Unlicensed spectrum utilization in LTE networks has been under extensive discussions and standardization attempts for its potential to handle the rapidly increasing data traffic. Various technologies for the utilization of unlicensed spectrum in LTE networks have emerged recently, and each of them has their potentials in certain aspects and critical issues to be solved. In this article, we provide a survey on the potential enabling solutions for the unlicensed spectrum utilization in LTE networks, including the direct usage of LTE infrastructures and protocols in unlicensed spectrum and LTE-WLAN integration. We highlight the differences between different LTE technologies in unlicensed spectrum and open up potential research directions related to the usage of unlicensed bands in cellular networks.