F. A. Q.

1.
Q. The most of the radio cards, radio bridges and other equipments of this kind for the wireless RadioEthernet networks have the performance range of 100-200 m and can operate within 0-40C temperature range. Can this equipment be used for deploying MAN or establishing links over the distance of several dozens km and in regions with the inclement climate?
A. When RadioEthernet networks are being deployed all radiounits (cards, bridges) are installed inside the buildings. The equipment, which increases the performance range -antennas, amplifiers and cables -, is installed on roofs, masts. It's weatherproof and can operate within a temperature range -50+50C, humidity up to 100%.

2.
Q. In many cases the LAN's, which are supposed to be connected are situated in the lower floors of the buildings. At the same time antennas have to be mounted on the roofs or masts. What can be the max length of the cable between an antenna and a radio unit and by what means can it be realized?
A. Without using an amplifier the maximum length of the cable can be up to 30m depending on the length of the radioline, the antenna type, the mast height ect. With an amplifier the cable length can be up to 100m. Using an additional compensating amplifier it can be up to 150-200m.

3.
Q. Very often there is no line of the sight between two points supposed to be connected because of hills, forests and other obstacles. Is it possible to establish a radio link in such a case? If yes, by what means can it be realized?
A. In many cases the use of directional antennas with a high gain and amplifiers (or active antennas with built-in amplifiers) can provide the stable connection even when it seems there is no line of sight. The right choice of a place for the antenna and a height of its mounting is also very important.

4.
Q. Very often in the region of where the new RadioEthernet network is supposed to be deployed a lot of other radio systems work in neighboring or the same frequency bands. How the interferences can be decreased?
A. The interference can be decreased with using narrow-band filters and directional antennas. Another solution is to use up/down converters, which allow the wireless network to operate in another license free band (e.g. in 5.7GHz instead of 2.4GHz). This converter has a function of an amplifier and can be installed up to 100m away from the radiounit.

5.
Q. What are the main features of the amplifiers with AGC offered by your company? When is it advisable or necessary to use WISTEC amplifiers?
A. The main features are:
- automatic gain control for both transmit/ receive modes,
- the very low noise level.
AGC gives a possibility to keep of outgoing signal at the antenna at a constant level irrespective of the cable losses. The input signal at the radiounit is also kept at constant level independently of the cable losses. It lets simplify designing and tuning the whole system and increase stability. It's especially important in the regions where the temperature of environment changes in a considerable range. The low noise level increases the receiving sensitivity of the system.

6.
Q. What are advantages of an active antenna with a built-in amplifier?
A. The antenna with a built-in amplifier has the advantages as compared with the antenna and amplifier mounted separately:
- the better match of antenna and amplifier feeders,
- losses and the noise level of this system are less and as a consequence the system sensibility is higher,
- the mounting is easier.

7.
Q. What parameters characterize the performance of an amplifier?
A. The main features of an bi-directional antenna amplifier are:
- outgoing signal level,
- transmit gain,
- receive gain,
- noise level.
Also very important features are:
- a range of the operating temperature,
- automatic gain control,
- a built-in filter,
- a built-in lighting protector.

8.
Q. How to choose the right outgoing power of an amplifier?
A. The higher the outgoing power of the amplifier, the longer the distance between the radiounits. Usually the amplifiers for RadioEthernet equipment have rated outgoing power 100, 500 and 1000 mWatt (for comparison: the outgoing power of WaveLan is 30 mW, of ARLAN is from 5 to 100 mW).
For each particular link the chosen outgoing power of the amplifier depends on the length of the radiolink, the type of the antennas, and also on the maximum outgoing power level allowed in the particular country according to its regulation rules.
Also very important to take into account the following. The precise match of the signal from the radiounit, cable losses and amplifier transmit gain is required if you use an amplifier without AGC. Otherwise either the outgoing power will be lower than it's required (if the signal is low) or the amplifier will perform in overload mode with linear and phase distortions (if the signal level is high), which can cause reducing speed. The amplifier with AGC is not so sensitive to the match of antenna feeder and keeps its parameters constant in all range of operating temperature +/-50C. Using an amplifier with AGC let use the cheaper type of cable.

9.
Q. How to choose the correct level of amplifier gain?
A. It's quite a complicated problem. You can find more details and method how to estimate it in "Calculation Page" section at WISTEC site. But the best and easiest way is to use amplifiers with automatic gain control.

10.
Q. How the noise level affects the performance of the system?
A. The lower the noise level is the higher the sensitivity of the system and more stable performance at the maximum rate.