Mobile Internet on PDA and laptop. Mobile Internet on PDAs and laptops Garpy GPS monitoring system for moving objects

Modern systems Energy metering is increasingly using GSM networks for data transmission, which is supported by GSM operators, who have largely exhausted the possibility of increasing the subscriber base of voice services. GSM networks are characterized by a developed infrastructure in all regions, high reliability, the ability to quickly deploy and low cost characteristics.

Analyst-TS LLC, Moscow

All modern GPRS modems are built on the basis of GSM modules from several foreign manufacturers. The simplicity of organizing access from a computer to the Internet on their basis creates a misleading impression that there are no difficulties when using them in industrial systems(availability on computer Windows drivers and periodic freezes requiring operator intervention are not noticeable). To control the GSM module the following can be used:

Functional controller of a meter, heat meter or concentrator;

Specialized (telecommunications) controller;

Software is built into the GSM module and takes on all the tasks of managing communication stability.

With all types of control implementation, it is necessary to go through the thorny path of turning the GSM module into a full-fledged GPRS modem that ensures stable operation in continuous and unattended mode:

Systems running on the desktop suddenly begin to fail and freeze when moving to real objects, when changing the operator, installing in another region or increasing network load;

It turns out that significant efforts are required to handle emergency situations, ensure stability and security, test solutions, take into account regional characteristics of operators, support work with dynamic IP addresses, provide access to the state of the modem and network during data transfer, etc.

Of course, there will be organizations that can solve the problems that arise, but is this economically justified for the majority? The implementation difficulties discussed above lead to the appearance on the market of complete solutions with high functionality. Their cost is, of course, a little higher, but this is the price for a kind of PnP (plug and play).

We will try to formulate the basic requirements for GPRS modems and, to the extent possible, justify them.

Basic requirements for GPRS modems

General requirements

Support for basic GSM network services: GPRS/EDGE, CSD and SMS.

Interfaces for connecting to metering devices: RS-232C (including “three-wire” - RxD, TxD and GND), RS-485, Industrial Ethernet.

Design: DIN rail mounting, built-in primary power supply with extended ranges ~140...286 V / 45...55 Hz or =18...36 V, operating temperature range -40...+70°C.

GSM antenna: connectivity must be provided external antenna, which can be moved from the equipment installation area (for example, from the basement) to the area of ​​reliable radio reception.

Automatic connection establishment

After turning on the power, modems must automatically activate the establishment of a GPRS/EDGE or CSD channel and, in some cases, provide automatic generation of SMS messages when “events” occur on additional logical inputs (for example, when fire and security alarm sensors are triggered).

Ensuring reliability

The following transmission channel reservation methods must be used:

At the routing level - between GSM operators (two SIM cards);

At the level of GSM services - transition from GPRS/EDGE to CSD or SMS messages.

In conditions of periodic destruction of channels without server and client signaling (for example, when rebooting the APN servers of a GSM operator), monitoring system freezes using an independent watchdog timer, built-in transparent Ping control of the connection and monitoring the time of no data play a big role. At the same time, it is necessary to ensure that the user can optimize the ratio of “depth of channel control / traffic (cost)”.

Rice. Scheme of organization of the GPRS channel ASKUPE

Security

Authentication at the stages of initialization, connection establishment and data transfer, including:

To prevent the possibility of using SIM cards for other purposes (when setting up the modem, the values ​​of their PIN codes must be entered, which are subsequently stored in the modem’s memory, checked at startup and cannot be read);

Authentication of access to the APN server;

Control exchange of identifiers when establishing a TCP connection (between two modems or a modem and a server);

Caller number control when establishing a CSD channel.

Using a VPN tunnel between the GSM operator and the dispatch center server.

In some cases, additional data encryption is required, the use of which is limited by law.

Comprehensive solution for communication channel

The use of modems on a distributed network of metering devices must be supported by software (telecommunication server), which is installed on the server in the control room and provides:

Easy connection of functional software, for example via TCP/IP;

Security and stability of the transmission channel (ping, identifiers, etc.);

Built-in routing, for example for additional ports or process software.

Data flow optimization

Data buffering (8...32 kbytes) built into the modem allows you to increase the transmission speed by optimizing the interaction between the RS-232C/RS‑485 interface and the TCP/IP socket, as well as use modems in systems with a “three-wire” interface.

Rice. Scheme of organization of the GPRS channel of the MOSCAD system

Provide support for different operating modes

Depending on the characteristics of the problem being solved, modems must support operating modes combined into two classes.

Monitoring and management of remote objects from a central node with the ability to optimize according to various criteria, for example, maximum functionality, minimum traffic, inability to use the Internet on the server side, or the need to use an SMS service along with GPRS/EDGE channels.

The second class of tasks to be solved is the organization of communication between two points - a radio interface extender (RS-232C or RS-485). In this case, modems must automatically provide a transparent data transmission channel between the interfaces when the power is turned on.

Ensuring Compatibility

To organize a reliable GPRS/EDGE connection with metering devices that are critical to breaking the packets they receive, for example, those using Modbus or Profibus field buses, it is necessary to eliminate temporary breaks in data packets on the receiving side. The hope of being able to fend off broken packets by re-polling or working with short packets leads to the emergence of systems that only work on the developer's desk.

Operational Requirements

Automated remote configuration of modems via CSD or GPRS/EDGE channels without visiting sites, for example: during installation, the factory configuration is used, during testing it is changed to the system integrator’s configuration, during operation - to the customer’s configuration;

Upgrading the software built into the modem directly on site, ideally via a GSM network;

Local and remote analysis of GSM network parameters, allowing you to adjust the position of the antenna, analyze surrounding GSM cells, select a telecom operator that provides the best working conditions at the point where the modem is installed, analyze the reasons for the deterioration of communication during operation;

Automatic control of the SIM card account balance and notification if it decreases to a specified level;

Creation and provision of remote access to log files of interaction processes with the GSM network.

Additional features

Of particular interest is the combination of the functions of a modem and a meter (or part thereof) in one device to reduce the overall cost. A prerequisite for this is the presence of powerful computing resources in the modems. Examples of such devices:

Modems with built-in functional software that provides interaction with metering devices (for example, autonomous reading and accumulation of measurement results);

Modems with multiple interfaces, providing multiplexing of data from several interfaces in a common radio channel for the independent operation of several systems.

Service software

Working with GPRS modems must be supported by a set of technological software that provides configuration, testing, remote configuration, monitoring and management of additional interfaces, remote analysis of GSM network parameters, modernization of the modem’s built-in software, TCP/IP and OPC server functions.

conclusions

GPRS modems used in energy metering systems have significant differences from modems used to access the Internet. Demands on them are constantly increasing. To date, the author is not aware of the implementation of all the requirements discussed above in one modem, which is probably not required, given the cost criterion. The article would not be complete without the examples below of using AnCom RM/D GPRS modems in energy metering systems.

Implementation examples

ASKUPE (Automated system for commercial accounting of energy consumption). Project implemented by OJSC "MOEK" (Moscow United Energy Company), 2009.

The goal of the project is to provide technical and commercial accounting of thermal energy at Moscow facilities served by MOEK, which is 70% of all residential buildings and industrial structures in the capital.

Let's consider a system of remote access to heat metering devices implemented in ASKUPE. The company "COMKOR" (trademark "AKADO-Telecom") is building a corporate multi-service network for OJSC "MOEK", within which access to heat metering devices is provided according to digital channels AKADO, where they are, and via GPRS channels of the GSM operator MTS. The task of providing information security data transfer is solved using a special MTS service for corporate clients(dedicated APN, local static IP address). System integrators (NPO Teplovizor and LLC Eurocom) use AnCom RM/D modems (more than 800 metering points) in automated control systems.

When installing modems, the main problems were related to the choice of location for installing the GSM antenna in the basement. The following methodology was developed:

All operations discussed below are carried out with the SIM card of the GSM operator selected in the system;

Search for areas where there is a signal (at least a minimum level) - using a cell phone, often near windows, vents or specific places near the walls;

Zone control using AnCom RM/D modem and NetMonitor GSM_RM software. The signal strength, number and type of visible GSM cells are measured. It is necessary to provide:

Level more than minus 95 (RxLev: -65…-95);

The MNC of the visible cells must match the MNC of the SIM card operator (if the SIM card operator's cells are not available for access to emergency services information about available cells of other operators is provided);

Visibility of more than 3 cells, one of which is preferably GSM-1800 - it has more free slots (BCCHfreq: GSM-900 from 1 to 124 and GSM-1800 from 512 to 885);

The presence of a high signal level, but 1…2 GSM-900 cells may in some cases not provide a stable GPRS connection due to their high load (IP address is not provided);

Monitoring the operation of GPRS (providing an IP address from the network side) using a modem (the mode for issuing technological information is turned on) and GTem software (the presence of a GSM connection does not always guarantee the operation of GPRS);

Control of operation in the system (standard settings).

A general approach to organizing GPRS communication has been defined:

It is wrong to try to use antennas with very long wires (attenuation per 5 m of RG58 wire at 1800 is 4.5 dB);

In most cases, it is more correct to move the modem to an area of ​​reliable reception, using the RS-485 interface for communication between the modem and the heat metering device;

As a result, the use of modems built into a heat metering device is often difficult;

Timeouts to ensure communication stability must be selected taking into account the period of polling of heat metering devices (including in test mode) and the period of interruption of unused sockets from the GSM operator;

It is advisable to use an antenna with low cable attenuation and high gain (for example, Ant K996A 900/1800 MHz: gain, dBi - 5/4; cable attenuation 5 m, dB - 1.8/2.5).

The telemetry system for gas metering units “MOSCAD” was implemented by Indasoft LLC, 2007–2009.

A commercial metering system that provides control over gas consumption modes, monitoring the condition of metering and security alarm equipment. Installation and commissioning of the first and second stages were carried out: 1,464 objects in 15 regions of the Russian Federation. Significant experience has been gained in using GPRS communications in various regions.

Features of the implementation lie in the ideology of the “active control point”: the remote controller independently monitors changes in process parameters and makes a decision on sending data to the upper level in accordance with predefined settings, rather than waiting for its turn in a cyclic poll of metering nodes.

The use of Motorola's specialized MDLC protocol ensures data delivery to the control center of a regional gas company, remote configuration and programming of all controllers in the system. Through the Internet gateway of the regional gas company and the communication server, the data enters the controller top level ACE 3600. The controller “parses” the MDLC package, extracts the data from the gas metering unit, processes it, places it in the internal database and initiates transmission to the data server, which ensures the provision of data to the dispatch systems of the regional gas company.

Protection of information from unauthorized access is ensured at the MDLC protocol level due to the isolation of telemetry system modems from other GPRS subscribers mobile operator by separating them into a separate group with its own access point (APN server) and creating a VPN tunnel. Reliability parameters are ensured by GSM operator redundancy (two SIM cards).

Conclusion

The AnCom RM/D wireless GPRS modem is an important element of any modern distributed energy metering system. Providing reliable communication in the system, GPRS modems make it possible to combine hundreds and thousands of remote metering devices into a single information network. The use of AnCom RM/D GPRS modems in automated accounting systems allows you to receive accurate, reliable information on energy consumption in real time, eliminate the influence of the human factor, prevent emergency situations, monitor the technical condition of devices and premises and, as a result, generally increase economic effect from the use of metering devices.

I.V. Dianov, technical director,

LLC "Analyst-TS", Moscow,

Organizing Internet access on a PDA or laptop today is not a big problem. In principle, a laptop is an ordinary computer, which, as a rule, has all standard interfaces (Ethernet, USB) or a regular analog modem for dial-up access over a public telephone line (dial-up). With a pocket computer (unless, of course, it is a communicator) it will be more complicated to connect to a modem via USB, it must have a USB-Hub or some kind of wireless interface (accordingly, the device that provides it with access to the Internet must have the same wireless interface ).

It is clear that both the PDA and the laptop are mobile devices, so it would be stupid to entangle them with wires to access the Internet. Therefore, let's talk about wireless methods of accessing the Internet from these mobile devices.

There are several ways to organize mobile wireless Internet access. Of these, the most popular and universal currently in Russia is cellular communication using a regular GSM phone, which allows you to organize high speed access to the Internet using GPRS technology (in this case, the gateway to the Network is cellular telephone). However, in this case, sometimes problems arise with sharing laptop and phone, since this requires using a wired connection (USB or RS-232), which is not very convenient in camping conditions, or wireless communication (Bluetooth, InfraRed, Wi-Fi), which is also not always suitable (after all, everything is on the phone -you still need to talk).

GSM/GPRS modem with USB interface

The cheapest and most universal solution for equipping a PDA or laptop with mobile Internet are GSM/GPRS modems with a USB interface. And there are quite a lot of such devices on sale today.

Some of them are simply GPRS/GPS modems without the ability to use talk mode, while others allow you to connect a hands-free headset, with which you can talk on the phone from a computer.

However, despite their compactness, such models are not very convenient to use, since they are “hung” on a PDA or laptop using an additional cord, require separate storage, get lost and generally limit mobility (for example, to use a USB device with a PDA you often also need additional interface cradle).

GSM/GPRS PCMCIA cards

If you do not want to use a combination of a phone and a laptop to access the Internet, then you can purchase a special PCMCIA card that allows you to organize high-speed access to the Global Network and turn your laptop into a full-featured mobile phone with the ability to conduct conversations and also send faxes and SMS/MMS messages. By the way, keep in mind that to connect to the Internet, the GSM operator and the corresponding tariff plan must support GPRS.

There are not many cards with PCMCIA interface (PC-card Type II) on sale today. Some of them, like those described above, are simply GPRS/GPS modems without the ability to use talk mode, but such an acquisition does not seem to us to be a good one. After all, at the speed of a GPRS connection, the use of tools such as Skype or others that allow speaking can cause delays in speech transmission, and considerable voice traffic will have to be paid at GPRS rates, which will certainly be more expensive than a regular call to a mobile phone located in another city or even country.

So, in our opinion, more attractive are modems that have a jack for connecting a headset that allows you to talk on the phone from a computer, and simple software for emulating all the functions of a telephone such, for example, as OvisLink WGP-1500, Billionton PCMCIA GPRS/GSM Wareless modem or Neodrive GPRS-100S (the kit includes a passive headset on a special clip, an earpiece and a sensitive microphone).

Other features of such modems include the presence of two or three GSM bands (GSM 900, 1800, 1900), a convenient location of the SIM card compartment and an original antenna design (it can be removable). For example, in the Billionton modem, the antenna design allows you to either hide it inside the device, making it as compact as possible, or extend it, positioning it for better reception quality. And the Neodrive GPRS-100S modem has an external rotating antenna, but although its design looks more reliable than that of the Billionton modem, this device is less compact.

To access the Internet, just install the drivers for the corresponding PCMCIA card and configure network connection, however, if you want to use all the functions of the phone, you need to install special software. The virtual keyboard and functions of this software are typically implemented in a familiar “telephone” design and provide simple dialing and answering functionality. Of course, navigating through the menu of such a phone is big screen using a laptop is much easier than looking at icons on the small screen of a cell phone. In addition, such software can provide panels with additional functions. From the program you can establish a GPRS connection, send SMS, e-mail and fax, as well as manage your notebook, synchronize data with the organizer and perform all the same operations as on the phone.

To use such a card as a regular mobile phone You must, of course, connect the included headset (these devices do not work with the laptop’s microphone and speakers). After which you can answer incoming calls or call someone, just like using the headset of a regular phone. The only difference between a PCMCIA card and a phone with a headset is that the system can only be used while working with a laptop, that is, if the laptop is turned off, then you won’t be able to use such a phone.

GSM/GPRS CompactFlash cards

However, only laptops have a PCMCIA interface, so a PDA cannot be connected to the Internet using the devices described above. But there are more universal solutions based on CompactFlash (CF) or Secure Digital (SD) interfaces, which can be used with both laptops and PDAs.

For example, Neodrive has a model GPRS-110S, which is identical in characteristics to the GPRS-100S model for PCMCIA, but has a CF interface, which allows you to connect it to pocket computer with such an interface and turn it into a communicator.

GSM/GPRS CF and SD cards are usually more complex and therefore more expensive than PCMCIA-based GPRS modems. This is due to the need to use additional battery, which is located on the device. And this battery accordingly requires additional indication of its status, the ability to supply external power and a charging plug. To charge the battery in the Neodrive GPRS-110S, a special USB adapter is used, which is connected to the power connector located on the front of the device, next to the antenna.

The Neodrive GPRS-110S comes complete with a headset including an earpiece and a sensitive microphone on a special clip.

Devices based on CompactFlash and Security Digital are universal: in order to use them in a laptop, you only need a special adapter for PCMCIA (the Neodrive GPRS-110S has a CF/PCMCIA adapter included in the package). To use the GPRS-110S model together with a PDA, the package also includes the Pocket PhoneTools program, which in its functionality and interface is similar to the PhoneTools version for a laptop, that is, it turns the PDA into a regular cell phone (or rather, into a communicator).

Unfortunately, when using such GPRS modems as a telephone, it is impossible to connect a wireless bluetooth headset, even if the PDA has such an interface. The fact is that GSM telephony of such modems only works with their own headsets and does not use the capabilities of the computer.

Let us note in conclusion that the price of such devices offered on the Russian market varies from 100 to 300 dollars.

Leica, along with high-precision equipment for the geodetic industry, also produces GIS-class satellite receivers. These receivers are intended for use in geographic information systems, navigation, cartography, and other industries where the priority is not millimeter accuracy in determining coordinates, but speed, mobility, and additional capabilities software, as well as the simplicity and convenience of geospatial data collection.

Leica GIS satellite receivers are advanced field measurement tools that allow you to create or update GIS data of any size and purpose. The distinctive features of Leica GIS receivers from geodetic class satellite receivers is that they are designed in the form of a monoblock, combining them in one compact housing satellite receiver, receiving antenna, Leica radio or cellular modem, control controller.

The Leica GIS receiver series is ideal for you if you are involved in mobile mapping, property surveying or utility locating and need direct in-field coordinates for your geographic information system. By obtaining coordinates with sub-meter accuracy in real time, you have the opportunity to simplify the survey process itself, since the need for post-processing in the office is eliminated. Leica GIS receivers are widely used by professionals Maintenance, emergency response teams, field inspectors and public utilities.

Standard modem Leica is a compact device that looks like a field controller. The front side of the Prior is occupied by a bright and clear touch display, providing quick and convenient data entry and editing, and control of the shooting process. Powerful processor and impressive volume random access memory allows you to work with large amounts of data without any restrictions. Often, modern GIS receivers are equipped with digital cameras, built-in speakers and microphone, expansion slots for memory cards and USB connectors.

The Bluetooth and Wi-fi wireless technologies found in modern Leica GIS receivers offer enhanced data reception and transmission capabilities, allowing you to connect to mobile phones or tablet computers for receiving corrections in real time from a real or virtual VRS base station, for downloading maps via the Internet. You can also quickly connect to various equipment, such as laser rangefinders, barcode scanners or digital cameras for getting additional features in the field.

Although Leica GIS receivers are primarily designed for stand-alone operation with sub-meter accuracy, you can always turn it into a high-precision survey receiver and obtain coordinates with millimeter accuracy. All you need to do is connect a sensitive external antenna and use your GIS receiver like a regular field rover for post-processed or real-time surveys. Some Leica GIS receivers may come standard with a built-in receiving radio or GSM modem.

Select and buy a Leica modem in Moscow you can in the store or on the RUSGEOKOM website. We also deliver to other regions.

The American company Enfora is well known throughout the world, including in Russia, as one of the leading manufacturers of modules and modems for GPS systems for tracking moving objects (Fleet Management). These devices are widely used by automobile, rail and sea transport companies, insurance companies, as well as shops selling cars, motorcycles, boats and yachts. The Enfora product line also includes personal GPS trackers designed to monitor the location of people and allow you to send an alarm signal with exact coordinates to several numbers in the form of an SMS message.

How GPS tracking systems work

Currently, GPS/GSM monitoring systems (GPS/GSM Fleet Management, abbreviated as GPS FM) offer a huge range of services both for professional transport, trading and insurance companies, and for the private sector. The use of modern control and management methods will optimize the transportation system, significantly reduce the cost of fuel and lubricants and transport repairs, and also prevent theft and seizure of vehicles and cargo.

According to one of the leading American statistical firms, Aberdeen Group, more than a million GPS FM devices are in use in the United States. On average across the country, the use of GPS/GSM monitoring systems showed the following results:

• increase in transportation efficiency by 12.2%;
• increase in vehicle utilization rate - 13.0%;
• reduction in cargo delivery time by 14.8%;
• reduction in operator errors by 27.9%;
• reduction of consequences from attempts to kidnap and seize transport and cargo by 32.1%;
• annual savings on vehicle repair costs - $1100/vehicle;
• annual wage fund savings due to reduced transportation time - $1,625/person;
• annual wage fund savings (due to the introduction automated system management and reduction in the number of dispatchers) - $1300/person;
• annual cost savings on fuel and lubricants due to route optimization - $1,700/vehicle.

The operating principle of GPS FM systems is shown in Fig. 1.

GPS monitoring systems for moving objects are essentially complex transport automated control systems using tracking satellites, ground base stations, mobile devices tracking (GPS-tracker), software package, central control center. GPS satellites constantly rotate around the Earth, placed on 6 orbital planes with orbits of 20,200 km and an inclination of 55°. On board each satellite there are transmitters that continuously emit signals at two frequencies: 1575.42 and 1227.60 MHz. A GPS/GSM mobile terminal installed at a controlled object collects the maximum possible amount of data from satellites and sends it via GPRS to a central server.

Such central servers can be supported both at local corporate levels and on a regional or global scale. In turn, the server processes data from satellites and creates a file of current calculations of detailed geodetic information. In general, the central server receives information from all controlled objects, the number of which is limited only by the power of the server itself and the application software used. The operator on the central server can observe accurate navigation information about all objects, received in real time from the start to the finish of the route. In addition, the database stores archival data about each object, cargo, vehicle and the driver. Enfora equipment and modern software for GPS/GSM monitoring systems allow you to receive the following information at the central control center:

• precise geophysical coordinates of the object, updated every few seconds;
• position of the controlled object on terrain maps in real time;
• movement speed;
• general technical information about the car, driver, cargo;
• history of turning the ignition on and off;
• current tire pressure information;
• history of fuel consumption for the entire period of movement (refueling and draining);
• the route specified by the dispatcher and the actual trajectory of movement;
• distance traveled at a specific point in time;
• expected time of arrival at a given point;
• time of continuous operation of the engine;
• temperature inside the car and outside;
• cars that do not respond to the dispatcher's request;
• medical parameters of the driver (pulse, pressure, temperature).

If necessary, the noted software functions can be modified taking into account the individual characteristics of the customer. For example, insurance companies can enter information about the policyholder, his cargo and vehicle into the database. Companies selling vehicles have the opportunity to monitor the timeliness of customer payments. Car rental companies can see their clients anywhere in the world.

In addition, the operator can plan individual routes and send them to the driver via GSM/GPRS network. It is also possible to change and optimize the route taking into account traffic conditions, road repairs, and meteorological conditions. The operator can inform the driver about the need for an unscheduled stop for rest or repair, as well as the coordinates of the most favorable place for these purposes. In case of unforeseen circumstances, you can quickly change the vehicle and cargo delivery conditions. As one of the options for the security system, it is possible to record within a few seconds at the central control center any deviation from the given route and send a corresponding notification to the driver’s phone, PDA or navigator.

In the USA, with the support of the government, there is and is developing a program to create global network coordinated with the 911 rescue service. If, in case of danger, you press the emergency button of a mobile terminal (phone, PDA, navigator), then the coordinates of the tracked object will be in the nearest rescue service point and in the central control room within a few seconds. These measures lead to noticeable savings Money and increasing company profits. In addition, they make the driver’s daily work safer and more efficient, as well as increase control over his work.

Enfora Spider series GPS/GSM modems

Especially for GPS monitoring systems, Enfora produces a series of modems under the general name Spider. The main technical characteristics of modems in this series are shown in Table 1. The series includes five models: Spider MT-Gu GSM2338, Spider MT-Gi GSM2354, Spider MT-Gi GSM2356, Spider mini MT GSM2228, Spider AT GSM5108.

Spider MT-Gu GSM2338 is a stationary GPS/GSM/GPRS tracker, designed primarily for road transport. It is rigidly mounted in the vehicle interior. This model made in an impact-resistant plastic case in accordance with international automotive standards. Product dimensions - 65?61?26 mm. The modem is designed for operation in the temperature range –30…+85 °C. The modem uses external GSM and GPS antennas. FACKRA RF automotive radio frequency connectors are used to connect antennas. The GSM/GPRS unit is based on the Enfora GSM0308 module. The GPS unit uses a 12-channel receiver based on the Enfora Enabler L GPS0401 module.

The modem supports exchange protocols: NMEA, TAIP, Enfora binary. The modem exchanges NMEA messages with the central server in the following formats: GGA, GLL, GSV, GSA, RMC, VTG. There is a function for storing GPS messages in the module's non-volatile memory. A technique has been developed for Enfora GPS navigators that allows you to display GPS information on various interactive maps. This allows you not only to receive coordinates on the central server, but also to observe the position of the object on the map in real time. The GSM2338 model supports PPP, UDP API, TCP API, UDP PAD, TCP PAD, AT commands via GPRS channel and via SMS. This allows you to fully utilize the unique advantages of Enfora products, primarily PAD and Event Tools.

Other additional functionality includes the following:

To power the GSM2338 modem, an extended voltage range is used - 7–40 V. There is a built-in Li-ion battery. Appearance GSM2338 is shown in Fig. 2.

The front panel contains a SIM card holder with an automatic ejector and three LED indicators of operating modes. The rear panel contains FACRA antenna connectors, a Molex 43024-0800 connector for user I/O, and a 2.5mm Headset connector. The Molex connector contains contacts for connecting power: from the ignition key and from the battery. Additionally, this connector has two programmable I/O pins: one general purpose and a 2-wire serial interface (Tx, Rx). User I/O allows you to connect various external devices to the modem and configure them using the Event Engine. Programmable I/O GPIO1 (pin 7 of the Molex 43024-0800 connector) can be set high or low, respectively, with the commands: AT$IOPULUP = 1 or AT$IOPULUP = 0.

Similarly, GPIO2 input/output (pin 8 of the connector) is programmed using AT commands. External circuits can be connected to a special pin GPIO3 (pin 6). The maximum load current on this pin should not exceed 250 mA. When the modem is rebooted, the state of this pin changes; a minus signal is supplied to GPIO4 (pin 4). The modem is programmed using the Event engine in such a way that in the absence of external power, the device operates from the internal battery. If necessary, a message about this event can be sent in the form of an SMS or UDP message. GPIO5 receives constant power directly from the battery. When the power is turned off at this pin, the modem restarts. This erases all GPS data. GPIO6 and GPIO7 I/O pins (pins 2, 3) are for 3-wire serial interface (Tx, Rx, GND). They can also be configured to monitor the status of GPS and GSM/GPRS communications. GPIO8 (pin 1) is supplied with power from the ignition key. This pin can also be used as a toggle pin when programming with Event tools. The modem can be programmed to send NMEA messages in the following cases:

• the specified time has expired;
• the specified mileage has been exceeded;
• the specified speed was exceeded;
• presence in a zone with specified coordinates is recorded;
• there was a change in the state of user input/output;
• the ignition is turned on/off;
• satellites appeared/disappeared.

To debug equipment, you can use the Enfora test server, which is constantly open to free access. With its help, you can control SMS, NMEA messages from the GSM2338 modem, and also change its configuration. The model is available in two versions: GSM2338-00 with a built-in backup battery and GSM2338-01 without a battery.

Spider MT-Gi GSM2354, Spider MT-Gi GSM2356 differ from the GSM2338 model discussed above in that they have built-in GSM and GPS antennas. In addition, these two models do not have a voice channel. The GSM2354 model is designed to operate in the American frequency range 850/1900 MHz, the GSM2356 model is designed for the European frequency range 900/1800 MHz. These models are also available in versions with and without battery.

Enfora Mini-MT GSM2228 is a portable, miniature GPS/GSM/GPRS tracker designed primarily for monitoring a person’s location. This model can be very useful as a mobile panic button for the elderly and children. In addition, this model can also be used as a removable transport tracker. The appearance of GSM2228 is shown in Fig. 3. The modem is manufactured in a sealed plastic case, its dimensions: 100×59×25 mm.

The modem has a universal purpose and allows you to manually and automatic mode determine current coordinates and transmit this information via GSM channel to specified phone numbers or central server. The model provides an emergency signal transmission mode to a given number when pressing one key. Access to GPS data is possible in NMEA and SUPL formats. The modem is self-powered from a built-in battery. IN basic configuration A 1340 mAh Li-ion battery is supplied. The battery is charged via a USB connector from a car or network adapter. The modem is controlled using four function keys.

The Push To Call button allows you to call a pre-programmed number. The Mini-MT modem can send emergency SMS to 5 different addresses.

The Set Geo-Fence button is designed to search within a specified radius. Search boundaries can be changed by the user and stored in the module memory. In the case when no satellite is visible, GSM2228 generates sound signal errors, warning the user to get out from under blocking cover (metal roof, wet tree leaves, thick concrete walls, etc.).

The function programming button (User-Defined button) is designed to select the required GSM2228 function. For example, you can select the following functions: call a number other than the one programmed using the emergency call button; search within a radius other than the factory setting; send an SMS with current coordinates to a GSM number or to a central server, etc.

Operating modes are controlled using four LED indicators. Via a USB port, you can output GPS NMEA data to a PC for working with maps and programming the GSM2228. The Headphone Jack connector is used to connect a voice headset in cases where it is not needed Speakerphone. The voice communication system allows you to talk to a pre-programmed caller as if you were using a regular cell phone.

In normal operating mode, the GSM2228 will send the user's NMEA coordinates to the central server at specified intervals. To activate this mode, it is enough to write several commands that determine the addresses of the modem and server, as well as set the transmission modes. As with the GSM2338, the GSM2228 modem can be programmed so that it sends SMS or UDP messages when an event occurs (specified time, distance, speed, zone with given coordinates, etc.).

Enfora Spider AT GSM5108 is an autonomous GPS/GSM/GPRS tracker designed specifically for monitoring the location and movement of various objects placed in temporary or long-term storage (cargo containers, mothballed equipment, reserve tanks with fuel or drinking water, etc. ). The main difference between the Spider AT and its existing analogues is its record low power consumption at battery life. This model can work without recharging the battery for up to three years!

The Spider AT modem is made on the basis of the micro-power GSM/GPRS module Enabler III Low Power Platform (LPP), which is a combined GSM/GPRS and GPS module with a built-in microcontroller. It should be especially emphasized that the LPP0108 module is designed to operate in standby mode. It sends information about current coordinates only in the event of an emergency or upon a direct request from the central server. This is precisely the fundamental difference between LPP0108 and other combined GSM/GPS modules (GPS0401–GSM0308, MLG0208) designed for continuous monitoring of traffic and constantly transmitting geophysical information dozens of times per minute. Therefore, the Enabler Low-Power Platform (LPP) module, LPP0108, cannot be used as a transport tracker.

In order to minimize power consumption, all control of the Spider AT modem is entrusted to a central server located at the control center. In this case, setting parameters and monitoring the operation of Spider AT is carried out remotely through Enfora Services Gateway. For this purpose, Provisioner software is used, designed specifically for Spider AT. The Spider AT GSM5108 modem is manufactured in a vandal-proof housing and has built-in GSM and GPS antennas (Fig. 4).

The Spider AT modem is a completely complete device, which includes:

• base module LPP0108;
• embedded Texas Instruments MSP430 microcontroller used for control and data processing.
• rechargeable battery BAT-0007-0001, 4200 mAh;
• SIM card holder;
• dust- and moisture-proof housing made of impact-resistant polystyrene;
• built-in GSM and GPS antennas.

Overall dimensions - 147×63×20 mm. Weight - 168 g. The GSM5108 modem operates in fully automatic mode and does not require additional maintenance. Depending on the modification, Spider AT is equipped with either a built-in motion sensor (LPP0108) or a built-in accelerometer (LPP0118-40). LPP0108 is used to capture the slightest movement. At the same time, its signals are analyzed by a microcontroller and compared with GPS signals. This approach allows you to avoid false triggering of an alarm signal corresponding to the start of movement. The microcontroller processes the data, generates GPS NMEA messages and sends them via the GSM/GPRS unit to the central server. On the other hand, from the central server you can use the UDP API channel to transmit control commands to the module and change its operating modes.

The basic Spider AT modem module has two user inputs and two user outputs. Custom I/Os can be programmed using Event Processing to trigger tamper switches, motion sensors, audio sensors, temperature sensors, etc. When an alarm is received from external sensors or the measured parameters deviate from the specified parameters, the module generates an output event signal, for example, sends an SMS or UDP message to a central server via a GSM/GPRS network. Control over the operation and configuration of Spider AT parameters is carried out remotely through the management server using the Enfora Services Gateway (ESG) service. In this case, standard Internet protocols are used, which allows you to control more than 100 thousand Spider AT modems from one server. The ESG service provides full support and processing of GPS messages. This application can be easily integrated into an existing IP network. In principle, ESG provides the ability to work with any remote devices that support IP protocols. Using ESG can significantly reduce money and time when developing and operating systems for monitoring the movement of remote objects.

To directly control the modem, the Provisioner Software (PS) application software, developed specifically for the Spider AT, is used. It should be noted that Spider AT GSM5108 can only be used in conjunction with PS. Set application programs PS allows you to manage the GSM5108 device remotely, via GSM/GPRS, using a support server and Enfora Services Gateway.

The Provisioner software package supports major industrial applications such as MS SQL Server, MySQL, Oracle. Therefore, if it is necessary to introduce additional operating modes, you can order an individual user version, taking into account the specifics of monitoring the status of specific devices. The concept of programming and controlling the Spider AT modem is based on combining individual tasks into various logical groups. This approach allows you to sort certain events by topic and quickly find adequate reactions to them.

An example is a container movement tracking system at a large terminal. Each container arriving at the warehouse receives its own Spider AT. Information about the cargo, conditions and periods of its storage is entered into the database. In accordance with these data, control and response scenarios are determined. For example, you need to store this container at a certain temperature and ship it from a warehouse to certain time. By comparing the readings of Spider AT modems from other containers, the dispatcher selects the optimal group of containers and the optimal location for placing this container in a certain group. For example, the following can be planned as an emergency event:

• removal of the container from the warehouse ahead of schedule;
• unauthorized movement of a container to another area;
• container falling from the top row;
• unauthorized opening of the container;
• excess storage temperature, etc.

Response actions are taken according to specific scenarios. When advancing emergency situation Spider AT transmits an alarm message, which is sent to the support server through the Gateway service.

The received information is processed using Provisioner and compared with information from the user application and the database. As a result, the user is prompted to immediately take certain response actions. In addition, alarm signals can also be sent to various security, police and emergency services in parallel.

The Provisioner program allows four configuration options for modem parameters designed for different operating modes of the GSM5108. For example, in static mode, the modem sends messages about its status according to a predetermined schedule. In dynamic mode, the modem reports the beginning and end of movement at predetermined time intervals. This mode is most often used in cases where it is necessary to quickly record the fact that a controlled object has begun to move (ATMs, vending machines, office equipment). Border violation modes use various combinations of movement between specified zones and take into account events such as, for example, leaving the zone, entering another zone, and the speed of movement between zones.

Provisioner software is available for an additional fee in the form of licensed disks designed to work with a varying number of controlled objects. For example, Provisioner License EWS0201 is designed for one device. Additionally, you can order Enfora Provisioner Support (catalog number EWP0201).

GPS navigation and vehicle monitoring systems based on Garmin navigators and Enfora modems

The world leader in the production of GPS navigators, Garmin, and Enfora entered into an agreement in 2008 to support Garmin Fleet Management Interface (GFMI) v2 with Spider Gu GSM2338 modems. Combining a Garmin car GPS navigator and an Enfora GSM2338 GPS/GSM tracker in one device made it possible to create a closed tracking system “GPS satellite – vehicle – central control center – rescue services.” The GFMI system allows fleet tracking companies to provide an interactive service to both fleet and trucking owners and individuals. With GFMI, dispatchers can track a vehicle in real time and adjust its operating mode. On the other hand, the driver can contact the dispatcher and request the necessary information from him.

A diagram illustrating the operating principle of GFMI is shown in Fig. 5.

To work together, you need special software with GFMI support - both for the Garmin navigator and for the Enfora modem. Enfora PKG47 and Garmin software versions 6.10 support GFMI. To activate the FMI function in GSM2338, you must obtain from Enfora additional code access for each modem. Please note that not all GPS navigators can work with the Enfora GSM2338 modem. The list of navigators that support Enfora-Garmin FMI is given in Table 2.

When working in pairs, the RS232 port of the Enfora GSM2338 modem is connected to USB port Garmin navigator using a special Garmin FMI cable 010, which has an interface converter and a 5 V power supply. GFMI functions are controlled using special AT commands developed by Enfora. These commands are sent from the central server via the TCP API protocol via a GSM/GPRS channel to the GSM2338 modem. Having received this command, the modem generates FMI messages and transmits them via the RS232 port to the Garmin navigator. The navigator processes them and displays the result on the display screen. At the same time, the response is transmitted through the USB port of the navigator to the GSM2338 modem, which forwards it via the GSM/GPRS channel to the central server. In its simplest form, the Garmin-Enfora FMI pair can be tested using the Enfora support server. In order to access this site, it is enough to first register the APN, UDPIP, Friends, Port parameters in the GSM2338 modem. From this site you can send control commands to the GSM2338 modem (Fig. 6).

For example, the command AT$GFMI = 1 is transmitted via the GSM2338 modem to the Garmin Nuvi 205 navigator and activates the GFMI function. At the same time, a new window appears in the main menu of the navigator with the inscription “Dispatcher”. The main GFMI menu of the Garmin Nuvi 205 navigator contains four main sections (Fig. 7):

• stops;
• messages;
• find a place;
• about the driver.

The Nuvi 205 navigator has a Touch screen (the corresponding menu item can be selected by simply touching the corresponding picture). The driver and dispatcher can exchange arbitrary messages. To do this, you need to select the menu item “Outgoing messages” and type the desired text on the keyboard that appears (Fig. 8).

Having received the command AT$GFMI=6.0002, “59.50827”, “30.22929”, “TESS NORTH WEST” from the server, the driver will see on the navigator screen the coordinates (latitude and longitude), as well as the name (“TESS North-West”) of the next unscheduled stop. Planned points are set by the dispatcher in advance and stored in the navigator in the “My stops” section. The driver can follow the route from stop to stop using the navigator. Each passage or failure to pass a given point is controlled by the dispatcher.

The GFMI support philosophy is based on the built-in software of the Enfora Event Engine modules. All messages generated by the GSM2338 modem and sent by it to the central server are output events of this software. For example, if the driver received a message on the navigator about the need to stop, read it or deleted it, the following commands will be sent to the server: AT$EVENT=89,1,89,100,104; AT$EVENT=89,3,40,89,1075864263 // SEND UDP Message to the Server. There are currently thirty-one AT$GFMI commands and thirty-eight AT$EVENT commands in the GFMI control list. They are described in detail in the document.

Currently version 6.0 (FMI V1, FMI V2) of Garmin software supports the following services:

• • free-form text messages (128 characters);
  • stops;
  • time of arrival at a given point;
  • automatic notification of arrival at a given point (or delay);
  • updating (changing) route data from the control center;
  • message delivery confirmation (FMI V2);
  • standard driver responses, up to 200 messages (FMI V2);
  • personal data about the driver (FMI V2);
  • technical condition of the car;
  • minute-by-minute transport status messages (FMI V2);
  • pinging modem GSM2338 (FMI V2);
  • additional data filled in by the client.

Garmin Fleet Management Interface protocols are open. There is a detailed description of them and instructions for developing the corresponding application software Garmin Fleet Management Interface Control, Specification. In addition, Garmin offers a turnkey application software solution for the central GFMI server. An example of the interface of such a program is shown in Fig. 9.

The interface of this program is adapted for an ordinary dispatcher who does not have special skills in working with GPS navigation systems. The main menu contains function keys corresponding to the GFMI protocols listed above. With one keystroke, the dispatcher can select the appropriate service and set the necessary parameters (Fig. 10). The main parameters of the monitored object are constantly displayed on the screen: current time, number of registered satellites, coordinates, speed of movement.

The introduction of two-way communication between the control center and the driver in tracking systems has significantly improved the vehicle safety system. If, for some reason, GPS data from a specific vehicle disappears on the dispatcher’s screen, the driver immediately receives a text request on his navigator. If there is no answer, the dispatcher can remotely block the ignition and doors and send an alarm message to the rescue service. In addition, the GSM2338 modem has a “panic button” function. Therefore, in critical situations, the driver can send an emergency message to the dispatcher himself.

The Garmin Fleet Management Interface GPS tracking system is widely used throughout the world. The site lists about seventy large partner companies, such as Trimble Mobile Resource Management, SkyPatrol, Datalink Systems, GPS-Buddy, Beacon Wireless, etc. That’s why transport companies, and individuals can choose a GPS tracking system to suit their individual needs.

GPS tracking system for moving objects Garpy

An example of the use of Enfora modems in Russian GPS monitoring is the Garpy tracking system developed by Olikom SPb. This Russian company sells Enfora products on a VAD (value added dealer) basis. Additional services include technical consultations, support and maintenance, accessories, installation and commissioning of equipment, and warranty service. Using the Garpy GPS monitoring system, the user can independently monitor the current location of his vehicle (V) on a computer screen or PDA at any time from anywhere in the world.

To view information about an object, you need any PC or PDA with Internet access. No specialized software is required to work with the GPS monitoring system, subscription fee not charged. However, it should be emphasized that only those clients who purchased GPS/GSM navigation equipment directly from Olikom SPb can use the Garpy system. Access to the monitoring system website is carried out using an individual login and password. Therefore, outsiders cannot obtain information about the controlled object of another client. The main interface of the Garpy system is shown in Fig. eleven.

The Garpy tracking system can work with both regular raster maps and maps from OS Maps, Google, Yandex, Hybrid Maps, etc. (Fig. 12). Switching between operating modes is carried out using virtual keys located in the right corner of the screen (Figure 11).
There is a pop-up menu in the left corner of the Garpy interface. The user has the opportunity to observe the following information in real time:

• unique vehicle login;
• time of the last response of the vehicle;
• address of the location of the vehicle’s last response;
• position of the vehicle at a given time on the area map;
• current account balance for the SIM card used in the GPS-GSM modem.

When you press the “Trajectories” key, a graphic image vehicle movement trajectories over the past two days. The points and duration of stops will also be marked on the map (Fig. 12).

When you press the “Settings” button, a menu will appear with the following items:

• Devices.
• Zones.
• Events.
• Reports.
• Profile.

The “Devices” section contains data about the vehicle, connected GPS/GSM equipment, monitored peripheral devices car (ignition, doors, fuel control sensor, temperature sensor, tire pressure sensor, etc.). In the "Zones" section you can designate different zones on the map. When you click on a zone with a selected name, for example, “Center of St. Petersburg,” its appearance immediately appears on the monitor screen. In the “Events” section, at the user’s request, certain incidents that occurred with a specific vehicle are noted. The “Reports” section stores an archive of vehicle parking records indicating the date, duration and addresses. The user can independently delete outdated parking archives. In the “View” mode, you select the format of the output home page menu of data about a specific vehicle. The “Profile” section stores the client’s personal contact information.

To connect to the Garpy GPS monitoring system, you must fill out a technical specification form, which indicates the type and brand of vehicle (the number of vehicles per user is not limited), the type and brand of GPS/GSM equipment, and connected peripheral automotive equipment. For corporate customers it is possible to develop, manufacture and connect additional control modules according to individual specifications. In addition, it is possible to place a Garpy-type monitoring system server directly at the customer’s site. More detailed information information about the operation of the Garpy system can be found on the websites. To get acquainted with the demo version of this system, you need to go to the website and use the same a codeword“demo” as login and password.

In the last couple of years, messages about the release of more and more new models of devices belonging to a special class of hardware - GPRS modems have become regular. What is it?
Very briefly, GPRS modems can be characterized as another type of wireless data transmission devices. Their fundamental difference from other devices in this group is that they operate using one of the variants of packet information transmission technology implemented in networks cellular communications GSM standard and called General Packet Radio Service, or GPRS for short. The development of this technology is the two largest Russian companies cellular communications - VimpelCom and Mobile TeleSystems - began back in 2000, and now the total number of cellular networks in the world that have implemented GPRS is already in the hundreds. Organizational issues are being resolved in full swing international roaming for subscribers working in this mode. All the main properties and features of the operation and parameters of this type of wireless modems, due to the use of such technical solution

, become clearer after familiarizing yourself with the essence of GPRS technology itself. Our magazine already wrote about this topic about a year and a half ago, so now we will only briefly recall the main point.
Why was GPRS created? The current stage of development of our industrial society has led to the fact that for the successful operation of many modern “information industries” it is not required that a person be geographically “tied” to any individual machine, premises or even the entire production complex, but it is only necessary that he I was just constantly “in touch”. Numerous telecommunications, and primarily mobile ones, partly make it possible to solve this problem. But if a person, for example, by the nature of his work must participate in the collective processing of large amounts of data, then the telephone does not really save the situation.
After all, spending hours dictating or checking over the phone many numbers in some summaries or reports is not a pleasant task. And it’s difficult to call such work effective. It’s another matter if this data, literally with one keystroke, can be quickly transferred to any necessary subscriber and others can be received just as easily. In this case, for successful collaboration, it no longer matters where you are: in the office, at home, in a train compartment, in another city or abroad...
In general, according to analysts, people's needs for mobile transmission data in the foreseeable future will increase annually by at least one and a half times. Of course, we must not forget that the ability to transmit data in cellular communications was realized almost from the very beginning of the operation of such networks, but only in practice this opportunity for a long time turned out to be almost theoretical - people didn’t really want to use it - literally a few percent of total number
subscribers all over the world! And there were two main reasons: slow and expensive. Indeed, for example, even modern second-generation cellular communications of the GSM standard provide data transmission at a speed of only 9.6 kbit/s. You can imagine how “modern” this speed is by simply remembering that users of modems on regular telephone lines They completely abandoned such speeds more than five years ago. And the very method of communication via a voice channel with per-minute payment made being online, although possible, but very expensive. It is to eliminate these shortcomings that GPRS technology was invented. Its goal was to significantly increase the speed of data transmission over cellular communication channels, as well as provide a “always-on” mode for subscribers, similar to how it is implemented in local computer networks . But unlike local networks

, the working area here turns out to be the entire coverage area of ​​the cellular network used, and taking into account roaming - almost all areas of the Earth where GSM cellular networks operate. Such coverage is not available today, in fact, to any other
First of all, it should be noted that GPRS technology is intended for use only in digital cellular networks of the GSM standard, implemented on the basis of the Time Division Multiple Access (TDMA) method. GPRS owes its appearance to the use of TDMA features.
To put it simply, the essence of the TDMA method is as follows. The entire operating time of one radio communication channel is divided into standard time intervals, distributed in turn among several subscribers. As a result of this, it is possible to transmit several conversations at once on one radio frequency, or organize several independent data exchange channels. In the GSM standard, the maximum number of such channels is eight.
Such temporary division of the communication channel between several users allows you to increase the number of simultaneously served subscribers, however, all channels are busy only during rare moments of peak load in the cellular network. The rest of the time, some of these channels are free. It is on this feature that the idea of ​​GPRS technology was based: in cases where a subscriber requires high-speed information transfer, he can temporarily “give” him free time slots in a given radio channel. Thus, the speed of information transfer can immediately increase several times.
But that is not all. The GSM channel itself can provide a slightly higher information transfer rate if other coding methods are used. Without a noticeable reduction in quality, the data rate can be increased to 14.4 kbit/s, and potentially even up to 22.8 kbit/s. the size of an entire typewritten page can be accomplished in just tenths of a second. And if we take into account that the delay time inherent in GPRS technology for the allocation of radio resources for transmitting a data packet should not exceed 1 second, then the exchange of small amounts of information between users will occur almost instantly. Such significant changes in the conditions of data exchange using mobile terminals also open up numerous new opportunities.

Functionality
One of the biggest advantages of the GPRS mode is that the subscriber device does not “take up the line” during pauses between receiving and transmitting data. The cellular network operator’s equipment simply “remembers” that the user is ready to transmit or receive data, and radio channel resources are allocated to him only for the duration of information exchange. In other words, any GPRS devices can be in communication continuously (if, of course, they are turned on and located within the network coverage area) - in a “constant” state virtual connection". In this case, the operator does not need to require the subscriber to pay for the entire time of his connection with mobile network(actually 24 hours a day), but only the intervals of active operation of its terminal or the volume of transmitted and received information.
Great opportunities GPRS technology also opens up the development of telemetry transmission systems, remote monitoring, security systems, industrial electronics, etc. GPRS technology is also convenient for cellular network operators, since it is a modernization existing networks GSM on the path of their development to third generation communication systems does not require a radical replacement of equipment. True, from this point of view, subscribers, on the contrary, are the losers - to use GPRS services, they definitely need special terminals that support this technology.

User equipment
Accepted GPRS implementation scenarios provide for a gradual increase in data transfer rates. This was done, in particular, due to the limitations imposed by current subscriber terminals. The fact is that the maximum speed of receiving and transmitting information that a mobile terminal can provide depends on the number of channels (number of time slots) it supports for reception and transmission. So far, all produced GPRS subscriber terminals are capable of supporting from 2 to 4 channels for receiving information and 1 or 2 channels for transmitting. This allows you to get maximum speed reception up to 57.6 kbit/s and transmission - up to 28.8 kbit/s (real speeds, depending on the load of the cellular network and determined by the actual availability of time slots free from voice traffic, can change noticeably during operation and in practice be significantly below). In the future, we should expect the emergence of GPRS terminals that support a larger (up to 7) number of channels for reception and transmission and are capable of providing higher communication speeds. From the standpoint of the operating algorithm, the standard provides for the existence of GPRS terminals of three different classes:
- class A models must provide the ability to simultaneously work in telephone mode and in GPRS mode;
- Class B terminals also support both voice connections and packet data transmission, but these modes are not implemented simultaneously - during data transmission via GPRS, the subscriber cannot make and receive voice calls, but the terminal must quickly respond to incoming calls and allow without loss of data pause the session to respond to phone call;
- class C is focused on working in turn in modes - GPRS and telephone.
In fact, all mobile phones currently produced in the world with GPRS support (and this is already more than fifty models) belong to class B and have means for connecting them to a computer via a special cable or infrared port. And one of the advantageous embodiments of class C devices (although classes A and B are not excluded) can be GPRS modems, implemented either in the form of a PC card connected to a laptop computer, or in the form of small-sized GPRS modules aimed at use in the most various equipment - from laptop computers to industrial electronics.

GPRS modems and modules
The number of models of such devices actually available now is already several dozen, and in the very near future it will undoubtedly increase, because many well-known companies are engaged in their creation today: Ericsson, Motorola, Nokia, Novatel, Olitec, Option International, Pretec Electronics, Real Time Devices, Siemens, Sony, Wavecom, Xircom and others, who sensitively grasped the promise of this direction.
What are the main advantages of using specialized devices, compared to using conventional mobile phones with GPRS support?
Several of them can be named, and they are determined, first of all, by the design features, as well as the functionality and parameters of such modules, which determine the areas of their primary use. For ease of explanation, all these features can be divided into several groups:
- "Wide functionality ". This is not just a slogan - many devices of this type are designed to operate in several (or even all!) frequency ranges used modern networks GSM (EGSM-850 MHz, GSM-900 MHz, DCS-1800 MHz, PCS-1900 MHz), which allows the use of such modems almost all over the world. Also, the versatility of using such devices is ensured by the fact that they often implement several data transmission technologies possible in GSM networks: a traditional GSM modem (speed 9.6 kbit/s), packet transmission in GPRS mode and transmission in line switching mode using HSCSD (High Speed ​​Circuit Switched Data) technology, which is similar in methods and parameters to GPRS.
-In addition, modern GPRS modems, as a rule, support all the functions provided for by the development phase of the GSM 2+ standard, including SIM Application Toolkit, etc. As a result, the user also has access to the functions of a regular mobile phone: voice communication, receiving and sending faxes , SMS, etc."Everything you need for work and nothing extra"
- .- ensure the design of modems and the “unpretentiousness” of some of them to supply voltages. Purely structurally, existing GPRS modems can be divided into three groups. The first of them, which can be conventionally called “office”, includes devices made in the form of Type II PC cards (PCMCIA), aimed at connecting and using in conjunction with laptop computers. The second group may include models intended for integration into other devices, and therefore characterized by maximum “lightweight” design. The third group consists of models for industrial use, which, on the contrary, have a “protected” design that ensures their reliable operation in a wide range of temperatures, humidity, pressure, vibration, electromagnetic fields and other types of influences. Such models often have a wide-range (for example, from 5 to 32 V) internal supply voltage stabilizer, which allows them to be directly connected to a wide variety of sources (Li-ion batteries, vehicle on-board power supply, various industrial devices, etc.). Some models of the last two groups are complemented by other devices (GPS receiver, analog-to-digital converter, etc.), which further expands their functionality and areas of application.
The use of GPRS modems and modules is particularly promising for the implementation of “machine-to-machine” communications, the area of ​​which includes a very large circle of the most various applications: security equipment for cars and homes, industrial and home automation, telemetry equipment and systems for monitoring parameters and movements of various objects, mobile office and much, much more. In other words, GPRS modems can be useful in all cases where laying a communication cable or deploying a specialized wireless system for one reason or another (organizational, technical, economic) turns out to be impossible or impractical. It is also important that you do not need to obtain any special permission to operate GPRS modems. To use them you just need to buy SIM card
In general, it should be noted that GPRS, despite the existence of other technologies for high-speed data transmission over cellular channels (for example, Cellular Digital Packet Data for networks of the D-AMPS standard, High Speed ​​Packet Data for systems with code division of signals according to the cdmaOne standard, etc. .), due to the current actual global dominance of GSM, is simply “doomed” to become one of the key technologies for wireless data transmission in the next decade (before the widespread use of 3G, Wi-Fi, etc. networks).
Igor Skolotnev