Page 74 - From GMS to LTE

60 From GSM to LTE-Advanced Pro and 5G

DSP

RISC
Signal Inter- Channel Speech
encoding Cipherer leaver coder encoder

Signal De- De-inter- Channel Speech
decoding cipherer leaver decoder decoder

GSM/GRPS User External
MMI
Control programs interfaces Serial
Operating system USB
Bluetooth
IrDA
Figure 1.47 Overview of RISC and DSP functionalities.

Section 1.7.3). As the DSP is aware of the composition of the training sequence of a
frame, the DSP can calculate a filter that is then used to decode the data part of the
burst. This increases the probability that the data can be correctly reconstructed.
Figure 1.47 shows the respective tasks that are performed by the RISC processor
and the DSP processor. If the transmission chain for a voice signal is compared
between the mobile device and the network, it can be seen that the TRAU mostly
performs the task of a DSP unit in the mobile device. All other tasks such as channel
coding are performed by the BTS, which is thus the counterpart of the RISC CPU of
the mobile device.
As hundreds of millions of mobile devices are sold every year, there is a great variety
of chipsets available on the market. The chipset is in many cases not designed by the
manufacturer of the mobile device. Chipset manufacturers that are not developing their
own mobile devices include, for example, Qualcomm and Mediatek.

1.9.2 Architecture of a Smartphone
Simple GSM voice phones usually have one processor that handles both the modem
functionality and the operating system for the user interface. In smartphones, these
tasks are performed by independent processors. This has become necessary as each
function has become much more complex over time, and the processor architecture
required by each function has developed in different directions. In addition, smart-
phones include many new functionalities that require significant and specialized pro-
cessing capabilities. Figure 1.48 gives an overview of the typical function blocks of a
modern smartphone. Owing to increasing miniaturization, most or even all of the func-
tions shown are included in a single chip. Such a combination is often also referred to as
a System on a Chip (SoC).