**1. Introduction**

338 Wireless Communications and Networks – Recent Advances

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ISBN 978-0-471-44967-6, New York, USA.

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The complexity of the communication systems and protocols is increasing constantly, while the communication products' time-to-market is becoming shorter. Afterthoughts communication system redesign due to lack of performance is financially and time expensive, and it is unacceptable. This book chapter proposes a method for improving the telecommunication systems, by means of enhancement the performance of the protocols they rely on. The proposed engineering of communication systems is based on a formal method and it provides an early-phase performance evaluation of the underlying communication protocols. The methodology is illustrated through a hands-on case study conducted on an existing wireless communication system.

The development and standardization of new telecommunication and information technologies is a rather complex process which requires a comprehensive framework (Sherif, 2001). The result of such a process is a new agreement that should satisfy all of the involved parties, such as: vendors, providers, and most importantly service users. To create a comprehensive communication standard and consequently a reliable communication system, many strategic and tactical issues need to be considered. The missing question is how to produce a standard that specifies a protocol or a system with high performance. The lack of performance issue might be a major cause for pitfall of entire communication systems. Most of the problems result from poor protocol specifications or from its enormous complexity. Furthermore, the design errors caused by the short and intensive creation period usually remain hidden until the testing and implementation phases of the communication product development. Fixing the problems after product's delivery for communication software and hardware increases the cost of the product by factor of 100 to 1000 compared to the fixing of the problem in the analysis phase.

High performance communication protocols which are untainted of functional errors are crucial in the telecommunications sector where product expectation cycle is denominated in decades instead of years. In order to develop such a protocol, two aspects should be fulfilled: introduction of formal methods during the specification process and integration of the performance-related activities in the early phases of the communication system specification and development. The former one is already taking place as a result of the need for clarity and accuracy in the telecommunication standards, but the last aspect is commonly avoided or even neglected.

The formal methods are always advised for the development process when early functional error detection is needed. Formal Descriptive Techniques (FDTs) provide corrective actions in the more abstract phases by introducing formal syntax and what is more important, precise semantics. In combination with the computer-aided software engineering, FDTs offer a delivery of better communication protocols and systems, sooner. The introduction of the FDTs has brought correctness and reliability into the protocol development, which has been recognized long time ago (Wing, 1990), (Hall, 1990). Today there are many formal languages and tools used in the protocol development process: Specification and Description Language-SDL (SDL, 2011), Simple ProMeLa Interpreter (Spin), Estelle (Estelle, 1989), Language of Temporal Ordering Specifications (LOTOS, 2000), Petri Nets (Petri, 1996), Uppaal (Larsen, 1997), Message Sequence Chart (MCS, 2001) and Unified Modelling Language (Booch, 2000). Among them, SDL has achieved widespread success because of its friendly graphical notation, its standardization by the International Telecommunication Union (ITU-T) as the major specification tool for standards and protocols, and because of its support for other popular notations such as ASN.1 (ASN.1, 1993), MSC and TTCN (TTCN, 2006). The effectiveness of SDL and its ability to develop unambiguous protocols have won it a widespread popularity and have led the standardization institutes, such as ETSI (European Telecommunications Standards Institute) (ETSI), 3GPP (Third Generation Partnership Project) (3GPP) and IEEE (The Institute of Electrical and Electronics Engineers) (IEEE) to include SDL diagrams in their protocols specification. SDL also provides powerful analysis of communication protocols, along with design, comprehensive modelling, protocol prototyping, exhaustive validation and verification, and all that by a user-friendly graphical notation. Along with Message Sequence Chart (MSC) description language, SDL is the most widely used FDT not only in the communication protocol specification area, but also in the industry systems engineering domain. Because of the previously stated advantages, SDL was selected as a protocol description method for the purpose of this chapter's analysis.

The aim of this chapter is to emphasize the importance of conducting an early performance evaluation of the communication protocols and systems, and to suggest an appropriate solution for carrying out such an activity. Performance evaluation activity denotes the actions to evaluate the protocol under development regarding its performance. This process can take place in different phases of the development, and can be based on modelling or measurements. If the designer can control the performance of the product, rather than just manage its functionality, the result will be a much superior creation. This problem is treated in this chapter through a tangible wireless communication protocol example.

The chapter is organized as follows. Section 2 presents the most relevant and most recent work which relates to the target topic of the chapter. In Section 3, the proposed and used methodology is elaborated in details. This methodology is demonstrated in Section 4, where a real engineering problem is provided, involving an IEEE 802.16 wireless communication protocol. Section 5 contains the conclusions of the chapter.
