Try to find some of these books.
Gsm System Engineering (Artech House Mobile Communications Series) (Hardcover)
An Introduction to Gsm (The Artech House Mobile Communications) (Hardcover)
GSM Switching, Services, and Protocols (Hardcover)
GSM Networks: Protocols, Terminology and Implementation (Artech House Mobile Communications Library.) (Hardcover)
Gsm and Personal Communications Handbook (Artech House Mobile Communications Library) (Hardcover)
The GSM System for Mobile Communications (Hardcover)
Introduction to GSM: Physical Channels, Logical Channels, Network, and Operation (Paperback)
Mobile Messaging Technologies and Services: SMS, EMS and MMS (Hardcover)
Cellular Radio Performance Engineering (Artech House Mobile Communications Library) (Hardcover
Encyclopedia of Energy Engineering and Technology – 3 Volume Set (Part a & B, Vol 3) (Hardcover)
UMTS Network Planning, Optimization, and Inter-Operation with GSM (Hardcover)
Practical Radio Resource Management in Wireless Systems (Artech House Universal Personal Communications Series.) (Hardcover)
Handbook of Optimization in Telecommunications (Hardcover)
GSM-Network Switching Subsystem Engineering: The NSS protocol architecture
End-to-End Quality of Service over Cellular Networks: Data Services Performance Optimization in 2G/3G (Hardcover)
Performance Enhancements in a Frequency Hopping GSM Network (Hardcover)
GSM-Base Station Subsystem Engineering (Paperback)
Networking Infrastructure for Pervasive Computing: Enabling Technologies and Systems (Hardcover)