A cost-effective design is proposed for circuit-switching multistage interconnection networks (CSMINs). Increase of the network bandwidth and reduction of the network size (and thus low costs) are accomplished by network overlapping and memory interleaving (NOMI), instead of by increasing the number of switches or adding buffers. NOMI and its control principle are described on the basis of the structure and interconnection functions of CSMINs. Detailed accounts of both the network design and the drastic reduction in hardware costs are given. The impact of NOMI on system performance is also analyzed.