Fault tolerant on board networks with priorities

International audienceWe consider on-board networks in satellites interconnecting entering signals (inputs) to amplifiers (outputs). The connections are made via expensive switches, each of which has four available links. The paths connecting inputs to outputs should be link-disjoint. Some of the input signals, called priorities, must be connected to the amplifiers which provide the best quality of service (that is to some specific outputs). In practice, amplifiers are prone to fail and the faults cannot be repaired. Therefore, extra outputs have to be built into the network to ensure that every input can be routed to operational outputs. Given three integers, $n$, $p$, and $f$, we would like to design a low cost network (where the network cost is proportional to the total number of switches) such that it is possible to route all $n$ inputs to $n$ operational amplifiers, and to route the $p$ priorities to the $p$ best quality amplifiers for any set of $f$ faulty and $p$ best-quality amplifiers. Let $R(n,p,f)$ be the minimum number of switches of such a network. We prove here that $R(n,p,f)\leq \frac{n+f}{2} \lceil \log_2 p \rceil +\frac{5}{2}(n-p) +g(f)$ with $g$ a function depending only on $f$. We then compute $R(n,p,f)$ exactly for a few small values of $p$ and $f$

Design of Fault-Tolerant Networks for Satellites (TWTA) Redundancy

This article deals with the design of networks to be placed on satellites. These networks should connect inputs (corresponding to signals arriving at the satellite) to outputs (corresponding to ampliers), even in case of failures of ampliers. The networks are made of links and expensive switches, hence we want to minimize the number of switches subject to the following conditions: each input and each output is connected to exactly one switch; each switch is adjacent to exactly four links; there are n inputs and n+k outputs; among the n+k outputs, k can fail permanently; and nally all the input signals should be sent to valid ampliers, i.e., outputs, via disjoint paths. So, the aim is to design networks having as few switches as possible and satisfying the following property: there exist n edge-disjoint paths from the n inputs to any set of n outputs chosen from the n + k total number of outputs. We call such networks valid k- fault tolerant networks. Let N (n; k) denote the minimum number of switches of a valid network with n inputs, n + k outputs and k output failures. In thi

Design of fault-tolerant networks for satellites (TWTA redundancy)

International audienc