Mobile phone Communications

The early days:
Before electronic communications were developed as they are today, people had to work hard to communicate over long distances using methods like smoke signals, light signals or waving flags.
Torch Relays:
Around the 13th century BC, this method is said to have been used by the Greeks to spread word of their victory over Troy in the Trojan War. This was a slow method because torches were passed from hand to hand, and bearers had to be careful that the fire didn't go out.
Voice Relays:
Around 550 BC, Cyrus the Great (the ruler of Persia) built rows of towers radiating out from his capital like the spokes of a wheel, with soldiers stationed atop each tower who could shout messages in a voice that could reach to the next tower. Because this was an oral relay system, messages sometimes changed somewhat along the way, as often happens when playing the 'telephone game'.
Smoke Signals:
Indians in western North America used smoke signals to communicate, just as seen in the movies. Smoke signals have been used around the world since before recorded history, but require prior agreement between the parties on a set of signals to be used and are unable to convey complex messages. The same is true of flag-based signal systems.
Letters:
The discovery of writing made it possible to send accurate and voluminous information. Methods of carrying letters evolved, such as foot and horse couriers, but delivery still took time. During the Prussian-French war in 1870 a system of 'carrier pigeons' was used but accuracy was hindered by the fact that some birds arrived and some did not.
People continued the quest for a method of communication that could carry large amounts of information quickly, accurately, at any time and to any location, cheaply and safely. This would find its expression in the invention of the telegraph and telephone.

The Birth of the Telegraph:
Born in Charlestown, Massachusetts in 1791, Samuel F. B. Morse invented the 'telegraph' in 1837, a machine that used electricity to relay signals. Then in 1844, Morse successfully demonstrated electrical communication using a 130km wire between Baltimore and Washington, sending the words 'What hath God wrought?' By 1850, a telegraph line connected Great Britain and France, and by 1857 the Transatlantic Cable connected Great Britain and the U.S. Soon thereafter, telegraph lines linked all parts of the world, and many people were able to use this new invention.

The Birth of the Telephone:
Alexander Graham Bell was born in Great Britain in 1847. In 1876 he invented a 'talking device' which could transmit a human voice to a listener.
However, Bell's device produced an extremely weak flow of audio current from the sending device, accompanied by a high level of static that made it difficult to hear. Research in transmitters continued until in 1878 Thomas Edison invented the carbon transmitter, a more practical device with much better characteristics which is still used today. The principle of the receiver has not changed. Telephone is a combination of the Greek words 'tele' meaning far and 'phone' meaning sound.

Recent Times

Mobile Communications:
Electromagnetic waves were first discovered as a communications medium at the end of the 19th century. The first systems offering mobile telephone service (car phone) were introduced in the early 1950s. Those early single cell systems were severely constrained by restricted mobility, low capacity, limited service, and poor speech quality. The equipment was heavy, bulky, expensive, and susceptible to interference. Because of those limitations, less than one million subscribers were registered worldwide by the early 1980s.

First Generation (1G): Analog Cellular
The introduction of cellular systems in the late 1970s and early 1980s represented a quantum leap in mobile communication (especially in capacity and mobility). Semiconductor technology and microprocessors made smaller, lighter weight, and more sophisticated mobile systems a practical reality for many more users. These 1G cellular systems still transmit only analog voice information. The most prominent 1G systems are Advanced Mobile Phone System (AMPS), Nordic Mobile Telephone (NMT), and Total Access Communication System (TACS). With the 1G introduction, the mobile market showed annual growth rates of 30 to 50 percent, rising to nearly 20 million subscribers by 1990.

Second Generation (2G): Multiple Digital Systems
The development of 2G cellular systems was driven by the need to improve transmission quality, system capacity, and coverage. Further advances in semiconductor technology and microwave devices brought digital transmission to mobile communications. Speech transmission still dominates the airways, but the demands for fax, short message, and data transmissions are growing rapidly. Supplementary services such as fraud prevention and encrypting of user data have become standard features that are comparable to those in fixed networks. 2G cellular systems include GSM, Digital AMPS (D-AMPS), code division multiple access (CDMA), and Personal Digital Communication (PDC). Today, multiple 1G and 2G standards are used in worldwide mobile communications. Different standards serve different applications with different levels of mobility, capability, and service area (paging systems, cordless telephone, wireless local loop, private mobile radio, cellular systems, and mobile satellite systems). Many standards are used only in one country or region, and most are incompatible. GSM is the most successful family of cellular standards (GSM900, GSM–railway [GSM–R], GSM1800, GSM1900, and GSM400), supporting some 250 million of the world’s 450 million cellular subscribers with international roaming in approximately 140 countries and 400 networks.

2G to 3G: GSM Evolution
Phase 1 of the standardization of GSM900 was completed by the European Telecommunications Standards Institute (ETSI) in 1990 and included all necessary definitions for the GSM network operations. Several tele-services and bearer services have been defined (including data transmission up to 9.6 kbps), but only some very basic supplementary services were offered. As a result, GSM standards were enhanced in Phase 2 (1995) to incorporate a large variety of supplementary services that were comparable to digital fixed network integrated services digital network (ISDN) standards. In 1996, ETSI decided to further enhance GSM in annual Phase 2+ releases that incorporate 3G capabilities. GSM Phase 2+ releases have introduced important 3G features such as intelligent network (IN) services with customized application for mobile enhanced logic (CAMEL), enhanced speech compression/decompression (CODEC), enhanced full rate (EFR), and adaptive multirate (AMR), high–data rate services and new transmission principles with high-speed circuit-switched data (HSCSD), general packet radio service (GPRS), and enhanced data rates for GSM evolution (EDGE). UMTS is a 3G GSM successor standard that is downward-compatible with GSM, using the GSM Phase 2+ enhanced core network. IMT–2000
The main characteristics of 3G systems, known collectively as IMT–2000, are a single family of compatible standards that have the following characteristics:

• Used worldwide
• Used for all mobile applications
• Support both packet-switched (PS) and circuit-switched (CS) data transmission
• Offer high data rates up to 2 Mbps (depending on mobility/velocity)
• Offer high spectrum efficiency

IMT–2000 is a set of requirements defined by the International Telecommunications Union (ITU). As previously mentioned, IMT stands for International Mobile Telecommunications, and “2000” represents both the scheduled year for initial trial systems and the frequency range of 2000 MHz (WARC’92: 1885–2025 MHz and 2110–2200 MHz). All 3G standards have been developed by regional standards developing organizations (SDOs). In total, proposals for 17 different IMT–2000 standards were submitted by regional SDOs to ITU in 1998—11 proposals for terrestrial systems and 6 for mobile satellite systems (MSSs). Evaluation of the proposals was completed at the end of 1998, and negotiations to build a consensus among differing views were completed in mid 1999. All 17 proposals have been accepted by ITU as IMT–2000 standards. The specification for the Radio Transmission Technology (RTT) was released at the end of 1999.

The most important IMT–2000 proposals are the UMTS (W-CDMA) as the successor to GSM, CDMA2000 as the interim standard ’95 (IS–95) successor, and time division–synchronous CDMA (TD–SCDMA) (universal wireless communication–136 [UWC–136]/EDGE) as TDMA–based enhancements to D–AMPS/GSM—all of which are leading previous standards toward the ultimate goal of IMT–2000.

UMTS allows many more applications to be introduced to a worldwide base of users and provides a vital link between today’s multiple GSM systems and IMT–2000. The new network also addresses the growing demand of mobile and Internet applications for new capacity in the overcrowded mobile communications sky. UMTS increases transmission speed to 2 Mbps per mobile user and establishes a global roaming standard.

UMTS is being developed by Third-Generation Partnership Project (3GPP), a joint venture of several SDOs—ETSI (Europe), Association of Radio Industries and Business/Telecommunication Technology Committee (ARIB/TTC) (Japan), American National Standards Institute (ANSI) T-1 (USA), telecommunications technology association (TTA) (South Korea), and Chinese Wireless Telecommunication Standard (CWTS) (China). To reach global acceptance, 3GPP is introducing UMTS in phases and annual releases. The first release (UMTS Rel. ’99), introduced in December of 1999, defines enhancements and transitions for existing GSM networks. For the second phase (UMTS Rel. ’00), similar transitions are being proposed as enhancements for IS–95 (with CDMA2000) and TDMA (with TD–CDMA and EDGE).

The most significant change in Rel. ’99 is the new UMTS terrestrial radio access (UTRA), a W–CDMA radio interface for land-based communications. UTRA supports time division duplex (TDD) and frequency division duplex (FDD). The TDD mode is optimized for public micro and pico cells and unlicensed cordless applications. The FDD mode is optimized for wide-area coverage, i.e., public macro and micro cells. Both modes offer flexible and dynamic data rates up to 2 Mbps. Another newly defined UTRA mode, multicarrier (MC), is expected to establish compatibility between UMTS and CDMA2000.