The Global System for Mobile communications is a digital cellular communications system. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide. GSM was designed to be compatible with ISDN services.
HISTORY OF GSM :---
The idea of cell-based mobile radio systems appeared at Bell Laboratories (in USA) in the early 1970s. However, mobile cellular systems were not introduced for commercial use until the 1980s. During the early 1980s, analog cellular telephone systems experienced a very rapid growth in Europe, particularly in Scandinavia and the United Kingdom. Today cellular systems still represent one of the fastest growing telecommunications systems.
But in the beginnings of cellular systems, each country developed its own system, which was an undesirable situation for the following reasons:
- The equipment was limited to operate only within the boundaries of each country.
- The market for each mobile equipment was limited.
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In order to overcome these problems, the Conference of European Posts and Telecommunications (CEPT) formed, in 1982, the Groupe Spécial Mobile (GSM) in order to develop a pan-European mobile cellular radio system (the GSM acronym became later the acronym for Global System for Mobile communications). The standardized system had to meet certain criteria:
- Spectrum efficiency
- International roaming
- Low mobile and base stations costs
- Good subjective voice quality
- Compatibility with other systems such as ISDN , PSTN , PSPDN etc.
- Ability to support new services
GSM system is based on digital technology which has many advantages over analog technology. It also provides the technology as ROAMING, SMS, TELETEX, Fax mail.
[ 1 ]GSM
As we have chose the topic “GSM Technologies”
we have made our assignment according to prerequisites or the questions asked in the assignment question.
- Describe the technology involved, giving a clear indication of what the technology is about.
- Describe the importance of the technology (i.e. how the technology has or will affect human beings at work and social life).
- Describe the modulation technique used and basic requirement for successful implementation of the technology (i.e. hardware, software, skills, cost, etc.).
- Describe the security issues of the technology (i.e. any special considerations or pre-requisites such as safety, security, regulation, etc.).
- Describe where such technology is best suited for implementation (i.e. for specific industry and locality).
- Describe the advantages/strengths and disadvantages of the technology.
- Describe the problems during the implementation of such technology.
- Using relevant diagrams and figures provide a simple design of the implementation of the chosen standard.
A) Describe the technology involved, giving a clear indication of what the technology is about.
GSM (Global System for Mobile communications) is an open, digital cellular technology used for transmitting mobile voice and data services.GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US. The 850MHz band is also used for GSM and 3G in Australia, Canada and many South American countries. By having harmonised spectrum across most of the globe, GSM's international roaming capability allows users to access the same services when travelling abroad as at home. This gives consumers seamless and same number connectivity in more than 218 countries.
Terrestrial GSM networks now cover more than 80% of the world's population. GSM satellite roaming has also extended service access to areas where terrestrial coverage is not available.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 . GSM is now used in 219 countries and territories serving more than three billion people and providing travellers with access to mobile services wherever they go.
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.
Architecture of the GSM network
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Marked to Standard
The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements.
The GSM network can be divided into four main parts:
- The Mobile Station (MS).
- The Base Station Subsystem (BSS).
- The Network and Switching Subsystem (NSS).
- The Operation and Support Subsystem (OSS).
The architecture of the GSM network is presented in figure 1.
1. Mobile Station
A Mobile Station consists of two main elements: ---
·The mobile terminal:-- These are distinguished by power & application.
- The Subscriber Identity Module (SIM): -- The SIM is a smart card that identifies the terminal. The SIM card is protected by a four-digit Personal Identification Number (PIN).
Another advantage of the SIM card is the mobility of the users. . In fact, the only element that personalizes a terminal is the SIM card.
2. The Base Station Subsystem
The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception. The BSS can be divided into two parts: ---
- The Base Transceiver Station (BTS) or Base Station.
- The Base Station Controller (BSC).
2.1 The Base Transceiver Station
The BTS corresponds to the transceivers and antennas used in each cell of the network. A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell. Each BTS has between one and sixteen transceivers depending on the density of users in the cell.
2.2 The Base Station Controller
The BSC controls a group of BTS and manages their radio resources. A BSC is principally in charge of handovers, frequency hopping, exchange functions and control of the radio frequency power levels of the BTSs.
3 The Network and Switching Subsystem
Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc. It also includes data bases needed in order to store information about the subscribers and to manage their mobility. The different components of the NSS are described below: ---
3.1 The Mobile services Switching Center (MSC)
It is the central component of the NSS. The MSC performs the switching functions of the network. It also provides connection to other networks.
3.2 The Gateway Mobile services Switching Center(GMSC)
A gateway is a node interconnecting two networks. The GMSC is the interface between the mobile cellular network and the PSTN. It is in charge of routing calls from the fixed network towards a GSM user. The GMSC is often implemented in the same machines as the MSC.
3.3 Home Location Register (HLR)
The HLR is considered as a very important database that stores information of the subscribers belonging to the covering area of a MSC. It also stores the current location of these subscribers and the services to which they have access.
3.4 Visitor Location Register (VLR)
The VLR contains information from a subscriber's HLR necessary in order to provide the subscribed services to visiting users. When a subscriber enters the covering area of a new MSC, the VLR associated to this MSC will request information about the new subscriber to its corresponding HLR. The VLR will then have enough information in order to assure the subscribed services without needing to ask the HLR each time a communication is established.
The VLR is always implemented together with a MSC; so the area under control of the MSC is also the area under control of the VLR.
3.5 The Authentication Center (AuC)
The AuC register is used for security purposes. It provides the parameters needed for authentication and encryption functions. These parameters help to verify the user's identity.
3.6 The Equipment Identity Register (EIR)
The EIR is also used for security purposes. It is a register containing information about the mobile equipments. More particularly, it contains a list of all valid terminals. A terminal is identified by its International Mobile Equipment Identity (IMEI). The EIR allows then to forbid calls from stolen or unauthorized terminals.
3.7 The GSM Interworking Unit (GIWU)
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The GIWU corresponds to an interface to various networks for data communications. During these communications, the transmission of speech and data can be alternated.
4. The Operation and Support Subsystem (OSS)
The OSS is connected to the different components of the NSS and to the BSC, in order to control and monitor the GSM system. It is also in charge of controlling the traffic load of the BSS.
However, the increasing number of base stations, due to the development of cellular radio networks, has provoked that some of the maintenance tasks are transferred to the BTS. This transfer decreases considerably the costs of the maintenance of the system.
The Geographical Areas Of The GSM Network
The figure 2 presents the different areas that form a GSM network.
As it has already been explained a cell, identified by its Cell Global Identity number (CGI), corresponds to the radio coverage of a base transceiver station. A Location Area (LA), identified by its Location Area Identity (LAI) number, is a group of cells served by a single MSC/VLR. A group of location areas under the control of the same MSC/VLR defines the MSC/VLR area. A Public Land Mobile Network (PLMN) is the area served by one network operator.
4.3 The GSM functions
In this paragraph, the description of the GSM network is focused on the different functions to fulfill by the network and not on its physical components. In GSM, five main functions can be defined:
- Radio Resources management (RR).
- Mobility Management (MM).
- Communication Management (CM).
- Operation, Administration and Maintenance (OAM).
1. Frequency allocation
Two frequency bands, of 25 Mhz each one, have been allocated for the GSM system:
- The band 890-915 Mhz has been allocated for the uplink direction (transmitting from the mobile station to the base station).
- The band 935-960 Mhz has been allocated for the downlink direction (transmitting from the base station to the mobile station).
2. Multiple access scheme
The multiple access scheme defines how different simultaneous communications, between different mobile stations situated in different cells, share the GSM radio spectrum. A mix of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA), combined with frequency hopping, has been adopted as the multiple access scheme for GSM.
2.1 FDMA and TDMA
Using FDMA, a frequency is assigned to a user. So the larger the number of users in a FDMA system, the larger the number of available frequencies must be. The limited available radio spectrum and the fact that a user will not free its assigned frequency explain why the number of users in a FDMA system can be "quickly" limited.
On the other hand, TDMA allows several users to share the same channel. Each of the users, sharing the common channel, is assigned his own burst within a group of bursts called a frame. Usually TDMA is used with a FDMA structure.
In GSM, a 25 Mhz frequency band is divided, using a FDMA scheme, into 124 carrier frequencies spaced one from each other by a 200 khz frequency band. Normally a 25 Mhz frequency band can provide 125 carrier frequencies but the first carrier frequencyis used as a guard band between GSM and other services working on lower frequencies. Each carrier frequency is then divided in time using a TDMA scheme. This scheme splits the radio channel, with a width of 200 khz, into 8 bursts. A burst is the unit of time in a TDMA system, and it lasts approximately 0.577 ms. A TDMA frame is formed with 8 bursts and lasts, consequently, 4.615 ms. Each of the eight bursts, that form a TDMA frame, are then assigned to a single user.
2.2 Channel structure
A channel corresponds to the recurrence of one burst every frame. It is defined by its frequency and the position of its corresponding burst within a TDMA frame. In GSM there are two types of channels:
- The traffic channels used to transport speech and data information.
- The control channels used for network management messages and some channel maintenance tasks.
B)Describe the importance of the technology (i.e. how the technology has or will affect human beings at work and social life).
Ans:-The economic and social impact of GSM
Mobile telecommunications is becoming one of the most important industries in the world. According to a report in 2003(US), mobile telecom services directly generated over $426bn in revenues. Further, the global revenues attributable to GSM totalled circa $277bn in 2003, a 19% increase over 2002. It was estimated that revenues would increase to $500bn by 2005. The technological challenges of introducing a new 2nd Generation digital technology such as GSM, have wrought significant economic changes on the value chain of the mobile industry that directly embraces mobile operators, equipment providers, component suppliers, retailers and a large segment of the software market. Meeting these challenges involved the interplay of various clusters of technologies and competencies, the adaptation of new and existing technologies, and the appearance of specialist manufacturers. Each of these industries has created employment opportunities, many of which have directly resulted from the global emergence of GSM. [18 February 2004 Telecommunications GSM White Paper Page 4 Deutsche Bank AG]
We estimate that mobile telephony has created 4.1m jobs worldwide and within this we believe GSM itself accounts for circa 75%. Following a couple of recent weaker years, we believe job creation will recommence and expect the industry to reach 10m employees by 2010.
In human terms, having access to a pocket sized mobile terminal has had a profound impact on society; empowering users with the freedom and convenience to conduct their affairs without being tethered to a wall, a terminal, or even a specific geographic location. The popularity and growth of mobile phones in society is changing the way we work and engage in our social interactions. The GSM mobile handset has also become more than just a phone; it is a very personal item and valued form of self-expression. Almost no other item is carried everywhere by users in quite the same way. But apart from the value of self-expression, the GSM handset has made its presence felt by changing the nature of social communications, allowing not only voice, but also creating textual modes as new, creative forms of dialogue. But perhaps the most far-reaching social consequences of GSM telephony have been felt in low income economies. The deployment of GSM has helped to bridge the digital divide and bring modern telecommunications services to chronically underserved communities in Africa, Asia and Latin America. In the developing world, many countries are effectively starting “from scratch” when it comes to telecommunications; therefore, very large sums of money are needed. For the world's poorest countries, GSM mobile wireless represents the best chance of bringing the power of telecommunications to their economically disadvantaged or isolated communities. We have presented two case studies — in Nigeria and Afghanistan - to highlight how quickly and how completely GSM can be deployed; and substituted for fixed line telephones. Undoubtedly, 3G will have a disruptive effect on the telecommunications industry, but its realisation will occur not through revolution, but rather graceful evolution from today's existing 2G infrastructure. The massive global deployment of GSM technology across 200 countries, and its global reach, necessitates the coexistence and reuse of GSM infrastructure. More importantly, backward compatibility with existing networks is vital to ensure that users enjoy the benefits of new 3G features and services, while continuing to enjoy the global coverage and roaming capabilities that they have come to expect from GSM. In that context, *3GSM represents the evolution of GSM to 3G that should culminate in a new W-CDMA air interface that will allow for coexistence of the current and new architecture and facilitate the reuse of the global GSM footprint.
After a few turbulent years for the industry, we highlight some of the key factors we view as critical for the continued success of GSM. These include:
Ø Enabling convergence with other wireless technologies
Ø Developing Mobile Centric Applications
Ø Evolving the mobile business model
Ø Mobile terminal enhancements and variety
Ø Fostering industry partnerships and co-operations
Ø Interoperability and Inter-generational roaming between various platforms.
C) Describe the modulation technique used and basic requirement for successful implementation of the technology (i.e. hardware, software, skills, cost, etc.).
Ans:-Gaussian Minimum Shift Keying, or to give it its full title Gaussian filtered Minimum Shift Keying, GMSK, is a form of modulation used in a variety of digital radio communications systems. It has advantages of being able to carry digital modulation while still using the spectrum efficiently. One of the problems with other forms of phase shift keying is that the sidebands extend outwards from the main carrier and these can cause interference to other radio communications systems using nearby channels.
In view of the efficient use of the spectrum in this way, GMSK modulation has been used in a number of radio communications applications. Possibly the most widely used is the GSM cellular technology which is used worldwide and has well over 3 billion subscribers.
GMSK modulation is based on MSK, which is itself a form of phase shift keying. One of the problems with standard forms of PSK is that sidebands extend out from the carrier. To overcome this, MSK and its derivative GMSK can be used.
MSK and also GMSK modulation are what is known as a continuous phase scheme. Here there are no phase discontinuities because the frequency changes occur at the carrier zero crossing points. This arises as a result of the unique factor of MSK that the frequency difference between the logical one and logical zero states is always equal to half the data rate. This can be expressed in terms of the modulation index, and it is always equal to 0.5.
Signal using MSK modulation
A plot of the spectrum of an MSK signal shows sidebands extending well beyond a bandwidth equal to the data rate. This can be reduced by passing the modulating signal through a low pass filter prior to applying it to the carrier. The requirements for the filter are that it should have a sharp cut-off, narrow bandwidth and its impulse response should show no overshoot. The ideal filter is known as a Gaussian filter which has a Gaussian shaped response to an impulse and no ringing. In this way the basic MSK signal is converted to GMSK modulation.
Spectral density of MSK and GMSK signals
Generating GMSK modulation:
There are two main ways in which GMSK modulation can be generated. The most obvious way is to filter the modulating signal using a Gaussian filter and then apply this to a frequency modulator where the modulation index is set to 0.5. This method is very simple and straightforward but it has the drawback that the modulation index must exactly equal 0.5. In practice this analogue method is not suitable because component tolerances drift and cannot be set exactly.
Generating GMSK using a Gaussian filter and VCO
A second method is more widely used. Here what is known as a quadrature modulator is used. The term quadrature means that the phase of a signal is in quadrature or 90 degrees to another one. The quadrature modulator uses one signal that is said to be in-phase and another that is in quadrature to this. In view of the in-phase and quadrature elements this type of modulator is often said to be an I-Q modulator. Using this type of modulator the modulation index can be maintained at exactly 0.5 without the need for any settings or adjustments. This makes it much easier to use, and capable of providing the required level of performance without the need for adjustments. For demodulation the technique can be used in reverse.
Block diagram of I-Q modulator used to create GMSK
Advantages of GMSK modulation:
There are several advantages to the use of GMSK modulation for a radio communications system. One is obviously the improved spectral efficiency when compared to other phase shift keyed modes.
A further advantage of GMSK is that it can be amplified by a non-linear amplifier and remain undistorted This is because there are no elements of the signal that are carried as amplitude variations. This advantage is of particular importance when using small portable transmitters, such as those required by cellular technology. Non-linear amplifiers are more efficient in terms of the DC power input from the power rails that they convert into a radio frequency signal. This means that the power consumption for a given output is much less, and this results in lower levels of battery consumption; a very important factor for cell phones.
A further advantage of GMSK modulation again arises from the fact that none of the information is carried as amplitude variations. This means that is immune to amplitude variations and therefore more resilient to noise, than some other forms of modulation, because most noise is mainly amplitude based.
Ø Mobile phone access points, known as BTS(base transceiver station) units.
Ø An industry standard server to run the BTS Control Software and GSM software.
The GSM software consists of three software components:
Ø A mobile switching centre (MSC), translation and routing
Ø Database and a short message service centre (SMSC)
Ø The GSM Exchange includes a forth option to provide GPRS using an industry standard GSN(GPRS Service Node).
Factory shipments for GSM mobile telecommunications equipment (BTS, BSC,MSC) worldwide has averaged $25bn YoY pa. If we were to look at it simply interms of the direct impact of GSM, where there are currently 616 networks on airworldwide, each would require a large number of Base Transceiver Sites (BTS) andBase Station Controllers (BSC). Typical costs for a fully equipped 3-sector BTS site
range between Euro 100-300K, while a BSC ($4m each) handles around 50-100 BTS sites depending on the manufacturer. To get an idea of the scale, consider Vodafone in the UK, which has a GSM network of 6,000 BTS sites, or perhaps O2, which also has around 6,000 BTS. This is in contrast to T-Mobile and Orange (who operate at higher frequency bands) in the UK who have 12,000 BTS sites each. All this is, simply, to provide national coverage throughout an island (the UK) the size of the state of Victoria in Australia. Multiply that by the 616 GSM networks throughout the world and one is looking at an installed first cost of approximately $300bn since the inception of GSM. The extraordinary growth in GSM mobile networks throughout the world has fuelled the need for more mobile switching centre (MSC) capacity. MSC's are essentially CLASS 5 type telecommunications switching nodes and are the centre point of interconnection with all the other entities that make up a mobile network. They also provide the necessary inter-working between the mobile network and the Public Switched Telephone Network (PSTN).
18 February 2004 Telecommunications GSM White Paper
D) Describe the security issues of the technology (i.e. any special considerations or pre-requisites such as safety, security, regulation, etc.).
Security in GSM consists of the following aspects:
- Subscriber identity authentication
- Subscriber identity confidentiality
- Signaling data confidentiality
- User data confidentiality.
The subscriber is uniquely identified by the International Mobile Subscriber Identity (IMSI). This information, along with the individual subscriber authentication key (Ki), constitutes sensitive identification credentials analogous to the Electronic Serial Number (ESN) in analog systems such as AMPS and TACS. The design of the GSM authentication and encryption schemes is such that this sensitive information is never transmitted over the radio channel. Rather, a challenge-response mechanism is used to perform authentication. The actual conversations are encrypted using a temporary, randomly generated ciphering key (Kc). The MS identifies itself by means of the Temporary Mobile Subscriber Identity (TMSI), which is issued by the network and may be changed periodically (i.e. during hand-offs) for additional security.
The security mechanisms of GSM are implemented in three different system elements; the Subscriber Identity Module (SIM), the GSM handset or MS, and the GSM network. The SIM contains the IMSI, the individual subscriber authentication key (Ki), the ciphering key generating algorithm (A8), the authentication algorithm (A3), as well as a Personal Identification Number (PIN). The GSM handset contains the ciphering algorithm (A5).The Authentication Center (AUC), part of the Operation and Maintenance Subsystem (OMS) of the GSM network, consists of a database of identification and authentication information for subscribers. This information consists of the IMSI, the TMSI, the Location Area Identity (LAI), and the individual subscriber authentication key (Ki) for each user. In order for the authentication and security mechanisms to function, all three elements (SIM, handset, and GSM network) are required. This distribution of security credentials and encryption algorithms provides an additional measure of security both in ensuring the privacy of cellular telephone conversations and in the prevention of cellular telephone fraud.
The following figure demonstrates the distribution of security information among the three system elements, the SIM, the MS, and the GSM network.
Distribution of Security Features in the GSM Network
The GSM network authenticates the identity of the subscriber through the use of a challenge-response mechanism. A 128-bit random number (RAND) is sent to the MS. The MS computes the 32-bit signed response (SRES) based on the encryption of the random number (RAND) with the authentication algorithm (A3) using the individual subscriber authentication key (Ki). Upon receiving the signed response (SRES) from the subscriber, the GSM network repeats the calculation to verify the identity of the subscriber. Note that the individual subscriber authentication key (Ki) is never transmitted over the radio channel. It is present in the subscriber's SIM, as well as the AUC, HLR, and VLR databases as previously described. If the received SRES agrees with the calculated value, the MS has been successfully authenticated and may continue. If the values do not match, the connection is terminated and an authentication failure indicated to the MS. Figure 2 shown below illustrates the authentication mechanism.
The calculation of the signed response is processed within the SIM. This provides enhanced security, because the confidential subscriber information such as the IMSI or the individual subscriber authentication key (Ki) is never released from the SIM during the authentication process.
Signaling and Data Confidentiality:
The SIM contains the ciphering key generating algorithm (A8) which is used to produce the 64-bit ciphering key (Kc). The ciphering key is computed by applying the same random number (RAND) used in the authentication process to the ciphering key generating algorithm (A8) with the individual subscriber authentication key (Ki). As will be shown in later sections, the ciphering key (Kc) is used to encrypt and decrypt the data between the MS and BS. An additional level of security is provided by having the means to change the ciphering key, making the system more resistant to eavesdropping. The ciphering key may be changed at regular intervals as required by network design and security considerations. Figure 6 below shows the calculation of the ciphering key (Kc).
In a similar manner to the authentication process, the computation of the ciphering key (Kc) takes place internally within the SIM. Therefore sensitive information such as the individual subscriber authentication key (Ki) is never revealed by the SIM.
Encrypted voice and data communications between the MS and the network is accomplished through use of the ciphering algorithm A5. Encrypted communication is initiated by a ciphering mode request command from the GSM network. Upon receipt of this command, the mobile station begins encryption and decryption of data using the ciphering algorithm (A5) and the ciphering key (Kc). Figure 7 below demonstrates the encryption mechanism.
Subscriber Identity Confidentiality:
To ensure subscriber identity confidentiality, the Temporary Mobile Subscriber Identity (TMSI) is used. The TMSI is sent to the mobile station after the authentication and encryption procedures have taken place. The mobile station responds by confirming reception of the TMSI. The TMSI is valid in the location area in which it was issued. For communications outside the location area, the Location Area Identification (LAI) is necessary in addition to the TMSI. The TMSI allocation/reallocation process is shown in Figure 8 below.
This section focuses on key length as a figure of merit of an encryption algorithm. Assuming a brute-force search of every possible key is the most efficient method of cracking an encrypted message (a big assumption), Table 1 shown below summarizes how long it would take to decrypt a message with a given key length, assuming a cracking machine capable of one million encryptions per second.
Table 1 Brute-force key search times for various key sizes
Key length in bits
Time required to test all possible keys
10.8 x 10^24 years
A machine capable of testing one million keys per second is possible by today's standards. It is generally accepted that DES with its 56-bit key will have reached the end of its useful lifetime by the turn of the century for protecting data such as banking transactions. Assuming that the A5 algorithm has an effective key length of 40 bits (instead of 64), it currently provides adequate protection for information with a short lifetime. A common observation is that the "tactical lifetime" of cellular telephone conversations is on the order of weeks.
(F) Describe the advantages/strengths and disadvantages of the technology.
Advantages of GSM:
- GSM is already used worldwide with over 456 million GSM subscribers versus CDMA's 82 million.
- International roaming permits subscribers to use one phone throughout Western Europe. CDMA will work in Asia, but not France, Germany, the U.K. and other popular European destinations. GSM covers virtually all parts of the world so international roaming is not a problem.
- GSM is mature, having started in the mid-80s. This maturity means a more stable network with robust features. CDMA is still building its network.
- GSM's maturity means engineers cut their teeth on the technology, creating an unconscious preference.
- The availability of Subscriber Identity Modules, which are smart cards that provide secure data encryption give GSM m-commerce advantages.
- In brief, GSM is a "more elegant way to upgrade to 3G," says Strategis Group senior wireless analyst Adam Guy.
- Less signal deterioration inside buildings.
- Ability to use repeaters.
- Talktime is generally higher in GSM phones due to the pulse nature of transmission.
- The availability of Subscriber Identity Modules allows users to switch networks and handsets at will.
- GSM covers virtually all parts of the world so international roaming is not a problem.
Disadvantages of GSM:
- Lack of access to burgeoning American market.
- Pulse nature of TDMA transmission used in 2G interferes with some electronics, especially certain audio amplifiers. 3G uses W-CDMA now.
- Intellectual property is concentrated among a few industry participants, creating barriers to entry for new entrants and limiting competition among phone manufacturers.
- GSM has a fixed maximum cell site range of 35 km, which is imposed by technical limitations.
- The data packets are not coded appropriately thus, loss of data.
(G)Describe the problems during the implementation of such technology.
We did'nt come across any problems during the implementation of GSM.
Advantages & Disadvantages of GSM :-
3. 'The GSM tutorial'. Web document found in: http://www.iec.org