A communication system includes a reference station and a mobile station. The reference station is operable to: receive GPS signals; generate GPS assisting data from the received GPS signals; receive SBAS signals; obtain SBAS data from the received SBAS signals; combine the GPS assisting data and the SBAS data to produce combined GPS data; and transmit the combined GPS data via a terrestrial wireless communication. The mobile station is operable to: receive the GPS signals; receive the combined GPS data via the terrestrial wireless communication; and generate positioning data from the mobile received GPS signals and the combined GPS data.