We consider a broker who has to place a large order which consumes a sizable
part of average daily trading volume. The broker's aim is thus to minimize
execution costs he incurs from the adverse impact of his trades on market
prices. By contrast to the previous literature, see, e.g., Obizhaeva and Wang
(2005), Predoiu, Shaikhet, and Shreve (2011), we allow the liquidity parameters
of market depth and resilience to vary deterministically over the course of the
trading period. The resulting singular optimal control problem is shown to be
tractable by methods from convex analysis and, under minimal assumptions, we
construct an explicit solution to the scheduling problem in terms of some
concave envelope of the resilience adjusted market depth