Broadband Wireless Systems

                                The market for broadband communications is growing rapidly, and the potential applications and services are numerous and diverse. Several technologies are currently being developed to offer such services. Both wired and wireless system solutions aim to win a share of the market. The wired contenders include digital subscriber lines (xDSL), cable modems and others. The wireless contenders include satellite communications systems, stratospheric communications systems, and terrestrial communications systems, specifically, Multipoint Multichannel Distribution Service (MMDS) and Local Multipoint Distribution Service (LMDS). While these systems do not all target identical market segments, the likely markets do overlap. The various broadband wireless access systems compete therefore more against high-speed wired solutions than against each other. Table III-1 from Allied Business Intelligence, Inc. presents a forecast of market share for various high-speed communication solutions [BWS1]. This forecast projects that wired technologies would command about 75 % of subscribers in the year 2003.

Broadband Subscribers by Technology, US Market, 2003

(source Allied Business Intelligence, Inc.)

ADSL            36 %

Cable Modem 26 %

ISDN             12 %

Satellite           12 %

LMDS          9 %

Others           5 % 

A. Terrestrial Broadband Wireless Systems

     A common way to classify broadband terrestrial, wireless fixed communications systems is to call systems using frequencies below 10 GHz MMDS systems and to call systems using frequencies above 10 GHz LMDS systems. The motivation for this classification is that the propagation characteristics are quite different at say 30 GHz than at 5 GHz. Equipment and components for frequencies under 10 GHz are mature, while equipment at higher frequencies is based on technology that still is relatively new and expensive. Systems at frequencies above 20 GHz are for fixed users. Systems below 10 GHz are also for fixed users, but may evolve to serve mobile users.

The Future of the Wireless Technology

                                        Wireless telephony systems are here to stay in a big way, unlike some other wireless technologies, which are on the drawing board and may never turn into viable commercial products and services. Investment in the wireless telephony industry is at $50.1 billion in capital investments and $20 billion in spectrum auction fees in the US. There are more than 60 million wireless subscribers in the US now, and the average monthly bill per user was at just below $40 in 1998. It is anticipated that there will be 170 million wireless users in the US by 2007; that’s more than 50% of the population.

     The purpose of this subsection is to help identify a NIST role in this important area of information technology. Since the NIST role will be mainly in the terrestrial 3G systems, and it is an accepted fact that the ITU process will result in at least two standards (one for terrestrial and one for satellite systems), we concentrate on terrestrial 3G systems in the rest of this section. At the time of writing of this report, and within eleven months of the completion of the IMT-2000 standard, it is not clear at all whether a single, global standard for terrestrial wireless communication systems will emerge at the end of the ITU standardization effort. There are three major obstacles that have to be removed before there can be such a standard. The 16th Meeting of ITU-R TG8/1 in Brazil in March 1999 will determine how likely it is that these obstacles will be removed, and a single international terrestrial standard for 3G wireless systems developed by the end of 1999. Each of the major obstacles is discussed below.

 1. Manufacturers’ Interest: An IPR (Intellectual Property Rights) conflict between Qualcomm and the European Telecommunications Standards Institute (ETSI) has been in the news for the past several months. Qualcomm is the major force behind TIA’s cdma2000 proposal, and ETSI is the sponsor of the W-CDMA proposal backed by all the European countries. They are both based on wideband CDMA technology, where Ericsson and Qualcomm each have a number of patents. Although the best technical solution would need both sets of patents, it appears that the two camps are trying to find ways around each other's IPR. This would not result in the best technical solution. In summary, each manufacturer’s interest is to influence the development of the IMT-2000 standard so that it is based on as much IPR from that manufacturer as possible. Naturally, this leads to a conflict of interest.

3rd Generation Wireless Systems

3rd Generation Wireless Systems

       The IMT-2000 standard for third-generation wireless systems is presently under development by the ITU-R Task Group 8/1 (R stands for radio). The ITU plans to complete this task by the end of 1999, hence the name IMT-2000 standard [3GW21,3GW8].

      The IMT-2000 standard will offer users transmission rates up to 2 Mbits/sec, global roaming and interoperability, and a much wider array of wireless services. These should be contrasted with the second-generation wireless systems, which provide mainly voice service, some limited data communication capability (e.g., e-mail), and lack of interoperability due to the use of different systems and standards around the world. The transmission rate for second-generation systems is on the order of only tens of kilobits per second. Third-generation systems have the potential to offer users high data rate services such as web browsing (usually involving web pages with multimedia content) and even applications such as video teleconferencing. In the interim, and until systems based on the IMT-2000 standard are deployed some time between 2002 and 2006, the GSM operators plan to offer an enhanced version of the GSM system, called the EDGE system, with service rates up to 384 Kbps. EDGE employs a more spectrally efficient modulation scheme than GSM, as well as some other advanced techniques, but it is not as radical a departure from GSM as are the proposed third-generation systems. Some call EDGE a 2.5-generation system.

      The deadline for submission of proposals for the air interface of the IMT-2000 system to the ITU was June 30, 1998. By that date fifteen RTT (Radio Transmission Technologies) proposals had been submitted, ten on terrestrial systems and five on satellite systems. A sixth satellite system, the Iridium system, was submitted to ITU after the expiration of the June 30 deadline. The Iridium proposal was accepted by ITU, and this brought the total number of RTT proposals under consideration to sixteen. These proposals were developed by national and regional standardization bodies and industry consortia in a handful of countries around the world. Between June 30 and September 30, 1998, these sixteen proposals were evaluated by ten evaluation bodies around the world. Not all evaluation groups evaluated all the sixteen proposals. As a matter of fact, all the evaluations and comparisons were based on the self-evaluations of the proposals made by the proposers themselves. No evaluation body had the time or resources to implement and simulate the different systems and carry out a more in-depth and unbiased evaluation of the proposals.

The period between September 30, 1998 and March 31, 1999 has been designated by the ITU as the time during which harmonization of different proposals is to take place, and a single set of key characteristics for the IMT-2000 standard is to emerge.

1st & 2nd Generation Wireless Systems

1st Generation Wireless Systems

The commercial use of mobile phones started in the US when AT&T developed the AMPS (Advanced Mobile Phone System) system in late 1970’s [3GW9, 3GW1]. AMPS went into service first in Chicago area in 1983. The AMPS system is an analog communication system, which uses frequency modulation (FM) to transmit speech and frequency shift keying (FSK) to transmit important network control information in digital form [3GW10]. The AMPS system was designed primarily for carrying two-way voice conversations. Surprisingly, AMPS remains in use almost sixteen years after its introduction into the market. In fact, AMPS still enjoys 11% share of the cellular communications market in the US. Other analog mobile systems were introduced in Europe and Japan a few years earlier than AMPS was deployed in the US [3GW11]. However, unlike in the US, where AMPS was the only system introduced, European countries developed several incompatible systems. Lack of interoperability soon proved to be a major problem for many European users who regularly traveled to other countries within Europe for business and pleasure. The number of cellular users and the geographic coverage of the system increased steadily, but modestly, in the US. 

 2nd Generation Wireless Systems

In the 1980’s the Europeans recognized the need for a second generation of cellular systems based on digital modulation and transmission schemes, which promised a more efficient use of the available frequency spectrum. This translates into increased total communication capacity and hence the capability to offer cellular service to a larger number of users per unit area. To avoid the interoperability problems encountered with the first-generation systems, the European countries agreed to jointly develop a common system for the entire continent. The result was the Global System for Mobile Communications (GSM), which was first commercially deployed in 1991 [3GW12, 3GW2]. GSM uses many features made possible by adoption of digital technology, such as digital voice compression and encryption. GSM also introduced many innovations in network level architectures and services. The multiple access mechanism in GSM is Time Division Multiple Access (TDMA), where each user in a cell transmits and receives information in time slots allocated to that user. The multiple access mechanism in the first-generation systems is Frequency Division Multiple Access (FDMA), where each user is allocated two bands or channels in the frequency spectrum, one for transmitting information and one for receiving it. GSM was a major success for Europe by all accounts, allowing users to roam all over the continent and yet be able to use their mobile phones. The success of GSM spread throughout the world.

Introduction Wireless Communication Systems

I. Introduction

In the 1960’s voice communication was carried to end subscribers almost exclusively on copper wires running from central office switches to homes and businesses, and television was broadcast to homes almost exclusively through the air modulated on electromagnetic waves. By the late 1980’s, industry pundits began to observe that the situation was reversing itself. Increasingly, voice communication was carried to end subscribers through the air modulated on electromagnetic waves, while television was broadcast to homes on copper coaxial cables (soon to be followed by fiber optic cables). Now, as the 21st century approaches, the situation appears decidedly more complex. Cellular telephony continues to expand at a rapid rate; however, numerous plans exist for igh-speed wireless backbones carried across networks of earth-orbiting satellites, both geostationary and on-stationary, as well as networks of aircraft and balloons. In addition, several companies are devising plans to deploy broadband wireless distribution systems in order to compete with cable and copper twisted pairs for delivering high bandwidth data and television signals to businesses and homes. Further a variety of embedded and portable devices are beginning to appear, carrying built-in picocellular wireless communication transceivers. Two things appear clear. First, during the 21st century, wireless information technology will play a large role in the life of the country’s citizens and in the country’s economy. Second, the wireless technology landscape is so vast and complex that any organization seeking to enter the fray must take careful stock of the opportunities ahead. This white paper, on wireless information technology for the 21st century, aims to inform the trategic decision-making process within the Information Technology Laboratory (ITL) of the National Institute of Standards and Technology (NIST). The paper surveys the vast landscape of wireless information technology. In doing so, the paper attempts: (1) to identify market inhibitors facing various wireless technologies, (2) to make projections about the likely road ahead, and (3) to seek opportunities for the ITL particularly, and NIST more generally, to contribute to the removal of market inhibitors for key wireless technologies.

Information Technology and Globalization

Information and communication technologies (ICTs) have been implicated in the structuring and restructuring of human social relations since the days of cave paintings and fire signals. The development of the electrical telegraph and the telephone in the late 1800s marked a qualitative shift in the scope and power of ICTs, however. The new electrical communication systems brought disparate regions and peoples into an unprecedented, increasingly synchronous global network of information, trade, finance, and culture. In the 20th century, the emerging global telecommunication infrastructure was extended and its uses expanded by the development of radio transmission, satellite communications, and terrestrial broadband networks. More recently, digital encoding, storage, and transmission have allowed for data compression and the convergence of multiple formats into a common digital stream, further accelerating the speed and volume of global information and communication flows. At the same time, the diffusion of inexpensive personal computers, the development of the graphical user interface, and the establishment of common data exchange protocols have given users around the world direct access to an increasing mass of data, text, and multimedia documents-as well as the power to create and distribute such documents themselves.

The integration and interdependence of global media and information systems have created new challenges and new opportunities.

Information Technology and Social Development

For the first time in history the entire planet is capitalist. Even the few remaining command economies are surviving or developing through their linkages to global, capitalist markets. Yet this is a brand of capitalism that is at the same time very old and fundamentally new. It is old because it appeals to relentless competition in the pursuit of profit, and because individual satisfaction (deferred or immediate) is its driving engine. But it is fundamentally new because it is tooled by new information and communication technologies that are at the root of new productivity sources, new organizational forms, and the construction of a global economy.

In the following paper, presented at the UNRISD conference on Information Technologies and Social Development (Geneva, June 1998), Manuel Castells examines the profile of this new world, centred around multinational corporations, global financial markets and a highly concentrated system of technological research and development. He stresses the extreme flexibility of the system, which allows it to link up everything that is valuable according to dominant values and interests, while disconnecting everything that is not valuable, or becomes devalued. This simultaneous capacity to include and exclude people, territories and activities is based upon a capacity to network.
A network is simply a set of interconnected nodes.