Acquisition and mobility operational scenarios in the MUOS system

The Mobile User Objective System (MUOS) is largely based on 3^rd Generation Partnership Project (3GPP) standards, however, these standards are intended for terrestrial mobile communications networks. As a result of incorporating geosynchronous satellites into the design (e.g., extended propagation delays, power, cell size), modifications to the 3GPP procedures, such as moving control of cell selection, are needed. The operational scenarios related to acquisition and mobility are dictated by the operational mode of a MUOS radio - point-to-point, group, or emissions control (EMCON) - as well as whether a MUOS service (e.g., `voice call´) is currently active. This paper describes the operational implications of mobility and acquisition on MUOS radios, and the design challenges that are met to satisfy customer anticipated levels of service. In order to support the three operational modes with common procedures, the MUOS design for acquisition and mobility has moved control of the mobility event from the radio (standard 3GPP operation) to the ground segment (GS); resulting in message and data flow modifications specific to MUOS. Additionally, whereas 3GPP operation does not notify users of a mobility event, the MUOS does provide that knowledge for the user involved in a mobility event as well as other users impacted (e.g., the talker in a group call informs the listeners of its mobility event).