JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards

Evolution of Personal Communications

History of the Cellular Radio Service

During the 1980's, the more advanced national PTTs focused their marketing attention on providing a telephone service to mobile subscribers. The first public radio telephone nets had been introduced during the seventies, based on the cellular concept for frequency reuse. Some initial systems, often operating in the 150 MHz band, only supported operator-assisted calls without automatic handover. To provide enhanced user capacity with improved and automatic services, Sweden, Norway, Denmark, Belgium, The Netherlands, Switzerland and Austria implemented (slightly different) versions of the Nordic Mobile Telephone (NMT) system. These analogue systems all use Frequency Division Multiple Access (FDMA). The system was set up in the 450 MHz band, and was later also deployed in the 900 MHz band. At the end of the 1980's, the various versions of the NMT system had a total of nearly a million subscribers. By 1989, the analogue Total Access Communication System (TACS) had approximately 750,000 subscribers in Great-Britain. In France, the Radiocom network had about 165,000 subscribers and in Germany, the C450-network (NETZ-C) had another 165,000 subscribers. In the US, the Advanced Mobile Phone System (AMPS) and American Radio Telephone System (ARTS) had a total of 2 million subscribers in 1988.

The GSM digital cellular telephone net was introduced in Europe in the 900 MHz band in the early 1990's. The acronym GSM originally stood for "Groupe Special Mobile" but later the name "Global System for Mobile communication" was adopted. The system employs Time Division Multiple Access (TDMA) of 8 subscriber signals per channel. The channel bit rate is 270.8 kbit/s and Gaussian Minimum Shift Keying (GMSK) is used. The system is suited for voice communication as well as for circuit-switched data communication.

In the US, the IS54 digital cellular concepts proposes a channel bit rate of 48.6 kbit/s, using pi/4 Differential Quadrature Phase Shift Keying (DQPSK) modulation on a 830 MHz carrier. A TDMA access scheme with three subscribers on each channel is proposed to ensure compatibility with the 30 kHz frequency spacing used for existing AMPS analogue networks. Voice is coded into 8 kbit/s, and including error control coding and signaling the bit rate per subscriber is 16.2 kbit/s.

From observing the developments in the late 1980's, Donald Cox concluded that the technology of personal communication progressed along two completely separate evolutionary paths: high-power vehicular cellular mobile radio technology, and low-power pedestrian and stationary cordless telephone technology. The two techniques are essentially different. The vehicular cellular technology has been developed during the last 45 years, and new systems are still designed to meet the standards of the wireline telephony service. In contrast to this, the history of the handheld cordless telephone is, at most, 15 years and the system is designed with a focus on miniaturization at the cost of some services. Particularly, restrictions imposed by power consumption are relevant to handheld sets. Power-demanding digital processing operations, such as forward error- correction coding, speech coding and multipath channel equalization are extensively employed in the proposed system for future vehicle telephone nets, but still appear impractical in low- powered handheld sets. Reduction of the power consumption during the standby mode is one of the reasons why the user of a cordless set can initiate a telephone call, but cannot receive calls unless a paging system is included. Nonetheless, with the market introduction of GSM, marketers mainly described it as a handheld system.

A number of systems for personal communications have been introduced or proposed. In the UK subscribers can make a telephone connection using a handset within a few hundred meters from a "Telepoint" base station. The Digital European Cordless Telephone (DECT) network is a further development of such a personal system, aimed at pan-European standardization of wireless PBXs. The band 1880 to 1900 MHz has been designated to the DECT service. The development and design of such systems does not only address carefully combining spectrum efficiency and performance objectives, but also has to meet constraints on power consumption.

Personal Communications

Personal Communication Services or PCS will provide broad range of radio communication services (including cordless, cellular, paging, mobile data etc.). These services free individuals from the constraints of wireline PSTN and enable them to communicate when they are away from their home or their office telephone.

Photo: The personal wrist communicator was science fiction in "Dick Tracy", a book published in 1930, but taken seriously by Philips Semiconductors in their vision for 2002.

Evolution Path

The evolution of wireless went as follows:

Generation:
1 2 2.5 3
CT1
CT2, DECT
converge with cellular PCS
AMPS, NMT
GSM, D/E-AMPS, ADC, JDC

Cellular Based PCS, 2.5G

GPRS, IS-95C, HSCSD, EDGE

Mobitex
converge with cellular PCS


Cellular and cordless converge into future systems, such as UMTS

Third Generation

3G widely uses CDMA technology. Licenses for 3G networks have been auctioned in many countries in 2000. Mobile Internet, particularly based on the WAP protocol, is seen by many as the driving market factor.

Fourth Generation

4G systems are intended to provide a very "open architecture" to allow flexible introduction of new features, services and business models. Augmented reality is one of the topics of interest.

 

 

Slides of Wireless Systems and their Evolution

 

Exercise 1

Make a summary of the most essential differences between DECT and GSM. Make sure you cover technical differences but also aspects seen by

Exercise 2

Analyze the message traffic generated by the following services and applications For each of the above applications,
  1. determine which one of the following systems would be your favorite choice to support its teletraffic requirements
  2. determine whether it would be useful to to combine two different transmission systems to support the application
  3. For the other systems than the one selected under (1), give the most relevant disadvantage.

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