WSM

Summing and Multiplexing Unit

(WSM)
The Summing and Multiplexing Unit (WSM) routes and distributes digital bit
streams between Transmitter and Receiver (WTR) and Signal Processor Units
(WSP).

Up to 3 WSM units can be installed in a single cabinet, one per each BB section.
In downlink direction, the unit receives spreaded downlink signals from six
WSPs. In the case of softer handover, it receives signals also from up to two
neighbouring sectors. After the final summing, the unit forwards the composite
signals to the WTR unit for transmission.


In uplink direction, the WSM unit distributes the received signals from its own
sector and from its two neighbouring sectors to all six WSPs.
The Application Manager Unit (WAM) controls the WSM and the System Clock
Unit (WSC) provides the WSM clock signal.


The WSM unit distributes signals between WTRs and WSPs. The TX block
receives signals from the WSP unit and forwards them to the WTRs. The RX
block receives signals from the WTR unit and forwards them to the WSPs.


The WSC unit provides the reference clock BRCLK 61.44MHz and SFCLK for
the WSM unit which sends them forward to the WAM unit.



The WAM unit detects the WSM via SCI-bus by reading the serial and version
numbers and the ID from EEPROM. The WAM also uploads the configuration
data for the WSM units.


The WSM is equipped with a LED to indicate different operation conditions (see
chapter 3).
The hot insert of the WSM unit is possible. If any of the WSM, WSP or WTR
units is inserted (hot insert) or removed from the BTS, the WAM updates that to
the WSM units.
The WSM unit can be reset remotely via SCI-bus.



The WSM unit consists of the following functional blocks:
• TX block
• RX block
• SCI bus (I 2 C) little 2 obove I