What is GSM Technology and How to Use GSM for IoT?

Table of Contents Show

GSM is short for Global System for Mobile Communications.

It is the European Telecommunication Standards Organization. Time division multiple access technologies are applied to its air interface. It has been applied to more than 100 countries since its commercial launch in the mid-1990s. The purpose of this article is to bring you a further understanding of GSM technology in the field of IoT applications.

1. What is GSM Wireless Technology?

What is GSM Technology

What is GSM in IoT?

1. GSM is a digital Mobile phone network standard developed by Europe. GSM uses digital modulation technology, one of its key technologies is TDMA Time Division Multiple Access (TDMA) (each user occupies frequency in a certain time slot and can only receive information at a certain time).  

GSM system has multiple frequency bands, including GSM 900:900mhz, GSM-1900, 1900MHz, GSM1800:1800mhz, and others.

The popularity of the GSM standard has made international roaming common after “roaming agreements” are signed between mobile-phone operators. The reason that GSM is viewed as the second generation of mobile phone systems for the biggest improvement of GSM compared to its predecessors is that its signaling and voice channels are digital. 

Technical characteristics of GSM  

1. Open interfaces  

The GMS system not only has an air interface but also contains network and device entities in the network, for example, the Abis interface.

2. Security  

The security of GSM is protected through encryption, user authentication, and the use of TMSI numbers. Authentication refers to verifying users’ access permission. Controlled by the key of network AUC and the SIM card, encryption is the one that is used for the air interface. TMSI, as a temporary identification number assigned to a user by a business network, helps to prevent someone from tracking or revealing the user’s location.

2. Working principle of GSM IoT

Working principle of GSM IoT

GSM is short for Global System for Mobile Communications, the widely used mobile phone standard is one of the world’s most important cellular systems.  CDMA is the mainstream 2G communication system, today xiaobian with you to understand the principle of GSM is how.  

GSM principle – Introduction  

GSM is different from previous standards since it has unique voice channels and digital signaling, which is the reason GSM is considered a 2G mobile phone system.  

GSM principle – Features  

Spectral efficiency: The system has high spectral efficiency for the use of a high-efficiency modulator, channel coding, equalization, interleaving, and speech coding.  

Capacity: The increase of the transmission bandwidth of each channel, has contributed to the same frequency multiplexing ratio requirement reduced to 9dB.

Due to this, the GMS same frequency multiplexing pattern has been brought down to 3/9or 1/4 and even smaller. For your reference, the data for the analog system is 7/21; At the same time, the bring-in of half-rate voice coding and the effort to reduce the number of out-of-zone switching by automatic traffic allocation, the capacity efficiency (number of channels per megahertz per cell) of the GSM system is about three to five-fold higher than the efficiency of TACS system

Voice quality: No matter how is the wireless transmission quality, thanks to the advantages of digital transmission technology, the air interface, and voice coding in the GSM standard, the voice quality will always reach above the standard threshold.

Open interfaces: The GMS system not only has an air interface but also contains network and device entities in the network, for example, the Abis interface  

Security: The security of GSM is protected through encryption, user authentication, and the use of TMSI numbers. Authentication refers to verifying users’ access permission. Controlled by the key of network AUC and the SIM card, encryption is the one that is used for the air interface.

Interconnection with other networks like the ISDN and PSTN, normally utilize existing interfaces, for example, ISUP or TUP.

The roaming function depends on the SIM card.  As everybody knows, roaming is an important factor in mobile communication services.  

GSM principle – Basic principle  

The core technology of the GSM air interface is TDMA. Technical characteristics: frequency division duplex, each carrier frequency 200KHZ(up and down asymmetric);  TDM, 8 TDM channels per carrier frequency;  Slow FM, counter interference.  

Signal coverage uses large area deployment base stations, a site is generally divided into three sectors, and multiple sites can form a cell group.  Cells can be replicated continuously to achieve large area coverage.  

The access network is also called the base station subsystem (BSS) and the core network is also called the Switching network subsystem (MSS)  

Um, is the interface between MS and BSS, while A is the one between BSS and MSS.  

Network Switching Subsystem (NSS), Base Station Subsystem (BSS), and  Network Management Subsystem (Network Management Subsystem) are three subsystems of the GMS system. Among these, Network Management Subsystem (NMS) is also called Operation and Maintenance Center (OMC–Operation & Maintenance Center).  

Network subsystem NSS is the core of the GSM system. It has the function of switching connection and administration between GSM mobile users and between mobile users and other communication network users. The Base station subsystem is connected to the mobile station through a wireless interface, it is responsible for wireless resource management, sending and receiving information, power control, and so on. It has the most direct relation with a wireless cellular component through the wireless interface directly connected to the mobile station at the same time it is connected with NSS realize mobile users or mobile communication among the users with fixed network connection, transmit system information and user information, etc. The NMS is in charge of the maintenance and management of the NSS and BSS systems.  

GSM principle – security  

GSM has a medium level of security. The system adopts sharing key and user authentication, which contributes to the communications between the base station and the user can be encrypted.

USIM is a further evolution of UMTS, which has a better performance by using longer authentication keys for better security and there is two-way authentication between the network and the user. GSM only has the network-to-user authentication feature. Even though the security system has security and authentication features, its capability is quite limited and can be fabricated.  

GSM uses a variety of encryption algorithms for security. Adopted in Europe, A5/1 is a mighty algorithm, while A5/2 is a relatively weak algorithm used outside of  Europe. They are both streaming ciphers adopted to confirm the secrecy of the air conversation. Severe flaws have been found in both algorithms. 

3 .GSM network structure 

GSM network structure

Mobile station  

The mobile station is the most primitive mobile network:  

The basic function  

· Been accessed to the GSM system, with wireless transmission and processing capabilities 

· The man-machine interface is also provided (such as MIC, loudspeaker, display screen, and various buttons)  


· Mobile terminals  

· Subscriber Identity Module (SIM)  

Mobile Terminal (” Machine “)  

· Voice coding, channel coding, information encryption, modulation, and demodulation, transmitting and receiving  

SIM card (” IDENTITY Card “)  

· The SIM card is one that contains all the information required for the authentication of the user’s identity, it can perform some important operations concerned with security and safety. So it can forbid illegal users to access the net. At the same time, the SIM card helps to store management data concerned with the network and users but only after inserting into the network.

Base Station Subsystem (BSS)  

Measures to Enhance System Management Capability – Introduction of Master Steward Mobile Switching Centre (MSC)  

The base station transceiver (BTS) and base station controller (BSC) is called the base station subsystem (BSS).  

Base Station Controller (BSC)  

In charge of multiple functions such as WLAN network resource administration, switching and control of the power, data management, and so on, the BSC controls one or more BTSs.      

Base station Transceiver (BTS)  

Wireless interface device, completely controlled by BSC, responsible for wireless transmission function.  

Network subsystem  

Introduction to the major features of a mobile switching center: 

· Firstly, The primary task of this center is to achieve the voice connection switching function, including the switch between mobile users and mobile users, mobile users and fixed users  

· Support the registration and update of the location

· User identification    

· Cooperate with base station controller to realize Interregional switch and roaming service  

· Network maintenance and billing function, etc  

Mobile Switching Center assistant – Location register  

Introduction of the information that is reserved in the home location register:  

The operator will store the user information in the HLR Visitor location register when the user applies for a new card.

Access position register  

· Given the users can easily extract information when roaming, once they roam to other cities, the VLR of the roaming place will automatically copy the user information from HLR, in this case, users can continue to enjoy the service provided by the operator.  

Introduction of the information that will be stored in the access location register.

Mobile Switching Center Assistant – Operation and Maintenance center  

Operation and Maintenance Center (OMC): Monitors and maintains the entire network, such as fault diagnosis and handling, traffic statistics, and charging.

Mobile switching center assistant – authentication center  

Authentication center (AUC): Used to perform encrypt calls, security management, and identify users.

  VLR works as a temporary backup of HLR  

GSM system number and identification  

International ISDN Number for Mobile Stations (MSISDN)  

Call a mobile number to be dialed  

CC: Country code, for an international call, 86 for China  

NDC: indicates the domestic destination code, that is, the first three digits of the mobile phone number  

SN: user number. The first four figures are applied to identify the home place. When a call is made, the HLR where the user resides can be found and user information can be obtained.  

International User Identity (IMSI)  

Consisting of SIM cards, HLR and VLR, IMSI is used in a communication device to identify users, It is special for its unique identification of mobile users among the domestic GSM mobile communications network.  

Temporary Mobile Subscriber Identity (TMSI):  Temporary Mobile Subscriber Identity (TMSI): For purpose of protecting IMSI secrecy, MSC/VLR will allocate a unique TMSI number to mobile customers. Assigned by the MSC system and as a 4-byte BCD code, the number can only be used within the MSC business area.

· The IMSI can only be transmitted over the air for one available time to confirm confidentiality. At the same time, there is a unique TMSI assigned to visiting mobile users by VRL

· The number is only valid only locally and it is not a one-time used number since it will be released when the user leaves the VLR service area.

· These numbers will be reused and temporary allocated by VLR

Mobile Station Roaming Number (MSRN)  

The structure is the same as MSISDN and is temporarily assigned by the MSC/VLR where the user is roaming.  This parameter is used to select routes for mobile users during a call.  

The MSISDN points to its HLR, and it is not possible to establish a connection between the calling party and the MSC where the called party is registered to make a call.  

Wireless transmission features of the GSM system.  

(2) Duplex mode  


(1) Working frequency band  

Uplink: 890-915mhz

Downlink: 935-960mhz

(3) Channel division  

Channel interval: 200kHz  

The total number of valid channels is 124  

The frequency interval between each pair of channels is 45MHz  

(4) Access mode  


(5) Modulation mode  

Gaussian Minimum Frequency Shift Keying (GMSK)  

4. GSM and CDMA


Differences between GSM and CDMA  

Signal encoding is different  

Cdma is code division multiple access.  GSM combines frequency division multiple access with time division multiple access.  

GSM network standards are different  

GSM network system generally has three network frequencies of 800/900/1800/1900mhz, which is 2G technology. Mobile phones that support GSM networks all support GPRS(General packet wireless service), which belongs to the 2.5-generation GSM, and now black is another kind of EDGE. It is a transitional stage of the third-generation GSM network (also known as 2.75GSM). The 3G technology of the GSM network is the WCDMA network, which is one of the future development directions of GSM.  

CDMA networks are divided into three types (CDMA2000/WCDMA/TD-SCDMA), among which China Unicom’s CDMA network belongs to CDMA2000, which is the CDMA network standard of Qualcomm in the United States, and is divided into CDMA2000 1x/ 2X / 3X;  China Unicom’s approach is different from that of Japan, where one phone number is bound to one phone number and one phone must be changed when changing the phone number. In China, it is “machine-card separation “(users can change the number at will without necessarily changing the phone number). Of course, the United States has to pay patent fees to Qualcomm every year.  

The main users of WCDMA networks are Hutchison Whampoa in Hong Kong, China, and it appears that South Korea also uses the same network.  

The last TD-SCDMA is a 3GSM network developed in collaboration with Siemens of Germany, and China has its intellectual property rights.  

China’s 3G GSM network development direction in two: one is to develop WCDMA, one is TD-SCDMA, depending on the decision of the national government, of course, the most likely to develop 3G GSM network is China Mobile, because China Unicom already has CDMA2000 1X 3G network.  

Different transmission distances  

GSM requires more base stations compared to the CDMA system base on the same distance. For example, covering a 1000KM distance, CDMA requires only 45 base stations while GSM requires 100 stations. 

The base stations of CDMA are 80% fewer than GSM, and at the same time,  each CDMA sector is small in size, and only takes up 55% of its maximum capacity. The increase of actual traffic channels will cause the shrink of the GSM cell radius. 

The number of actual traffic channels per square KM is up to 20, and each base station can cover a distance of 20KM.

In addition, If the GSM base stations are not able to provide acceptable voices if their time slot is greater than 14 voices.  


Efficient use of spectrum over the air interface is very important since it is not only limited but also very expensive. An efficient use means it can support a large number of users in the same bandwidth, which can increase potential revenue and reduce the cost at the same time. The CDMA has a high capacity and its spectrum utilization rate is more than 10 times AMPS.

CDMA can offer up to 25 talk/sector /CDMA channels in a high-speed mobile state, which already includes a 35% soft switching overhead. The transmission rate and spectrum receiving rate of each CDMA channel is 1.25MHz. 

CDMA, GSM, and AMPS capacities can be obtained from the comparison of the spectrum occupied by 10MHz and 30MHz. GSM or AMPS has no protective tape, which is the most optimistic case for them, as shown in Table 3 and Table 4.  

Table 3 The situation of the 10MHz spectrum (5MHz transmission, 5MHz reception)  

The price  

Many factors must be considered when determining the cost of implementing a wireless system. Construction of base station controllers, network planning and installation,  maintenance, and management and so are all the initial costs.

 A successful business should plan for its growth so that as it expands to more users, it will generate more income than the cost of investment.  However, using an unreasonable capacity technology, the system operation will add more base stations to expand the number of users, and cost more.  

The expenditure sometimes also depends on “time to market”.The system booting and running and some other factors all influence the time to market.  The “get to market” time will take longer if more base stations and network planning are required.

As mentioned above, CDMA requires only 20% base stations compared with GSM. This feature helps to reduce fixed assets, equipment investment, site construction, spectrum, and maintenance costs. In addition, because GSM claims 3/9 frequency multiplexing, any base station cell or sector that exceeds initial planning requires complex and costly reconfiguration of the network.  CDMA can easily add cells and sectors without having any impact on the existing network planning since its frequency reuse factor is 1. This is very convenient for network planning. 

Compared with PCS occupying 30MHz spectrum, PCS using only 10MHz spectrum can save a considerable amount of cost, because 10MHz CDMA can provide 70% more call volume than 30MHz GSM. Service providers can not only save the cost of purchasing PCS in the initial stage but also provide better services for more users.  

PCS operations must clear its spectrum of existing microwave users.  If the CDMA mobile phone is far away from the base station, its transmission rate will be very small. So they also have little distraction to microwave fixed stations compared with GSM. Moreover, because of CDMA’s inherent spread-spectrum technology, operators need to clear very little spectrum to provide sufficient capacity. The integration of these factors has facilitated significant cost reductions for PCS operators.  

CDMA phones are adapted to suit a variety of markets. These phones are reaching economical prices worldwide in a wide range of wireless local loop, PCS, and cellular markets, where phones share critical circuit components, thus making them more efficient and competitive. There are dozens of mobile phone companies that have got permission from CDMA so the competition is intense Above all, we can see that there is a low cost of CDMA network foundation and operation.

Articulation of speech  

The articulation of speech is affected by the spatial propagation characteristics of air interface technology and the design of the sound coder. The CDMA has excellent air propagation performance due to its good features.  

Rayleigh fading and shadow multipath effects exist in all wireless mobile applications.  CDMA takes advantage of multipath environments through spectrum expansion processing (off-multipath receiver), time diversity (symbol interweaving and error detection and error-correcting coding for all transmitted bits), and multi-cell/sector diversity (soft and soft switching).  

GSM uses a TDMA system, so bandwidth is limited. In particular, GSM is worse than CDMA in forwarding error-correcting coding ability. CDMA has a powerful forward error correction function, which is very meaningful since it can significantly improve the clarity during the call, especially in a noisy and complicated transmission environment, or with large co-channel interference caused by system overload.  

The multipath receivers are greatly used in the CDMA system, for example, there will be three of them used in the mobile station receiver and four of them will be used in each antenna in the base station. What they do are tracking the signal and multipath separately, and the sum of their signal strengths is used for signal demodulation. Between soft switch (cell) and soft switching (between sectors of the same cell) provides completely transparent switch calls, CDMA uses a soft switch of “broken after the first pass”, as a result, even at the edge of the CDMA cell, language and data switch quality also is greatly improved, so the user calls possibility to eliminate effectively, See Figure 2. CDMA uses the power control of forward and reverses links to achieve better speech clarity. The power control of the reverse link can be adjusted in two ways: closed loop and open loop. These power controls are sensitive to cellular load, cellular noise maps, antenna gain, amplifier output, multipath fading, shading, and changes in the distance between the mobile station and the base station receiver. The benefit is it only costs minimal average output power to have consistently high-quality voice and digital services. The very low average transmitting power translates directly into long talk time and backup time. Qualcomm Electronics inc. (Qualcomm/Sony) will offer customers up to 300 minutes of talk time, three days of backup time, and eight ounces (225 grams) of CDMA cellular and PCS phones. 

Under compression conditions, this brand-new CDMA vocoder algorithm still can offer a clear speech. Developed in 1988, GSM’s vocoder is designed to operate at a fixed rate of 13kbit/s, an algorithm that often provides only “acceptable” speech.  

The improvement of the CDMA space performance benefited from the advanced CDMA vocoder algorithm.  A variable rate vocoder with a peak value of 8kbit/s is designed for cellular applications and a variable rate vocoder with a peak value of 13kbit/s is designed for PCS.  However, we should pay attention that the normal rate of the vocoder is less than its peak rate. Unlike some TDMA vocoders, which use digital voice interpolation, CDMA vocoders typically transmit at least 1200bit/s.  This makes voice quality sound more natural to the user and also makes CDMA clear. The employ of adaptive thresholds that determine the rate of the vocoder. Adaptive thresholds change the data rate of the vocoder according to changes in the background acoustic noise level. These thresholds suppress background acoustic noise and thus provide clear speech even in noisy environments.  


Selectivity provides wireless operators with the flexibility to serve today’s and tomorrow’s customers. CDMA will provide operators with four different highest-rate vocoders (13,8,6.5, 4kbit/s).  With this flexibility, users can choose voice services in different environments (automotive, business, and advanced voice services) as needed.  Or in high-density urban environments, operators can provide instant “instruction bandwidth” by selecting peak-data-rate processing modules, depending on the required capacity. CDMA also offers a selection of services: high-quality voice, packet data, asynchronous data, G3 fax, and short messaging.  CDMA can provide voice and data services at the same time, so users can receive pager messages while talking. Not only the initial data rate provided by the 1.25MHz CDMA spread spectrum signal but a new enhanced CDMA air interface has been proposed as the standard for high-speed data applications. The enhanced CDMA will use a 2.5mhz CDMA spread spectrum signal and provide operators with data services of up to 76.8kbit/s.  This high-speed service can provide all-mobile video phones, digital photos, giant file transfers, and high-capacity Email, and operators can share a lot of base station equipment as they move from 1.25MHz CDMA to enhanced CDMA.  

Customer satisfaction  

Effective wireless services ultimately depend on customer satisfaction.  In voice tests conducted simultaneously with other air interfaces, CDMA was found by the vast majority of users to be of good voice quality. Using CDMA phones with similar voice quality as wired phones make using wireless phones a joy. This is particularly important because the primary means of communication for high telephone utilization users are wireless. As the number of data services (fax, E-mail) increases, users will become increasingly intolerant of error codes. To prevent the occurrence of error codes, CDMA uses strong error correction, soft switching, and separation of multipath diversity receiver, which means that CDMA can provide GSM that can not match very high data quality. Due to its large coverage and high capacity, CDMA enables operators to provide wireless services at an economical price, thus improving user satisfaction with high-quality and efficient services. The combination of low average power, high-efficiency vlSIIC design, and advanced lithium battery show CDMA breakthrough in portable phone applications. Weighing just 8 ounces (225 grams), the CDMA handset will provide more than 3 days of backup time and more than 4 hours of talk time. Because of its longevity, the user can use his phone for a long time to receive more calls, and the user can receive short messages without hanging up.

5. Comparison between GSM and GPRS technology

GSM represents for Global System for Mobile Communications  

GPRS stands for General Packet Radio Service  

Based on the GMS system, the GPRS system is a packet data bearer and transmission tool.

GSM works as a circuit switching system, while GPRS serves as a packet switching system, which is the most essential difference between these two systems.

GSM can only transmit data via SMS, but cannot achieve by the ways of “instant online” and “billing by volume”. GPRS has a distinct advantage of bearing and supporting the data compared with GSM. This is manifested in the following aspects: firstly, it has higher efficiency when using the wireless network channel resources, secondly, it is suitable for multiple data transmission, especially suitable for both small and large amounts of data transmission, transmission intermittent, non-periodic data transmission, etc.  

The technical strengths of GPRS can also be seen in the following aspects: High resource using rate; High transmission rate; Always online; Short access time; Supports IP and X.25 protocols;  Reasonable charges, etc.  

The advantages of GPRS  

GPRS is a packet-switching technology, which has the advantages of “high speed” and “always online”.  

Real-time online  

“Live online” or “Real-time online” refers to the users who are connected to the network and stay online all the time. For example, a user gets to the Internet, at the same time his or her mobile phone sends and receives data through the wireless channel. The mobile phone will still keep connecting with the network no matter whether there is data transmission or not. 

Volume Pricing  

In a circuit-switched GSM system, the wireless channel is owned by the user, regardless of whether data is transmitted or not, during the entire connection period. For packet-switched GPRS, the user occupies resources only during the sending or receiving of data. This means the efficiency can be greatly improved since multiple users can share the same wireless channel at the same time, which improves resource utilization. The billing rules of GPRS follow the principle of “what you get, what you pay”. According to the technical features of packet switching, the billing is based on the cost of the user’s data traffic. To sum up, even though the user stays online, if there is no data traffic during this time, users will not be charged.

Quick Login  

As soon as the GPRS mobile phone turns on, it can be connected to the GPRS network, and the attachment time normally only cost 3-5 seconds.  An activation process is required each time the GPRS data service is used by the user. And this activation time normally will take 1-3 seconds.

Once the GPRS data service is activated, the internet will be completely connected. The fixed dial-up mode will take at least 8-10 seconds to dial, after verifying the user name and password, it will log in to the server.

The high-speed transmission  

By adopting the packet switching technology during the high-speed transmission GPRS process, theoretically, the highest data transmission rate can reach 171.2 kbit/s, at this time has been fully able to support multimedia image transmission business such as some of the high bandwidth requirements of the application business. But the theoretical value of 171.2 kbit/s is realized under the condition of cS-4 encoding in and good wireless environment and sufficient channel. The actual data transmission rate determines by the network terminal support, coding mode, wireless environment, and many other factors. Nowadays, the connection speed of GPRS users is less than 40kbit/s. The connection speed can be increased from 60kbit/s to 80kbit/s with the data acceleration system.

6. Excellence of GSM IoT

Excellence of GSM IoT

GSM advantages  

One of the biggest advantages of the GSM standard is that it has an open interface, not just in the air, but also in networks and network equipment entities. Secondly, GSM has strong security, it has been through authentication and encryption and other ways to ensure the security of GSM numbers so that it can have a very safe effect. Finally, it can roam on top of a SIM card, allowing users to switch between different networks.  

Mobile communication folding  

GSM is the 2G cellular mobile communication form. Generation 2 refers to the analog cellular mobile communication technology used in the 1980s and the broadband CDMA technology that is gradually entering commercial use. Analog cellular technology and broadband CDMA technology stand for different generations. Analog represents the first generation, while the other is the third generation mobile communication technology, also called 3G.  

Radio interface folding  

GSM is a cellular network, meaning that a mobile phone connects to the area of the nearest cell it can search.  GSM networks operate on many different radio frequencies.  

Microcell, giant cell, umbrella cell, and pico cell are four different cell sizes for GSM networks. The area covered varies with different environments. Commonly used in urban areas, the antennas of Microcells are generally lower than the average building height. Since they are tiny cells that cover only a few dozen meters, they are normally used indoors only. Giant cells can be thought of as base-station antennas mounted on masts or on top of buildings. Umbrella cells are also important gaps, normally used to fill in the signal gaps between different cells.

Cellular radius is determined by antenna height, propagation conditions, and gain,  ranging from 100 plus meters to even tens of kilometers. The actual maximum distance in use is up to 35 km according to the GSM specification. The cells can also be doubled or more times extended. Indoor coverage is also possible by using the power distributor, which can distribute the outdoor antenna power to the indoor antenna. 

Indoor high-density calling is common in the places like airports and shopping malls.  But the truth is, it is not a necessity as the wireless signals through the building can achieve indoor coverage, but this calling is also meaningful since it reduces echo and improves signal quality. 

GSM shortcomings  

Users send a short message is first sent to the center of the short message server, and then the SMS center server to receive short message queue processing, to send to the corresponding receiving user terminal, if the receiving user shutdown or exceeds the service area can’t normal communication, the text message sent later may arrive faster or first after a certain time delay like this situation.  

Moreover, each user has a limited cache provided by the short message center server, that is, 15 to 25 messages for each one. The server will not receive any new text messages once the receiving memory is full and the receiving user also cannot communicate normally. This means, that text message block up occurs, causing short message loss.  

Short messages can also be retained for about a day in the SHORT message center. The network and receiver must be in a stable communication status to confirm the data switch between the central manager and the monitoring station.  

The SMS received by the GSM module of a GSM mobile phone is stored in a SIM card. A common SIM card can store 25 SMS messages. Therefore, the SMS should be stored in the SIM card 

7. What is GSM used for, Can we use GSM in IoT?

What is GSM used for

What is a GSM module?  

GSM module is multiple functional modules that integrate a baseband processing chip, GSM RADIO frequency chip, power amplifier device, memory, etc on a circuit board. It has an independent GSM radio frequency processing, operating system, and baseband processing system, providing a standard interface.  

GSM module shares all the basic functions like voice calls, sending SMS messages, GPRS data transmission, and other communications with the GSM network. Simply put, the GSM module, plus the keyboard, display screen, and battery, is a mobile phone.  

Working principle of the GSM module  

GSM is a cellular network, meaning that a mobile phone connects to the area of the nearest cell it can search. GSM networks operate on many different radio frequencies.  

Microcell, giant cell, umbrella cell, and pico cell are four different cell sizes for GSM networks. The area covered varies with different environments. Giant cells can be thought of as base-station antennas mounted on masts or on top of buildings. Commonly used in urban areas, the antennas of Microcells are generally lower than the average building height. Umbrella cells are also important gaps, normally used to fill in the signal gaps between different cells.

Cellular radius is determined by antenna height, propagation conditions, and gain,  ranging from 100 plus meters to even tens of kilometers. The actual maximum distance in use is up to 35 km according to the GSM specification. The cells can also be extended, which means the radius of the cell can be doubled or extended or more.  Indoor coverage can also be realized by using the power distributor, which can distribute the outdoor antenna power to the indoor antenna. Indoor high-density calling is common in the places like airports and shopping malls. But the truth is, it is not a necessity as the wireless signals through the building can achieve indoor coverage, but this calling is also meaningful since it reduces echo and improves signal quality.  

Five TYPICAL applications of GSM modules  

1. Access control system controlled by mobile phone  

Use GSM to control the electronic lock of the access control system, if you need to enter the door, as long as you dial the mobile phone card number in the GSM module, the door will automatically open, and only the mobile phone number you set can open the door, and there is no cost.  

2. Three turn the billboard disaster weather emergency closure  

Three double billboards are achieved by motor continuously flip display multiple AD content, because install outside, when the disaster weather such as strong winds and hail, billboard easily blown bad or damage to the card dead need emergency shut down at this moment, you can use the relay normally closed contacts to control the power of the billboard, then all you have to send the “off” control message,  The billboard will automatically close, and automatically return to normal after a certain time delay (the general disaster weather will not last for a long time) if you want to open the billboard in advance, you can send “open” control message.  

3. Urge payment of the balance of the engineering system  

Some engineering is safe after the completion of the normal operation after some time to get the balance settlement, if the customer malicious default payment for goods, the installer very often has a headache because the device has been installed, if come back down the loss is very big, very costly, especially the customer then can install the first GSM module in customer’s system, use it for one way or multi-way control system of some key points, when the customer maliciously delinquent payment can be closed by SMS some functions, forcing the customer to pay off the payment and then immediately SMS open, if the payment has been successfully recovered can also borrow system maintenance in the name of the GSM module removed from the customer system.  

4. Alarm and reset of monitoring system or website server  

Monitoring system or web server error may crash after a long-running, then power reduction is one of the few solutions, then scan through the GSM module of power supply control system, and set to open automatically after 3 seconds off mode, can realize the power is reset, in addition, the GSM module in some special applications also play a very big role, such as the disappearance of the main power supply, memory error, cooling fan shutdown, fuel depletion, someone intrusion, and other information, is the ideal choice for UAV room monitoring.  

5. Remote control of smart home appliances  

It is easy to turn on smart home appliances such as rice cookers and water heaters remotely through SMS control. It is also possible to control air conditioners by controlling remote controls or switching to maintenance mode.  

8. GSM IoT solution  

GSM IoT solution

Solution of Internet of Things in GSM-R electromagnetic environment testing  

To meet the needs of high-speed railway IoT industry development, the Internet of Things technology is applied in the field of GSM-R electromagnetic environment testing. The system design makes full use of the advantages of wireless sensor network technology in the field of measurement and control, assists the electromagnetic environment test equipment to collect the temperature, humidity, car distance, and other information in the GSM-R electromagnetic environment test environment, real-time transmission through the Internet, and complete the data reception, storage, processing and analysis in the computer software; The test experiment of the electromagnetic environment in the GSM-R band of a railway section shows that the system can obtain the interference signal intensity and other information of the interfered station in the measured section, which confirms the application value of the Internet of Things technology in GSM-R electromagnetic environment test.

Gsm-r IoT solution in the power supply of railway system  

Gsm-r system is an important means of railway communication, and the reliable power supply of GSM-R network equipment is one of the basic conditions for the reliable operation of the GSM-R system. This paper aims at the power supply mode of base stations and repeat stations that exist along a large number of routes, such as connecting railways with 10kV and using self-closing lines to set pole-type transformer stations to get power nearby. By using Internet of Things sensing technology and intelligent distribution technology, the reliable power supply of the railway GSM-R system is guaranteed by intelligent sensing and monitoring means.  

The power amplifier is disabled in the GSM network  

Based on the energy saving and emission reduction of the GSM network, the application of power amplifier turn-off technology in the GSM network is studied.  The adaptive environment of two kinds of power amplifier turn-off technology is analyzed and the comparison results are given. The results show that the best consumption reduction can be achieved by the rational application of power amplifier turn-off technology.  

Application of GSM monitoring of Internet of Things in MBTF wastewater treatment  

The application of the electronic control device module is based on the GSM network in MBTF sewage treatment, the electronic control device module is a set of computer microprocessor technology, wireless data transmission, and wireless remote control in one of the integrated electrical equipment control integrated module, through the mobile phone terminal formed a sewage treatment Internet of things architecture. The functions and methods of the electronic control device module are shown in detail.  

9. The history of GSM  

The history of GSM

As we mentioned above, GSM is a digital Mobile phone network standard developed by Europe, also named the Global System for Mobile Communications. GSM belongs to the second generation (2G) cellular mobile technology, as opposed to the first generation of analog cellular mobile technology used in the 1980s. Back in 1982, there are a few analog cellular mobile systems were operated in Europe, among these, the typical one is TACS (Full Access Communication System) in the UK. Some countries in Western Europe have domestic mobile services back in that time.  The disadvantage is these systems were domestic, you can not use them aboard. Therefore, it will be a great promotion if there is a common system for people to uniform use mobile phones throughout Europe. In 1982, the Nordic countries stand out and submitted a proposal to the Conference Europe of Post and Telecommunications. They proposed that a common European telecommunications service specification in the 900MHz band should be developed. The result was a “Group Special Mobile” (GSM) was established under a committee at the conference, The GSM was founded to develop standards and offer recommendations.

In 1986, in Paris, the group carried out field tests of eight proposed systems based on dog sizing studies and experiments conducted by European countries and companies.  

On September 7, 1987, operators and managers from 17 European countries signed a Memorandum of Understanding (MOU) on the implementation of the 900MHz digital cellular mobile Communication standard in Europe in Copenhagen, and subsequently established the MOU group to work on the development of the GSM standard.  

The specification of GSM900 was completed in 1990, resulting in about 130 recommendations.  The different proposals have been grouped into a series of 12 proposals for the TEST GSM standard.  

The first System was opened in Europe in 1991, and the MOU organization designed and registered a market trademark For the System, changing the name of GSM to Global System For Mobile Communications. Since the year 1991, mobile communication has come into the second-generation digital mobile communication era.