1. Introduction
With the fast development of wireless applications and networks, wireless services that delivers common contents to multiple users have becoming increasingly popular. Examples include video streaming, information or media sharing, and mobile application downloads. Wireless multicasting is the underlying technology to enable these services. With massive MIMO emerged as a promising key technology for the 5th generation wireless systems [1], [2], multicast beamforming for downlink content delivery in a massive MIMO cellular system is expected to a promising transmission techniques.