Tài liệu Điện thoại di động mạng lưới Radio P16 ppt

16 The Future is Wireless 16.1 A Typical Day in the Year 2000 Joe Mobilus is a manager with a haulage firm in a city 100 km away from his home town; his wife Sue is a nurse at the local hospital. Their son Tom and daughter Ann are still at school. 06:30 The central alarm system wakes Joe and Sue in line with their weekly schedule. 07:00 Joe uses his TETRA terminal to access his firm’s central computer to see if there have been any changes to his diary. 07:15 Joe leaves his house and using his cellular phone in the car calls the traffic service to find out about current traffic conditions. 07:30 Tom, who is finishing school this year and wants to become a stock- broker, calls up a stock market service on the Internet to have the share prices from New York conveyed over satellite. Then, together with his sister, he leaves to go to school. The Mobilus household is linked to the PSTN/ISDN over an RLL system. 08:00 Sue’s cordless DECT telephone rings while Sue is in the bath. Her mother informs her that she has to postpone the joint dinner that was planned for that evening. 08:10 Sue informs Joe accordingly, over a pager or the GSM short-message service. 08:15 Joe’s car breaks down as he is driving to work. He activates the auto- matic emergency service for his car to call for help with a puncture. To do so, he uses a TETRA service or GSM-SMS. 08:20 Because Joe is not sure whether he will make it to the office on time, he sends his secretary an e-mail from his mobile data terminal with the message that she should change his 9 o’clock appointment to a later time. This message is served by GPRS, a non-transparent GSM data service. Mobile Radio Networks: Networking and Protocols. Bernhard H. Walke Copyright © 1999 John Wiley & Sons Ltd ISBNs: 0-471-97595-8 (Hardback); 0-470-84193-1 (Electronic) 806 16 The Future is Wireless 10:00 Joe has arrived in his office, where he receives a message that a client’s warehouse flooded because of heavy rain during the night and that the goods being delivered should be diverted to a different address. 10:05 The firm’s TETRA system enables Joe to make a group call to the vehicles that are just on their way to the warehouse to notify them of the new address. 11:00 A customer order requires Joe to spend a long time working closely with Mr. Jones, another employee of the firm, who has his workstation on another floor of the building. To save time, Mr. Jones has his work- station transferred next to Joe’s. This can be done with no problems, because the company has installed a HIPERLAN. 13:00 Sue, who has been working in the hospital for four hours, is just looking after the patient in room 8 when she is paged over ERMES. The ERMES terminal indicates that she is urgently needed in casualty admissions. 14:00 Joe has to talk to several colleagues jointly at the branch in Russia about a decision concerning a cooperation agreement with a Russian haulage company. He is able to reach them easily over the satellite radio system IRIDIUM, but video conferencing is unfortunately not available. 15:00 Tom is called at home by a school friend. Because the friend was ill, he was unable to attend classes today. He asks Tom to send him the homework that was handed out in maths class today. Using the fax machine connected to the DECT system, Tom is able to send the information that was requested. 17:00 Ann, who is out shopping with her friend Jane, finds a nice shirt that she wants to give her father for his birthday. Because she is not sure which size to take, she goes to a pedestrian zone to call up her mother using her DECT handset over a Telepoint service. 18:00 On the way home, Mr. Mobilus is informed over his cellular phone that he has to visit a customer in Rome the next day. He is able to book his air tickets and hotel reservations through a travel service from his car. 19:30 After an evening meal with his family, Joe arranges for the data he needs from his firm for his appointment in Rome to be displayed on his GPRS/GSM data terminal so he can have it printed out. 16.2 Wireless Communication in the Year 2005 Instead of having many different mobile radio systems and the associated terminals, each modern user will have a software radio that, using the software- defined configuration of the mobile terminal, adapts to the grade of service 16.3 Closing Remarks 807 of the radio interface, depending on the service and the location, and largely makes decisions independently. Because of the flexibility that this allows the user in selecting services, the mobile network operators have entered into a price war and are offering confusing, particularly reasonable rates supposedly restricted to certain user groups. Modern users have a program installed within their terminal that always selects the best rate specific to the current receive situation and to the service to ensure that the software radio is switched to the corresponding mode and the most favourable mobile radio service is being used. UMTS-based PLMNs have been established, but are still available only in highly crowded areas. The main mobile radio service in the large areas is still served by second-generation systems like GSM. There is no longer a restriction to narrowband services in hot communi- cations traffic spots (like airports, sports arenas, fairs, etc.), because even broadband (ATM- and IP-based) services are now available as wireless ser- vices at broadband terminals. However, the costs for these services are still so high that only business users can take advantage of them and afford the appropriate terminals. Since the narrowband telecommunications services of the fixed network (telephony and data) have already been widely introduced over the Internet and have bearable real-time characteristics, the packet-based GPRS speech transmission is being extensively used for mobile calls because it is less ex- pensive than the standard GSM telephone service. The GPRS has also been adopted by the UMTS. All mobile radio services have fallen dramatically in cost of usage and are at almost the same cost levels as the corresponding fixed network services, which are much lower in prize than in the late 1990s. 16.3 Closing Remarks Our society is being characterized by increasing individual mobility and the growing need for an exchange of information. To be successful in domestic and international markets in the future, com- panies and their employees inevitably have to be contactable at all times, wherever they are and with the greatest confidentiality, and also have to have access to the most up-to-date information. The more mobile employees of a company are, the more difficult it is for them to be reached and to have access to important information early enough unless they use mobile radio services. Because of the variety of application areas they are used in, mobile radio systems are also becoming increasingly im- portant for private use. Thus newest-generation mobile radio systems, which have established themselves in the commercial world, will become increasingly cheaper through mass production, and therefore will appeal to an ever-growing group of customers. 808 16 The Future is Wireless The advantages of mobile radio systems and the evident trend towards uni- versal systems in the future, which enable parallel transmission of voice, text, data and images over one connection, thus allowing multimedia information exchange based on UMTS and IMT 2000, will lead to a rapid increase in the number of mobile radio users. Third-generation systems will combine radio-based and fixed networks into a standard architecture. This kind of network will consist of public and pri- vate terrestrial components, as well as ground or space components from radio-based networks combined in a way that a subscriber can use a stan- dard terminal, the so-called Personal Communicator, to take advantage of all the services offered by all networks available today and those that will be operating in the next few years. There is no conclusive response to the question repeatedly being discussed in the media about possible repercussions to health arising from cellular tele- phone use. Intensive studies are being conducted today on the biological effects of electromagnetic radiation in the mobile radio area in order to define meaningful limit values for acceptable radiation levels. Because they are almost always physically separate, fixed radio facilities for mobile telephone systems are only playing a minor role as potential sources of danger due to electrosmog. Mobile equipment with integrated transmit- ting antennas that radiate high-frequency waves near the head warrant more concern. Most of the absorbed energy is converted into heat, and increases the temperature of the body. In tests carried out on animals and simulated human heads it has been determined that the metabolism, the nervous sys- tem and behaviour can be affected even with an additional temperature rise of 1 . The World Health Organization and the national offices for radiation pro- tection of many countries therefore recommend threshold values for the spe- cific absorption and maximum power output (EIRP) of transmitting facilities that are not to be exceeded, along with guidelines on the minimum permitted distance between equipment or its antennas and a person’s body. Besides the thermal effect of electromagnetic radiation, non-thermal effects can also occur. These have been investigated for more than a decade, but there are still no definitive statements about possible impacts of mobile radio waves on humans. The results of further scientific studies will influence the development and suitable protective measures as well as the acceptance of mobile radio systems. There is sufficient experience with human exposure to sources of danger, e.g., from cars and with electrical power. Even if future research results point to a calculable danger from electrosmog due to handset use, this will hardly have any impact on acceptance. The danger-to-use consideration of individual mobile radio users will probably be similar to what happened with the use of cars and electricity. . to the service to ensure that the software radio is switched to the corresponding mode and the most favourable mobile radio service is being used. UMTS-based. 2005 Instead of having many di erent mobile radio systems and the associated terminals, each modern user will have a software radio that, using the software- defined