In any radio environment, there can be a number of factors present that will affect the overall signal quality. Items such as walls can reduce the signal indoors. Furthermore, the signal will fade as it travels further from the access point. Also, higher frequencies equate to higher path losses. For example 802.11a, which operates at 5 GHz will have a shorter range than 802.11b or g based products, which operate at 2.4 GHz. All of these effects comprise path loss. To account for path loss, a mechanism called rate fallback can be used. 802.11 stations can change their transmission speed when they sense changes in the RF environment. By lowering the speed, a station ensures that its message will still get across rather than getting dropped altogether. Once conditions improve, the data rate can be stepped up.