A cell phone's roaming feature allows the user to get service when traveling beyond the boundaries of his/her service provider. Wireless service providers make approximately 30% of their operating profit from roaming. But despite being a major source of income, roaming suffers from a number of technological problems in the handoff between networks. Signal strength is wildly variable, calls are frequently dropped, and quality of service is poor. Based upon training courses the author teaches at Agilent and Hewlett-Packard, this is the first book to give communications engineers the know-how to faultlessly design and manage roaming services.