There is a separate attribute, which enables you to map the desktop and mobile URLs: rel=”alternate”. You can either implement that attribute on the desktop page, or specify it on the XML Sitemap. However, make sure that you use the canonical version of the mobile URL, because including the URL in the browser address bar could add annoying optional parameters.
Sometimes redirects are unavoidable, but always make sure you redirect to the target page and not to the homepage. This will only limit the usability of the mobile site, which could lead visitors to bounce off. So stay away from redirect loops, because it takes around 0.6 seconds to request a page for a mobile device – this means another 0.6 seconds for each redirect.
This happens, when you have separate URLs for your desktop and mobile site. If your desktop page redirects mobile users to an irrelevant page on the mobile site, then you can call it a faulty redirect – eg. all your pages on the desktop site redirects falsely to the mobile site. These redirects will just hinder the usability for mobile users, which could lead to an increase of the bounce rate.
There are three different possibilities; either you keep the URL the same for the mobile and desktop; or different URLs for both. If you use the same URL for your mobile, you can implement the responsive design or the dynamic serving. The former basically serves the same page with the same content, but changes the layout accordingly to the screen size or device. Although dynamic serving uses one URL as well, the page can show completely different content according to the device. The last possibility is implementing mobile URLs, typically at a ‘m.’ domain. Read more about it here.