This paper assumes a practical channel model, called a cascaded Rayleigh fading channel, for a noncooperative distributed mobile relay network, which consists of one mobile source and one mobile destination, and multiple mobile amplify-and-forward (AF) relays. Then, an optimum AF relay amplifying vector (or matrix) is analytically designed using the minimum mean square error (MMSE) criteria and uses it for an efficient mobile relay selection. Power is intentionally not constrained. Instead, this paper presents a scaling factor scheme to meet a target signal-to-noise ratio (SNRTGT) at the destination. This SNRTGT strategy can implicitly embrace the power constraint problems and be a more practical implementation.