SIEMENS BSS

1. A30808-X3247-L14-2-7618 61
Information
Base Station System
Technical Description (TED:BSS)
BS-240/241
4.2 Receiving Paths
4.2.1 Antenna diversity techniques
Basically, there are two different diversity combining techniques:
• Switched Combining
• Maximum Ratio Combining
Switched Combining
Switched Combining simply selects one of the two receiver paths according to a given
quality criterion, such as maximum receiver gain.
Thus, in the case of correlated signals from receiver paths (and comparable gain),
Switched Combining cannot improve receiver performance. A decision is usually made
for one full Um burst.
Maximum Ratio Combining
Maximum Ratio Combining provides the best combination of all available informations
from both receiver paths.
4.2.1.1 Antenna System Modules
Different TX, RX and TX/RX antennas are provided which are connected to the
combining modules in order to serve cells with different carrier numbers. These
combining modules have to provide the necessary performance by using the following
methods:
– Antenna Combining
to feed several transmitter outputs to the TX antenna
– Multicoupling
for splitting the RX signal for several receiver inputs
– Duplexing
both Antenna Combining and Multicoupling methods are used in order to connect
the TX- and the RX-path to one antenna
The technology of the new BTSEs knows TX Combiner (FICOM), TX and RX Combiner
(DUAMCO), High Power Duplexer (HPDU) and RX Multicoupler (DIAMCO). DUAMCO
and DIAMCO use a Low Noise Amplifier (LNA) in the RX path, which can be set to
different gain to establish the various configurations of the BS-240/241. Additionally, the
DUAMCO and DIAMCO have power supply and supervision functionality for a Tower
Mounted Amplifier.
Antenna diversity is a second receive path to improve the receive quality and the grade
of service. It is important that the diversity path is configured in the same way as the
normal path, that means either, with or without TMA. Inside the Rack, it's possible that
one RX path is realized with a DUAMCO and the other with a DIAMCO or cascaded
DIAMCOs.
A solution of antenna combining and multicoupling is the configuration with two
TX-/RX-antennas and two duplex combining modules. Both antennas belong to the
same cell. One antenna is used for transmission and reception, the other for transmis-
sion and diversity reception. Therefore exist two transmit paths, one normal receive path
and one diversity receive path. The combining of the two transmit paths happens 'on air'.
Supervision of the two antennas will be done separately for each one.