dlink dir-615 is one of the worst ap router that existed in this world. There is no need to argue it's usage and so on. This piece of crap should be collected and thrown into the volcano.

Now, on some of the recommendations on replacement. I would not suggest any typical user to user mikrotik because it is a powerful device that have so many features, a normal user will be lost in it's infinite config options. Mikrotik is more for enthusiasts and IT geeks. For normal typical users, go for brands like asus or netgear. Some suggested tp-link as it is cheaper but quality is not as good as others. But it is still 100 times better than stupid dir-615.