24-07-2012, 12:05 PM
GSM and CDMA Network Modeling
[attachment=28639]
1 INTRODUCTION
1.1 WIRELESS COMMUNICATION
Wireless communication is one of the most vibrant areas in the communication field today. While it has been a topic of study since the 1960s, the past decade has seen a surge of research activities in the area there are two fundamental aspects of wireless communication that make the problem challenging and interesting. These aspects are by and large not as significant in wire line communication. First is the phenomenon of fading the time variation of the channel strengths due to the small-scale effect of multipath fading, as well as larger-scale effects such as path loss via distance attenuation and shadowing by obstacles. Second, unlike in the wired world where each transmitter–receiver pair can often be thought of as an isolated point-to-point link, wireless users communicate over the air and there is significant interference between them. The interference can be between transmitters communicating with a common receiver (e.g., uplink of a cellular system), between signals from a single transmitter to multiple receivers (e.g., downlink of a cellular system), or between different transmitter–receiver pairs (e.g., interference between users in different cells
Traditionally the design of wireless systems has focused on increasing the reliability of the air interface; in this context, fading and interference are viewed as nuisances that are to be countered. Recent focus has shifted more towards increasing the spectral efficiency; associated with this shift is a new point of view that fading can be viewed as an opportunity to be exploited.
1.2 GSM TECHNOLOGY
GSM stands for Global System for Mobile Communication and is an open, digital cellular technology used for transmitting mobile voice and data services. The GSM emerged from the idea of cell-based mobile radio systems at Bell Laboratories in the early 1970s. The GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard. The GSM standard is the most widely accepted standard and is implemented globally. The GSM is a circuit-switched system that divides each 200kHz channel into eight 25kHz time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US. The GSM owns a market share of more than 70 percent of the world's digital cellular subscribers. The GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals. The GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates. Presently GSM support more than one billion mobile subscribers in more than 210 countries throughout of the world. The GSM provides basic to advanced voice and data services including Roaming service. Roaming is the ability to use your GSM phone number in another GSM network. A GSM digitizes and compresses data, then sends it down through a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800 MHz frequency band.
1.3 CDMA TECHNOLOGY
CDMA or Code Division Multiple Access is a form of access scheme that has been widely used within 3G cellular telecommunications systems as well as being used in a number of other technologies as well. CDMA technology gave some significant advantages when compared to the technologies used for previous in terms of overall performance and specifically in terms of spectrum efficiency. CDMA uses spread spectrum technology with the use of different codes to separate between different stations or users rather than different frequencies of time slots as in the case of previous access technologies. In this way, CDMA is different to the previous schemes used to provide different cellular users with access to the radio network.
1.3.1 KEY ELEMENTS OF CDMA
CDMA is a form of spread spectrum transmission technology. It has a number of distinguishing features that are key to spread spectrum transmission technologies:
USE OF WIDE BANDWIDTH: CDMA, like other spread spectrum technologies uses a wider bandwidth than would otherwise be needed for the transmission of the data. This results in a number of advantages including an increased immunity to interference or jamming, and multiple user access.
SPREADING CODES USED: In order to achieve the increased bandwidth, the data is spread by use of a code which is independent of the data.
LEVEL OF SECURITY: In order to receive the data, the receiver must have knowledge of the spreading code, without this it is not possible to decipher the transmitted data, and this gives a measure of security.
MULTIPLE ACCESS: The use of the spreading codes which are independent for each user along with synchronous reception allow multiple users to access the same channel simultaneously.
1.4 EM SIGNAL STRENGTH VARIATIONS
The near field (or near-field) and far field (or far-field) and the transition zone are regions of the electromagnetic field around any object. The different terms for these regions are due to the fact that certain characteristics of an EM field change with distance from the object containing the charges and currents that are the sources of any electromagnetic (EM) field. The basic reason a EM field changes in character with distance from its source, is that Maxwell's equations prescribe different behaviors for each of the two source-terms of electric fields and also the two source-terms for magnetic fields. Electric fields produced by changes in charge distribution have a different character than those produced by changing magnetic fields. Similarly, Maxwell's equations show a differing behavior for the magnetic fields produced by changing electric currents, versus magnetic fields produced by changing electric fields. For these reasons, in the spacial region very close to currents and charge-separations, the EM field is dominated by electric and magnetic components produced directly by currents and charge-separations, and these effects together produce the EM "near field." However, at distances far from charges-separations and currents, the EM field becomes dominated by the electric and magnetic fields indirectly produced by the change in the other type of field, and thus the EM field is no longer affected (or much affected) by the charges and currents at the EM source. This more distant part of the EM field is the "radiative" field or "far-field," and it is the familiar type of electromagnetic radiation seen in "free space," far from any EM field sources (origins). The far-field thus includes radio waves and microwaves several wavelengths from most types of antennas, as well as all the shorter-wave EM radiation in the electromagnetic spectrum (infrared, light, UV, X-rays, etc). The latter types of EM radiation in normal experience show far-field behavior almost exclusively due to their shorter wavelength that gives them”far-field” character at all but extremely short distances from their sources. For example, visible light shows far-field behavior at all distances larger than one micrometer from its source.
In practical mathematical terms, the dominance of far-field behavior with sufficient distance from the source appears because both currents and the oscillating charge-distributions in antennas (and other radiators) produce dipole type field behavior. While these dipole near-field intensities may be very powerful near the source, they decay very rapidly with distance in comparison to EM radiation (the far-field). Radiative far-field intensity decays more slowly with distance, following the inverse square law for total EM power that is typical of all electromagnetic radiation. For this reason, the far-field component of the EM field wins out in intensity with increasing distance. Thus, for objects such as transmitting antennas, electrical or electronic equipment, dielectric materials, or where radiation is scattering from an object, the non radiative 'near field' components of electromagnetic fields dominate the EM field close to the object, while electromagnetic radiation or 'far field' behaviors dominate at greater distances. The near-field does not suddenly end where the far-field begins—rather; there is a transition zone between these types where both types of EM field-effects may be significant.
1.5 INTRODUCTION TO MATLAB
MATLAB (matrix laboratory) is a numerical computing environment and fourth-generation programming language. Developed by Math Works, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, Java, and Fortran. Although MATLAB is intended primarily for numerical computing, an optional toolbox uses the MuPAD symbolic engine, allowing access to symbolic computing capabilities. An additional package, Simulink, adds graphical multi-domain simulation and Model-Based Design for dynamic and embedded systems.
In 2004, MATLAB had around one million users across industry and academia. MATLAB users come from various backgrounds of engineering, science, and economics. MATLAB is widely used in academic and research institutions as well as industrial enterprises. Cleve Moler, the chairman of the computer-science department at the University of New Mexico, started developing MATLAB in the late 1970s. He designed it to give his students access to LINPACK and EISPACK without them having to learn Fortran. It soon spread to other universities and found a strong audience within the applied mathematics community. Jack little, an engineer, was exposed to it during a visit Moler made to Stanford University in 1983. Recognizing its commercial potential, he joined with Moler and Steve Bangert. They rewrote MATLAB in C and founded Math Works in 1984 to continue its development. These rewritten libraries were known as JACKPAC. In 2000, MATLAB was rewritten to use a newer set of libraries for matrix manipulation, LAPACK.
MATLAB was first adopted by researchers and practitioners in control engineering, Little's specialty, but quickly spread to many other domains. It is now also used in education, in particular the teaching of linear algebra and numerical analysis, and is popular amongst scientists involved in image processing.
[attachment=28639]
1 INTRODUCTION
1.1 WIRELESS COMMUNICATION
Wireless communication is one of the most vibrant areas in the communication field today. While it has been a topic of study since the 1960s, the past decade has seen a surge of research activities in the area there are two fundamental aspects of wireless communication that make the problem challenging and interesting. These aspects are by and large not as significant in wire line communication. First is the phenomenon of fading the time variation of the channel strengths due to the small-scale effect of multipath fading, as well as larger-scale effects such as path loss via distance attenuation and shadowing by obstacles. Second, unlike in the wired world where each transmitter–receiver pair can often be thought of as an isolated point-to-point link, wireless users communicate over the air and there is significant interference between them. The interference can be between transmitters communicating with a common receiver (e.g., uplink of a cellular system), between signals from a single transmitter to multiple receivers (e.g., downlink of a cellular system), or between different transmitter–receiver pairs (e.g., interference between users in different cells
Traditionally the design of wireless systems has focused on increasing the reliability of the air interface; in this context, fading and interference are viewed as nuisances that are to be countered. Recent focus has shifted more towards increasing the spectral efficiency; associated with this shift is a new point of view that fading can be viewed as an opportunity to be exploited.
1.2 GSM TECHNOLOGY
GSM stands for Global System for Mobile Communication and is an open, digital cellular technology used for transmitting mobile voice and data services. The GSM emerged from the idea of cell-based mobile radio systems at Bell Laboratories in the early 1970s. The GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard. The GSM standard is the most widely accepted standard and is implemented globally. The GSM is a circuit-switched system that divides each 200kHz channel into eight 25kHz time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US. The GSM owns a market share of more than 70 percent of the world's digital cellular subscribers. The GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals. The GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates. Presently GSM support more than one billion mobile subscribers in more than 210 countries throughout of the world. The GSM provides basic to advanced voice and data services including Roaming service. Roaming is the ability to use your GSM phone number in another GSM network. A GSM digitizes and compresses data, then sends it down through a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800 MHz frequency band.
1.3 CDMA TECHNOLOGY
CDMA or Code Division Multiple Access is a form of access scheme that has been widely used within 3G cellular telecommunications systems as well as being used in a number of other technologies as well. CDMA technology gave some significant advantages when compared to the technologies used for previous in terms of overall performance and specifically in terms of spectrum efficiency. CDMA uses spread spectrum technology with the use of different codes to separate between different stations or users rather than different frequencies of time slots as in the case of previous access technologies. In this way, CDMA is different to the previous schemes used to provide different cellular users with access to the radio network.
1.3.1 KEY ELEMENTS OF CDMA
CDMA is a form of spread spectrum transmission technology. It has a number of distinguishing features that are key to spread spectrum transmission technologies:
USE OF WIDE BANDWIDTH: CDMA, like other spread spectrum technologies uses a wider bandwidth than would otherwise be needed for the transmission of the data. This results in a number of advantages including an increased immunity to interference or jamming, and multiple user access.
SPREADING CODES USED: In order to achieve the increased bandwidth, the data is spread by use of a code which is independent of the data.
LEVEL OF SECURITY: In order to receive the data, the receiver must have knowledge of the spreading code, without this it is not possible to decipher the transmitted data, and this gives a measure of security.
MULTIPLE ACCESS: The use of the spreading codes which are independent for each user along with synchronous reception allow multiple users to access the same channel simultaneously.
1.4 EM SIGNAL STRENGTH VARIATIONS
The near field (or near-field) and far field (or far-field) and the transition zone are regions of the electromagnetic field around any object. The different terms for these regions are due to the fact that certain characteristics of an EM field change with distance from the object containing the charges and currents that are the sources of any electromagnetic (EM) field. The basic reason a EM field changes in character with distance from its source, is that Maxwell's equations prescribe different behaviors for each of the two source-terms of electric fields and also the two source-terms for magnetic fields. Electric fields produced by changes in charge distribution have a different character than those produced by changing magnetic fields. Similarly, Maxwell's equations show a differing behavior for the magnetic fields produced by changing electric currents, versus magnetic fields produced by changing electric fields. For these reasons, in the spacial region very close to currents and charge-separations, the EM field is dominated by electric and magnetic components produced directly by currents and charge-separations, and these effects together produce the EM "near field." However, at distances far from charges-separations and currents, the EM field becomes dominated by the electric and magnetic fields indirectly produced by the change in the other type of field, and thus the EM field is no longer affected (or much affected) by the charges and currents at the EM source. This more distant part of the EM field is the "radiative" field or "far-field," and it is the familiar type of electromagnetic radiation seen in "free space," far from any EM field sources (origins). The far-field thus includes radio waves and microwaves several wavelengths from most types of antennas, as well as all the shorter-wave EM radiation in the electromagnetic spectrum (infrared, light, UV, X-rays, etc). The latter types of EM radiation in normal experience show far-field behavior almost exclusively due to their shorter wavelength that gives them”far-field” character at all but extremely short distances from their sources. For example, visible light shows far-field behavior at all distances larger than one micrometer from its source.
In practical mathematical terms, the dominance of far-field behavior with sufficient distance from the source appears because both currents and the oscillating charge-distributions in antennas (and other radiators) produce dipole type field behavior. While these dipole near-field intensities may be very powerful near the source, they decay very rapidly with distance in comparison to EM radiation (the far-field). Radiative far-field intensity decays more slowly with distance, following the inverse square law for total EM power that is typical of all electromagnetic radiation. For this reason, the far-field component of the EM field wins out in intensity with increasing distance. Thus, for objects such as transmitting antennas, electrical or electronic equipment, dielectric materials, or where radiation is scattering from an object, the non radiative 'near field' components of electromagnetic fields dominate the EM field close to the object, while electromagnetic radiation or 'far field' behaviors dominate at greater distances. The near-field does not suddenly end where the far-field begins—rather; there is a transition zone between these types where both types of EM field-effects may be significant.
1.5 INTRODUCTION TO MATLAB
MATLAB (matrix laboratory) is a numerical computing environment and fourth-generation programming language. Developed by Math Works, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, Java, and Fortran. Although MATLAB is intended primarily for numerical computing, an optional toolbox uses the MuPAD symbolic engine, allowing access to symbolic computing capabilities. An additional package, Simulink, adds graphical multi-domain simulation and Model-Based Design for dynamic and embedded systems.
In 2004, MATLAB had around one million users across industry and academia. MATLAB users come from various backgrounds of engineering, science, and economics. MATLAB is widely used in academic and research institutions as well as industrial enterprises. Cleve Moler, the chairman of the computer-science department at the University of New Mexico, started developing MATLAB in the late 1970s. He designed it to give his students access to LINPACK and EISPACK without them having to learn Fortran. It soon spread to other universities and found a strong audience within the applied mathematics community. Jack little, an engineer, was exposed to it during a visit Moler made to Stanford University in 1983. Recognizing its commercial potential, he joined with Moler and Steve Bangert. They rewrote MATLAB in C and founded Math Works in 1984 to continue its development. These rewritten libraries were known as JACKPAC. In 2000, MATLAB was rewritten to use a newer set of libraries for matrix manipulation, LAPACK.
MATLAB was first adopted by researchers and practitioners in control engineering, Little's specialty, but quickly spread to many other domains. It is now also used in education, in particular the teaching of linear algebra and numerical analysis, and is popular amongst scientists involved in image processing.