DCom special measuring equipment for O2 laboratories

O2 Czech Republic, a.s. is the largest integrated telecommunications operator in the Czech market. It takes great care to ensure the top quality of its telecommunications network services and before putting a new technology or technical solution into operation, it undergoes a very thorough testing in their test lab in Prague-Brumlovka. Within the laboratory tests, the settings and the software compatibility is verified and it is searched whether it is more beneficial to use components from a single manufacturer or whether devices of different brands should be combined. All these actions are performed in the testing laboratory. Such a laboratory should be a part of the technological base of each mobile operator.
In the O2 test lab, several specialists are employed full-time. There, however, often work even whole teams of technicians from suppliers. Their task is to propose technical solutions so that in full operation, everything works smoothly. In the testing lab, they make an effort to anticipate all negative phenomena before the customers could notice them.
The development in mobile communication requires more tests of mobile phones and base stations proper functioning. For testing the radio, part of these devices- specialized measuring instruments called radio testers- are used. Universal high-frequency measurement devices – power meters, generators, spectrum analysers, etc. – can be used too. None of these devices, nevertheless, enables to test the behaviour of the entire network, or at least a part of it (i.e. several base stations, several mobile phones and a possible interference from other users of the radio spectrum). To simulate a realistic environment in the laboratory, a complex testing tool, in professional terminology called “interconnection coaxial matrix”, is vital. Signals entering the measurement process must first be lowered at the appropriate level and then mixed. Interfering signals are added to useful signals in accordance with the needs of the measurements.

A special measuring equipment GSM TestBed

DCom, s.r.o. designed and manufactured a specialized measuring equipment: GSM TestBed, which enables to test the behaviour of a network consisting of 1-16 base stations, 1-4 mobile phones and 12 internal jammers with frequencies from 400MHz to 2.5GHz. (These are not noise generators.) The frequency band was chosen in order to cover all GSM / UMTS / LTE bands, i.e. 800, 900, 1800 and 1900, 2100MHz and further 450MHz band for O2 system CDMA.

The basis of the device is an adjustable coupler 8X4X12 (16X2X12) of signals, which allows to con-nect any connected base station with any connected mobile phone and, furthermore, to connect any interfering signal with any mobile phone. The range of the signal levels processed by TestBed is from 50W (+ 47dBm) as for the base stations, through 5W (+ 37dB) for mobile phones and -40dB for generators to -160dBm for receivers. The electrical and mechanical concept of the whole device, made as a construction set of repeating modules, was subordinated to successful achievement of the regulatory scope. This concept was proved to be correct and, on top of that, it simplifies repairs or reconfiguration of TestBed.
The control of the whole TestBed is possible in two ways – either by direct setting of individual components (attenuators, RF switches, noise generators, etc.) or via scripts – batches of predefined commands allowing long-term testing. In both cases the user is connected via Ethernet interface. This solution was chosen because of an easy remote monitoring. It allows the installation of TestBed together with the tested devices to a separated area, preferably shielded chamber, where the influence of external environment is further reduced. Thanks to the modular concept of the device, it enables a quick conversion of TestBed for other purposes, such as testing in WiMax system in 3,5GHz band.

Multi-channel program-controlled attenuators

Multi-channel program-controlled attenuators allow software, very quick setting and change of the level of individual measured signals according to the testing needs to measure the behaviour of the mobile devices in the real run.

Shielded boxes

Another special product tailor-made according to customer´s needs are shielded boxes, ensuring that results are not affected by external influences. For the needs of the operator, there were delivered two types of shielded boxes.

Shield Box 1
Frequency range: up to 2,5 GHz standard, up to 20 GHz optional.
Shielding efficiency: 60-70 dB GSM/UMTS/CDMA/LTE bands, i.e. 450, 800, 900, 1800 and 1900, 2100, 2600MHz.
Dimensions: 800*800*1200mm (W, D, H)
Network filter: FHA1-10A-230V AC 10A 230V
Optical connection: 100Mbit Ethernet

Suitable for testing of mobile devices without the need to be connect through an antenna. Especially for LTE Multiple-input multiple-output (MIMO), the second type of shielded box: Shield Box 2 was designed. This box is equipped with an internal antenna and non-reflective 3D environment.

Shield Box 2
Frequency range: up to 2,5 GHz.
Shielding efficiency: 60-70 dB GSM/UMTS/CDMA/LTE bands, i.e. 450, 800, 900, 1800 and 1900, 2100, 2600MHz.
Dimensions: 950*1200*1500mm (W, D, H)
Inner detachable VF absorbers – Spires height 20cm, attached with Velcro
3D internal antenna
Internal swivel stand for a mobile device
Filtered input: 230V /10A
Optical connection: 100Mbit Ethernet

Posted in News

AGRO PILOT

AGRO PILOT

Modern technologies are rapidly penetrating into agriculture. The level of robotics and automation has significantly advanced and new technologies are helping to facilitate and improve hard work of people in this industry. Farms and farmers in the Czech Republic gradually modernize their fleet. Modern farming machinery is powerful, but expensive at the same time. That is why it is important to make maximum use of it so that the investment is quickly returned. In crop farming, machines must often return to the same place several times during the growing season when ploughing, sowing crops, spraying application, harvesting, etc. To achieve top results while saving the cost of expensive seeds and fertilizers and to obtain subsidies, precision is crucial.

Why the precise positioning is so important in agricultural production

Modern agricultural machines are usually already prepared for or directly equipped with electronic control systems, so called autopilots that use a GPS navigation system for automated machine guidance. In the automatic mode, the operator does not have to be occupied with driving the machine, but checks the correct operation of all systems and pays attention to potential hazards that could endanger an employee or a machine in the field. The operator operates the machine according to the instructions of the control system only at turnabouts. The autopilot function is controlled with a prepared configuration and map data that are pre-loaded into the machine, so the operation itself is not complicated.
The problem with the use of GPS navigation for the control of agricultural technology is a lack of accuracy. GPS system standardly achieves an accuracy of three meters on average, which, moreover, changes over time. If the configuration of satellites to the GPS receiver is unfavourable, the error can be even greater. This is sufficient for most applications, but for the needs of agricultural production, this is insufficient. For the improvement of accuracy, various correction methods are used. The best performance is reached with systems with a reference station. Deviation on the border area with a maximum distance from a reference station oscillates up to 3 cm using these systems. They have very good repeatability, so when the machine returns to the same place in half a year, it drives along the same line, along the same furrow and so does not destroy grown plants. Without the use of precise navigation tools, approximately 20% of the fields remain unused. A man driven machine can never be as precise as a machine controlled by robotic navigation.
Large machines also have problems in turns. Sharp turns are very complicated and slow down the cultivation of the needed area. Using precise navigation of a working machine, the option of a field cultivation with omitting a line and with wide turns can be used. Skipped rows are cultivated during the second passage.
If spraying is inaccurate, there occur areas that are unsprayed and strips where the spray was applied twice. In both cases this costs farms considerable sums of money because spraying was consumed, but a part of the surface was not treated and a part was sprayed too much.
Data from machines controlled this way can be used for reverse engineering, which can track the yield of each crop in an observed area and adapt the machines for seeding or fertilizing.
A great advantage is that when the machine is controlled by autopilot the same results can be achieved in reduced visibility or at night and the machine can be utilised for the maximum period possible.
Another reason for accurate positioning is subsidies and division of land, where the absolute position against the Czech cadastre is crucial. The problem is that the GPS system uses the WGS84 coordinate system and the Czech cadastre uses the S-JTSK coordinate system. These coordinate systems are calculated in a completely different way. Conversion of these exists but thanks to the movement of lithospheric plates, it changes over time. It should not happen that the machinery gets in someone else´s land during the cultivation. As for getting subsidies, the exact localizing of land is also important because there is a relatively small tolerance of up to 10% of the cultivated area.

System for increasing the accuracy of satellite navigation with GPS system

Satellite systems

To increase the accuracy of determining the position of the GPS system, there are several transmission systems of correction data available. There are satellite systems of correction. Their advantage is that they do not need any additional data transmission system but unfortunately they do not have sufficient accuracy and repeatability because the correction data are calculated for a large area. To obtain corrections, satellites in stationary orbits are used. Basic systems for satellite correction are the US WAAS and the European EGNOS. These systems have been developed for and are used for example in aviation and shipping. Modern GPS receivers can already work with these data. The problem with these systems during their usage in agriculture is that it is necessary to have a view to the south, where the satellites are placed in geostationary orbit. In the case that the view is shadowed, the correction is not available. Another option of positioning improvement is the simultaneous use of the Russian GLONASS system, which can be used by modern GPS receivers as well. When using these correction methods and means a good short term accuracy can be achieved but unfortunately sufficient repeatability of precise location, so that the agricultural machine would return to exactly the same place on the cultivated field at the next working cycle with an error up to several centimetres, cannot.

Correction with a ground reference station

Ground correction systems use correction against a fixed point where the location is precisely known. In such an explicitly defined point, a correction station is placed. It determines individual satellites´ errors against the actual position.
Global systems use a network of stations and interpolate correction for a given area of interest. They offer sending correction signals as a service. The price of the service consists of a fixed price for a license for each machine and an annual fee for service operation. The price of these services is relatively high for Czech farmers. Further problems with these global solutions are reliability and availability of these services in the required area. In countries with a flat terrain such as the USA or the Netherlands, these systems work well. Data from these services are transmitted via mobile networks. The availability of these networks in sparsely populated areas with a complex terrain profile is usually not good enough to enable infallible usage of this system. In case that an agricultural machine loses a correction signal, it stops within 30 seconds and must be controlled by an operator.

Agro Pilot system

GPS Agro Pillot system was developed in cooperation with Zemědělské družstvo Rostěnice farm.
Our solution uses its own reference base station with a transmitter of correction signals in the VHF or UHF bands; both bands are suitable for this purpose. Correction data are encoded into a data stream and continuously transmitted by a reference station. In individual agricultural machines, radio modems are placed, which receive the signal, decode and transmit it to the control computer. With one reference station built up in this way, an area with a radius of approximately 15 kilometres can be operated. When building up a system for the distribution of correction data, building a reference station is the most expensive. On the other hand the number of machines which can use the data from the reference station is not limited (data travel unidirectionally from the reference station to the machines). Individual farms in the region can share a reference station, use it together, and the cost of the initial investment can be divided among multiple users.
For the transmission of correction data there are a number of different protocols available. Well-known are protocols by Trimble company: CMR, CMR +, RTCM open protocol supported by most manufacturers. Agro Pilot system is able to send two protocols simultaneously and the user is not dependent on a single supplier of technology.
To cover the area which is not available due to the terrain profile or the distance of a machine from the reference station, repeaters that receive signals from the main reference station and transmit it to the desired area can be built. Unlike other solutions, an unlimited number of repeater stations can be theoretically realised. Data from one reference station are applicable with repetition of up to 30 km from the reference station with respect to the maximum permissible error. Agricultural machinery in operation automatically chooses the best signal and smoothly moves from the coverage area of one reference station to another.
As part of this project even a reference station located in a place without electricity was successfully implemented using solar panels.
The system offers a very quick return of investment because as for big modern machines financial losses per hour of work without an autopilot can reach several thousand Czech crowns according to the experience of users.
Our company has many years´ experience building radio and telemetry networks and we are able to provide the user with a complex service ranging from a radio project with arranging the appropriate permits, delivery and installation to the subsequent long-term maintenance of the technology.

Advantages of the solution

  • Affordable price
  • Coverage of a vast territory according to customer needs
  • Using repeaters for enlarging the area covered
  • Private radio network which is not dependent on another provider and the need to pay charges for data transfer
  • Accuracy and repeatability of positioning with a tolerance of 3 cm
  • Simultaneous support of two different protocols for the transmission of correction data
  • Considerable saving of fertilizer, seeds, fuel, more efficient use of fields, full use of modern technology
  • Possibility of sharing a reference station among multiple farms in the region
  • Unlimited number of machines using a reference station
Posted in News, Telemetry and Control Systems

MikroEXPO 2012

Uherské Hradiště 18.7.2012

Professional radio stations Hytera and Integrated dispatching system were introduced by Mr. Radomir Dvorak in his speech in the Hall of Culture House, then

Mr. Jan Zbytovský presented the development of a new duplexer and splitter for 5,6 GHz band. Radio stations, and in the near future also the duplexer, can be found on our e-shop.

 

Posted in News, Trainings and presentation

Czech Raildays 2012

Railway station Ostrava main station from 19th to 21st June 2012

Dear friends, Company Dcom spol. s r.o. would like to invite you to the International fair of railway technology Czech Raildays 2012; which will be held from 19th to 21st June 2012 in the commercial part of the railway station Ostrava main station. More information about the fair: http://www.railvolution.net/czechraildays/

At the Fair we will exhibit our complete Integrated dispatching system RV3, antennas VHF, UHF, GSM and Hytera professional radios.
You can find us in Hall A1, Stand No. 24, where we exhibit along with AŽD Praha.

We look forward to meeting you.

Posted in News

Amper 2012

Brno Fair ground, 20. – 23. March 2012

Dear business partners, we would like to invite you to visit our exposure at the AMPER 2012 international Trade Fair at Brno Fair ground.We will show you professional analog and digital radios Hytera for firefighters, law enforcement agencies, transport companies, taxis, industry, agriculture and forestry. You will see an integrated dispatch system for all types of communication including voice recording module for use in transport, rescue and security forces.
You will find us in Hall P, Booth No. 163. We are looking forward to your visit.

Posted in News