Combinatorial approximation algorithms for buy-at-bulk connected facility location problems

In this paper, we introduce and analyze two fundamental versions of these problems. In the Buy-at-Bulk version of the problem, each access cable type has a fixed setup cost and a fixed capacity, whereas in the Deep-Discount problem version, each cable type has unlimited capacity but a traffic-dependent variable cost in addition to its fixed setup cost. We derive the first constant-factor approximation algorithms for these problems, using different algorithmic and analytical techniques.