Baseband Processing - Huawei iSiteC BTS3601C-800 User Manual

User Manual
iSiteC BTS3601C CDMA Base Station
VIII. Power control
Coordinating with the MS and BSC, BTS provides various power control mechanisms
(as detailed in Section 3.4.1 Power Control).

3.3 Baseband Processing

Baseband processing performs physical layer functions on Um interface, and
processes baseband data of all full-duplex channels in CDMA system.
In the forward direction (transmitting direction), baseband processing fulfills channel
coding, rate adaptation, interleaving, spreading spectrum and modulation. In the
reverse direction (receiving direction), it fulfills multi-path signaling demodulation,
de-interleaving, channel decoding and information bit extraction.
For different Radio Configuration (RC), baseband processing is different. But basically
it can be summarized into the following procedures:
I. Forward channel baseband processing
In CDMA forward channel, the baseband processing of one traffic channel includes
channel coding, rate adaptation, block interleaving, long code scrambling, power
control bit insertion, Walsh code spreading spectrum, signal modulation and
baseband filtering, as shown in Figure 3-5.
Rate Rate
Channel Channel
adaptation adaptation
coding coding
Channel coding
l
CDMA system uses Convolutional code and Turbo code for channel coding. Its
function is error correction. Convolutional code is used for ordinary speech service
and Turbo code for high-speed data service.
Rate adaptation
l
Since the system supports frames of different rates. The frame rates after channel
coding are different. Rates should be adapted to ensure that the rate of frames meets
the requirement before entering the interleaver. In CDMA system, rate adaptation is
realized by symbol repetition and code puncturing.
Block interleaving
l
The purpose of interleaving is to resist fast fade in the radio channel environment.
Long code scrambling
l
Long code Long code
Block Block
scrambling scrambling
interleave interleave
Figure 3-5 Baseband processing in forward channel
3-9
Chapter 3 System Function
Walsh code Walsh code
QPSK QPSK
spreading spreading
modulation modulation
spectrum spectrum
System Description
Baseband Baseband
filtering filtering