Analysis and applications of r-for N protection system

The availability of a single member of a group of N functionally identical systems that work in parallel and share a pool of r backup systems is analyzed. These N+r systems, each with failure rate λ, are repairable, and there are m repairers available, each operating at rate μ. A Markov model is used to derive formulas for availability, mean time to failure, and mean time to repair for such a system. The analysis results indicate that by increasing r and decreasing ρ, the ratio of failure rate to repair rate, overall network availability is improved. It is shown that, for certain ρ´s, some r:N pooled protections can significantly outperform 1:1 or 1:2 dedicated protection in terms of availability. The application of r :N protection to high-capacity transport systems is discussed, and it is indicated that multiwavelength systems may use additional wavelengths for protection. It is concluded that r: N protection can potentially provide both improved availability and significant cost advantages to the high-capacity transport systems