28-06-2012, 12:19 PM
wireless networks
[attachment=25894]
ABSTRACT :
Mobile computing is a form of human–computer interaction by which a computer is expected to be transported during normal usage. Mobile computing has three aspects: mobile communication, mobile hardware, and mobile software. The first aspect addresses communication issues in ad-hoc and infrastructure networks as well as communication properties, protocols, data formats and concrete technologies. The second aspect is on the hardware, e.g., mobile devices or device components. The third aspect deals with the characteristics and requirements of mobile applications.
This paper mainly introduces the development of mobile communication systems. In the first section, we briefly review the history of wireless communication and its applications. In the second section we focus on the wireless mobile communication and divide the development course of mobile communication into four generations. Then we show the characteristics of each generation in detail. In the third section, we explain the basic concept of CDMA by examples and discuss two famous standards of CDMA--IS-95 and CDMA2000. In the end, we present our ideas about the future of the wireless mobile communication.
Evolution of Wireless computing:
In 1895, Guglielmo Marconi opened the way for modern wireless communications by transmitting the three-dot Morse code for the letter „S‟ over a distance of three kilometers using electromagnetic waves. From this beginning, wireless communications has developed into a key element of modern society. From satellite transmission, radio and television broadcasting to the now ubiquitous mobile telephone, wireless communications has revolutionized the way societies function.
The evolution of wireless begins here.
Overview of wireless communication :
Wireless communication is an industry developing with high speed. It has a history over only a century since Marconi sent telegraph signals from Cornwall to Saint John which was located in Nufinland 1800 miles away on the other side of the Atlantic Ocean in 1901. The inventions of vacuum tubes (in 1906), semiconductors (in the 1950s) and other new electronic components accelerated the development of wireless communication. Among all the advances of wireless communication, digital technology and the cellular communication network were the most revolutionary. As a result, the wireless communication changed from the analog era to digital era.
Generally speaking, the applications of wireless communication can be classified into four categories.
• shortwave communication and ultra-shortwave communication, which include army broadcasting and military special communication.
• microwave communication, for example vision distance microwave relay.
• satellite communication, such as maritime satellite, television relay, broadcasting and remote sensing.
• mobile wireless communication, including cellular wireless system, paging system，wireless LAN and wireless ATM system.
In recent years mobile wireless communication, especially wireless system and personal communication service, has become the most successful application of the above four categories
2. Development of mobile wireless communication:
The concept of mobile wireless communication began in the 1920s. Some technologies had been developed such as frequency modulation (FM). Originally it was applied to the military communications and then introduced to the civil fields. However, it was the 1970s when mobile wireless communication became a real industry and the mobile telephones were sold as a real commodity. Up to now, mobile wireless communication has gone through two generations in the past twenty years. And currently it is heading for the third generation and beyond the third generation. In the following, the features of each generation are presented.
The first generation:
In 1978, the Bell Laboratory that was located in Chicago and belonged to AT&T developed the first generation of mobile wireless communication system. It was a communications platform that was able to transmit voice signals by the analog frequency modulation technology. And all the users within the system shared the available frequency spectrum (or the wireless channel) by frequency division multiple access (FDMA) technology. FDMA was one of multiple access technologies that the whole available wireless frequency spectrum was divided into many small parts with the same bandwidth. And each part was assigned to a special user in the communication system. As a result wireless resources could be reused to some degree.
The first generation of mobile wireless communication system was a voice-oriented communication system. The most famous systems of the first generation included :
• Advanced mobile phone service (AMPS) system in America and Australia in 1979.
• Nordic mobile telephony (NMT) system in Finland, Norway, Sweden and Denmark in 1981.
• Total access communication system (TACS) in Europe in 1985
However, everything had two sides just as a coin. The first generation of mobile wireless communication system also had some defects [28], such as:
• The capacity of the first generation was limited and its coverage was small. It was not able to hold many users. So its service was very expensive.
• The first generation had no security and encryption technology and so it was subject to intentional attacks and wire tapping.
• The first generation had no seamless roaming function between two networks deployed by different manufacturers.
• The first generation could only transmit voices and did not provide data services. But with the spread of the internet, e-mails increasingly became an important part of people’s lives. So people hoped to build a wireless network supporting the data transmission.
To overcome these defects, researchers began to develop the second generation of mobile wireless communication system.
The second generation :
In the early 1990s, the concept of the second generation was proposed and digital technology as well as the cellular network was accepted in the mobile communication. And these revolutionary advances made wireless communications enter common families. This progress was so great that the number of mobile subscribers almost doubled over a night. Today the second generation systems are still the main wireless network in use.
The second generation system can transmit voices as well as low speed data streams by the digital technology. And the data transmission rate of the second generation is about 64,000 bits per second. The multiple access technology of the second generation systems is CDMA or TDMA. CDMA is the abbreviation of the code division multiple address. It is a technology that different users can send/receive information in the same frequency bandwidth at the same time by means of using a unique code division channels assigned to each of them. TDMA is a technology by which the wireless channel is divided into many time segments and different users can share the channel by transmitting in the different segments [20-25]. The successful applications of the second generation are as follow: [12-14]
• IS-95. In 1993, the CDMA system based on the IS-95 standard was developed in order to improve AMPS system.
• IS-136. In 1994, the TDMA system on the basis of IS-136 standard was developed.
• GSM. In 1991, GSM (global system for mobile communication) on the basis of European telecommunication standards was developed, aiming at improving the performance of the TACS system [11] [19].
[attachment=25894]
ABSTRACT :
Mobile computing is a form of human–computer interaction by which a computer is expected to be transported during normal usage. Mobile computing has three aspects: mobile communication, mobile hardware, and mobile software. The first aspect addresses communication issues in ad-hoc and infrastructure networks as well as communication properties, protocols, data formats and concrete technologies. The second aspect is on the hardware, e.g., mobile devices or device components. The third aspect deals with the characteristics and requirements of mobile applications.
This paper mainly introduces the development of mobile communication systems. In the first section, we briefly review the history of wireless communication and its applications. In the second section we focus on the wireless mobile communication and divide the development course of mobile communication into four generations. Then we show the characteristics of each generation in detail. In the third section, we explain the basic concept of CDMA by examples and discuss two famous standards of CDMA--IS-95 and CDMA2000. In the end, we present our ideas about the future of the wireless mobile communication.
Evolution of Wireless computing:
In 1895, Guglielmo Marconi opened the way for modern wireless communications by transmitting the three-dot Morse code for the letter „S‟ over a distance of three kilometers using electromagnetic waves. From this beginning, wireless communications has developed into a key element of modern society. From satellite transmission, radio and television broadcasting to the now ubiquitous mobile telephone, wireless communications has revolutionized the way societies function.
The evolution of wireless begins here.
Overview of wireless communication :
Wireless communication is an industry developing with high speed. It has a history over only a century since Marconi sent telegraph signals from Cornwall to Saint John which was located in Nufinland 1800 miles away on the other side of the Atlantic Ocean in 1901. The inventions of vacuum tubes (in 1906), semiconductors (in the 1950s) and other new electronic components accelerated the development of wireless communication. Among all the advances of wireless communication, digital technology and the cellular communication network were the most revolutionary. As a result, the wireless communication changed from the analog era to digital era.
Generally speaking, the applications of wireless communication can be classified into four categories.
• shortwave communication and ultra-shortwave communication, which include army broadcasting and military special communication.
• microwave communication, for example vision distance microwave relay.
• satellite communication, such as maritime satellite, television relay, broadcasting and remote sensing.
• mobile wireless communication, including cellular wireless system, paging system，wireless LAN and wireless ATM system.
In recent years mobile wireless communication, especially wireless system and personal communication service, has become the most successful application of the above four categories
2. Development of mobile wireless communication:
The concept of mobile wireless communication began in the 1920s. Some technologies had been developed such as frequency modulation (FM). Originally it was applied to the military communications and then introduced to the civil fields. However, it was the 1970s when mobile wireless communication became a real industry and the mobile telephones were sold as a real commodity. Up to now, mobile wireless communication has gone through two generations in the past twenty years. And currently it is heading for the third generation and beyond the third generation. In the following, the features of each generation are presented.
The first generation:
In 1978, the Bell Laboratory that was located in Chicago and belonged to AT&T developed the first generation of mobile wireless communication system. It was a communications platform that was able to transmit voice signals by the analog frequency modulation technology. And all the users within the system shared the available frequency spectrum (or the wireless channel) by frequency division multiple access (FDMA) technology. FDMA was one of multiple access technologies that the whole available wireless frequency spectrum was divided into many small parts with the same bandwidth. And each part was assigned to a special user in the communication system. As a result wireless resources could be reused to some degree.
The first generation of mobile wireless communication system was a voice-oriented communication system. The most famous systems of the first generation included :
• Advanced mobile phone service (AMPS) system in America and Australia in 1979.
• Nordic mobile telephony (NMT) system in Finland, Norway, Sweden and Denmark in 1981.
• Total access communication system (TACS) in Europe in 1985
However, everything had two sides just as a coin. The first generation of mobile wireless communication system also had some defects [28], such as:
• The capacity of the first generation was limited and its coverage was small. It was not able to hold many users. So its service was very expensive.
• The first generation had no security and encryption technology and so it was subject to intentional attacks and wire tapping.
• The first generation had no seamless roaming function between two networks deployed by different manufacturers.
• The first generation could only transmit voices and did not provide data services. But with the spread of the internet, e-mails increasingly became an important part of people’s lives. So people hoped to build a wireless network supporting the data transmission.
To overcome these defects, researchers began to develop the second generation of mobile wireless communication system.
The second generation :
In the early 1990s, the concept of the second generation was proposed and digital technology as well as the cellular network was accepted in the mobile communication. And these revolutionary advances made wireless communications enter common families. This progress was so great that the number of mobile subscribers almost doubled over a night. Today the second generation systems are still the main wireless network in use.
The second generation system can transmit voices as well as low speed data streams by the digital technology. And the data transmission rate of the second generation is about 64,000 bits per second. The multiple access technology of the second generation systems is CDMA or TDMA. CDMA is the abbreviation of the code division multiple address. It is a technology that different users can send/receive information in the same frequency bandwidth at the same time by means of using a unique code division channels assigned to each of them. TDMA is a technology by which the wireless channel is divided into many time segments and different users can share the channel by transmitting in the different segments [20-25]. The successful applications of the second generation are as follow: [12-14]
• IS-95. In 1993, the CDMA system based on the IS-95 standard was developed in order to improve AMPS system.
• IS-136. In 1994, the TDMA system on the basis of IS-136 standard was developed.
• GSM. In 1991, GSM (global system for mobile communication) on the basis of European telecommunication standards was developed, aiming at improving the performance of the TACS system [11] [19].