Page 75 - From GMS to LTE

Global System for Mobile Communications (GSM) 61

Flash Camera
memory SDRAM module
Cellular
analog Front
parts Baseband ARM camera
processor CPU

ARM
Wifi GPU CPU
Bluetooth Battery logic Battery
FM Radio
Image Video Microphone
processor en/decoder Speech codecs Loudspeaker
Motion USB transceiver USB Port
sensor Shared Memory Controller
Timers, Interrupts Keypad ctrl. Keypad

GPS Secure ROM Analog-and
SoC energy
management
SD card TV Out TFT / OLED Touch chip
reader (HDMI) display screen ctrl.

Figure 1.48 Architecture of a modern smartphone.

The baseband processor is responsible for communication with a mobile network
and supports not only GSM but also UMTS and LTE. A few analog components can-
not be included on the SoC because of their size and function and are thus shown
separately in the figure.
The operating system for the user interface, such as Android or iOS, is executed on
the application processor, which usually consists of several ARM processor cores.
These ARM CPUs have an instruction set similar to that of the ARM processors of
the voice‐centric GSM phones discussed earlier. Owing to their higher complexity
and higher clock rates, their power consumption is much higher. The baseband pro-
cessor and application processor operate independently of each other and communi-
cate with each other over a fast serial interface. This is also the case if both units are
contained in a single SoC. Other important building blocks usually contained in an
SoC are a dedicated Graphics Processing Unit (GPU) and a number of additional
supporting functions for memory management, timers, interrupts and dedicated
processing units allowing the external camera module to quickly process images
taken by the user for the operating system. Memory chips are usually still physically
separate from the SoC. And finally, additional external elements such as a camera
module on the back, another one on the front, Wi‐Fi, Bluetooth and FM radio chips,
as well as GPS, SD card readers, TV‐Out, display and touchscreen are also part of a
modern smartphone.