Consistent Global navigation across separate host named site collection for SharePoint 2013?

Hi All,

Here i am looking for some suggestion on SharePoint 2013 architectural design. i am planning to have Consistent Global navigation across different host named site collection. Lets say i will have Landing page and in there will be Home Tab, About us, Departments and Projects. For Departments tab, there will be drop-down for all departments (like HR, Finance and Marketing) and each department will have own host named site collection. so what is the best way to achieve the consistent global navigation across separate HNSC?

Thanks in advanced!