Preface

Raison d'être

Mobile telecommunications has left the POTS (plain old telephone system) far behind. Today, one in every three has a mobile connection. In parts of Europe and Asia, close to 80 percent of the population carries a mobile—developed countries are close to getting saturated. The situation in developing countries will be encouragingly similar in a few years—countries like China and India are experiencing exciting growth opportunities for the mobile telecommunication industry. Given the scenario, certain trends are evident: As the subscriber base gets saturated, growth will come from new services and not new subscribers. For example: multi-media services that provide integration of voice and data will become critical. Moreover, the bandwidth limitation of existing wireless networks will force operators to deploy next generation networks. This will result in end-user benefit—users can enjoy bandwidth-intensive multimedia applications that are being developed but limited by data carrying capacities of mobile networks.

The pressing need for greater bandwidth and service capabilities led International Telecommunications Union – Telecommunication Standardization (ITU-T) to form a vision of Third Generation (3G) networks. In sync with this development our book on Third Generation (3G) networks (2004) was very well received. Even though 2G and 2.5 in comparison to 3G are older technologies, the following, current, strong outlook for these two technologies has necessitated development of books on 2G and 2.5G mobile networks:

 

  1. GSM (Global System for Mobile Communications) is the most popular Second Generation (2G) network for wireless voice and low data rate applications, such as SMS (Short Message Service). With an existing subscriber base of two billion, large parts of the world, particularly China and India, hold a very strong growth potential for 2G GSM and 2.5G GPRS networks in the coming five years.  As of mid-2006, 2G GSM networks accounted for more than 75 percent of the mobile telecommunications market—3G UMTS networks even after five years are no where even near. Even for services that require high bandwidth, simpler options, such as GPRS and EDGE are preferred.

 

  1. Technological improvements have resulted in 2G and 2.5G networks that are capable of higher data rates. Among these are: circuit-switching techniques, such as High-Speed Circuit Switched Data (HSCSD), and packet-multiplexing techniques including General Packet Radio Services (GPRS) and Enhanced Data Rates for Global Evolution (EDGE).

 

  1. 3G UMTS networks are backward compatible with 2G GSM and 2.5G GPRS networks. Over the next few years, GSM and GPRS operators would move towards UMTS. During the transition, which is likely to span many years, they will have to support GSM and GPRS. GSM-3G and GPRS-3G integration will be important during this time, in which multi-mode handsets will appear. This makes it imperative to know about GSM and GPRS.

 

  1. Several mobile telecommunication companies around the world are still involved in the development of GSM and GPRS products. And this trend is projected for another five to seven years, until 2015.

 

To cover the journey from 2G to 2.5G to 3G we present a series of three books (Ref. Fig. P.1). As mentioned earlier the first book on Third Generation (3G) networks was published in 2004. The second book on 2G networks was published in late 2006. This book completes the trilogy of books on the three generation of mobile cellular technologies.

 

 

 


Figure P.1: Three book series on wireless technologies

 


About the book

 

This book presents GPRS concepts in a simple, yet effective manner. All the important topics have been given adequate attention. The overall idea is to first provide introduction material and then take the discussion from the air interface to the core network.

The book starts with a detailed overview of GSM in Chapter 1. This chapter essentially summarizes the contents of the book 2G Mobile Networks. Readers well versed with GSM may skip this chapter. Nonetheless, it is recommended to go through this chapter as GPRS uses GSM as its underlying foundation.

The GPRS discussion starts with Chapter 2 that describes the GPRS network architecture. All the network entities and the interfaces between them are described in this chapter. A brief description of the relevant protocols for the interfaces is also presented.

The GPRS Air Interface is described in Chapter 3. This chapter covers the GPRS logical channels, channel organization and various schemes of channel coding (CS1 to CS4). The chapter also covers important air interface concepts like timing advance and power control.

The twin protocols of Medium Access Control (MAC) and Radio Link Control (RLC) are described in Chapter 4 and Chapter 5 respectively. The main function of MAC layer is establishment and release of Temporary Block Flow (TBF) which are described in detail in Chapter 4. Other important functions of MAC including System Information Broadcast, Paging and Cell Re-selection are also covered in this chapter. The next chapter on RLC primarily deals with the block structure of both control blocks and data blocks. The RLC operations for acknowledgement and reliable delivery are also discussed.

The core network procedures of GPRS Mobility Management (GMM) and Session Management (SM) are covered in Chapter 6 and Chapter 7 respectively. In particular, chapter 6 covers important GMM procedures including the Attach/Detach, Routing Area Update, Authentication, and Combined Attach/Routing Area Update procedures. Chapter 7 covers the SM procedures including PDP Context Management procedures including activation, modification and deactivation of PDP Context.

Chapter 8 provides a summarized view of the GPRS user plane. The role of key user-plane protocols including Subnetwork Dependent Convergence Protocol (SNDCP), Logical Link Control (LLC), BSS GPRS Protocol (BSSGP), Network Service (NS) and GPRS Tunelling Protocol for User Plan (GTP-U) are covered in this chapter. Other user plane protocols like RLC/MAC are not discussed as they are already covered earlier.

Chapter 9 is the concluding chapter of the book that describes the enhancements done in GPRS to support Enhanced Data Rates for Global Evolution (EDGE). The new modulation and coding schemes for EDGE (MCS 1 to 9) are described in this chapter. Important changes in the RLC/MAC block structure and TBF establishment/release for EDGE are also described in this chapter.

 

Acknowledgements

First off, we thank our organization Aricent, Gurgaon, India where we have our professional career. The organization has provided us a solid foundation to write technical books on different technologies in communication networks.

We remain obligated to our senior colleagues at Aricent, N. Mohanrangan, Prabhat Kumar Sahoo, Sudatta Kar, Rajinder Kumar, Ravikanth Pasumarthy, Manish Gupta and Dhrubajyoti Das for their support and guidance.

We would also like to thank all personnel at Nokia Siemens Networks (NSN) who were a part of the collaborative software project on GSM/GPRS/EDGE. Special thanks are due to Juha Matturi, Heikki Herva, William Brockington, Andy Tabor, Rade Luburic and Eric Jones for sharing their expertise that helped us become proficient with the three wireless technologies.

Our acknowledgements would not be complete without appreciating our families for the time we could not spend with them while finalizing the book.

We also thank all our readers who time and again have provided valuable feedback and motivated us to write new and better books.

Apart from above, individually, we would like to acknowledge specific persons/institutions.

Both Sumit and Nishit would thank their alma mater and all its professors for providing them a strong engineering platform. While Sumit is an alumnus of Indian Institute of Technology (IIT) Kharagpur, Nishit completed his graduation from the prestigious IIT Delhi.

Priyanka would thank good fortune and the almighty for being present in the right place at the right time. As she puts it: “Luck is when opportunity meets preparation”. In particular, she would like to thank Sumit and Nishit for showing faith in her capabilities and providing her with this opportunity of being part of the authoring team. She expresses special gratitude to Sumit for his tireless mentoring and patience as he guided her through this process of book-authoring. She owes her preparation, not just for this book, but for the whole life to her parents without whom she could not justify any opportunity. She would also like to thank her sister and husband for their unconditional love, support and patience. Last, but not the least, she would like to thank all colleagues at Aricent for making each day a learning experience.

 

Website

To supplement the material in this book a website has been created: http://gprsbook.tripod.com. Readers are strongly encouraged to access this site, where they will find:

 

Suggestions

We solicit reader comments, feedback and criticism that will help us add more value to the subsequent editions of this book. Please write to us at: nwbook@lycos.com.

 

SUMIT KASERA

NISHIT NARANG

A. P. PRIYANKA