The need for ubiquitous coverage for many of the proposed 5G use cases – in particular the Connected Car – has necessitated a plan to include other connectivity solutions such as WiFi and satellite communications in future hybrid networks, in order to ensure that there will be no holes in the 5G coverage map. The low earth orbit (LEO) satellites that are being developed for the space segment are of necessity very different from the high-cost, high-reliability geostationary (GEO) satellites that have traditionally been used for satcomms, or even the medium earth orbit (MEO) craft that make up the GPS, Glonass and Galileo constellations used for satellite navigation. One of the key challenges for the new satellites is the need to use commercial-off-the-shelf (COTS) components rather than radiation-hardened, space-qualified components, whose cost would be prohibitive. Rigorous functional qualification of the full system will of course still need to be carried out, to ensure adequate reliability for space deployment.
Although satellites can deliver virtually blanket coverage, and potentially also the high data rates demanded for 5G, they do have a disadvantage in terms of latency. Due to the long distances involved, latency for an LEO is typically 30ms – better than the 40ms that is typically achieved by 4G LTE, but poor compared with the 5G target of less than 1ms.