The initiation of the actual telecommunications as we understand the term has a long precedence and history, from the era of fire and smoke signals in the most primitive yet functional format in order to deliver simple messages between two different physical locations. Claude Chappe was one of the pioneers who brought the optical signaling techniques to a new level by introducing a method that was based on the different positions of wooden signaling poles 1792 [1].
The finding of ways to handle electricity finally opened the new era of telecommunications as it provided the necessary means to deliver messages over long distances without the limitations of the line-of-sight that previous optical methods required. The characteristics of copper as telecommunication line conductor were well understood in the nineteenth century [2]. The most concrete application of this era was Morse code in the 1800s, which is still utilized actively by radio amateurs, or hams, all over the globe, although its importance in commercial communications has practically disappeared and it is utilized merely as a backup support in limited environments when other systems fail. Table 1.1 shows the original Morse codes that are still utilized in the ham community in addition to other transmission modes.
Voice services took their first steps soon after, and Alexander Graham Bell patented the fixed telephone in 1876. Regardless of official recognition, there were also other inventors like Elisha Gray brainstorming on the same topic, which was a concrete sign that people realized the importance of telecommunications.
The relevance of early experiments by radio amateurs cannot be underestimated. Radio and television broadcasting as we know it today benefited greatly from the experiments that radio amateurs carried out. After hobby-based activities, broadcasting was taken over by governments as the importance of communications started to become clear. Nevertheless, radio amateurs still continue with the experiments of the old and new transmission modes of wireless communications. The radio amateurs or “ham radio” community enjoys the amateur radio hobby in such a way that licensed participants operate communications equipment with a deep appreciation of the radio art [3]. Connections are typically confirmed via QSL card, i.e., cards for the acknowledgement of radio amateur connections, which nowadays can also have electronic form. Figure 1.1 shows an example of QSL card of radio amateurs which is used for acknowledging 2-way connections. Today, amateur radio activity is a mix of fun, public service, and convenience.
Amateurs have a basic knowledge of radio technology and operating principles, and pass an examination for the regulators’ license to operate on radio frequencies in the amateur bands. As an example, FCC is responsible for radio amateur licensing in the USA. As soon as the candidate passes the exams that include radio technologies, communications procedures and regulations, the candidate is awarded a license to operate
Table 1.1 The Morse code table
A . - K -.- U . .- 0 - - - - - B -. . . L .-. . V . . .- 1 .- - - - C -.-. M - - W .- - 2 . .- - - D -. . N -. X -. .- 3 . . .- - E . O - - - Y -.- - 4 . . . .- F . .-. P .- - . Z - - . . 5 . . . . . G - - . Q - - .- Dot .-.-.- 6 -. . . . H . . . . R .-. = -. . .- 7 - - . . . I . . S . . . Error . . .-. 8 - - - . . J .- - - T - End . . .-.- 9 - - - -.
Introduction 3
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0
KL76
TNX FER QSO = 73 DE CALIFORNIA
Jyrki T.J. Penttinen
10530 Hollingsworth Way San Diego, CA 92127
The United States of America
Loc. DM13KA = CQ Zone 3 = ITU Zone 6
Day/Month/Year UTC MHz Mode RST Remarks Confirming QSO with Radio:
KH
Member of The International Morse Preservation Society FISTS ID #16315
On the air also via call signs:
OH2NZP(Finland), since 1987
EA4GGT(Spain), since 2011
Figure 1.1 The QSL card is still utilized in amateur radio communications for confirming the connections. in the frequencies with the modes and technical limitations the respective class dictates. It should be noted that earlier the passing of the Morse code exam was also required for part of the classes, but it is not included in the official exam any more. Nevertheless, operating in continuous wave (CW) via Morse code is still one of the popular modes today.
The regulators, following the national and international principles, reserve the radio amateur frequency blocks for use by hams. There are various bands for the use of radio amateurs in almost all of the practically usable frequencies, beginning with the low frequency bands of 160 m (1.8 MHz band) up to the mm-bands near the limit of the ITU (International Telecommunications Union) radio frequency allocation tables. This arrangement provides an excellent opportunity to experiment with the practical radio wave propagation by utilizing various, analog and digital modes for voice, data and video transmission. Introductions for the ham radio can be found in Ref. [4].
The amateur radio, as well as the commercial, special and other types of radio stations, cellular and broadcast operators, and all the other entities that need a license or permit to send the radio signals over the air, are aligned via the national and international rules. The highest entity that dictates the utilization of the radio frequencies is ITU, and the national regulators and other related entities plan jointly the overall rules for the utilization, as well as the more specific limits for allowed power levels, frequency boundaries, and technologies that may possibly utilize per band. This joint alignment is to agree common rules, to avoid interferences between technologies, operators and countries. The great challenge of this work is to find an optimal solution so that as many services can be utilized as possible at a global level. The problem is that there have been countless solutions appearing in different useful bands over time since the invention of communications over the radio interface.
Due to the complexity of the different regional services on the radio frequencies, the world has been divided into three ITU regions as presented in Figure 1.2. The regions have slightly different divisions for frequency
4 The Telecommunications Handbook
ITU region 2 ITU region 1 ITU region 3
Figure 1.2 ITU regions.
utilization and different allowable power limits. This ITU division into three regions is valid for all radio communications from radio amateur activities to commercial, military and scientific mobile communications.
1.2.2 Analog Telephony Era
Early analog systems were based on manual connection of the voice calls. These exchange switchboards included the connection matrix which was handled by personnel. The crossbar switch was developed for automatic voice call delivery. The concept was most popular from 1950 to 1980. Most of the modern telephone switches at that time period were based on some variant of the crossbar switching system as presented in Figure 1.4. Along with the more advanced technology, the relay solutions took place as shown in Figure 1.3.
1.2.3 Wireless Era
The wireless telephony systems appeared in the markets in the beginning of 1970s. One of the early systems in the commercial and publicly available pioneers was ARP, Auto Radio Phone in Finland that was opened for the public 1971 [5]. It was still a manually operated system, and can be interpreted to represent the pre-1G systems. The automatic analog mobile systems falls into the category of 1G-systems and they appeared in the commercial markets as of the beginning of 1980s. Nordic Mobile Telephone (NMT) was one of the examples of this era, together with various similar systems in the USA and Europe appearing in the VHF/UHF bands. 1G-systems started to pave the way for the wireless era, and stayed in the markets for several decades until they were closed down typically at the beginning of 2000 due to the more advanced and spectral efficient variants of the next generation.
The common factor for 2G is digital functionality. GSM (Global System for Mobile communications), defined by ETSI/3GPP, is one of the most widespread and popular systems in the history of wireless telecommunications so far. GSM can be expected to stay in the markets and still evolve, even if the first
Introduction 5
Figure 1.3 An example of small-scale telephone exchange based on mechanical switches. This TELEVA KAU 2/5 model was produced in Finland and it was able to deliver 5 internal and 2 external calls based on the relay arrays. networks already appeared at the beginning of 1990s. In the US market, 2G is based on CDMA (1x), whilst GSM utilizes TDMA.
3G represents more spectral efficient systems, which are more clearly multimedia capable. Wide band CDMA-based UMTS (Universal Mobile Telecommunications System) paved the way for this era, and there have been various other systems. The evolution has brought, for example, HSPA (High Speed Packet Access), providing considerably higher data rates compared with the first 3G networks that were launched at the beginning of the 2000s.
The mobile system generations have appeared around once per decade, and 4G is no exception. The pre- version of the fully equipped 4G is, for example, LTE (Long Term Evolution) which will evolve towards ITU-defined 4G requirement compliance by the introduction of LTE-Advanced.