 higher-orbiting sat- ellite, SO you can direct their transmissions into a user's handheld. Also, LEOs offer greatly increased network capacity overall on a global basis. LEOs orbit at about 400 to 1,000 miles (640 to 1,600 km). LEOs can be used with smaller terminals than can the other satellites because they are much closer to the earth (40 times closer). But, again, because they are closer, you need many more LEOs than other satellites to get the same coverage (about 20 times more LEOs than GEOs and 5 times more LEOs than MEOs). A user must always be able to see at least one LEO satellite that is well clear of the horizon. As mentioned earlier, the very first satellites rotated around the earth SO fast that we couldn't use them for communications. But LEO satellite platforms include switching, SO as a LEO satellite begins to go out of view, a call is switched-that is, handed over-to the next satellite coming in. This works very much like the cellu- lar system, where a caller is handed off to different frequencies during a conversa- tion while transiting between cells. Of course, a benefit of being lower in the sky means that the delay with LEOs is reduced-to only about 0.05 seconds-and this makes LEOs very appealing for interactive services. The key applications for LEOs are support for mobile voice, low-speed data, and high-speed data. There are three categories of LEOs, and each category is opti- mized for certain applications: Little LEOs-Little LEOs offer 2.4Kbps to 300Kbps and operate in the 800MHz range. They are ideal for delivering messaging, paging, and vehicle location services. Big LEOs-Big LEOs offer 2.4Kbps to 9.6Kbps and operate in the 2GHz range. They have rather low data rates and are largely designed to provide voice services to areas that aren't currently served by any form of terrestrial or cellular architecture. Broadband LEOs-Broadband LEOs offer 16Kbps to 155Mbps. They oper- ate in the Ka-band, at 20GHz to 30GHz, and they support data and multi- media files at up to 155Mbps. Applications 