Generations of Mobile Communication
...ncreasing demand these services quickly became saturated in major markets. The congestion in the radio spectrum made it clear that a whole new approach was necessary. As the governments refused to increase the spectrum and as there were a number of interoperability problems if a wider spectrum was used a new solution had to be obtained. Cellular radiotelephony techniques were developed by breaking the coverage zone into smaller cells, each of which reuse portions of the spectrum to increase spectrum usage at the cost of greater system infrastructure. Since the transmitted power drops with distance, cells located far apart could be assigned the same spectrum. With this ability to reuse the spectrum, cellular accommodates many more customers. Moreover, since the coverage area of each base station was greatly reduced, low power transmitters at each base station were sufficient to cover the entire cell. The handoff mechanism was also incorporated allowing long and uninterrupted calls to be placed. The world’s first operational cellular system was implemented by the Nippon Telephone and Telegraph Company (NTT) in Japan, in 1979. This was followed in the north-European countries in 1981 by the Nordic Mobile Telephone (NMT 450) system developed by Ericsson that began operation in Scandinavia. Total Access Communication System (TACS) was introduced in the United Kingdom in 1982 and the Extended Total Access Cellular System (ETACS) was deployed in 1985. Subsequently, in Germany, the C-450 cellular system was introduced in September 1985. Another system called Radicom 2000 was in introduced in 1985 in France. In North America, a system named Advanced Mobile Phone System (AMPS) was a pioneer. The company, Ameritech, first placed it in service in 1983 in Chicago. AMPS used FM in the 800 MHz frequency band with each channel having a bandwidth of 30 kHz. The Federal Communication Commission (FCC) initially allocated 40 MHz of bandwidth for AMPS cellular in 1981. To ensure some competition, the FCC insisted on a duopoly by mandating two and only two cellular providers serve each market. Each provider was designated as either “A-side” or “B-side.” A-side providers were upstart companies that did not originate in the traditional telephone business. They were called non-wireline carriers. B-side providers had a base in telecommunication services and were called wireline carriers. Most of these systems were incompatible with one another because of the different frequencies and communication protocols used. Within a few years of introduction of these systems, usage levels began to soar. In order to cater to this demand there was a great need to introduce a digital system that would use the available frequency spectrum a lot more efficiently. Additionally, the development of the European common market led to greater movement of people among the European countries and there was a great demand for interoperability of mobile services. Both these factors were the main drivers for the creation of the next generation of mobile services. The first generation of mobile phones was deployed around 1985 in some developed countries. Based on the figures, it can be seen that in Scandinavian countries where mobile systems were introduced since the early eighties there was a very high penetration of mobile phones and the rate of growth of the market was also very high. The growth of wireless services in USA, Canada, Ireland, U.K., Australia and New Zealand was quite high with market penetration of 3% to 5%. The development in the other European countries and the Asian countries were not that rapid. Second Generation The primary reason for the development of second generation technologies round the globe was to use the available spectrum more efficiently. By the late 1980s, it was clear that the first generation cellular systems – based of analog signalling techniques ¬– were becoming obsolete. Advances in integrated circuit (IC) technology had made digital communications not only practical, but, actually, more economical than analog technology. This digital communication technology was used to achieve the required efficiency. Digital communication enables advanced source coding techniques to be utilized, thereby, reducing the amount of bandwidth required for voice and video. In addition, error correction coding was also used to provide a degree of resistance to interference and fading that plagues analog systems, and to allow a lower transmit power. The 2G standards represent the first set of wireless air interface standards to rely on digital modulation and sophisticated digital signal processing in the handset and the base station. Due to increased movement of users across borders in Europe, a common radio system was developed. Additionally, as the design of a new radio system required a very large investment, it was developed together by several countries. In early 1990s, second generation cellular system began to be deployed throughout the world. Four main second generation systems arose globally. In Europe the system was Global System for Mobile Communication (GSM), the Pan-European digital cellular standard, and had been deployed widely in Europe, Asia, Australia, South America and some parts of North America. This system was initially called Groupe Spèciale Mobile. Digital AMPS (DAMPS) in North America which evolved into the North American Digital Cellular (NADC). This system has been deployed in North America, South America and Australia. Pacific Digital Cellular (PDC) a Japanese Time Division Multiple Access (TDMA) standard. Code Division Multiple Access (CDMA) standard Interim Standard 95 (IS-95), known as cdmaOne, was introduced by the TR45.5 subcommittee of the Telecommunications Industry Association (TIA) in 1993. Second generation digital systems can be classified by their multiple access techniques as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA). In FDMA, the radio spectrum is divided into a set of frequency slots and each user is assigned a separate frequency to transmit. In TDMA, several users transmit at the same frequency but in different time slots. CDMA uses the principle of direct sequence spread-spectrum: the signals are modulated with high bandwidth spreading waveforms called signature waveforms or codes. Although the users transmit at both the same frequency and time, separation of signals is achieved because the signature waveforms have very low cross correlation. In practice, the TDMA and CDMA schemes are combined with FDMA. Thus the term “TDMA” is used to describe systems that first divide the channel into frequency slots and then divide each frequency slot into multiple time slots. Similarly, CDMA is actually a hybrid of CDMA and FDMA where the channel is first divided into frequency slots. Each slot is shared by multiple users who each use a different code. The second generation technologies have particularly been a boon to late liberalised economies. The 2G systems were primarily designed to be voice centric services. Data services were added on later due to demand and to increase facilities available to the users. The data services became extremely popular with the users. With the continuing growth of mobile data applications, an improvement in data rate was required. And a number of upgrades were devised. These new standards were data centric and represented the 2.5G technology. They allowed the existing 2G equipment to be modified and supplemented with new base station add-ons to support higher data rate transmissions. Four main technologies were developed to enhance the data rates. One of the first solutions was the High Speed Circuit Switched Data (HSCSD) General Packet Radio Service (GPRS) was the first system to gain widespread acceptance. Enhanced Data for Global Evolution (EDGE) IS-95B that increased the data rate on CDMA front. The second generation of mobile phones saw rapid growth and expansion of the market. As a consequence of large market, production increased and the technology got cheaper because of the benefits of mass production. A number of markets got saturated. This saturation was one of the driving forces behind the development of the third generation. In order to increase traffic and thus revenues and number of bandwidth intensive services were introduced. The third generation technologies are designed to cater exactly to these needs. Third Generation Mobile communication by 1999 was characterized by a diverse set of applications using many incompatible standards around the world. For today’s mobile communications to become truly personal communications, it will be necessary to consolidate the standards into a single unifying framework. Towards the end of the millennium it was clear that there were insurmountable physical and functional limits to second generation systems. The universal availability of services is an essential prerequisite for making full use of the world’s telecommunication market potential. This led to a world-wide agreement that the third generation systems must be truly innovative with respect to the mobile radio services that were then in service. The new systems must provide services and features which are closer to those provided by fixed systems, in terms of both quality of service and transmission rates. It was evident that both fixed and mobile services should move towards convergence. This project was initially called the Future Public Land Mobile Telecommunications System (FPLMTS). Later it was renamed IMT-2000 for International Mobile Telecommunications. The key characteristics that were required from 3G systems were: Flexibility With the large number of mergers and consolidations occurring in the mobile industry, and the move into international markets, operators wanted to avoid having to support a wide range of different interfaces and technologies. The 3G standard addresses this problem, by providing a highly flexible system, capable of supporting a wide range of services and applications. Affordability There was agreement among industry that 3G systems had to be affordable in order to encourage their adoption by consumers and operators. Compatibility with existing systems 3G services have to be compatible with existing systems through effective and seamless migration paths. Modular Design The vision for 3G systems is that they must be easily expandable in order to allow for growth in users, coverage areas, and new services, with minimum initial investment. Europe has developed a standard known as Universal Mobile Telecommunications Systems (UMTS). This system uses a variant of CDMA known as Wideband CDMA (W-CDMA) with 5MHz channel spacing. It can support both voice and data with a burst rate of 2Mbps. UMTS assures backward compatibility with most of the 2G and 2.5G technologies. Analyses have been performed on the UMTS standards to test the possibility of offering services like virtual reality which can be considered as good representatives of advanced services that would be expected to be offered by 3G systems. The results of these tests have been in favour of UMTS. The main standard that will be used for 3G systems in the US is an evolution of the cdmaOne IS95 system, called CDMA2000. The CDMA2000 standard is a product of several stages of evolution to enable a steady progression from the 2G version to the final 3G version. The first stage of evolution is CDMA2000 1X. It provides both voice and data. The system is quite successful since its deployment in October 2000. By October 2002, there were 44 other 1X systems deployed worldwide. The next stage of evolution is CDMA2000 1xEV-DO, where EV-DO stands for EVolution Data Only. This is defined under the IS-856 standard although it u...