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

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