CA : Carrier Aggregation

http://www.3gpp.org/technologies/keywords-acronyms/101-carrier-aggregation-explained
https://www.qualcomm.com/invention/technologies/lte/lte-carrier-aggregation
http://www.sogi.com.tw/mobile/articles/6232223-%E4%BB%80%E9%BA%BC%E6%98%AFCA%EF%BC%9FNote+4%EF%BC%8B%E8%BC%89%E6%B3%A2%E8%81%9A%E5%90%88%E5%AF%A6%E6%B8%AC%EF%BC%81%E7%B6%B2%E9%80%9F%E5%86%8D%E5%8D%87%E7%B4%9A