16
Satellite Networks
16.1 Potential Convergence
Getting coverage to deep rural areas or out at sea or on deserted mountain tops or in the middle of the desert where no one lives can be technically challenging and economically problematic. With the possible exception of coverage in the middle of the ocean, cellular networks can provide coverage more or less anywhere, but the cost can become prohibitive relative to income.
Cellular networks are generally speaking optimised for capacity and increasingly now high per user peak data rates. The wider channel spacing and wider operational bandwidths needed generally reduce the coverage available in any particular band.
This chapter looks at low-earth orbit and geostationary satellite systems but we start with two-way radio systems and specialist user requirements. As with terrestrial cellular networks, satellite networks and two-way radio networks are increasingly doing a lot more than just supporting voice traffic and are becoming increasingly information centric and, in the jargon of the sector, ‘mission critical’.
Table 16.1 Specialist user needs
| Wide-area coverage | Better than cellular particularly in rural areas and/or within buildings in urban environments |
| ‘All informed’ user capability | The ability to hear other users in an ‘open’ channel |
| ‘Instant access’ onto available channels | Call setup time has to be less than 250 milliseconds |
| Multigroup announcements | |
| Wide-area broadcast messages | |
| Dynamically changeable priority ... |
