Anatomy of Contemporary GSM Cellphone Hardware
Anatomy of contemporary GSM cellphone hardware
Harald Welte April 16, 2010
Abstract Billions of cell phones are being used every day by an almost equally large number of users. The majority of those phones are built according to the GSM protocol specifications and interoperate with GSM networks of hundreds of carriers. Despite being an openly published international standard, the architecture of GSM networks and its associated protocols are only known to a relatively small group of R&D engineers. Even less public information exists about the hardware architecture of the actual mobile phones themselves, at least as far as it relates to that part of the phone implementing the GSM protocols and facilitating access to the public GSM networks. This paper is an attempt to serve as an introductory text into the hardware architecture of contemporary GSM mobile phone hardware anatomy. It is intended to widen the technical background on mobile phones within the IT community.
1
Foreword
This document is the result of my personal research on mobile phone hardware and system-level software throughout the last six years. Despite my past work for Openmoko Inc., I have never been professionally involved in any aspect of the actual GSM related hardware of any phone. Nevertheless I have the feeling that in the wider information technology industry, I am part of a very, very small group of people who actually understand mobile phones down to the lowest layer. I hope it is useful for any systems level engineer with an interest in understanding more about how mobile phone hardware actually works. There are no guarantees for accuracy or correctness of any part of the document. I happily receive your feedback and corrections.
2
Is your phone smart or does it have features?
Initially, for the first couple of years, GSM cell phones were actual phones with very little additional functionality. They provided everything that was required for voice calls, as well as SIM
Harald Welte April 16, 2010
Abstract Billions of cell phones are being used every day by an almost equally large number of users. The majority of those phones are built according to the GSM protocol specifications and interoperate with GSM networks of hundreds of carriers. Despite being an openly published international standard, the architecture of GSM networks and its associated protocols are only known to a relatively small group of R&D engineers. Even less public information exists about the hardware architecture of the actual mobile phones themselves, at least as far as it relates to that part of the phone implementing the GSM protocols and facilitating access to the public GSM networks. This paper is an attempt to serve as an introductory text into the hardware architecture of contemporary GSM mobile phone hardware anatomy. It is intended to widen the technical background on mobile phones within the IT community.
1
Foreword
This document is the result of my personal research on mobile phone hardware and system-level software throughout the last six years. Despite my past work for Openmoko Inc., I have never been professionally involved in any aspect of the actual GSM related hardware of any phone. Nevertheless I have the feeling that in the wider information technology industry, I am part of a very, very small group of people who actually understand mobile phones down to the lowest layer. I hope it is useful for any systems level engineer with an interest in understanding more about how mobile phone hardware actually works. There are no guarantees for accuracy or correctness of any part of the document. I happily receive your feedback and corrections.
2
Is your phone smart or does it have features?
Initially, for the first couple of years, GSM cell phones were actual phones with very little additional functionality. They provided everything that was required for voice calls, as well as SIM