| The wireless arena has been experiencing exponential growth in the past decade. We have seen great advances in network infrastructures, growing availability of wireless applications, and the emergence of omnipresent wireless devices such as portable or handheld computers, PDAs, and cell phones, all getting more powerful in their capabilities. These devices are now playing an ever-increasingly important role in our lives. To mention only a few examples, mobile users can rely on their cellular phone to check e-mail and browse the Internet; travelers with portable computers can surf the internet from airports, railway stations, cafes, and other public locations; tourists can use GPS terminals installed inside rental cars to view driving maps and locate tourist attractions; files or other information can be exchanged by connecting portable computers via wireless LANs while attending conferences; and at home, a family can synchronize data and transfer files between portable devices and desktops. |