4.11 Active DAS Data
Active DAS systems consist to a large extent of amplifiers and repeater/BDA systems; therefore it is important for the RF planner to understand the basic data of these system components. Many of these standard metrics are used to benchmark the radio performance of different manufacturers and systems. Make sure that the data you are comparing all use the same standard benchmark reference.
The amplifiers used in active DAS, repeaters and BDAs have to be very linear, in order not to distort the signal and degrade the modulation. The more complex the modulation used, the higher demands are on linearity and performance. This is very important for the higher coding schemes on EDGE, UMTS and especially HSPA. Be careful when selecting equipment used for indoor DAS systems, since performance of the system is often directly related to the price. The most basic parameters and merits are described in this section.
4.11.1 Gain and Delay
Gain is the amplification of the system (as shown in Figure 4.41), the difference between input signal and output signal power. The power of the output signal is:
Gain is typically stated in dB. For a system with a factor 2 power gain, for example, 1 W input (+30 dBm) will lead to 2 W output.
Power gain in dB can be calculated as:
For voltage, gain factors can be converted to ...