GPS modem for computer. GPRS modems
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 Internet access using GPRS technology (in this case, the gateway to the Network is a cell phone). However, in this case, sometimes problems arise with sharing a 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, you still need to talk on the phone).
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 in order 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, you just need to install drivers for the appropriate PCMCIA card and set up a network connection, but 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 the menu of such a phone on a large laptop screen is much easier than looking at icons on a small cell phone screen. In addition, such software may 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 microphone and speakers of a laptop). 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 a 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 an additional battery, which is placed 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.
Modern energy metering systems are 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 of the absence of difficulties when using them in industrial systems (the presence of a driver on a Windows computer 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: it is necessary to provide the ability to connect an external antenna, which can be moved from the equipment installation area (for example, from the basement) to an 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 lack of data play an important 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 COMCOR company (AKADO-Telecom trademark) is building a corporate multiservice network for MOEK OJSC, within which access to heat metering devices is provided via AKADO digital channels, where they exist, and via GPRS channels of the GSM operator MTS. The problem of ensuring information security of data transmission 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 unavailable 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. We have gained significant experience 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 ACE 3600 upper-level controller. The controller “parses” the MDLC package, extracts the gas metering node data, processes it, places it in the internal database and initiates transmission to the data server, which provides providing data to dispatch systems of a regional gas company.
Protection of information from unauthorized access is ensured at the MDLC protocol level thanks to the isolation of telemetry system modems from other GPRS subscribers of the cellular operator by separating them into a separate group with their 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,
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, additional software capabilities, as well as simplicity and convenience of collecting geospatial data.
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 made in the form of a monoblock, combining in one compact body a satellite receiver, a receiving antenna, a Leica radio or cellular modem, and a 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 maintenance professionals, emergency response teams, field inspectors and utility companies.
The standard Leica modem 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. A powerful processor and an impressive amount of RAM 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.
Bluetooth and Wi-Fi wireless technologies found on modern Leica GIS receivers offer advanced data transmission and reception capabilities, allowing connection to mobile phones or tablet computers to receive real-time corrections from a real or virtual VRS base station for downloading cards via the Internet. You can also quickly connect to a variety of equipment, such as laser rangefinders, barcode scanners or digital cameras, for additional capabilities 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.
Transferring information over networks GPRS allows you to easily create systems for remote dispatch and control of devices, as well as stationary and moving objects. By using GPRS modems for data transmission, you can replace the CSD connection (modem connection of two nodes) widely used in GSM with a GPRS connection. Given the current tariffs of all telecom operators, this is significantly more economically profitable.
InSAT company offers a wide selection GPRS modems. The most popular for industrial applications are GPRS modems produced by MOXA, ICP DAS, Segnetics, iRZ, ARIES, TELEOFICE companies.
Russian manufacturers of GPRS modems
Among domestic manufacturers, we offer products from companies such as OWEN, iRZ, Segnetics and TELEOFICE.
The OWEN company produces a wide range of equipment for industrial automation, dispatching and accounting systems. GPRS modem PM01 produced by OVEN has proven itself in a large number of real projects.
The TELEOFICE company specializes in the production of communications equipment. It offers a wide range of products, including GPRS and GSM modems.
iRZ is an international manufacturer of wireless products and integrated solutions. The uniqueness of the iRZ policy lies in the flexibility of the architecture of products and solutions, the highly efficient use of the latest technologies and sensitivity to the dynamics of market development. The iRZ model range is distinguished by high quality components, support for the latest technologies and moderate cost. The company's products are not inferior in characteristics to products from the world's leading manufacturers.