In Japan, 4K/8K satellite broadcasting is scheduled to start in December 2018 and ultra high definition video service is expected to be spreading rapidly. In the future, 4K/8K multichannel broadcasting by cable television operators is also expected. The challenge in introducing this service is that the transmission method in older apartment buildings is not fiber to the home (FTTH). Therefore, we investigated 4K/8K multichannel IP multicast distribution using data over cable service interface specifications (DOCSIS), which utilizes in-building coaxial cable networks. We have proposed a transmission method which can distribute with a smaller number of QAM signals than conventional methods.