History of mobile phones

The history of mobile phones charts the development of devices which connect wirelessly to the public switched telephone network. The transmission of speech by radio has a long and varied history going back to Reginald Fessenden's invention and shore-to-ship demonstration of radio telephony, through the Second World War with military use of radio telephony links. Hand-held radio transceivers have been available since the 1940s. Mobile telephones for automobiles became available from some telephone companies in the 1940's. Early devices were bulky and consumed high power and the network supported only a few simultaneous conversations. Modern cellular networks allow automatic and pervasive use of mobile phones for voice and data communications.
Mobile phone history is often divided into generations (first, second, third and so on) to mark significant step changes in capabilities as the technology improved.

[edit] Pioneers of radio telephony

By 1930, telephone customers in the United States could place a call to a passenger on a liner in the Atlantic Ocean. Air time charges were quite high, at $7₍₁₉₃₀₎/minute (about $92.50/minute in 2011 dollars). ^[1] In areas with Marine VHF radio and a shore station, it is still possible to arrange a call from the public telephone network to a ship, still using manual call set-up and the services of a human marine radio operator.
However it was the 1940s onwards that saw the seeds of technological development which would eventually produce the mobile phone that we know today. Motorola developed a backpacked two-way radio, the Walkie-Talkie and a large hand-held two-way radio for the US military. This battery powered "Handie-Talkie" (HT) was about the size of a man's forearm.

[edit] Early services

[edit] MTS and IMTS

In 1946 in St. Louis, the Mobile Telephone Service was introduced. Only three radio channels were available, and call set-up required manual operation by a mobile operator. ^[2] Although very popular and commercially successful, the service was limited by having only a few voice channels per district.
In 1964 Improved Mobile Telephone Service was introduced with additional channels and more automatic handling of calls to the public switched telephone network. Even the addition of radio channels in three bands was insufficient to meet demand for vehicle-mounted mobile radio systems.

[edit] Radio Common Carrier

Parallel to Improved Mobile Telephone Service (IMTS) in the US until the rollout of cellular AMPS systems, a competing mobile telephone technology was called Radio Common Carrier or RCC. The service was provided from the 1960s until the 1980s when cellular AMPS systems made RCC equipment obsolete. These systems operated in a regulated environment in competition with the Bell System's MTS and IMTS. RCCs handled telephone calls and were operated by private companies and individuals. Some systems were designed to allow customers of adjacent RCCs to use their facilities but the universe of RCCs did not comply with any single interoperable technical standard (a capability called roaming in modern systems). For example, the phone of an Omaha, Nebraska–based RCC service would not be likely to work in Phoenix, Arizona. At the end of RCC's existence, industry associations were working on a technical standard that would potentially have allowed roaming, and some mobile users had multiple decoders to enable operation with more than one of the common signaling formats (600/1500, 2805, and Reach). Manual operation was often a fallback for RCC roamers.
Roaming was not encouraged, in part, because there was no centralized industry billing database for RCCs. Signaling formats were not standardized. For example, some systems used two-tone sequential paging to alert a mobile or hand-held that a wired phone was trying to call them. Other systems used DTMF. Some used a system called Secode 2805 which transmitted an interrupted 2805 Hz tone (in a manner similar to IMTS signaling) to alert mobiles of an offered call. Some radio equipment used with RCC systems was half-duplex, push-to-talk equipment such as Motorola hand-helds or RCA 700-series conventional two-way radios. Other vehicular equipment had telephone handsets, rotary or pushbutton dials, and operated full duplex like a conventional wired telephone. A few users had full-duplex briefcase telephones (radically advanced for their day).
RCCs used paired UHF 454/459 MHz and VHF 152/158 MHz frequencies near those used by IMTS.

[edit] Rural Radiotelephone Service

Using the same channel frequencies as IMTS, the US Federal Communications Commission authorized Rural Radiotelephone Service for fixed stations. Because RF channels were shared with IMTS, the service was licensed only in areas that were remote from large Bureau of the Census Metropolitan Statistical Areas (MSAs).^[3]
Systems used UHF 454 MHz or 152 MHz radio channels to provide telephone service to extremely rural places where it would be too costly to extend cable plant. One such system was on a 454/459 MHz channel pair between the Death Valley telephone exchange and Stovepipe Wells, California. This specific system carried manual calls to the Traffic Service Position System (TSPS) center in Los Angeles. Stovepipe Wells callers went off-hook and were queried, "Number please," by a TSPS operator, who dialed the call. Dial service was introduced to Stovepipe Wells in the mid-1980s. The radio link has since been replaced by cable. The analog service has since been replaced by Basic Exchange Telephone Radio Service, a digital system using the same frequencies.
Alongside the early developments outlined above, a different technology was also growing in popularity. Two-way mobile radios (known as mobile rigs) were used in vehicles such as taxicabs, police cruisers, and ambulances, but were not mobile phones, because they were not connected to the telephone network.

[edit] Before cellular networks

A mobile radio telephone.

These mobile radio telephone services preceded modern cellular mobile telephony technology. Since they were the predecessors of the first generation of cellular telephones, these systems are sometimes retroactively referred to as pre cellular (or sometimes zero generation) systems. Technologies used in pre cellular systems included the Push to Talk (PTT or manual), Mobile Telephone System (MTS), Improved Mobile Telephone Service (IMTS), and Advanced Mobile Telephone System (AMTS) systems. These early mobile telephone systems can be distinguished from earlier closed radiotelephone systems in that they were available as a commercial service that was part of the public switched telephone network, with their own telephone numbers, rather than part of a closed network such as a police radio or taxi dispatch system.
These mobile telephones were usually mounted in cars or trucks, though briefcase models were also made. Typically, the transceiver (transmitter-receiver) was mounted in the vehicle trunk and attached to the "head" (dial, display, and handset) mounted near the driver seat.
They were sold through WCCs (Wireline Common Carriers, AKA telephone companies), RCCs (Radio Common Carriers), and two-way radio dealers.
Early examples for this technology:

Motorola in conjunction with the Bell System operated the first commercial mobile telephone service Mobile Telephone System (MTS) in the US in 1946, as a service of the wireline telephone company.
The A-Netz launched 1952 in West Germany as the country's first public commercial mobile phone network.
First automatic system was the Bell System's IMTS which became available in 1962, offering automatic dialing to and from the mobile.
The Televerket opened its first manual mobile telephone system in Norway in 1966. Norway was later the first country in Europe to get an automatic mobile telephone system.
The Autoradiopuhelin (ARP) launched in 1971 in Finland as the country's first public commercial mobile phone network.
The B-Netz launched 1972 in West Germany as the country's second public commercial mobile phone network (but the first one that did not require human operators to connect calls).

[edit] Cellular concepts

[edit] Emergence of automated mobile phone services

The first fully automated mobile phone system for vehicles was launched in Sweden in 1960. Named MTA (Mobile Telephone system A), it allowed calls to be made and received in the car using a rotary dial. The car phone could also be paged. Calls from the car were direct dial, whereas incoming calls required an operator to determine which base station the phone was currently at. It was developed by Sture Laurén and other engineers at Televerket network operator. Ericsson provided the switchboard while Svenska Radioaktiebolaget (SRA) and Marconi provided the telephones and base station equipment. MTA phones consisted of vacuum tubes and relays, and weighed 40 kg. In 1962, an upgraded version called Mobile System B (MTB) was introduced. This was a push-button telephone, and used transistors and DTMF signaling to improve its operational reliability. In 1971 the MTD version was launched, opening for several different brands of equipment and gaining commercial success.^[10]^[11] The network remained open until 1983 and still had 600 customers when it closed.
In 1958 development began on a similar system for motorists in the USSR.^[12] The "Altay" national civil mobile phone service was based on Soviet MRT-1327 standard. The main developers of the Altay system were the Voronezh Science Research Institute of Communications (VNIIS) and the State Specialized Project Institute (GSPI). In 1963 the service started in Moscow, and by 1970 was deployed in 30 cities across the USSR. Versions of the Altay system are still in use today as a trunking system in some parts of Russia.
In 1959 a private telephone company located in Brewster, Kansas, USA, the S&T Telephone Company, (still in business today) with the use of Motorola Radio Telephone equipment and a private tower facility, offered to the public mobile telephone services in that local area of NW Kansas. This system was a direct dial up service through their local switchboard, and was installed in many private vehicles including grain combines, trucks, and automobiles. For some as yet unknown reason, the system, after being placed online and operated for a very brief time period, was shut down. The management of the company was immediately changed, and the fully operable system and related equipment was immediately dismantled in early 1960, not to be seen again.^{[citation needed]}
In 1966, Bulgaria presented the pocket mobile automatic phone RAT-0,5 combined with a base station RATZ-10 (RATC-10) on Interorgtechnika-66 international exhibition. One base station, connected to one telephone wire line, could serve up to six customers.^{[citation needed]}
One of the first successful public commercial mobile phone networks was the ARP network in Finland, launched in 1971. Posthumously, ARP is sometimes viewed as a zero generation (0G) cellular network, being slightly above previous proprietary and limited coverage networks.^{[citation needed]}

[edit] Handheld cell phone

Dr. Martin Cooper of Motorola, made the first US analog mobile phone call on a larger prototype model in 1973. This is a reenactment in 2007

Prior to 1973, cellular mobile phone technology was limited to phones installed in cars and other vehicles.^[13]
On April 3, 1973, Martin Cooper, a Motorola researcher and executive, made the first analog mobile phone call using a heavy prototype model. He called Dr. Joel S. Engel of Bell Labs.^[14]
There was a long race between Motorola and Bell Labs to produce the first portable mobile phone. Cooper is the first inventor named on "Radio telephone system" filed on October 17, 1973 with the US Patent Office and later issued as US Patent 3,906,166.^[15] John F. Mitchell, Motorola's chief of portable communication products (and Cooper's boss) was also named on the patent. He successfully pushed Motorola to develop wireless communication products that would be small enough to use anywhere and participated in the design of the cellular phone.^[16]^[17]

[edit] First generation: Cellular networks

Main article: 1G

The technological development that distinguished the First Generation of mobile phones from the previous generation was the use of multiple cell sites, and the ability to transfer calls from one site to the next as the user travelled between cells during a conversation. The first commercially automated cellular network (the 1G generation) was launched in Japan by NTT in 1979. The initial launch network covered the full metropolitan area of Tokyo's over 20 million inhabitants with a cellular network of 23 base stations. Within five years, the NTT network had been expanded to cover the whole population of Japan and became the first nation-wide 1G network.

Analog Motorola DynaTAC 8000X Advanced Mobile Phone System mobile phone as of 1983

The next 1G network to launch was the Nordic Mobile Telephone (NMT) system in Denmark, Finland, Norway and Sweden in 1981.^[18] NMT was the first mobile phone network to feature international roaming. The Swedish electrical engineer Östen Mäkitalo started work on this vision in 1966, and is considered to be the father of the NMT system, and by some the father of the cellular phone itself, since he and two colleagues hold a patent from 1971 on a cellular system with handover and roaming.^[19]^[20]^[21] The NMT installations were based on the Ericsson AXE digital exchange nodes.
Several other countries also launched 1G networks in the early 1980s including the UK, Mexico and Canada. A two year trial started in 1981 in Baltimore and Washington DC with 150 users and 300 Motorola DynaTAC pre-production phones. This took place on a seven tower cellular network that covered the area. The DC area trial turned into a commercial services in about 1983 with fixed cellular car phones also built by Motorola. They later added the 8000X to their Cellular offerings. A similar trial and commercial launch also took place in Chicago by Ameritech in 1983 using the famous first hand-held mobile phone Motorola DynaTAC.
AT&T's 1971 proposal for Advanced Mobile Phone System (AMPS) was approved by the FCC in 1982 and frequencies were allocated in the 824–894 MHz band.^[7] Analog AMPS was superseded by Digital AMPS in 1990.
In 1984, Bell Labs developed modern commercial cellular technology (based, to a large extent, on the Gladden, Parelman Patent), which employed multiple, centrally controlled base stations (cell sites), each providing service to a small cell area. The sites were set up so that cells partially overlapped and different base stations operated using the same frequencies with little or no interference.
Vodafone made the UK's first mobile call at a few minutes past midnight on January 1 1985.^[22]
The technology in these early networks was pushed to the limit to accommodate increasing usage. The base stations and the mobile phones utilized variable transmission power, which allowed range and cell size to vary. As the system expanded and neared capacity, the ability to reduce transmission power allowed new cells to be added, resulting in more, smaller cells and thus more capacity. The evidence of this growth can still be seen in the many older, tall cell site towers with no antennae on the upper parts of their towers. These sites originally created large cells, and so had their antennae mounted atop high towers; the towers were designed so that as the system expanded—and cell sizes shrank—the antennae could be lowered on their original masts to reduce range.

[edit] Second generation: Digital networks

Main articles: 2G, 2.5G, and 2.75G

Two 1991 GSM mobile phones with several AC adapters

In the 1990s, the 'second generation' (2G) mobile phone systems emerged, primarily using the GSM standard. These differed from the previous generation by using digital instead of analog transmission, and also fast out-of-band phone-to-network signaling. The rise in mobile phone usage as a result of 2G was explosive and this era also saw the advent of prepaid mobile phones
In 1991 the first GSM network (Radiolinja) launched in Finland. In general the frequencies used by 2G systems in Europe were higher than those in America, though with some overlap. For example, the 900 MHz frequency range was used for both 1G and 2G systems in Europe, so the 1G systems were rapidly closed down to make space for the 2G systems. In America the IS-54 standard was deployed in the same band as AMPS and displaced some of the existing analog channels.
Coinciding with the introduction of 2G systems was a trend away from the larger "brick" phones toward tiny 100–200g hand-held devices. This change was possible not only through technological improvements such as more advanced batteries and more energy-efficient electronics, but also because of the higher density of cell sites to accommodate increasing usage. The latter meant that the average distance transmission from phone to the base station shortened, leading to increased battery life whilst on the move.

Personal Handy-phone System mobiles and modems used in Japan around 1997–2003

The second generation introduced a new variant of communication called SMS or text messaging. It was initially available only on GSM networks but spread eventually on all digital networks. The first machine-generated SMS message was sent in the UK on 3 December 1992 followed in 1993 by the first person-to-person SMS sent in Finland. The advent of prepaid services in the late 1990s soon made SMS the communication method of choice amongst the young, a trend which spread across all ages.
2G also introduced the ability to access media content on mobile phones. In 1998 the first downloadable content sold to mobile phones was the ring tone, launched by Finland's Radiolinja (now Elisa). Advertising on the mobile phone first appeared in Finland when a free daily SMS news headline service was launched in 2000, sponsored by advertising.
Mobile payments were trialled in 1998 in Finland and Sweden where a mobile phone was used to pay for a Coca Cola vending machine and car parking. Commercial launches followed in 1999 in Norway. The first commercial payment system to mimic banks and credit cards was launched in the Philippines in 1999 simultaneously by mobile operators Globe and Smart.
The first full internet service on mobile phones was introduced by NTT DoCoMo in Japan in 1999.

[edit] Third generation: High speed IP data networks and mobile broadband

Main article: 3G

As the use of 2G phones became more widespread and people began to utilize mobile phones in their daily lives, it became clear that demand for data services (such as access to the internet) was growing. Furthermore, experience from fixed broadband services showed there would also be an ever increasing demand for greater data speeds. The 2G technology was nowhere near up to the job, so the industry began to work on the next generation of technology known as 3G. The main technological difference that distinguishes 3G technology from 2G technology is the use of packet switching rather than circuit switching for data transmission.^[23] In addition, the standardization process focused on requirements more than technology (2 Mbit/s maximum data rate indoors, 384 kbit/s outdoors, for example).
Inevitably this led to many competing standards with different contenders pushing their own technologies, and the vision of a single unified worldwide standard looked far from reality. The standard 2G CDMA networks became 3G compliant with the adoption of Revision A to EV-DO, which made several additions to the protocol whilst retaining backwards compatibility:

the introduction of several new forward link data rates that increase the maximum burst rate from 2.45 Mbit/s to 3.1 Mbit/s.
protocols that would decrease connection establishment time.
the ability for more than one mobile to share the same time slot.
the introduction of QoS flags.

All these were put in place to allow for low latency, low bit rate communications such as VoIP.^[24]
The first pre-commercial trial network with 3G was launched by NTT DoCoMo in Japan in the Tokyo region in May 2001. NTT DoCoMo launched the first commercial 3G network on October 1, 2001, using the WCDMA technology. In 2002 the first 3G networks on the rival CDMA2000 1xEV-DO technology were launched by SK Telecom and KTF in South Korea, and Monet in the USA. Monet has since gone bankrupt. By the end of 2002, the second WCDMA network was launched in Japan by Vodafone KK (now Softbank). European launches of 3G were in Italy and the UK by the Three/Hutchison group, on WCDMA. 2003 saw a further 8 commercial launches of 3G, six more on WCDMA and two more on the EV-DO standard.
During the development of 3G systems, 2.5G systems such as CDMA2000 1x and GPRS were developed as extensions to existing 2G networks. These provide some of the features of 3G without fulfilling the promised high data rates or full range of multimedia services. CDMA2000-1X delivers theoretical maximum data speeds of up to 307 kbit/s. Just beyond these is the EDGE system which in theory covers the requirements for 3G system, but is so narrowly above these that any practical system would be sure to fall short.
The high connection speeds of 3G technology enabled a transformation in the industry: for the first time, media streaming of radio (and even television) content to 3G handsets became possible [1], with companies such as RealNetworks [2] and Disney [3] among the early pioneers in this type of offering.
In the mid 2000s an evolution of 3G technology begun to be implemented, namely High-Speed Downlink Packet Access (HSDPA). It is an enhanced 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, also coined 3.5G, 3G+ or turbo 3G, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.0 Mbit/s. Further speed increases are available with HSPA+, which provides speeds of up to 42 Mbit/s downlink and 84 Mbit/s with Release 9 of the 3GPP standards.
By the end of 2007 there were 295 million subscribers on 3G networks worldwide, which reflected 9% of the total worldwide subscriber base. About two thirds of these were on the WCDMA standard and one third on the EV-DO standard. The 3G telecoms services generated over 120 Billion dollars of revenues during 2007 and at many markets the majority of new phones activated were 3G phones. In Japan and South Korea the market no longer supplies phones of the second generation.
Although mobile phones had long had the ability to access data networks such as the Internet, it was not until the widespread availability of good quality 3G coverage in the mid 2000s that specialized devices appeared to access the mobile internet. The first such devices, known as "dongles", plugged directly into a computer through the USB port. Another new class of device appeared subsequently, the so-called "compact wireless router" such as the Novatel MiFi, which makes 3G internet connectivity available to multiple computers simultaneously over Wi-Fi, rather than just to a single computer via a USB plug-in.
Such devices became especially popular for use with laptop computers due to the added portability they bestow. Consequently, some computer manufacturers started to embed the mobile data function directly into the laptop so a dongle or MiFi wasn't needed. Instead, the SIM card could be inserted directly into the device itself to access the mobile data services. Such 3G-capable laptops became commonly known as "netbooks". Other types of data-aware devices followed in the netbook's footsteps. By the beginning of 2010, E-readers, such as the Amazon Kindle and the Nook from Barnes & Noble, had already become available with embedded wireless internet, and Apple Computer had announced plans for embedded wireless internet on its iPad tablet devices beginning that Fall.

[edit] Fourth generation: All-IP networks

Main article: 4G

By 2009, it had become clear that, at some point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications like streaming media.^[25] Consequently, the industry began looking to data-optimized 4th-generation technologies, with the promise of speed improvements up to 10-fold over existing 3G technologies. The first two commercially available technologies billed as 4G were the WiMAX standard (offered in the U.S. by Sprint) and the LTE standard, first offered in Scandinavia by TeliaSonera.
One of the main ways in which 4G differed technologically from 3G was in its elimination of circuit switching, instead employing an all-IP network. Thus, 4G ushered in a treatment of voice calls just like any other type of streaming audio media, utilizing packet switching over internet, LAN or WAN networks via VoIP.^[26]

[edit] Satellite mobile

Main article: Satellite phone

Earth-orbiting satellites can cover remote areas out of reach of wired networks or where construction of a cellular network is uneconomic. The Inmarsat satellite telephone system, originally developed in 1979 for safety of life at sea, is now also useful for areas out of reach of landline, conventional cellular, or marine VHF radio stations. In 1998 the Iridium satellite system was set up, and although the initial operating company went bankrupt due to high initial expenses, the service is available today.

[edit] Patents

U.S. Patent 3,449,750:Duplex Radio Communication and Signaling Apparatus for Portable Telephone — George Sweigert of Euclid, Ohio, filed May 2, 1966, issued June 10, 1969
U.S. Patent 3,663,762: Cellular Mobile Communication System — Amos Edward Joel (Bell Labs), filed December 21, 1970, issued May 16, 1972
Swedish Patent N:o 357481, Mobil radioanläggning (Mobile radio system), R Berglund, T von Brömssen, Östen Mäkitalo (Televerket), filed 4 June 1971, issued 5 May 1973.
U.S. Patent 3,906,166: Radio Telephone System (Dyna-Tac) — Martin Cooper et al. (Motorola), filed October 17, 1973, issued September 16, 1975
U.S. Patent 4,144,411: Cellular Radiotelephone System for Different Cell Sizes — Richard H. Frenkiel (Bell Labs), filed September 22, 1976, issued March 13, 1979
U.S. Patent 4,152,647: Rapidly deployable emergency communication system — Charles A. Gladden and Martin H. Parelman, of Las Vegas, filed February 23, 1978, issued May 1, 1979
U.S. Patent 4,399,555: Cellular Mobile Radiotelephone System — Verne MacDonald, Philip Porter, Rae Young, (Bell Labs) filed April 28, 1980, issued August 16, 1983
U.S. Patent 5,129,098: Radio telephone using received signal strength in controlling transmission power — Andrew McGirr, Barry Cassidy (Novatel), filed September 24, 1990, issued July 7, 1992
U.S. Patent 5,265,158: Construction of a stand alone portable telephone unit — Jouko Tattari (Nokia), filed May 11, 1992, issued November 23, 1993
U.S. Patent 5,722,067: Security cellular telecommunications system — Douglas Fougnies et al. (Freedom Wireless), filed December 1994, issued February 24, 1998
U.S. Patent 5,826,185: Cellular phone system wherein the air time use is predetermined — Andrew Wise et al. (Banana Communications), filed November 1994, issued October 20, 1998
U.S. Patent 5,841,856: Hands-free telephone set — Yoshiyuki Ide (NEC), filed May 21, 1997, issued November 24, 1998
U.S. Patent 7,324,480: Mobile communication apparatus and method including base station and mobile station having multi-antenna: Per-User Unitary Rate Control (PU2RC) — James S. Kim, Kwangbok Lee, Kiho Kim and Changsoon Park, filed July 10, 2003, issued January 29, 2008

[edit] See also

[edit] Notes

^ Ship to Shore Telephone Service Opened, Popular Science, March 1930 page 34
^ ^a ^b Gordon A. Gow, Richard K. Smith Mobile and wireless communications: an introduction, McGraw-Hill International, 2006 ISBN 0335217613 page 23
^ Nathan J. Muller Wireless A to Z McGraw-Hill Professional, 2003 ISBN 0071410880 pages 17-18
^ see external link for the 1947 memo
^ article by Tom Farley "Cellular Telephone Basics"
^ See Amos Joel patent 3,663,762.
^ ^a ^b AT&T article
^ "Switching Plan for a Cellular Mobile Telephone System:, Z. Fluhr and E. Nussbaum, IEEE Transactions on Communications volume 21, #11 p. 1281 (1973)
^ "Data signaling functions for a cellular mobile telephone system", V. Hachenburg, B. Holm and J. Smith, IEEE Trans Vehicular Technology, volume 26, #1 p. 82 (1977)
^ Mingtao Shi, Technology base of mobile cellular operators in Germany and China, page 55
^ Facts about the Mobile. A Journey through Time
^ The first Russian mobile phone
^ See Amos Joel patent 3,663,762.
^ Shiels, Maggie (April 21, 2003). "BBC interview with Martin Cooper". BBC News. http://news.bbc.co.uk/1/hi/uk/2963619.stm.
^ Cooper, et al., "Radio Telephone System", US Patent number 3,906,166; Filing date: Oct 17, 1973; Issue date: September 1975; Assignee Motorola
^ "Motorola Executive Helped spur Cellphone Revolution, Oversaw Ill-fated Iridium Project". The Wall Street Journal, June 20–21, 2009, p. A10.
^ "John F. Mitchell, 1928-2009: Was president of Motorola from 1980 to '95, Chicago Tribune, June 17, 2009, retrieved June 17, 2009". Chicagotribune.com. http://www.chicagotribune.com/news/chi-hed-jmitchell-17-jun17,0,955426.story. Retrieved 2009-07-29.
^ "Swedish National Museum of Science and Technology". Tekniskamuseet.se. http://www.tekniskamuseet.se/mobilen/engelska/1980_90.shtml. Retrieved 2009-07-29.
^ Swedish Patent N:o 357481 Mobile radio system, 1971.
^ Mobile and technology: The Basics of Mobile Phones
^ The cell phone 50 years - facts and numbers
^ Vodafone
^ Privateline.com: 3G and Cellular radio Information
^ Gopal, Thawatt (11–15 March 2007). "EVDO Rev. A Control Channel Bandwidth Analysis for Paging". IEEE Wireless Communications and Networking Conference. IEEE. pp. 3262–7. doi:10.1109/WCNC.2007.601.
^ Fahd Ahmad Saeed. "Capacity Limit Problem in 3G Networks". Purdue School of Engineering. http://www.ece.iupui.edu/~dskim/Classes/ECE695MWN/2006-saeed-Capacity_Limit_Problem_in_3G_Networks.ppt. Retrieved April 23, 2010.
^ "VoIP Support in Nokia Devices". http://www.forum.nokia.com/Technology_Topics/Mobile_Technologies/VoIP/Nokia_VoIP_Framework/VoIP_support_in_Nokia_devices.xhtml. Retrieved 2009-08-16. ^{[dead link]}

[edit] References

Farley, Tom (2007). "The Cell-Phone Revolution". American heritage of invention & technology (New York: American Heritage) 22 (3): 8–19. ISSN 8756-7296. OCLC 108126426. BL Shelfmark 0817.734000. http://www.americanheritage.com/events/articles/web/20070110-cell-phone-att-mobile-phone-motorola-federal-communications-commission-cdma-tdma-gsm.shtml. Retrieved 2008-04-21.

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