In the past 20 years, mobility has grown to become a salient feature of many communication systems. The demand for mobility is expected to be even more indispensable in the future as end users require greater amounts of data along with their desire for ubiquitous coverage as they move about. Recently, next generation cellular architectures have started providing data communication in the broadband range while preserving the mobile nature of the network. Satellite data communication systems have, however, mostly stayed within the fixed or transportable arena. The capabilities of existing and near-future satellite systems vary substantially by factors such as the types of end users and applications supported, satellite spot beam capabilities, and bandwidths supported.This paper looks at the capability of mobile communications in a Geosynchronous Regenerative Satellite Mesh (RSM) System.In particular, the architecture and design of mobility and Communicationson-the-move (COTM) will be detailedfor the SPACEWAY system, which falls under the RSM architecture. The mobility concept is distributed across the system, involving the space, terminal, and ground segments. Additionally, mobility has been designed to be as automated as possible and to offer high performance at broadband data rates. The concepts and designs presented here can also be considered as a blueprint for future generation satellite systems that would need to support communications-onthe-move. INTRODUCTION The demand for mobile communications has increased exponentially in the last several years, both for commercial and military environments. Much of this has been driven by the roll-out of terrestrial cellular networks throughout the world, including the US [1]. The range of features and their convenience has made mobile phones (terminals) nearly indispensable for many segments of the population. Additionally, support for new features, including transmission of packetized voice and video data, has opened up even more demand for robust and data intensive applications.The generation of mobile satellite commercial systems pioneered over a decade ago primarily focused on voice services and low data bandwidth applications. Iridium, Globalstar, ICO and Thuraya are typical examples of the satellite communication systems of that era. These systems typically relied on omni-directional antennae with "brick-sized" form factors for the terminals. However, current and future satellite commercial systems need to offer more compelling features such as higher bandwidth, guaranteed quality, and high-end performance -all with user mobility. To improve signal gain, directional antennae are often used to achieve the desired higher bandwidth demanded by current and future applications. Not only does the higher bandwidth and performance allow for a credible product in the satellite marketplace, it also offers competition for traditional land-based carrier networks.In the military, mobile communications also has a rich history as an important aspect to tactical missions. In p...