With the rapid increase of applications in 5G and Internet of Things, mobile edge computing (MEC) has been proposed to reduce the burden of central cloud and decrease the users request delay by deploying edge servers and edge services close to users. Due to resources constraint of edge servers and disadvantage of standalone placement optimization of edge servers or edge services, the discussion focusing on the combining optimization of server placement and service placement has engendered. At present, the placement combination is studied with strict assumption constrains, such as homogeneous service and server with unlimited resources, which are not suitable for the reality scenarios. This paper proposes Placement Combination between Heterogeneous Services and heterogeneous capacitated Servers (PCHSS). PCHSS aims to minimize the delay in computation and transmission as well as to balance resources in edge servers. Because the placement combination optimization is a NP-hard problem, we propose two solution algorithms named FHPC and IUPC. Both algorithms have a two-layer iterative optimization structure with different convergence time and result performances. FHPC can converge to a good result quickly, and IUPC can achieve better results with a relatively higher computational complexity. Then we prove that both algorithms can converge in polynomial time. Extensive simulations demonstrate the significant effectiveness of the placement combination, and our algorithms can reduce the user request delay by up to 51% compared with baseline algorithms.
