator. This is a form of time-division multiple access (TDMA).
Orbital Cellular Orbital cellular networks, also known as Direct-to-Cell satellite networks (D2C), Direct-to-Device networks, Satellite-to- Smartphone and Non-Terrestrial Networks (NTN) represent an evolution in mobile telephony where standard terrestrial cellular frequencies are broadcast directly from low Earth orbit (LEO) satellites to unmodified consumer smartphones. Unlike traditional satellite phones that require proprietary hardware and bulky antennas, these space-based networks use advanced phased array antennas to project highly precise, moving cell coverage sectors onto the Earth's surface. These satellite-based cells seamlessly interoperate with ground-based networks by utilizing roaming partnerships and existing mobile network operator (MNO) spectrum. The primary objective of orbital cellular networks is to eliminate rural coverage gaps, provide critical emergency communication infrastructure in disaster-stricken zones, and establish a foundational layer for global Internet of Things (IoT) connectivity across remote land masses and oceans where building terrestrial masts is economically or logistically unfeasible.
History
The idea to establish a standard cellular phone network was first proposed on December 11, 1947. This proposal was put forward by Douglas H. Ring, a Bell Labs engineer, in an internal memo suggesting the development of a cellular telephone system by AT&T.
The first commercial cellular network, the 1G generation, was launched in Japan by Nippon Telegraph and Telephone (NTT) in 1979, initially in the metropolitan area of Tokyo. However, NTT did not initially commercialize the system; the early launch was motivated by an effort to understand a practical cellular system rather than by an interest to profit from it. In 1981, the Nordic Mobile Telephone system was created as the first network to cover an entire country. The network was released in 1981 in Sweden and Norway, then in Finland and Denmark in early 1982. Televerket, a state-owned corporation responsible for telecommunications in Sweden, launched the system.
In September 1981, Jan Stenbeck, a financier and businessman, launched Comvik, a Swedish telecommunications company. Comvik was the first European telecommunications firm to challenge the state's telephone monopoly on the industry. According to sources, Comvik was the first to launch a commercial automatic cellular system before Televerket launched its own in October 1981. However, at the time of the new network's release, the Swedish Post and Telecom Authority threatened to shut down the system after claiming that the company had used an unlicensed automatic gear that could interfere with its own networks. In December 1981, Sweden awarded Comvik with a license to operate its own automatic cellular network in the spirit of market competition.
The Bell System had developed cellular technology since 1947, and had cellular networks in operation in Chicago, Illinois, and Dallas, Texas, prior to 1979; however, regulatory battles delayed AT&T's deployment of cellular service to 1983, when its Regional Holding Company Illinois Bell first provided cellular service.
First-generation cellular network technology continued to expand its reach to the rest of the world. In 1990, Millicom Inc., a telecommunications service provider, strategically partnered with Comvik's international cellular operations to become Millicom International Cellular SA.“Millicom International Cellular S.A. (31, March 2004). Form 6-K. Retrieved from the Securities and Exchange Commission". The company went on to establish a 1G systems foothold in Ghana, Africa under the brand name Mobitel.“Millicom International Cellular S.A. (31, Dec. 2008). Form 20-F. Retrieved from the Securities and Exchange Commission". In 2006, the company's Ghana operations were renamed to Tigo.
The wireless revolution began in the early 1990s, leading to the transition from analog to digital networks. The MOSFET invented at Bell Labs between 1955 and 1960, was adapted for cellular networks by the early 1990s, with the wide adoption of power MOSFET, LDMOS (RF amplifier), and RF CMOS (RF circuit) devices leading to the development and proliferation of digital wireless mobile networks.
The first commercial digital cellular network, the 2G generation, was launched in 1991. This sparked competition in the sector as the new operators challenged the incumbent 1G analog network operators.
Cell signal encoding To distinguish signals from several different transmitters, a number of channel access methods have been developed, including frequency-division multiple access (FDMA, used by analog and D-AMPS systems), time-division multiple access (TDMA, used by GSM) and code-division multiple access (CDMA, first used for PCS, and the basis of 3G).
With FDMA, the transmitting and receiving frequencies used by different users in each cell are different from each other. Each cellular call was assigned a pair of frequencies (one for base to mobile, the other for mobile to base) to provide full-duplex operation. The original AMPS systems had 666 channel pairs, 333 each for the CLEC "A" system and ILEC "B" system. The number of channels was expanded to 416 pairs per carrier, but ultimately the number of RF channels limits the number of calls that a cell site could handle. FDMA is a familiar technology to telephone companies, which used frequency-division multiplexing to add channels to their point-to-point wireline plants before time-division multiplexing rendered FDM obsolete.
With TDMA, the transmitting and receiving time slots used by different users in each cell are different from each other. TDMA typically uses digital signaling to store and forward bursts of voice data that are fit into time slices for transmission, and expanded at the receiving end to produce a somewhat normal-sounding voice at the receiver. TDMA must introduce latency (time delay) into the audio signal. As long as the latency time is short enough that the delayed audio is not heard as an echo, it is not problematic. TDMA is a familiar technology for telephone companies, which used time-division multiplexing to add channels to their point-to-point wireline plants before packet switching rendered TDM obsolete.