What is a GSM Technology : Architecture & Its Applications

Digital cellular technology like GSM (Global System for Mobile Communication) is used to transmit mobile data as well as voice services. This concept was implemented at Bell Laboratories using a mobile radio system in 1970. As the name suggests, it is the standardization group name that was established in the year1982 to make a general European mobile telephone standard. This technology owns above 70% of the market share of the digital cellular subscriber around the world. This technology was developed by using digital technology. At present, GSM technology supports above 1 billion mobile subscribers around the world in the above 210 countries. This technology provides voice and data services from fundamental to complex. This article discusses an overview of GSM technology.

What is GSM Technology?

GSM is a mobile communication modem; it stands for global system for mobile communication (GSM). The idea of GSM was developed at Bell Laboratories in 1970.  It is a widely used mobile communication system in the world. GSM is an open and digital cellular technology used for transmitting mobile voice and data services operate at the 850MHz, 900MHz, 1800MHz, and 1900MHz frequency bands.

GSM technology was developed as a digital system using the time division multiple access (TDMA) technique for communication purposes. A GSM digitizes and reduces the data, then sends it down through a channel with two different streams of client data, each in its own particular time slot. The digital system has the ability to carry 64 kbps to 120 Mbps of data rates.

There are various cell sizes in a GSM system such as macro, micro, pico, and umbrella cells. Each cell varies as per the implementation domain. There are five different cell sizes in a GSM network macro, micro, pico, and umbrella cells. The coverage area of each cell varies according to the implementation environment.

The time division multiple access (TDMA) technique relies on assigning different time slots to each user on the same frequency. It can easily adapt to data transmission and voice communication and can carry 64kbps to 120Mbps of data rate.

GSM Technology Architecture

The main elements in the GSM architecture include the following.

• Network and Switching Subsystem (NSS)
• Base-Station Subsystem (BSS)
• The mobile station (MS)
• Operation and Support Subsystem (OSS)

Network Switching Subsystem (NSS)

In GSM system architecture, it includes different elements, which are frequently known as the core system/network. Here, it is basically a data network including a variety of units to provide the major control as well as interfacing of the entire mobile network system. The core network includes the major elements which are discussed below.

Mobile Switching Centre (MSC)

The Mobile Switching Centre or MSC is the key element in the core network region of the GSM network architecture. This mobile services switching center works like a standard switching node in an ISDN otherwise PSTN, however, it also gives extra functionality to allow the mobile user necessities to be supported like authentication, registration, inter-MSC handovers call location & routing of the call to a cell phone subscriber.

And, it also provides an edge toward the public switched telephone network so that the phone calls can be connected from the network of the mobile to a phone to a landline. Interfaces to other mobile switching center server are provided to allow mobile calls to be made to mobiles over dissimilar networks.

Home Location Register (HLR)

This HLR database includes the information regarding the administrative like every subscriber with their previous identified location. Like this, the GSM network is capable to connect the calls to the related base station for the mobile switch. Once an operator turns ON his/her phone, and then the phone registers through the network so that it is probable to decide which base transceiver station is communicating so that incoming calls can be connected properly.

Even once the mobile is switched on, but not active then it again registers to make sure that the HLR network is responsive to its most recent location. There is one HLR for each network, even though it may be dispersed across a variety of sub-centers for operational causes.

Visitor Location Register (VLR)

The VLR includes preferred information that is received from the HLR network to allow the preferred services for the separate subscriber. The visitor location register can be executed like a separate unit; however, it is usually realized like an essential element of the MSC, before an individual unit. Thus, access is finished quicker & more convenient.

Equipment Identity Register (EIR)

The EIR (Equipment Identity Register) is the unit that makes a decision whether specified mobile gear may be permitted over the network. Every mobile gear includes a number identified like the IMEI or International Mobile Equipment Identity.

So, this IMEI number is fixed within the mobile equipment & is verified through the network while registration. It mainly depends on the information that is held within the EIR, and the mobile device may be assigned one of 3 conditions which allowed over the network, barred access, otherwise watched in case its problems.

Authentication Centre (AuC)

The AuC (authentication center) is a protected file that includes the secret key in the SIM card of the user. The AuC is mainly used for verification & for coding on the radio channel.

Gateway Mobile Switching Centre (GMSC)

The GMSC/ Gateway Mobile Switching Centre is the end to which a ME finishing call is primarily connected without any information about the MS’s place. The GMSC obtains the Mobile Station Roaming Number (MSRN) from the MSISDN based on HLR & connecting the call toward the exact visited MSC. The “MSC” division of the name GMSC is confusing as the gateway process does not need any linking toward an MSC.

SMS Gateway (SMS-G)

The SMS gateway or SMS-G is used jointly to explain two SMS-Gateways in the GSM standards. These gateways control messages which are directed in dissimilar ways.

The Short Message Service Gateway Mobile Switching Centre (SMS-GMSC) is used for short messages which are being transmitted to an ME. The Short Message Service Inter-Working Mobile Switching Centre (SMS-IWMSC) is used for short messages created through a mobile network. The main role of SMS-GMSC is related to GMSC, but the SMS-IWMSC offers a permanent access end to the SMS Centre.

These units were the major ones that are used in the network of GSM technology. They were normally co-located, however frequently the overall middle network was transmitted around the country wherever the network was situated. In case of malfunction, it will give some flexibility.

Base Station Subsystem (BSS)

It acts as an interface between the mobile station and the network subsystem. It consists of the Base Transceiver Station which contains the radio transceivers and handles the protocols for communication with mobiles. It also consists of the Base Station Controller which controls the Base Transceiver station and acts as an interface between the mobile station and mobile switching center.

The network subsystem provides the basic network connection to the mobile stations. The basic part of the Network Subsystem is the Mobile Service Switching Centre which provides access to different networks like ISDN, PSTN, etc. It also consists of the Home Location Register and the Visitor Location Register which provides the call routing and roaming capabilities of GSM.

It also contains the Equipment Identity Register which maintains an account of all the mobile equipment wherein each mobile is identified by its own IMEI number. IMEI stands for International Mobile Equipment Identity.

The BSS or Base Station Subsystem section of the second generation GSM network architecture is basically connected with the mobiles over the network. This subsystem includes two elements which are discussed below.

Base Transceiver Station (BTS)

The BTS (Base Transceiver Station) which is utilized within a GSM network includes the radio Tx, Rx & their related antennas to transmit, receive & directly converse through the mobiles. This station is the important element for every cell and it converses with the mobiles & the interface among the two is identified like the Um interface with related protocols.

Base Station Controller (BSC)

The BSC (base station controller) is used to form the next phase reverse into the GSM technology. This controller is used to control a collection of base transceiver stations & it is frequently co-located through one of the transceiver stations within the group. This controller manages the resources of radio to control different items like handover in the collection of BTSs, assigns channels. It converses with the Base Transceiver Stations over Abis interface.

The subsystem element in the base station of the GSM network uses the radio allowable technology to allow a number of operators to right to use the system concurrently. Every channel supports up to 8 operators by allowing a base station to include different channels; a huge number of operators could be accommodated through every base station.

These are located carefully through the provider of the network to allow whole area coverage. This area can be enclosed with a base station that is often being called a cell. Because it is not achievable to stop the signals from overlapping into the nearby cells and channels which are used in single-cell are not utilized in the next.

Mobile Station

It is the mobile phone which consists of the transceiver, the display, and the processor and is controlled by a SIM card operating over the network.

The MS (Mobile stations) or ME (mobile equipment) are most generally identified through cell otherwise mobile phones which are the part of a GSM mobile communications n/w that the operator observes & operates. At present, their dimension has reduced radically whereas the functionality level has very much increased. And one more benefit is that the time among charges has drastically enlarged. There are different elements to the mobile phone, though the two essential elements are the hardware & the SIM.

The hardware includes the major elements of the mobile phone like the case, display, battery, & the electronics utilized to produce the signal & process the data receiver to be broadcasted.
The mobile station includes a number called the IMEI. This can be set up on the mobile phone while manufacturing & it cannot be modified.

It is accessed by the network during registration to check whether the equipment has been reported as stolen.

The SIM (Subscriber Identity Module) card includes the data which gives the user identity toward the network. And also, it includes different information like a number called the IMSI (International Mobile Subscriber Identity). When this IMSI is used in the SIM card, the mobile user could simply change mobiles by moving the SIM from one mobile to another.

So mobile changing is easy without changing the same mobile number means that people would frequently improve, thus making a further income stream for the providers of network & serving to enhance the total financial victory of GSM.

Operation and Support Subsystem (OSS)

The operation support subsystem (OSS) is a part of the complete GSM network architecture. This is connected to the NSS & the BSC components. This OSS is mainly used to control the GSM network & the BSS traffic load. It should be noted down that when the number of BS enhances through the subscriber population scaling then some of the preservation tasks are moved to the base transceiver stations so that the ownership cost of the system can be reduced.

The GSM network architecture of 2G mainly follows a logical technique of operation. This is very simple as compared with present architectures of mobile phone network which utilize software-defined units to allow extremely supple operation. But the architecture of 2G GSM will demonstrate the voice & operational fundamental functions that are required & how they arranged together. When the GSM system is digital, then the network is a data network.

Features of GSM Module

The features of the GSM module include the following.

• Improved spectrum efficiency
• International roaming
• Compatibility with integrated services digital network (ISDN)
• Support for new services.
• SIM phonebook management
• Fixed dialing number (FDN)
• Real-time clock with alarm management
• High-quality speech
• Uses encryption to make phone calls more secure
• Short message service (SMS)

The security strategies standardized for the GSM system make it the most secure telecommunications standard currently accessible. Although the confidentiality of a call and secrecy of the GSM subscriber is just ensured on the radio channel, this is a major step in achieving end-to-end security.

GSM Modem

A GSM modem is a device that can be either a mobile phone or a modem device that can be used to make a computer or any other processor communicate over a network. A GSM modem requires a SIM card to be operated and operates over a network range subscribed by the network operator.  It can be connected to a computer through serial, USB, or Bluetooth connection.

A GSM modem can also be a standard GSM mobile phone with the appropriate cable and software driver to connect to a serial port or USB port on your computer. GSM modem is usually preferable to a GSM mobile phone. The GSM modem has a wide range of applications in transaction terminals, supply chain management, security applications, weather stations, and GPRS mode remote data logging.

Working of GSM Module

From the below circuit, a GSM modem duly interfaced to the MC through the level shifter IC Max232. The SIM card mounted GSM modem upon receiving digit command by SMS from any cell phone sends that data to the MC through serial communication. While the program is executed, the GSM modem receives the command ‘STOP’ to develop an output at the MC, the contact point of which are used to disable the ignition switch.

The command so sent by the user is based on an intimation received by him through the GSM modem ‘ALERT’ a programmed message only if the input is driven low. The complete operation is displayed over a 16×2 LCD display.

GSM Technology Applications

The applications of GSM technology include the following.

Intelligent GSM Technology for Automation and Security

These days, the GSM mobile terminal has become one of the items that are constantly with us. Just like our wallet/purse, keys or watch, the GSM mobile terminal provides us a communication channel that enables us to communicate with the world. The requirement for a person to be reachable or to call anyone at any time is very appealing.

This project, as the name says the project is based on GSM network technology for transmission of SMS from sender to receiver. SMS sending and receiving is used for ubiquitous access to appliances and allowing breach control at home. The system proposes two sub-systems. The appliance control subsystem enables the user to control home appliances remotely and the security alert subsystem gives automatic security monitoring.

The system is capable enough to instruct users via SMS from a specific cell number to change the condition of the home appliance according to the user’s needs and requirements. The second aspect is that of security alert which is achieved in a way that on the detection of intrusion, the system allows automatic generation of SMS thus alerting the user against security risk.

GSM technology will allow communication anywhere, anytime, and with anyone. The functional architecture of GSM employing intelligent networking principles, and its ideology, which provides the development of GSM is the first step towards a true personal communication system that enough standardization to ensure compatibility.

GSM Applications in Medical Services

Consider Two Situations like the following

• A person is critically injured or has fallen ill and needs to be immediately taken care of. All he or the person accompanying him has is a mobile phone.
• A patient is discharged from the hospital and thinks of taking rest at his home, but still has to go to the hospital for regular checkups. He may have a mobile phone and also some medical sensor devices like health monitoring devices.

In both situations, the only way which can provide a solution is by using the mobile communication system. In other words, using communication technologies any situation like the above can be handled just by transmitting the patient details through the communication network and receiving them and processing them at the receiver section-either a the healthcare center or at the doctor’s home.

The doctor simply monitors the patient details and gives back the instructions to the person(in the 1^st case)so that he can at least take some precautions before finally reaching the hospital and in the 2^nd case monitors the test results of the patient and in case of any abnormalities, takes the next step for further treatment.

This whole situation is the telemedicine services. The telemedicine system can be used in either of the three ways.

• Using Video conferencing, where patients sitting at one place can have direct interaction with the health care providers and accordingly carry on the curing process.
• By using health monitoring sensors that keep updating about the health of the patient and accordingly guide the health care providers to carry on the treatment.
• By transmitting the acquired medical data and transmit the acquired data for consultation and processing.

For the above three ways, a wireless communication technique is used.  Medical services require many ways of getting access to stored resources. These can be medical databases or online hosts with devices that can help recover and monitor patient health. Different access options are broadband network, through medium-throughput media and narrowband through GSM.

The advantages of GSM technology in the telemedicine system include the following.

• It is more cost-effective.
• GSM receivers are widely available- mobile phones and GSM modems
• It has a high data transfer speed.

Basic Telemedicine System

A basic telemedicine System consists of 4 modules:

• The Patient Unit: It collects information from the patient, sends it as an analog signal or converts it to the digital signal, controls the data flow, and transmits the data. It basically consists of various medical sensors like heartbeat sensor, blood pressure monitor, skin temperature monitor, spirometry sensor, etc which outputs an electrical signal and sends these signals to the processor or a controller ( a Microcontroller or a PC) for further processing of the signals and then transmits the results through a wireless communication network.
• Communication Network: It is used for data security and data transmission. The GSM technology is used which uses mobile stations, base substations, and network systems. The mobile station consists of the basic mobile access point or the mobile phone and links the mobile phones with the GSM network for communication.
• Receiver Unit/Server Side: It is basically a healthcare system where a GSM modem is installed which receives and decodes the signals and sends them to the presentation unit.
• Presentation Unit: It is basically the processor that converts the data received into a well-defined format and stores them so that the doctors can regularly monitor it and any feedback to the client-side can be sent via SMS from the GSM modem.

A Simple Telemedicine System

A Basic Telemedicine system can be shown in a simplified way. It consists of two units – The transmitter unit and the receiver unit. The transmitter unit transmits the sensor input and the receiver unit receives this input to carry on further processing.

Given below is an example of a simple telemedicine system to monitor the heart rate of the patient and accordingly process the data.

At the transmitter unit, the heartbeat sensor (which consists of a light-emitting source whose emitted light is modulated as it passes through human blood) converts the obtained data from the human body and converts them to electrical pulses. The microcontroller receives these pulses and processes them to calculate the heartbeat rate and sends this calculated data to the health care unit through a GSM modem. The GSM modem is interfaced with the Microcontroller using a Max 232 IC.

At the receiving unit, the GSM modem receives the data and feeds it to the Microcontroller. The Microcontroller accordingly analyzes the received data with the data from the PC and shows the result on the LCD. The patient monitoring can be done based on the result displayed on the display by the medical staff so that the required treatment procedure can be started.

Practical Examples of GSM Technology in Medical

In practice, GSM technology is used in the following fields.

AT&T Vitality GlowCaps

These are pills bottles that simply gives a reminder to a patient to take his/her medicines. It consists of a timer that is set for the patient’s pill-taking time and at that time sets the cap to illuminate and starts the buzzer and then calls the patient’s mobile phone using the GSM technology. A record is made for every opening of the bottle.

Mobisante Mobius SP1 Ultrasound System

It consists of a mobile ultrasound probe plugged into a smartphone and transmits the handheld ultrasound imaging to any remote place through GSM.

Dexcom Seven Plus Continuous Glucose Monitoring (CGM) System

This is used for monitoring the blood glucose levels of the patients and transmitting them to the doctor. It consists of a sensor placed beneath the skin which continuously monitors the blood glucose levels and transmits them to the receiver( a cell phone) at frequent intervals.

Future Scope of GSM in Medical Services

In accordance with a recent survey by PricewaterhouseCoopers for the GSM Association, an industry body that represents nearly 800 of the world’s mobile operators in 219 countries, GSM-enabled services will become a part of the healthcare system by 2017, creating a global market of 23 billion dollars.

Now among all these, GSM technology is the most widely used option owing to its immense popularity, improved spectrum efficiency, and low cost of implementation.