32
A30808-X3247-L14-2-7618
Technical Description (TED:BSS)
BS-240/241
Information
Base Station System
frames and sent to TRAU. Signalling data (e.g., FACCH) are processed by layer 3 of
BTS software
–
receives the TRAU frames or signalling data. The TRAU frames are unformatted and
sent to the coder. After encoding, data are ciphered. Now, baseband hopping takes
place. Training sequence is inserted to the data received via the hopping bus. These
bursts are sent to the GMSK modulator. This stream is converted into an analogue
baseband signal leaving the SIPRO
–
parallel to the data stream the PLLs for synthesizer hopping are programmed.
Therefore, both for uplink and downlink, a data stream to the PLLs is generated.
Fig. 3.7
Principal Data Flow on SIPRO
Power Supply Unit (PSU)
The PSU is the DC/DC converter for the CU for all applications. The PSU generates the
vo26/28V, +6V (only GSM 1800, GSM 1900), +12V, +5.3V and -5.3V for the
analogue circuitry and +3.35V for the digital circuitry from a -48V primary input voltage.
The PSU is mechanically incorporated in the CU.
3.3
EDGE Carrier Unit
The ECU unit is a modified CU using the same interfaces as CU but supporting EDGE
functionality in uplink and downlink. In downlink direction, the signalling and traffic data
are received from the Core and converted into GMSK or EDGE modulated signal, which
is amplified to the desired power level.
With thef EDGE it is possible to mix EDGE and non EDGE timeslots on the same carrier.
The ECU carries two independent receivers (normal and diversity channel) to provide
the antenna diversity function. In uplink direction, the received signal is converted to
IF-band. The IF-band is converted to a digital GMSK/8PSK-signal.
The 8PSK is a linear modulation, where three consecutive bits are mapped to symbol
as shown in
Uplink
Downlink
A
D
A
D
Hopping PLL
Hopping PLL
Control
Central
diversity
2
2
Digital Down-
Conversion
Equalization
Deciphering
Decoding
TRAU Frame
Formatting
Signalling
TRAU Frame
Deformatting
Signalling
Coding
Ciphering
GMSK
Modulation
