  A delay-optimal caching problem (DOCP) in deviceto- device (D2D) networks
with moblity is modelled. The problem arises in the context of achieving
offloading using device caching, and the offloading effect is represented by
the expected network load ratio (NLR) which is the percentage of data that has
to be downloaded from the network. Compared with the related studies, this work
considers minimizing delay with NLR guarantee in mobility scenarios. A lower
bound of global optimum is derived, thus enabling performance benchmarking of
any sub-optimal algorithm. For problem-solving, an effective search algorithm
(ESA) is proposed based on the bound. Simulations are conducted to evaluate the
effectiveness of the ESA algorithm.
