TABLE OF CONTENTS Wireless communications has enabled a variety of services starting from Voice continuing to Data and now to Multimedia. We are about to enter an era that has never been seen before as cell phones, laptops, cameras, personal digital assistants (PDAs), and televisions all converge into a potentially single consumer electronic device.
Since the conception of cellular communications, we have learned to enjoy the freedom that comes with mobility. The first generation cellular system was AMPS, Analog Mobile Phone System. It used the traditional frequency modulation (FM) scheme to enable communication among voice users. A user s speech was directly converted by an FM modulator to be sent over the wireless medium. This system had voice quality issues, in particular at the cell fringe, and suffered from low user capacity [1 3].
Here comes Digital! The second generation (2G) cellular systems used digital modulation schemes such as ?/4-Shifted Differential Quaternary Phase Shift Keying ( ?/4-DQPSK) and Gaussian Filtered Minimum Shift Keying (GMSK). The speech was digitized, error protected, and transmitted in a specific time, frequency, or code domain. These advances helped improve voice quality and user capacity. These 2G systems are North American TDMA System (IS-136), Group Special Mobile (GSM), North American Spread Spectrum System (IS-95), and Japan Digital Cellular (JDC), to name a few, with GSM being the de facto Global Standard, in other words, the more widely used system throughout the world.
These 2G cellular systems suffered not only from low user capacity, but also from low...
