The merits of multi-hop communication in deep space

The physics of communication give an advantage to multi-hop systems, because the ratio of power received to power transmitted on a telecommunications link of length S increases by a factor of n/sup 2/ if the link is divided in to n equal hops of length S/n. If terminal characteristics are unchanged, the cost of a multi-hop system is higher than for a single hop, but the efficiency-to-cost ratio is n times better. Multi-hop systems can be scaled easily, have capacity that scales proportional to the square of the investment, are robust, and can provide multiple orders-of-magnitude increase of capacity in deep space using presently available technology. This remains true when noise introduced on each segment is taken into account, if modern error-control coding techniques are applied. Candidate mission designs for a multi-hop approach are discussed for high-capacity Earth-Mars and interstellar communication systems.